Experimental and Theoretical Study on the Heat Transfer Coefficients of Building External Surfaces in the Tropical Island Region

Yaping Cui,Jiaping Liu,Jingchao Xie,Peng Xue

doi:10.3390/app9061063

Yaping Cui, Jiaping Liu + Show 2 more

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https://doi.org/10.3390/app9061063

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Journal: Applied Sciences	Publication Date: Mar 13, 2019
Citations: 7	License type: CC BY 4.0

Affiliation: Beijing University of Technology

Abstract

China is actively promoting ocean territory construction, and how to design low-energy buildings to fit the unique climate of tropical island regions has received much attention. The heat transfer coefficient of a building external surface plays a vital role in calculating air-conditioning load accurately. To obtain reasonable heat transfer coefficients in the tropical island region, this study introduced a naphthalene sublimation experiment to conduct full-scale measurements on convective heat transfer coefficients (CHTCs) in the tropical island region, and proposed a simplified calculation model of evaporative heat transfer coefficients (EHTCs). Results indicated that the function expression between CHTC and wind speed was CHTC = 5.56 + 4.48u (R2 = 0.94), and it was validated to be reliable. Furthermore, compared with CHTCs and radiation heat transfer coefficients (RHTCs), the EHTC had a wider changing range, owing to rainfall effects. Moreover, whether evaporation was considered or not, the difference of total heat transfer coefficients (THTCs) on building external surfaces was 5.2 W/(m2·K) for the whole year, so evaporation cannot be ignored directly. Additionally, THTCs with consideration of evaporation in winter and summer were 33.4 W/(m2·K) and 38.9 W/(m2·K) severally, which are much larger than the recommended values in the Chinese standard. This study would make up for the lack of surface heat transfer coefficients in energy conservation design of tropical island buildings.

Highlights

During the past 50 years, tropical island building construction in the South China Sea has been faced with two problems: Extremely scarce conventional building materials and very difficult energy supply
The convective heat transfer coefficients (CHTCs) testing days and sample size of the naphthalene sublimation experiment were fewer. This would not affect the reliability of the CHTC model, because the data used to obtain the correlation between CHTC and wind speed were from 8 November and 9 November 2016, and the weather on the two days was sunny and had a certain representativeness
The CHTC predictive model was examined by comparing the predicted CHTCs under measured wind speeds and the measured CHTCs on 19 August 2016, and the percentage errors were all less than 5% for the different verification groups, the mean percentage error (MPE) was merely 2.50%

Summary

Introduction

During the past 50 years, tropical island building construction in the South China Sea has been faced with two problems: Extremely scarce conventional building materials and very difficult energy supply. Studying building energy conservation in tropical island regions is urgently imperative [1,2,3]. On the one hand, compared with the Chinese inland area, the climate in the tropical island region situated in the South China Sea is exceedingly different, reflected in high temperatures, high humidity, intense radiation, high wind speeds, and strong rainfall etc. The current energy efficiency design standard performed in China is aimed at inland climates. Some design parameters in the current standard are not applicable for tropical island regions

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