Thermal radiation inside a single span greenhouse with a thermal screen

Abstract

A model is offered which yields the net thermal radiation at the ground of a single span greenhouse fitted with thermal screens, in terms of the outside radiative environment, the properties of the cladding and screening surfaces and the temperatures of the ground, screen and covering. Radiation is assumed to be diffusely emitted, transmitted and reflected, both by the cladding and the screening surfaces. The importance of the geometry and temperature of the screening surface, and of the radiometric properties of the screen in determining the radiative environment inside are indicated. On the basis of this model, together with the outside radiation fluxes, temperature of the ground, screen and cover and data on the properties of the cladding and screening surfaces, the net thermal radiation inside the greenhouse can be determined, both in clear and overcast night sky conditions. These results are found to be in fairly good agreement with the measured net thermal radiation at ground level inside the greenhouse.