Thermal performance measurement for confined heat sinks

The convective heat transfer characteristics for confined heat sinks by using two experimental methods such as the improved transient liquid crystal method and thermal testing method have been systematically investigated. The trends of average effective heat transfer coefficients measured by using transient liquid crystal method are consistent with that by using thermal testing method. The deviation of the results evaluated by transient liquid crystal method from the data measured by thermal testing method will become more significant when the air flow velocity increases. For exploring the parameters influencing the thermal and fluid friction performances, the average effective heat transfer coefficient increases with increasing flow velocity or decreasing channel porosity; the highest and lowest effective heat transfer coefficients can be found for the cases close to fully-confined and unconfined heat sinks at a specific channel inlet velocity, respectively. The overall channel pressure drop increases with increasing flow velocity. The highest and lowest pressure drops can be found for the cases close to fully-confined and unconfined heat sinks at a specified air flow velocity, respectively. Furthermore, two new correlations of average effective heat transfer coefficient in terms of flow velocity and channel porosity for confined heat sinks are proposed for transient liquid crystal method and thermal testing method, respectively. Finally, a concept of the amount of enhanced heat transfer (AEHT) defined as the ratio of j/f for heat sink analysis is introduced. The j/f ratio is almost independent of Reynolds number for a specific confined heat sink; and it increases with decreasing channel porosity. All the present experimental data for partially confined heat sinks are reasonably bounded between 0.0124 for unconfined heat sinks and 0.0603 for fully-confined heat sinks.