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Artykuły w czasopismach na temat "REFRIGERANT COUPLE"
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Xu, Lei, Yan Long Jiang, Nian Yong Zhou i Jun Li. "Study on the Performance of an Open Loop Cycle CO2 Refrigeration System in the Extreme Limit Condition". Advanced Materials Research 1025-1026 (wrzesień 2014): 178–82. http://dx.doi.org/10.4028/www.scientific.net/amr.1025-1026.178.
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As a result of the strict restrictions on the use of power supply under the mine disaster, the Open loop cycle CO2 refrigeration system is used in the Mine Rescue Cabin. Traditional system have got a couple of equipment malfunctions frequently, such as the Ice-block in Cold-start, Cold-frost and Overheating. In this paper, a new type of refrigeration system is designed after the Thermodynamic analysis of extreme limit condition. The new system avoids the Ice-block and the cold-frost by limit the refrigerant flow, it also can improve the capability of the evaporator. It has a important reference value to the research and application of the open loop cycle CO2 refrigeration system in the extreme condition.
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Martinazzoli, Gianni, Daniele Pasinelli, Adriano Maria Lezzi i Mariagrazia Pilotelli. "Design of a 5th Generation District Heating Substation Prototype for a Real Case Study". Sustainability 15, nr 4 (7.02.2023): 2972. http://dx.doi.org/10.3390/su15042972.
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The evolution of district heating networks is moving toward low temperatures in heat distribution with so called 4th generation networks. However, the lowest heat transfer fluid temperatures in district heating are achieved through ultra-low temperature networks, referred to as 5th generation district heating networks (5GDHNs). Low temperatures in heat distribution results in an extremely different configuration of 5GDHN compared to traditional district heating network, especially in the grid substation due to the inability to directly couple the grid with the buildings. This paper presents a detailed design of a 5th generation substation prototype, which is carried out to verify the proper operation and monitor the performance of this type of substation in a real case study. The prototype is fed by low-temperature waste heat, currently dissipated through evaporative towers, and will be built in the city of Brescia, Italy. The layout of the substation prototype, consisting of a bidirectional pumping system, a reversible water-to-water heat pump, an inertial thermal energy storage and a heat exchanger, is presented. An analysis is performed to figure out which refrigerant offers the best performance of the heat pump. In addition, fixed the refrigerant, the performance of the grid connected heat pump is found to be increased from 29.5% to 55.5% for both heating and cooling compared with a stand-alone air-to-water heat pump solution. Finally, the process flow diagram and the piping and instrumentation diagram of the substation are presented and commented.
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Aprea, Ciro, Adriana Greco, Angelo Maiorino i Claudia Masselli. "Enhancing the Heat Transfer in an Active Barocaloric Cooling System Using Ethylene-Glycol Based Nanofluids as Secondary Medium". Energies 12, nr 15 (28.07.2019): 2902. http://dx.doi.org/10.3390/en12152902.
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Barocaloric cooling is classified as environmentally friendly because of the employment of solid-state materials as refrigerants. The reference and well-established processes are based on the active barocaloric regenerative refrigeration cycle, where the solid-state material acts both as refrigerant and regenerator; an auxiliary fluid (generally water of water/glycol mixtures) is used to transfer the heat fluxes with the final purpose of subtracting heat from the cold heat exchanger coupled with the cold cell. In this paper, we numerically investigate the effect on heat transfer of working with nanofluids as auxiliary fluids in an active barocaloric refrigerator operating with a vulcanizing rubber. The results reveal that, as a general trend, adding 10% of copper nanoparticles in the water/ethylene-glycol mixture carries to +30% as medium heat transfer enhancement.
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Kunert, Anna T., Mark Lamneck, Frank Helleis, Ulrich Pöschl, Mira L. Pöhlker i Janine Fröhlich-Nowoisky. "Twin-plate Ice Nucleation Assay (TINA) with infrared detection for high-throughput droplet freezing experiments with biological ice nuclei in laboratory and field samples". Atmospheric Measurement Techniques 11, nr 11 (23.11.2018): 6327–37. http://dx.doi.org/10.5194/amt-11-6327-2018.
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Abstract. For efficient analysis and characterization of biological ice nuclei under immersion freezing conditions, we developed the Twin-plate Ice Nucleation Assay (TINA) for high-throughput droplet freezing experiments, in which the temperature profile and freezing of each droplet is tracked by an infrared detector. In the fully automated setup, a couple of independently cooled aluminum blocks carrying two 96-well plates and two 384-well plates, respectively, are available to study ice nucleation and freezing events simultaneously in hundreds of microliter-range droplets (0.1–40 µL). A cooling system with two refrigerant circulation loops is used for high-precision temperature control (uncertainty <0.2 K), enabling measurements over a wide range of temperatures (∼ 272–233 K) at variable cooling rates (up to 10 K min−1). The TINA instrument was tested and characterized in experiments with bacterial and fungal ice nuclei (IN) from Pseudomonas syringae (Snomax®) and Mortierella alpina, exhibiting freezing curves in good agreement with literature data. Moreover, TINA was applied to investigate the influence of chemical processing on the activity of biological IN, in particular the effects of oxidation and nitration reactions. Upon exposure of Snomax® to O3 and NO2, the cumulative number of IN active at 270–266 K decreased by more than 1 order of magnitude. Furthermore, TINA was used to study aqueous extracts of atmospheric aerosols, simultaneously investigating a multitude of samples that were pre-treated in different ways to distinguish different kinds of IN. For example, heat treatment and filtration indicated that most biological IN were larger than 5 µm. The results confirm that TINA is suitable for high-throughput experiments and efficient analysis of biological IN in laboratory and field samples.
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Rony, Rajib, Huojun Yang, Sumathy Krishnan i Jongchul Song. "Recent Advances in Transcritical CO2 (R744) Heat Pump System: A Review". Energies 12, nr 3 (31.01.2019): 457. http://dx.doi.org/10.3390/en12030457.
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Heat pump (HP) is one of the most energy efficient tools for address heating and possibly cooling needs in buildings. Growing environmental concerns over conventional HP refrigerants, chlorofluorocarbons (CFCs), and hydrofluorocarbons (HFCs) have forced legislators and researchers to look for alternatives. As such, carbon dioxide (R744/CO2) has come to light due to its low global warming potential (GWP) and zero ozone depleting characteristics. Even though CO2 is environmentally benign, the performance of CO2 HP has been of concern since its inception. To improve the performance of CO2 HP, research has been playing a pivotal role in developing functional designs of heat exchangers, expansion devices, and compressors to suit the CO2 transcritical cycle. Different CO2 HP cycles coupled with auxiliary components, hybrid systems, and refrigerant mixtures along with advanced control strategies have been applied and tested. This paper presents a complete overview of the most recent developments of transcritical CO2 HPs, their components, and applications.
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Fouad, Wael A., i Lourdes F. Vega. "The phase and interfacial properties of azeotropic refrigerants: the prediction of aneotropes from molecular theory". Physical Chemistry Chemical Physics 19, nr 13 (2017): 8977–88. http://dx.doi.org/10.1039/c6cp08031f.
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He, Dazhuang, Yangfan Liu i Davide Ziviani. "Numerical modeling of noise and vibration due to discharge in hermetic compressors". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 264, nr 1 (24.06.2022): 362–77. http://dx.doi.org/10.3397/nc-2022-741.
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The pulsive and intermittent nature of the operation of a hermetic refrigeration compressor leads to the generation of noise and vibration during the operation. Specifically, in hermetic compressors, gas pulsation induced by refrigerant discharge is a major source of NVH effects. The generation of noise and vibration due to refrigerant gas discharge is a process that involves thermo-mechanical operation within compressor cylinder, cavity acoustic resonance, valve opening/closing, hermetic shell vibration, and exterior sound radiation. In the presented study, a numerical simulation model was developed to address the multi-physical process of noise generation due to refrigerant gas discharge. The thermodynamics aspects of the compression process and the vibro-acoustics aspects are coupled together. The thermo-mechanical submodel is based on a compressor mechanistic model based on control volume analysis with lumped parameters. The vibro-acoustics submodel is based on finite element analysis, and it describes the two-way coupled interaction of compressor cavity acoustic resonances and hermetic shell vibration. Meanwhile, the acoustics response in the cavity is coupled with the thermodynamics submodel through proper modeling dynamics of discharge valves. Numerical simulations were conducted to demonstrate how simulation models work and how they can potentially help compressor manufacturers to gain a better understanding of the physical reasons behind NVH effects of compressors.
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Mohammadi, Kasra, i Kody M. Powell. "Thermoeconomic Evaluation and Optimization of Using Different Environmentally Friendly Refrigerant Pairs for a Dual-Evaporator Cascade Refrigeration System". Processes 9, nr 10 (19.10.2021): 1855. http://dx.doi.org/10.3390/pr9101855.
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Applications of dual-evaporator refrigeration systems have recently gained much attention both in academia and industry due to their multiple benefits. In this study, a comprehensive thermodynamic and economic analysis is conducted to evaluate the potential of using several environmentally friendly refrigerant couples and identifies the most suitable one yielding the best economic results. To achieve this goal, a detailed parametric study is conducted, and an optimization process is performed using a particle swarm optimization (PSO) approach to minimize the unit production cost of cooling (UPCC) of the cascade refrigeration system. The results showed that among all selected 18 refrigerant pairs and for all ranges of examined operating parameters, the R170-R161 pair and R1150-R1234yf pair are identified as the best and worst pairs, respectively, from both thermodynamic and economic viewpoints. The results also confirm that R170-R161 pair has an improvement over R717-R744, used as a typical refrigerant pair of cascade refrigeration cycles. For a base case analysis, the COP of R170-R161 and R1150-R1234yf pairs is determined as 1.727 and 1.552, respectively, while their UPCC is found to be $0.395/ton-hr and $0.419/ton-hr, respectively, showing the influence of proper selection of refrigerant pairs on the cascade cycle’s performance. Overall, this study offers a useful thermodynamic and economic insight regarding the selection of proper refrigerant pairs for a dual-evaporator cascade vapor compression refrigeration system.
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Lee, Sangheon, Chulung Cheong i Jinhyung Park. "Development of flow-vibroacoustic coupled numerical methods for prediction of noise radiation due to flow-born vibration of compressor discharge piping system". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, nr 1 (1.02.2023): 6032–39. http://dx.doi.org/10.3397/in_2022_0896.
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The compressor and fan in air conditioner outdoor unit are the core component which deter-mines noise performance as well as cooling or heating performance. Among these, the com-pressor has larger contribution to the noise of outdoor units. For high efficiency air condition-er, the size and operating speed of compressor are smaller and faster. The high-speed com-pressor causes loud noise which is complaints for the customer. Traditionally, it is well-known that the vibration of compressor and connected duct is main noise source. However, as the compressor speed increases, the refrigerant flow in the compressor discharge duct also emerged as a major noise source. To reduce the compressor noise operating at high speed, it is necessary to analyze vibrational and acoustic characteristics of compressor discharge duct. This duct noise has the two-types source: structure born noise and flow induced noise. The structure born noise is generated by the duct vibration caused by compressor movement. For the flow induced noise, the static pressure field of refrigerant flow in the duct is vibrational source. In this paper, the compressor discharge duct noise considering two mechanisms was investigated. The refrigerant flow is solved using CFD and duct vibration and noise radiation are computed by FE-BE method.
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Ibarra-Bahena, Jonathan, Eduardo Venegas-Reyes, Yuridiana R. Galindo-Luna, Wilfrido Rivera, Rosenberg J. Romero, Antonio Rodríguez-Martínez i Ulises Dehesa-Carrasco. "Feasibility Analysis of a Membrane Desorber Powered by Thermal Solar Energy for Absorption Cooling Systems". Applied Sciences 10, nr 3 (7.02.2020): 1110. http://dx.doi.org/10.3390/app10031110.
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In absorption cooling systems, the desorber is a component that separates the refrigerant fluid from the liquid working mixture, most commonly completed by boiling separation; however, the operation temperature of boiling desorbers is generally higher than the low-enthalpy energy, such as solar, geothermal, or waste heat. In this study, we used a hydrophobic membrane desorber to separate water vapor from an aqueous LiBr solution. Influencing factors, such as the H2O/LiBr solution and cooling water temperatures, were tested and analyzed. With the experimental data, a solar collector system was simulated on a larger scale, considering a 1 m2 membrane. The membrane desorber evaluation shows that the desorption rate of water vapor increased as the LiBr solution temperature increased and the cooling water temperature decreased. Based on the experimental data from the membrane desorber/condenser, a theoretical heat load was calculated to size a solar system. Meteorological data from Emiliano Zapata in Mexico were considered. According to the numerical result, nine solar collectors with a total area of 37.4 m2 provide a solar fraction of 0.797. The membrane desorber/condenser coupled to the solar system can provide an average of 16.8 kg/day of refrigerant fluid that can be used to produce a cooling effect in an absorption refrigerant system.
Rozprawy doktorskie na temat "REFRIGERANT COUPLE"
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Ignatowicz, Monika. "Corrosion aspects in indirect systems with secondary refrigerants". Thesis, KTH, Tillämpad termodynamik och kylteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-65569.
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Aqueous solutions of organic or inorganic salts are used as secondary refrigerants in indirect refrigeration systems to transport and transfer heat. Water is known for its corrosive character and secondary refrigerants based on aqueous solutions have the same tendency. The least corrosive from the aqueous solutions are glycols and alcohols. Salt solutions, such as chlorides and potassium salts, are much more corrosive. Nevertheless, it is possible to minimize corrosion risks at the beginning stage while designing system. Proper design can significantly help in improving system performance against corrosion. There are several aspects which need to be taken into account while working with secondary refrigerants: design of system, selection of secondary refrigerant, proper corrosion inhibitors, compatible materials used to build the installation and proper preparation of system to operation. While choosing proper materials it is advised to avoid the formation of a galvanic couple to reduce the risk of the most dangerous type of corrosion. Oxygen present in installation is another important factor increasing the rate of corrosion. Even small amounts of oxygen can significantly affect the system lifetime. The methods of cleaning, charging the system with refrigerant, and deaeration procedures are extremely important. The purpose of this thesis work is to present the problems of corrosion occurring in the indirect systems with secondary refrigerants. The thesis describes the mechanism of corrosion and its different types, most commonly used materials in installation, different corrosion inhibitors used to protect system. This thesis also lists the available secondary refrigerants on the market and briefly describes them. Further, it describes the important aspects related with designing, preparing and maintaining of indirect systems. This thesis is giving some clues and shows what should be done in order to reduce risks of corrosion.Effsys 2 P2 project
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Fronk, Brian Matthew. "Modeling and Testing Of Water-Coupled Microchannel Gas Coolers for Natural Refrigerant Heat Pumps". Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16247.
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An experimental and analytical investigation on a water-coupled microchannel gas cooler was conducted in this study. With a relatively low critical temperature (31.1°C/89.9°F) and pressure (73.7 bar/1070 psi), CO2 is a supercritical fluid on the high side of a vapor compression cycle under warmer ambient conditions. This results in a non-isothermal heat rejection through the component known as the gas cooler. The large temperature glide in the heating of tap water matches well with the supercritical temperature glide of carbon dioxide. Unlike in a condensation process, here the non isothermal heat rejection can be used to advantage in a counterflow gas cooler, in which the water outlet temperature can rise to the desired high value. This minimizes temperature pinch and keeps gas cooler size economical. The focus of this thesis was to develop and experimentally validate a heat transfer model for a water-coupled microchannel gas cooler. The heat exchanger was tested in a small capacity experimental heat pump system. The heat pump system was designed to simulate conditions for heating domestic tap water to a usable temperature. A matrix of test points varying refrigerant inlet temperature, refrigerant mass flow rate, water inlet temperature and water volumetric flow rate were used to characterize the performance of the heat exchanger and validate the model.
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Appadoo, Dominique R. T. (Dominique Rupert Thierry) 1964. "Spectral simplification techniques for high resolution fourier transform spectroscopic studies". Monash University, School of Chemistry, 2002. http://arrow.monash.edu.au/hdl/1959.1/7746.
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Remigy, Jean-Christophe. "Etude de la miscibilite des lubrifiants frigorifiques compatibles avec les nouveaux refrigerants inertes vis a vis de la couche d'ozone. Optimisation d'une formulation". Caen, 1995. http://www.theses.fr/1995CAEN2049.
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La miscibilite des lubrifiants frigorifiques a base de polyolesters avec le hfc-134a (le principal substitut des refrigerants inertes vis a vis de la couche d'ozone, 1,1,1,2-tetrafluoroethane) est presente dans la premiere partie de cette these. L'influence de la structure chimique sur la miscibilite a ete etudiee. L'encombrement sterique des groupements esters est un facteur important de la miscibilite et un polyolester encombre ne sera pas miscible avec le hfc-134a. Un polyolester synthetise a partir d'un alcool donne et d'un acide a chaines ramifiees et courtes sera plus miscible que celui obtenu a partir d'un acide a chaine longue lineaire. La miscibilite a aussi ete etudiee a l'aide des parametres de solubilite de hansen. Une nouvelle methode de traitement des resultats experimentaux a permis de determiner les parametres et les volumes de solubilite (les volumes sont assimiles a des ellipsoides) du hfc-134a et de differents polyolesters. Nous avons montre que dans l'espace 3d de hansen, la distance d'interaction entre les centres des volumes de solubilite refletait la miscibilite du hfc-134a avec differents polyolesters. Pour ce refrigerant, nous avons determine la distance d'interaction critique au-dela de laquelle l'immiscibilite apparait. La seconde partie est consacree a l'influence de la structure chimique des polyolesters sur la viscosite et sur les proprietes tribologiques. Ces proprietes ont ete etudiees pour les contacts acier sur acier et aluminium sur acier. A partir des acquis, trois diagrammes ternaires ont ete etudies. Deux formulations optimisees ont ete testees, avec des compresseurs hermetiques
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Rerhrhaye, Amal. "Contribution à l'étude de divers couples frigorigènes : Application à la réfrigération solaire photothermique". Nancy 1, 1986. http://www.theses.fr/1986NAN10093.
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Détermination du profil annuel de l'irradiation globale dans plusieurs sites de climat aride, en vue de la production de froid. Étude des propriétés physico-chimiques de trois couples frigorigènes : CACL::(2)-NH::(3), BACL::(2)-NH::(3), MGCL::(2)-NH::(3). Détermination du couple le plus adapté à la production de froid dans les zones tropicales. Présentation des résultats expérimentaux du fonctionnement d'un réfrigérateur solaire photothermique de capacité de 380 L installé à Madagascar
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ANAND, SAURABH. "COMPARATIVE ANALYSIS OF THERMODYNAMICS PERFORMANCE OF CASCADE REFRIGERATION SYSTEM FOR REFRIGERANT COUPLE R23/R290 AND R23/R600A". Thesis, 2019. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16950.
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This study presents a comparative analysis of thermodynamic performance of cascade refrigeration systems (CRSs) for refrigerant couples R23/R290 and R23/R600A to discover whether R600A is a suitable substitute for R290. The discharge temperature, input power of the compressor, coefficient of performance (COP), exergy loss (X) and exergy efficiency (g) are chosen as the objective functions. The operating parameters considered in this thesis include condensing temperature, evaporating temperature in both high-temperature cycle i.e HTC and lower cycle i.e LTC and Temperature difference in the cascade heat exchanger. Under the same operation condition, the input power of R23/R600A CRS is lower than that of R23/R290 CRS, and COP opt is higher than that of R23/R290 CRS. The theoretical analysis indicates that R23/R600A is a more potential refrigerant couple than R23/R290 in Cascade Refrigeration System (CRS).
Części książek na temat "REFRIGERANT COUPLE"
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Tan, Hüsamettin, i Ali Erişen. "Exergy Analysis of Cascade Refrigeration System for Different Refrigerant Couples". W Springer Proceedings in Energy, 633–42. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-30171-1_68.
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Nhan Phan, Thanh. "A Review on Condensation Process of Refrigerants in Horizontal Microfin Tubes: A Typical Example". W Heat Transfer [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.105875.
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Heat transfer performance of refrigerant on the condensation process is very important in the designing of condensation equipment, especially in air conditioning and refrigeration systems. The outstanding advantages of microfin tubes are reducing the weight and size of condensers and also reducing the amount of refrigerant on the system. Reviewing the general concept of condensation and detailing the formation of flow pattern map that is also the procedure to determine heat transfer coefficient and pressure drop during condensation process of refrigerant inside the horizontal microfin tubes would be considered. Also, a typical example will be presented to illustrate a detailed procedure to calculate the value of heat transfer coefficient and pressure drop during the condensation process in horizontal microfin tubes. The data results show that microfin tube J60 with 60 number of fins inside 8.96 mm inner diameter, 0.2 mm height of fin, 40o of apex angle and 18o of helix angle, the condensation procedure of R1234ze at 35°C, heat flux of 8.62 kW/m2, and mass flux of 222 kg/m2s that could be estimated with heat transfer coefficient would be reduced from 8160.4 [W/m2 K] to 1413.8 [W/m2 K] follow with quality x changes from 0.99 to 0.01, and the maximum pressure drop of this process is 3173.8 [Pa/m].
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Ikeda, Hajime, Akinori Sakabe, Shingo Hamada, Mitsuhiro Shirota i Takashi Kobayashi. "Application of CFD to Prediction of Heat Exchanger Temperature and Indoor Airflow Control Simulation in Room Air Conditioner Development". W Computational Fluid Dynamics - Recent Advances, New Perspectives and Applications [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.110076.
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In the development of room air conditioners, repeated experiments are conducted to improve product performance. In experiments, temperatures, and air velocities, however, the number and locations of sensors that can be installed in experiments are limited, and it is difficult to estimate the background of a phenomenon based on experimental data alone. Therefore, in design practice, we utilize quantitative verification by CFD in addition to experimental analysis. In this chapter, we describe two CFD models. The first model is a heat exchanger model of an indoor unit that has a cross-flow fan and a heat exchanger. This model is coupled with CFD model and one-dimensional refrigerant flow circuit model. This calculates airflow velocity, temperature, refrigerant flow pressure, and enthalpy. The second model is an indoor airflow model of a room. The room air conditioner can control the temperature and the velocity distribution of airflow in a room, which influences user thermal comfort by controlling the direction, temperature, and volume of airflow by using the indoor unit outlet. This model can predict airflow velocity and temperature in a room.
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Wei, James. "Product Exploration and Discovery". W Product Engineering. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195159172.003.0005.
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It is sometimes said that “necessity is the mother of invention.” Many product innovations have begun with the observation and recognition that many people are in need of a new or improved product, and investigators then looked for a technology that would produce such a product to satisfy this market need. Investigators may examine current products to find what properties need improvement and whether these properties can be modified; for example, raw rubber is brittle when cold and is sticky when hot, whereas vulcanized rubber, which is used to make tires and gaskets, remains flexible whether hot or cold. Investigators may take the more ambitious approach of looking for materials that are not currently used for a particular product to see whether they have better properties to offer: for example, the use of ether as an anesthetic relieved the pain from surgery and childbirth that people were subjected to previously. The more ambitious investigator would attempt to create new synthetic materials to suit a particular market: Freon, a chlorofluorocarbon (CFC), was invented to make a safe refrigerant for home refrigerators. These are called the Market-Pull products, or market looking for a technology. Another frequent innovation path begins with a technology that is dormant or underutilized, followed by the search for new markets. When Freon was established as a safe refrigerant, it became the platform for new markets, such as air conditioning, aerosol propellants, and computer cleaning. Some technologies began as accidental discoveries when investigators were looking for something else, or were driven by curiosity. Penicillin is one of the best known examples of serendipity, of making unexpected discoveries. The most ambitious paths start from planned explorations to create a new technology, followed by the quest for a place in the market. Carothers created the field of synthetic condensation polymerization, and DuPont decided that this method could be used to make nylon fibers to replace silk stockings. These are called the Technology-Push products, or technology looking for a market.
Streszczenia konferencji na temat "REFRIGERANT COUPLE"
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Ernst, Timothy C., i Srinivas Garimella. "Wearable Engine-Driven Vapor-Compression Cooling System for Elevated Ambients". W ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43734.
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The development of a wearable cooling system for use in elevated temperature environments by military, fire-fighting, chemical-response, and other hazardous duty personnel is underway. Such a system is expected to reduce heat-related stresses, increasing productivity and allowable mission duration, reduce fatigue, and lead to a safer working environment. The cooling system consists of an engine-driven vapor compression system assembled in a backpack configuration, to be coupled with a cooling garment containing refrigerant lines worn in close proximity to the skin. A 2.0 L fuel tank powers a small-scale engine that runs a compressor modified from the original air compression application to the refrigerant compression application here. A centrifugal clutch and reduction gear train system was designed and fabricated to couple the engine output to the refrigerant compressor and heat rejection fan. The system measured 0.318×0.273×0.152 m and weighed 4.46 kg. Testing was conducted in a controlled environment to determine performance over a wide range of expected ambient temperatures (37.7–47.5°C), evaporator refrigerant temperatures (22.2–26.1°C), and engine speeds (10,500–13,300 RPM). Heat removal rates of up to 300 W, which is the cooling rate for maintaining comfort at an activity level comparable to moderate exercise, were demonstrated at a nominal ambient temperature of 43.3°C. The system consumes fuel at an average rate of 0.316 kg/hr to provide nominal cooling of 178 W for 5.7 hrs between refueling.
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Fan, Xiaowei, Fang Wang, Huifan Zheng, Xianping Zhang i Di Xu. "Behavior and Performance of Refrigerant Mixture HFC125/HC290 in Heat Pumps". W ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63552.
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The refrigerant mixtures provide an important direction in selecting new environment-friendly alternative to match the desirable properties with the existing halogenated refrigerants or future use in the new devices, in which, HFCs refrigerants with zero ODP combined with HCs refrigerants with zero ODP and lower GWP are of important value in the fields of application. In the present work, research on HFC125/HC290 (25/75 by mass) binary refrigerant mixture used in heat pumps was carried out, and parameters, factors affecting the performance were investigated, and compared with that of HCFC22 under the same operating conditions. It has been found that the new mixture can improve the actual COP by 2 to 13% and hence it can reduce the energy consumption by 20 to 31.5%. The overall performance has proved that the new refrigerant mixture could be a promising substitute for HCFC22.
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Antao, Dion Savio, i Bakhtier Farouk. "Numerical and Experimental Investigations of an Orifice Type Cryogenic Pulse Tube Refrigerator". W ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58530.
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A helium filled orifice type pulse tube refrigerator (OPTR) was designed, built and operated to provide cryogenic cooling. The OTPR is a travelling wave thermoacoustic refrigerator that operates on a modified reverse Stirling cycle. The experimental studies are carried out at various values of the mean pressure of helium (0.35 MPa – 2.2 MPa), amplitudes of pressure oscillations, frequencies of operation and sizes of orifice opening. The experimental results are compared with the predictions from a detailed time-dependent numerical model. In the CFD model, the compressible forms of the continuity, momentum and energy equations are solved for both the refrigerant gas (helium) and the porous media regions (the regenerator and the three heat-exchangers) in the OPTR. An improved representation of heat transfer in the porous media is achieved by employing a thermal non-equilibrium model to couple the gas and solid (porous media) energy equations. The model predictions show better comparisons with the experimental results when the effects of wall thicknesses of the various components of the OPTR are included in the model.
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Antao, Dion Savio, i Bakhtier Farouk. "Experimental and Numerical Characterization of an Orifice Type Cryogenic Pulse Tube Refrigerator". W ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65027.
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An orifice type pulse tube refrigerator (OPTR) was designed, built and operated to provide cryogenic cooling. The OTPR is a travelling wave thermoacoustic refrigerator that operates on a modified reverse Stirling cycle. We consider a system that is comprised of a pressure wave generator (a linear motor), an aftercooler heat-exchanger, a regenerator (comprising of a porous structure for energy separation), a pulse tube (in lieu of a displacer piston as found in Stirling refrigerators) with a cold and a warm heat-exchanger at its two ends, a needle-type orifice valve, an inertance tube and a buffer volume. The experimental characterization is done at various values of mean pressure of helium (∼ 0.35 MPa–2.2 MPa), amplitude of pressure oscillations, frequency of operation and size of orifice opening. A detailed time-dependent axisymmetric computational fluid dynamic (CFD) model of the OPTR is simulated to predict the performance of the OPTR. In the CFD model, the continuity, momentum and energy equations are solved for both the refrigerant gas (helium) and the porous media regions (the regenerator and the three heat-exchangers) in the OPTR. An accurate representation of heat transfer in the porous media is achieved by employing a thermal non-equilibrium model to couple the gas and solid (porous media) energy equations. In the future, a validated computational model can be used for system improvement and optimization.
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Escobar Nunez, Emerson, i Andreas A. Polycarpou. "Tribological Performance of Polymer Coatings in Carbon Dioxide Refrigerant Environment". W ASME/STLE 2009 International Joint Tribology Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/ijtc2009-15190.
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Natural refrigerants have gained significant interest due to environmental reasons. Among different natural refrigerants such as water, air, and ammonia, Carbon dioxide (CO2) is the main candidate to replace commonly used hydrofluorocarbon (HFC) refrigerants in air-conditioning compressors due to its environmental benefits. One of the main advantages of implementing CO2, from an environmental point of view, lies in its relative low global warming potential (GWP) which is three orders of magnitude lower than commonly used HFC refrigerants. Coupled with the new refrigerants is also the need to use some form of protective coatings on the tribopairs. In this study unlubricated (presence of CO2 refrigerant only) experiments were performed to evaluate the tribological performance of three different polymeric-based coatings deposited on Durabar G1 gray cast iron disks. Specifically, Fluorolon 325, Impreglon 1704 PEEK, and PEEK/Ceramic/ PTFE blends were tested against 52100 hardened steel pins. Results showed lower friction coefficient and wear in the Fluorolon 325 case compared to the Impreglon 1704 PEEK and PEEK/Ceramic/PTFE coatings. These results are comparable with earlier studies using PTFE-based coatings [1].
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Conte´, Ibrahima, Xiao-Feng Peng i Zhen Yang. "Numerical Investigations of Forced Convection From Rectangular Coiled Pipes". W 2007 First International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2007. http://dx.doi.org/10.1115/mnc2007-21136.
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Investigations are done to numerically study forced convective heat transfer from the flow inside a rectangular coiled pipe, as micro-scale heat exchange device with staggered arrangement, to the external flow around the pipe. The commercial CFD software Fluent 6.0 is used as the solver. The problems considered were three-dimensional laminar flow of the refrigerant R141B through the tube and turbulent air flow exterior to the tube. The studied coiled pipe was composed of four rows among which two rows were encompassed in a large rectangular coil and the other two were in an inner smaller rectangular coil. The results showed remarkable differences in the flow behavior and heat transfer for different rows of tubes. The secondary flow in the tubes bends of the larger rectangular coil is very weak compared to that of the inner rectangular coil. Better heat transfer process occurred through the tubes of the second row where the higher values of the fluid temperatures were observed in the pipe. The results showed the effects of the straight tubes inclination angle on the flow behavior in rectangular coiled pipes. The shape of the secondary flow is changed from a couple of vortices in the case of smaller angle (α = 9°) to a single vortex in the case of larger angle (α = 45°). The results also showed the rotation of the maximum axial velocity due to the increase in the straight tubes inclination angles. The results are in good agreement with previous numerical and experimental works on laminar flow in helical coil pipe.
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Holden, Nathan, i Norbert Mu¨ller. "Optimal Wheel Diameter Design for a Water-Vapor (R-718), Axial, Compressor". W ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-14039.
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There is an interest to phase out environmentally harmful refrigerants (ie: HCFC-12, HCFC-22, but also HCFC-134A and other). Theoretical analysis coupled with mostly European research has proven that water-vapor (R-718) technology can be comparable to and even more efficient than other modern chiller technology using conventional refrigerants. The crucial component to succeed with water-vapor as refrigerant is the compressor. European compressor designs already introduced and commercialized have shown that with the currently available mechanics of using water-vapor, energy consumption can be reduced by as much as 20% over conventional technology utilizing refrigerants like HCFC134A. However, currently these compressor designs are physically large and the chillers can be as much as five (5) times more expensive to manufacture and install. Often for this reason they are often deemed to be insufficient. Much more reasonably priced compressors of possibly smaller size are desired now to developed water-vapor into an economically viable refrigerant, that may also be applicable for smaller cooling capacities. The presented work looks at the preliminary design considerations to determine the minimum impeller-wheel diameter with respect to the pre-determined operating parameters (ie: limiting relative critical Mach number, rotational speed, total fluid temperature, total fluid density, etc....). The results need then to be further refined in subsequent steps leading to a final design not discussed here. With the preliminary optimal impeller-wheel diameter of a water-vapor (R-718) compressor as established here, industry can easily perform a critical first step in developing a workable water-vapor (R-718) refrigeration system.
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Jiang, Yirong, i Srinivas Garimella. "Compact Air-Coupled and Hydronically Coupled Microchannel Heat Pumps". W ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/aes-23628.
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Abstract Novel air-coupled and hydronically coupled heat pumps using microchannel components were investigated in this study. The air-coupled system uses microchannel tube, multilouver fin heat exchangers as the evaporator and condenser. In the hydronically coupled heat pump, refrigerant in the evaporator as well as the condenser transfers heat to an intermediate fluid such as an ethyleneglycol solution. The glycol loops are connected to the indoor/outdoor air through liquid-air heat exchangers. Models to simulate cycle thermodynamics, and single- and two-phase heat transfer in the components were developed to design these systems for cooling and heating mode operation. The components were optimized to develop the most compact systems that would satisfy system performance requirements. These systems were also compared with a conventional round-tube, plate-fin heat pump, which was designed using a commercially available simulation tool. Results from this study show that indoor and outdoor units of air-coupled microchannel systems can be packaged in only one-half and one-third the space required for a conventional system. Even more compact refrigerant heat exchangers are required in the hydronically coupled system, because of the high heat transfer coefficients for these liquid-coupled heat exchangers, and the counterflow orientation. The hydronic coupling offers flexibility in system location, and is well suited for integrated space-conditioning and water heating systems. Both air-coupled and hydronically coupled systems result in significant reductions in refrigerant inventories compared to round-tube systems. The refrigerant charge of the microchannel air-coupled system is 20% less than that of the round-tube heat pump. For the hydronically coupled system, the refrigerant charge is only 10% of the charge in the round-tube heat pump.
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Kilicarslan, Ali, i Norbert Mu¨ller. "Irreversibility Analysis of a Vapor Compression Cascade Refrigeration Cycle". W ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66363.
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Hydrocarbon based energy sources such as coal, oil and natural gas have been diminishing in an increasing speed. Instead of finding alternative energy sources, we have to use the available sources more effectively. By means of the irreversibility analysis, we can determine the factors or conditions that cause the inefficiencies in any energy system. In this study, irreversibility analysis of a compression cascade refrigeration cycle that consists of a high and low temperature cycles is presented. In the high temperature cycle, the refrigerants from different classes, namely R12 (CFC), R22 (HCFC), R134a (HFC) and R404a (Azeotropic) are selected as working fluids. In the low temperature cycle, R13 is only used as a working fluid. Irreversibility analysis of refrigerant pairs, namely R12-R13, R22-R13, R134a-R13, and R404a-R13 are carried out in a compression cascade refrigeration cycle by a computer code developed. The effects of evaporator temperature, condenser temperature, and the temperature difference between the saturation temperatures of the lower and higher temperature cycles in the heat exchanger (ΔT) and the polytropic efficiency on irreversibility of the system are investigated. The irreversibility of the cascade refrigeration cycle decreases as the evaporator temperature and polytropic efficiency increase for all of the refrigerant couples considered while the irreversibility increases with the increasing values of the condenser temperature and ΔT. In the whole ranges of evaporator temperature (−65°C / −45°C), condenser temperature (30–50°C), ΔT (2–16K) and polytropic efficiency (%50/%100), the refrigerant pair R12-R13 has the lowest values of irreversibilities while the pair R404a-R13 has the highest ones. At the lower condenser temperature (<30°C) and higher polytropic efficiencies (85%–95%), the refrigerant couples except for R404a-R13 have approximately the same values of irreversibility.
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Khan, Muhammad Saad, Sambhaji T. Kadam, Alexios-Spyridon Kyriakides, Ibrahim Hassan, Athanasios I. Papadopoulos, Mohammad Azizur Rahman i Panos Seferlis. "Comparative Analysis of Coefficient of Performance (COP) Correlations of Single-Effect Vapor Absorption Refrigeration (VAR) Cycle". W ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-93943.
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Abstract Most of the absorbent-refrigerant pairings are evaluated considering single-effect vapour absorption refrigeration (VAR) cycle. The coefficient of performance (COP) based modelling of VAR enables its quick performance evaluation. The development of efficient and environmentally benign fluid pairing is required to replace conventional refrigerants. Operating parameters-based COP models are scarce for single-effect VAR systems, and fewer correlations are available for the COP estimation. The paper compares five performance-based models reported in the literature for operating absorption cooling systems with various refrigerant and absorbent pairing. The comprehensive mean absolute percentage error (MAPE) analysis was performed for five reported correlations for more than 1601 data points of different fluid pairings. Results revealed that RMSD and MAPE values seem significantly higher for the reported correlations apart from the recently developed COP correlation accounted for fluid parameters in prediction. This indicates that the earlier reported correlations only accounted for the specific fluid pairing and could not incorporate different fluid pairing, which has been considered a recently reported correlation that resulted in the significantly improved prediction ability for COP. The finding from this study highlighted that the newly registered COP prediction correlation could be beneficial for developing new single-effect VAR cycles as it accounted for both the operating parameters and fluid parameters.
Raporty organizacyjne na temat "REFRIGERANT COUPLE"
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Kedzierski, Mark A., i Donggyu Kang. Horizontal convective boiling of R1234yf, R134a, and R450A within a micro-fin tube :. Gaithersburg, MD: National Institute of Standards and Technology (U.S.), sierpień 2017. http://dx.doi.org/10.6028/nist.tn.1966.
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This report presents local convective boiling heat transfer and Fanning friction factor measurements in a micro-fin tube for R134a and two possible low global warming potential (GWP) refrigerant replacements for R134a: R1234yf and R450A. Test section heating was achieved with water in either counterflow or in parallel flow with the test refrigerant to provide for a range of heat fluxes for each thermodynamic quality. An existing correlation from the literature for single and multi-component mixtures was shown to not satisfactorily predict the convective boiling measurements for flow qualities greater than 40 %. Accordingly, a new correlation was developed specifically for the test fluids of this study so that a fair comparison of the heat transfer performance of the low GWP refrigerants to that of R134a could be made. The new correlation was used to compare the heat transfer coefficient of the three test fluids at the same heat flux, saturated refrigerant temperature, and refrigerant mass flux. The resulting example comparison, for the same operating conditions, showed that the heat transfer coefficient of the multi-component R450A and the single-component R1234yf were, on average, 15 % less and 5 % less, respectively, than that of the single-component R134a. Friction factor measurements were also compared to predictions from an existing correlation. A new correlation for the friction factor was developed to provide a more accurate prediction. The measurements and the new models are important for the evaluation of potential low-GWP refrigerants replacements for R134a.
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Johra, Hicham. Performance overview of caloric heat pumps: magnetocaloric, elastocaloric, electrocaloric and barocaloric systems. Department of the Built Environment, Aalborg University, styczeń 2022. http://dx.doi.org/10.54337/aau467469997.
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Heat pumps are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water production. Conventional heat pumps are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The heat pump market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional heat pumps can have a large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression heat pump technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining large attention. These caloric effects are characterized by a phase transition varying entropy in the material, resulting in a large adiabatic temperature change. This phase transition is induced by a variation of a specific external field applied to the solid refrigerant. Therefore, the magnetocaloric, elastocaloric, electrocaloric and barocaloric effects are adiabatic temperature changes in specific materials when varying the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. Heat pump cycle can be built from these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not a mature technology yet, some of these caloric systems are well suited to become new efficient and sustainable solutions for indoor space conditioning and domestic hot water production. This technical report (and the paper to which this report is supplementary materials) aims to raise awareness in the building community about these innovative caloric systems. It sheds some light on the recent progress in that field and compares the performance of caloric systems with that of conventional vapour-compression heat pumps for building applications.