| In the complex and diverse field of building energy conservation,it is one of the important ways to keep the indoor environment comfortable and save energy to use some excellent envelope structures in the building,and to ensure the good performance of its thermal performance in the service cycle of the building.Based on this,this paper discusses the heat transfer characteristics and condensation in long-term maintenance of the enclosure in hot summer cold winter areasFirst of all,the heat transfer characteristics of enclosure are closely related to its thermal performance,so a good thermal performance test method is very important.At present,there are many problems in the current detection methods,such as large deviation between the laboratory and the actual measurement results,cumbersome and heavy instruments,limited measurement environment in hot summer cold winter areas,and low accuracy Therefore,this paper proposes a Balance Correction Test method based on double-sided heat flow meter to improve the current form of thermal performance test.In this paper,the method is verified by four kinds of test conditions.The results show that:(1)For the envelope structure of steady-state heat transfer process and one-way unsteady-state heat transfer process,the error of the Balance Correction Test method can be very small,is 6.48%,5.56% and 5.8% respectively,the accuracy is much higher than the traditional single and double-sided heat flow meter method;(2)For the two-way unsteady heat transfer process,there is a large error about 75.38%.This is because: in the process of heat transfer,there are a lot of points with opposite direction and numerical value of heat transfer,and the internal heat transfer of the wall fluctuates violently,which seriously deviates from the premise of "one-dimensional steady heat transfer".But it is still better than the traditional method’s error about 109%.Furthermore,it is proposed that the scheme of calculating thermal resistance with dominant heat flow can reduce the deviation to 7.69%;(3)The time-by-time thermal resistance curve calculated by this method fluctuates smoothly in any period and solves the real value more,so the measurement time and calculation period can be shortened.In conclusion,this method can calculate the thermal resistance of the enclosure effectively,quickly and stably.Secondly,In the long-term use of building envelope,condensation will have a serious impact on its heat transfer characteristics,especially in hot summ er and cold winter areas.The existence of this phenomenon will not only damage the thermal performance of the wall itself,but also seriously affect the health of indoor residents.Therefore,this paper proposes a simple algorithm for the comprehensive co nvective heat transfer coefficient of indoor surface in the hot summer-cold winter area,taking this as the boundary condition.we use CHAMPS-BES software to simulate the hourly temperature of three kinds of wall inner surface,take the most unfavorable temperature point and dew point temperature for comparison,get the condensation condition and indoor temperature control critical point,draw it in the enthalpy humidity diagram,and get the critical curve.The results show that:(1)A simple algorithm based on the cavity model can accurately calculate the comprehensive convective heat transfer coefficient of the inner surface;(2)No.1 wall is the most "healthy",followed by No.2 and No.3,t he better thermal insulation performance,the less likely enclosure is to condense,so even in hot summer cold winter areas,the thermal insulation facilities should be increased appropriately.(3)For the old buildings that cannot be retrofitted with energy-saving and heat preservation,the indoor temperature and humidity can be controlled to make them higher than the critical curve of condensation,so as to reduce the risk of condensation on the inner surface of the enclosure.To sum up,the conclusion and method are helpful to reduce the condensation on the inner wall of the building in production and life. |
PDF Full Text Request