Design optimisation and analysis of heat sinks for electronic cooling

Since industrial devices create power dissipation in the form of heat created as a by-product, which can have a negative effect on their performance, certain temperature limit constraints are required for almost all these applications to work within suitable conditions. That is, these engineering devices might fail in some way if these limitations are surpassed by overheating. In all the related industries, inexorable increases in power densities are driving innovation in heat exchange techniques. Furthermore, electronic devices are becoming smaller at the same time as their thermal power generation increases. Thus, heat sinks can be applied for cooling critical components in many important applications ranging from aero-engines and nuclear reactors to computers, data centre server racks and other microelectronic devices. \nThe most common cooling technique for heat dissipation for thermal control of electronics is air cooling. Reduced cost, simplicity of design, the easy availability of air, and increased reliability are the main benefits of this cooling method. Heat sinks with a fan/blower are commonly used for air-cooled devices as a forced convection heat transfer. An amount of heat is dissipated from the heat source to environmental air utilising a heat sink as a heat exchanger, which is a vital practice employed in air-cooling systems. This transfer mechanism is easy, simple and leads to reduced cost and increased reliability, and pinned heat sinks are more beneficial than plate fin heat sinks. \nThe main interest of this study is to investigate the benefits of using perforated, slotted, and notched pinned heat sinks with different configurations to reduce CPU temperature and fan power consumption to overcome the pressure drop and maximise a heat transfer rate through the heat sink. An experimental heat sink with multiple perforations is designed and fabricated, and parameter studies of the effect of this perforated pin fin design on heat transfer and pressure drops across the heat sinks are undertaken, to compare it to solid pinned heat sinks without perforations. Experimental data is found to agree well with predictions from a CFD model for the conjugate heat transfer and turbulent airflow model into the cooling air stream. The validated CFD model is used to carry out a parametric study of the influence of the number and positioning of circular perforations, and slotted/notched pinned heat sinks. Then, the multi-objective optimum pinned heat sink designs are tested to obtain CPU temperature and fan power consumption as lowest as possible through the heat sink. In addition, the limitations in application of pinned heat sinks based on the pin density and applied heat flux are reported for active air-cooling electronic systems. \nAn overview of the findings indicates that the CPU temperature, the fan power consumption, and the heat transfer rate in terms of Nusselt number are enhanced with the number of pin perforations and slotted/notched pinned heat sinks, while the locations of the pin perforations are much less influential. These benefits arise due to not only the increased surface area but also to the heat transfer enhancement near the perforations through the formation of localised air jets. Finally, the perforated heat sinks will be lighter in weight compared with solid pinned heat sinks.