Determination of overall heat transfer coefficient for greenhouse energy-saving screen using Trnsys and hotbox

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 U-values (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. • A new methodological approach for determining thermal screen properties is proposed. • TRNSYS model and hotbox are useful for thermal screens performance evaluation. • This study evaluated the U-value of single and multilayer thermal screens. • Low IR transmissivity and permeability enhance thermal screen effectiveness. • Airflow property impacted on the prediction of greenhouse heat load with thermal screens.