Engineering HDR Seminar Series 8, 2013: Thermal Performance of Micro Heat Pipes

Mr Chang Fun Liang, postgraduate (Mechanical Engineering)

Date: 2013-02-27
Time: 11:00 to 12:00
Venue: Engineering Meeting Room 1, 5-4-22


Due to the rapid advances in miniaturization of electronic components, micro heat pipe stands out to be one of the effective high-heat-flux removal devices. Benefiting from the phase-change heat transfer of its working fluid, micro heat pipe, which is a micro-scale cooling device with a hydraulic diameter on the order of , manifests itself with extremely high thermal conductance, and its effective thermal conductivity is typically multiple times that of the solid wall material. Due to the difficulties associated with experimentation in a sealed micro-scale device like micro heat pipe, analytical investigations of the transport processes such as the fluid mechanics and heat transfer characteristics associated with the thermal performance of the device are of paramount importance. The investigation of the transport phenomena in micro heat pipes is considerably complicated, encompassing the fields of heat transfer, fluid mechanics, thermodynamics, as well as thin film evaporation and condensation characteristics. In this research project, a detailed steady-state one-dimensional mathematical model based on the physical phenomena of micro heat pipe is developed, particularly to investigate the roles of the working fluids and solid wall relating to the thermal performance of micro heat pipe, entailing a number of problems demanding better insights to be addressed. To this end, a series of investigations encompassing four fundamental objectives will be implemented. Firstly, the model is established to examine the interrelationship of the thermo-physical properties of the working fluid with the effect of the axial conduction in the solid wall on the thermal performance of a horizontally oriented micro heat pipe which is optimally charged with working fluid at its designated operating temperature. The theoretical model has been checked and verified using the experimental data of previous investigations. Secondly, further study will be conducted by extending the model to facilitate investigation on electrohydrodnamic (EHD) pumping assisted micro heat pipes which are very efficient when space constraint is an issue. Effective heat transfer enhancement can be attained by applying EHD operating at high voltage. Thirdly, the Marangoni effect due to surface tension gradient of the working fluid inside a micro heat pipe will be investigated. The Marangoni effect which is dependent on the temperature gradient is postulated to be significant when the micro heat pipe is overloaded where dryout takes place at the evaporator end, inducing a high temperature gradient at the solid wall. Fourthly, the present mathematical model will be modified to relate the operating temperature of the micro heat pipe with the ambient temperature, by considering convective boundary conditions at the condenser section of the micro heat pipe, which is of considerable practical significance by providing a firm theoretical basis for the experimental determination of the operating temperature of a micro heat pipe. Lastly, arrays of micro heat pipes will be fabricated and experimentation will be performed for the validation of the theoretical model.

About the Speaker

Chang Fun Liang graduated from Monash University Sunway Campus with Bachelor of Enginering (with first class honors) in the field of Mechanical Engineering in year 2011. He joined Monash University for postgraduate studies in year 2012 under the supervision of Dr. Hung Yew Mun and A/Prof. Ong Kok Seng. His current research focuses on the various factors affecting the thermal performance of micro heat pipes.