Experimental investigation of the effect of compound protrusion-pin array on heat transfer in an internal rotating cooling channel

An experimental investigation was conducted to study the effect of protrusions and their combination with pins on heat transfer enhancement in a rotating internal passage with an orientation angle of 90 degrees for Reynolds numbers (Re) of 10,000 and 20,000. The trailing surface showed the highest Nusselt number (Nu). The highest and lowest local Nusselt number was at the front and back of the protrusion respectively. A short disturbed wake region was observed behind the protrusion as a result of complex three dimensional flow. Addition of pins in the configuration resulted in an increase of the average Nusselt number, specifically a 35%, 50% and 142% for trailing, static and leading surfaces respectively, compared to protrusions only case for Re of 10,000. On removal of the third column of protrusions, average Nusselt number showed a decrease of 8.25%, 3.1% and 2.3% for trailing, static and leading cases respectively, compared to the protrusion-pin case for Re of 10,000. It also caused elongation of the stagnation and wake flow fields around the fourth column comprising of pins. Pressure drop results indicated that the protrusion only case was the lowest compared to protrusion-pin.