多层覆盖连栋温室热环境模型构建

Thermal model of multi-span greenhouses with multi-layer covers

建立了多层覆盖连栋温室的温、湿度动态机理模型,定量描述了温室内的对流换热、土壤热传导、太阳辐射、长波热辐射、植物蒸腾、地面蒸发、水汽凝结、机械通风和自然通风等物理过程,根据质能平衡原理,对覆盖材料、室内空气、作物、土壤等建立了质能平衡方程。在给定的边界条件下,通过求解质能平衡方程,可求得室内温、湿度和各组成部分如覆盖材料、土壤、植物等的温度以及各部分间的能流、蒸汽流密度。利用有效辐射的概念,推导出了内外遮阳幕、内外覆盖材料、作物冠层、地表、室外天空之间的辐射热交换计算方法。利用压力分布法,推导出了具有顶窗、侧窗和湿垫等多个通风口时的风压和热压通风量计算式。与其他研究者提出的温室环境模型相比,本模型具有更为广泛的适用性。

A dynamic greenhouse thermal and humidity mechanism model for multi-span greenhouse with multi-layer covers was developed in this paper. The model describes the physical processes such as convection, conduction in soil, solar radiation, long-wave thermal radiation, transpiration, evaporation and condensation on covering materials, natural and mechanical ventilation that govern the thermal environment of greenhouses, and establishes mass and energy equilibrium equations of covering materials, indoor air, plant and soil. By resolving these equations, this dynamic model can be used to predict the indoor temperature, humidity, energy and steam flux density among greenhouse components, such as covering materials, soil, plant and so on, when boundary condition is determined.A procedure that is able to calculate radiation heat exchange among internal and external curtains, internal and external covering materials, plant canopy, ground surface and sky is deduced based on the concept of net radiation. Using pressure distribution method, a formula is put forward to calculate the ventilation of greenhouse equipped with multi-ventilation inlets such as roof windows, side windows and wet-pads under wind pressure and thermal pressure.Comparing with previous models developed by other researchers, the model presented in this paper has wider range of application.