Dissertations / Theses on the topic 'Cooling pipes'

Current water-cooling technology used in the metallurgical industry poses a major safety concern. In addition, these systems are expensive to operate and result in significant energy losses.
The purpose of the research presented in this thesis was to develop a viable cooling system based on novel heat pipe technology which addresses these problems. This technology employs boiling as the means to store and transfer heat energy. The large heat extraction capacity of the device is owed to two design features: firstly, a separate return line that generates a column of liquid working fluid which drains into the evaporator by gravity, and secondly, a helical flow modifier in the evaporator that stabilizes annular two-phase flow.
A full-scale copper tapblock and launder were designed with water-based heat pipe cooling systems. These systems were successfully tested under industrial heat loading conditions, using a gas burner to simulate the heat loads.
The tapblock cooling system was able to dissipate 142 kW per heat pipe, at heat fluxes as high as 2.4 MW/m2. These values are the largest to date using the novel water-based heat pipe technology. The launder system was the first to incorporate horizontal heat pipes, as well as have multiple evaporators feeding a single condenser.
The cooling systems used in both experiments were fundamentally safer than watercooling systems, being operated at low pressures and with only several kilograms of water exposed to the heat source. The cooling water requirements of these systems represent a reduction of 80-95% compared to conventional water-cooling, with increased potential for energy recovery.
During the testing, dry-out and film boiling were identified as the main limitations. It was found that film boiling occurs when the flow in the evaporator is not great enough to generate a helical motion. The dry-out limitation was achieved when the velocity of the flow within the evaporator was too great, causing a large pressure gradient that opposes the gravity head of the return line.
Both of these limitations are related to the configuration of the evaporator, i.e. the return line and the flow modifier. A methodology was developed to model the evaporator numerically using computational fluid dynamics. This methodology can be used to understand how the design parameters of the evaporator affect the flow patterns during operation.

Distributionsförluster är en viktig faktor i fjärrenergisystem. Genom att optimera förluster i sådana system, kan både ekonomiska och miljömässiga aspekter uppfyllas. Tyvärr finns det ringa information om rörförluster i fjärrkylasystem. Föreliggande studie fokuserar på förluster i ett fjärrkylanät genom att både använda ett R-nätverk och FEM simuleringsmodeller. Ett R-nätverksmodell bestående av termiska konduktanser har utvecklats genom analytiska ekvationer och simuleringar med FEM har utfört för validering av modellen. Därefter har ett fjärrkylanätverk som konstrueras i Gävle, analyserats. Undersökningen omfattar 15 olika rördiametrar i tre utföranden (dubbelrör med två symmetriska och en osymmetrisk värmeisolering) och i tre förläggningsdjup (0,8; 2 och 4 meter) för en säsong om 7 månader (April t o m Oktober). Särskilt utreds ökningen av temperaturen hos framledningsmediet, där matningsrören förlagts i en å mitt i staden om en sträcka av 1 km. Den maximala förlusten under säsongen, bland alla rörkonfigurationer, motsvarar 2 % av den totala levererade energin. Slutligen konstateras att kombinationen av isolerad framledningsrör och oisolerade returrör verkar som en gångbar investering, ekonomiskt och tekniskt, men kan inte användas i hela nätet eftersom stora delar har redan byggts med oisolerade plaströr. R-nätverksmodellen, som visades vara effektiv och pålitlig i undersökningen, kan som beräkningsverktyg, framförallt för dimensionering och för att uppskatta energiförluster.
Distribution losses are a very important factor in district energy systems. By optimizing the losses in such a system, both economical and environmental aspects can be fulfilled. Unfortunately, there is few information regarding losses for district cooling systems. This study focuses on losses in district cooling networks by using both R-network and FEM simulation models. A R-network model composed of thermal conductances has been developed through analytical equations and simulations have been performed for validation. Afterwards, an in-progress construction project of a district cooling network from the city of Gävle, Sweden, is analyzed. The assessment consists of 15 pipe diameters in three configurations (two symmetric cases and one asymmetric), at three ground laying depths (0.8, 2 and 4 meters) for a duration of 7 months (April to October). A particular case in which the main distribution pipes from and to the plant are submerged in the city’s river for a distance of 1 km is investigated in order to estimate the temperature increase of the supply water. A maximum cooling loss below 2% of the total delivered energy during the season for any network configuration resulted from the calculation. Finally, the mixed pipes array seems to be a feasible investment both economically and technically but it cannot be used for the entire network spread since a part of the network has been already built with the non-insulated plastic pipes. The R-network model proved to be effective and reliable in the analysis which provides confidence that it can serve as a solid foundation for a calculation tool - primarily for design purposes and also for estimating energy loss.

In modern aircraft, one of the most difficult issues has been how to provide avionics with adequate cooling. Future versions of the fighter aircraft JAS 39 Gripen is equipped with new applications that have increased heat loads. In previous versions of the JAS 39 Gripen avionics was cooled by zero degree air and fuel, but in the next version a liquid loop will be installed to cool the new radar.The fluid in the liquid loop is cooled to proper temperature by pressurized bleed air from the engine which is cooled by ram air. The air to cool the avionics is produced the same way and this is a very expensive process for the airplane which lowers its performance. It is important to minimize the production of cooling air and therefore three new adjustable valves that provide various components of cooling air are installed in the next version of the JAS 39 Gripen. The cooled and pressure controlled air from the engine is distributed between different avionic shelves, each containing a set of components. Depending on the type of tasks performed and current flight mode of the aircraft the requirement of functions which should be active varies and therefore also the cooling demand to avionics. The first part of this thesis studies the overall priority of how the engine bleed shall be used. This part of the thesis results in a decision basis for the distribution of cooling air to be regulated in the absence of full cooling capacity. The amount of cooling which must be distributed to the radar is proportional to its developed power which varies widely depending on the radar’s operational mode. Since the pump which determines the liquid flow velocity operates at a constant speed is the regulation of cooling to the radar is controlled by varying the bleed air flow into the heat exchanger which cools the fluid and thus the temperature of the fluid has when it reaches the radar. This part of the thesis creates a control algorithm for controlling the airflow into the heat exchanger. The regulation keeps the fluid inlet temperature to the radar within the range of +25 ± 5 ˚ C and the gradient of the temperature less than 0.5° C per second. The PI-controller with the feed-forward filter succeeded in controlling the temperature of the liquid as it reached the radar within +25 ± 1° C, the temperature gradient requirement, 0.5° C per second, was also passed in all flight cases which were used to evaluate the controller. The PI-controller with feed-forward has a low convergence time and no static error. It also performs well when the measurement signals contain a lot of noise because of the controllers integrated low pass filter.   The three new adjustable valves saves 12 to 97 g/s of cooling air for the different valve positions studied in this thesis, this corresponds to 9 - 70% of the total amount of controllable air to the avionics. Since the production of cooling air is a costly process for the aircraft, the use of all 3 valves is recommended.

Orientador: Tomaz Manubu Hashimoto
Banca: Marcelo dos Santos Pereira
Banca: Cristina de Carvalho Ares Elisei
Resumo: Com os novos desafios impostos pelas condições cada vez mais severas dos poços de petróleo offshore a necessidade de materiais mais modernos e com melhores propriedades mecânicas tem sido um desafio constante. Neste trabalho foi realizada a caracterização mecânica de tubos fabricados a partir de chapas de aço laminadas a quente, seguido de resfriamento acelerado. Os valores reportados são resultados de testes de laboratório aplicados em corpos de prova retirados do metal de base, de solda e da zona termicamente afetada. A utilização destes aços na fabricação de tubos soldados por processo arco-submerso em dois passes, utilizando arcos múltiplos, tem apresentado resultados de tenacidades confiáveis e superiores aos obtidos a partir de chapas laminadas pelo processo de laminação controlada sem resfriamento acelerado, principalmente em espessuras de 16 mm e superiores. Os requisitos do teste de tenacidade especificados pela norma DNV-OS -F101 aplicados em tubos fabricados de acordo com a norma API 5L, são considerados críticos. A criticidade é função dos valores mínimos a serem obtidos e também da freqüência estabelecida para ser aplicada em cada corrida de aço utilizada na produção de cada item de fabricação. Com isso nota-se uma enorme vantagem do uso dos aços com o processo de resfriamento acelerado, visto que os mesmos tiveram uma melhor homogeneidade nos resultados de limite de escoamento, com um ganho significativo no alongamento e apenas uma pequena redução no limite de resistência. O fato de usarem menores teores de carbono, também favoreceu muito a tenacidade no metal de base e ao longo da ZTA, tendo diferenças extremamente significativas de ganho no teste de impacto e CTOD
Abstract: The main of this work is the mechanical properties characterization of pipes made from steel plates produced using hot rolling with accelerated cooling. The values reported are laboratory tests results, applied on samples taken from the base metal, weld and heat affected zone. The use of these steel plates in the manufacture of pipes by submerged arc welding process using multiple arcs has shown toughness and elongation results superior to those obtained by using hot rolled steel plates without accelerated cooling, particularly in thicknesses of 16 mm and higher. The toughness test requirements specified by DNV-OS-F101 applied for pipes manufactured aiming offshore application are considered critical. The criticality is function of the minimum values required set the sampling frequency to be applied in every steel heat used in the production of each product. Because of this the use of accelerated cooling process shows a significant advantage, since it provides a better homogeneity in yield strength results, with a significant gain in elongation and only a small reduction in tensile strength. The use of smaller amounts of carbon also greatly fostered toughness in base metal and along HAZ, with significant improvement in the impact test and CTOD. Results due to these enhanced properties the use of steels with accelerated cooling technology is essential in order to face technological challenges imposed by new requirements of submarines pipelines
Mestre

Designing turbines for either aerospace or power production is a daunting task for any heat transfer scientist or engineer. Turbine designers are continuously pursuing better ways to convert the stored chemical energy in the fuel into useful work with maximum efficiency. Based on thermodynamic principles, one way to improve thermal efficiency is to increase the turbine inlet pressure and temperature. Generally, the inlet temperature may exceed the capabilities of standard materials for safe and long-life operation of the turbine. Next generation propulsion systems, whether for new supersonic transport or for improving existing aviation transport, will require more aggressive cooling system for many hot-gas-path components of the turbine. Heat pipe technology offers a possible cooling technique for the structures exposed to the high heat fluxes. Hence, the objective of this dissertation is to develop new radially rotating heat pipe systems that integrate multiple rotating miniature heat pipes with a common reservoir for a more effective and practical solution to turbine or compressor cooling. In this dissertation, two radially rotating miniature heat pipes and two sector heat pipes are analyzed and studied by utilizing suitable fluid flow and heat transfer modeling along with experimental tests. Analytical solutions for the film thickness and the lengthwise vapor temperature distribution for a single heat pipe are derived. Experimental tests on single radially rotating miniature heat pipes and sector heat pipes are undertaken with different important parameters and the manner in which these parameters affect heat pipe operation. Analytical and experimental studies have proven that the radially rotating miniature heat pipes have an incredibly high effective thermal conductance and an enormous heat transfer capability. Concurrently, the heat pipe has an uncomplicated structure and relatively low manufacturing costs. The heat pipe can also resist strong vibrations and is well suited for a high temperature environment. Hence, the heat pipes with a common reservoir make incorporation of heat pipes into turbo-machinery much more feasible and cost effective.

Heat pipe is a passive two phase device capable of transferring large rates of heat with a minimal temperature drop. It is a sealed tube with a wick structure lined in it and with a working fluid inside the tube. It consists of three parts: an evaporator, a condenser and an adiabatic section. The heat pipes are widely used in electronics cooling and spacecraft applications. Although they can transfer large rate of heat in a short range, they have operating limits, namely: the capillary limit, the viscous limit, the entrainment limit, the sonic limit and the boiling limit. These limits determine the heat transfer capacity of the heat pipe. The properties of the working fluid, the structure of the wick, the orientation of the pipe, the length and the diameter of the tube etc. are the parameters that affect the limits. In this study, an analytical 1-D heat pipe model is formed and a computer code is prepared in order to analyze the effects of the parameters on the heat transfer capacity of a heat pipe. Water, Ammonia and Mercury are investigated as working fluids for different operating temperature ranges. The software is tested for a typical application for each working fluid.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Com os novos desafios impostos pelas condições cada vez mais severas dos poços de petróleo offshore a necessidade de materiais mais modernos e com melhores propriedades mecânicas tem sido um desafio constante. Neste trabalho foi realizada a caracterização mecânica de tubos fabricados a partir de chapas de aço laminadas a quente, seguido de resfriamento acelerado. Os valores reportados são resultados de testes de laboratório aplicados em corpos de prova retirados do metal de base, de solda e da zona termicamente afetada. A utilização destes aços na fabricação de tubos soldados por processo arco-submerso em dois passes, utilizando arcos múltiplos, tem apresentado resultados de tenacidades confiáveis e superiores aos obtidos a partir de chapas laminadas pelo processo de laminação controlada sem resfriamento acelerado, principalmente em espessuras de 16 mm e superiores. Os requisitos do teste de tenacidade especificados pela norma DNV-OS –F101 aplicados em tubos fabricados de acordo com a norma API 5L, são considerados críticos. A criticidade é função dos valores mínimos a serem obtidos e também da freqüência estabelecida para ser aplicada em cada corrida de aço utilizada na produção de cada item de fabricação. Com isso nota-se uma enorme vantagem do uso dos aços com o processo de resfriamento acelerado, visto que os mesmos tiveram uma melhor homogeneidade nos resultados de limite de escoamento, com um ganho significativo no alongamento e apenas uma pequena redução no limite de resistência. O fato de usarem menores teores de carbono, também favoreceu muito a tenacidade no metal de base e ao longo da ZTA, tendo diferenças extremamente significativas de ganho no teste de impacto e CTOD
The main of this work is the mechanical properties characterization of pipes made from steel plates produced using hot rolling with accelerated cooling. The values reported are laboratory tests results, applied on samples taken from the base metal, weld and heat affected zone. The use of these steel plates in the manufacture of pipes by submerged arc welding process using multiple arcs has shown toughness and elongation results superior to those obtained by using hot rolled steel plates without accelerated cooling, particularly in thicknesses of 16 mm and higher. The toughness test requirements specified by DNV-OS-F101 applied for pipes manufactured aiming offshore application are considered critical. The criticality is function of the minimum values required set the sampling frequency to be applied in every steel heat used in the production of each product. Because of this the use of accelerated cooling process shows a significant advantage, since it provides a better homogeneity in yield strength results, with a significant gain in elongation and only a small reduction in tensile strength. The use of smaller amounts of carbon also greatly fostered toughness in base metal and along HAZ, with significant improvement in the impact test and CTOD. Results due to these enhanced properties the use of steels with accelerated cooling technology is essential in order to face technological challenges imposed by new requirements of submarines pipelines

O uso do solo como massa inercial para condicionamento térmico de edificações por contato direto é uma prática antiga, porém, seu uso como trocador de calor através de dutos enterrados, para ventilação natural de edificações é recente. A prática consiste em enterrar dutos a profundidades entre 0,5m e 1,5m – com extensões e diâmetros variáveis – por onde o ar circula do exterior para o interior dos ambientes através da ação do vento externo e da convecção natural. Durante o trajeto, o ar troca calor com o solo e ingressa no ambiente a temperaturas mais amenas. Embora seja um sistema já empregado na arquitetura bioclimática, existem poucos estudos conclusivos sobre a sua real eficácia. Dessa forma, o objetivo do trabalho é investigar o comportamento higrotérmico de uma edificação construída no sul do Brasil com o sistema e compreender a atuação dos fatores climáticos responsáveis pelo deslocamento de ar no seu interior. O estudo foi realizado através do monitoramento do Protótipo Ventura, localizado em Viamão (Brasil – 30º01'59"S, 51º13'48"W) no período de verão. No deslocamento de ar, foi estudada a influência do vento e da diferença de temperatura nos 2 diâmetros, nas 2 inclinações e nas 2 orientações dos dutos existentes, bem como a influência da chaminé solar. O desempenho higrotérmico foi avaliado comparando o ar na sala ventilada com uma sala de referência (de mesmas dimensões, porém de orientação distinta) e com o exterior. Os resultados demonstram que o solo de Viamão é eficiente para o condicionamento térmico da edificação, pois a pequenas profundidades, ele apresenta uma temperatura mais estável que o ar, próxima à média anual de temperatura do ar local (18ºC). Dessa forma, ao passar pelo duto, o ar externo é aquecido nos períodos frios e refrigerado nos períodos quentes, mantendo o ar interno próximo da zona de conforto. Também foi possível observar que o principal fator responsável pelo deslocamento de ar observado é o vento externo, porém as diferenças de temperatura entre as extremidades dos tubos, bem como entre o interior e exterior da edificação, não podem ser desprezadas, pois geram velocidades de mesma magnitude que o primeiro. Por fim, conclui-se que a ventilação da sala reduziu seu retardo térmico, porém não prejudicou o seu conforto térmico, apresentando inclusive uma redução de sua umidade interna.
The use of the ground as an inertial mass for thermal conditioning of buildings, such as the Italians cellars, is an old practice. However, its use as a heat exchanger with buried pipes for natural indoor ventilation is quite recent. The system uses pipes with variable length and diameter buried at a depth between 0.5m and 1.5m. The air flows trough the pipes from the outside to the inside by convection or wind effects. Although it’s already a bioclimatic architecture system, there are few conclusive studies about its real effectiveness. The objective of this study is to investigate the benefits of natural ventilation through buried pipes in a building located in the south of Brazil. A prototype building and a buried pipe system have been built and measured during a period in the summer of 2005-2006, in Viamão (30º 01'59"S, 51º13'48"W). The influence of the pipes diameter, inclination and orientation has been studied as well as the thermal comfort indoors. The system is efficient for thermal building conditioning and air renovation. At small depths, the ground presents a more steady temperature than the air, close to the annual average temperature (18ºC), cooling the air in hot days, warming it in cold nights – a similar effect is expected on a yearly period. The main factor responsible to the air flow is the outside wind, but the air temperature differences between the pipes, the room and the solar chimney edges are very relevant. The room ventilation reduces its thermal delay without interfering with its thermal performance, and also shows a decrease in its internal humidity.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: A reactor cavity cooling system (RCCS) is used in the PBMR to protect the concrete citadel surrounding the reactor from direct nuclear radiation impingement and heat. The speci ed maximum operating temperature of the concrete structure is 65 ±C for normal operating conditions and 125 ±C for emergency shut-down conditions. A conceptual design of an entirely passive RCCS suitable for the PBMR was done by using closed loop thermosyphon heat pipes (CLTHPs) to remove heat from a radiation heat shield over a horizontal distance to an annular cooling dam placed around the PBMR. The radiation shield is placed in the air space between the Reactor Pressure Vessel (RPV) and the concrete citadel, 180 mm from the concrete citadel. A theoretical heat transfer model of the RCCS was created. The theoretical model was used to develop a computer program to simulate the transient RCCS response during normal reactor operation, when the RCCS must remove the excess generated heat from the reactor cavity and during emergency shut-down conditions, when the RCCS must remove the decay heat from the reactor cavity. The main purpose of the theoretical model is to predict the surface temperature of the concrete citadel for di erent heat generation modes in the reactor core and ambient conditions. The theoretical model assumes a 1D geometry of the RCCS. Heat transfer by both radiation and convection from the RPV to the radiation heat shield (HS) is calculated. The heat shield is modelled as a n. The n e ciency was determined with the experimental work. Conduction through the n is considered in the horizontal direction only. The concrete structure surface is heated by radiation from the outer surface of the heat shield as well as by convection heat transfer from the air between the heat shield and the concrete structure surface. The modelling of the natural convection closed loop thermosyphon heat pipes in the RCCS is done by using the Boussinesq approximation and the homogeneous ow model. An experiment was built to verify the theoretical model. The experiment is a full scale model of the PBMR in the horizontal, or main heat transfer, direction, but is only a 2 m high section. The experiments showed that the convection heat transfer between the RPV and the HS cannot be modelled with simple natural convection theory. A Nusselt number correlation developed especially for natural convection in enclosed rectangles found in literature was used to model the convection heat transfer. The Nusselt number was approximately 3 times higher than that which classic convection theory suggested. An optimisation procedure was developed where 121 di erent combinations of n sizes and heat pipe sizes could be used to construct a RCCS once a cooling dam size was chosen. The purpose of the optimisation was to nd the RCCS with the lowest total mass. A cooling dam with a diameter of 50 m was chosen. The optimal RCCS radiation heat shield that operates with the working uid only in single phase has 243 closed loop thermosyphon heat pipes constructed from 62.72 mm ID pipes and 25 mm wide atbar ns. The total mass of the single phase RCCS is 225 tons. The maximum concrete structure temperature is 62.5 ±C under normal operating conditions, 65.8 ±C during a PLOFC emergency shut-down condition and 80.9 ±C during a DLOFC emergency shut-down condition. In the case where one CLTHP fails and the adjacent two must compensate for the loss of cooling capacity, the maximum concrete structure temperature for a DLOFC emergency shut-down will be 87.4 ±C. This is 37.6 ±C below the speci ed maximum temperature of 125 ±C. The RCCS design is further improved when boiling of the working uid is induced in the CLTHP. The optimal RCCS radiation heat shield that operates with the working uid in a liquid-vapour mixture, or two phase ow, has 338 closed loop thermosyphon heat pipes constructed from 38.1 mm ID pipes and 20 mm wide atbar ns. The total mass of the two phase RCCS is 198 tons, 27 tons less than the single phase RCCS. The maximum concrete structure temperature is 60 ±C under normal operating conditions, 2.5 ±C below that of the single phase RCCS. During a PLOFC emergency shut-down condition, the maximum concrete structure temperature is 62.3 ±C, 3.5 ±C below that of the single phase RCCS and still below the normal operating temperature of the single phase RCCS. By inducing two phase ow in the CLTHP, the maximum temperature of the working uid is xed equal to the saturation temperature of the working uid at the vacuum pressure. This property of water is used to limit the concrete structure temperature. This e ect is seen in the transient response of the RCCS where the concrete structure temperature increases until boiling of the working uid starts and then the concrete structure temperature becomes constant irrespective of the heat load on the RCCS. An increased heat load increases the quality of the working uid liquid-vapour mixture. Working uid qualities approaching unity causes numerical instabilities in the theoretical model. The theoretical model cannot capture the heat transfer to a control volume with a density lower than approximately 20 kg/m3. This limits the extent to which the two phase RCCS can be optimised. Recommendations are made relating to future work on how to improve the theoretical model in particular the convection modelling in the reactor cavities as well as the two phase ow of the working uid. Further recommendations are made on how to improve the basic design of the heat shield as well as the cooling section of the CLTHPs.
AFRIKAANSE OPSOMMING: 'n Reaktor lug spasie verkoelingstelsel (RLSVS) word in die PBMR gebruik om die beton wat die reaktor omring te beskerm teen direkte stralingskade en hitte. Die gespesi seerde maksimum temperatuur van die beton is 65 ±C onder normale bedryfstoestande en 125 ±C gedurende die noodtoestand afskakeling van die reaktor. 'n Konseptuele ontwerp van 'n geheel en al passiewe RLSVS geskik vir die PBMR is gedoen deur gebruik te maak van geslote lus termo-sifon (GLTSe) om hitte van die stralingskerm te verwyder oor a horisontale afstand na 'n ringvormige verkoelingsdam wat rondom die reaktor geposisioneer is. Die stralingskerm word in die lug spasie tussen die reaktor drukvat (RDV) en die beton geplaas, 180 mm vanaf die beton. 'n Teoretiese hitteoordrag model van die RLSVS was geskep. Die teoretiese model was gebruik vir die ontwikkeling van 'n rekenaar program wat die transiënte gedrag van die RLSVS sal simuleer gedurende normale bedryfstoestande, waar die oorskot gegenereerde hitte verwyder moet word vanuit die reaktor lug spasie, asook gedurende noodtoestand afskakeling van die reaktor, waar die afnemingshitte verwyder moet word. Die primêre doel van die teoretiese model is om the oppervlak temperatuur van die beton te voorspel onder verskillende bedryfstoestande asook verskillende omgewingstoestande. Die teoretiese model aanvaar 'n 1D geometrie van die RLSVS. Hitte oordrag d.m.v. straling asook konveksie vanaf die RDV na die stralingskerm word bereken. The stralingskerm word gemodelleer as 'n vin. Die vin doeltre endheid was bepaal met die eksperimente wat gedoen was. Hitte geleiding in die vin was slegs bereken in die horisontale rigting. Die beton word verhit deur straling vanaf die agterkant van die stralingskerm asook deur konveksie vanaf die lug tussen die stralingskerm en die beton. The modellering van die natuurlike konveksie GLTS hitte pype word gedoen deur om gebruik te maak van die Boussinesq benadering en die homogene vloei model. 'n Eksperiment was vervaardig om the teoretiese model te veri eer. Die eksperiment is 'n volskaal model van die PBMR in die horisontale, of hoof hitteoordrag, rigting, maar is net 'n 2 m hoë snit. Die eksperimente het gewys dat die konveksie hitte oordrag tussen die RDV en die stralingskerm nie met gewone konveksie teorie gemodelleer kan word nie. 'n Nusselt getal uitdrukking wat spesi ek ontwikkel is vir natuurlike konveksie in geslote, reghoekige luggapings wat in die literatuur gevind was, was gebruik om die konveksie hitteoordrag te modelleer. Die Nusselt getal was ongeveer 3 maal groter as wat klassieke konveksie teorie voorspel het. 'n Optimeringsprosedure was ontwikkel waar 121 verskillende kombinasies van vin breedtes en pyp groottes wat gebruik kan word om 'n RLSVS te vervaardig nadat 'n toepaslike verkoelingsdam diameter gekies is. Die doel van die optimering was om die RLSVS te ontwerp wat die laagste totale massa het. 'n Verkoelingsdam diameter van 50 m was gekies. Die optimale RLSVS stralingskerm, waarvan die vloeier slegs in die vloeistof fase bly, bestaan uit 243 GLTSe wat van 62.72 mm binne diameter pype vervaardig is met 25 mm breë vinne. The totale massa van die enkel fase RLSVS is 225 ton. Die maksimum beton temperatuur is 62.5 ±C vir normale bedryfstoestande, 65.8 ±C vir 'n PLOFC noodtoestand afskakeling en is 80.9 ±C vir 'n DLOFC noodtoestand afskakeling. In die geval waar een GLTS faal gedurende 'n DLOFC noodtoestand afskakeling en die twee naasgeleë GLTSe moet kompenseer vir die vermindering in verkoelings kapasiteit, is die maksimum beton temperatuur 87.4 ±C. Dit is 37.6 ±C laer as die gespesi seerde maksimum temperatuur van 125 ±C. Die RLSVS ontwerp kan verder verbeter word wanneer die vloeier in die GLTSe kook. Die optimale RLSVS stralingskerm met die vloeier wat kook, of in twee fase vloei is, bestaan uit 338 GLTSe wat van 38.1 mm binne diameter pype vervaardig is met 20 mm breë vinne. The totale massa van die twee fase vloei RLSVS is 198 ton, 27 ton ligter as die enkel fase RLSVS. Die maksimum beton temperatuur is 60 ±C vir normale bedryfstoestande, 2.5 ±C laer as die enkel fase RLSVS. Gedurende 'n PLOFC noodtoestand afskakeling is die maksimum beton temperatuur 62.3 ±C, 3.5 ±C laer as die enkel fase RLSVS en nogtans onder die maksimum beton temperatuur van die enkel fase RLSVS vir normale bedryfstoestande. Deur om koking te veroorsaak in die GLTS word die maksimum temperatuur van die vloeier vasgepen gelyk aan die versadigings temperatuur van die vloeier by die vakuüm druk. Hierdie einskap van water word gebruik om 'n limiet te sit op die maksimum temperatuur van die beton. Hierdie e ek kan gesien word in die transiënte gedrag van die RLSVS waar die beton temperatuur styg tot en met koking plaasvind en dan konstant raak ongeag van die hitte belasting op die RLSVS. 'n Toename in die hitte belasting veroorsaak net 'n toename in die kwaliteit van die vloeistof-gas mengsel. Mengsel kwaliteite van 1 nader veroorsaak numeriese onstabiliteite in die teoretiese model. The teoretiese model kan nie die hitteoordrag beskryf na 'n kontrole volume wat 'n digtheid het laer as ongeveer 20 kg/m3. Hierdie plaas 'n limiet op die optimering van die twee fase RLSVS. Aanbevelings was gemaak met betrekking tot toekomstige werk aangaande die verbetering van die teoretiese model met spesi eke klem op die modellering van konveksie in die reaktor asook die modellering van twee fase vloei. Verdere aanbevelings was gemaak aangaande die verbetering van die stralingskerm ontwerp asook die ontwerp van die verkoeling van die GLTSe.

Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: High temperature heat sources are becoming an ever-increasing imperative in the process industry for the production of plastics, ammonia and fertilisers, hydrogen, coal-toliquid fuel and process heat. Currently, high temperature reactor (HTR) technology is capable of producing helium temperatures in excess of 950°C; however, at these temperatures, tritium, which is a radioactive contaminant found in the helium coolant stream, is able to diffuse though the steel retaining wall of the helium-to-steam heat exchanger. To circumvent this radioactivity problem, regulations require an intermediate heat exchange loop between the helium and the process heat streams. In this paper, the use of a uniquely designed sodium-charged heat pipe heat exchanger is considered, and has the distinct advantage of having almost zero exergy loss as it eliminates the intermediate heat exchange circuit. In order to investigate this novel heat pipe heat exchanger concept, a special intermediate-temperature (± 240°C) experimental heat pipe heat exchanger (HPHE) was designed. This experimental HPHE uses Dowtherm A as working fluid and has two glass windows to enable visual observation of the boiling and condensation two-phase flow processes. A high temperature air-burner supply simulates the high temperature stream, and the cold stream is provided by water from a constant-heat supply tank. This experimental apparatus can be used to evaluate the validity of steady-state and start-up transient theoretical models that have been developed. This paper will highlight the special design aspects of this HPHE, the theoretical model and the solution algorithm described. Experimental results will be compared with the theoretically calculated results. The theoretical model will then be used to predict the performance of a high temperature (sodium working fluid at 850°C) HPHE will be undertaken and conclusions and recommendation made.
AFRIKAANSE OPSOMMING: Hoë temperatuur hitte bronne is besig om ‘n toenemende noodsaaklikheid te raak in die proses industrie vir die vervaardiging van plastieke, ammoniak, kunsmis, waterstof, steenkool-tot-vloeibare brandstof en proses hitte. Huidige hoë temperatuur reaktor tegnologie is in staat om helium te verhit tot temperature hoër as 950°C, maar by sulke hoë temperature is die vorming van tritium, wat ‘n radioaktiewe produk is, in die helium verkoeling stroom wat deur die reaktor vloei, ‘n probleem. Die tritium is in staat om deur die staal wand van ‘n enkel fase warmte uitruiler te diffundeer. Om hierdie radioaktiewe probleem te uitoorlê, stel huidige regulasies voor dat ‘n oorgangs hitte uitruil lus gebruik raak tussen die helium en proses strome van die reaktor stelsel. In hierdie tesis word ‘n unieke natrium gevulde hitte pyp warmte uitruiler nagevors, hierdie ontwerp het die voordeel dat dit geen “exergy” verlies het omdat dit nie ‘n oorgangs hitte uitruil lus benodig nie. Hierdie unieke konsep was nagevors deur ‘n spesiale oorgangs temperatuur (± 230°C) eksperimentiële hitte pyp warmte uitruiler te ontwerp. Hierdie eksperimentiële hitte pyp warmte uitruiler gebruik Dowtherm A as oordrags medium tussen die warm en koue strome en het twee glas venters waardeur die kook en kondensasie van die oorgangs medium dop gehou kan word. ‘n Hoë temperatuur verbrander simuleer die warm stroom deur die reaktor en die koue stroom word gesimuleer deur koue water. Die eksperimentiële opstelling sal gebruik word om die tyd afhangklike en tyd onafhangklike teoretiese wiskundige modele te valideer. Hierdie tesis sal die spesiale ontwerp aspekte van die hitte pyp warmte uitruiler, teoretiese modelle en oplos algoritme te bespreek. Eksperimentiele resultate sal met die teoretiese resultate vergelyk word en dan sal die teoretiese modelle gebruik word om ‘n natrium gevulde warmte uitruiler te simuleer. Gevolgtrekkings en aanbevelings sal in die lig van die resultate verskaf word.

Thesis (MEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: This project investigates aspects of a novel inherently safe nuclear power steam supply system as safety is of paramount importance. The system envisaged has unique features namely: a) a two-phase flow flash-tube type natural circulating primary loop (also the secondary radioactive particle containment); b) a twophase flow thermosyphon heat pipe type heat exchanger secondary loop is used to transfer heat from the primary loop to the steam generators, thereby physically separating the two flow streams from one another; c) a natural convection air cooled condenser for the removal of the reactor’s residual heat; d) a unique core using TRISO type fuel (acting as the primary radioactive particle containment) with life of at least 8.9 years; e) a steel containment vessel acting as a tertiary radioactive product containment; f) a concrete containing structure with air vents to allow air to pass over the main steel containment vessel for cooling purposes in the case of an emergency, and for the removal of parasitic heat during operation. In particular the primary and secondary loops of the proposed system are investigated. This is done by design, construction and testing of a small scale experimental set-up of the primary and secondary loops as well as the development of theoretical models for the two loops. A literature survey focusing on nuclear technology, thermosyphon loops, natural circulating loop instabilities, heat pipes, and two-phase flow modelling is presented to give a brief overview of the technologies as well as tools used in the work undertaken. Observations of the inside flow behaviour of the primary loop experimental set-up were made possible by windows providing many insights into the inner workings, such as plume formation and geysering. The transient response of the secondary heat pipe loop start-up is also investigated. A thermal resistance theoretical model was developed for the secondary loop using heat transfer formulae from theory as well as experimentally semiempirical correlated formula. Different states of operation of the secondary loop were observed during testing with the theoretical model of the condensing regime correlating well, two-phase regime correlating acceptably and liquid regime correlating poorly to experimental results and thus were modelled using an experimentally determined overall heat transfer coefficient. The secondary loop model of the liquid regime is coupled with the primary loop theoretical model to predict the system’s performance. A homogeneous, one-dimensional, simple theoretical model for the primary loop was derived and computer simulated. The results did not compare well with experimental results for single phase flow and failed to capture the onset of two-phase flow. The assumptions of one dimensional model with a unidirectional flow, a hydrostatic pressure problem, a constant volumetric flow rate and the inability of the implementation of the code to handle expansion are noted as some of the flaws in the theoretical model. The following recommendations are made: a more advanced design of the pressuriser should be incorporated into the experiment; the secondary loop’s theoretical model should be characterised under a broader set of operating conditions; the computer program can be used as the basis for further research and implementation of alternative solution algorithms and models.
AFRIKKANSE OPSOMMING: Hierdie projek ondersoek aspekte van ’n ongewone, essensieel veilige kernkrag stoomtoevoer-stelsel, omdat veiligheid van kardinale belang is. Die stelsel wat voorgestel is, het unieke eienskappe, naamlik: a) ’n twee-fasevloei flits-buistipe natuurlik sirkulerende primêre lus (wat ook die sekondêre inperking van radioaktiewe materiaal bevat); b) ’n twee-fasevloei termo-heweleffek sekondêre lus hitte-pyp hitte-uitruiler word gebruik om die hitte vanaf die primêre lus oor te dra na die stoomkragopwekkers en daardeur word die twee strome se vloei fisies geskei van mekaar; c) ’n natuurlike konveksie lugverkoelde kondensor word gebruik vir die verwydering van die reaktors se oortollige hitte; d) ’n unieke kern gebruik TRISO-tipe brandstof (wat as die primêre inperking van radioaktiewe materiaal optree) met ’n lewe van minstens 8.9 jaar; e) ’n inperkingshouer van staal wat optree as ’n tersiêre radioaktiewe produkhouer; f) ’n betonstruktuur met lugventilasie om toe te laat dat lug oor die hoof staalhouer vloei vir verkoeling in ’n noodgeval, en vir die verwydering van parasitiese hitte tydens werking. Hoofsaaklik word die primêre en sekondêre lusse van die voorgestelde stelsel ondersoek. Dit word gedoen deur die ontwerp, konstruksie en die toets van ’n eksperimentele opstelling van die primêre en sekondêre lusse op klein skaal, sowel as die ontwikkeling van teoretiese modelle vir die twee lusse. ’n Literatuurstudie wat fokus op kerntegnologie, termo-heweleffeklusse, natuurlik sirkulerende lus instabiliteit, hitte-pype, en twee-fase vloeimodellering word aangebied om ’n kort oorsig te gee van die tegnologie, sowel as gereedskap gebruik in die werk wat onderneem is. Om die interne vloeigedrag van die primêre lus se eksperimentele opstelling waar te neem, word daar gebruik gemaak van vensters wat dien as ’n manier om die innerlike werking van die proses soos pluimvorming en die kook van die water in die warmwaterkolom te toon. Die oorgangsreaksie van die sekondêre hittepyplus aanvangs is ook ondersoek. ’n Teoretiese termiese weerstandmodel is ontwikkel vir die sekondêre lus met behulp van hitte-oordragformules waarvoor hitte-oordragteorie gebruik is, wat met eksperimentele semi-empiriese formules gekorreleer is. Verskillende toestande van die sekondêre lus se werking is waargeneem gedurende die toetse. Die teoretiese model het goed met die kondensasiestaat gekorreleer, terwyl by die twee-fasewerkswyse aanvaarbare korrellasies aangetref is en die uiteindelike vloeitoestand swakker gekorrelleer het met eksperimentele resultate en dus gemodelleer is met behulp van die NTU-effektiwiteitsmetode. Die sekondêre lusmodel van die vloeistoftoestand is gekoppel met die primêre lus teoretiese model om die werking van die stelsels te voorspel. ’n Homogene een-dimensionele eenvoudige teoretiese model van die primêre lus is afgelei en ’n rekenaar simulasie is uitgevoer. Die resultate vergelyk nie goed met die eksperimentele resultate vir enkelfasevloei en kon nie die aanvang van twee-fasevloei beskryf nie. Die aannemings van ’n een-dimensionele model met eenrigting vloei, ’n hidrostatiese druk probleem, ’n konstant volumetries vloeitempo en die onvermoë van die implementering van die kode om uitbreiding te hanteer is bekend as ’n paar van die foute in die teoretiese model. Die volgende aanbevelings word gemaak: ’n meer gevorderde ontwerp van drukreëlaar moet in die eksperiment ingesluit word; die sekondêre lus se teoretiese model moet gekenmerk word onder ’n wyer stel bedryfsomstandighede, en die rekenaar program kan gebruik word as die basis vir verdere navorsing en die implementering van alternatiewe algoritmes en modelle.

Beståndsdelarna som bildar betong är ballast, cement, vatten och ibland olika tillsatsmedel och tillsatsmaterial. När betongen blandas startar hydratationen som leder till att cementpastan expanderar och värme frigörs. Hydratationshastigheten avtar med tiden vilket gör att cementpastan efter en viss mognad kommer kontrahera. Dessa töjningsrörelser kan under olika omständigheter bidra till att sprickor uppstår. Sprickorna kan begränsas eller elimineras med hjälp av olika åtgärder.   Genom redogörelse för hur ingjutna kylrör minskar risken för att temperatursprickor uppstår i ung betong vid uppförandet av en simbassängkonstruktion kan syftet uppnås. Rapporten avgränsas till den första och andra fasen i betongens hårdnandeprocess.   En fallstudie har genomförts där metoden innefattar en intervju och dialog med sakkunniga, läsning i rekommenderad litteratur från företaget samt observation av arbetet innan, under och efter gjutning. Datan har verifierats för att bibehålla korrekt information.   Förekomsten av sprickor påverkas av olika faktorer som betongreceptet, mängden armering och temperatur. En konstruktions geometri med planerade gjutetapper är också betydelsefull för minimering av sprickor.   Ingjutna kylrör fördelar temperaturen i betongkroppen för att undvika att en för hög temperaturdifferens uppstår mellan betongens kärna och yta. Detta gör att betongens inre delar inte kommer expandera lika mycket och skapa ett inre tvång, på grund av värmen som hydratationen bidrar till. Värmeutvecklingen för de olika delarna har registrerats med hjälp av temperaturmätare, vilka resulterade i olika diagram.   I simbassängen uppkom inte några temperatursprickor. Dock var det svårt att urskilja om det var på grund av det specifika betongreceptet som användes eller om kylningen var den bidragande faktorn till resultatet.

Content of this diploma thesis is analysis of the operation of heat and cold sources and its evaluation based on data from measurement and control systém and design of a new solution for heating and cooling selected part of the object Otevřená zahrada. Building is located on the street Údolní in Brno. It is a three-storey building serving as offices of non-profit organizations and weekend activities of the organization. On the first floor there is a technical background of the building and half of it is used by four offices. On the second floor there is a seminar hall with a capacity of 50 persons. The rest of the floor is used by three meeting rooms and three offices. The third floor is used by four offices. For the heating and cooling of building, there are designed heat pumps ground-water. Air exchange in the building is provided by the air handling unit.

Continued development of highly compact and powerful electronic components has led to the need for a simple and effective method for controlling the thermal characteristics of these devices. One proposed method for thermal control involves the use of a micro heat pipe system containing a working fluid with physical properties having been speciffcally selected such that the heat pipes, as a whole, vary in effective thermal conductance, thereby providing a level of temperature regulation. To further explore this possibility, a design scenario with appropriate constraints was established and a model developed to solve for the effective thermal conductance of individual heat pipes as a function of evaporator-end temperature. From the results of this analysis, several working fluids were identified and selected from a list over thirteen hundred that were initially analyzed. Next, a thermal circuit model was developed that translated the individual heat pipe operating characteristics into the system as a whole to determine the system level effects. It was found that none of the prospective fluids could completely satisfy the established design requirements to regulate the device temperature over the entire range of operating conditions. This failure to fully satisfy design requirements was due, in large part, to the highly constrained nature of problem definition. Several fluids, however, did provide for an improved level of thermal control when compared to the unmodified design. Suggestions for improvements that may lead to enhanced levels of thermal control are offered as well as areas that are in need of further research.

District Cooling Systems (DCS) have been widely applied in large institutions such as universities, government facilities, commercial districts, airports, etc. The hydraulic system of a large DCS can be complicated. They often stem from an original design that has had extensive additions and deletions over time. Expanding or retrofitting such a system involves large capital investment. Consideration of future expansion is often required. Therefore, a thorough study of the whole system at the planning phase is crucial. An effective hydraulic model for the existing DCS will become a powerful analysis tool for this purpose. Engineers can use the model to explore alternative system configurations to find an optimal way of accommodating the DCS hydraulic system to the planned future unit. This thesis presents the first complete procedure for the use of commercial simulation software to construct the hydraulic model for a large District Cooling System (DCS). A model for one of the largest DCS hydraulic systems in the United States has been developed based on this procedure and has been successfully utilized to assist its master planning study.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 195-200).
An emerging method of propellant-less formation flight propulsion is the use of electromagnets coupled with reaction wheels. This technique is called Electromagnetic Formation Flight (EMFF). In order to create a large magnetic field necessary for actuating formation flying spacecraft, EMFF uses high temperature superconducting (HTS) wire since it is able to carry a large current at low power. To achieve superconductivity, the HTS wire needs a cryogenic thermal control system to maintain the wire temperature below the critical temperature and this temperature must be maintained over the entire EMFF coil, which could be as large as two meters in diameter. For commercially available HTS wire, this critical temperature is 110 K. Since EMFF obviates the need for consumables for formation flying maneuvers, the thermal system must also be consumable-free. The research in this thesis investigates a consumable-free method of maintaining isothermalization for a large scale HTS coil. The HTS coil resides inside a thermally conductive jacket which is used for isothermalization. A cryocooler is attached to the thermally conductive jacket and is used for heat extraction. Wrapped around the thermally conductive jacket is multilayer insulation which is used to reduce the heat load into the HTS coil. This thermal system has the ability to maintain constant temperature in the presence of a rapidly changing thermal environment, such as low Earth orbit. Both a solid conductor and a heat pipe were investigated for use as the thermally conductive jacket. Finite difference models were developed to model a single coil in space and a coil inside a vacuum chamber. In addition, the research in this thesis investigates the design, operation, and testing of a cryogenic heat pipe. The heat pipe uses nitrogen as a working fluid and a stainless steel mesh as the wicking structure. As a proof of concept, an 86 cm long heat pipe was constructed as the thermally conductive jacket enclosing the HTS wire. The working fluid, at saturation condition, maintains a constant temperature below the HTS wire critical temperature. Testing of the heat pipe in a vacuum chamber was conducted to verify the power capacity of the heat pipe. Verifying the proof of concept cryogenic heat pipe led to construction of a full scale circular heat pipe for testing in a two meter diameter toroidal vacuum chamber. This system also achieved saturation condition and showed the potential for HTS cooling. The experiments in this thesis demonstrate the feasibility of operating large HTS coils for future formation flying missions.
by Daniel W. Kwon.
Ph.D.

In this work a cooling system connected to a reactor pressure vessel has been studied using the CFD method for the purpose of investigating the strengths and shortcomings of using CFD as a tool in similar fluid flow problems within nuclear power plants. The cooling system is used to transport water of 288K (15°C) into a nuclear reactor vessel filled with water of about 555K (282°C) during certain operating scenarios. After the system has been used, the warm water inside the vessel will be carried into the cooling system by buoyancy forces. It was of interest to investigate how quickly the warm water moves into the cooling system and how the temperature field of the water changes over time. Using the open source CFD code OpenFOAM 2.3.x and the LES turbulence modelling method, a certain operating scenario of the cooling system was simulated. A simplified computational domain was created to represent the geometries of the downcomer region within the reactor pressure vessel and the pipe structure of the cooling system. Boundary conditions and other domain properties were chosen and motivated to represent the real scenario as good as possible. For the geometry, four computational grids of different sizes and design were generated. Three of these were generated using the ANSA pre-processing tool, and they all have the same general structure only with different cell sizes. The fourth grid was made by the OpenFOAM application snappyHexMesh, which automatically creates the volume mesh with little user input. It was found that for the case at hand, the different computational grids produced roughly the same results despite the number of cells ranging from 0,14M to 3,2M. A major difference between the simulations was the maximum size of the time steps which ranged from 0,3ms for the finest ANSA mesh to 2ms for the snappy mesh, a difference which has a large impact on the total time consumption of the simulations. Furthermore, a comparison of the CFD results was made with those of a simpler 1D thermal hydraulic code, Relap5. The difference in time consumption between the two analyses were of course large and it was found that although the CFD analysis provided more detailed information about the flow field, the cheaper 1D analysis managed to capture the important phenomena for this particular case. However, it cannot be guaranteed that the 1D analysis is sufficient for all similar flow scenarios as it may not always be able to sufficiently capture phenomena such as thermal shocks and sharp temperature gradients in the fluid. Regardless of whether the CFD method or a simpler analysis is used, conservativeness in the flow simulation results needs to be ensured. If the simplifications introduced in the computational models cannot be proved to always give conservative results, the final simulation results need to be modified to ensure conservativeness although no such modifications were made in this work.

Orientador: Paulo César Razuk
Banca: Augusto Ronchi Junior
Banca: Waldemar Gastoni Venturini Filho
Resumo: A fermentação alcólica, processo central da indústria cervejeira é um processo que libera uma grande quantidade de calor. Sendo assim, os recipientes de fermentação devem estar equipados com instalações de refrigeração para o correto controle da temperatura. A presente pesquisa tem como objetivo a análise da troca de calor de fermentadores cilindrocônicos dotados de sistema de refrigeração direta através de serpentina meia-cana. Para a consecução desse objetivo foi necessária a elaboração de um roteiro de cálculo seguro baseado em equações e experiências encontradas em renomadas literaturas. A análise dos resultados encontrados foi realizada a partir dos valores obtidos através do programa de cálculo atualmente utilizado em uma das maiores empresas fornecedoras deste tipo de equipamento para o mercado cervejeiro, a Dedini Indústrias de Base. Constatou-se que os valores obtidos pelo roteiro apresentado na presente dissertação foram maiores do que os calculados no programa, concluindo-se que as diferenças e dificuldades de resfriamento encontradas em equipamentos semelhantes fornecidos a clientes distintos podem ter origem na quantidade de refrigerante. As estimativas para o coeficiente global de transferência de calor independem do roteiro de cálculo seguido, pois há uma variação máxima de 3,5 % nos resultados para o cálculo deste. O mesmo é verificado para as vazões mássicas de amônia requerida, onde esta variação é ainda menor (cerca de 3,0%)
Abstract: Alcoholic fermentation, brewery industry's central process that liberates a great amount of heat. Therefore, the fermentation containers should be equipped with cooling installations for correct temperature control. The present research aims to analyze the heat exchange in cylindroconical fermenters endowed with a halp-pipe coil direct cooling system. To achieve this objective, the elaboration of a sate calculation route based on equations and experiences found in renowned references was necessary. The validation of the results was accomplished from the values obtained through the calculation program now used in one the largest supplying companies of this kind of equipment for the brewer market, Dedini indústrias de Base. It was verified that the flow of ammonia for the cooling system obtained by the itinerary introduced in the present article was larger than the one calculated in the program, and it can be concluded that the differences and cooling difficulties found in similar equipments supplied to different customers can have origin in the amount of ammonia used in the cooling system. The values for the overal heat transfer coefficient do not depend on the calculation itinerary followed, because there is a maximum variation of 3.5% in the results for the calculation of the coeffiecient. The same is verified for the mass flows of requested ammonia, where this variation is still smaller (about 3.0%)
Mestre

Ce mémoire présente l’étude du refroidissement diphasique passif d’un décodeur de télévision par le biais d’un caloduc. Il se décompose en deux grandes parties : une étude numérique des caloducs, afin de déterminer les caractéristiques géométriques et physico-chimiques des calo-ducs dans le but de refroidir de manière optimale le décodeur TV. Deux analyses numériques sont effectuées : une première qui est analytique, qui repose sur des simplifications afin d’établir une formule simple du flux maximal que l’on peut dissiper avec un caloduc dont on connais les caractéristiques demandées. Une vérification est de surcrois effectuée pour déterminer si le ca-loduc déterminé ne rentre pas dans des limitations inhérentes aux écoulements diphasiques. Dif-férents fluides sont testés. Une seconde simulation est effectuée, comportant une étude hydrau-lique couuplée a un modèle hydraulique pour simuler toutes les propriétés à l’intérieur du calo-duc, comme le rayon capillaire, les pressions, les vitesses des fluides. Cette simulation est effec-tuée grace a une méthode Runge-Kutta d’un système d’équations différentielles non linéaires couplées. La partie experimentale comporte elle aussi deux sections distinctes. La première con-siste à tester différents caloducs, afin d’optimiser leur fonctionnement lorsqu’ils sont soumis à des puissances données.Pour ce faire, un banc d’essai a été monté et un système de remplissage a été développé afin de répondre aux enjeux de la mise en place d’un caloduc. Plusieurs taux de remplissages, plusieurs fludies et différentes ailettes sont testées. Enfin, le caloduc présentant les meilleures performances est testé sur le décodeur, après avoir au préalable caractérisé le com-portement de celui-ci en fonctionnement normal
This report presents the study of a passive two-phase cooling of a television decoder using heat pipe. It is composed into two main parts: a first part concerns the numerical studies and the second an experimentalstudy. Numerical study is conducted in order to determine the geometric and physico-chemicalcharacteristics of heat pipes in order to optimally cool the TV decoder. Two numerical analyses arecarried out: a first one, which is analytical model that is based on the global study of the heat pipe inorder to determine the maximum heat flux that can be dissipated. Different working fluid could bestudied and various architectural design of heat pipe are tested. Different fluids are tested in order todetermine the best configuration of the micro-channel respecting heat pipes working limitations. Asecond model is carried out to characterize the local physical parameters such as: pressure in the liquidand vapour phases, temperature, thermal resistances, capillary radius, etc. This second simulation iscarried out by a Runge-Kutta method to solve differential equations. In the experimental part, an experimentalset up is has been installed in the laboratory to study heat pipes performances under variousexperimental conditions. A filling system has been developed for heat pipes in order to test variousworking fluids and different charges. Finally, the best configuration of the heat pipe is tested to coolOrange decoder. Different tests are conducted previously in order to make characterization of the conventionalcooling system and heat pipe cooling mod

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A fermentação alcólica, processo central da indústria cervejeira é um processo que libera uma grande quantidade de calor. Sendo assim, os recipientes de fermentação devem estar equipados com instalações de refrigeração para o correto controle da temperatura. A presente pesquisa tem como objetivo a análise da troca de calor de fermentadores cilindrocônicos dotados de sistema de refrigeração direta através de serpentina meia-cana. Para a consecução desse objetivo foi necessária a elaboração de um roteiro de cálculo seguro baseado em equações e experiências encontradas em renomadas literaturas. A análise dos resultados encontrados foi realizada a partir dos valores obtidos através do programa de cálculo atualmente utilizado em uma das maiores empresas fornecedoras deste tipo de equipamento para o mercado cervejeiro, a Dedini Indústrias de Base. Constatou-se que os valores obtidos pelo roteiro apresentado na presente dissertação foram maiores do que os calculados no programa, concluindo-se que as diferenças e dificuldades de resfriamento encontradas em equipamentos semelhantes fornecidos a clientes distintos podem ter origem na quantidade de refrigerante. As estimativas para o coeficiente global de transferência de calor independem do roteiro de cálculo seguido, pois há uma variação máxima de 3,5 % nos resultados para o cálculo deste. O mesmo é verificado para as vazões mássicas de amônia requerida, onde esta variação é ainda menor (cerca de 3,0%)
Alcoholic fermentation, brewery industry's central process that liberates a great amount of heat. Therefore, the fermentation containers should be equipped with cooling installations for correct temperature control. The present research aims to analyze the heat exchange in cylindroconical fermenters endowed with a halp-pipe coil direct cooling system. To achieve this objective, the elaboration of a sate calculation route based on equations and experiences found in renowned references was necessary. The validation of the results was accomplished from the values obtained through the calculation program now used in one the largest supplying companies of this kind of equipment for the brewer market, Dedini indústrias de Base. It was verified that the flow of ammonia for the cooling system obtained by the itinerary introduced in the present article was larger than the one calculated in the program, and it can be concluded that the differences and cooling difficulties found in similar equipments supplied to different customers can have origin in the amount of ammonia used in the cooling system. The values for the overal heat transfer coefficient do not depend on the calculation itinerary followed, because there is a maximum variation of 3.5% in the results for the calculation of the coeffiecient. The same is verified for the mass flows of requested ammonia, where this variation is still smaller (about 3.0%)

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: The feasibility of a closed loop thermosyphon for the Reactor Cavity Cooling System of the Pebble Bed Modular Reactor has been the subject of many research projects. Difficulties identified by previous studies include the hypothetical inaccuracies of heat transfer coefficient correlations available in literature. The aim of the research presented here is to develop inside-pipe heat transfer correlations that are specific to the current design of the RCCS. In order to achieve this, a literature review is performed which identifies reactors which employ closed loop thermosyphons and natural circulation. The literature review also explains the general one-dimensional two-fluid conservation equations that form the basis for numerical modelling of natural circulation loops. The literature review lastly discusses available heat transfer coefficient correlations with the aim of identifying over which ranges and under which circumstances these correlations are considered accurate. The review includes correlations commonly used in natural circulation modelling in the nuclear industry in aims of identifying correlations applicable to the modelling of the proposed RCCS. One of the objectives of this project is to design and build a one-third-height-scale model of the RCCS. Shortcomings of previous experimental models were assessed and, as far as possible, compensated for in the design of the model. Copper piping is used, eliminating material and surface property uncertainties. Several sight glasses are incorporated in the model, allowing for the visual identification of two-phase flow regimes. An orifice plate is used allowing for bidirectional flow measurement. The orifice plate, thermocouples and pipe-in-pipe heat exchangers are calibrated in-situ to minimize experimental error and aid repeatability. Twelve experiments are performed with data logging occurring every ten seconds. The results presented here are limited to selected single and two-phase flow operating mode results. Error analyses and repeatability of experimental measurements for single and two-phase operating modes as well as cooling water mass flow rates are performed, to show repeatability of experimental results. These results are used to mathematically determine the experimental inside-pipe heat transfer coefficients for both the evaporator and condenser sections. Trends in the heat transfer coefficient profiles are identified and the general behaviour of the profiles is thoroughly explained. The RCCS is modelled as a one-dimensional system. Correlations for the friction factor, heat transfer coefficient, void fraction and two-phase frictional multiplier are identified. The theoretical heat transfer coefficients are calculated using the mathematical model and correlations identified in the literature review. Fluid parameters are evaluated using experimentally determined temperatures and mass flow rates. The resulting heat transfer coefficient profiles are compared to experimentally determined profiles, to confirm the hypothesis that existing correlations do not accurately predict the inside-pipe heat transfer coefficients. The experimentally determined coefficients are correlated to 99% confidence intervals. These generated correlations, along with identified and established twophase heat transfer coefficient correlations, are used in a mathematical model to generate theoretical coefficient profiles. These are compared to the experimentally determined coefficients to show prediction accuracy.
AFRIKAANSE OPSOMMING: Die haalbaarheid van ‘n natuurlike sirkulasie geslote lus vir die Reaktor Holte Verkoeling Stelsel (RHVS) van die Korrelbed Modulêre Kern-Reaktor (KMKR) is die onderwerp van talle navorsings projekte. Probleme geïdentifiseer in vorige studies sluit in die hipotetiese onakkuraatheid van hitte-oordrag koëffisiënt korrelasies beskikbaar in literatuur. Die doel van die navorsing aangebied is om binne-pyp hitte-oordrag koëffisiënt korrelasies te ontwikkel spesifiek vir die huidige ontwerp van die RHVS. Ten einde dit te bereik, word ‘n literatuurstudie uitgevoer wat kern-reaktors identifiseer wat gebruik maak van natuurlike sirkulasie lusse. Die literatuurstudie verduidelik ook die algemene een-dimensionele twee-vloeistof behoud vergelykings wat die basis vorm vir numeriese modellering van natuurlike sirkulasie lusse. Die literatuurstudie bespreek laastens beskikbare hitte-oordrag koëffisiënt korrelasies met die doel om te identifiseer vir welke massavloei tempo waardes en onder watter omstandighede hierdie korrelasies as korrek beskou is. Die ontleding sluit korrelasies in wat algemeen gebruik word in die modellering van natuurlike sirkulasie in die kern industrie met die hoop om korrelasies vir gebruik in die modellering van die voorgestelde RHVS te identifiseer. Een van die doelwitte van die projek is om ‘n een-derde-hoogte-skaal model van die RHVS te ontwerp en te bou. Tekortkominge van vorige eksperimentele modelle is geidentifiseer en, so ver as moonlik, voor vergoed in die ontwerp van die model. Koper pype word gebruik wat die onsekerhede van materiaal en opperkvlak eindomme voorkom. Verkseie deursigtige polikarbonaat segmente is ingesluit wat visuele identifikasie van twee-fase vloei regimes toelaat. ‘n Opening plaat word gebruik om voorwaartse en terugwaartse vloeimeting toe te laat. Die opening plaat, termokoppels en hitte uitruilers is gekalibreer in plek om eksperimentele foute te verminder en om herhaalbaarheid te verseker. Twaalf eksperimente word uitgevoer en data word elke tien sekondes aangeteken. Die resultate wat hier aangebied word, is beperk tot geselekteerde enkel- en tweefase vloei meganismes van werking. Fout ontleding en herhaalbaarheid van eksperimentele metings, om die herhaalbaarheid van eksperimentele resultate te toon. Hierdie is gebruik om wiskundig te bepaal wat die eksperimentele binne-pyp hitte-oordrag koëffisiënte is vir beide die verdamper en kondenseerder afdelings. Tendense in die hitte-oordrag koëffisiënt profiele word geïdentifiseer en die algemene gedrag van die profiles is deeglik verduidelik. Die RHVS is gemodelleer as 'n een-dimensionele stelsel. Korrelasies vir die wrywing faktor, hitte-oordrag koëffisiënte, leegte-breuk en twee-fase wrywings vermenigvuldiger word geïdentifiseer. Die teoretiese hitte-oordrag koëffisiënte word bereken deur middle van die wiskundige model en korrelasies wat in literatuur geidentifiseer is. Vloeistof parameters is geëvalueer met eksperimenteel bepaalde temperature en massa-vloei tempos. Die gevolglike hitte-oordrag koëffisiënt profiles is vergelyk met eksperimentele profiele om die hipotese dat die bestaande korrelasies nie die binne-pyp hitte-oordrag koëffisiënte akkuraat voorspel nie, te bevestig. Die eksperimenteel bepaalde koëffisiënte is gekorreleer en die gegenereerde korrelasies, saam met geïdentifiseerde twee-fase hitte-oordrag koëffisiënt korrelasies, word gebruik in 'n wiskundige model om teoretiese koëffisiënt profiele te genereer. Dit word dan vergelyk met die eksperimenteel bepaalde hitteoordrag koëffisiënte om die akkuraatheid van voorspelling te toon. Tekortkominge in die teoretiese en eksperimentele model word geïdentifiseer en aanbevelings gemaak om hulle aan te spreek in die toekoms.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

In this study, the thermal management system of a notebook computer is investigated by using a commercial finite volume Computational Fluid Dynamics (CFD) software. After taking the computer apart, all dimensions are measured and all major components are modeled as accurately as possible. Heat dissipation values and necessary characteristics of the components are obtained from the manufacturer'
s specifications. The different heat dissipation paths that are utilized in the design are investigated. Two active fans and aluminum heat dissipation plates as well as the heat pipe system are modeled according to their specifications. The first and second order discretization schemes as well as two different mesh densities are investigated as modeling choices. Under different operating powers, adequacy of the existing thermal management system is observed. Average and maximum temperatures of the internal components are reported in the form of tables. Thermal resistance networks for five different operating conditions are obtained from the analysis of the CFD simulation results. Temperature distributions on the top surface of the chassis where the keyboard and touchpad are located are investigated considering the user comfort.

Fernkälte bietet das Potenzial, wirtschaftlich und ökologisch vorteilhaft zur Deckung des stetig zunehmenden Klimakältebedarfs beizutragen. Im Rahmen dieser Arbeit wurde ein dynamisches thermohydraulisches Netzmodell „ISENA“ entwickelt, mit dem während der Planung und des Betriebs von Fernkältesystemen auftretende Fragen, beispielsweise in Bezug auf Wirtschaftlichkeit und Energieeffizienz, beantwortet werden können. Das Netzmodell setzt sich aus einem quasistationären hydraulischen Modell und einem instationären thermischen Modell zusammen, das auf der Verfolgung von Wasserpfropfen durch das gesamte Netz basiert (Lagrange-Ansatz). Mit diesem Modellierungsansatz können numerische Fehler sowie Bilanzungenauigkeiten vermieden werden, sodass sich eine höhere Ergebnisgüte im Vergleich zu bisher bekannten Netzmodellen erreichen lässt. Ebenfalls neu entwickelt wurde das Teilmodell zur Abbildung der Wärmeströme über die Wände unterirdischer Rohrpaare (Kälteverluste und -gewinne). Dieses Modell erlaubt die Bestimmung der instationären Rohrwand-Wärmeströme für wärmegedämmte unterirdische Rohrpaare, Rohrpaare mit gedämmtem Vor- und ungedämmtem Rücklauf sowie ungedämmte Rohrpaare. Anhand von Validierungs- und Verifikationsrechnungen wird gezeigt, dass ISENA verlässliche Ergebnisse liefert und für die praktische Anwendung geeignet ist. Abschließende Beispielrechnungen geben einen Einblick in die Untersuchungsmöglichkeiten, die das neue Modell bietet – unter anderem im Hinblick auf den Vergleich von Pumpenregelungsvarianten, den Einfluss von Rohrdämmung und Erdreicheigenschaften auf Kälteverluste und -gewinne sowie die Einbindung von Hochtemperatur-Kälteverbrauchern in den Netzrücklauf
District cooling can provide economic and ecological benefits while supplying the increasing cooling demand for air conditioning. In the present thesis, a dynamic thermo-hydraulic model “ISENA” is presented which may be used in order to answer questions arising during design and operation of district cooling networks—e. g., that are related to economic and energy efficiency. The network model consists of a quasi-static hydraulic module and a transient thermal module being based on the tracking of water segments through the entire network (Lagrangian method). With this approach, numerical errors and inaccuracies in the balance of conserved quantities could be avoided, which eventually leads to a better reliability of the results as compared to that obtained from other network models. Additionally, a new sub-model has been developed for predicting the transient heat flux through the walls of buried pipes in order to model thermal gains and losses. This model covers un-insulated, insulated and combinations of insulated as well as un-insulated pipes. Calculations performed for the purpose of validation and verification are presented in order to demonstrate that ISENA provides reliable results and hence is suitable for practical applications. Finally, example simulations show the various possibilities provided by the new model—for example, concerning the comparison of different strategies for pump control, the influence of pipe insulation and soil properties on thermal gains and losses as well as the connection of buildings equipped with high temperature cooling systems to the return line of the network

Ce mémoire présente une étude sur le refroidissement passif de batteries lithium-ion. Il se compose de deux grandes parties. La première partie est une étude expérimentale et numérique du comportement thermique d’une batterie et la seconde partie est l’étude expérimentale d’un système passif pour le refroidissement de plusieurs batteries. Un banc d’essais expérimental a été conçu pour suivre l’évolution thermique des batteries soumises à différents courants de sollicitation. Les batteries prismatiques étudiées sont de type LFP et de capacité 60 Ah. Dans un premier temps, le comportement thermique d’une batterie soumise à des cycles de charge / décharge, est caractérisé expérimentalement. Nous montrons que la température n’est pas uniforme à la surface de la batterie et la zone la plus chaude est identifiée. Dans un second temps, un modèle numérique tridimensionnel a été développé pour prédire la température en tout point de la batterie. Ce modèle thermique permet de prédire notamment les températures à l’intérieur de la batterie, non mesurées expérimentalement et ceci, pour différents courants de sollicitation. Les données d’entrée du modèle sont issues des essais expérimentaux et de la littérature. Cette phase de caractérisation thermique de la batterie est essentielle pour la conception d’un système de refroidissement. Enfin, une étude expérimentale d’un système de refroidissement passif basé sur des caloducs et des plaques à ailettes est réalisée. Plusieurs configurations sont testées au fur et à mesure en apportant des améliorations aboutissant enfin à un système à dix caloducs munis de plaques à ailettes verticales au niveau du condenseur combinés à des plaques à ailettes placées sur les faces des batteries
This thesis deals with the passive cooling of lithium-ion batteries. It consists of two large parts. The first part is an experimental and numerical study of the thermal behaviour of a battery and the second part is the experimental study of a passive system for the cooling of several batteries. An experimental test bench was designed to monitor the thermal evolution of batteries subjected to different currents. The prismatic batteries studied are made of lithium-iron-phosphate and have a capacity of 60 Ah. In a first step, the thermal behaviour of a battery subjected to charge / discharge cycles is experimentally characterized. We show that the temperature is not uniform at the surface of the battery and the hottest area is identified. In a second step, a three-dimensional numerical model was developed to predict the temperature at any point of the battery. This thermal model makes it possible to predict in particular the temperatures inside the battery, not measured experimentally and this, for different currents. The model input data are from experimental trials and literature. This phase of thermal characterization of the battery is essential for the design of a cooling system. Finally, an experimental study of a passive cooling system based on heat pipes and finned plates is carried out. Several configurations are tested progressively with improvements leading finally to a system with ten heat pipes with vertical finned plates at the condenser combined with finned plates placed on the faces of the batteries

Etude de l'influence d'une rotation d'entrainement des parois sur la circulation secondaire d'un fluide avec ou sans transfert de chaleur. On presente un modele stationnaire qui permet des positions et orientations variables de l'axe de rotation

The diploma thesis deals with the design of the heating and cooling system, inclu-ding hot water preparation for the administrative part of the production hall. The first part of the thesis briefly discusses the history of heating and cooling of office buildings, legislative requirements and current solutions. The second part contains the design of the entire heating and cooling system with heat pump as a source of heat and cold. The final part of the thesis describes the experimental measure-ment and evaluation of the efficiency of the ice rink source.

L’objectif de cette thèse est l’optimisation énergétique d’un système de micro-cogénération et micro-tri-génération à pile à combustible. Dans un premier temps, une modélisation mathématique de tous les composants du système de cogénération à pile à combustible a été menée. L'influence de plusieurs paramètres tels que la pression et la densité de courant sur les performances de système micro-cogénération est examinée. La pertinence énergétique et environnementale du système proposé pour le contexte français est étudiée. Ensuite, une étude numérique d’un système de tri-génération composé d’une pile à combustible et d’une machine à absorption simple effet H2O/ Li-Br a été menée. L’unité de micro-tri génération est couplée à une maison unifamiliale et la performance énergétique du système est évaluée. Enfin, afin d’évaluer le potentiel de coupler le système de micro-tri-génération avec les énergies renouvelables, un système de production d’hydrogène avec les panneaux photovoltaïques «PV-H2» a été étudié. Une modélisation des différents composants du système «PV-H2» a été réalisée. Les résultats de simulation du couplage du système PV-H2 avec une maison individuelle de l’éco-quartier de la Glacerie sont présentés
The objective of this thesis is the energy optimization of the micro-cogeneration and micro-tri-generation fuel cell system. First, a mathematical modeling of all the components of the fuel cell cogeneration system was conducted. The influence of several parameters such as pressure and current density on micro-CHP system performance is examined. The energy and environmental relevance of the system for the French context is studied. Then, a numerical study of a tri-generation system consisting of a fuel cell and a single-acting H2O / Li-Br absorption machine was conducted. The micro-tri-generation unit is coupled to a single-family house and the energy performance of the system is evaluated. Finally, in order to evaluate the potential of coupling the tri-generation system with renewable energies, a hydrogen production system with photovoltaic panels «PV-H2» has been studied. A modeling of the various components of the "PV-H2" system has been carried out. The simulation results of the coupling of the «PV-H2» system with an individual house in the eco-district of La Glacerie are presented

• Für eine exakte Lichtbogenpositionierung zum Schweißpunkt werden beim Roboter – WIG-Schweißprozess folgende technische Anforderungen am Brennerkopf und dessen Wechselsystem gestellt wie: konstante Wärmeableitung und -führung im Brennerkopfbereich, schnelle Wechsel von Verschleißteilen insbesondere der Kathode, reproduzierbare Wechsel der Schweißbrennerköpfe. • Entwicklung eines neuartigen physikalischen Wirkprinzips auf Basis der Wärmeableitung – Heatpiperohr zur Gestaltung einer optimierten Wärmebilanz und Brennerkopfkühlung. • Mit dem entwickelten thermo – strömungs-mechanischen/magneto-hydro-dynamischen FE-Modells wurde die technisch-konstruktive Brennerkonstruktion mit der integrierten Wärmeableitung – Heatpiperohr für ein äußerst effektives Brennerkühlsystem unter Variation der Schweißprozessparameter zur Erzielung einer höheren Brennerdauerbelastung prozesstechnisch untersucht, analysiert und erkenntnisbezogen optimiert. • Beeinflussbar sind Lichtbogenausbildung, dessen Intensität, Verhalten sowie Temperatur- und Strömungsverhältnisse durch Prozessparameter.

Thesis (M.S.)--University of Wisconsin--Madison, 2003.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 83-85).

碩士
國立成功大學
工程科學系專班
92
Among various kinds of heat-generate components, heat-pipe cooling module is one of the commonly-used designs of heat dissipation that can bring lots of advantages, including no noise, low energy consumption, long cycle life, high heat transfer efficiency, little space occupied and light weight. Therefore, heat-pipe cooling module is fit for delicate electronic equipments as heat- dissipation device. 　　This article depicts, through experiments, it proves that dissipation efficiency can reach 61.4W with heat-pipe cooling module made by heat-pipe. The dissipation efficiency increases by 19.2%, as compared with originally-designed method for heat dissipation, that is collocation of heat-sink with an electric fan. Heat-pipe cooling module can substitute original method for use as heat dissipation device of power-transistor on high-output efficiency switching power supply appliance. 　　The experiment result shows that the factors affecting efficiency of heat-pipe cooling module are pipe contour, numbers of pipes used and pipe diameters. To the extent of influence, the biggest is a straight heat-pipes has more efficiency than a bended heat pipe by 61.8%. Secondly, efficiency of two heat-pipes is higher than that of one heat-pipe by 26.6%. Last, tube dia. 8mm is 14.6% efficient more than tube dia. 6mm. 　　In conclusion, in order to achieve the greatest heat dissipation efficiency, the best design is connection of heat-pipe cooling module that uses straight heat-pipes with switching power supply circuit.

A project report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016
Underground chilling installations have an important role in deep mining operations because the total cost of cooling a mine is minimized when underground machines deliver as high a proportion of the required cooling as practicable. Thus the refrigerating load of an underground installation should be maximized to the extent permitted both by the environment in which the installation operates, and by the physical characteristics of the machines in the installation. This study analyses how, and to what extent, the refrigerating load of older, already installed water chilling machines rejecting heat into a limited supply of return water may be maximized through configuration of their water circuits and capacity control of their compressors. Multiple-machine installations are simulated in a range of scenarios, using the thermodynamically efficient series-counterflow arrangement, to predict both the potential maximum refrigerating load and the expected refrigerating load of such installations. The simulation results indicate significant potential for installations to chill water more efficiently and thus deliver larger, maximized, refrigerating loads. For scenarios where a larger-than-design flowrate of return water is available, so permitting machines to be operated with little or no capacity control, the simulated chilling efficiency and thus the expected refrigerating loads tend toward, and in some cases almost match, the potential maximum values. For simulations in which compressor capacity control is used to prevent the return water temperature from exceeding its maximum permitted value, expected refrigerating loads fall short of their potential values, by varying amounts, due to the low machine cycle efficiency caused largely by reduced compressor isentropic efficiency at part load. For a limited supply of return water for heat rejection, the simulations indicate that load maximization efforts should focus on the machines in an installation being connected in a series-counterflow arrangement and operated, as far as practicable, at or near full capacity to create the best prospect for approaching potential maximum refrigerating load.

碩士
國立臺灣大學
機械工程學研究所
96
The higher penetration rate and better performance efficiency of personal computer (PC) nowadays has led to the improvement of cooling technology, increasing demand, and higher quality requirement of heat pipe cooling module. Following this trend, the topic of Quality Management becomes more and more important. Therefore, the existing problem of long examination process, which causes worse manufacturing efficiency and higher cost, turns to be one issue to be further improved in cooling field. Our research focus on designing the experiment methodology and process for heat pipe cooling module, and try to analyze the temperature response change of each component in heat pipe cooling module under different situations. The main experimental parameters include the heating methods, heating temperature, and time to turn on the fan. In addition, based on Lumped System theory, we build up a simulation model to find out the dynamic temperature response of heat pipe cooling module, and then set up experimental parameters. Under this simulation, we could reduce the time and cost on testing parameters and analysis principles with try and error method. The study proves to be the successful simulation model to find out suitable parameters range and analysis principles under different heating methods. Finally, our research results successfully shorten the examination time to 30 seconds through transient examination method.

碩士
淡江大學
機械與機電工程學系
92
IC industry is one of Taiwan industries gaining strong global competitiveness. With increasing functions of electrical manufactures, we need advanced cooling systems to solve the high temperature problems resulted from interior concentrative power consumption of electric device. The available fan-heat sink mechanism will be certainly not satisfying with the cooling requirement of prospective electric devices. So we bring up the study of Flat Plate Loop Heat Pipe (FPLHP) utilizing the phase change phenomenon to enhance cooling ability. In this study, FPLHP consisting of an evaporator, vapor line, air condenser, and liquid line was fabricated and characterized. Evaporator with comb grooves and copper mesh is a novel design to increase capillary pumping capacity. FPLHP were realized by bonding a glass onto copper substrate, resulting in a transparent cover for observation. Methanol, Water, and Freon (HCFC 141b) were used as the working fluid in the experiment. Preliminary result showed that FPLHP filled with methanol could dissipate heat more than 68W. Under air cooling the total thermal resistance of such a system is 1.3 °C/W and depends strongly on the cooling conditions and the radiator efficiency. Research work is continuing for the heat transfer limitation, different fluid charge rate and optimization of the FPLHP size design in an effort to improve the cooling performance of the notebook computer.

碩士
國立臺灣科技大學
機械工程系
87
The purpose of this study is used paradigm of the Holonic Manufacturing System to simplify the layout of the cooling pipe design of Injection Mold Die. On base the experience rule, energy equilibration and the shape factor. It is building the relation of the Mold for the layout, supply the structural model and speeding up to finish the flow chart of the optimization and writing program. We can get the optimal cooling time and the layout of cooling pipe design. In this research we are base on the energy equilibration and use the experience rule as the constraint domain to build the optimization model, speed up to finish optimal design and reduce the period of time for the optimization. We aim the difference shape of the product generation the problem that layout the pipe, and refer the vector and mathematics follow to build the characterize shape’s single and database. The first case, we aim the rectangle plate and use the finite difference method to identify the practicability. We follow the shape of product and employ the construct characterize shape to indicate it. Using the equivalent area conception to simplify the irregular shape and layout the cooling pipe. On the other hand, whereat the ㄇ-shape. We use the length’s expand concept to layout the cooling pipe