Micro-climatic environmental conditions inside a greenhouse with a built-in solar distillation system

A numerical study was carried out to investigate the micro-climatic environmental conditions inside a greenhouse– distillation system, self-sufficient for irrigating water. The greenhouse consists of the planting cavity, circulating air channels and roof solar distiller for the production of a rather modest rate of irrigating water. A turbulent, steady-state flow, energy and humidity concentration equations were solved using the numerical code FLUENT 6.1. Velocity vectors, steam function, isotherms and temperature and humidity distribution inside the greenhouse present the resultant micro-climatic environmental conditions. The results are presented for hot days where cold and humid air (from the evaporative cooler) enters the greenhouse from one side and is circulated through the partially porous cavity (representing the plants) and flows through air flow channels and leaves from a vertical thermal chimney. The results show that, with the selected inlet flow conditions, the flow velocity, temperature, and relative humidity can be within the comfort values for plant growth. The effect of some important environmental, design, and operational parameters on greenhouse micro-climatic conditions has also been highlighted.

1. A numerical simulation of the steady-state turbulent flow, temperature and humidity distribution inside an agriculture greenhouse with a built-in solar distillation system is presented. The micro-climatic environmental condition results are presented for the pre-construction of an integrated GH–still system. The results are presented for hot days where cold and humid air (from an evaporative cooler) enters the GH and leaves through a partially porous cavity (repre- senting the plants), to flow channels and a thermal chimney. 2. Turbulent flow, energy and humidity concentration equations were solved using the numerical code FLUENT 6.1. The results are presented in the form of velocity vectors, stream function, isotherms and humidity and mass fraction contours. The developed computer package proved to be an effective tool for the study and analysis of the micro-climatic conditions of a preconstructed GH–still system for optimum plant growth. 3. With the selected inlet flow conditions, the flow velocity, temperature, and relative humidity were found to be within the comfort values for plant growth. 4. The effect of some important environmental, design, and operational parameters on GH micro-climatic conditions and economics were analyzed. The GH can accept harsher environmental conditions that make its wall temperatures and inlet air temperatures 10°C higher those given in Table 2. The inlet velocity should not decrease below 0.5 m/s to avoid recirculating vortices that increase the RH within the plant growth zone to unacceptable values.