Design and Fabrication of a Vapor Absorption Refrigeration System for Vehicle Cabin Cooling Utilizing Exhaust heat

Abstract

Automobile air-conditioning is a necessity of present life. Designing energy efficient and cost effective products are the main challenge in modern world. From that perspective when we look at a vehicle air conditioning system, it doesn’t fit that criteria in most of the cases. Vapor compression refrigeration cycle used in modern automobile uses refrigerant 134-a and the compressor of automobile air-conditioning is run by engine crankshaft, which reduces the mileage of the automobile. An internal combustion engine gives about 35% efficiency and when we put the load of air conditioning, it consumes upto 15-20% energy of the crankshaft. Also 65% heat energy is wasted through exhaust and cooling system. In many industries waste heat is used to reutilize in refrigeration system using Vapor Absorption System. The main theme of this project is to utilize the waste heat of the exhaust gases generated in internal combustion engines. Before leaving these gases to the atmosphere through the exhaust necessary mass of exhaust gases is by passed and is made to deliver it generator so as to run the vapour absorption refrigeration system there by conserving the energy. We have made the same system in smaller scale so that it can be used in vehicles and cabin temperature can be kept at a comfortable level. By controlling the heat provided in generator and pump flow rate we have ensured that the cabin temperature stays at the thermal comfort zone of 20-25 degree Celcius. In this project we have used Temperature sensors, Water flow sensor, Pressure gauge, Valves, Electromagnetic relay and Arduino to monitor the system conditions with time. This also enables us to control the system completely which wasn’t done in a smaller scale before. This project takes the idea of using VARS for air cooling one step closer to industrialization and with continual research this can be developed to use in vehicles in near future. Owing to the threat of global warming due to high thermal disposal and to compensate the energy crisis, VARS is likely to gain immense prominence in the coming years. The aim of the project is to perform analysis on absorption refrigeration system using lithium-bromide as absorbent and water as refrigerant to find out the optimal operating temperatures on the thermal loads of components and their coefficient of performance. Finally coming up with the operating conditions where it can run by effectively utilizing the waste heat of the exhaust gases.