Abstract
As an important factor in indoor human thermal comfort, the wind is investigated in the present study using a fully validated human body-environment interface model based on CFD technology. The three parameters of air speed (va, 0.5–2 m/s), turbulence intensity (TI, 5%–40%) and wind direction (0°–180°) were simulated to study their influence on the convective heat transfer coefficient (hc) at the surface of the human body. It was found that va influenced the value of hc more than TI. The influence of TI on hc reached a steady level when va was above 1.5 m/s; for example the greatest rate of change of hc at the head remained at 52% as the TI was increased from 5% to 40%. The wind direction had a noticeable influence on the overall hc when the va was above 0.5 m/s. A 90° wind (i.e. from the right side) gave a value of hc that was about 20% lower than wind from other directions, and led to an asymmetrical distribution of hc over the body surface. Locally, the wind direction did not influence hc at the head and feet, and influenced the central segments more than the limbs. Two regression equations for the correlations between hc and va, TI and wind direction were also generated and validated for continuous evaluation of hc. The resulting database of values for hc can be used in combination with the human thermoregulation models for thermal response prediction in built spaces with increased air speed.
Highlights
As a basic requirement for life, human thermal comfort is a constant focus of research in indoor environments and automotive cabin engi neering
A numerical human body-environment interface model for the study of heat transfer under windy conditions was developed. It was validated against measurements in a climatic chamber with a thermal manikin under the same environmental conditions (RMSD for va of below 0.4 m/ s, for ht below 3.4 W/(m2K))
The influence of turbulence intensity (TI) remains at a steady level when the air speed exceeds 1.5 m/s and forced convection becomes predominant; for example, the rate of change in the overall hc caused by an increase in TI from 5% to 40% remains at 42%. (2) The wind direction does not have any influence on the convective heat transfer from the entire body surface at a low air speed of 0.5 m/s, but becomes an influential parameter as the air speed increases
Summary
As a basic requirement for life, human thermal comfort is a constant focus of research in indoor environments and automotive cabin engi neering. The temperature of the indoor surrounding environment (air tempera ture and radiant temperature) and the air speed are the two most influential parameters, and are the most adjustable using indoor heating, ventilation and air conditioning (HVAC) systems for human thermal comfort. According to Newton’s law of cooling and the Stefan-Boltzmann law of radiation, the temperature of the surrounding environment affects both convective and radiative heat exchange be tween the human body and the environment. The air speed, which changes the airflow pattern around the surface of human skin, mainly influences convective heat exchange. To find a balance between energy consumption and human thermal comfort, plenty of experimental and numerical studies [9,10,11] have been conducted to investigate the rela tionship between the use of air-conditioning systems and human ther mal comfort, and have provided guidance on the design of air-conditioning and ventilation systems for occupational and residen tial spaces
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