| In order to solve the heating problem in the southern part of China,the ‘Solutions to heating and cooling of buildings in the Yangtze river region' has been proposed by the thirteen five national key research and development project.The heat source tower heat pump(HSTHP)technology extracts low-grad heat energy from the air in winter for heating,and dissipates waste heat to the environment in summer for cooling,and produces domestic hot water throughout the year.The system is flexible and reliable,energy-saving and environmentally friendly,especially suitable for the low temperature and high humidity environment in the Yangtze River valley in China in winter.Firstly,based on the ?-NTU method,the heat exchange model of cross-flow heat source tower was established.The empirical formula was used to simplify the NTU calculation method,which made the model more applicable for engineering.Based on the secondary development of TRNSYS,the heat source tower calculation module was created,and the accuracy of the model was validated by the measured data.The results showed that for the outlet temperature of the heat source tower,the static relative error was controlled within 4%,the dynamic average absolute error was 0.17°C and the maximum error was 0.36°C.For the latent heat transfer rate,the static relative error was controlled within 10%.Secondly,the TRNSYS platform was used to establish a simulation model based on the HSTHP system of a residential district in Changsha.Through the statistical analysis of the heating capacity and heating power data of the actual heat pump host at different temperatures and different flow rates,the performance curves of the heat pump host under different working conditions in winter were obtained.The pump model was established by the similarity law,and the model was validated by the measured data.The parameters of each component of the heat pump system were set according to the tested parameters,then an accurate system model was obtained.Thirdly,a whole year field test of the project has been conducted,and the operation of the HSTHP system was analyzed.It was concluded that the actual application of the HSTHP system had excessive flow rate at the load side and the heat source side;the temperature difference was too small,and the system lacked corresponding regulation when the heat load changes at different times in the day,resulting in the low energy efficiency of the system.The statistical analysis of the cooling and heating load of residential buildings was carried out,and the linear relationship between outdoor dry bulb temperature and load was obtained.The load distribution in winter and summer showed that the lowest load was between 4 and 8 o'clock,and the highest load was between 20 and 24 o'clock.Finally,the effects of solution flow rate,fan number,outdoor dry bulb temperature and relative humidity on system energy consumption and condensed water were simulated.An optimization objective function was proposed.The optimization considered the system energy consumption and the influence of the condensed water on the system.The temperature difference setting value between the supply and return solution in heat source side and the number of working fans were optimized under different outdoor temperatures,relative humidities and different daily time periods.The optimal control strategies under different working conditions were obtained. |
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