Experimental study on heat transfer from rectangular fins in combined convection

Combined natural and forced convective heat transfer arise in many transport processes in engineering devices and in nature, which is frequently encountered in industrial and technical processes, including electronic devices cooled by fans, heat exchangers placed in a low-velocity environment, and solar receivers exposed to winds. In this study, the effects of design parameters have been experimentally investigated for the air-side thermal performance under combined (natural and forced)convection of the rectangular plate heat sinks, and the values of optimum design parameters were sought. Many ideas for improving cooling methods have been proposed, one of which is the heat sink. In this work, the average Nusselt number (Nu) and thermal resistance of a simple base rectangular plate and five vertical rectangular plate heat sinks with different numbers of fins under natural and combined convection were experimentally investigated to obtain the maximum average Nu and minimum thermal resistance for various Reynolds numbers (Re) from 2300 to 40000, Rayleigh numbers (Ra) from 1300000 to 13000000, and Richardson numbers (Ri) from 0.4 to 3. Also, in this experiment, fin spacing (P) was varied from 2.8 mm to 14.6 mm and the dimensionless P/H ratio was varied from 0.1 to 0.49. The flow velocity varied in the range of 2 to 8 m/s under combined convection. Based on the effects of Ri and Re, two empirical equations for natural and also for combined convection heat transfer were derived to calculate the average Nu. The average deviation for these two equations is about 7%.The outcomes of this research can be beneficial for engineers who work on electronics cooling systems

An extensive review of the most recent advancements in the use of oscillating heat pipes for cooling photovoltaic thermal systems

Photovoltaic-thermal (PV-T) panels are one of the major solar energy sources used to convert solar radiation into electrical power directly. This type of panel is considered a viable solution to guarantee energy security and reduce greenhouse gases. On the other hand, the efficiency of PV-T modules diminishes when the temperature of the nodule rises, leading to a degradation in the conversion efficiency along with the life span of a photovoltaic cell. Applying cooling techniques will lead to the decrease of the excess heat that is generated and will make the life span longer simultaneously. Higher efficiency can be achieved by incorporating oscillating heat pipe (OHP) into energy systems. PV-T module thermal and electrical efficiency can be improved by using an oscillating heat pipe. This review encourages the selection of an oscillating heat pipe and the heat transfer enhancement approach to increase energy conversion rate and the productivity corresponding to the PV-T system, as well as identifies the research gaps, future vision, and development that can be done. Firstly, the OHP-PV-T system and its performance in detail are illustrated. Then, the structure and working principles of the system are discussed, followed by a review of the work conducted in this case. The advantages of using an oscillating heat pipe as a solar panel cooling approach are then highlighted. Understanding the advanced cooling technologies mentioned above is vital for further modifications of current PV-T panels. Moreover, using nanofluid as coolant can make a significant contribution to enhancing the total system efficiency

Journal of a missionary voyage to New Guinea / by A.W. Murray and S. Macfarlane.

Electronic reproduction. Canberra, A.C.T. : National Library of Australia, 2011