The Frequency Domain Model And The Heat Transfer Function Model Of Exhaust Air Insulation Wall

One of the keys to saving the building energy is to reduce the cold/heat loss through the building envelope.The exhaust air insulation wall belongs to a new type of building structure,which contains a core layer of porous material,through which the indoor air con-ditioning is discharged to the environment.The cold loss through the building wall can be reduced and building energy thus can be saved as a result of that the heat passing through the wall to the room can be taken away by utilizing the low-grade cold energy of the exhuast air.The exhaust insulation wall has great energy saving potential.In order to make the heat transfer simulation and load calculation for the exhuast air insulation wall more convenient and accurate and to establish a good foundation for subsequent research,it is necessary to study the heat transfer calculation model.In this dissertation,the frequency domain model and heat transfer function model are studied,and the thermal characteristics of the exhaust heat insulation wall in the frequency domain are analyzed by using the frequency domain model.The contents of the main research chapters are as follows.In the second chapter,based on the frequency domain finite difference method and the harmonic assumption,the frequency domain model is established for the basic type and the interlayer type of the exhaust air insulation wall,which can be applied to four types of exhaust heat insulation walls(basic,internal panel,interlayer ventilation,external insulation).The third chapter compares the frequency domain model with the existing numerical model and experimental data to verify the correctness of the frequency domain model.The results show that the difference between the result of frequency domain model and the result of numerical model is only within 1%,and the error of frequency domain model relative to the experimental data is also small,indicating that the frequency domain model and the existing numerical model have basically the same accuracy,and the frequency domain model is correct.In the fourth chapter,the exhaust air insulation wall’s heat transfer function(G_X(s),G_Y(s),G_Y′(s),G_Z(s))can be derived from the heat transfer control equation by using the Laplace transform.In order to verify the correctness of the heat transfer function,the fre-quency domain thermal response characteristics obtained by the heat transfer function and the frequency domain model are compared.The results show that the frequency domain ther-mal response characteristics obtained by the two methods are very close,and the four heat transfer functions of the exhaust heat insulation wall(including basic type and interlayer type)are relatively correct.In the fifth chapter,the effects of parameters of porous layers(penetration speed,thick-ness,porous layer material)on the thermal characteristics in the frequency domain and the different characteristics of four types of exhaust air insulation wall were analyzed by using the frequency domain model.The results show that while the permeation speed or the the thickness of the porous layer increase,or the thermal conductivity of the porous material decrease,the thermal insulation properties of the exhaust air insulation wall are improved.Among the four different types of exhaust insulation walls,the external insulation type per-forms best.