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# An air heater consists of a steel tube with inner and outer radii ofr112 mmandr2 15 mm, respectively length of tube L= 2 m and eight integrally machined

An air heater consists of a steel tube, with inner and outer radii ofr1= 12 mmandr2= 15 mm, respectively, length of tube L= 2 m, and eight integrally machined longitudinal fins, each of thicknesst= 2 mm. The fins extend to a concentric tube, which is of radiusr3= 50 mmand insulated on its outer surface. Water at a temperatureT8,i= 95°Cflows through the inner tube with inner heat transfer coefficient hi = 10 W/m2·K, while air atT8,o= 25°Cflows through the annular region formed by the larger concentric tube at the speed of 10 m/s in the axial direction. Assume the 8 fins are the rectangular straight fins; and the air flow is a parallel flow over the 8 plates. What is the total heat transfer rate from water to air? Hints:

1. Drawing diagrams of thermal circuit, heat transfer rates or heat fluxes, temperatures, etc.
2. Stating that which equations, figures and tables you are using at each step.
3. Compute the flow over a plate problem.
4. Is it Laminar or turbulent flow?
5. Solve the total heat transfer rate for the entire structure.
6. Will the two sides of every fin be considered?

Apr 26 2020 View more View Less Subscribe To Get Solution