Study On Frosting Characteristics Of Energy Recovery Ventilators In Cold Area

Membrane total heat exchanger is a kind of total heat exchanger,which has the advantages of low cost and high heat transfer efficiency.However,during winter operation in cold areas,because of the high humidity in the exhaust passage of membrane total heat exchanger,frost phenomenon exists,which affects the heat transfer efficiency and the normal operation of membrane total heat exchanger.Therefore,in order to ensure the normal operation of membrane heat exchanger in cold winter area,this paper studies the Frosting Characteristics and control strategy of membrane heat exchanger by combining theory with experiment.The main contents are as follows:Based on the analysis of heat and mass exchange principle and frosting principle in membrane total heat exchanger,frosting can be divided into two categories: sub-zero frosting and zero frosting.Based on the principle of energy conservation,the theoretical models of subzero frosting and zero frosting are established respectively,and the experimental data are used to verify the two theoretical models.Two theoretical models were used to analyze the influencing factors of frosting criticality,and the Frosting Characteristics of membrane heat exchanger were studied.It is found that heat transfer efficiency and latent heat of condensation are the most important factors affecting frost formation.When the indoor relative humidity is low,the dry environment is in the heat exchange channel of the membrane heat exchanger.At this time,the most important factor affecting the frost critical is the heat transfer efficiency.The lower the humidity,the greater the effect of sensible heat efficiency on the frost critical.Under the influence of heat transfer efficiency,the frosting critical temperature increases with the increase of indoor humidity.When indoor relative humidity is relatively high,condensation will occur in the channel of membrane heat exchanger.The condensation latent heat is the most important factor affecting the frosting threshold.Under the influence of latent heat of condensation,the critical temperature of frosting decreases with the increase of indoor relative humidity.Based on typical meteorological year data,the mass transfer direction in membrane total heat exchanger was studied.It is found that taking the temperature and humidity corresponding to the maximum vapor partial pressure in January as the outdoor calculation parameter can ensure the normal mass transfer of membrane heat exchanger in January and the whole heating season at 83%.According to the calculated parameters,the critical value of mass transfer direction change in membrane heat exchanger is calculated.Based on the frosting critical model and frosting characteristics,the frosting control strategy of membrane heat exchanger was optimized.The results show that if the height of the single channel of the membrane heat exchanger is reduced to 2 mm and the wind speed optimized by the zero degree frosting model is selected as the frosting control parameter,the frosting phenomenon of the membrane heat exchanger will not occur during the whole winter operation.This study is expected to provide theoretical basis and optimization guidance for the design and application of membrane heat exchangers in cold regions.