Help: Air is heated through copper tubes, what is the length of the copper tubes?
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Help: Air with a flow rate of 5 m3/h is heated through copper tubes with an outer diameter of 12 mm. The air temperature rises from 10°C to 130°C. The copper tubes are in the form of coiled tubes and are submerged in heat transfer oil at 150°C. What is the required length of these copper tubes? Please provide the calculation steps, thank you.
5 cubic meters of air, approximately 6.5 kg/h flow rate, a temperature rise of 120°C; the heat generated is about 0.23 kW. With a heat transfer coefficient of 20, the required heat exchange area is 0.2 square meters. The flow velocity is set at 5 m/s. The length of the pipe is calculated as 0.2 square meters divided by (12 mm – wall thickness * 2); it’s roughly 25 meters
This post was last edited by wiseboy on 2018-3-25 08:18. If the heat transfer coefficient is not taken into account and instead a value of 20 is used for the heat transfer coefficient, then the original poster wouldn’t have asked the question. The core of heat exchanger calculations is to compute the heat transfer coefficient rather than simply using it. In fact, it can be calculated using specialized software such as Dr. Coil Heat Exchange.
It’s indeed not clear; it seems the calculation steps are more or less like this, provided for reference.