Selection Of Heat-collecting Media For Solar/air Energy Combined Drying And Analysis Of Energy Consumption Of Poplar Drying

Wood solar drying is one of the main drying methods of clean,green and energy-saving energy.Since the main system(solar heat collector system)of the wood solar combined drying equipment is not only affected by the heat collection/storage medium but also by the region and season,the current wood solar drying system is mainly used in tropical regions.Therefore,In order to solve the limitation that wood solar combined drying equipment is only used in tropical regions,the heat collection/heat storage medium of the wood solar drying system can adapt to the seasonal characteristics of high latitudes(Harbin,China)is an important factor that should be promoted.The selection of the heat collection/storage medium across seasons is very important.At the same time,the energy consumption of the equipment can reflect the cost-effectiveness of the wood solar drying equipment,provide research directions for the improvement of the equipment,and provide a theoretical basis for the wood solar air drying method.In this study,electrothermal method and cooling method were used to conduct simulation experiments on the selection of heat-collecting medium across seasons.The corresponding temperature parameters of the selected heat-collecting medium during the poplar drying process were matched to select a suitable heat-collecting medium;the wood solar/air energy combined drying equipment was used to dry poplar sawn timber,and the verification of the media selection scheme was studied;By testing the performance parameters of the heat collection system and air source heat pump during equipment operation,and analyzing the energy consumed by the equipment during the drying process of poplar wood,the energy consumption of the equipment is analyzed and tested.The main research contents and results are as follows:(1)The heat collection and heat storage of three common industrial media under different environmental conditions were tested by the electrothermal method and the cooling method.The results shown that when the ambient temperature was-10?,ethylene glycol aqueous solution(W-EG)was the best heat-collecting medium.The heat collected by W-EG was 109.3%more than heat transfer oil(THO),and the thermal efficiency(?)was 91.1%higher than that of THO.When the ambient temperature was between 5 and 35?,water(W)was the best heat collection medium.At-10?,the KO value of THO was 106.1%of W-EG.At the minimum value,when the ambient temperature was 20?,the K0 value of W was the largest and the K value of W-EG was the smallest.W was 124%of W-EG.Therefore,in late autumn,winter and early spring,W-EG was the best heat collection/storage medium.In the late spring,early autumn and summer,W was the best heat collection medium,and W-EG was the best heat storage medium.(2)By drying the 35mm poplar sawn timber,the heat required by the poplar sawn timber at each drying stage was calculated according to the parameters involved in the drying process,and according to the required heat,calculated the temperature that the selected medium should reach in each stage of the poplar drying process.·The results shown that under winter conditions,when poplar sawn timber was dried to a moisture content of 15%or less,W-EG need to reach a maximum temperature of 77.2?;when the working environment temperature of the medium W was satisfied,the minimum heat collection temperature need 50.5?,and the highest need 75.5?;The highest heat collection temperature of THO was 82.8?,which can meet the temperature parameter conditions for drying poplar sawn timber.(3)Through the selection and verification of the heat collection medium of the solar/air energy combined drying equipment,the performance test of the system,and the energy consumption analysis of the poplar drying process,the heat collection test and air energy performance test were performed on two kinds of heat collection media,water and antifreeze.The results shown that under the conditions of an average ambient temperature of 11.9? and an average solar radiation value of 812.2 W/m 2,the average heat collection efficiency of water was 61.02%,the antifreeze was 22.04%,and the average heating coefficient of air was 3.44;based on this,drying experiments on 25 mm thick poplar were carried out using solar/air energy combined drying with water as the heat-collecting medium.At an average ambient temperature of 24.3?,the moisture content of poplar fell from 40.24%to 9.79%,and the energy consumption per unit volume was 39.25 kWh/m3.Compared with the energy consumption of 472.36 kWh/m3 per unit volume of conventional drying of poplar,the combined solar/air energy drying had obvious energy saving effect.