Control and Design for a Multi-Evaporator Air-Conditioning (MEAC) System

Multi-evaporator air-conditioning (MEAC) systems are widely used and offer many advantages. However, there has been lack of experimental-based capacity controller developments for MEAC systems. On the other hand, the pipelines in an MEAC system are usually complicated and different designs would affect its operational performance. However, no previous studies on the refrigerant pipework layout design of an MEAC system have been reported. Therefore, a comprehensive research program consisting of developing a novel capacity control algorithm, and investigating the effects of refrigerant pipework and discovering the best possible pipework layout design has been carried out and is reported in this thesis.;This thesis starts with reporting the development of a novel capacity control algorithm. Experimental tests validated its control accuracy and robustness. And then, an improved novel capacity control algorithm was therefore further developed, and further controllability tests carried out. The test results showed that the improved novel capacity control algorithm was simple but could effectively restrain the magnitude of temperature variations and avoid the frequent altering in compressor speed.;Secondly, the thesis presents a modeling study on the effects of refrigerant pipeline length on the operational performance. A physical-based steady-state mathematical model has been developed which contained a sub-module to account for the influence of refrigerant pipeline length on system operational performance. The model has been validated by comparing its prediction results with the experimental results previously reported by others. Simulation results indicated that the system's COP decreased with an increase in the refrigerant pipeline length.;Thirdly, this thesis documents an analytical study of applying the Constructal Theory to discovering the best possible refrigerant pipework layout design in MEAC systems for minimizing the total power requirement. The analytical study results showed that for an MEAC system, its total heat exchanger area was decided by the total cooling load. The heat exchanger area in each room however was influenced by the location of the outdoor unit of the MEAC system when the distance among all rooms was fixed. The results also indicated that the optimum diameters of refrigerant pipelines were independent of their lengths.