入口空气参数分布对薄膜式全热交换器性能影响的数值研究

Numerical study on influence of supply inlet air parameter distribution on a membrane-type total heat exchanger

薄膜式全热交换器是一种可同时回收热量和湿份的空气-空气热回收装置,其换热芯由具有良好透湿性的膜材料制成,通常用来减少建筑能耗并改善室内空气品质。由于全热交换器内部通道分布不均或外部干扰,全热交换器入口空气可能存在分布不均的情况。该文采用数值计算研究了薄膜式全热交换器入口空气参数分布对全热交换器传热传质特性的影响,包括入口空气温度、含湿量和速度分别呈线性和抛物线分布的情况。建立了全热交换器传热传质模型,通过数值计算得到了不同入口条件下全热交换器的显热效率、潜热效率和全热效率以及全热交换器薄膜两侧的温、湿差分布云图。结果表明:入口空气参数的线性分布对全热交换器效率影响较为明显,而抛物线分布对效率影响很小,但二者对薄膜两侧的温、湿差分布均有影响;传热传质相互影响并存在耦合,但传热对传质的作用很弱;入口空气温度和含湿量分布越不均匀,越容易出现反向传热传质现象,从而恶化传热传质。

Membrane-type total heat exchangers(THX) are air-to-air heat exchangers with a core made of a water vapor permeable membrane that transfers both heat and moisture. These heat exchangers are often used to reduce building energy consumption and improve indoor air quality. However, non-uniform internal channel structures and external disturbances can lead to maldistributions of the supply inlet air parameters into the heat exchanger. This research numerically examines the effects of various supply inlet air parameter variations on the heat and moisture transfer characteristics, including linear and parabolic distributions of the inlet air temperature, moisture ratio and velocity. The model then simulates the heat and mass transfer in the heat exchanger to predict the temperature, moisture and enthalpy effectiveness distributions as well as the temperature difference and humidity ratio difference contours between the two sides of the membrane for the various inlet conditions. The results show that the linear distribution significantly affects the effectiveness while the parabolic distribution has little effect, with both affecting the temperature difference and humidity ratio difference contours between the two sides of the membrane. The heat transfer and the mass transfer affect each other, with the heat transfer having only a weak effect on the mass transfer. More nonuniform supply inlet air temperature and moisture ratio distributions increase the probability that the heat and mass transfer will be in opposite directions, which reduces both the heat and mass transfer.