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A major portion of the worldwide emissions arise from mobile air-conditioning systems with hydrofluorocarbon refrigerant as working substance and which is one of major cause for the greenhouse effect. R134a refrigerant having GWP of 1400 has been extensively used in car air conditioning. To reduce greenhouse gas emissions, the current R134a refrigerant must be phase out as per Kigali Amendment. The present study deals with cooling load calculation of car model by heat balance method as per ASHRAE standard using local climate condition. Further, thermodynamic analysis of R1234yf as an alternate refrigerant to R134a has been carried out for automobile air conditioning system. The required properties of refrigerants are extracted from Engineering Equation Software. The thermodynamic analysis is carried out to study the effect of operating parameters viz. condensing temperature, evaporating temperature, degree of superheating and degree of subcooling on COP, EDR, exergy efficiency and entropy generation. The previous literature reports mainly focus on separate study of either cooling load calculation or energy analysis or exergy analysis of R1234yf and R134a for automobile air conditioning system, while this paper presents the comprehensive study of new low GWP R1234yf as an alternate refrigerant to R134a in automobile air conditioning system with cooling load calculation including the concept of energy, entropy and exergy analysis. The percentage difference in COP between R134a and R1234yf system varies from 2.44 % to 4.78 % while percentage difference in EDR varies from 6.79 % to 2.87 % when evaporating temperature varied from -10 °C to 10 °C. With 12 °C of superheating at compressor inlet, the COP of R134a is 3.9 whereas COP of R1234yf is 3.75, which makes 3.85 % lower than that of R134a. The R1234yf has 4.78 % lower value of exergy efficiency as compared to that of R134a at evaporating temperature of -10 °C and it is found that maximum exergy destruction takes place in compressor. [ABSTRACT FROM AUTHOR]

Heat exchanger developments are driven by increase in energetic efficiency and emission reduction. To reach the required standards, new systems are required based on mini-channels along with macro channels also. Mini-channels can be described as tubes with one or more ports extruded in aluminium or any other material like copper, steel etc. with hydraulic diameter in the range of 0.2 to 3 mm. Its use in refrigeration systems became a reality; thanks to the human ability to make micro-scale systems. Some heat exchanger enterprises have some models developed specially for their use in automotive sector, cooling sector and industrial refrigeration without having knowledge of how these reduced geometries affect the most important parameters such as pressure drop and the heat transfer coefficient. To overcome this, an exhaustive literature review of the last two decades has been performed to determinate the state of the research. Among all the publications, several models have been reviewed to check the predicting capacities of them as most of them were developed for macro channels along with single port mini-channel tubes. This work presents a comparative study of existing heat transfer correlations for horizontal flow through mini-channels. Present work total 317 experimental results of condensation heat transfer coefficient obtained from several published literatures and also various condensation heat transfer correlations are reviewed for horizontal flow through mini-channels. Results of condensation heat transfer coefficient obtained for various correlations are compared with the experimental results. Among all correlations used the Bohdalet’s correlation gives value of condensation heat transfer coefficient closer to experimental results and has a mean relative deviation (MRD) of 5.4 % whereas mean absolute relative deviation (MARD) of 20.72%.Hence in present work the effort has been made to find better model to predict the condensation heat transfer coefficient which can fit the experimental data with least MRD and MARD.