Evaluation of Control Method of VRF (Variable Refrigerant Flow) System by Experimental Study and Simulation Analysis

抄録

Recently, the installation of VRF (Variable Refrigerant Flow) heat pump systems in offices – regardless of their size and shape – has become popular in Japan. This system consists of a packaged outdoor unit and multiple indoor units connected by a refrigerant pipe. It has the advantage of fitting in easily with the any building plans because of its standardized system. Moreover, this system is energy saving and enhances user comfort, as it can be easily operated as an indoor unit. On the other hand, as there are infinite combination of indoor units of VRF systems available for the users to be chosen freely within the range of outdoor capacity, and since the indoor units can be turned on and off independently, operation conditions are not predictable. So it is very difficult to find adequate control parameters under wider load conditions. For this reason, the purpose of this paper is set to organize the control characteristics systematically. In order to evaluate VRF system, we develop a numerical simulation model based on the laws of physics. This model can easily add and delete indoor unit's elements. Therefore, we hope that this model is adequate for VRF system’s analysis. In this report we reproduce machine’s operation conditions precisely; for example, for unstable condition, we reproduce the hunting phenomenon of expansion valve and evaluate the effects of different control constants under different loads.