Turbulent Heat Transfer and Friction in Pin Fin Channels With Lateral Flow Ejection

Abstract

Experiments were conducted to study the effects of lateral flow ejection on the overall heat transfer and pressure drops for turbulent flow through pin fin channels. The two test sections of the investigation were rectangular channels with staggered arrays of six and eight streamwise rows of pins, respectively. The pin length-to-diameter ratio was one and both the streamwise and spanwise pin spacings were 2.5 times the pin diameter. Heat transfer and friction data were obtained for various ejection exit geometries, for ejection ratios between 0 and 1, and for Reynolds numbers between 6000 and 60,000. The results of the study show that, for any given ejection ratio, the overall Nusselt number increases with increasing Reynolds number. However, the overall Nusselt number is reduced by as much as 25 percent as the ejection ratio is increased from 0 to 1 over the range of Reynolds number studied. The Nu–Re–ε relationship, which is insensitive to varying the ejection exit geometry, can be correlated by the equation (Nu/Nu0) = (Nu1/Nu0)ε, where Nu0 = c0Rem and Nu1 = c1Ren are the overall Nusselt numbers in the 0 and 100 percent lateral flow ejection cases, respectively. The results also show that the overall friction factor is independent of the flow Reynolds number over the range of Reynolds number studied. However, the friction factor is strongly dependent on the ejection ratio as well as the geometries of the straight flow exit and lateral ejection flow exit.