| With the development of national economy,the requirement of energy saving and emission reduction is higher.Due to high temperature and humidity in hot and humid areas,cooling energy consumption is huge in summer.As an energy-saving and commonly used tool in hot and humid regions,electric fans promise an indoor cooling effect with lower energy consumption.This makes the exploration of airflow utilization significative.The flow field characteristics of floor fan which is the foundation of creating comfortable airflow is rarely studied in the preliminary study.Study on floor fan in high humidity environment is of great significance to the application of floor fans in hot and humid areas.It is worth exploring whether the periodic fluctuating airflow can improve the discomfort caused by long-time blowing.Therefore,this paper studies the above problems by studying the flow field characteristics of floor fans and conducting human thermal comfort experiments.First,the characteristics of steady air supply field of floor fan are analyzed.The flow field distribution is different from that of the general orifice jet because of the shield of the fan.Different wind speeds have different flow field characteristics.With the increase of wind speeds,the entrainment capacity increases and the wind speed attenuation increases.The turbulence intensity field distribution under different gears is similar.The axial turbulence intensity is around 10% and the turbulence intensity away from the axis is around 45%.The influence of fan gear on human thermal comfort is mainly reflected in the difference of wind speed.Besides,experiment has been carried out to study the influence of airmovement of floor fan under different wind speeds on human thermal comfort at relative humidity of 50%?70% and 90% and background temperature of 28??30? and 32?.In order to know the parameters of ventilation when people get the best comfort,so there are three levels of air supply speed.The results of climate chamber experiment identified acceptable limit of indoor temperature and humidity to use floor fans is 30?/70%.Through the regression analysis of the whole thermal sensation and the whole airmovement sensation,the comfort interval is given,when TSV and ASV in the range of-0.5 ~ + 0.5 at the different background temperature and humidity,which is provided a reference for the design of the floor fan in the hot and humid environment.The second part of the article is to study the influences of the fluctuating period to the subject's thermal reaction.The dynamic characteristics of constant airflow?airflow of oscillating fan and 10s?30s?60s and100 s sinusoidal flows were studied.The results show that the turbulence of oscillating fan'airflow is the bigger than that of constant airflow and sinusoidal flows.The ? values of sinusoidal fluctuating airflow with a period of 60 s were the highest which is more than 1.1,while the values of other airflows were all less than 1.1.Airflow of oscillating fan has obvious skewness distribution and the proportion of small wind speed is the largest.A total of 20 subjects participated in the thermal comfort experiment at 30?/70% and results were analysed.Different fluctuating periods(10s,30 s,60s and 100s)showed no significant difference in thermal sensation,air movement perception and perceived air quality.60 s sinusoidal flows with 1/f fluctuation similar to natural wind is more acceptable than other airflow.Besides,subjects prefer constant airflow at the beginning.As the blowing time increases,subjects are more inclined to sinusoidal flows and airflow of oscillating fan.From what has been discussed above,with reasonable utilization,floor fans could provide a healthy and energy-efficient way to control indoor environment. |
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