Heat trransfer to a plane free oil jet impinging at an angle on a flat surface

摘要

The heat transfer rate from a heated flat horizontal heated surface to an impinging free oil jet that originates from a wide rectangular (lane) nozzle has been numerically and experimentally studied. The oil jet, in general, impinges on the surface at an angle i.e. the intial jet flow is not normal to the surface. In the expeirmental study, the oil jet was discharged from a 5mm wide slot nozzle that had an aspect ratio of 20 at velocities of between 0.1 and 0.4m/s. For the type of oil used in the study, this gave jet Reynolds numbers based on the nozzle width, i.e. 5mm, approximately between 50 and 150. The horizontal heated surface was made from a thin stainless steel sheet bonded to a plexigles backing. The surface was heated by passing an electrical current through the stainless steel and the surface temperature was measured using thermocouples bonded to the back of this sheet. Tests were undertaken with the discharge nozzle set at distances of between 2 and 10 nozzle width from the surface at nozzle discharge angles of between 0 deg (vertical, i. e. normal to surface) and 20. In addition to the heat transfer measurements, the thickness of the oil layer on the surface was measured. In the numerical study, the heat transfer rate variation in the impingement point region was c alculated using a finite element solver. Numerical solutions were obtained for Reynolds numbers up to 500 for Prandtl numbers between 10 and 180, for jet impingement angles of between 0 and 30 deg for nozzle heights above the surface of between 2 and 6 nozzle heights above the surface of between 2 and 6 nozzle widths. A separate numerical study of the heat transfer rate far from the impingement point has also been undertaken.