Comparison of compact and tubular generators performance for R134a–DMF

Abstract

Heat and mass transfer during R134a desorption in compact generator and tubular generator have been compared experimentally. An R134a–DMF based vapour absorption refrigeration system is built with brazed plate heat exchangers as condenser, absorber, evaporator and solution heat exchanger with a rated cooling capacity of 1kW. This kind of system can be operated with low grade thermal energy such as solar energy and waste heat. Generator temperature is chosen accordingly between 353K and 368K. Two types of generators in parallel, which are a brazed plate heat exchanger with chevron H-type plate channels and stainless steel concentric tubes, are investigated. Performances of the generators, at different operating conditions, have been compared, to explore the significance of compact generator for the improvement of absorption refrigeration technologies. Influence of solution flow rate, hot water inlet temperature, condensing temperature, evaporator temperature on generators is studied. Heat transfer rate, desorption rate, heat and mass transfer effectiveness increase with the hot water inlet temperature but decrease with increase in condensing temperature. Even though heat and mass transfer rates increase, heat transfer effectiveness and mass transfer effectiveness decrease with solution flow rate.