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In the present work, the parallel hub axial flow annular diffuser's performance characteristics with divergent casing varying between equivalent cone angle (10°, 15°, and 20°) with area ratio 3 have been evaluated computationally as well as experimentally. The performance of three diffusers was tested at different inlet swirl angles (from 0° to 25°) for swirling and nonswirling flow. Simulations have been carried out on a fully developed flow at Reynolds number 2.5×105. The results were analyzed based on the velocity profiles, static pressure recovery coefficient, and the total pressure loss coefficient. The result analysis shows that the inlet swirl flow improves the recovery of pressure and also delays the flow separation on the casing. Moreover, the findings also show that the best performance was achieved in equivalent cone angle 10° at the inlet swirl angle of 7.5° compared to other diffusers. [ABSTRACT FROM AUTHOR]

The aim of present work is the evaluation of mechanically subcooled simple vapour compression refrigeration system on the basis of energy and exergy analysis, and compatibility of alternative low GWP and zero ODP HFOs R1234yf and R1234ze to replace HFC 134a. A computer program has been developed in Engineering Equation solver software to compute the system performance parameters such as COP, exergetic efficiency, total exergy destruction and exergy destruction ratio. The effect of degree of subcooling (5 to 30°C), evaporator temperature (-30°C to 15°C), effectiveness of liquid vapour heat exchanger (0.2 to 1.0) and compressor efficiency (0.4 to 1.0) has been investigted on the performance parameters viz. exergy desturction, exergy destruction ratio (EDR) and exergetic efficiency of the system components. The results of current analysis highlight that the R1234ze is the best alternate refrigerant considered in the analysis and can replace R134a as the COP and exergetic efficiency of R1234ze are 1.87% and 1.88% more than that of R134a for 30°C of subcoooling. However, R1234yf offers lower performance than R134a. The components condenser and evaporator are the sites of highest and lowest exergy destruction respectively for the refrigerants considered. [ABSTRACT FROM AUTHOR]

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°C), evaporator temperature (-20 to 10°C) and condenser temperature (30-50°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. [ABSTRACT FROM AUTHOR]

The aim of this paper is to determine the best available alternative which could replace existing refrigerant R22, with minimum or no changes in the air conditioning system. For this purpose, both the theoretical as well as experimental studies done in this area of research have been reviewed. The most popular HFC, R410A is having lower critical temperature, which restricts its usage in compression based systems working at higher condensing temperatures whereas for R407C, a change to synthetic lubricant is required and HC-290 is flammable. It is suggested that until the safety issue of use of hydrocarbon refrigerants in quantities exceeding 500gm is resolved, we should go for those mixtures of HFCs and HCs for which TEWI index is the lowest. [ABSTRACT FROM AUTHOR]

The performance of axial annular diffuser with parallel hub and diverging casing for same equivalent cone angle of 20° has been analysed with the help of computational fluid dynamics for area ratio 2, 3 and 4. The analysis has been carried out for flow regime with various experimentally obtained inlet velocity profiles for area ratio 2 with or without swirl. The flow behaviour inside the annular diffuser was analysed and pressure recovery coefficient was computed which agrees reasonably well with the experimental/available data. Further prediction of flow behaviour inside the annular diffuser and the expected pressure recovery coefficient has been computed. [ABSTRACT FROM AUTHOR]