Cylindrical Pin-fin Heat Sink Research Articles

Numerical Investigation of the Effect of Cooling and Heating Conditions on the Performance of Thermoelectric Module

Today, the need for energy increases, and fossil fuel resources run out rapidly so energy costs also increase rapidly. The most important feature of fossil fuels is that they consist of hydrocarbon and organic substances containing high levels of carbon. This causes great harm to the world and humanity. In the face of this dangerous situation, world states look for new and clean energy sources. As a result, the trend towards renewable energy sources increases rapidly. In this context, TE (thermoelectric) module is an important source to convert heat to electrical energy. The amount of electricity generation from heat depends on the temperature difference between surfaces of the TE module. The electrical power obtained from heat increases with the increase of temperature difference. This work aims to investigate numerically the heat transfer and electricity generation performance of a 〖Bi〗_2 〖Te〗_3-based TE module embedded with cylindrical pin-fin heat sink under the different hot surface and air temperature conditions with different air velocities. The results were evaluated and discussed with parameters such as temperature distribution, power input, power output, voltage output, current output, temperature difference, total thermal resistance, conversion efficiency and Nusselt number according to Reynolds numbers. In all analyses, it was observed that performance of the heat transfer and electricity generation of the TE module increase with the increase in Reynolds number. The highest conversion efficiency was obtained generally at surface temperatures of 200℃, specifically at air temperature of 5℃ and the Reynolds number of 20000. In addition, it was observed that the temperature difference between the surfaces of the TE module is not sufficient alone to give good performance and besides, it is necessary to keep the cold surface at low temperature.

Experimental investigations of conical perforations on the thermal performance of cylindrical pin fin heat sink

This paper deals with experimental investigations of heat transfer and friction factor characteristics of perforated pin fin heat sink tested in a rectangular channel by using forced convection. Cylindrical pin fins with conical perforations on the lateral surface area were arranged in staggered arrays on the base plate to form heat sink. Two combinations, such as solid fins and fins with conical perforations, were compared. The effect of number of conical perforations and size of conical perforation on thermal performance of heat sink was studied in detail. The heat sinks were subjected to variable air flow rate (10,000 ≤ Re≥ 30,000) in the turbulent regime and constant heat flux input. The results found that with an increase in the number of conical perforations from 2 to 5 results in higher heat dissipation rates and lower pressure drop. With an increase in the size of conical perforation, heat transfer rate initially increases, attains maximum values and then decreases. This is due to the reduction in vertical heat transfer rate through fin by conduction, which shows adverse effects on the overall heat transfer rate by convection. The purpose of using conical perforation instead of circular perforation was to increasethe velocity of air passing through perforation. This affects the turbulence of working fluid at heatsink and ultimately influences heat transfer rate from heat sink.

Constructal design progress for eight types of heat sinks

This review paper summarizes constructal design progress performed by the authors for eight types of heat sinks with ten performance indexes being taken as the optimization objectives, respectively, by combining the methods of theoretical analysis and numerical calculation. The eight types of heat sinks are uniform height rectangular fin heat sink, non-uniform height rectangular fin heat sink, inline cylindrical pin-fin heat sink (ICPHS), plate single-row pin fin heat sink (PSRPHS), plate inline pin fin heat sink (PIPHS), plate staggered pin fin heat sink (PSPHS), single-layered microchannel heat sink (SLMCHS) with rectangular cross sections and double-layered microchannel heat sink (DLMCHS) with rectangular cross sections, respectively. And the ten performance indexes are heat transfer rate maximization, maximum thermal resistance minimization, minimization of equivalent thermal resistance which is defined based on the entransy dissipation rate (equivalent thermal resistance for short), field synergy number maximization, entropy generation rate minimization, operation cost minimization, thermo-economic function value minimization, pressure drop minimization, enhanced heat transfer factor maximization and efficiency evaluation criterion number maximization, respectively. The optimal constructs of the eight types of heat sinks with different constraints and based on the different optimization objectives are compared with each other. The results indicated that the optimal constructs mostly are different based on different optimization objectives under the same boundary condition. The optimization objective should be suitable chosen based on the focus when the constructal design for one heat sink is performed. The results obtained herein have some important theoretical significances and application values, and can provide scientific bases and theoretical guidelines for the thermal design of real heat sinks and their applications.

Design and development of a heatsink for thermo-electric power harvesting in aerospace applications

In recent years, the growing interest of aerospace companies in wireless structural health monitoring (SHM) systems has led to the research of new energy efficient sources and power harvesting solutions. Among available environmental power sources, temperature gradients originated at different locations of the aircraft can be used by thermo-electric generators (TEGs) to create electrical voltage. TEGs are lightweight, provide high-energy conversion and do not contain movable parts. Thermal diffusion systems, commonly known as heatsinks, can be combined with TEGs to enhance their performance by increasing heat dissipation from a high temperature surface to the ambient air. This paper focused on the enhancement of TEG performance by developing an air-cooled heatsink for low-power wireless SHM applications. The design, manufacturing and testing of the proposed thermal diffusion system was investigated by evaluating the increase of the temperature gradient between the opposite surfaces of a commercial TEG element. The thermal performance of the heatsink was assessed with numerical finite element thermal simulations and validated with experimental tests. Experimental results revealed that the proposed thermal diffusion system provided higher temperature differences and, therefore, higher output power in comparison with traditional cylindrical pin-fin heatsinks. A hybrid heat diffusion system composed by copper heatsinks and highly oriented pyrolytic graphite layers was also here proposed in order to allow TEG reaching wireless SHM operative power requirements of tens of mW and, at the same time, adapt the assembly to the complexity of aerospace SHM arrangements. Experimental results revealed that the proposed heatsink-TEG arrangement was able to generate an output power over 25 mW.

Constructal operation cost minimization for in-line cylindrical pin-fin heat sinks

Second-law-based minimum operation cost optimization is performed based on constructal theory for in-line cylindrical pin-fin heat sinks (PFHS). With the minimum operation cost which is based on the entropy generation rate (EGR) as the objective, the optimal values of diameter, height to diameter aspect ratio and quantity of cylindrical pin-fin are achieved by combining the analytical and numerical method, the effects of fin-material fraction (FMF), heat transfer load (HTL) of the PFHS, fluid velocity (FV) and cost ratio on variations of the operation cost of the PFHS with the diameter of pin-fin are analyzed. The results indicate that when the single freedom degree optimization is performed, the minimum operation cost and the optimum constructs are various under various FMF, the HTL, the FV and the cost ratio in the research range of parameters; when the double freedom degree optimization is carried out, the operation cost of the PFHS increases with the height to width aspect ratio of the PFHS increasing.

Comparison of heat sink and water type PV/T collector for polycrystalline photovoltaic panel cooling

Abstract Cylindrical pin fin heat sinks are not used to cool a panel, which we have done so in the present work and tested it's performance against a traditional single-channel PV/T collector. An older 20 Watt polycrystalline solar cell photovoltaic panel with a standard efficiency of 11.7% is elevated to a high temperature by indoor halogen light of intensity 1378.4 W m−2 in this study. The temperature of 81.7 ± 2.3 °C temperature at the front and 88.6 °C at the rear under at 0 m2 s−1 wind speeds are lowered using a cylindrical pin fin heat sink (fin density 1.22 fin cm−2). A channel of aspect ratios α* = 0.08 was attached to the rear of the panel as the collector configuration. Temperatures dropped to 58.4 °C with heat sink and 47.9° using the collector. The analysis suggests that heat flux of 667.2 W m−2 at the rear of the bare panel with no cooling is enhanced by 30 and 41.5% by the heat sink and PV/T collector by natural methods. We strongly urge exploration of using the cylindrical pin fin heat sinks to cool the panel under stagnant wind conditions.

Constructal entropy generation rate minimization for cylindrical pin-fin heat sinks

Optimization of in-line cylindrical pin-fin heat sinks (PFHS) is carried out by using constructal theory and entropy generation minimization (EGM) theory for fixed total heat sink volume and fin-material volume. The optimal constructs of cylindrical pin-fin are obtained by taking the minimum entropy generation rate (MEGR) as objective, and the influences of fin-material fraction, heat transfer load (HTL) of the heat sink and the fluid velocity on the optimization results are studied. It is shown that there exists optimal diameters makes the EGR minimized for the fixed shape of the heat sink; the MEGR decreases, the corresponding optimal diameter and number of cylindrical pin-fin increase as the fin-material fraction increases; the MEGR increases, the corresponding optimal diameter and number of cylindrical pin-fin decrease as the HTL and the fluid velocity increase, respectively; when the shape of the heat sink can be morphed freely, the MEGR increases as the aspect ratio of the heat sink increases, and the corresponding optimal geometric parameters are different, which means there is no quadratic optimal constructs for the heat sink by taking MEGR as optimal objective. That is the less MEGR can be obtained by choosing the more fin-material fraction, the lower fluid velocity and the smaller aspect ratio of the heat sink in allowed range. The results can provide theoretical support for the MEG optimization design of in-line cylindrical PFHS.

Constructal heat transfer rate maximization for cylindrical pin-fin heat sinks

Constructal optimization of the whole cylindrical pin-fin heat sinks (PFHS) is performed by the finite volume method (FVM). Maximum dimensionless heat transfer rate (MDHTR) is taken as the objective for fixed total heat sink volume and fin-material volume, and pressure drop is used to evaluate the hydraulic performance of the system. Variation of the dimensionless heat transfer rate (DHTR) and its corresponding pressure drop along the diameter of cylindrical pin-fin is studied, and the influences of the volume fraction and fluid velocity on the results are analyzed, and the flow field and temperature distribution of PFHS are shown. The results show that there exists an optimal diameter which corresponds to an optimal number of pin fins makes the DHTR maximized when the shape of PFHS is fixed, the MDHTR and its corresponding pressure drop and optimal constructs are different for different volume fraction; there exists an optimal aspect ratio of the PFHS which makes the MDHTR maximization. The sensitivity of heat transfer performance to the fin-material fraction is higher than hydraulic performance does, but with respect to the fluid velocity and the aspect ratio of PFHS, the sensitivity of hydraulic performance is higher. The results of this paper can provide theoretical support for the optimization design of cylindrical PFHS.

Thermal Simulation Analysis of High Power LED with Varied Heat Sink Fin Design

In this paper, the heat distribution for single chip high power LED package attached with varied heat sink fin shapes were analyzed through simulation. The main focus of this study was to scrutinize the fluctuation of junction temperature with different shapes of heat sink fin designs. The simulation was done using Ansys version 11. The single chip LED was loaded with input power of 0.5 W and 1 W . Simulation was done at ambient temperature of 25°C under three convection coefficient of 5, 10 and 15 W/m2.oC respectively. The obtained results showed that the LED package with pyramid pin fin heat sink has demonstrated a better thermal performance compared to the LED package with cylindrical pin fin heat sink.

Dynamic simulation, optimal design and control of pin-fin heat sink processes

This paper considers the dynamic simulation, optimal design and direct adaptive control of cylindrical pin-fin heat sink processes. For dynamic heat-dispersion investigation of the pin-fin heat sinks, a 3D model that includes the heat transfer from the heat source to fins and the forced convective heat transfer by a horizontal air-cooling fan is proposed. To optimize the heat dispersion performance, a real-coded genetic algorithm is applied to search for a set of optimal fin-shape parameters and operation conditions. The objective function to be minimized is the entropy generation rate that is able to account for air resistance as well as the heat transfer resistance simultaneously. The comparisons with existing methods show that the obtained optimal design is much better in performance and at the same time is superior in energy savings. Furthermore, to ensure excellent heat dispersion performance when facing environmental and time-varying disturbances, a direct adaptive control system for the temperature regulation of the pin-fin heat sink processes is implemented. The control system is developed using a single-parameter, nonlinear controller along with a parameter-tuning algorithm. A Lyapunov theorem is applied to ensure the stability of the direct adaptive control system. Additionally, extensive simulation results reveal that the proposed direct adaptive control system outperforms conventional on-off and PI controllers, providing a significantly much better heat dispersion performance despite the existence of unexpected environmental variations and disturbances.

Thermal and hydraulic performance analysis of cylindrical pin fin heat sink with conical perforations

Thermal and hydraulic performance analysis of cylindrical pin fin heat sink with conical perforations

Optimization of Pin-Fin Heat Sinks in Bypass Flow Using Entropy Generation Minimization Method

An entropy generation minimization method is applied to study the thermodynamic losses caused by heat transfer and pressure drop for the fluid in a cylindrical pin-fin heat sink and bypass flow regions. A general expression for the entropy generation rate is obtained by considering control volumes around the heat sink and bypass regions. The conservation equations for mass and energy with the entropy balance are applied in both regions. Inside the heat sink, analytical/empirical correlations are used for heat transfer coefficients and friction factors, where the reference velocity used in the Reynolds number and the pressure drop is based on the minimum free area available for the fluid flow. In bypass regions theoretical models, based on laws of conservation of mass, momentum, and energy, are used to predict flow velocity and pressure drop. Both in-line and staggered arrangements are studied and their relative performance is compared to the same thermal and hydraulic conditions. A parametric study is also performed to show the effects of bypass on the overall performance of heat sinks.

Effect of Bypass on Overall Performance of Pin-Fin Heat Sinks

DOI: 10.2514/1.27544 Oneofthemostimportantfactorsinfluencingtheoverallperformanceofcylindricalpin-finheatsinksisthebypass phenomenon. Depending upon the total bypass area in comparison to the flow area between pin fins, a significant portion of the approaching airflow bypasses the heat sink. In this study, the effects of side and top bypass on the hydraulic and thermal performances of a cylindrical pin-fin heat sink will be investigated in laminar forced convection. Theoretical models, based on laws of conservation of mass, momentum, and energy, are developed to predict flow velocity, pressure drop, and heat transfer from the heat sink and the bypass regions. These models will help in determining hydraulic and thermal resistances in each region. Both in-line and staggered arrangements are analyzed in this study. Analytical andempirical correlations are used to determine friction factors and heat transfer coefficients in both arrangements. The effects of thermal spreading and joint resistances are neglected in this study. Nomenclature Ab

Performance of Shrouded Pin-Fin Heat Sinks for Electronic Cooling

The objective of this study is to analyze the performance of a cylindrical pin-fin heat sink in laminar forced convection. The mathematical models are presented for predicting thermal and hydraulic resistances for both in-line and staggered arrangements. Analytical/empirical correlations of friction and heat transfer coefficients are used in the analysis. The analyses are performed by using parametric variation of resistances. The effects of thermal joint, spreading, and contact resistances as well as the thermal conductivity on the overall thermal performance are examined. For a given size and heat load, it is observed that the overall performance of a pin-fin heat sink depends on a number of parameters including the dimensions of the pin-fins, pin density, longitudinal and transverse spacings, interface material, location and size of heat sources, method of manufacturing, type of heat-sink material, approach velocity, and arrangement of pins. It is also observed that the thermal resistance decreases whereas pressure drop increases with an increase in approach velocity, pin diameter, and pin density. Nomenclature Ab = area of the base plate ≡ L × W ,m 2 Ac = cross-section or contact area of a single pin, m 2 Afin = surface area of a single pin, m 2 Ahs = surface area of heat sink, m 2 CV = control volume D = pin diameter, m f = friction factor H = pin height, m h = average heat transfer coefficient, W/m 2 · K he = uniform effective film coefficient, W/m 2 · K k = thermal conductivity, W/m · K ks = harmonic mean thermal conductivity for the two solids, W/m · K L = length of heat sink in flow direction, m m = fin performance parameter, m −1 N = total number of pins in heat sink ≡ NT NL NL = number of pins in the longitudinal direction NT = number of pins in the transverse direction Nu D = Nusselt number based on pin diameter ≡ Dh/k f P = contact pressure, N/m 2 Pr = Prandtl number ≡ ν/α Q = total heat transfer rate, W Rc = contact resistance between fins and the baseplate, K/W R f = total resistance of fluid side of heat sink, K/W Rfilm = thermal resistance of exposed (unfinned) surface of the baseplate, K/W Rfin = resistance of a fin, K/W R j = thermal joint resistance between the source and the baseplate, K/W Rm = material resistance of the baseplate, K/W Rs = thermal spreading resistance in the baseplate, K/W

Optimization of pin-fin heat sinks using entropy generation minimization

In this study, an entropy generation minimization, EGM, technique is applied as a unique measure to study the thermodynamic losses caused by heat transfer and pressure drop in cylindrical pin-fin heat sinks. The use of EGM allows the combined effect of thermal resistance and pressure drop to be assessed through the simultaneous interaction with the heat sink. A general expression for the entropy generation rate is obtained by considering the whole heat sink as a control volume and applying the conservation equations for mass and energy with the entropy balance. Analytical/empirical correlations for heat transfer coefficients and friction factors are used in the optimization model, where the characteristic length is used as the diameter of the pin and reference velocity used in Reynolds number and pressure drop is based on the minimum free area available for the fluid flow. Both in-line and staggered arrangements are studied and their relative performance is compared on the basis of equal overall volume of heat sinks. It is shown that all relevant design parameters for pin-fin heat sinks, including geometric parameters, material properties and flow conditions can be simultaneously optimized.