Bubble Absorber, Swirl Flow, Heat and Mass Transfer, R134a-DMF
Vapour absorption refrigeration systems (VARS) importance has increased due to utilization of solar energy, waste heat, etc. To improve the efficiency of this system, it is necessary to increase the heat and mass transfer in the absorber with tangential injectors. Experiments were carried out to analyze a tubular heat exchanger used as an absorber with tangential injector. In this study, a vertical bubble absorber is considered for heat and mass transfer studies with refrigerant, R134a (1,1,1,2 –Tetrafluoroethane) and absorbent, DMF(dimethyl formamide). R134a vapour is injected into the absorber using two injectors of 4.8 mm inner diameter at an injection angle of 30° to the vertical axis and parallel to the azimuthal axis of the absorber, which enhances mixing of R134a with liquid R134a-DMF solution to increase the heat and mass transfer. Experiments were carried out by varying the operational parameters by varying refrigerant flow rate from 5 lph to 15 lph and liquid solution flow rate in the range of 20 lph to 50 lph. Chilled water is used to load the refrigeration system evaporator with flow rate 100 lph and temperature in the range of 5 to 20oC. Hot water is supplied to the generator in the range of 60 to 91oC with flow rate of 80 to 200 lph. Cold water is used as coolant to the condenser and absorber in the temperature range of 11 to 25 oC with the flow rate of 80 to 160 lph. Effects of operational parameters viz., gas flow rate, solution initial concentration, and solution pressure and solution temperature and number of injector on absorber performance are varied and analysed. Mass transfer effectiveness, heat transfer effectiveness, overall heat transfer coefficient, volumetric mass transfer coefficient, absorption rate and heat rejected from the absorber have been evaluated for the absorber. Heat and mass transfer coefficients evaluated from the experiments are compared with numerical model and it is found to be in good agreement. REFERENCE Suresh M., Mani A. (2012), Experimental studies on heat and mass transfer characteristics for R134a-DMF bubble absorber, International Journal of refrigeration 35 pp. 1104-1114. Santosh Kumar Panda, Mani A. (2014), Bubble dynamics study with tangential nozzles in a bubble absorber, International Sorption Heat Pump Conference at Maryland University, Maryland,USA.