A horizontal 1-m-square plate electric heater dissipates heat to the atmospheric air at 25oC. The power of the electric heater is 0.5 kW and the average surface temperature of the heater surface is 85oC. Air is forced over the heater surface to transfer a large amount of heat into the air. What should be the air velocity to remove the heat from the heater? Now suppose the heater also radiates like a black surface to surroundings at 25oC? What air flow velocity is required to remove heat from the heater in this case?

A horizontal 1-m-square plate electric heater dissipates heat to the atmospheric air at 25oC. The power of the electric heater is 0.5 kW and the average surface temperature of the heater surface is 85oC. Air is forced over the heater surface to transfer a large amount of heat into the air. What should be the air velocity to remove the heat from the heater? Now suppose the heater also radiates like a black surface to surroundings at 25oC? What air flow velocity is required to remove heat from the heater in this case?