DETERMINATION OF OVERALL HEAT TRANSFER COEFFICIENT FOR GREENHOUSE ENERGY-SAVING SCREEN USING TRNSYS AND HOTBOX
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Date
2022-03-08
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Biosystems Engineering
Abstract
The high energy consumption in the greenhouse during the winter season necessitates the development of various thermal screens for energy-saving purposes. However, there is limited data on the precise properties of thermal screens, while little research has investigated a methodological approach for measuring the screen's energy-saving capacity for
greenhouse energy efficiency. This research aims to determine the thermophysical, radiative, and aerodynamic properties of selected commercial greenhouse thermal screens. The transient system simulation (TRNSYS) model was used to simulate the heat flux and derive the thermal retention qualities of the thermal screens through their measured
properties. The model was validated by comparing the simulated and experimental heat transfer coefficients, expressed as the overall heat transfer coefficient (U-value), thereby, determining the thermal retention of the screens. In addition, the simulated U-value was compared to the experimental U-value in material permeability to investigate the influence
of screen porosity on heat loss. The statistical analysis t-test was conducted to compare the U-values obtained from the simulation and the experimental hotbox. The simulated Uvalues (for computed permeability) indicated that samples M1 and M3 exhibited the lowest U-value of 4.4 W m 2 K 1, while white polyester, Luxous, PH-super, PH-66, M2, Clima45 (0),
and New-Lux showed higher U-values of 82%, 105%, 161%, 123%, 41%, 102%, and 118%, respectively. Because of their low material porosity, M1, M2, and M3 samples showed better greenhouse thermal retention over others. Conclusively, the permeability features of the greenhouse energy screen materials have a substantial impact on their U-values.
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Keywords
Thermal screen; Permeability; Airflow; TRNSYS; Hotbox