AN ESTIMATION METHOD FOR GREENHOUSE TEMPERATURE UNDER THE INFLUENCE OF EVAPORATIVE COOLING SYSTEM

Mohammad Hossein Shojaei̇,Kazem Jafari̇naei̇mi̇,Mohammad Mehdi Maharlooei̇,Hamid Mortezapour

doi:10.18186/thermal.930907

Mohammad Hossein Shojaei̇, Kazem Jafari̇naei̇mi̇ + Show 2 more

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https://doi.org/10.18186/thermal.930907

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Abstract

Temperature is one of the most important plant growth parameters that should be controlled in the greenhouses. The present study was aimed to assess the thermal behavior of a greenhouse with and without the fan and pad (FP) evaporative cooling system. A method was developed to approximate the greenhouse temperature based on the mass and energy balance equations. For this purpose, both of the fan and pad evaporative cooling system, and the greenhouse were studied. The results of the theoretical analysis were compared with those achieved by the experiments. Maximum deviations of 5.32, 5.56 and 4.53oC were observed between the theoretical and experimental temperatures of the inside air, the floor and the cover of the greenhouse without the cooling system, respectively. Whereas, the mean absolute error values associated with the predicted temperatures of the greenhouse with the FP system were ranged between 1.50 and 25.67%. Based on the obtained values for the correlation coefficient, root mean square error and mean absolute magnitude error, it was concluded that the models satisfactorily predicted the temperature of the greenhouse components. An air circulation system inside the greenhouse can be proposed to maintain the lumped condition even at the high temperatures, and lead to smaller errors. The results indicated that the inside air, the floor and the cover temperature of the greenhouse reduced by respectively 20.6, 13.0 and 20.6 oC when using the FP system with the air velocity of 4.4 ms-1 and the pad thickness of 6 cm.

Highlights

Due to recent developments in the greenhouse cultivation and off-season production in response to the population growth and the increase in living standards, there is an urgent necessity to provide the appropriate environmental conditions for plant growing in the greenhouse
The results showed that the greenhouse with 20-degree sloped roof indicated the best performance, in terms of energy reception and losses
The results showed that the obtained models for the greenhouse without the cooling system led to the maximum deviations of 5.3, 5.6 and 4.5oC respectively in temperature prediction of the inside air, the floor, and the cover

Summary

Introduction

Due to recent developments in the greenhouse cultivation and off-season production in response to the population growth and the increase in living standards, there is an urgent necessity to provide the appropriate environmental conditions for plant growing in the greenhouse. Energy consumed for ventilation, cooling or heating of buildings, which accounts for 25-40% of the total energy consumption, is mostly consisted of fossil fuels and nonrenewable fuels such as gas, gasoline, and kerosene [1, 2]. The prospect of ending global fossil fuel resources in the few decades along with the competition among the countries has led to the optimization of energy consumption as a strategic policy proposed by the economists and the governors throughout the world. A number of studies have been conducted to use renewable energies as the alternative or supplementary source of the fossil fuels in the greenhouse heating/cooling systems [3]. Some studies have assessed greenhouse structure and optimal greenhouse design for maximum solar energy absorption [4, 5]

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