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In this study, the effect of a change in height on the heat flux distribution from a single-stage radiant tube heater (RTH) on a floor was investigated. Experimental measurements and numerical simulations were performed for various heights ranging from 12 to 15 ft (3.66 to 4.57 m). The RTH had a firing rate of 200,000 Btu/h (58.63 kW) and a tube length of 70 ft (21.34 m). The maximum and average heat fluxes were found to decrease with increasing height. The results also show a good match between the experimental data obtained and the numerical results generated using computational fluid dynamics (CFD). Thus, the numerical predictions can be used with confidence to predict the heat flux for wider coverage areas on the floor.

In addition, a heat flux zone between 31.69 and 63.40 Btu/hxft2 (100 and 200 W/m2) was studied. This heat flux region will help to determine the thermal comfort zone in combination with other comfort parameters, such as the metabolic rate and air draft. This heat flux zone increases with increasing height; thus, placing the heater at high levels above the floor will lead to a wider coverage area for the same heat flux.

Citation: ASHRAE Transactions -- Volume 119, Part 2, Denver, CO.