Effect of nozzle geometry on heat transfer characteristics from a single circular air jet

The paper reports results on the effects of nozzle geometry on local and average heat transfer distribution in unconfined air jet impingement on a flat plate. An infrared thermography camera is used to record the temperature distribution from isotherms on a uniformly heated impingement surface. Experiments have been conducted with variation of exit Reynolds number, Re, in the range of 6000 ≤ Re ≤ 40,000 and plate surface spacing to nozzle diameter, H/d, in the range of 1 ≤ H/d ≤ 6 for single nozzle with square edge (non-chamfered) and chamfered nozzles of the same diameter, 5 mm. The chamfered length, Lc is varied from 1 mm to 3.65 mm with constant chamfered angle, θ = 60 and length to diameter ratio of 50 is chosen for each nozzle configuration. It is observed that the local and average Nusselt numbers have the highest value for square edge inlet nozzle when compared with other nozzle configurations. The average Nusselt number was correlated for the nozzle Reynolds number as Nu ¯ ∝ R e 0.75 ( H / d ) − 0.016 for square edge. For chamfered edge nozzles, the value of average Nusselt number is depend on jet Reynolds number, separation distance and chamfered length, Lc, Nu ¯ ∝ R e 0.76 ( H / d ) − 0.015 ( L c / d ) − 0.01 .