Could an absorption refrigeration system be driven by the engine exhaust gas and cooling fluid of a minibus?

Abstract

© 2021, The Brazilian Society of Mechanical Sciences and Engineering.This study evaluates the possibility of recovering energy from the cooling and exhaust systems of an internal combustion engine as a source input for an absorption refrigeration system. Sensors were installed in a minibus to measure the temperature and mass flow of the exhaust gas. Their signals, together with those of the vehicle’s built-in sensors, were acquired during tests under different conditions: warm-up, city route, and highway route. Simulations of a lithium bromide absorption refrigeration cycle were performed using the experimental data as input. In the model, a fraction of the engine cooling fluid and exhaust gas was considered as the generator’s energy source. Hence, recuperative heat exchangers were included with an auxiliary water circuit between the generator and exhaust system. The results showed an average cooling capacity of 1.5 kW during the initial warm-up phase, reaching 7.2 kW under road-route driving conditions. In the city, where minibusses are used most, a cooling capacity of 3.6 kW was found, that is, 68% of the cooling demand in vehicles in this category. To operate under these conditions and during the warm-up period, an alternative system would have to be added as an electrical heater. Moreover, the system requires a controller to bypass a fraction of the available exhaust gas during high engine demands.