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An attempt has been made to investigate numerically a two-stage refrigeration system with flash intercooler of 50 kW cooling capacity using refrigerant R410A and its possible alternative R32. Development of the simulation model for the analysis of the system has been carried out in engineering equation solver considering the energetic, exergetic, economic, and environmental aspects. Evaporator and condenser temperatures have been varied from −50 °C to −25 °C and 40 °C to 55 °C, respectively, to carry out the simulation work. Co-efficient of performance (COP), exergetic efficiency, and plant cost rate are the three performance parameters computed in this present work. Results show that the performances of the system using R32 are comparable with those of the system using R410A. It is also observed that R32 shows slightly better thermo-economic performances at higher condenser temperature. Multi-objective optimization has also been carried out using the toolbox available for optimization in matlab to obtain the optimum performance and optimum operating conditions for both the refrigerants. Optimization results also show better thermo-economic performances of R32 over R410A though compressor discharge temperature is higher in case of R32.

A single-stage vapour compression refrigeration system becomes inefficient and impractical when the temperature lift between the evaporator and the condenser becomes large. Under the high temerature lift, different losses in the system increase and more refrigerant vapour is formed at the end of the throttling process. The authors have attempted to analyze a vapour compression refrigeration system with dedicated subcooler for high-temperature lift applications using R134a in the main cycle and four low GWP refrigerants in the subcooler cycle. The modelling of the proposed system has been carried out in EES considering the energy, exergy and economic aspects for the simulation of the system. The predicted results show that the use of the proposed system is more beneficial from both performance and economy point of view for high temperature lift. Nearly 27% improvement in both energetic and exergetic performances are noted whereas cost is reduced by 2% when the proposed system is used instead of a typical refrigeration system. Finally, the present investigation concludes that the use of refrigerant R1234ze is much efficient than the other investigated refrigerants due to its low GWP and compressor discharge temperature, in spite of achieving better thermo-economic performances using R152a as subcooler refrigerant.

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A twin cylinder, constant speed, direct injection CI (diesel) engine was run on jatropha biodiesel and diesel fuel blends. The engine was directly coupled to a hydraulic dynamometer whose load was varied by adjusting load wheel on the top of the engine. The test results were recorded for pure diesel, pure biodiesel (B100) and different diesel/biodiesel blends. The performance characteristics shows that brake specific fuel consumption (BSFC) decreases rapidly with increase of load up to 4.0 to 4.5 kW (55% to 62% of full load) and then decreases slowly. This result also indicates that BSFC increases when the percentage of biodiesel in the blends is increased. Brake thermal efficiency also increases from high biodiesel blends to pure diesel fuel. Each fuel curve shows maximum efficiency reaches at the load range of 5.0 to 5.5 kW (68% to 75% of full load). Pure diesel has maximum efficiency 29.6%, where as pure biodiesel has maximum efficiency of 21.2%. The exhaust gas temperature increases with the load for all fuel blends. Pure biodiesel gives higher exhaust temperature (320°C) than pure diesel (260°C). The exhaust gas temperature increases with the higher percentage of biodiesel blends in different fuel blends. The probable reason for that is biodiesel contains oxygen atoms which make the combustion process complete and hence more energy is released. In respect of emission characteristics, carbon mono-oxide (CO) and hydrocarbon emissions are improved with the addition of biodiesel to diesel. But these emissions increase with the increase of load for all fuel blends. NOx emission increases with load as well as percentage of blending of biodiesel in the diesel fuel.