Design and Development of Small Capacity Vapor Absorption Refrigeration System

Abstract

Vapor absorption refrigeration methods are usually used to take care of bigger cooling loads ranging from 10TR to 3500TR according to which their size and construction changes. Another convention about such systems is that they use waste heat or in some cases directly fuel to satisfy the requirement of heat supply in generator. In present work Lithium Bromide and water based vapor absorption refrigeration system has been designed which can use solar energy as an heat input and can work 24 hours even in absence of Sun hours and can produce 1TR refrigeration. Various ways of energy storage for the system to work in absence of Sun have been studied in literature review and out of them refrigerant storage method have been chosen. For solar operated 24hrs VAR system the excess amount of refrigerant that is required for after sun hours operation of system, is being produced by condenser and generator which is stored in refrigerant storage tank. Strong and weak solutions of LiBr-water required after sun hours for absorber use, are stored in two different tanks. Thus system is designed in such a way that after sun hours sufficient amount of refrigerant is available to produce cooling effect. Three types of system have been designed such as, system which is completely based on solar energy, hybrid system which is working on solar energy in day time and on fuel gas in night time, and system which is completely based on gas fuel. Based on design in present work the theoretical COP for solar based VAR system is 0.67 and for hybrid system and fuel based system it is 0.87. The purpose behind design for this various options is to observe the impact on cost and size of the system. Simple cost analysis carried out for all three types of VAR systems with compare to VCR system working 24 hours and 365 days. It was found that hybrid VAR system and fuel based VAR system are not economic compared to VCR system. Solar based VAR system is economically more viable and has simple payback period of 2.5 years.

A prototype of LPG fuel based VAR system has been fabricated to check the technical feasibility of development of small capacity VAR system. Best efforts have been made to make the design based on right data and comply with standards and codes such as ASHRAE and ASME.