Experimental investigation of heat transfer from an array of air jets impinging normally on a flat plate

Author

• Deniz Metin Kaya, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

5-31-1985

Degree Name

Master of Science in Mechanical Engineering - (M.S.)

Department

Mechanical Engineering

First Advisor

P. Hrycak

Second Advisor

Gerald Jaffe

Third Advisor

E. S. Geskin

Abstract

Heat transfer from submerged, turbulent, circular and axisymmetric array of air jets impinging normally on a hot flat plate has been studied experimentally. Jets issued from an array of five nozzles 6.35 mm (0.25 in.) in diameter. The ratio of nozzle center-to-center distance to the nozzle diameter, given by C_n/D, of 2, 3 and 4 were considered. Nozzle exit Reynolds Numbers 14000, 26000 and 54000 were employed. The ratio of distance between the test plate and nozzle diameter (Z_n/D) varied from 5 to 15.

Two experimental arrangements, one with a segmented brass plate heated by a guarded heater and other with a steam-heated stainless steel plate with heat-flux measuring calorimeters were used during the investigation.

Stagnation point heat transfer intensities were found slightly different from those corresponding to a single jet. Increasing mass flow rate and the turbulance generated by the interaction of flow of jets improved the average heat transfer rates. An examination of results revealed a weak dependence of average Nusselt numbers on nozzle-to-plate spacing. It was observed that the heat transfer intensity has a tendency to peak out at the impingement points of the surrounding jets. The individual cooling effect of neighbouring jets became more pronounced with increasing nozzle-to-plate spacing. Increasing Z_n/D helped to spread out the local heat transfer toward the edge of the test plate for all the orifice plates used. A more uniform heat transfer in the area close to the stagnation points of the jets used was achieved by using orifice plates with relatively small nozzle-to-nozzle spacings.

Recommended Citation

Kaya, Deniz Metin, "Experimental investigation of heat transfer from an array of air jets impinging normally on a flat plate" (1985). Theses. 3443.
https://digitalcommons.njit.edu/theses/3443