A Comparative Study on the Effects of Channel Divergence and Convergence on the Performance of Two-Layer Microchannels

This paper compares the hydrothermal performance of two-layer microchannels with the divergent and convergent walls. The heat transfer coefficients, pumping power, and entropy production are investigated via the fluid-solid conjugate hydrothermal simulation. The results showed that in microchannels, the divergent walls reduce both the pumping power and average Nu number, while increase the thermal resistance and the solid base temperature. The convergent walls increase the pumping power and average Nu number and decline the thermal resistance and base temperatures. The microchannels with high TF values (more divergent) are not hydrothermally optimal as compared to those with low TF values (more convergent). For the Re number of 400, with changing TF from l to 0.5, the pumping power and the Nu number increase about 99% and 10%, respectively. However, by changing the TF from l to 2 (or 1/0.5), the pumping power and the Nu number decrease about 101% and 18%, respectively. On the other hand, in the same Re number, by changing the TF from 1 to 0.5, the thermal resistance decreases by 9%. However, by increasing the TF value from 1 to 2, thermal resistance rises by 16%. Finally, it can be found that the negative effect of divergence on thermal resistance is greater than the positive effect of convergence on thermal resistance. In general, the divergent microchannels generate lower frictional entropy and higher thermal entropy. Also, in the divergent microchannels, the production of thermal entropy is higher than the frictional one, while in the convergent microchannels the production of frictional entropy is greater.

Automated summary

This paper compares the hydrothermal performance of divergent and convergent walls in two-layer microchannels. The results show that divergent walls decrease the pumping power and average Nu number, but increase the thermal resistance and base temperatures. Conversely, convergent walls increase the pumping power and average Nu number, while decreasing the thermal resistance and base temperatures. The study also finds that microchannels with low TF values (more convergent) are more hydrothermally optimal compared to those with high TF values (more divergent). Furthermore, divergent microchannels generate lower frictional entropy and higher thermal entropy, while convergent microchannels produce higher frictional entropy.