Investigation on Flow Maldistribution in Parallel Microchannel Systems for Integrated Microelectronic Device Cooling

This paper brings out the phenomenon of flow maldistribution in parallel microchannel systems, which is supposed to have an adverse effect on hot spot formation and temperature distribution in microelectronic devices. An extensive experimental study is carried out where in the parameters affecting the flow maldistribution such as number of channel, area of cross section of the manifold, channel hydraulic diameter, and Reynolds number are varied to study their effect on the pressure drop across the parallel channels designed for liquid cooling of a CPU. It is observed that the flow distribution among the channels improves significantly with a decrease in the channel hydraulic diameter due to higher pressure drop offered by each individual channels simultaneously. This results in a considerable reduction in both the peak temperature and the average temperature of the device with decreasing channel diameters. It is also inferred that the flow maldistribution is relatively invariant with Reynolds number for the microchannel system, which is not the case for the macrochannels. Flow maldistribution is found to increase with increase in number of channels and with a decrease in the manifold area relative to the channel area. The “I” type flow configuration is found to have the least maldistribution while the “U” type shows the maximum and Z type falls in between. A simple force analysis of the governing equation in the manifold of the parallel microchannel system reveals a strong dominance of the frictional force over the inertial force and both the forces contribute to the uniform flow distribution at smaller hydraulic diameters, where the 1-D theoretical models failed to achieve a concurrence with the present experimental results. Also the present 3-D numerical simulations give a satisfactory agreement with the experimental results projecting it as an effective tool in the design and analysis of microchannel cooling system. The potential zones of hot spots are identified as low fluid velocity zones or low pressure drop zones among the channels resulting from flow maldistribution.