A Feasibility Study of Supersonic Air Flow for Cooling Application

The theoretical study of steady, one-dimensional, isentropic, compressible fluid flow suggests that a convergent-divergent passage is required for accelerating a compressible fluid to supersonic velocities. It also reveals that along with pressure, temperature of the compressible fluid continuously decreases along the flow passage. Air is also a compressible fluid which is freely and abundantly available. Keeping these facts in mind the possibility of obtaining supersonic flow with the help of compressed air is first studied theoretically. A convergent divergent nozzle is designed and developed for obtaining supersonic flow of air. An experiment is carried out for various back pressures for verifying supersonic flow and measuring the exit temperature of air. It is observed that supersonic flow can be obtained with minimum back pressure of 1 bar. Exit temperature of air can be varied by changing the back pressure of the nozzle. Temperature drop of air as high as 18.23 0C could be obtained. These factors prove the potential of supersonic air jet as a good and environmentally friendly cooling medium especially for localized cooling applications.