The paper presents a general distributed model of a vertical U-tube direct expansion heat exchanger coupled with the ground. This model is developed for studying the dynamic thermal behavior of a buried heat exchanger...The paper presents a general distributed model of a vertical U-tube direct expansion heat exchanger coupled with the ground. This model is developed for studying the dynamic thermal behavior of a buried heat exchanger which is an integral part of a so-called direct expansion heat pump. The transient conservative equations of mass, momentum and energy considering single and two-phase flow of refrigerant are derived and presented. The diffusive heat exchange with the ground is treated using an analytical approach to treat short-time scale response of vertical boreholes based on an imposed temperature. The thermal interference between the two pipes of the heat exchanger is also considered. The mathematical equations of the model are numerically presented using a control volume formulation and the solution of the system of equations is obtained by successive iterations. The dynamic behavior of the evaporator is simulated and the numerical results are analyzed regarding spatial parameters distribution and thermal interference influence.展开更多
In this research,a novel small-scale single-panel liquid-to-air membrane energy exchanger has been used to numerically investigate the effect of given number of heat transfer units(4.5),different cold inlet air temper...In this research,a novel small-scale single-panel liquid-to-air membrane energy exchanger has been used to numerically investigate the effect of given number of heat transfer units(4.5),different cold inlet air temperature(1.7,5.0,10.0℃)and different low heat capacity ratio(0.4,0.5,0.6,0.7,0.8,0.9)on the steady-state performance of the energy exchanger.This small-scale energy exchanger represents the full-scale prototypes well,saving manufacturing costs and time.Lithium chloride is used as a salt solution in the system and the steady-state total effectiveness of the exchanger is evaluated for winter inlet air conditions.The results show that total effectiveness of the energy exchanger decreases with heat capacity ratio in the mentioned range.Maximum numerical total effectiveness of 97%is achieved for the energy exchanger.Increasing the heat capacity ratio values on given inlet air temperature,the humidification capacity of energy exhanger is also investigated in this paper.The humidification performance increases with heat capacity ratio.The highest humidification performance(4.53 g/kg)can be reached when inlet air temperature is 1.7℃,and heat capacity ratio is 1.0 in winter inlet air conditions in the range of low heat capacity ratio.展开更多
文摘The paper presents a general distributed model of a vertical U-tube direct expansion heat exchanger coupled with the ground. This model is developed for studying the dynamic thermal behavior of a buried heat exchanger which is an integral part of a so-called direct expansion heat pump. The transient conservative equations of mass, momentum and energy considering single and two-phase flow of refrigerant are derived and presented. The diffusive heat exchange with the ground is treated using an analytical approach to treat short-time scale response of vertical boreholes based on an imposed temperature. The thermal interference between the two pipes of the heat exchanger is also considered. The mathematical equations of the model are numerically presented using a control volume formulation and the solution of the system of equations is obtained by successive iterations. The dynamic behavior of the evaporator is simulated and the numerical results are analyzed regarding spatial parameters distribution and thermal interference influence.
基金financially supported by the Natural Science and Engineering Research Council of Canada (NSERC)Venmar CES,Inc.,Saskatoon,SK,Canada and Hungarian Eotvos Scholarship,Balassi Institute Hungarian Scholarship Board Office,Budapest,Hungary
文摘In this research,a novel small-scale single-panel liquid-to-air membrane energy exchanger has been used to numerically investigate the effect of given number of heat transfer units(4.5),different cold inlet air temperature(1.7,5.0,10.0℃)and different low heat capacity ratio(0.4,0.5,0.6,0.7,0.8,0.9)on the steady-state performance of the energy exchanger.This small-scale energy exchanger represents the full-scale prototypes well,saving manufacturing costs and time.Lithium chloride is used as a salt solution in the system and the steady-state total effectiveness of the exchanger is evaluated for winter inlet air conditions.The results show that total effectiveness of the energy exchanger decreases with heat capacity ratio in the mentioned range.Maximum numerical total effectiveness of 97%is achieved for the energy exchanger.Increasing the heat capacity ratio values on given inlet air temperature,the humidification capacity of energy exhanger is also investigated in this paper.The humidification performance increases with heat capacity ratio.The highest humidification performance(4.53 g/kg)can be reached when inlet air temperature is 1.7℃,and heat capacity ratio is 1.0 in winter inlet air conditions in the range of low heat capacity ratio.
