Academic literature on the topic 'Multi-source heat pipes'
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Journal articles on the topic "Multi-source heat pipes"
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Rightley, M. J., C. P. Tigges, R. C. Givler, C. V. Robino, J. J. Mulhall, and P. M. Smith. "Innovative wick design for multi-source, flat plate heat pipes." Microelectronics Journal 34, no. 3 (March 2003): 187–94. http://dx.doi.org/10.1016/s0026-2692(02)00187-8.
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Pekur, D. V., Yu E. Nikolaenko, and V. M. Sorokin. "New LED lamp design with heat pipes." Технология и конструирование в электронной аппаратуре, no. 5-6 (2019): 34–42. http://dx.doi.org/10.15222/tkea2019.5-6.34.
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The problem of climate change poses a challenge for humanity: it is necessary to reduce harmful emissions into the atmosphere, caused mainly by the burning of coal in thermal power plants. Partially, this problem can be solved by the use of energy-saving devices and equipment, including the replacement of traditional light sources with more efficient LEDs. This, however, causes the problem of ensuring normal thermal modes of the LEDs, since the more powerfull the LED is, the more heat is released in their semiconductor crystals, which leads to an increase in the temperature of the crystals and a decrease in the reliability of the device. This problem becomes especially urgent when using powerful multi-chip LED light sources, the so-called SOB matrices, whose power even now exceeds 500 W. This article presents a new design of a powerful LED lamp for indoor illumination of rooms with low ceilings. The heat from the LED is transferred via heat pipes to the heat exchanger rings looped around the light source. The heat exchanger rings are cooled by the natural convection of the surrounding air (at an ambient air temperature of 20°C). Computer simulation allowed evaluating the ability of the proposed cooling system to provide a normal thermal mode of the LED light source. The results on the computer simulations of the temperature field of light source`s cooling system showed that when the LED power is 300 W, the temperature of the light source`s base at the point where it is connected to the light source does not exceed 67.6°C. When the contact zone is covered with a 0.1 mm layer of heat-conducting paste (Arctiс Silver 5 type) with a thermal conductivity coefficient of 8.7 W/(m•°C), the temperature of the LED case reaches 70°C. If the thermal resistance of the LED light source is 0.1°C/W, then the temperature of its semiconductor crystals will be 100°C, well below the allowable temperature value of 150°C. The total thermal resistance of the cooling system is 0.159°C/W.
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Liu, Zhi Bin, Ji Li Zhang, and Liang Dong Ma. "Design and Research on One Avoiding-Clogging Equipment in Untreated Sewage Heat Pump Air Conditioning System." Applied Mechanics and Materials 204-208 (October 2012): 4378–83. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.4378.
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Appling urban untreated sewage as a cool and heat source of the heat pump air conditioning system is considered to be an effective way to develop urban sewage resource and a critical technique to serve the building energy system.Applications of technical difficulties are to solve the jam on sewage dirt to tube of heat exchanger and pipes. The multi-filter surface backwash technology is used to separate the suspended solids from the sewage and clean the dirt on the grille. By describing the filtration technique in the sewage source heat pump system to introduce the principle of operation and control process of the multi-filter surface backwash technology. By using in commercialese, the technology is proved to be feasible and reliability. These methods could serve as a reference for designing and application untreated sewage source heat pump systems.
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Yu, Yajie, Shaojun Xia, and Ming Zhao. "Thermodynamic Optimization of the Ethylene Oligomerization Chemical Process." Entropy 24, no. 5 (May 7, 2022): 660. http://dx.doi.org/10.3390/e24050660.
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The use of olefin oligomerization in the synthesis of liquid fuel has broad application prospects in military and civil fields. Here, based on finite time thermodynamics (FTT), an ethylene oligomerization chemical process (EOCP) model with a constant temperature heat source outside the heat exchanger and reactor pipes was established. The process was first optimized with the minimum specific entropy generation rate (SEGR) as the optimization objective, then multi-objective optimization was further performed by utilizing the NSGA-II algorithm with the minimization of the entropy generation rate (EGR) and the maximization of the C10H20 yield as the optimization objectives. The results showed that the point of the minimum EGR was the same as that of SEGR in the Pareto optimal frontier. The solution obtained using the Shannon entropy decision method had the lowest deviation index, the C10H20 yield was reduced by 49.46% compared with the point of reference and the EGR and SEGR were reduced by 59.01% and 18.88%, respectively.
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Pericault, Youen, Erik Kärrman, Maria Viklander, and Annelie Hedström. "Expansion of Sewer, Water and District Heating Networks in Cold Climate Regions: An Integrated Sustainability Assessment." Sustainability 10, no. 10 (October 17, 2018): 3743. http://dx.doi.org/10.3390/su10103743.
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This study presents an integrated sustainability assessment of technical alternatives for water and heating services provision in suburban areas affected by a cold climate. Each alternative combines a drinking water supply, sewerage (gravity or low-pressure), pipe freeze protection (deep burial or shallow burial with heat tracing) and heating solution (district heating or geothermal heat pumps). An innovative freeze protection option was considered, in which low-temperature district heating (LTDH) is used to heat trace shallow sewer and water pipes. First, the performance of each alternative regarding seven sustainability criteria was evaluated on a projected residential area in Sweden using a systems analysis approach. A multi-criteria method was then applied to propose a sustainability ranking of the alternatives based on a set of weights obtained from local stakeholders. The alternative with a deep buried gravity sewer and geothermal heat pumps was found to have the highest sustainability score in the case study. In the sensitivity analysis, the integrated trench solution with a gravity sewer, innovative heat tracing and LTDH was found to potentially top the sustainability ranking if geothermal energy was used as the district heating source, or if the weight of the cost criterion increased from 24% to 64%. The study highlights the need for integrated decision-making between different utility providers as an integrated solution can represent sustainability gains.
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Kremnyov, V., N. Korbut, K. Pianyh, and О. Shelimanova. "Features of drying of mull sewerage deposits with the help of environmental energy." Energy and automation, no. 6(52) (November 25, 2020): 59–70. http://dx.doi.org/10.31548/energiya2020.06.059.
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Analysis of sludge deposits formed during wastewater treatment gives grounds to evaluate them as a valuable raw material for obtaining biomineral fertilizers. Researcher’s efforts are focused on finding new innovative technical solutions and environmentally friendly approaches in order to make these technologies economically viable. The purpose of this study is to obtain reliable experimental data that will form the basis for a multi-stage technology for the disposal of sludge deposits. A method of combined drying is proposed, in which both the energy of the environment (solar energy) and the energy of secondary energy resources: the heat removed by the cooler from the gasification chambers and the enthalpy of the exhaust gases of gas piston engines - are simultaneously used. The real installation is equipped with a "warm floor" of pipes, in the inner space of which heated circulating water circulates from the cooling system of gas generators. In the experimental setup, the "warm floor" is modeled using a special flat, controlled electric heater. Experiments carried out with a round-the-clock supply of heat from circulating water at a temperature of 40 °C indicate that the use of a "warm floor" can increase the specific amount of moisture removed from the material during the day, almost twice. When constructing a pilot industrial dryer, it is advisable to equip it with a "warm floor" with an additional source of thermal energy, which can be used as the heat of the ground, as well as the heat of high-temperature exhaust gases of an internal combustion engine.
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Amanzholov, Tangnur, Abzal Seitov, Abdurashid Aliuly, Yelnar Yerdesh, Mohanraj Murugesan, Olivier Botella, Michel Feidt, Hua Sheng Wang, Yerzhan Belyayev, and Amankeldy Toleukhanov. "Thermal Response Measurement and Performance Evaluation of Borehole Heat Exchangers: A Case Study in Kazakhstan." Energies 15, no. 22 (November 14, 2022): 8490. http://dx.doi.org/10.3390/en15228490.
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The purpose of the present work was to determine the thermal performance of borehole heat exchangers, considering the influences of their geometric configurations and the thermophysical properties of the soil, grout and pipe wall material. A three-dimensional model was developed for the heat and mass transfer in soil (a porous medium) and grout, together with one-dimensional conductive heat transfer through the pipe walls and one-dimensional convective heat transfer of the heat transfer fluid circulating in the pipes. An algorithm was developed to solve the mathematical equations of the model. The COMSOL Multiphysics software was used to implement the algorithm and perform the numerical simulations. An apparatus was designed, installed and tested to implement the thermal response test (TRT) method. Two wells of depth 50 m were drilled in the Almaty region in Kazakhstan. Gravel and till/loam were mainly found, which are in accordance with the stratigraphic map of the local geological data. In each well, two borehole heat exchangers were installed, which were an integral part of the ground source heat pump. The TRT measurements were conducted using one borehole heat exchanger in one well and the data were obtained. The present TRT data were found to be in good agreement with those available in literature. The numerical results of the model agreed well with the present TRT data, with the root-mean-square-deviation within 0.184 °C. The TRT data, together with the predictions of the line-source analytical model, were utilized to determine the soil thermal conductivity (λg = 2.35 W/m K) and the thermal resistance of the borehole heat exchanger from the heat transfer fluid to the soil (Rb = 0.20 m K/W). The model was then used to predict the efficiencies of the borehole heat exchangers with various geometric configurations and dimensions. The simulation results show that the spiral borehole heat exchanger extracts the highest amount of heat, followed by the multi-tube, double U-type parallel, double U-type cross and single U-type. It is also found that the spiral configuration can save 34.6% drilling depth compared with the conventional single U-type one, suggesting that the spiral configuration is the best one in terms of the depth and the maximum heat extracted. The simulation results showed that (i) more heat was extracted with a higher thermal conductivity of grout material, in the range of 0.5–3.3 W/m K; (ii) the extracted heat remained unchanged for a thermal conductivity of pipe material higher than 2.0 W/m K (experiments in the range of 0.24–0.42 W/m K); (iii) the extracted heat remained unchanged for a volumetric flow rate of water higher than 1.0 m3/h (experimental flow rate 0.6 m3/h); and (iv) the heat extracted by the borehole heat exchanger increased with an increase in the thermal conductivity of the soil (experiments in the range of 0.4–6.0 W/m K). The numerical tool developed, the TRT data and simulation results obtained from the present work are of great value for design and optimization of borehole heat exchangers as well as studying other important factors such as the heat transfer performance during charging/discharging, freezing factor and thermal interference.
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Bockelmann, Franziska, and M. Norbert Fisch. "It Works—Long-Term Performance Measurement and Optimization of Six Ground Source Heat Pump Systems in Germany." Energies 12, no. 24 (December 10, 2019): 4691. http://dx.doi.org/10.3390/en12244691.
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Long-term studies of ground source heat pump (GSHP) heating and cooling systems for six different buildings (commercial, institutional and multi-family buildings) were conducted in Germany by Steinbeis-Innovationszentrum (SIZ) energy+. Three of them are equipped with borehole heat exchangers, and the others use energy piles as heat exchangers. This paper deals with a demonstration of the investigated buildings, the measured values and performance, and the obtained results include important findings and experiences, problems encountered and possible preventive measures to avoid mistakes. After ten years of operation, it can be stated that the systems work and achieve their planned efficiency but require constant control and regulation to avoid faulty operation. An analysis of the implemented control strategies shows that, for all these heating and cooling systems, holistically coordinated control strategies that are verified during commissioning are required.
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Zhou, Yan, Wenping Liu, Haojie Bi, Riqiang Chen, Shixiang Zong, and Youqing Luo. "A Detection Method for Individual Infected Pine Trees with Pine Wilt Disease Based on Deep Learning." Forests 13, no. 11 (November 9, 2022): 1880. http://dx.doi.org/10.3390/f13111880.
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Pine wilt disease (PWD) can cause destructive death in many species of pine trees within a short period. The recognition of infected pine trees in unmanned aerial vehicle (UAV) forest images is a key technology for automatic monitoring and early warning of pests. This paper collected UAV visible and multispectral images of Korean pines (Pinus koraiensis) and Chinese pines (P. tabulaeformis) infected by PWD and divided the PWD infection into early, middle, and late stages. With the open-source annotation tool, LabelImg, we labeled the category of infected pine trees at each stage. After coordinate-correction preprocessing of the ground truth, the Korean pine and Chinese pine datasets were established. As a means of detecting infected pine trees of PWD and determining different infection stages, a multi-band image-fusion infected pine tree detector (MFTD) based on deep learning was proposed. Firstly, the Halfway Fusion mode was adopted to fuse the network based on four YOLOv5 variants. Simultaneously, the Backbone network was initially designed as a dual branching network that includes visible and multispectral subnets. Moreover, the features of visible and multispectral images were extracted. To fully utilize the features of visible and multispectral images, a multi-band feature fusion transformer (MFFT) with a multi-head attention mechanism and a feed-forward network was constructed to enhance the information correlation between visible and multispectral feature maps. Finally, following the MFFT module, the two feature maps were fused and input into Neck and Head to predict the categories and positions of infected pine trees. The best-performing MFTD model achieved the highest detection accuracy with mean average precision values (mAP@50) of 88.5% and 86.8% on Korean pine and Chinese pine datasets, respectively, which improved by 8.6% and 10.8% compared to the original YOLOv5 models trained only with visible images. In addition, the average precision values (AP@50) are 87.2%, 93.5%, and 84.8% for early, middle, and late stages on the KP dataset and 81.2%, 92.9%, and 86.2% on the CP dataset. Furthermore, the largest improvement is observed in the early stage with 14.3% and 11.6%, respectively. The results show that MFTD can accurately detect the infected pine trees, especially those at the early stage, and improve the early warning ability of PWD.
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Hasan Al-Hafadhi, Mahmood, and Gyorgy Krallics. "Prediction and numerical simulation of residual stress in multi-pass pipe welds." Pollack Periodica, March 24, 2021. http://dx.doi.org/10.1556/606.2020.00127.
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AbstractA numerical simulation procedure is presented to predict residual stress states in multi-pass welds in oil transportation pipes. In this paper, a two-dimensional thermo-mechanical finite element model is used to calculate the temperature distribution, hardness, and the distribution of residual stresses during multi-pass welding of pipes of dissimilar metals and varying thicknesses. In this model, the temperature dependence of the thermal and mechanical properties of the material was considered. The present model was validated using the hardness measurement. Good agreement was found between the measurement and the numerical simulation results. The simulated result shows that the two-dimensional model can be effectively used to simulate the hardness test and predict the residual stress in the pipe weld. The simulation results and measurements suggest that the model with moving heat source can obtain a good prediction of residual welding stress. Both the two-dimensional and the three-dimensional modeling can be used to estimate the residual stresses in different weld regions and help saving time.
Dissertations / Theses on the topic "Multi-source heat pipes"
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Fu-Rung, Yu, and 余富榮. "Study on Multi-heat Source Management using Three-Dimensional Loop Heat Pipe." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/02218987489554446688.
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碩士國防大學理工學院
機械工程碩士班
101
This research is to pre-develop a new highly adaptable loop heat pipe, which is featured with simplicity in making, high thermal efficiency, and configuration adaptability to the heat source position and heat flux volume, and used to treat three-dimensional multiple heat sources in a limited space. This research uses pressurized gas generated by capillary structure to resist gravity, and in the same conditions uses the bending curvature design to explore the gravity impact on the entire device. In the end, heat sources of different quantities, positions and powers are discussed to find out the variations of the parameters for an effective heat dissipation result. In this research, electronic instruments of military specifications are studied, and the loop heat pipe's unique features of stand-alone operation, anti-vibration, low thermal resistance, and long thermal transmission distance are applied for the design and production of the three-dimensional loop heat pipe in a multiple heat sources environment. The low-cost, highly heat-transfer efficient loop cooling mechanism is used to make the electronic devices in a sealed environment highly reliable, and able to tackle other extended dissipation issues as well. This three-dimensional, multiple-heat-sources loop heat pipe developed in this research has descending powers by the targets in phases, in order to measure the thermal resistance variation along with the decreasing of the input powers. Vacuuming is used to reduce the working substance saturation and capillary structure in order to increase the contact area between the working substance and the heat sources for expediting the change of the working substance phase. After the working substance phase is changed, the generated pressure will make the working substance within the system transmit heat in the designed directions. This research has found out that when the input power of the main heat sources of the three-dimensional, triple-heat-sources loop heat pipe is at its peak (60W) and the input power of the secondary heat sources is at its bottom (15W), the lowest thermal resistance of this research can be obtained; while the input power of the main heat sources is at its bottom (40W) and the input power of the secondary heat sources is at its peak (30W), the highest thermal resistance of this research can be obtained, and result remains unchanged even if the bottom input power of the heat sources vary.
Conference papers on the topic "Multi-source heat pipes"
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Brar, Gurinder Singh. "Residual Stresses in Butt Welding of Two Circular Pipes: An Experimental and Numerical Investigation." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-29082.
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Welding is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Welding is carried out with a very complex thermal cycle which results in irreversible elastic-plastic deformation and residual stresses in and around fusion zone and heat affected zone (HAZ). A residual stress due to welding arises from the differential heating of the plates due to the weld heat source. Residual stresses may be an advantage or disadvantage in structural components depending on their nature and magnitude. The beneficial effect of these compressive stresses have been widely used in industry as these are believed to increase fatigue strength of the component and reduce stress corrosion cracking and brittle fracture. But due to the presence of residual stresses in and around the weld zone the strength and life of the component is also reduced. To understand the behavior of residual stresses, two 10 mm thick Fe410WC mild steel plates are butt welded using the Metal Active Gas (MAG) process. An experimental method (X-ray diffraction) and numerical analysis (finite element analysis) were then carried out to calculate the residual stress values in the welded plates. Three types of V-butt weld joint — two-pass, three-pass and four-pass were considered in this study. In multi-pass welding operation the residual stress pattern developed in the material changes with each weld pass. In X-ray diffraction method, the residual stresses were derived from the elastic strain measurements using a Young’s modulus value of 210 GPa and Poisson’s ratio of 0.3. Finite element method based, SolidWorks software was used to develop coupled thermal-mechanical three dimension finite element model. The finite element model was evaluated for the transient temperatures and residual stresses during welding. Also variations of the physical and mechanical properties of material with the temperature were taken into account. The numerical results for peak transverse residual stresses attained in the welded plates for two-pass, three-pass and four-pass welded joint were 67.7 N/mm2, 58.6 N/mm2, and 48.1 N/mm2 respectively. The peak temperature attained during welding process comes out to be 970°C for two-pass weld, 820.8°C for three-pass weld and 651.9°C for four-pass weld. It can be concluded that due to increase in the number of passes during welding process or deposition weld beads, the residual stresses and temperature distribution decrease. Also, the results obtained by finite element method agree well with those from experimental X-ray diffraction method.
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Ekoto, Isaac W., William G. Houf, Adam J. Ruggles, Leonard W. Creitz, and Jimmy X. Li. "Large-Scale Hydrogen Jet Flame Radiant Fraction Measurements and Modeling." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90535.
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Analytic methods used to establish thermal radiation hazard safety boundaries from ignited hydrogen plumes are based on models previously developed for hydrocarbon jet fires. Radiative heat flux measurements of small- and medium-scale hydrogen jet flames (i.e., visible flame lengths < 10 m) compare favorably to theoretical calculations provided corrections are applied to correct for the product species thermal emittance and the optical flame thickness. Recently, Air Products and Chemicals Inc. commissioned flame radiation measurements from two larger-scale hydrogen jet flames to determine the applicability of current modeling approaches to these larger flames. The horizontally orientated releases were from 20.9 and 50.8 mm ID pipes with a nominal 60 barg source pressure and respective mass flow rates of 1.0 and 7.4 kg/s. Care was taken to ensure no particles were entrained into the flame, either from the internal piping or from the ground below. Radiometers were used to measure radiative heat fluxes at discrete points along the jet flame radial axis. The estimated radiant fraction, defined as the radiative energy escaping relative to chemical energy released, exceeded correlation predictions for both flames. To determine why the deviation existed, an analysis of the data and experimental conditions was performed by Sandia National Laboratories’ Hydrogen Safety, Codes and Standards program. Since the releases were choked at the exit, a pseudo source nozzle model was needed to compute flame lengths and residence times, and the results were found to be sensitive to the formulation used. Furthermore, it was thought that ground surface reflection from the concrete pad and steel plates may have contributed to the increased recorded heat flux values. To quantify this impact, a weighted multi source flame radiation model was modified to include the influence of planar surface radiation. Model results were compared to lab-scale flames with a steel plate located close to and parallel with the release path. Relative to the flame without a plate, recorded heat flux values were found to increase by up to 50% for certain configurations, and the modified radiation model predicted these heat fluxes to within 10% provided a realistic steel reflectance value (0.8) was used. When the plate was heavily and uniformly oxidized, however, the reflectance was sharply attenuated. Model results that used the surface reflectance correction for the larger-scale flames produced good agreement with the heat flux data from the smaller of the two flames if an estimated reflectance of 0.5 was used, but was unable to fully explain the under predicted heat flux values for the larger flame.
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Oguma, Masahito, Takeshi Matsumoto, Ayako Funabiki, Futoshi Miyaoka, Kosuke Ito, and Takao Kakizaki. "Numerical Solution of a Ground Source Heat Pump System Using Foundation Piles." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17315.
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A ground source heat pump (GSHP) system has higher cooling and heating performances than an air source heat pump system, so the GSHP system has attracted attention in the cold regions. Particularly after the 2011 earthquake off the Pacific coast of Tohoku, which damaged nuclear power plants, the GSHP utilizing renewable energy, has become attractive in heating system in the Tohoku region. However, it is necessary to install wells to collect ground source heat, and so, together with the cost of the heat pump itself, the installation cost is a barrier to widespread adoption of this technology in Japan. On the other hand, due to poor subsoil, foundation piles are often required in the construction of buildings in Japan. By using foundation piles as heat exchangers, which are commonly used in residential construction, the cost of using GSHP systems in houses may be reduced. However, since the placement of the piles depends on the floor layout of the residence, that is arbitrary sequence. Moreover, an arbitrary floor layout requires a complicated multi-dimensional numerical analysis to design the GSHP, and the analysis is burdensome for general designers. Therefore, the use of the model unit of the two-dimensional cylindrical heat exchange well is proposed. The use of this model, which includes an unused volume of soil, reduces the analysis burden for general design tools. On experience, the arrangement rate is 4 m2 per pile, and the well separation is narrow. And the foundation piles will form a group. So thermal interference between heat exchanger wells might be working hard. In addition, the foundation piles are very short, compared to the traditional borehole depth of 50 to 100 m. Therefore, the thermal performance of the well may degrade compared to that of the traditional GSHP system, although the initial costs are less. Therefore, we examined a GSHP system with heat exchanger piles by using the heat exchange well unit model for residences in the Tohoku region. As a result, the two-dimensional analysis and more is needed to predict the thermal performances of the heat exchanger piles so that the effect of the pitch of the heat exchange wells on the heat transfer in the axial direction will be large. In cold climates, the heating demand is large and, in the summer, the amount of waste heat to the ground is small, so a large amount of heat penetration into the ground from the atmospheric air is important for continuous GSHP operation in the Tohoku region, and in Fukushima Prefecture in particular.
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Ghanta, Nikhilesh, and Arvind Pattamatta. "A Numerical and Optimization Study of Compressible Phase-Change Heat Transfer in a Part-Unit-Cell Model of a Pulsating Heat Pipe (PHP)." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66440.
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The heat transfer capacity of a PHP is tremendously high and is finding many applications such as in electronic cooling. In order to maximize its heat transfer potential, the working parameters of a PHP have to be set to the right values. The present work deals with the optimization study of a part-unit-cell model of a Pulsating Heat Pipe (PHP) comprising of a single meniscus oscillating between evaporator and adiabatic sections. The parameters considered for this study are the effective length of the evaporator section, the evaporator temperature and the fluid fill ratio. All the numerical studies on PHP till date make the approximation of incompressibility of working fluid. However, recent experimental studies by M.Rao et al. [1] have shown the importance of compressibility effects on the working of a PHP. The present work involves a compressible phase change heat transfer model, based on the Volume-of-Fluid solver. The compressible model is incorporated into open source CFD solver OpenFOAM. This solver is validated in stages by Ghanta and Pattamatta [2] and the part-unit cell of the PHP is validated against the existing experimental results of M. Rao et al [1] and contrast is made with an incompressible solver, to emphasise the importance of considering the compressibility effects. Following validation of the compressible phase change solver, a parametric study explaining the effects of the above mentioned parameters on the objective functions and working of the PHP is performed, which forms the basis for the optimization presented in this work. Accordingly, the ratio of evaporator to the adiabatic length (Le/La) is varied between 2 and 10, the evaporator superheat between 5 and 20 and the fluid filling ratio is varied between 35–80 %. A multi-objective optimization problem is set-up taking the maximum vapour pressure attained and working time (the time for which the working fluid is in contact with the part unit cell of the PHP) as the objective functions. Models are created using two different methods — Kriging and Response Surface Approximation (RSA). The models are optimized using multi-objective Genetic Algorithm, coded in MATLAB. Both the models used predicted the same optimum values, with a variation of 0.01%. The optimum values point at a fluid fill ratio of 79.5%, evaporator excess temperature of 7.89 and an evaporator section of length seven times that of the adiabatic section. The same is also validated with results of numerical simulation at the optimal point. In majority of the works presented so far, the maximum vapour pressure alone is taken as a benchmark for the performance of the PHP. To elucidate the importance of considering working time as an objective function, a single objective optimization study was also performed, with only the maximum pressure as the objective function. The results of single objective optimization showed a deviated optimal point, with similar optimal pressure value as that of multi-objective optimization, but working time reduced by half. Hence by not considering the working time of PHP as an objective function, the optimal point generated results in only half the maximum heat transfer that can otherwise be attained with different parameters.
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Cheng, Jiangtao, and Chung-Lung Chen. "Spot Cooling Using Electrowetting-Controlled Thin Film Heat Transfer." In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75032.
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We report an electrowetting-controlled cooling system with site-specific treatments on the heat source (evaporator or hot spot) surfaces. Electrowetting-on-dielectric (EWOD) has great potential in thermal management because EWOD-driven droplet transport has unique characteristics of prompt response, low power consumption and programmable paths without the need for any mechanical moving parts. Prompt and fast droplet transport is necessary for adaptive and active cooling of high heat flux targets. Using a multi-channel DC/AC control system, we carried out sequenced activation of AC voltages on coplanar electrodes and transmitted a droplet to the spot target along a programmable path. With high positioning accuracy at the chip level, we have successfully transmitted a water droplet of 15 μL at speeds as high as ∼10 cm/s. We further improved electrowetting cooling performance by coating a fine copper screen on the cooling targets. The capillarity associated with the copper screen facilitates the delivered droplets automatically spreading and clinging to the target surfaces. As a result, heat transfer is in the more efficient form of filmwise evaporation at the evaporator sites. To maintain a thin film with proper thickness on the hot spots, we implemented EWOD-assisted droplet splitting and merging to precisely control the droplet volume to avoid fluid flooding (accumulation) on the hot spot surfaces. Our investigation indicates that thin-film evaporation is a high-efficiency heat transfer mechanism on a hydrophilized hot spot surface. Based on EWOD technique with surface treatments, the superheat on a hot spot of 4mm × 4mm was maintained well below 30°C even when the heat flux reached as high as 80W/cm2. The closed loop of this novel thermal management system can potentially function as a wickless vapor chamber or heat pipe with enhanced heat dissipation capabilities.
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Huang, Hui, Jian Chen, Blair Carlson, Hui-Ping Wang, Paul Crooker, Gregory Frederick, and Zhili Feng. "Prediction of Residual Stresses in a Multipass Pipe Weld by a Novel 3D Finite Element Approach." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-85044.
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Due to enormous computation cost, current residual stress simulation of multipass girth welds are mostly performed using two-dimensional (2D) axisymmetric models. The 2D model can only provide limited estimation on the residual stresses by assuming its axisymmetric distribution. In this study, a highly efficient thermal-mechanical finite element code for three dimensional (3D) model has been developed based on high performance Graphics Processing Unit (GPU) computers. Our code is further accelerated by considering the unique physics associated with welding processes that are characterized by steep temperature gradient and a moving arc heat source. It is capable of modeling large-scale welding problems that cannot be easily handled by the existing commercial simulation tools. To demonstrate the accuracy and efficiency, our code was compared with a commercial software by simulating a 3D multi-pass girth weld model with over 1 million elements. Our code achieved comparable solution accuracy with respect to the commercial one but with over 100 times saving on computational cost. Moreover, the three-dimensional analysis demonstrated more realistic stress distribution that is not axisymmetric in hoop direction.
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Feng, Yi, Y. Wang, and C. Y. Huang. "Study on Copper Cold Plate Designs for Electronics Liquid Cooling System." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-16242.
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The increasing power consumption of microelectronic systems and the dense layout of semiconductor components leave very limited design spaces with tight constraints for the thermal solution. Conventional thermal management approaches, such as extrusion, fold-fin, and heat pipe heat sinks, are somehow reaching their performance limits, due to the geometry constraints. Currently, more studies have been carried out on the liquid cooling technologies, as the flexible tubing connection of liquid cooling system makes both the accommodation in constrained design space and the simultaneous cooling of multi heating sources feasible. To significantly improve the thermal performance of a liquid cooling system, heat exchangers with more liquid-side heat transfer area with acceptable flow pressure drop are expected. This paper focuses on the performance of seven designs of source heat exchanger (cold plate). The presented cold plates are all made in pure copper material using wire cutting, soldering, brazing, or sintering process. Enhanced heat transfer surfaces such as micro channel and cooper mesh are investigated. Detailed experiments have been conducted to understand the performance of these seven cooper cold plates. The same radiators, fan, and water pump were connected with each cooper cold plate to investigate the overall thermal performance of liquid cooling system. Water temperature readings at the inlets and outlets of radiators, pump, and colder plate have been taken to interpret the thermal resistance distribution along the cooling loop.
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Ayrault, Danie`le, Alix Bonaventure, Olivier Asserin, Guillaume Montay, and Vincent Klosek. "Numerical and Experimental Evaluation of Residual Stresses in Dissimilar Weld Joints." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57523.
Full textAbstract:
This paper describes finite element modelling of residual stresses in tubular dissimilar weld joints. To validate numerical approach, residual stresses are determined experimentally in various locations of the welded specimen by using complementary methods such as neutron diffraction technique and increment hole drilling method combined to speckle interferometry. Dissimilar metal weld specimens (DMW), representative of configurations in primary coolant circuit of pressurized water nuclear reactors, are produced using AISI 316L stainless steel and low alloy carbon 16MND5 steel as base materials and a nickel based filler metal (Inconel 82) for buttering of the ferritic side and the filling between the buttered pipe and stainless steel one. The simulation of the manufacturing procedure of the DMW specimen is firstly performed thanks to an equivalent heat source. Secondly, the mechanical behaviour is calculated by using the computed thermo-metallurgical history for each welded pass. The “birth and death” elements method is used to simulate the addition of filler metal for this multi-pass welding configuration. A relatively good agreement is observed between the calculated and experimental results.