Characteristic Analysis of a Multi-split Type Air-Conditioning System for Buildings Under Performance Degradation of Components

Abstract

Multi-split type air-conditioning systems for buildings, which have multiple indoor units, require energy-saving operation. However, their performances, including cooling and heating capacity and COP, are decreased during long operating times because of aging degradation of system components and refrigerant leakage from movable parts. Hence, a performance monitoring method to detect performance degradations and to identify degraded components online must be developed. As a preliminary survey, the present study analyzed the characteristics of a multi-split type air-conditioning system under the performance degradations of system components and the reduction in the refrigerant charge amount in the cycle by using our steady-state cycle simulation model. The decreases in the adiabatic efficiency of the compressor and the heat transfer coefficients outside the tube of the condenser and evaporator are examined as typical performance degradations. The numerical simulation revealed the distinctive trends of the system characteristics under the performance degradations and the importance of the performance monitoring under the normal condition to identify a degraded component.