Thermodynamics of Refrigeration Systems

As a result of global concerns over the depletion of the earth's protective stratospheric ozone layer by the atmospheric release of chloroflurocarbons (CFCs) and hydrochlorofluoro-carbons (HCFCs) refrigerants, their production has been restricted and they are no longer choices for new equipment. This paper presents theoretical investigation of the performance of some environment friendly refrigerants in a sub-cooling heat exchanger refrigeration system. Five promising environment-friendly refrigerants (R23, R32, R134a, R143a and R152a) were selected from methane and ethane derivatives and they were investigated theoretically. Sub-cooling heat ex-changer was used to evaluate the impact of selected refrigerants on the exchanger effectiveness, system capacity and coefficient of performance (COP). The results obtained showed excellent performance of R152a and R134a, and fair performance of R143a when compared with R12 in vapour compression refrigeration system. The results also showed that using R23 and R32 in the refrigeration system will be detrimental to the system performance.

The process of expansion of paper is to minimize losses and improve the basic refrigeration
cycle COP with ejector and continue on a description of the development of important refrigeration system with
R-22 refrigerant. A refrigerant R-22 is used as the working fluid. In conventional systems some work of
compressor is lost for the compression of uncondensed fluid passes through the condenser which is undesirable
for performance of refrigeration. Through this experiment the undesirable work of compressor is removed by
use very simple separator like device. The two phase flow through the ejector rebirth of pressure that also save
the compressor work for novel vapor compression cycle for refrigeration. The new cycle with an ejector device
which combines compression, with compression includes a second step. Approximately 4/5 of the final
compressor compresses the vapor pressure and addition compression, in an ejector provided, thus the amount of
mechanical energy required by the compressor is reduced and efficiency increased. The thermodynamic model
was developed for R22 refrigerant, showing a possible efficiency improvement as compared to the traditional
vapor compression cycle. The theoretical work followed by prototype and practical demonstration of 20%
energy savings in the first attempt.

Marine products are more ecologist regarding to CO2 emission while they are produced and catch. Also, they have almost same protein ratio as red meat and they are consumed all around the world. It is more common that in industrial fishing, fishes are not only catch but also different type of processes are apply for producing and storing on fishes in fishing vessel. In this way, fishes stay fresh and it makes saving time and space. In this study, fishing vessel refrigeration system which has precooling and storage system is analyzed in terms of exegetic performance with various refrigerant which has different environment effect and changing design condition. The results show that ε Tot , ECOP and COP are 0,525, 5,6 and 4,8 respectively in design conditions. Also, they become 0,85-0,45, 8-4,7 and 6,5-4 respectively regarding to temperature of sea water changing. Moreover, they become 0,525-0,490, 5-7,5 and 4,5-6 respectively regarding to temperature of storage unit changing.

The effect of heat transfer medium (HTM) on the environment is associated with ozone layer depletion and global warming. The role of HTM (working fluid) in the heating and air conditioning industries is paramount, which cannot be underestimated. The conventional refrigerant has been predominantly used over decades due to their thermodynamic properties. However, hydrocarbon refrigerants such as isobutane are considered substitutes because they have negligible global warming potential and zero ozone depletion. That makes it eco-friendly among other existing refrigerants. The investigation of the refrigeration system's performance characteristics required consideration for the coefficient of performance, refrigerating effect, and the compressor work; this enables the determination of the system's efficiency without any assumption. Another factor that suggests a better absorption of refrigerant (working fluid) into a refrigeration system is an increase in the coefficient of performance (COP). The effect will cause a reduction in the rate of energy consumption by the compressor. The result shows that the system's coefficient of performance when using R600a was 27.1% higher than when working with R134a, with an energy reduction of 23.3%.

This review paper is a study on various methods of performance improvement in domestic refrigeration systems, based on the vapor compression refrigeration VCRS cycle. Here air-cooled, water-cooled, fog cooled, evaporatively cooled condensers and nano-fluid lubricant /coolant methods their working and efficiency are reviewed, compared, analyzed and presented. The paper inspects the work done by different researchers for the maximization of heat loss from condenser & compressor and bringing about necessary modifications to reduce the overall power consumption of domestic refrigerators by improving Coefficient of Performance (COP). Numerous works have been done on improving the heat dissipation capacity of condenser but using nano-fluid in lubricant base as refrigerant and in the compressor shell as coolant is a new technology. Nano-fluid increase heat transfer due the high conductivity nano particles. It has been observed that water cooled condensers and compressors with nano-lubricants/coolants give the best performance improvements but they suit better for big or large refrigeration systems like centralized air conditioning systems or cold storage warehousing, whereas air cooled and evaporative condensers are optimal for small scale or low power appliances like domestic refrigerators, water coolers or split air conditioners to reduce overall power consumption by increasing the COP.

This paper study the performance evaluation of a refrigeration system that operates on solar energy as alternative source of power to enhance the refrigerating effect, coefficient of performance (COP), preservation of perishable items and short time drug such as vaccine, to remote communities and parts of the urban settlement around the developing nations where there is no access to modern electrical source. The system was made from locally sourced materials using a conventional refrigerant HFC134a as working fluid to improve thermal efficiency and stability of the vapour compression refrigeration system. The COP of the system was enhanced by 8.67% when working with solar and with energy reduction of 2.38% respectively. In case the weather is cloudy or during the night hour when the energy generation is low, the refrigerator can work on battery for an average of 12 hours if fully charge during the day to avoid idle time of the refrigeration system.

This paper presents a macroscopic applied innovate modeling to study the performance effects of the second law of thermodynamics on the mechanical systems. To investigate the irreversibility in mechanical systems, the energy structure of the system can be studied. Some energy components relate to the reversible processes and remaining relate to the irreversible process. Exiting models are based on the studying sub structures and therefore, need a large volume of the calculations. In this paper, at first, using a macroscopic quasi-statistical approach, a new energy structure equation is extracted and by examining it's variation in the different paths, the irreversible components as well as their structures are studied. Using the kinematic theories of dissipated energy, it can be concluded that the extracted equations have the same base as the different formulations of the second law of thermodynamics. Finally, as a mechanical system example with the possibility of irreversibility in the possible performed processes, the extracted equations are developed for viscoelasticity problems. And also the matching of the results with expected results is shown.

This paper study the performance evaluation of a refrigeration system that operates on solar energy as alternative source of power to enhance the refrigerating effect, coefficient of performance (COP), preservation of perishable items and short time drug such as vaccine, to remote communities and parts of the urban settlement around the developing nations where there is no access to modern electrical source. The system was made from locally sourced materials using a conventional refrigerant HFC134a as working fluid to improve thermal efficiency and stability of the vapour compression refrigeration system. The COP of the system was enhanced by 8.67% when working with solar and with energy reduction of 2.38% respectively. In case the weather is cloudy or during the night hour when the energy generation is low, the refrigerator can work on battery for an average of 12 hours if fully charge during the day to avoid idle time of the refrigeration system.