Research On Frosting And Heat Recovery Characteristics Of Membrane Outdoor Air Heat Recovery System In Severe Cold/Cold Regions

As an important component of a building’s central air conditioning system,a fresh air system can provide a building with high quality indoor air quality and a comfortable indoor environment.However,the process of providing a comfortable indoor environment inevitably increases building energy consumption.Therefore,how to reduce the energy consumption of the new air system under the premise of achieving high quality indoor air quality is of great importance to the energy saving and emission reduction of the building.In severe and cold regions,when the temperature on the inlet side of the fresh air is low in winter,frost will occur in the heat recovery unit during heat exchange,and the heat exchange efficiency of the heat exchange unit will be greatly affected after frosting.Therefore,how the heat exchange efficiency changes after frosting and how to avoid frosting is an urgent problem for practical engineering and the focus of this paper.This paper begins with a brief explanation of the basic principles of heat and mass transfer in membrane type fresh air heat recovery systems,an analysis of the factors affecting the exchange efficiency of membrane type fresh air heat recovery systems and the performance evaluation indexes of membrane type total heat exchangers to facilitate subsequent research.Secondly,a test rig for a fresh air heat recovery system was set up,and the main components of the experimental system and the design of the system were introduced.In order to ensure the accuracy of the experimental data,the air leakage rate,temperature and humidity as well as the air velocity of the whole experimental system were tested and the error analysis was carried out.Then,the frost characteristics of the membrane type fresh air heat recovery system under low temperature conditions in winter are analysed.The location of frost in the membrane heat recovery unit is tested and the concept of cold angle is proposed.The actual frost point temperature and frost location where frost first occurs under different operating conditions are obtained by setting up different operating conditions.Finally,the influence of indoor temperature,indoor relative humidity,outdoor fresh air temperature and wind speed on the sensible heat exchange efficiency,latent heat exchange efficiency and total heat exchange efficiency of the membrane type fresh air heat recovery system under different working conditions is analysed.