Vapor Compression Refrigeration System

The growing demand for affordable and eco-friendly cooling systems has encouraged the development of hybrid
technologies. This study presents the design and fabrication of an air cooler that integrates vapor compression
refrigeration (VCR) principles with copper tubing and refrigerant gas (R134a). The system enhances heat
exchange using high-thermal-conductivity copper coils and optimizes air cooling with a fan-assisted
mechanism. Results indicate improved cooling efficiency and reduced electricity consumption, making it a
viable alternative to traditional air conditioning, especially in resource-constrained settings.

This study investigates the performance enhancement and energy savings of domestic refrigeration systems by utilizing a hybrid nanolubricant composed of Al 2 O 3 /ZrO 2 nanoparticles dispersed in Polyalkylene Glycol (PAG) oil. The primary aim is to improve the energy efficiency and overall performance of cooling systems. The research focuses on reducing compressor power consumption and enhancing the evaporator's heat absorption rate. The R600a refrigerant, an environmentally friendly and ozone-safe fluid, was used in the refrigeration system with varying concentrations of Al 2 O 3 /ZrO 2 hybrid nanolubricants (0.2, 0.4, and 0.6 g/L) at 70 g of refrigerant. The key performance metrics analyzed include compressor power consumption, refrigeration effect, and Coefficient of Performance (COP). Results show that, compared to a system without nanolubricant, the hybrid nanolubricant led to a 5.94% increase in cooling capacity, a 28.35% reduction in compressor power consumption, and a 46.2% improvement in COP (from 3 to 4.05). The nanoparticles were dispersed using ultrasonication and magnetic stirring techniques. Performance tests revealed significant enhancements in cooling capacity, thermal efficiency, and energy consumption, demonstrating that the Al 2 O 3 /ZrO 2 hybrid nanolubricant is a promising solution for improving the efficiency of home cooling systems.

In a domestic refrigerator with 4.49cc displacement compressors, the performance of R290 (48 by mass percent) and R600a (52 by mass percent) was examined experimentally. In our research, we employed a 210-litre refrigerator that was designed to run on R12 and had a longer capillary. The amount of energy utilised, as well as the pressure and temperature at crucial locations on the various refrigerated compartments and refrigerator circuit, are all monitored. With R290/R600a, we performed a scroll-down test and ice-making test. According to our findings, R290/R600a is the best contenders for replacing R134a in terms of energy conservation. Because the amount of refrigerant utilised is so small, the flammability factor can be overlooked.

The study of the expansion device in simple vapor compression refrigeration system is necessary in order to understand the parameters which can enhance the overall performance of system. It is essential to study the effect of capillary tube geometry on the performance of refrigeration systems. The literature review focuses on the effect that geometrical parameters like capillary tube length, bore diameter, coil pitch, number of twist and twisted angle have on the pressure drop, coefficient of performance (COP) and mass flow rate of the system. The parameters stated above can be further optimized in order to enhance the performance of the refrigeration system. The present work is focused on the influence of tube diameter, tube length, coil pitch, and inlet condition on mass flow rate of refrigerant through helical coil capillary tube and also on investigation about the Coefficient of Performance (COP) of the system due to coiling effect of capillary tube. The use of helical capillary...

In this study, energy and exergy analysis was performed for a refrigerator display cabinet (RDC) unit equipped with a variable speed DC-compressor and electronic expansion valve. Economic impact and energy saving were also investigated. Two identical refrigeration systems were built and tested experimentally to find the most efficient and feasible one. The first system was built using the existing commercial way of building up the refrigeration cycle of the RDC unit using an on/off switch for the compressor, and mechanical traditional thermal expansion valve (TEV). The other system was equipped with a variable refrigerant flow (VRF) DC-compressor, with inverter and electronic expansion valve (EEV) instead of the mechanical expansion valve. Complete specifications of each component and measurement devices used in this work are included in this study. It was found that the new RDC unit equipped with the VRF system provided 32% energy saving, and less exergy destruction than the commercial cabinet. So, the use of the new suggested RDC units will reduce the energy bill of such sector by 32%.

This paper reviews on the possibilities of researches in the field of exergy analysis in various usable sectors where vapor compression refrigeration systems are used. Here, it is found that exergy depends on evaporating temperature, condensing temperature, sub-cooling and compressor pressure. It also depends on environmental temperature. Nowadays, hydrocarbons are considered as refrigerant having low ODP and GWP, and these are considerable in the aspect of exergy analysis. Refrigerants R 407a, R 600a, R 410a and R 134a are considered and analyzed with respect to exergy efficiency. Mixtures of hydrocarbons with R134a also show better performance with respect to other refrigerants. Among the components of the vapor compression system, much research showed that major part of exergy losses is occurred in the compressor. Nanofluid and nanolubricant cause to reduce the exergy losses in the compressor indirectly.

Vapor compression cooling systems are the most used and most efficient cooling method in industrial and commercial applications. The reason of these systems are preferred is that they reduce environmental impacts, provide energy efficiency and have economic advantages. In this article, the effects of superheating and subcooling on the system performance in the vapor compression refrigeration cycle (VCRS) using R507A were theoretically examined. The thermodynamic data used the calculation were taken from the Coolpack program. The performance analysis of the VCRS were made for different operating conditions. In the analyses, the evaporator temperature was changed between -5 and -25 oC, the condenser temperature was changed between 25 and 45 oC, and the superheat and subcooling temperatures were changed as 0, 3, 5 and 7 oC. In the analysis made depending on the change in evaporator temperature, superheat and subcooling temperatures, the highest COP value of the cycle is 3.71. In the analysis made depending on the change in condenser temperature, superheat and subcooling temperatures, the highest COP value of the cycle was found to be 4.367.

This work presents a Modelica library aimed to simulate vapor compression systems at both steady and transient conditions. The simulation of these specific systems is particularly challenging from both the phenomena and the numerical resolution point of views. The main goal of the library is to provide, not only accuracy and robustness, but also very low computational time. It is worth mentioning that, although the baseline version of the library is currently operative, its development continues in order to improve or add new features.Most of the components developed for the library are simulated by means of look-up tables or efficiency curves for the sake of quickness. The main efforts were focused on two critical aspects of the system. On the one hand, heat exchanger models were developed based on a switching moving boundary approach in order to have a relatively high ratio between accuracy and resolution time. This method takes into account the distribution of phases along heat e...

A major use of refrigeration is in the preservation, storage and distribution of perishable foods. Cold room is refrigerated space where low temperatures maintain for preservation of Food. The demand of cold room is going to increases due to adverse climatic conditions over worldwide so it needs to develop a cold chain which includes harvest cooling (pre-cooling) cold room transport to market. This design of cold storage is adaptive design which is operated on evaporative cooling suitable for preservation of the vegetables and fruit. The cold room is designed with refrigeration capacity 1.15 TR. During design these system various design parameter like cooling load calculation, selection of compressor, thermostatic expansion valve, condenser capacity and piping design are considered.

A household refrigerator is a necessary piece of equipment for humans. Almost no house exists without a refrigerator. Air conditioning and refrigeration account for between 30 and 35 percent of total energy use. The researchers are always trying to build an energy-efficient cooling system and increase cooling capacity. Nano technological goods, methods, and applications contribute to environmental and climate conservation by conserving raw materials, energy, and water, as well as lowering greenhouse gas emissions and hazardous waste. The use of nanoparticles in small amount in vapor compression refrigeration system aided in improving system performance and reduced energy consumption. This paper  presents the energy consumption & thermal performance of domestic refrigerator using  CuO/POE Oil and Cu/POE oil nanofluids with 0.1%, 0.2 to 0.3% wt. concentration in hermetically sealed compressor of the system used in a residential refrigerator  From the results it is found that compression works get reduced, cooling capacity & COPs of the systems get increased.

This paper provides a clear and concise understanding of the principles and applications of HVACR using a rigorous, yet, easy to follow presentation. The coverage is broad, including relevant support areas such as fluid mechanics, heat transfer, thermodynamics, psychrometrics, with specific applications to HVACR design and calculations, and main topics such as air conditioning processes, cooling / heating load calculations, refrigeration cycles, and HVACR equipment and systems. The book integrates and illustrates the use of data and information from ASHRAE Handbooks and Standards in step-by-step calculations of cooling and heating loads and other aspects of HVACR. Elucidation of the principles is further reinforced by examples and practice problems with detailed solutions. Firmly grounded in the fundamentals, the book maximizes readers’ capacity to take on new problems and challenges in the field of HVACR with confidence and conviction. Providing a ready reference and review of essential principles and their applications in HVACR, the book is ideal for HVACR practitioners, undergraduate engineering students, and those specializing in HVACR, as well as for practicing engineers preparing for the engineering license exams (FE and PE) in USA and abroad. The book uses both Inch-Pound (I-P) and S I systems of units to facilitate global readership and use.
Covers support areas of fluid mechanics, heat transfer, thermodynamics, and psychrometrics with HVACR applications
Covers HVACR principles and applications using many problems and solutions illustrating the use of ASHRAE Handbooks
Usage of both I P (inch-pound) and S I units to facilitate global readership and usage

This paper is devoted primarily to thermodynamic analysis of cycles implemented in three low-capacity pilot plants for liquefaction of natural gas (in Moscow, St. Petersburg, and Yekaterinburg). In our opinion, results of the research conducted will undoubtedly be defined more precisely in possible replication of small-capacity plants, or the creation of new ones. The problem of producing liquefied natural gas (LNG) in Russia has existed for some time: as early as the outset of the 1980s, the design and construction of a large-scale liquefaction complex was begun by the collective Scientific-Production Association Kriogemash on the initiative of the general contractor for cryogenic engineering, member-correspondent of the Academy of Sciences of the USSR V. P. Belyakov. These operations had ceased with the breakup of the USSR. Today, foreign companies are constructing on Sakhalin Island the heavy-duty liquefaction complex Sakhalin-2 with a capacity of the order of several hundred tons of LNG per hour, which will basically provide for export demands. As for internal demands for LNG, it must be remembered that a branching pipeline system for the distribution of natural gas containing a significant portion of methane (CH 4), which attains 95-98%, is being built and is functioning within the Russian landmass. Since LNG is used as a fuel for all types of transport, including aviation, and is extremely promising, LNG production is actually limited in a number of cases by small truck gas-filling compression stations (TGFCS) and gas-distribution stations (GDS), which have a heavy-duty, and at the present time, incompletely loaded compressor base. Today, there are three low-capacity (up to 1000 kg/h) "pilot" liquefaction plants in St. Petersburg, Moscow, and Ekaterinburg. They are built in accordance with two designs: with a simple throttle cycle, and with a rather complex throttle-ejector cycle; and, preliminary chilling at a level of 238 K is utilized in both designs. The degree of thermodynamic improvement in the liquefaction of methane (the ratio of the minimum required energy for liquefaction to that actually expended) for these plants does not exceed 0.3 (i.e., 30%). To improve the efficiency of the plants (or demonstrate the need to search for new solutions), it is necessary to determine the feasibility of reducing energy losses, which is of particular import, since it should be considered that replication of small liquefaction systems not only in our country, but also in many others is inevitable with expanding use of LNG in all types of transport. The probability of this situation is rather high: it is substantiated by a large amount of experience acquired in the fields of transportation, storage, and utilization of other cryogenic liquids such as oxygen, nitrogen, and hydrogen on the one hand, and by expanding pipeline export of natural gas to Europe on the other.

A study was carried out to investigate the performance and effect of Earth Heat Exchangers (Heat Pipe), Peltier Module with and without combination with vapour compression air conditioning system with return air. The results show that the coefficient of performance of the system can be improved and the energy required by the compressor can be reduced when Peltier Module and Earth Heat Exchanger is used before cooling coil and provide supplementary cooling air to evaporator coil.In the present age with depleting sources of energy there will be minimum electric power consumption in operation of the air conditioning units so thatthere is always a target to get the best energy ratios. Individually the ideas like Earth heat exchanger cooling; Peltier Module(thermoelectric cooling) did not stand good but by combination of two or more concepts in a collaborative manner stands a possibility to develop an energy efficient method of air conditioning. By adopting proper design of Earth heat ex...

The research and development work carried out by different researchers on development of novel thermoelectric R&AC system has been thoroughly reviewed in this paper. In recent years, with the increase awareness towards environmental degradation due to the production, use and disposal of ChloroFluoro Carbons (CFCs) and Hydro Chlorofluorocarbons (HCFCs) as heat carrier fluids in conventional refrigeration and air conditioning systems has become a subject of great concern and resulted in extensive research into development of novel refrigeration and space conditioning technologies. Thermoelectric cooling provides a promising alternative R&AC technology due to their distinct advantages. Use of Thermoelectric effect to increase the COP of existing cooling system has been also reviewed

This paper presents a methodology for using a general-purpose spreadsheet application, which is Microsoft Excel, as an effective modelling platform for multi-objective optimisation analyses of vapour-compression refrigeration (VCR) systems. Since Excel itself does not provide functions for determining the thermodynamic properties of the refrigerants, the VBA programming language that comes with Microsoft applications has been used for developing such functions for various conventional and alternative refrigerants. The other limitation of Excel regarding the intended purpose is that the solver that comes with it (Frontline's Solver) is not suitable for multiobjective analyses. Fortunately, the developers of the MIDACO solver have made a limited version of this multi-objective solver available for Excel users for free. The paper demonstrates the capability of Excel with these additional capabilities for exergetic, economic, and environmental (3E) analyses of VCR systems by considering a simple system with the environment-friendly R-152a as the refrigerant.

The principal of refrigeration is method of successful storage of vegetable and fruits to maintain their flavour and freshness, for post harvest product deterioration start with time and temperature so it need to be maintain desirable temperature and relative humidity for post harvest product that is for potato. A cold storage design at village HARSODAN district Ujjain (m.p.) to give better facility for potato storage. This paper deal with all standard refrigeration principles and different aspect of design of cold storage and this design is hypothetically intended to serve as a guide for future fabrication and erection. .

Most of the household refrigerators work on the Vapor compression refrigeration system which has high coefficient of performance. The system consists of components like compressor, condenser, expansion valve and evaporator. The system performance depends on the performance of all the components of the system. The main objective of the paper is to find coefficient of performance of refrigeration system using conventional condenser (MS with Cu coating) and then verifying effect of performance using conventional condenser made of copper material on Kelvinator refrigerator of refrigeration capacity 165 lts, hermitic sealed compressor unit with R134a as refrigerant. Further an attempt is made in modifying the conventional shaped condenser to spiral shaped condenser and with varying pitch the performance of system is evaluated. Finally it is noticed that spiral shaped condenser has given the maximum COP among all observations.

Due to ecological problems like Ozone depletion and Global warming certain refrigerants like R-22 have to be replaced. HCFC's (Hydro Chloro fluoro carbon) have been identified as the prime foremost cause of Ozone depletion. Driven by 1992 amendment to the Montreal-Protocol that calls for the phase out of HCFC's. HFC's (Hydro fluoro carbon) are substantially less damaging to the Ozone layer than HCFC's. Several refrigerants have emerged as substitutes to replace R-22, the most widely used Fluoro carbon refrigerant in the world. These include the environmentally friendly hydro carbon refrigerants such as R134a, R410A, R407A and R407C. In this present work problem of R-22 phase out in air conditioning application is addressed. The main objective of the project is Performance analysis of an window air conditioning system by using three refrigerants like R-22, R407C and R410A with different capillary pitches. In view of this it is proposed to carry out a number of experim...

This work presents the computer aided comparative analysis of the effects of subcooling and superheating on the performance of R134a and R717 in simple vapour compression refrigeration systems. The analysis was done by carrying out a comprehensive study of the simple vapour compression refrigeration systems, determining the subcooling and superheating parameters by calculation and developing a computer program for the analysis and results generation. The results obtained show that superheating is not an ideal way of improving performance with R717 as the COP reduces with increasing superheat temperature, rather subcooling the refrigerant gives an improvement in the COP of the system. On the other hand, both subcooling and superheating refrigerant R134a improve the performance of the system as the COP increases with the subcooling and superheating temperatures. These were presented graphically using the MATLAB programming language. The program developed for this study can also be used for examination purposes to reduce the work load for the lecturer and to also ensure accuracy of results.

Allowing the condensing pressure of direc;t expansion refrigeration equipment to float (vary freely) with ambient temperature can lead to substantial energy savings. This paper presems experimental results of the perfonnance of thermostatic expansion valves (TEV) under a range of condensing pressures. system loads and inlet quality. A theory is developed to exp!aTn the performance of the valves under these conditions. It is concluded that condensing pressures can be allowed to vary freely across a wide range of conditions provided that the TEV is correctly siz.ed and that an envelope of safe operating conditions is defined to ensure satisfactory perform:.tnce at all times.

The European limitations associated with the use of fluorinated refrigerants have affected one of the most extended solutions used in commercial refrigeration in warm countries. Traditional cascade systems with R404A or R134a, in the high-temperature cycle, and R744 (CO 2), in the low side, will be prohibited from 2022 onwards unless the refrigerants used have a GWP 100 lower than 150. Since practically all the available refrigerants with low-GWP 100 are flammable, a simple but effective modification can be adopted upgrading the current direct expansion system to an indirect one. Accordingly, the aim of this work is to determine the energy and environmental impact of converting an R134a/CO 2 direct expansion cascade to an indirect one using the low-GWP 100 refrigerants R152a, R1234ze(E), R290 and R1270. The experimental analysis is performed at three different heat rejection temperatures (from 23.3 to 43.6 ºC), maintaining the cooling service product at temperatures of 2ºC and-20ºC on average.

In this study, energy and exergy analysis was performed for a refrigerator display cabinet (RDC) unit equipped with a variable speed DC-compressor and electronic expansion valve. Economic impact and energy saving were also investigated. Two identical refrigeration systems were built and tested experimentally to find the most efficient and feasible one. The first system was built using the existing commercial way of building up the refrigeration cycle of the RDC unit using an on/off switch for the compressor, and mechanical traditional thermal expansion valve (TEV). The other system was equipped with a variable refrigerant flow (VRF) DC-compressor, with inverter and electronic expansion valve (EEV) instead of the mechanical expansion valve. Complete specifications of each component and measurement devices used in this work are included in this study. It was found that the new RDC unit equipped with the VRF system provided 32% energy saving, and less exergy destruction than the commercial cabinet. So, the use of the new suggested RDC units will reduce the energy bill of such sector by 32%.

The current focus on vehicle efficiency requires that components and systems are designed with the focus on entire vehicle energy management. Therefore, the impact of air conditioning (A/C) system design on overall vehicle energy management must be considered, especially as government regulations evolve to include driving cycles with air conditioning systems turned on within the overall calculation of vehicle fuel economy. Within the A/C system design process, it is necessary to weigh the trade-offs between system performance and energy consumption. This is especially true in hybrid or electric vehicles, where the A/C system design and its control algorithms may significantly affect "battery only" driving range, and where the A/C circuit may be used to cool batteries or electrical components. To study these trade-offs in a cost effective and efficient manner, it is necessary to use a system simulation tool. This paper presents a methodology for studying the trade-offs between cabin comfort, energy consumption, and battery cooling using GT-SUITE simulation software. This methodology was used to study the impact of various A/C system configurations for a Land Rover vehicle. Various compressors, evaporator configurations and battery cooling options were assessed to determine their impact on cooling performance and energy consumption. The modeling of one A/C system configuration will be presented, where the possibility to easily extrapolate to many different A/C configurations can be observed. The analyzed A/C system consists of electrically driven compressor, evaporator, internal heat exchanger, condenser, thermal expansion valve and battery cooler. Systems included in the simulation are the A/C refrigerant circuit with battery cooling, underhood airflow and vehicle cabin. The system model was run and validated at different steady-state conditions. Subsequently, the system was investigated to observe pulldown characteristics inside vehicle cabin at 43˚C ambient temperature.

The Vapor Compression Cycle (VCC) is the fundamental thermodynamic principle behind most Heating, Ventilation, Air Conditioning and Refrigeration (HVACR) systems. HVACR systems account for a vast majority of the energy used in residential and commercial buildings. There is a growing need to make these VCC DEDICATION This work is dedicated to my parents; Francois and Berthe Youmsi Mogtomo, to my siblings, Boris, Ariane and Pierre-Francois, and to all my friends and teachers. v ACKNOWLEDGEMENTS I would like to thank my thesis adviser, Dr. Bryan Rasmussen for his teaching, guidance, financial and moral support over the course of this research work. I would also like to thank the members of my committee Dr. Jerald Caton and Dr. Perla Balbuena for all that they taught me and for serving on my thesis committee.

The aim of this study was to develop a mathematical model with lumped parameters to investigate the energetic parameters of the heat pump with an internal heat exchanger (IHX). The developed mathematical model is validated with 25 tests using R134a as a working fluid. The results show that the maximum prediction error between the modeled and experimental results for the COP is 7.06%. The main objective of this paper was to investigate the COP value of a heat pump as a function of the efficiency of the internal heat exchanger and present a new equation to calculate the COP value. When the efficiency of IHX was increased from 0.65 to 0.95, the COP value increased by 5.41% under the conditions of minimum evaporation − 20 °C and maximum condensation temperature 90 °C. Keywords Heat pump • Efficiency • IHX • COP List of symbols A Heat transfer area (m 2) C Characteristic constant of the TEV valve (-) Cp Specific heat at constant pressure (J kg −1 K −1) COP Coefficient of performance (-) D Diameter (m) h Enthalpy (J kg −1) Nu Nusselt number (-) m Mass flow rate (kg s −1) P Compressor power (kW) Pr Prandtl number (-) Rc Capacity ratio (-) Re Reynolds number (-) Q Heat transfer rate (kW) T Temperature (K) U Overall heat transfer coefficient (W m −2 K −1) Greek symbols α Heat transfer coefficient (W m −2 K −1) η Compressor efficiency (-) λ Thermal conductivity (W m −1 K −1) ρ Density (kg m −3) ε Efficiency of the IHX (-) Subscripts r Refrigerant c Condenser o Evaporator liq Liquid phase vap Vapor phase cw Cooling water hw Hot water in Inlet out Outlet * Róbert Sánta

Performance enhancement and exergy destruction analyses were conducted numerically for vapor-compression refrigeration systems using R22, R134a, R410A, and R717. The first law of thermodynamics combined with finite-temperature-difference heat transfer theory and the second law of thermodynamics were applied to calculate the COP, heat-exchanger area, irreversibility, and friction loss that occurs in heat exchangers used in this system at various condensation and evaporation temperatures. The effects of cooling water in a subcooler, refrigerant pressure drop among heat exchangers, and superheating in an evaporator were also considered. Two dimensionless parameters, which represented initial cost saving and the total exergy destruction of the system, were introduced and evaluated to obtain the optimal degree of subcooling. Compared with evaporation temperature, condensation temperature plays a considerably more crucial role in determining the optimal degree of subcooling for achieving maximal initial cost saving. In addition, the optimal degrees of subcooling obtained according to the second law of thermodynamics were consistently higher than those obtained according to the first law of thermodynamics.

Modern air-conditioners incorporate variable-speed compressors and variable-opening expansion valves as the actuators for improving cooling performance and energy efficiency. These actuators have to be properly feedback-controlled; otherwise the systems may exhibit even poorer performance than the conventional machines which use fixed-speed compressors and mechanical expansion valves. Particularly for an air-conditioner with multiple evaporators, there are occasions that the machine is operated in a mode that only selected evaporator(s) is(are) turned on, and switching(s) between modes occurs(occur) during the control process. In this case, one needs to have more carefully designed control and switching strategies to ensure the system performance. In this paper, a framework for mode switching control of the dual-evaporator airconditioning (DEAC) system is proposed. The framework is basically an integration of a controller and a dynamic compensator. The controller, which possesses the flow-distribution capability and assumes both evaporators are on throughout the control process, is intended to provide nominal performance. While mode switching is achieved by varying the reference settings in the controller, the dynamic compensator is used to improve the transient responses immediately after the switching. Experiments indicate that the proposed framework can achieve satisfactory indoor temperature regulation and provide bumpless switching between different modes of operation.

The use of heat pumps is increasing worldwide, and knowledge of their properties is becoming more and more important. Although numerous tests regarding heat pumps have been performed, due to the large number of influencing variables, the entire range of input parameters is not covered, and there is no overall picture regarding the range of the coefficient of performance (COP) of heat pumps and their output parameters. This study extends existing research and provides a much more detailed comparison of results for the application of R1234yf and R1234ze(E) refrigerants, including the pressure drop across the evaporator, condenser, and internal heat exchanger (IHX). The appropriate mathematical model for the selected components was defined and verified experimentally. A total of 60 series of measurements were performed at different evaporating and condensing temperatures. The deviation of the numerical simulation results from the experimentally determined results was up to 7.4% for coo...

Refrigeration systems find applications in many stationary and mobile applications to provide an appropriate environment for food preservation and other temperature/ humidity sensitive items. These systems consume a large amount of energy leading to global warming. A variety of refrigerants are there, which are used in vapour compression refrigeration system. R134a has a higher global warming potential as compare to R134a and HC mixture. The various flow aspects of the capillary tube were investigated by a number of researchers in the past. In the present article, a review of various refrigerants presently used in the vapour compression refrigeration system and their performance have been analyzed and compared.

OPTIMIZATION OF THE REFRIGERATION MACHINERY WITH ONE STAGE OF COMPRESSION USING R152a Dumitru Aradau and Liviu Costiuc Department of Mechanical Engineering University "Dunarea de Jos" of Galati ROMANIA A method of the exergetic optimization of the refrigerating machinery with one stage of compression using R152a and reciprocating compressor, starting from the indicated diagram of compressor, is set in this paper. Also some practical relations for the calculation of the exergetic efficiency that brings in evidence the influence of the real reciprocating compressor and the nature of the working refrigerating agent, are set in this work. l.Introduction. The meetings of specialized commissions of the I.I.R. at London ( 1990), at Copenhagen, Ghent ( 1992) and Hanovra (1994) have brought significant changes for the Montreal Protocol (1987) regarding the rise of restrictions for the production and the use of the polluting refrigerants. It is now acknowledged that in order to sati...

The use of heat pumps is increasing worldwide, and knowledge of their properties is becoming more and more important. Although numerous tests regarding heat pumps have been performed, due to the large number of influencing variables, the entire range of input parameters is not covered, and there is no overall picture regarding the range of the coefficient of performance (COP) of heat pumps and their output parameters. This study extends existing research and provides a much more detailed comparison of results for the application of R1234yf and R1234ze(E) refrigerants, including the pressure drop across the evaporator, condenser, and internal heat exchanger (IHX). The appropriate mathematical model for the selected components was defined and verified experimentally. A total of 60 series of measurements were performed at different evaporating and condensing temperatures. The deviation of the numerical simulation results from the experimentally determined results was up to 7.4% for coo...

This research was set up to design and fabrication a table-type refrigerator unit using locally sourced materials. The objectives of the research are to: 1. Design and construct a table-type refrigerating unit using locally sourced materials. 2. to carry-out cost analysis of the fabricated refrigerator. The construction of tabletype refrigerating unit using locally was carried-out applying a ten-step procedure. The construction materials include steel bar for frame and copper pipe for the inner walls. The refrigerator constructed is a storage and preserving facility, which could be used to keep food fresh for a long time. It is therefore recommended that the content of this research be widely communicated to enlighten the populace on the procedures of design and construction of refrigerator to bring about the cooling effect and which is of great importance to the survival and of living human day-today activities.

This paper investigates the results of a Second Law analysis applied to a mobile air conditioning system (MACs) integrated with an internal heat exchanger (IHX) by considering R152a, R1234yf and R1234ze as low global warming potential (GWP) refrigerants and establishing R134a as baseline. System simulation is performed considering the maximum value of entropy generated in the IHX. The maximum entropy production occurs at an effectiveness of 66% for both R152a and R134a, whereas for the cases of R1234yf and R1234ze occurs at 55%. Sub-cooling and superheating effects are evaluated for each one of the cases. It is also found that the sub-cooling effect shows the greatest impact on the cycle efficiency. The results also show the influence of isentropic efficiency on relative exergy destruction, resulting that the most affected components are the compressor and the condenser for all of the refrigerants studied herein. It is also found that the most efficient operation of the system resulted to be when using the R1234ze refrigerant.

This paper investigates the results of a Second Law analysis applied to a mobile air conditioning system (MACs) integrated with an internal heat exchanger (IHX) by considering R152a, R1234yf and R1234ze as low global warming potential (GWP) refrigerants and establishing R134a as baseline. System simulation is performed considering the maximum value of entropy generated in the IHX. The maximum entropy production occurs at an effectiveness of 66% for both R152a and R134a, whereas for the cases of R1234yf and R1234ze occurs at 55%. Sub-cooling and superheating effects are evaluated for each one of the cases. It is also found that the sub-cooling effect shows the greatest impact on the cycle efficiency. The results also show the influence of isentropic efficiency on relative exergy destruction, resulting that the most affected components are the compressor and the condenser for all of the refrigerants studied herein. It is also found that the most efficient operation of the system resulted to be when using the R1234ze refrigerant.

Vapour compression refrigeration systems are widely used refrigeration method in industries as well as domestic applications from a long times. There were many improvements made to get higher performance of such systems. In this paper we discuss about improvement way of such systems by useful superheating of refrigerant before entering to the compressor. The analysis shows that how could increase the performance of vapour compression systems by useful superheating occurring in evaporator to producing extra refrigerating effect. This might be possible if the heat absorbed for superheating purpose produce the additional cooling effect. The superheating of refrigerant also provide the safe working condition of compressor. The working conditions are: condenser and evaporator pressures of 7.2 bar and 2.2 bar respectively, R-12 used as a refrigerant and superheating of 10 ℃. The analytical comparison shows the way to give the preference to such superheating under the working conditions me...

After study of many literatures gives the knowledge of flow of characteristics of refrigerant through capillary tube as well as to know about the working fluids for refrigeration system. In present study, the many household refrigerators used a different type of refrigerants as per as their characteristic, the R600a refrigerant have been discussed. In study of many literatures it is concluded that the capillary tube used in refrigerator for refrigerant flow has been suitable for helix coiled tube. Also it is concluded that R600a refrigeratnt is low GWP and low flammable refrigerant, so application of this of refrigerant is suitable for replacing R12, R22 and R134a.

The exchange of heat is one of the most important processes in the mechanical industry and heat exchanger is the major equipment used to transfer heat from one medium to another. This project work on the Computer Aided Design (CAD) of shell and tube, double pipe and spiral coil heat exchanger aims to provide an easy way to design it. A case study question was taken and all the necessary calculations in the thermal design are carried out using standard method of heat exchanger design. The thermal design is then used as a guide to the computer aided design using computer codes. The computer software program used is the Visual Basic called Visual Basic 6.0 (VB 6) because of its numerous advantages over the other software programmes. The result gotten from the computer aided design was compared to the result from the thermal design. The computer aided design software was equally used to test other problems on shell and tube, double pipe and spiral coil heat exchanger. Because the comput...

Vapour compression refrigeration systems are widely used refrigeration method in industries as well as domestic applications from a long times. There were many improvements made to get higher performance of such systems. In this paper we discuss about improvement way of such systems by useful superheating of refrigerant before entering to the compressor. The analysis shows that how could increase the performance of vapour compression systems by useful superheating occurring in evaporator to producing extra refrigerating effect. This might be possible if the heat absorbed for superheating purpose produce the additional cooling effect. The superheating of refrigerant also provide the safe working condition of compressor. The working conditions are: condenser and evaporator pressures of 7.2 bar and 2.2 bar respectively, R-12 used as a refrigerant and superheating of 10 ℃. The analytical comparison shows the way to give the preference to such superheating under the working conditions me...

This paper presents a computer-based first law and exergy analysis applied to vapour compression refrigeration systems for determining subcooling and superheating effects of environmentally safe new refrigerants. Three refrigerants are considered: R134a, R407c and R410a. It is found that subcooling and superheating temperatures directly influence the system performance as both condenser and evaporator temperatures are affected. The thermodynamic properties of the refrigerants are formulated using artificial neural network (ANN) methodology. Six ANNs were trained to predict various properties of the three refrigerants. The training and validation of the ANNs were performed with good accuracy. The correlation coefficient obtained when unknown data were used to the networks were found to be equal or very near to 1 which is very satisfactory. Additionally, the present methodology proved to be much better than the linear multiple regression analysis. From the analysis of the results it is found that condenser and evaporator temperatures have strong effects on coefficient of performance (COP) and system irreversibility. Also both subcooling and superheating affect the system performance. This effect is similar for R134a and R407c, and different for R410a.

Refrigeration system holds an important role in chemical/petrochemical processes. The traditional cascade refrigeration system (CRS) used in ethylene plants contains multiple refrigerants working at multiple temperature/pressure levels. In this study, a general methodology is developed for the optimal process synthesis of a CRS based on exergy analysis. This procedure involves four stages: (1) refrigeration system exergetic analysis; (2) optimization model development for simultaneous synthesis of refrigeration system and heat exchanger network (HEN); (3) HEN configuration; and (4) final solution validation. The exergy-temperature chart is used to comprehensively analyze a CRS. A mathematical model is presented to minimize total compressor shaft work of the HEN-considered CRS, where multiple recycling loops satisfying all cooling/heating demands are simultaneously addressed. The optimal solution is examined by rigorous simulations to verify its feasibility and consistency. The efficacy of the developed methodology is demonstrated by a case study of a propylene CRS in an ethylene plant.

In this work, the thermodynamic analysis of dedicated mechanically subcooled vapour compression refrigeration system is presented. A software based computer program in EES has been formulated for computation of the performance results. The effect of varation of degree of subcooling (5-30 o C), evaporator temperature (-20 to 10 o C) and condenser temperature (30-50 o C) has been investigated for energetic and exergetic performance of the system. The analysis of the system has been carried out using zero ODP and very low GWP (1 to 4) refrigerants viz.HFO-R1234ze and R1234yf to compare the performance of HFC-R134a. The results depicts that the COP and exergetic efficiency of dedicated subcooled VCR cycle are better than that of simple VCR cycle. Refrigerant R1234ze performs better than R1234yf and comparable to R134a.

Power Regeneration Technique in Vapour Compression Refrigeration Plants is presented for the purpose of upgrading already existing plants, each characterized by Main Compressor, Evaporator, Condenser and Main Expansion Valve. The Power Regeneration Concept is illustrated and theoretical results deeply discussed in relation to the upgrading of Refrigeration Plants whose Cooling Power being given or whose Main Compressor remain unchanged. Changes in performance and internal variables are deeply analysed for various arrangement options. Experimental results are also given providing the performance improvement of the Refrigeration Plants equipped with Power Regeneration Systems. Cooling Power and COP improvements up to 100% and 80% respectively are expected for a given Main Screw Compressor; while COP increasing up to 70% and Main Compressor Delivery reduced to 50% are evidenced for constant Cooling Power Plants.

ZusammenfassungDas Arbeitsmittel in Wärmepumpen unterliegt einer Vielzahl von Anforderungen, welche für einen effizienten und sicheren Betrieb eingehalten werden müssen. Weiterhin steigt die Anzahl markterhältlicher Arbeitsmittel durch die Entwicklung neuer Gemische kontinuierlich an, wodurch deren Auswahl erschwert wird. Aus diesem Grund wird im Rahmen dieses Beitrags eine Marktanalyse alternativer Arbeitsmittel durchgeführt und die selektierten Arbeitsmittel hinsichtlich ihres Potentials für Wärmepumpen bewertet. Die Marktanalyse beinhaltet eine Einordnung der Arbeitsmittel durch politische Vorgaben (kein Ozonabbaupotential, geringes Treibhauspotential), sicherheitstechnischer Aspekte (Toxizität, Brennbarkeit) sowie technischer Anforderungen (unterkritischer Betrieb, maximale Prozesstemperaturen). Hierbei werden 32 Fluide identifiziert, welche die gestellten Anforderungen einhalten. Diese sind alle brennbar und größtenteils entweder Kohlenwasserstoffe (KW) oder Hydrofluorolefine (...

In the field of refrigeration and air conditioning, the transition from using chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) to using hydrofluorocarbon (HFC) as refrigerants has been driven by the need to prevent the depletion of the stratospheric ozone layer. Although HFC refrigerants have low ozone depletion potential, their high global warming potential (GWP) is a serious concern. After the passing of the Kigali Amendment to the Montreal Protocol, UN member nations are now required to switch to low-GWP refrigerants, such as hydrofluoroolefins (HFO), and natural refrigerants. HFO-1123 has very low GWP and should emerge as a new refrigerant in refrigeration and air-conditioning equipment. However, HFO-1123 may undergo a disproportionation reaction under high-temperature and high-pressure conditions. This is a self-decomposition reaction accompanied by significant increases in pressure and temperature. Therefore, to put HFO-1123 into practical use, it is first necessary...

This work presents a Modelica library aimed to simulate vapor compression systems at both steady and transient conditions. The simulation of these specific systems is particularly challenging from both the phenomena and the numerical resolution point of views. The main goal of the library is to provide, not only accuracy and robustness, but also very low computational time. It is worth mentioning that, although the baseline version of the library is currently operative, its development continues in order to improve or add new features.Most of the components developed for the library are simulated by means of look-up tables or efficiency curves for the sake of quickness. The main efforts were focused on two critical aspects of the system. On the one hand, heat exchanger models were developed based on a switching moving boundary approach in order to have a relatively high ratio between accuracy and resolution time. This method takes into account the distribution of phases along heat e...

The present work aims at evaluating the performance characteristics of a vapor compression heat pump (VCHP) for simultaneous space cooling (summer air conditioning) and hot water supply. In order to achieve this objective, a test facility was developed and experiments were performed over a wide range of evaporator water inlet temperature (14:26 C) and condenser water inlet temperature (22:34 C). R134a was used as a primary working fluid whereas water was adopted as a secondary heat transfer fluid at both heat source (evaporator) and heat sink (condenser) of the heat pump. Performance characteristics of the considered heat pump were characterized by outlet water temperatures, water side capacities and coefficient of performance (COP) for various operating modes namely: cooling, heating and simultaneous cooling and heating. Results showed that COP increases with the evaporator water inlet temperature while decreases as the condenser water inlet temperature increases. However, the evaporator water inlet temperature has more effect on the performance characteristics of the heat pump than that of condenser water inlet temperature. Actual COP of cooling mode between 1.9 to 3.1 and that of heating mode from 2.9 to 3.3 were obtained. Actual simultaneous COP between 3.7 and 4.9 was achieved.