Master of Science in Mechanical Engineering (MSME)
Metal-based MHEs are of current interest due to the combination of high heat transfer performance and improved mechanical integrity. Efficient methods for fabrication and assembly of functional metal-based MHEs are essential to ensure the economic viability of such devices. The present study focuses on the results of heat transfer testing of assembled Cu- and Al- based microchannel heat exchanger (MHE) prototypes. Efficient fabrication of Cu- and Al- based high-aspect-ratio microscale structures (HARMS) have been achieved through molding replication using surface engineered, metallic mold inserts. Replicated metallic HARMS were assembled through eutectic bonding to form entirely Cu- and Al- based MHE prototypes, on which heat transfer tests were conducted to determine the average rate of heat transfer from electrically heated Cu blocks placed outside the MHEs to water flowing within the molding replicated microchannel arrays. Experimentally observed heat transfer rates are higher as compared to those from previous studies on microchannel devices with similar geometries. Further, infrared thermography was conducted to determine the overall cooling rate and time constants. The time constant for the MHE device was found out to be lower for Cu channels with response times around 1-2 seconds. Al MHE device response time was only slightly lower due to the lower thermal conductivity. Experimental results show a great influence of the type of metal, flow rate and the surrounding conditions on the overall cooling performance of the MHEs. The potential influence of microchannel surface profile on heat transfer rates is discussed. The present results illustrate the potential of metal-based MHEs in wide ranging applications. A two-dimensional thermal lattice Boltzmann model was developed to simulate the heat transfer phenomenon in Cu- and Al- based microchannels. The LBM results were compared with 3D and 2D fluent models. Additionally, attempts were made to visualize the flow field inside an assembled Cu micro-channel at very low flow rates using oil-in-water solution.
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Parida, Pritish Ranjan, "Experimental investigation of heat transfer rate in micro-channels" (2007). LSU Master's Theses. 849.