Experimental Study on Fan-Induced Airflow Evaluation by Comparing the Power Spectrum, Turbulence Intensity and Draught Rate Methods

Abstract In hot climates a comfortable indoor environment is important. Mechanical fans are often introduced to cool the indoor air. However, it has been found that the airflow from such fans is not comfortable, especially compared with natural wind. Artificial airflow in an enclosure has been known to disturb hair, irritate eyes, and distract occupants. This paper presents the result of an experimental study on the characteristics of household airflow inducing appliances. The details of experiments carried out in the laboratory are described. Four kinds of common appliances were tested and two operating conditions were chosen. The power spectrum density function was used to evaluate the airflow dynamic characteristics. The preliminary conclusion shows that the power spectrum exponent is determined by the mean air velocity and the intermittence of the air velocity profiles. However, even mechanical airflow with dynamic characteristics such as shift and intermittence cannot exactly replicate natural wind. A small ratio of height to width of the fan airflow outlets is required so that more surrounding air can be involved in the flow, and more comfortable airflow is available for occupants.

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