著者

安富 善三郎 宮井 善弘

出版者

公益社団法人 空気調和・衛生工学会

雑誌

空気調和・衛生工学会 論文集 (ISSN:0385275X)

巻号頁・発行日

vol.1, no.2, pp.65-73, 1976

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The function of the air curtain is to suppress the transfer of heat, moisture, dust and smoke through the open doorway. This paper presents both experimental and theoretical investigations on the effect of the cross-flow of the two-dimensional air curtain. Flow Patterns The fluid flow in the neighbourhood of the curtain jet for various cross-flow coefficient α (α=discharge flow at the atmosphere side/nozzle flow) is visualized by water tank experiments with mixing oil particles to the jet fluid flow. This oil particle is made from n-Butyl phthalate 81%, Kerosene 19%, so that the density is as same as water. The interesting results are as follows. (1) As cross-flow coefficient α increases, the flow of the curtain jet divided into the atmosphere side increases, (i.e. its case is called as nonequilibrium condition of jet). (2) In the special case, i.e. α=0, all flow of the jet is forced into the suction side, so that its case is called as equilibrium condition. (3) When we deflect the curtain jet to the suction port side, the value of α becomes gradually small. The free stream which flow out at the atmosphere side, finally passes through beneath the curtain jet, and then the value of α becomes negative. We may call its case as also non-equilibrium condition. (4) The cross-flow region is subdivided into two parts. The first of these is a small region adjacent to the curtain jet, and turbulent diffusion of the cross-flow is dominant in this region. The second region lies between the diffusion region and the atmosphere or the suction port, and the flow in its region behaves like the channel flow, so that its region is termed channel flow. Pressure Characteristics The static pressure distributions on the floor wall and the cross-flow rate have been measured. The pressure of diffusion region are lower than that of channel flow region, in which the pressure seems to be uniform upward. As cross-flow coefficient α decreases, the pressure of channel flow in suction side decreases. In the case of the equilibrium, the pressure difference between the atmosphere side and the channel flow region is from 50 to 70% lower than that between the atmosphere side and the diffusion region. Analysis The curtain jet of the non-equilibrium condition can be classified into two flow patterns; a stagnation point exists floor, or not. Simple flow models for the jet, diffusion and channel flow regions are proposed. And a theoretical analysis is carried out by using the momentum theory around the curtain jets at the equilibrium and non-equilibrium condition. Pressure differences are calculated for several cross-flow rates. The calculated results agree fairly well with the experimental results.