Prof. Ahmed Attia Abd El_Latief Attia :: Publications:

The present study is carried on a channels array filled partially with a working fluid representing micro heat pipe. The effect of varying the configuration, hydraulic diameter and characteristic of working fluid on the thermal characteristic and performance are investigated. Ten chips of the same dimensions are fabricated and tested. Five of them have rectangular channels array with different hydraulic diameters. The remaining five have triangular channel array (V- shape) with the same hydraulic diameters. Deionized water, methanol and solution of de-ionized water and ethylene glycol with concentration varied from 10% to 60% with step 10% are tested as micro heat pipe working fluids. Varying the various inter-related parameters such as the evaporator input power and the coolant flow rate from which the results are obtained. It indicated that the rectangular grooved chip of 900µm hydraulic diameter, using methanol as the working fluid introduced the lowest evaporator section temperature. The same results are gained when testing rectangular grooved chip of 700µm using de-ionized water as working fluid. In addition, the rectangular grooved chips of 800µm and 900µm hydraulic diameters as well as, the triangular grooved chip of 500µm hydraulic diameter with de-ionized water as working fluid are the pioneers in introducing the highest conductance. Moreover, the rectangular grooved chip of 800µm hydraulic diameter with 50% ethylene glycol brine introduced the desired performance. This desired performance means lowest evaporator section temperature, highest conductance and lowest chip characteristic parameter (Te-Tc)/mw.Cpw . A detailed analysis of the experimental data ensures that the performance of the micro heat pipe array (of specific configuration and working fluid) can be well described by introducing a modified thermal resistance analogy that is applicable to this type of heat pipes. Provided that the chip Nusselt number is correlated with the product (Re.Pr) for specific micro heat pipe configuration and working fluid. The later result represents a helpful tool for predicting the chip heat transfer coefficient of micro heat pipe array and working fluid combination.