| Membrane-based energy recovery ventilator?ERV?takes advantages of vapor-permeable membrane to recovery latent and sensible energy of exhaust air and pretreat fresh air.The pretreatment of fresh air is of significance for energy conservation of air-conditioning.In this paper,vapor-permeable composite membranes based on different property of support,sodium alginate and lithium chloride?LiCl?were fabricated.Sodium alginate and LiCl were the corresponding active layer and hydrophilic additive and calcium chloride solution acted as cross-linking agent.Firstly,sodium alginate-cellulose acetate was manufactured and hydrophilic cellulose acetate with pore size of 0.12?m was the support.The highest water vapor permeance of composite membranes reached up to 4.42×10-88 kg/m2·s·Pa,which was 1.56 and 2.63 times higher than those of the composite membrane without LiCl and the traditional commercial paper,respectively.This result indicated that LiCl was beneficial to improvement of water vapor permeance and this composite membrane had a better vapor performance than commercial paper.Secondly,hydrophobic fabric nonwovens served as the support constructions and sodium alginate-nonwoven fabric composite membrane was developed.Experimental results show that LiCl content enhanced vapor permeance of composite membrane;and the highest vapor permeance was 29.8×10-8 kg/m2·s·Pa,which was 10 times higher than that of composite one without LiCl.Compared with sodium alginate-cellulose acetate,hydrophobic support was more advantageous to enhancement of vapor permeance when the lithium chloride content was identical.Water solubility of composite membranes varied from20.6%to 25.5%,which demonstrated a certain waterproofness of membranes.Besides,Fourier Transform Infrared Spectroscopy analysis demonstrated that sodium alginate membrane introduced plenty of hydroxyl groups and carboxylic acid ions on the surface of nonwoven fabrics.Simultaneous thermal analysis showed that cross-linking enhanced thermal stability of sodium alginate membrane and composite membranes can regenerate at 50oC.Furthermore,two ERVs with different sodium-alginate composite membranes were fabricated and characterized by measuring their sensible,latent and enthalpy efficiencies.It is found that these three efficiencies at the speed of 0.35 m/s can reach up to 83.9%,87.4%and 86.7%under summer condition,and 80.8%,81.7%,and 81.1%under the winter condition,respectively. |
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