Abstract：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.
沈志杰, 闵敬春, 段江菲. 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[J]. 清华大学学报（自然科学版）, 2020, 60(11): 958-966.
SHEN Zhijie, MIN Jingchun, DUAN Jiangfei. Numerical study on influence of supply inlet air parameter distribution on a membrane-type total heat exchanger. Journal of Tsinghua University(Science and Technology), 2020, 60(11): 958-966.
[1] ZURAIMI M S, THAM K W. Effects of child care center ventilation strategies on volatile organic compounds of indoor and outdoor origins[J]. Environmental Science & Technology, 2008, 42(6):2054-2059. [2] XUE L X, LIU B X, CHEN J, et al. Structure and properties of total-heat exchange membranes for energy saving heat exchange ventilation processes[J]. Sustainable Development of Urban Environment and Building Material, 2012, 374-377:568-571. [3] YE W, GAO J, ZHANG X, et al. Studies of relationship between ventilation, pollution exposure and environmental health of buildings[J]. Indoor and Built Environment, 2017, 26(2):147-151. [4] HU T, MIN J C, SONG Y Z. Analysis of the effects of mass transfer on heat transfer in the process of moisture exchange across a membrane[J]. Chinese Science Bulletin, 2010, 55(12):1221-1225. [5] HU T, MIN J C, SONG Y Z. Analysis of the effects of the heat of sorption on the process of heat transfer in moisture exchange across a membrane[J]. Science in China Series E:Technological Sciences, 2008, 51(12):2120-2127. [6] ZHANG L Z, NIU J L. Effectiveness correlations for heat and moisture transfer processes in an enthalpy exchanger with membrane cores[J]. Journal of Heat Transfer, 2002, 124(5):922-929. [7] ZHANG L Z, JIANG Y. Heat and mass transfer in a membrane-based energy recovery ventilator[J]. Journal of Membrane Science, 1999, 163(1):29-38. [8] NIU J L, ZHANG L Z. Membrane-based enthalpy exchanger:Material considerations and clarification of moisture resistance[J]. Journal of Membrane Science, 2001, 189(2):179-191. [9] MIN J C, SU M. Performance analysis of a membrane-based energy recovery ventilator:Effects of outdoor air state[J]. Applied Thermal Engineering, 2011, 31(17-18):4036-4043. [10] MIN J C, SU M. Performance analysis of a membrane-based enthalpy exchanger:Effects of the membrane properties on the exchanger performance[J]. Journal of Membrane Science, 2010, 348(1-2):376-382. [11] MIN J C, SU M. Performance analysis of a membrane-based energy recovery ventilator:Effects of membrane spacing and thickness on the ventilator performance[J]. Applied Thermal Engineering, 2010, 30(8-9):991-997. [12] MIN J C, DUAN J F. Comparison of various methods for evaluating the membrane-type total heat exchanger performance[J]. International Journal of Heat and Mass Transfer, 2016, 100:758-766. [13] MIN J C, DUAN J F. Membrane-type total heat exchanger performance with heat and moisture transferring in different directions across membranes[J]. Applied Thermal Engineering, 2015, 91:1040-1047. [14] GUO J F, HUAI X L, CHENG K Y, et al. The effects of nonuniform inlet fluid conditions on crossflow heat exchanger[J]. International Journal of Heat and Mass Transfer, 2018, 120:807-817. [15] WANG L N, MIN J C. Thermodynamic analysis of adsorption process at a non-equilibrium steady state[J]. Chinese Science Bulletin, 2010, 55(31):3619-3625. [16] ZHENG W, WOREK W M. Numerical simulation of combined heat and mass transfer processes in a rotary dehumidifier[J]. Numerical Heat Transfer, Part A:Applications, 1993, 23(2):211-232. [17] INCROPERA F P, DEWITT D P. Fundamentals of heat and mass transfer[M]. New York, USA:Wiley, 1985. [18] SHAH R K, LONDON A L, WHITE F M. Laminar flow forced convection in ducts[J]. Journal of Fluids Engineering, 1980, 102(2):256-257. [19] KUEHN T H, RAMSEY J W, THRELKELD J L. Thermal environmental engineering[M]. 3rd ed. Upper Saddle River, USA:Prentice Hall, 1998. [20] SIMONSON C J, BESANT R W. Energy wheel effectiveness, Part I:Development of dimensionless groups[J]. International Journal of Heat and Mass Transfer, 1999, 42(12):2161-2170. [21] SIMONSON C J, BESANT R W. Energy wheel effectiveness, Part Ⅱ:Correlations[J]. International Journal of Heat and Mass Transfer, 1999, 42(12):2171-2185. [22] STRUCHTRUP H. Psychrometrics[M]//STRUCHTRUP H.Thermodynamics and energy conversion. Berlin, Germany:Springer, 2014. [23] YANNIOTIS S. Solving problems in food engineering[M]. New York, USA:Springer, 2008. [24] GUO Z Y, ZHOU S Q, LI Z X, et al. Theoretical analysis and experimental confirmation of the uniformity principle of temperature difference field in heat exchanger[J]. International Journal of Heat and Mass Transfer, 2002, 45(10):2119-2127.
2020, Vol. 60 
