Question

Steam in a heating system flows through tubes whose outer diameter is 5 cm and whose walls maintained at a temperature of 180 degree C. Circular aluminum alkiy 2024-T6 fins (k = 186 W/m . degree C) of outer diameter 6 cm and constant thickness 1 mm are attached to the tube. The space between the fins is 3 mm, and thus there are 250 fins per meter length of the tube. Heat is transferred to the surrounding air at T = 25 degree C. with a heat transfer coefficient of 40 W/m2 . degree C. Determine the increase in heat transfer from the tube per meter of its length as a result of adding fins. Answer 2639 W

Answer 1

The question pertains to calculating the increased heat transfer that results from adding circular aluminum fins to a steam tube in a heating system. The solution involves determining the fin efficiency, the total effective heat transfer area per meter, and using the heat transfer coefficient to quantify the increased heat transfer, which is given as 2639 W per meter.

Step-by-step explanation:

The student inquires about the increase in heat transfer from a steam tube by the addition of aluminum fins in a heating system. To solve this problem, we use principles from the field of thermodynamics, specifically the concept of extending the heat transfer surface area by adding fins, also known as finned heat transfer.

To calculate the effectiveness of fins and the heat transfer, the following procedure is used:

1. Calculate the fin efficiency and multiply by the area of a single fin to determine the effective heat transfer area per fin.
2. Sum the total effective heat transfer area of all fins per meter of tube.
3. Calculate the increase in heat transfer using the extended area, heat transfer coefficient, and temperature difference between the fin surface and the surrounding air.

To apply these steps specifically, one would need to calculate thermal resistance, temperature profiles, and efficiency of the fins, but the final result given by the student is an increase in heat transfer of 2639 W per meter due to the addition of fins.