Temperature Regime and Heat Transfer in a Glasshouse at the Daytime

Characteristics of the temperature regime and the heat transfer in ventilated and unventilated glass-houses at the daytime were studied by using numerical technique based on the shooting method described in a previous paper (UCHIJIMA and IWAKIRI, 1970). The results obtained can be summarized as follows: 1. Temperature profiles in the unventilated glasshouse under daytime conditions with higher net radiation were characterized by iTs>iTw>oTw>oTa, where iTs, iTw and oTw are temperatures at the floor surface, at the inner and outer surfaces of glasswall, respectively and oTa outside air temperature. Influence of the dryness of air was strongly marked on the temperature at the floor surface (see Fig. 1). Although the difference in wall temperature between dry and wet houses was about 0.5°C at most, the floor temperature in the dry unventilated house was higher by 10 to 20°C than that in the wet house. 2. The following relations were obtained from numerical experiments between temperature excess (ΔT=iTa-oTa) of the unventilated glasshouse and net radiation (iS), area ratio (R=As/Aw) and transfer coefficient (ih, oh), ΔT=iS(a+bR), ΔT=αH-β+γ, where As is floor area (cm2), As wall area (cm2), H=oh⋅104 heat transfer coefficient (1y/sec°C) and a, b, α, β and γ are experimental proportionality constants. The temperature excess increased in proportion to the net rediation. A similar net radiation dependence of the temperature excess was also obtained from our experiments made in an unventilated glasshouse (see Fig. 5). Dependence of temperature excess on sensible heat transfer coefficient was approximated by a hyperbolic formula (see Fig. 7). The values of proportionality constants α and β did not vary with dryness, indicating that the shape of hyperbolic curves was independent of dryness. The asymptotic values of each hyperblic curve decreased with increasing heat transfer coefficient. 3. By making reasonable assumptions, the heat balance equations of a ventilated glasshouse are expressed by Es=iqs+ihr(iTs-iTw), for floor surface λ/d(iTw-oTw)=ih/2+Rihr(iTs-iTw) for inner surface of glasswall λ/d(iTw-oTw)=fFo+(fohr+oh)(oTw-oTa), for outer surface of glasswall where Es=(1-ia)τt(Q+q)0-iBs, iqs=ih/1+R[(iTs-iTw)(1-had/2ih)+had/ih(iTs-oTa)], Es and iqs denote respectively the effective heat source and the sensible heat flux at the floor surface (ly/sec). The temperatures (iTs, iTw, oTw) in the above equations are numerically determined by the shooting method on an electron