Constructal design of single microchannel heat sink with varying axial length and temperature-dependent fluid properties

The objective of this numerical study is to investigate the best geometric configuration that maximises heat transfer from the heated base by allowing both the length of the solid substrate and the microchannel heat sink freedom to morph. The thermal performance of the microchannel is based on the minimised peak temperature on the heated surface which gives a global minimised thermal resistance. The optimisation of the geometric parameters of the heat sink and solid substrate is carried out using a computational fluid dynamics code with a goal-driven optimisation algorithm. Results of the effect of Bejan number on the minimised peak temperature and minimised thermal resistance for solid substrate with varying axial lengths of 1 to 10 mm but fixed volume of 0.9 mm3 is presented. Results of optimal channel aspect ratio, solid volume fraction and channel hydraulic diameter of the microchannel were also presented.NRF, TESP, University of Stellenbosch/ University of Pretoria, SANERI/SANEDI, CSIR, EEDSM Hub and NAC.http://www.iieta.org/Journals/IJHTam2016Mechanical and Aeronautical Engineerin

Constructal design of combined microchannel and micro pin fins for electronic cooling

This paper presents a three-dimensional numerical study of steady, laminar, incompressible flow and forced convection heat transfer through a microchannel heat sink with micro pin fin inserts for both fixed and variable axial lengths. The objective of the study was to optimise the geometric configuration of an integrated microchannel and micro pin fins for different solid volumes so that the peak temperature in the configuration was minimised. The effect of the micro pin fins on the optimised microchannel was also investigated. The geometric optimisation of the integrated microchannel and micro pin fin was carried out using a computational fluid dynamics (CFD) code with a goal-driven optimisation tool subject to global constraints. The optimisation procedure was carried out in two steps. Firstly, the microchannel configuration was optimised without the micro pin fins inserted and the results were compared with similar work found in the open literature. This optimisation was carried out for both fixed and relaxed lengths. Thereafter, the integrated design of the microchannel and micro pin fins was optimised. The effect of the Bejan number on the solid volume fraction, channel aspect ratio and hydraulic diameter, pin fin aspect ratio, minimised peak temperature and maximised thermal conductance were reported. Results showed that as the Bejan number increased, the minimised peak temperature decreased. Also, the maximum thermal conductance increased with the optimised microchannel structure with three to six rows of micro pin fin inserts. Diminishing return set in when the number of rows of micro pin fin inserts was greater than three for the fixed length but for the relaxed length, as the number of rows increased, the results improved but when it exceeded six diminishing returns set in for a fixed solid volume of 0.9 mm3. For each Bejan number used in this study, there was an optimum channel hydraulic diameter and aspect ratio, solid volume fraction and pin fin aspect ratio that satisfied the global objective.NRF, TESP, University of Stellenbosch, University of Pretoria, SANERI/SANEDI, CSIR, EEDSM Hub and NAChttp://www.elsevier.com/locate/ijhmthb2014ai201

Constructal design of single microchannel heat sink with varying axial length and temperature-dependent fluid properties

The objective of this numerical study is to investigate the best geometric configuration that maximises heat transfer from the heated base by allowing both the length of the solid substrate and the microchannel heat sink freedom to morph. The thermal performance of the microchannel is based on the minimised peak temperature on the heated surface which gives a global minimised thermal resistance. The optimisation of the geometric parameters of the heat sink and solid substrate is carried out using a computational fluid dynamics code with a goal-driven optimisation algorithm. Results of the effect of Bejan number on the minimised peak temperature and minimised thermal resistance for solid substrate with varying axial lengths of 1 to 10 mm but fixed volume of 0.9 mm3 is presented. Results of optimal channel aspect ratio, solid volume fraction and channel hydraulic diameter of the microchannel were also presented.NRF, TESP, University of Stellenbosch/ University of Pretoria, SANERI/SANEDI, CSIR, EEDSM Hub and NAC.http://www.iieta.org/Journals/IJHTam2016Mechanical and Aeronautical Engineerin

Temperature variation on the heated base of a solid substrate cooled with different types of heat sink

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Three-dimensional numerical studies were carried out to investigate forced convection heat transfer and fluid flow in a solid substrate cooled using different types of micro heat sinks. The objective of this study is to investigate which heat sink type gives the lowest temperature variation on the heated base of the solid substrate which is being cooled. A low temperature variation indicates a low temperature gradient which, in practical application, improves the reliability of the electronic device. The different heat sinks considered are single microchannels, two-layer microchannels with parallel and counter-flow of fluid, single microchannels inserted with circularshaped micro pin fins and two-layer microchannels inserted with circular-shaped pin fins. All the heat sinks are geometrically optimised using a computational fluid dynamics code with a goaldriven optimisation algorithm subject to global constraints. The thermal performance of the heat sinks considered in this study is based on two objectives namely, the minimisation of the peak temperature which results in maximisation of the thermal conductance and the lowest temperature variation on the heated base. The heat sink with the largest value of thermal conductance and lowest temperature variation on the heated base for the range of pressure drop considered is chosen as the best heat sink design. Numerical results of thermal performance for fixed axial length of the solid showed that cooling the solid substrate with the two-layer microchannel with counter-flow of fluid gave the lowest temperature difference at base of the solid substrate and also performed best in maximising thermal conductance at pressure drops of 20 and 30kPa.dc201