Development and Applications of Simulation Codes for Air-to-Water and Ground-Coupled Heat Pump Systems

In this Thesis, new simulation codes for the evaluation of a heat pump system seasonal performance are presented. The codes apply to electric air-to-water and ground-coupled heat pump systems based on a vapor compression cycle, used for building heating, cooling and domestic hot water production. Numerical models are developed to simulate different kinds of air-to-water heat pumps by means of the bin-method. The models take into account the different operating modes of mono-compressor on-off, multi-compressor and inverter-driven heat pumps. The heat pump system seasonal performance is analyzed in terms of SCOP and SEER in relation to the thermal characteristics of the building, the climate of the location and the kind of heat pump control system. Furthermore, numerical codes for the hourly simulation of air-to-water heat pump systems are developed. The dynamic codes are implemented in the software MATLAB and apply to on-off and inverter-driven heat pumps for building heating, cooling and domestic hot water production, coupled with storage tanks and integrated by a gas boiler or electric heaters. The codes are used, in particular, to evaluate the seasonal performance and the primary energy consumption of the inverter-driven air-to-water heat pump employed in the retrofit of a residential building in Bologna (Italy). A code for the hourly simulation of ground-coupled heat pump systems is developed. The code, implemented in MATLAB, employs g-functions expressed in analytic form and applies to on-off and inverter-driven heat pumps, used for building heating and/or cooling. The whole system, composed by the heat pump and the coupled borehole heat exchanger field, can be simulated for several years. The code is applied to analyze the effects of the inverter and of the total length of the borehole field on the mean seasonal performance of a ground-coupled heat pump system designed for a residential house with dominant heating loads