Studies on a pressurized type under-floor air conditioning system. (Analysis of governing factors for uniform air velocity profile.)

Recently, a lower type free-access floor system which realizes improved ease of walking and less sense of confinement has been attracting attention. However, it is known that the lower the design of the air supply chamber, the larger the non-uniformity of the diffuser air velocity profile and the greater the deterioration in room temperature distribution. In this paper, an analytical model is proposed for predicting the non-uniformity of diffuser air velocity at the design stage. The validity of the analytical model was confirmed by the good coincidence of results obtained in scale model experiments. It was found that the limit of the floor height at which a uniform diffuser air velocity is obtained was 50 mm. Moreover, a relation was found whereby the inverse of coefficient of resistance at a diffuser up to a value of 1 is proportional to the maximum non uniformity. This indicates the possibility that design work aimed at constructing a pressurized type under-floor air conditioning system with a uniform air velocity profile from diffusers may be readily performed from parameters of the coefficient of resistance at a diffuser by utilizing this relation.