Improved heating-element configurations for a tunnel oven

Natural convection within a 1700 mm horizontally long, 350 mm× 350 mm square cross-sectioned oven, containing a symmetrically-positioned square-sectioned inner body, has been measured. Attention was focused on the effects that three heater configurations have on the steady-state rate of heat transfer to the rectangular-sided, 175 mm× 175 mm square cross-sectioned inner body. The radiative fluxes to each of the inner-bodyʹs surfaces have been calculated for the different configurations, using a multi-zone radiation model. Evacuating the enclosure permitted the convective component of the steady-state heat transfer to be identified. Thence, an easily applicable empirical correlation, of the form was deduced for the natural-convection contribution. Overall, the proximity of the heating element to the inner body dictated the proportions of the rates of heat that are transferred by radiation and convection. For enhanced convective-heating, configurations with the heaters mounted along the lower section of the sidewall, are recommended.