Effects of an Internal Heat Exchanger in a Refrigerant System with Carbon Dioxide on Its Cooling Coefficient of Performance and Cooling Capacity

2008 ◽  
Vol 34 (5) ◽  
pp. 505-512 ◽  
Author(s):  
Shogo Tamaki ◽  
Yuuko Fujii ◽  
Yohsuke Matsushita ◽  
Hideyuki Aoki ◽  
Takatoshi Miura ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Internal Heat ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Internal Heat Exchanger

Theoretical Analysis and Experimental Researches on Internal Heat Exchanger in CO2 Trans-Critical Cycle

2012 ◽  
Vol 204-208 ◽  
pp. 4336-4342
Author(s):  
Hui Xia Lu ◽  
Jing Lv ◽  
Zhe Bin He ◽  
Jin Yu Wang ◽  
Jia Wei Zhou
Keyword(s):  
Heat Exchanger ◽  
Internal Heat ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Outlet Temperature ◽  
Internal Heat Exchanger ◽  
High Side ◽  
Side Pressure ◽  
Experimental Researches ◽  
Regenerative Cycle

The change of system performance caused by regenerative cycle in different operating conditions was analyzed in this paper, comparing the cycle with or without internal heat exchanger in a CO2 trans-critical cycle. We analyzed theoretically the performance of CO2 trans-critical cycle with the internal heat exchanger, and found that the coefficient increased with the decreasing of the high side pressure and the increasing of outlet temperature in gas cooler, in a certain range of the high side pressure and outlet temperature. The evaporation temperature could be raised when the system with internal heat exchanger and at the same time the coefficient of performance could be improved obviously. At lower high side pressure, the performance coefficient could be improved significantly by increasing the suction superheat. The higher the gas cooler outlet temperature was, the more obvious the increase was.

Performance characteristics of natural-refrigerants- based ejector expansion refrigeration cycles

2009 ◽  
Vol 223 (5) ◽  
pp. 543-550 ◽  
Author(s):  
J Sarkar
Keyword(s):  
Heat Exchanger ◽  
Internal Heat ◽  
Area Ratio ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Internal Heat Exchanger ◽  
Optimum Parameters ◽  
And Performance ◽  
Vapour Compression ◽  
Cycle Temperature

The thermodynamic analyses and comparison of three natural-refrigerants-based vapour compression refrigeration cycles (ammonia, isobutane, and propane) are presented in this article using a constant pressure mixing ejector as an expansion device. Optimization of the area ratio of the ejector is done based on maximum cooling coefficient of performance (COP) and performance improvement for different operating conditions. The effect of using an internal heat exchanger is studied as well. Results show that optimum area ratio and cooling COP increases with a decrease in cycle temperature lift, whereas the COP improvement over basic expansion cycle increases with the increase in cycle temperature lift. Study shows that the optimum parameters, as well as performance using the ejector as an expansion device, are strongly dependent on the refrigerant properties as well as the operating conditions. The optimum area ratio is maximum for ammonia and minimum for propane, whereas maximum cooling COPs are similar. Using the ejector as an expansion device, propane yields a maximum COP improvement of 26.1 per cent followed by isobutane (22.8 per cent) and ammonia (11.7 per cent) for studies ranges. The effect of using an internal heat exchanger in the ejector expansion refrigeration cycle is found to be not profitable.

Transcritical Carbon Dioxide Refrigeration as an Alternative to Subcritical Plants

2016 ◽  
pp. 100-159
Author(s):  
Adriana Greco ◽  
Ciro Aprea ◽  
Angelo Maiorino
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Critical Temperature ◽  
Experimental Analysis ◽  
Internal Heat ◽  
Refrigeration Cycle ◽  
Desiccant Wheel ◽  
Internal Heat Exchanger ◽  
Transcritical Carbon Dioxide ◽  
Vapour Compression

Carbon dioxide (R744) is as a valid alternative to classical substances such as HFCs used in vapour compression plants. A transcritical refrigeration cycle is needed because the critical temperature of carbon dioxide is usually lower than the ambient temperature. In this chapter the performances of a transcritical cycle have been evaluated with a prototype R744 system working as a classical spit-systems to cool air. An experimental analysis has been carried out on the effect of: refrigerant charge, internal heat exchanger, heat rejection pressure on the energetic performances of the transcritical plant. An experimental analysis of a hybrid trans-critical refrigerator-desiccant wheel system has been carried out in order to improve the COP. The experimental transcritical cycle has been examined in comparison with a classical vapour compression plant working with the R134a.

The optimal charge of carbon dioxide in water–water heat pump systems with and without an internal heat exchanger

2017 ◽  
Vol 24 (2) ◽  
pp. 99-106 ◽  
Author(s):  
Zhili Sun ◽  
Shengchun Liu ◽  
Youcai Liang ◽  
Mengjie Song ◽  
Jianghe Guo
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Internal Heat ◽  
Internal Heat Exchanger

scholarly journals Thermodynamic Analysis of a CO2 Refrigeration Cycle with Integrated Mechanical Subcooling

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 4 ◽  
Author(s):  
Laura Nebot-Andrés ◽  
Daniel Calleja-Anta ◽  
Daniel Sánchez ◽  
Ramón Cabello ◽  
Rodrigo Llopis
Keyword(s):  
Thermodynamic Analysis ◽  
Internal Heat ◽  
Cooling Capacity ◽  
Point Of View ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Refrigeration Cycle ◽  
Internal Heat Exchanger ◽  
Promising Solution

Different alternatives are being studied nowadays in order to enhance the behavior of transcritical CO2 refrigeration plants. Among the most studied options, subcooling is one of the most analyzed methods in the last years, increasing cooling capacity and Coefficient Of Performance (COP), especially at high hot sink temperatures. A new cycle, called integrated mechanical subcooling cycle, has been developed, as a total-CO2 solution, to provide the subcooling in CO2 transcritical refrigeration cycles. It corresponds to a promising solution from the point of view of energy efficiency. The purpose of this work is to present, for the first time, thermodynamic analysis of a CO2 refrigeration cycle with integrated mechanical subcooling cycle from first and second law approaches. Using simplified models of the components, the optimum operating conditions, optimum gas-cooler pressure, and subcooling degree are determined in order to obtain the maximum COP. The main energy parameters of the system were analyzed for different evaporation levels and heat rejection temperatures. The exergy destruction was analyzed for each component, identifying the elements of the system that introduce more irreversibilities. It has been concluded that the new cycle could offer COP improvements from 11.7% to 15.9% in relation to single-stage cycles with internal heat exchanger (IHX) at 35 °C ambient temperature.

scholarly journals Experimental Analysis and Optimization of an R744 Transcritical Cycle Working with a Mechanical Subcooling System

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3204 ◽  
Author(s):  
Daniel Sánchez ◽  
Jesús Catalán-Gil ◽  
Ramón Cabello ◽  
Daniel Calleja-Anta ◽  
Rodrigo Llopis ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Critical Temperature ◽  
Computational Model ◽  
Experimental Analysis ◽  
Experimental Tests ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Liquid Heat

In the last century, the refrigerant R744 (carbon dioxide) has become an environmentally friendly solution in commercial refrigeration despite its particular issues related to the low critical temperature. The use of transcritical cycles in warm and hot countries reveals the necessity of adopting different configurations and technologies to improve this specific cycle. Among these, subcooling methods are well-known techniques to enhance the cooling capacity and the Coefficient of Performance (COP) of the cycle. In this work, an R600a dedicated mechanical subcooling system has been experimentally tested in an R744 transcritical system at different operating conditions. The results have been compared with those obtained using a suction-to-liquid heat exchanger (IHX) to determine the degree of improvement of the mechanical subcooling system. Using the experimental tests, a computational model has been developed and validated to predict the optimal subcooling degree and the cubic capacity of the mechanical subcooling compressor. Finally, the model has been used to analyze the effect of using different refrigerants in the mechanical subcooling unit finding that the hydrocarbon R290 and the HFC R152a are the most suitable fluids.

Transcritical Carbon Dioxide Refrigeration as an Alternative to Subcritical Plants

2015 ◽  
pp. 295-359
Author(s):  
Adriana Greco ◽  
Ciro Aprea ◽  
Angelo Maiorino
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Critical Temperature ◽  
Experimental Analysis ◽  
Internal Heat ◽  
Refrigeration Cycle ◽  
Desiccant Wheel ◽  
Internal Heat Exchanger ◽  
Transcritical Carbon Dioxide ◽  
Vapour Compression

Carbon dioxide (R744) is as a valid alternative to classical substances such as HFCs used in vapour compression plants. A transcritical refrigeration cycle is needed because the critical temperature of carbon dioxide is usually lower than the ambient temperature. In this chapter the performances of a transcritical cycle have been evaluated with a prototype R744 system working as a classical spit-systems to cool air. An experimental analysis has been carried out on the effect of: refrigerant charge, internal heat exchanger, heat rejection pressure on the energetic performances of the transcritical plant. An experimental analysis of a hybrid trans-critical refrigerator-desiccant wheel system has been carried out in order to improve the COP. The experimental transcritical cycle has been examined in comparison with a classical vapour compression plant working with the R134a.

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