Development of variable refrigerant flow heat-pump model for annual-energy simulation

Abstract

In this study, a model of a variable refrigerant flow (VRF) heat pump is developed that combines multiple physical equations into only one characteristic equation. The parameters of the characteristic equation are estimated according to the specifications in the manufacturer catalog published based on the definitions established by the Japanese Industrial Standards. This model allows the evaluation of effects that cannot be represented by the conventional models; for example, defrost, unbalanced heat loads, changes in pipe length, and changes in indoor and outdoor temperature, and humidity. The model is sufficiently fast for use in practical applications because it can perform calculation for building with 10,000 m2 floor area in 1 min. The effects of the above-described characteristics on the energy performance vary depending on the local climate. The availability of such a model facilitates the comparison of VRF-system configurations during their design phase, which improves the energy efficiency of buildings.