Transient heat transfer characteristics of segmented finned microchannels

• Performance analysis of microchannel heat sinks during transient operating conditions.
• Estimation of response time for various operating conditions.
• Calculation of transient and steady state heat transfer coefficient.
• Performance comparison of segmented finned with uniform cross-section microchannels.

An experimental investigation has been carried out to study transient heat transfer characteristics of segmented finned microchannels during single-phase flow and flow boiling of coolant. Further heat transfer characteristics of segmented finned channels have been compared with those of uniform cross-section microchannels. Deionized water has been used as coolant. An array of microchannels consisting of 12 numbers of channels has been fabricated in each type of channel configuration. In each configuration, copper blocks of size 25.7 × 12.02 × 10 mm3 have been used to fabricate microchannels of width 400 μm and depth of 750 μm with hydraulic diameter of 522 μm. Experiments have been performed for single-phase flow and flow boiling regimes with coolant mass flux (G) range of 100–350 kg/m2 s and applied heat flux (qeff″) range of 20–300 kW/m2. Based on time required to reach steady state temperature, response time of each microchannel configuration has been estimated for different values of coolant mass flux and heat flux. A comparison of bubble growth behaviour in both types of channels has been presented. Coolant mass flux significantly affects the response time. During single-phase flow of coolant, response time decreases with increase in coolant mass flux, whereas response time increases with increase in coolant mass flux in flow boiling of coolant. Response time is less in flow boiling condition compared to single-phase flow of coolant. Segmented channels show less response time and enhanced heat transfer compared to uniform channels. Unhindered bubble growth phenomenon helps in reduction of response time in segmented channels.