The Impact of Overhead Heating System Height on Greenhouse Air Temperature, Air Movement, and Canopy Temperature

Abstract

The effects of a movable heating system on distribution and uniformity of air temperature, air movement, and canopy temperature were studied in a greenhouse. A movable heating system consisting of hot-water pipes was placed over the top of the plant canopy at six different heights (0.25, 0.5, 0.75, 1.0, 1.25, and 1.45 m) and compared with a fixed overhead heating system placed 1.6 m above the top of the plant canopy. The movable heating system influenced the distribution and uniformity of the air temperature in the greenhouse. The change in temperature distribution was closely related to the position of the heating pipes. The movable heating system increased the air velocity near the plant canopy when placed at the two lowest positions, but at higher positions air velocity was similar to that measured for the fixed overhead heating system. The leaf temperature was correlated with air temperature but was not influenced by the position of the movable heating pipes.