Research On Coupled Heat And Moisture Transfer Of Building Envelope

ABSTRACT:As an important aspect of building thermal design, heat and moisture transfer property of building envelope is well worth thorough studying, which is of obvious significance to improve the thermal insulation property and humidity resistance property of the building envelope.By employing CHAMPS-BES, a special software for heat and moisture transfer process simulation of building envelope, this thesis conducts a numerical simulation analysis on the initial liquid moisture content of most seen wall structures located in different climatic regions of building. The study covers four types of most seen wall structures------the sintered clay brick wall, reinforced concrete-EPS thermal insulation composite wall, hollow block-EPS thermal insulation composite wall as well as aerated concrete wall and includes the representative cities for four different climatic regions of building-----Beijing, Harbin, Shanghai and Guangzhou.This thesis studies on the moisture transfer and accumulation rules for building envelope, especially in the field how various initial liquid moisture content will affect the moisture equilibrium process. Then on the base of previous study, by studying the moisture transfer process's influence on heat transfer process of building envelope, the thesis presents the rules of building envelope heat transfer resistance variation given different moisture content and proposes a method to calculate the heat transfer resistance in moisture equilibrium situation according to the current heat transfer resistance. In addition, this thesis works out the time required for moisture equilibrium, moisture content for equilibrium and the total period of dew condensation for walls with different initial liquid moisture content. Also presented here are the rules how relative humidity and the quantity of condensed water of the air layer vary as time goes by.In the end, this thesis analyzes the influence of gaps between EPS boards and the air layer size on heat and moisture transfer property of building envelope and proposes the method of "control on gaps between EPS boards" to relieve the moisture accumulation and damage in EPS thermal insulation composite walls.