Research On Optimization Design Technology For Applying Air Source Heat Pump Heating To Middle School Buildings

In recent years,with the vigorous promotion of coal-to-electricity policies in northern China,air-source heat pumps have been widely used because of their advantages of convenient installation,simple management,safety and reliability.However,The time for large-scale development of the air-source pumps in northern China is still short.Meanwhile the funds,construction period and actual conditions still have a lot of limitations.Most users simply replace the heat source,and replace the heating end with the heat source.There is a lack of adequate technical supports and researches in regulatory strategies and thermal comfort.At present,the researches on the application and operation strategy optimization of air-source heat pump’s systems are mainly focused on rural housing,while the system optimization of public buildings are not concerned.Based on this,this paper selects school buildings with distinctive load characteristics as the research objects,and studies the students thermal comfort and o peration strategy of heat pump heating system.Firstly,a secondary school in Beichen District of Tianjin was selected as an example.More than 150 students were surveyed on the thermal comfort problem,and the environmental parameters were tested simultaneously.After calculation,the expected temperature of the human body in the middle school building was 17.1 °C.Under the same conditions of other factors,the males heat expectation temperature is about 1 °C lower than that of females.Secondly,the operating parameters of the air heating pump system during the whole heating season were monitored,and the correlation between the indoor thermal environment and the supply and return water temperature changes in different stages of the heating season was analyzed.The analysis found that the weather conditions,the number of people and the activity status had a great impact on the indoor temperature;the operation mode at different periods of the heating period had a great influence on the thermal comfort and energy consumption.Now,a more simple time-varying water temperature control mode is adopted.The comfort is lower and the energy consumption is higher than before.Therefore,this paper will optimize it later,and use the simulation software to propose a fine time-divided water temperature control mode to improve the students thermal comfort and reduce the electricity consumption in the whole season.Finally,using the air-source heat pumps heating system of the middle school as an object,and the EnergyPlus energy simulation software was used to simulate it on weekdays’ and holidays’ conditions.There are three working conditions for the working day,which are the nighttime intermittent heating mode,the daytime working time change back to the water temperature control mode,and the low temperature operation antifreeze mode.On holiday,there is only a low temperature running antifreeze mode.Considering the increasing thermal comfort and energy saving of the next day,according to the coupling effect of water temperature and running time of the system at night on the dynamic characteristics of room temperature,the author found that it is more energy saving to start the system earlier at lower water temperature than later at higher water temperature.That is to say,turning on later is more energy efficient.In addition,using the simulated water supply temperature setting value and the relationship between the unit opening time and the outdoor temperature,the typical conditions of different heating stages in the heating season are simulated by the adjustment of the return water temperature with the outdoor temperature during the daytime working period.The results show that the air-source heat pump can reduce power consumption in three typical temperature periods in winter while ensuring indoor thermal comfort,and can decrease the power consumption by 10.7%,17.5% and 4.1%.For the winter holiday,on the basis of meeting the minimum indoor temperature requirement,the low temperature operation mode adopts a method of reducing the return water temperature,and the energy saving rate reaches 16.1%.