Numerical Investigation on Slot air Jet impingement Heat Transfer between Horizontal Concentric Circular Cylinders

Document Type: Research Paper

Authors

1 Department of Mechanical and Aerospace Engineering, Science and Research Branch, Islamic Azad University, Tehran

2 Department of Mechanical Engineering, University of Tehran

Abstract

A numerical study has been carried out for slot air jet impingement cooling of horizontal concentric circular cylinders. The slot air jet is situated at the symmetry line of a horizontal cylinder along the gravity vector and impinges on the bottom of the outer cylinder which is designated as θ=0°. The outer cylinder is partially opened at the top with a width of W=30mm and is kept at constant temperature T= 62°C. The inner cylinder which is a part of the slot jet structure is chosen to be insulated. The effects of jet Reynolds number in the range of 100≤ Rej ≤1000 and the ratio of spacing between nozzle and outer cylinder surface to the jet width for H=4.2 and H=12.5 on the local and average Nusselt numbers are examined. In the numerical study, FLUENT CFD package is used and validated by comparing the results with the experimental data at the same Reynolds number. It is observed that the maximum Nusselt number occurs at the stagnation point at (θ=0°) and the local heat transfer coefficient decreases on the circumference of the cylinder with increase of θ as a result of thermal boundary layer thickness growth. Also, results show that the local and average heat transfer coefficients are raised by increasing the jet Reynolds number and by decreasing the nozzle-to-surface spacing.

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