DOI: 10.14457/tu.the.2016.1462
title: Development of the jet refrigeration system to be used with waste heat

description: A jet refrigeration system or ejector refrigeration system which is a kind of the thermally driven refrigeration system is of current interest. This is because it can be powered by heat which may be captured from industrial waste heat, exhaust gas from combustion, geothermal, hot water produced by solar collector, etc. Therefore, the reduction of the electricity consumption for producing thermal comfort can be made possible while the increasing need of thermal comfort is still satisfied with the use of the ejector refrigerator. In addition, the use of the jet refrigeration system is also recognized as a promising way to relieve the environmental situation. This is due to the reduction in the electricity consumption, resulting in a decrease in greenhouse gases emission. However, there is not many evidences to demonstrate the use of a jet refrigeration system in an actual air–conditioning application. Especially for the country where the ambient is rather hot and humid such as Thailand, it is unavailable. Therefore, the development of a jet refrigeration system which is able to operate at the hot and humid ambient (such as Thailand) is necessary to investigate in order to make progress in the ejector refrigeration technology.    To make progress in the ejector refrigerator for an actual air–conditioning application, this present work presents the design, construction, and operation of the prototype R141b ejector refrigerator for use as an air–conditioner in Thailand, which is a rather hot and humid environment. The main objective of this dissertation is to demonstrate the possibility of using an ejector refrigerator for the actual air–conditioning application. The dissertation is separated into two main parts: (1) An experiment and CFD simulation of R141b ejector refrigerator; and (2) Development and test of a prototype R141b ejector refrigerator for an actual air–conditioning application. In part 1, the background of the ejector refrigerator operation and CFD simulation for alternative analyses of the parameters that affect the ejector performance are acquired. The main purpose of this part is to determine the proper designed criteria of the ejector geometries and the important equipment. In this case, a small scale experimental R141b ejector refrigerator is constructed for experimentation. The experimental results in various working conditions and ejector’s geometries are carried out. CFD simulation is also employed to simulate the flow inside the ejector. With the use of CFD simulation, the flow process occurring inside the ejector is able to be visualized graphically. Therefore, a better understanding of the flow state of the supersonic stream, which significantly affects the ejector performance, can clearly be explained. In the conclusion of part 1, the design criteria which can be used for further developing the prototype ejector refrigerator is determined. This is so that the prototype ejector refrigerator can be operated at its best performance.In part 2, the details of design, construction, and operation of the prototype R141b ejector refrigerator for use as an air–conditioner in Thailand are proposed. The description and steps to develop the ejector refrigerator are provided. Initially, computational fluid dynamics (CFD) simulation is employed to predict the ejector performance. The simulation is implemented to ensure that the ejector which is designed particularly for a prototype refrigerator is workable throughout the range of operating conditions for Thailand. The prototype ejector refrigerator is designed to produce the chilled water with cooling capacity up to 4500 W. The generator is based on a water–heated type which is powered by hot water of which the temperature is varied between 90 and 98ºC. The heat supplied to the generator is simulated by an immersion electric heater with capacity of 27 kW. The condenser is cooled by water provided by a commercial cooling tower. The cooling water temperature produced is between 28 and 32ºC. To implement the test, the tested method of the prototype ejector refrigerator is separated into two main parts: (1) Tested with directly supplied cooling load to the chilled water (first test); and (2) Tested as an air–conditioner. For the first test, the cooling load is applied directly to a chilled water box by installing the electric heater inside. The chilled water temperature at various cooling capacity is observed. The main purpose is to make sure that the prototype, which newly constructed, is workable throughout the designed conditions and tunes up the prototype so that it is workable at the desired point. For the air–conditioning test, the chilled water is supplied to a cooling fan–coil unit which is installed within the tested room. It is found that the prototype R141b ejector refrigerator is workable satisfactorily at the operating condition consistent with Thailand’s environment. The prototype ejector refrigerator can produce the thermal comfort condition for the tested room with the cooling capacity up to 4500 W.