Thermodynamic analyses of vapourabsorption refrigeration systems using Excel

Vapour-absorption refrigeration (VAR) systems do not compress a vapour refrigerant as in the more commonly used vapour-compression refrigeration (VCR) systems. Instead, the refrigerant vapour is dissolved in a liquid absorbent at the lower pressure and the solution is heated to release it at the higher pressure. Thus, VAR systems require considerably less work input than VCR systems. Since a low-temperature heat source can be used for the heating process, VAR systems are important elements for efficient use of energy and for the utilisation of renewable energies such as solar and geothermal energies. Thermax provides two sets of property functions for the two most commonly used absorbent-refrigerant combinations in VAR systems, which are lithium bromidewater, with water as the refrigerant, and water-ammonia, with ammonia as the refrigerant. This chapter verifies these functions by analysing different types of VAR systems. Initially, the chapter gives a brief review of VAR systems and discusses the temperaturepressure-concentration and enthalpy properties of water-lithium-bromide solutions. It verifies the functions for lithium-bromide-water by comparing the results of analysing a basic VAR system, a single-effect system with a heat-exchanger, and a double-effect system with the data provided by Stoecker and Jones [1], ASHRAE [2], and Abdulateef et. al. [3]. The ammonia-water functions are verified by comparing their results for analysing the single-effect VAR system with those given by Sun [4].