Abstract Enthalpy exchangers using water vapor perm-selective membranes are used in building ventilation systems due to their small footprint, simplicity, reduced contaminant crossover, and relatively high efficiency. Moisture permeation properties of the membrane media that vary with operating air humidity and temperature lead to significant changes in the performance of an enthalpy exchanger and thus the whole ventilation system, impacting building energy efficiency. Evaluation of the actual energy savings potential of such energy recovery devices in building ventilation systems requires models that account for this variable membrane performance. A theoretical model is developed for current generation asymmetric composite membranes used in enthalpy exchangers. This model predicts the membrane permeability as a function of local values of air humidity and temperature, based on a limited number of kinetic water vapor sorption tests of the membrane material. The membrane model is coupled with a finite-difference model of the conjugate heat and mass transfer in full cross-flow enthalpy exchanger cores. The model predictions are validated against experimental data of a commercial-scale enthalpy exchanger. The model is used to predict the influence of outdoor air parameters (temperature, humidity) on an enthalpy exchanger and the predictions are compared against a baseline case that assumes constant membrane permeability. Such assumption can result in deviations in effectiveness predictions by up to 15%. Depending on the mode of operation, outdoor air relative humidity can increase or decrease the effectiveness of enthalpy exchangers by up to 12%. In contrast, outdoor air temperature appears to have only a minimal influence on effectiveness parameters.

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使用非对称复合膜的焓交换器中的热量和水分传递建模

摘要 使用水蒸气选择性渗透膜的焓交换器因其占地面积小、简单、减少污染物交叉和相对较高的效率而被用于建筑通风系统。膜介质的透湿特性随工作空气湿度和温度而变化，导致焓交换器的性能发生显着变化，从而影响整个通风系统，影响建筑能源效率。评估建筑通风系统中此类能量回收设备的实际节能潜力需要考虑这种可变膜性能的模型。为用于焓交换器的当代非对称复合膜开发了理论模型。该模型基于膜材料的有限数量的动态水蒸气吸附测试，预测作为局部空气湿度和温度值的函数的膜渗透性。膜模型与全错流焓交换器核心中的共轭传热和传质的有限差分模型相结合。模型预测针对商业规模的焓交换器的实验数据进行了验证。该模型用于预测室外空气参数（温度、湿度）对焓交换器的影响，并将预测结果与假设膜渗透率恒定的基线情况进行比较。这种假设可能导致有效性预测的偏差高达 15%。根据操作模式，室外空气相对湿度可将焓交换器的效率提高或降低多达 12%。相比之下，室外空气温度似乎对有效性参数的影响很小。