Study on water temperature prediction and control strategy for household air source heat pump system using floor heating

Air source heat pump is one of the most important forms of clean heating. It is widely used in residential buildings. When heating with radiant floors, the floor's inherent heat storage exothermic properties result in a delayed thermal response to the changes of heating regulations. During the change of outdoor temperature and electricity price, how to control the indoor thermal environment and achieve operation saving is one of the issues to be studied related to air source heat pumps. This paper establishes a mathematical model for predicting the system's hour-by-hour water supply temperature based on meteorological parameters and the indoor heating temperature through buildings’ heat balance relationship. A simplified model for supply water temperature controll is proposed considering the thermal inertia of floor. At the same time, a system simulation model was established using TRNSYS. Considering the influence of changes in outdoor temperature, heating load, thermal inertial characteristics of the floor, four different control strategies were proposed. According to the simulation results, with these control strategies, the indoor air room temperature can be controlled within the target range, and the maximum room temperature change was only 0.6℃ on typical day. The energy use can be reduced by approximately 20% compared to the actual condition, in which overheating happens sometimes. The proposed time-shift shutdown controls can achieve energy saving, while keeping stable thermal environment during heating in residential buildings.