Heat transfer distribution and shadowgraph study for impinging underexpanded jets

• Published in: Applied thermal engineering 2017-03, Vol.115, p.41-52
• Main Authors: Vinze, Ravish, Chandel, S., Limaye, M.D., Prabhu, S.V.
• Format: Article
• Language: English
• Subjects: Adiabatic flow; Contoured nozzle; Correlation analysis; Fluid dynamics; Fluid flow; Foils; Heat transfer; Infrared cameras; Jets; Nozzles; NPR; Nusselt number; Plates (structural members); Pressure ratio; Recovery; Recovery factor; Shadowgraph photography; Studies; Temperature distribution; Under-expanded jets; Wall temperature
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2016.12.046

In the present study, the influence of impinging underexpanded jets on local heat transfer is studied for nozzle pressure ratio (NPR) ranging from 2.4 to 5.1. To measure the local temperature distribution, a thin metal foil technique with Infrared camera is used. The adiabatic wall temperature is taken as the reference temperature for calculating local Nusselt number and recovery factor. The flow structure distributions captured with the shadowgraph technique are compared with the local Nusselt number and recovery factor distributions. Shadowgraph images show that the shock structure in the flow region plays an important role in governing the local heat transfer distribution over the plate. To propose a generalized correlation for local heat transfer for underexpanded jets, three contoured nozzles of exit diameter of 3.6mm, 5.67mm and 8.37mm are studied. Proposed correlations for the local heat transfer show good agreement with the experimental results for larger nozzle to plate distances.