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Researchs on the Effects of Moisture Content on Thermal Performance of Walls

Author: XuZuoZuo
Tutor: ZhanShuLin；MengTao
School: Zhejiang University
Course: Structural Engineering
Keywords: Since the insulation Porous building materials Effective thermal conductivity Heat transfer coefficient Moisture content Mortar joint thickness
CLC: TU111
Type: Master's thesis
Year: 2010
Downloads: 252
Quote: 3
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Abstract


, Hot summer and cold winter areas of the building envelope insulation system development and research in energy and building energy situation is of great significance. Most of the self-insulation wall materials belong to the scope of the moisture content of unsaturated porous media, the changes in the relationship between the effective thermal conductivity and moisture, lack of awareness of relevant norms. At the same time, existing research focused on the oven-dry state and wet saturated, and the moisture content of unsaturated porous media thermal conductivity is still lack of accepted experimental data and predictive models for the study of the thermal conductivity of unsaturated porous building materials less. To ceramsite enhanced aerated blocks, insulation mortar, ordinary mortar, for example, to carry out a theoretical and experimental study of the relationship of the effective thermal conductivity and moisture from the wall insulation materials, and to study the moisture content of the wall materials on the impact of the wall heat transfer coefficient. Also carried out a study of the the gray seam heat consumption preliminary test. Article will parallel conduction model, series model, the WM model is extended to a three-phase state, the moisture content of unsaturated porous media theory calculation of the effective thermal conductivity derived from the macro level, the effective thermal conductivity of the material moisture status and oven dry state thermal conductivity linked, to make it closer to the actual engineering. Theoretical calculated value curve of the measured value of the effective thermal conductivity of the three kinds of materials under different moisture state with three models were compared each trend and a suitable prediction model; fitted for the first time the Dow grain enhanced aerated blocks, the accurate calculation of the effective thermal conductivity of insulation mortar and mortar style; also discussed the impact of the presence of water on the stability of the test data, test the balance of time and the heat conduction plate moisture values. In this paper, the theoretical value of the wall heat transfer coefficient calculation try to adopt the thermal conductivity of the material the actual moisture state to replace the general material thermal conductivity values, given in the specification to improve the existing norms are ignored in the calculation of the heat transfer coefficient moisture content of materials a defect; envisaged by real-time changes in the moisture content of the material at the same time, to more realistic projection wall heat transfer coefficient, the detection and evaluation of wall thermal performance. The wall heat transfer coefficient of the test results found that the ceramsite enhanced aerated block wall heat transfer coefficient of the measured value is compared with the theoretical value is too large to determine the theoretical calculation of the value of the average correction factor of approximately 1.493. The higher the rate of the water content of the wall material, the higher the test value of the heat transfer coefficient. Test the moisture content of the test range (less than 20%), when every 1% increase in the average moisture content of the wall material, the # 1 wall (insulation mortar masonry, the thickness of the mortar joint 10mm) wall ( insulation mortar masonry mortar joint thickness 5mm), 3 # wall (ordinary mortar masonry, mortar joint thickness 10mm), 4 # wall (ordinary mortar masonry, mortar joint thickness 5mm) heat transfer coefficient in the original moisture content of the corresponding based on the value increased by 4.21%, 3.35%, 2.67%, 2.56%. The greater thickness of the mortar joint, the greater the growth rate of the heat transfer coefficient. The 1 # wall, # 2 wall # wall # wall mortar joint influence coefficient were 1.960,1.896,1.884,1.592. This study shows that the wall material moisture content is one of the determinants of the wall heat transfer coefficient, wall heat transfer coefficient is increasing with the increase in moisture, and moisture content, the design and calculation of the heat transfer coefficient should consider the impact. The detection and evaluation of the heat transfer coefficient is also quite possible by material moisture Road \The new self-insulation wall materials engineering practice self-insulation system, the research and development of low moisture absorption rate, or pay attention to the material moisture, control the moisture content of the wall materials can reduce moisture due to wall heat consumption . In the promotion of self-insulation wall materials, the use of supporting insulation mortar, reasonable control and selection of the thickness of the mortar joint, and help prevent the mortar joint thermal bridges caused heat consumption.

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