Simulation Research On Low Temperature Hot Water Floor Heating System With Air Source Heat Pump

Floor radiation system with low temperature hot water (generally range between40℃and45℃or so) as a heating medium has been widely used in architectural heat supply, and the hot water temperature range happens to be the ideal working condition of air source heat pump. The influence of environment temperature changes on the heating performance of the air source heat pump decreases by making full use of the heat storage capacity of the enclosure and each structural layer of the floor. But air source heat pump’s heating performance is closely related to the environment, the heating performance has a big difference between peak and off-peak load time because of the corresponding ambient temperature. For the heating demanders, well operating mode should reduce operation cost as far as possible under the premise that comfort is guaranteed, so how to reasonable arrangement the running time on peak and off-peak load time under the background of TOU price policy is the key to establishing an operation mode.This article will focus on hot summer and cold winter region in China, taking a150m2three-bedroom located on17layers of a high-rise building in Chongqing as the object. A simulation research was conducted on the indoor thermal environment and heating performance of the unit under the full off-peak running mode and peak and off-peak running mode.A transient simulation model of low temperature hot water floor radiant heating system with an air source heat pump in a high-rise building is built by TRNSYS and EES software. Simulation results keep a good agreement with the reported experimental data.Considering the user’s living habits and the thermal inertia of floor radiant heating system, discussion focus on the influence of different operating mode to system efficiency, operating cost and the influence of thermal comfort under the TOU price policyby using numerical simulation method.Peak and off-peak intermittent running mode presented in this paper based on the heat storage properties of the floor radiant heating system can improve heating efficiency through avoiding bad working conditions of the air source heat pump. From the results of numerical simulation, the new running mode can improve the average room temperature during family members frequently activities in normal weather conditions. In extreme weather conditions, new running mode although failed to guarantee the room temperature higher than17℃all the time, it remains above18℃during family members frequently activities and significantly improve the thermal comfort. Thermal discomfort value and operation cost were simulated under different ratio of peak and off-peak running time. Mean square error method is used to determine the two indicators’relative weight, the comprehensive evaluation value is given by weighted summation of thermal discomfort value and operation cost. From the point of the evaluation results, keep the ratio of peak and off-peak running length at5:3or4:4is a reasonal choice.In view of full off-peak and peak and off-peak operation mode can’t meet the requirement of comfort during part of time, heating compensation control strategy is put forward.From the results of numerical simulation, heating compensation control strategy can significantly improve the indoor thermal environment in two kinds of operation modes, each room temperature can remain above17℃throughout the day. Based on the peak and off-peak running time reasonable proportioning, the operation adjustment for the demand of working days and holidays under conventional and extreme weather conditions are discussed.