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MODELING THE THERMAL AND INDOOR AIR QUALITY PERFORMANCE OF VERTICAL DISPLACEMENT VENTILATION SYSTEMS Makoto Koganei'~2 , G. Thomas Holbrook2 , Bjarne W. Olesen2, James E. Woods2 'Research & Development Center, Asahi Kogyosha Co., Ltd., Japan Ztndoor Environment Program, Virginia Polytechnic Institute & State University, U.S.A. SUMMARY Two zone modeling of vertical dispiacement ventilation was performed assuming piston flow in the clean zone, uniform mixing in the dirty zone, and no recirculation between the zones except via heat source plumes. The resulting equations for air change effectiveness and contaminant removal effectiveness more closely match observed vertical displacement ventilation performance than previous studies. METHOD I) piston flow in the lower "clean" zone and uniform mixing in the upper "dirty" zone 2) recirculalion between Ihe zones does not occur except via heat source plumes V,.,+V1.:+V" +•••=V RESULTS V~ eV Schematic of two-zone model Mass Balance Equations Air Change Ntfectireness Contaminant Removal Effectiveness V,(d(:,/dl) =V(:,(0) - VC,((); (0 < t < VJV) V,(d(',Idl) = -V(:,(U; (V~V < t < o°) e, = t,/<t> = 2/11 + (Vi/V)'i Piston no.. ~ (-uokPk~ tmiaioR 0 Vt/V I Air change effectiveness VC=+ N, + N, = VC, VC~,+ N= = VC, + N2 Cw = (t-F.)(1-6)C~+ (1-e,)QC, + (N.IV) for lhe simple case where C, = 0, N, = 0, e, = 0 and a = 1: t:''= CM-)I<C(-)> = (:,/((C,V, + C=V=)/V) = 1/(V,/V) Contaminant removal effectiveness where V,/V is a function of flow rate, diffuser type, heat load, height, supply air temperature (see Equation 14-16). CONCLUSIONS Il Fundamental characteristics of displacement ventilation systems are more realistically simulated by including consideration of N heat load, room ventilalion„and system conditions (e.g. outside air ratio, air cleaner location and efficiency, total heal load, 111111111 supply air now rate, etc.) CA 2) For system design and evaluation purposes, ii is necessary to know lhe now rate (diffuser type), heat load(heighl). supply air 041 temperature. It is unnecessary lo know the delaiis of llie plume llow condiliuns. ~ ACKNOWLEDGEMENTS ~ Wc are pleased to acknowledge llie partial support of Philip Morris, USA and Asahi Kogyusha ('o.,, l.td., Japan fur this study. W