Model-Based Analysis of Recovered Heat Driven Vapor Absorption Refrigeration System Using the Waste Heat from a 5.2 kW Single Cylinder Diesel Engine

Abstract

The exhaust gases from an engine contain significant amount of heat energy that is wasted through the burnt gases. Part of this heat energy can be harnessed to achieve a specific purpose. This work therefore studied the feasibility of utilizing the recovered heat energy within the exhaust gases of a compression ignition engine for a vapor absorption refrigeration (VAR) system. This is as an alternative to vapor compression refrigeration widely used in the refrigeration system. The paper explained the possibility and advantages of waste heat application on VAR and also evaluated the heats gained and losses at the different components of the VAR system. The parameters for the study are coefficient of performance (COP); generator temperature (Tg); heat loads in generator (Qg), evaporator (Qe) and condenser (Qc). The study was done by mathematically modeling and applying thermodynamics first law to the individual components of a lithium bromide-water (LiBr-H2O) solution VAR system. With cooling capacity, Qe=3.8KW; constant Te=40C, Tc=350C, Ta=300C and varying generator temperatures from 850C to 1350C, the parameters for the study were computed using the results from the models for the generator, evaporator, absorber and condenser. This study elucidates the fact that with waste heat temperature of 850C, the COP of VAR can be as much as 0.861 depending on refrigeration capacity.