Effect Of Operational Parameters On Heat and Mass Transfer In Generator of R134a/DMF Absorption Refrigeration System

摘要

Vapour absorption refrigeration systems (VARS) has regained the attention due to their potential for renewable/waste heat utilization. To improve the efficiency of these systems, it becomes obligatory to make component level studies on processes. In this present study, investigations on the heat and mass transfer in compact generator of the vapour absorption refrigeration system have been carried out using R134a-Dimethyl formamide (DMF). An experimental facility of VARS has been fabricated using brazed plate heat exchangers as generator, condenser, absorber, evaporator and solution heat exchanger. Hot water source is used to supply hot water between 80 oC and 98 oC to suit utilization of solar energy, waste heat, etc to the generator. Cooling water from cooling water source is circulated through the absorber and condenser to remove the heat. Water from cooling load simulator is circulated to the evaporator. Investigations have been carried out on VARS with a rated cooling capacity of 1kW by varying the operating parameters viz, solution flow rate from 0.02 m3hr-1 to 0.05 m3hr-1, liquid refrigerant flow rate from 0.002 m3hr-1 to 0.015 m3hr-1, hot water temperature from 85 oC to 97 o C. Generator pressure is varied from 620 kPa to 920 kPa, hot water flow rate from 0.12 m3hr-1 to 0.32 m3hr-1 and solution initial concentration is varied from 0.59 kgkg-1 to 0.75 kgkg-1. The effect of solution flow rate, generator temperature and generator pressure on the performance of generator and the absorption system has been investigated. Heat and mass transfer coefficients, heat transfer rate, mass desorption rate increase with generator temperature and solution flow rate but decrease with increase in generator pressure.