Detailed heat transfer investigation of an impingement jet array with large jet-to-jet distance

Abstract

The heat transfer performance of a large jet-to-jet distance impingement configuration with a jet-to-jet spacing X/D = Y/D = 10 was experimentally studied for turbomachinery applications. Narrowband thermochromic liquid crystals (TLCs) were used to record the target wall temperature. Pressure taps were set along the experimental rig to measure the pressure loss. Improved measurement methods with multiple TLCs and a ramp heater were studied. The work was done for different Reynolds numbers (Re = 15,000–35,000), different jet to target plate distances (H/D = 3–5) and different cross-flow schemes. The results from the improved methods show good agreement with the basic measurement method. It confirms that the single TLC, step heater method is sufficient for the current experimental study. The improved methods are confirmed to be reliable and are suitable for complex applications with extremely large heat transfer variations over the measured surface, or extremely high local heat transfer coefficients. Experimental results indicate that a smaller jet to target plate distance and a smaller cross-flow scheme can provide a better heat transfer performance in the studied range. When compared to the impingement configuration with X/D = Y/D = 5, the results show that a larger jet-to-jet distance configuration provides a higher overall heat transfer when the mass flow rate is kept constant.