An engineer is designing a heating system that will consist of multiple tubes placed in a duct carrying the air supply for a building. She decides to perform preliminary tests with a single copper tube of 2-cm OD carrying condensing steam at 100°C. The air velocity in the duct is 5 m/s, and its temperature is 20°C. The tube can be placed normal to the flow, but it may be advantageous to place the tube at an angle to the air flow and thus increase the heat transfer surface area. If the duct width is 1 m, predict the outcome of the planned tests and estimate how the angle θ will affect the rate of heat transfer. Are there limits?
