Turbulence promoters have been widely applied to enhance heat transfer in internal flow channels, although they cause pressure loss. This study employed the transient liquid-crystal technique to measure the heat transfer distribution in a square channel with compound turbulence promoters with orthogonal (90 deg), continuous angled (45 deg), discrete angled (45 deg), V-shaped, and inverted-V-shaped rib configurations. The rib height-to-hydraulic diameter ratio (e∕D h ) and the rib pitch-to-height ratio (P∕e) were 0.1 and 8, respectively. Variations in the Nusselt number were observed after adding grooves between the ribs. The Reynolds number tested in this study ranged from 15,000 to 35,000. Adding grooves between the ribs enhanced the heat transfer. The convective heat transfer coefficient increased by up to 40%, whereas the friction factor ratio increased by less than 30%. The discrete angled configuration of grooved ribs exhibited the maximal heat transfer enhancement and thermal performance, whereas the orthogonal configuration attained the minimal heat transfer enhancement and thermal performance. The frictional loss of the V-shaped and inverted-V-shaped configurations was higher than that of the continuous or discrete arrangements for both ribs-only and ribbed-grooved configurations.

Reducing the electricity consumption from the cooling systems in a data center can cut the energy cost. The development of the high efficiency cooling schemes can effectively save more energy from the computer room air conditioning (CRAC) system. Impingement cooling with air jets can achieve high heat transfer rates and could be used to cool local hot spots in the cabinets. A 5 × 5 jet array was designed utilizing circular and elliptic holes. The cross sectional area of the test region was 250 mm × 25 mm. The jet Reynolds numbers is 3300. Heat transfer coefficients on the target surface were investigated. Results indicated that the impingement cooling provided lower surface temperature than the traditional fan cooling.