Abstract
From the economical viewpoint in large indoor spaces such as factories and atriums, it is desirable to limit the air conditioned space to the specific area occupied. This paper analyzes about new local air conditioning system where the Coanda effect of a plane jet is utilized. When the plane jet is discharged from a slot horizontally into a half-confined space opening upward and at the opposite end, the jet is forced to curve and attaches to the floor, forming a cavity space covered by the jet. By applying warm or cool jet, we can use this cavity space for air conditioning. However when the warm plane jet is discharged, the Coanda effect does not usually occur by the influence of buoyancy. In this paper, first, we analyzed the trajectory of the warm jet, considering the effect of the pressure difference produced by the entrained air, so that we could find the critical conditions where the Coanda effect appears. As the results the critical condition, represented as a function of modified Archimedes number and denoted by K_c for the warm jet where the Coanda effect occurs, was identified as K_c=1.0k_p^<-0.96> (k_p: center line velocity constant). Secondly, we analyzed the air temperature difference between inside and outside of the cavity space by applying the characteristics of the free non-isothermal jet. Temperature difference ratio in the cavity is found to be represented as in the following equation. Δθ_i/Δθ_o≒0.90(H_s/k_ph)^<-1/2> Δθ_i, Δθ_o: temperature difference between cavity and room air, outlet and room air, respectively, h: slot width, H_s: height of slot location.
