Thermal mass, including the building envelope, the interior partition, the furnishing, or even the air inside a building, is defined as the mass that can store thermal energy (heat or cooling energy). For storing heat in buildings, there are two important thermal properties of the materials need to be considered, i.e. the heat capacity by volume and the heat-absorption rate. The first property determines the ability of the element to store thermal energy, and the second property determines the ability of the element to conduct the thermal energy. The combined convective and radiative heat transfer coefficient and the surface area of the thermal mass determine the rate of heat transfer between the thermal mass element and the air. One of the good examples in using thermal mass is the night cooling, which can avoid or minimize the need of mechanical cooling in buildings. We present a simple design formula for use by architects and engineers which involves only three design related parameters, i.e. the time constant of the system, the dimensionless convective heat transfer number and the Fourier time constant. The present method allows the fast determination of the amount of thermal mass as well as key design parameters when the phase shift of indoor air temperature and the attenuation of the indoor air temperature fluctuation are specified.
Dr Y. Li is an Associate Professor of the University of Hong Kong. He graduated from Shanghai Jiaotong University and Tsinghua University. He obtained his Licentiate and Ph.D. from the Royal Institute of Technology, Sweden. He was a Principal Research Scientist in CSIRO, Australia, and led and managed the CSIRO Ventilation and Indoor Environments team from 1997 to 2000.
He was a Subtask Leader in the IEA Annex 35 Hybvent project between 1998 and 2000. He is a guest/adjunct professor in the Hybrid Ventilation Center of Aalborg University, Denmark, Shanghai Jiaotong University, Hunan University and the Seasky Scholar Visiting Professor at Dalian University of Science and technology. He received the HKU Outstanding Young Research Award in 2003. He is an editorial board member of Indoor Air, Indoor & Built Environment, and International Journal of Ventilation. He is a member of ASHRAE and ISIAQ.
His research interests lies in the interface areas between fluid dynamics, indoor environments and health. His current research topics include bioaerosols, engineering control of infectious diseases including SARS, natural ventilation, and building energy efficiency.
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