Microchannels heat sinks are employed in many industrial applications, among which the cooling of small electronic components, thanks to their small dimensions and high area-to-volume ratio. The main drawback of such devices is the adverse effect of viscous heating, which also implies high friction losses, especially for liquid flows. If the channel is of sufficient length, the fluid temperature will eventually exceed that of the walls, making cooling impossible. In this work the critical channel length, above which the wall is heated by the fluid due to viscous effects, is derived from the energy balance as a function of the Peclet and Brinkman numbers. Then, Performance Evaluation Criteria (PEC) are applied for the optimization of the channel geometry for a fixed size of the micro-heat sink. Since the channel length may be comparable to that of the thermal entry region, the average Nusselt number, required to apply PECs, is evaluated from the numerical solution of the Graetz-Brinkman problem. Results show that, depending on the applied restrictions, the heat transfer performances of the microchannel heat sink can be improved, compared to the reference square geometry, by a suitable choice of the aspect ratio.
Microchannel Heat Sink Optimization Considering Viscous Heating
Suzzi N.;
2026-01-01
Abstract
Microchannels heat sinks are employed in many industrial applications, among which the cooling of small electronic components, thanks to their small dimensions and high area-to-volume ratio. The main drawback of such devices is the adverse effect of viscous heating, which also implies high friction losses, especially for liquid flows. If the channel is of sufficient length, the fluid temperature will eventually exceed that of the walls, making cooling impossible. In this work the critical channel length, above which the wall is heated by the fluid due to viscous effects, is derived from the energy balance as a function of the Peclet and Brinkman numbers. Then, Performance Evaluation Criteria (PEC) are applied for the optimization of the channel geometry for a fixed size of the micro-heat sink. Since the channel length may be comparable to that of the thermal entry region, the average Nusselt number, required to apply PECs, is evaluated from the numerical solution of the Graetz-Brinkman problem. Results show that, depending on the applied restrictions, the heat transfer performances of the microchannel heat sink can be improved, compared to the reference square geometry, by a suitable choice of the aspect ratio.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
