Paper Conference

Proceedings of Building Simulation 2017: 15th Conference of IBPSA


Multi-split Type Gas-Engine-Driven Heat Pump System Model to Estimate Performance in Low Temperature and High Humidity Conditions in Mid-winter

Eisuke Togashi
Kogakuin University, Tokyo, Japan

Abstract: A gas-engine-driven heat pump (GEHP) shows higher thermal capability than an electric heat pump (EHP) in winter because it uses residual heat from the engine exhaust. A GEHP rarely needs defrosting, which otherwise significantly reduces the efficiency of a heat pump system. The widespread use of multi-split type heat pump systems in commercial buildings has helped in enabling individual zone control. To evaluate the characteristics of a multi-split type GEHP, heat recovery from a gas engine, defrosting in an evaporator, and heat flow between indoor and outdoor units should be expressed quantitatively. Elgendy et al. (2011) developed a semiempirical GEHP model that consists of a scroll compressor and plate evaporator. However, they did not address heating operations. Zhang et al. (2005) and Zhang et al. (2014) developed a GEHP model for the heating mode. However, these models are not multi-split type, and hence, cannot be applied to individual zone control systems. Hornberger developed a TRNSYS subroutine, which simulates a GEHP. Physical formulas are used to evaluate evaporators and condensers in this model, and the compressors effectiveness is calculated from the pressure ratio. Unfortunately, the heat transfer coefficients of heat exchangers are fixed, and therefore, the defrosting phenomena cannot be simulated. This study develops a multi-split type GEHP model that consists of a compressor, an indoor unit, and an outdoor unit. The model components are expressed with physical formulas to simulate defrosting phenomena in winter. Firstly, a simulation model of a frosting coil (outdoor unit) is described, and then sensitivity analysis is performed. Description of model for indoor units is skipped since they have no defrosting phenomena and are much simpler than outdoor unit models. Secondly, a GEHP simulation model and parameter estimation method for the model is described. Finally, the model is integrated with a building heat-load simulation model.
Pages: 319 - 326