II. Flow parameters:

**5. Future research directions**

*Advances in Microfluidics and Nanofluids*

can be an exciting field

microchannels

parameters and Flow parameters.

inlet/outlet.

**170**

I. Flow parameters:

**6. Conclusion**

Finally, according to the reviewed papers and commercialized devices, some

I. Combination of micro pin-fin and oblique patterns to obtain novel patterns

II. Investigation of hybrid nanofluids and PCMs in commercialized heat sinks

III. Study of flow containing phase change particles and hybrid nanofluid within

IV. Using the hybrid pattern (micro pin-fin + microchannel) in commercialized

VI. Using liquid cooling in small digital devices such as tablets and cellphones

Liquid cooling techniques in heat sinks have been using to increase the heat transfer rate in electronic devices. The performance of the heat sink is affected by some parameters. Geometry parameters (shape of the cross-section, pattern, manifolds) and flow parameters (working fluids and boiling) are the most common methods for enhancing the thermal–hydraulic performance of micro pin-fin/ microchannel heat sink. Effective parameters are divided into two parts Geometry

> a. pattern: It was found that changing the channel flow path leads to generating the phenomena such as secondary flows in the channel cross-section that result in improving thermal performance. The previous data demonstrated, the geometric parameters play a

performance compared to other microchannels heat sinks. While in micro pin-fins, it is impossible to conclude precisely the best cross-

c. Manifold: it concludes that flow and temperature maldistribution should be reduced along the microchannel to reach the ideal flow distribution for obtaining optimal performance. Also, other parameters are crucial as well, such as header shape, inlet configurations (vertical and horizontal flow inlet/outlet),

inlet/outlet arrangements (I, Z, C, S, V, and U-types), location of

b. Cross-section: rectangular cross-section presents maximum

section due to the different operating conditions.

significant role in heat sinks' performance

V. Using jet impingement heat sink that can remove high heat fluxes

research gaps recognized and the following directions are suggested:

that may increase thermo-hydraulic performances

heat sinks for increased thermal performance.

