Dynamic Performance Of Closed Heat Source Tower In Winter

Nowadays,in light of the extreme climatic issues caused by global climate change and El Nino phenomenon,ice and snow have appeared frequently in south cities of China.In these cities,there are more than 90 days daily average temperature less than 6?,and sometimes this kind of cold whether may even take place over 100 days.In this scenario,people living in these cities are in dire need of an equipment to improve their living environment.Therefore,the heat source tower heat pump system has developed rapidly and attracted numerous scholars' attention as an effective heating system since invented.However,the current research on heat source towers is limited to steady-state conditions and cannot reflect its actual operating conditions.So in this paper,a mathematical model is established to analyse the dynamic performance of closed heat source tower.The outline of this paper can be divided into four parts as listed below.Firstly,a theoretical model describing the process of heat transfer between heat source tower and air in winter is developed based on the mass and energy balance for the moisture,tube/fin,air,and working solution.Secondly,the closed heat source tower's heat exchanger is divided into two-dimensional grids by the control unit and the equations in the model are discretized according to the grid relationships.So these equations can be solved by numerical calculation in MATLAB,and the dynamic heat transfer process in the closed heat source tower in winter can also be simulation.And then,an experimental system is established to test the accuracy of the model.Two groups of experiments are designed in this system,one of which is conducted in steady state,while another in unsteady state.In the course of experiment,The data is recorded and compared with simulation results,the results show that the RMSE(Root Mean Square Error)of the model under the two working conditions are 0.151 ? and 0.198 ? respectively,which proves the model is highly accuracy and thus can be used to analyse practical problems.Last but not the least,the dynamic heat transfer characteristics of closed heat source tower are analysed by numerical simulation.The results show that the sudden change in inlet temperature and velocity of working solution in closed heat source tower only has little influence on the stability of Heat Pump,while the change in the air velocity would have a significant influence on it.Furthermore,the small temperature difference between air and working solution could reduce the frost risk of closed heat source tower in winter.