Characterization of compact heat sink models in natural convection (original) (raw)
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Compact Heat Sink Simulations in both Forced and Natural Convection Flows
8th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2002
In this article, the modeling of heat sinks is carried out using electronic cooling software under both forced and natural convection conditions. Simulations are applied to both detailed and compact heat sink models. The compact models are based on the volume resistance approach also known as the porous block model. These models are devised with the intention of approximating actual heat sink behavior while providing substantial savings in computational effort. In some cases, results obtained from numerical simulations are compared with independent laboratory measurements. This is accomplished with both forced and natural convection flow conditions. In the case of forced convection, the effective thermal conductivity of the compact heat sink is calculated directly from the Nusselt number correlation for flow over a flat plate. When this value is used, the numerically determined thermal resistance of the compact heat sink is found to compare well with the experimental value. In the case of natural convection, the effective thermal conductivity of the compact heat sink is calculated using the corresponding Nusselt number correlation for free convection over a vertical plate. The increased complexity of the correlation for free convection necessitates an iterative solution for the effective thermal conductivity. In this case also, it is shown that results obtained from CFD simulations compare favorably with available laboratory measurements. The case-studies illustrate the manner in which compact heat sinks can be conveniently used to reduce the needed computational cost, time and resources while producing sufficiently reliable results.
2015
Whenever electric current flow through a resistive element say electric chip, heat is generated under natural convection conditions. Electric chips are facing thermal challenges to remove the heat. Effectively that causes rising temperature and failure. For better performance and condition operation additional care must be taken in to account for chip cooling system. One of the effective ways is attaching a heat sink over the chips which removes the heat more effectively and keep the chip at lesser temperature. Heat sink performance will vary with respect to the orientation. Recent study shows that the denser fin arrays or more sensitive to orientations. So in this study similar fin arrays with 0ᵒ,45ᵒ, 90ᵒ, orientation are consider for the numerical simulation under certain condition fins with slots can work better than the plane .different slots shape studied to find the better one of the rectangular fin heat sink.
Natural convection heat transfer from inclined plate-fin heat sinks
International Journal of Heat and Mass Transfer, 2013
The steady-state natural convection from heat sinks with parallel arrangement of rectangular cross section vertical plate fins on a vertical base are numerically investigated in order to obtain a validated model that is used for investigating inclined orientations of a heat sink. Taking a previous experimental study as a basis, aluminum heat sinks with two different practical lengths are modeled. The models and the simulation approach are validated by comparing the flat plate heat sink results with the available correlations, and by comparing the finned heat sink results with the experimental data. Natural convection and radiation heat transfer rates from the fronts of the heat sinks heated from the back with a heater are obtained from finite volume computational fluid dynamics simulations. The sensitivities of the heat transfer rates to the geometric parameters are determined. A set of dimensionless correlations for the convective heat transfer rate is suggested. The validated model is used for several upward and downward inclination angles by varying the direction of gravitational acceleration. At small inclinations, it is observed that convection heat transfer rate stays almost the same, even increases slightly for the downward inclinations. At larger angles, the phenomenon is investigated for the purpose of determining the flow structures forming around the heat sink. For the inclination angles of ±4°, ±10°, ±20°, ±30°, ±45°, ±60°, ±75°, +80°, ±85°, ±90° from the vertical, the extent of validity of the obtained vertical case correlation is investigated by modifying the Grashof number with the cosine of the inclination angle. It is observed that the correlation is valid in a very wide range, from −60° (upward) to +80° (downward). It is also observed that the flow separation inside the fin channels of the heat sink is an important phenomenon and determines the validity range of the modified correlation. It is further shown that the correlations are also applicable to all available inclined case data in the literature, verifying both our results and correlations. Since the investigated ranges of parameters are suitable for electronic device cooling, the suggested correlations have a practical use in electronics cooling applications.
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2018
Downward lighting light-emitting diodes require cooling with cylindrical fin heat sinks to be mounted on top and cooled under natural convection air cooling mode. Performance simulation would involve specification of the heat transfer coefficient. Numerous methods are available to simulate the performance of conventional plate fin heat sinks including computational fluid dynamics packages. It would be feasible to perform simulation based on conventional flat plate fin heat sinks. A cylindrical fin heat sinks could be simply treated as a plate fin heat sink, if we imagine it cut open and laid out horizontally. A theoretical model is proposed in this paper. An experimental investigation is conducted here to validate its accuracy. Convective heat transfer coefficients were experimentally determined for a horizontally and vertically inclined bare plate operating under natural and forced air cooling modes. In addition, a vertical plate fin heat sink and a vertical cylindrical fin heat si...
Analysis of natural convection in heat sink using OpenFOAM and experimental tests
Heat and Mass Transfer, 2019
A transient three-dimensional natural convection problem in heat sinks with rectangular fins positioned horizontally was studied using the software OpenFOAM (Open Field Operation and Manipulation). OpenFOAM is based on the Finite Volume Method for the discretization of the governing equations and was used to solve the three-dimensional equations of continuity, momentum and energy. These computational simulations were done with the PIMPLE solution algorithm for decoupling the equations. The NusseltCalc tool was used in the post-processing to obtain Nusselt number. The results of Nusselt number, temperature, velocity and vorticity fields were obtained. The temperature results were also obtained by numerical probes and compared with experimental and analytical results; presenting differences lower than 0.7%. The results of the average Nusselt number, Nu, and the average heat transfer coefficient by convection, h, numerically obtained with OpenFOAM were compared with the experimental and with those obtained from empirical correlation. All these results obtained with OpenFOAM presented good accordance with experiments and literature with differences lower than 10%. Uncertainty analyses were also carried out in order to prove the quality of the results and they presented differences lower than 5%. In addition, a Nusselt number correlation is proposed for Rayleight number in the range of 4.6 × 10 4 < Ra < 5.8 × 10 5 .
Effect of heat sink design on the thermal characteristic in computational fluid dynamics analysis
The thermal management in the electronic device or system using the heat sink is important to ensure the device or system operating under the allowable temperature. The present study aims to investigate the thermal characteristic (i.e., temperature distribution) of the various heat sink designs via computational fluid dynamics (CFD) analysis. The electronic cooling process of the heat sink is carried out via CFD software. The temperature distribution of the various heat sink designs (i.e., plate fin, circular pin fin and rectangular fin) was analyzed and compared. The CFD analysis revealed the plate fin heat sink has lowest temperature distribution on the fin region. High temperature distribution was observed on the pin fin heat sink. The non-uniform temperature distribution was attributed by the direction of inlet airflow, whereas the low temperature was found in the region that close to the inlet airflow. Thus, the research findings indicated the design of heat sink significantly affects the temperature distribution during the electronic cooling process.
Uluslararası Katılımlı 23. Isı Bilimi ve Tekniği Kongresi ULIBTK’21, 2021
Natural convection heat transfer is a heat transfer mechanism that is encountered frequently in daily life with its applications since it does not necessitate an additional pumping power. There are intensively used instances in numerous fields such as heating and cooling systems, cooling electronics, heat exchangers, thermic power plants, hot and cold-water pipes, and vehicle engines. Extending heat transfer surfaces is one of the frequently used options in enhancing heat transfer for heat transfer by natural convection. Pins and fins in various geometries are implanted onto the surfaces for this purpose. Triangular, square, circular and elliptical pins are prominent among most used pin fins. Geometries, numbers, and orientations of the fins are the most important parameters that affect heat transfer rate. In this study, natural convection heat transfer of square, circular, elliptical, and triangular pin and plate heat sinks having same heat transfer surface area and two different pin order configurations, i.e., inline, and staggered, were experimentally investigated. Radiation heat transfer is considered in the analysis. Pin and plate heat sinks were examined at constant heating power and experiments were done with 9 different heating powers. Those heating powers were arranged between 10 W and 50 W with 5 W increments. Nusselt (Nu) and Rayleigh (Ra) numbers were calculated using measurements and tabulated data according to the measurements. Heat transfer results are evaluated according to the drawn graphics. It was found that more heat transfer rates are possible with staggered arrangements comparing to inline arrangements.
3D analytical modelling of plate fin heat sink on forced convection
Mathematics and Computers in Simulation, 2019
With the development of embedded systems, it is crucial to reduce weight of equipments. In power converter, heat sink is a heavy part that often can be reduced in volume and weight. There are several models and methods to calculate a heat sink thermal resistance. However the more precise these methods are, the more time consuming they are and thus they can be hardly integrated in a weight optimization routine. Using analytical models to calculate heat sink thermal resistance is a good compromise between execution time and precision of results. They are usually one-dimensional models which are simple but do not take into account heat spreading effects, which is important when power electronic heat sources are small compared to their heat sink. This paper describes a threedimensional analytical model of forced convection plate fin heat sink, which will be compared with numerical simulation. A maximum difference of 2.5% has been observed between models. This analytical model will be used in an optimization routine to reduce the weight of an existing heat sink in order to show that fast and precise optimization of cooling system is possible with analytical models.