Cooling efficiency of fogging systems for greenhouses
Cooling efficiency of fogging systems for greenhouses
复制标题
DOI：
10.1016/j.biosystemseng.2006.02.008
复制
发表时间：
2006-05-01
影响因子：
5.1
通讯作者：
Kozai, T.
中科院分区：
文献类型：
--
作者：
Abdel-Ghany, A. M.;Kozai, T.
目前用于雾化系统的湿垫和风扇系统的冷却效率eta（c）被定义为假设温室中的干球温度T-db、T-i低于外部干球温度T-db、T-o，并且直接在湿垫的出口处测量。然而，在雾化系统的eta（c）的情况下，通常在温室中的不同位置处测量T-db、T-i以获得平均值。在阳光充足的夏季条件下，室内空气主要通过传输到温室中的太阳能来加热。那么T-db，T-i通常高于T-db，T-o，给出负的eta（c）值。即使T-db，T-i低于T-db，T-o，由于增加到内部空气中的潜热，当前的eta（c）定义给出了不切实际的值。在这项研究中，新定义了一个雾化系统的eta（c），考虑到显热和潜热添加到温室空气。该定义基于在雾化操作期间温室中未冷却空气的能量和质量（水蒸气）平衡。测定了一个占地面积为26 m2的实验温室的eta（c）值，该温室包含150个盆栽番茄植株。温室以10 g（-1）的雾化速率间歇冷却，雾化时间分别为30、60和90 s，间隔时间分别为90、180和270 s。结果表明，60 s开、180 s关的雾化周期比其他周期具有较高的η（c）值。在此条件下，可以用两种近似式估算eta（c）值，误差小于± 5%。(c)2006年IAgRE。版权所有Elsevier Ltd.
The cooling efficiency eta(c) of wet pad and fan systems, which is currently used for fogging systems, is defined assuming that the dry bulb temperature in the greenhouse T-db,T-i is lower than the outside dry bulb temperature T-db,T-o and is measured directly at the outlet of the wet pad. However, in the case of eta(c) of a fogging system, T-db,T-i is typically measured at different locations in the greenhouse to obtain an average value. The inside air is sensibly heated mainly by solar energy transmitted into the greenhouse under sunny summer conditions. Then T-db,T-i is often higher than T-db,T-o, giving negative values of eta(c) Even though, T-db,T-i is lower than T-db,T-o, the current definition of eta(c) gives unrealistic values due to the latent heat added to the inside air. In this study, eta(c) of a fogging system was newly defined, taking into consideration the sensible and latent heat added to the greenhouse air. The definition is based on the energy and mass (water vapour) balance of the uncooled air in the greenhouse during the operation of fogging. The value of eta(c) was determined for an experimental greenhouse with a floor area of 26 m 2 and contained 150 potted tomato plants. The greenhouse was cooled intermittently at a fogging rate of 10 gs(-1) for three different fogging times of 30, 60 and 90 s with interval times of 90, 180 and 270 s, respectively. The results showed that a fogging cycle of 60 s on, 180 s off provided a relatively higher value of eta(c) than other cycles. Under this condition, two approximate expressions of eta(c) could be used to estimate the eta(c) value with an error less than +/- 5%. (c) 2006 IAgrE. All rights reserved Published by Elsevier Ltd.