|Author:||Tse, Yau Ki|
|Title:||Improvement of a new adaptive controller for the variable speed direct expansion air conditioning system with an emphasis on system stability|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Air conditioning -- Control
Refrigeration and refrigerating machinery
|Department:||Department of Building Services Engineering|
|Pages:||13, 71 pages : color illustrations|
|Abstract:||The operational instability of refrigeration system has been studied over decades. It will lead to a lower operational safety, and a higher energy consumption of a refrigeration system There have been two different views on the possible causes of operational instability of refrigeration system or known as hunting. The first of the view is the inherent operational characteristics of an evaporator, the observation of the fluctuation in refrigerant mixture-vapor transition point. The second view is the inherent operational characteristics of an expansion valve (EV). Hunting is observed both in thermostatic expansion valve (TEV) controlled refrigeration system e.g. time constant of the evaporator pipe wall and electronic expansion valve (EEV) controlled refrigeration system e.g. nonlinearities in response from control input. On the other hand, an adaptive controller is reported based on the relationship between the inherent operational characteristics and the operational stability for an experimental variable speed (VS) direct expansion (DX) air conditioning (A/C) system. The adaptive controller was then validated using an experimental VS DX A/C system. The results showed that the parameters of PID controller will be changed at different supply fan speeds to improve the stability of DS setting in the DX A/C system|
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