Vertical Plate Fin Research Articles

Thermal improvement of the vertical plate-fin heat sink by variable fin thickness pattern and utilizing phase change material: A numerical investigation

In this 3-D (three-dimensional) numerical study, variable fin thickness is proposed to address the thermal problem of the vertical plate-fin heat sink (PFHS) under natural convection. This design aims to facilitate heat transfer by preventing the merging of boundary layers and reducing the weight and cost of manufacturing. Simulations are carried out with COMSOL Multiphysics to solve continuity, momentum, and energy equations under a time-dependent condition. The PFHS with the dimension of 10 × 5.5 × 4.5 cm is hired with two fin convergence angles (α = 1.145, 0.572), and the number of fins and applied heat rate are varied from 4 to 7 and 2.5 W to 20 W, respectively. The numerical results show that the influence of the fin convergence angle on the thermal resistance rises by increasing fin numbers in the PFHS. The maximum reduction of 45.5 % is registered for thermal resistance in the highest density of fin numbers. Simulations are also expanded to study the PFHS under high temporary heat loads (40 and 80 W). For this, employing single and multiple PCMs for the thermal management of PFHS along with air cooling is proposed. The combined heat transfer mode results indicate that using PCM can decrease the critical temperature of PFHS by up to 8 %. Furthermore, the obtained result indicates that using multiple PCM with different melting temperatures is not advised for thermal management as it deters the full utilization of latent heat, and better performance achieves for a single PCM with a lower melting temperature.

Heat transfer characteristics of plate fin heat sink with longitudinal vortex generators

PurposeThis study aims to provide an insight into the relationship between design parameters and thermal performance of plate fin heat sinks (PFHSs) incorporating longitudinal vortex generators (VGs) inside a PFHS channel.Design/methodology/approachA computational fluid dynamics model of a delta winglet pair VG mounted inside a PFHS geometry is detailed, and the model is validated by comparison with experimental data. The validated model is used to perform a virtual design of experiments study of the heat sink with bottom plate and vertical plate mounted VGs. Data from this study is used to regress a response surface enabling the influence of each of the assessed design variables on thermal performance and flow resistance to be determined.FindingsThe results of this study show that the thermal hydraulic performances of a PFHS with bottom plate mounted VG and vertical plate fin mounted VG are, respectively, 1.12 and 1.17 times higher than the baseline PFHS. Further, the performance variation of the heat sink with VG, relative to delta winglet’s arrangement (common flow up and common flow down), trailing edge gap length and Reynolds number were also evaluated and reported.Originality/valueFor the first time, performance characteristics of delta winglet VGs mounted inside the PFHS are evaluated against different design variables and a polynomial regression model is developed. The developed regression model and computed results can be used to design high performance PFHSs mounted with delta winglet VGs.

Computational Investigation on Natural Convection Heat Transfer in Vertical Plate Fin Arrays

Objectives: To perform computational studies on different combinations of plate fin arrays of different shapes for studying their performance in natural convection heat transfer. To compare the heat transfer performance of uniform notched fins with hybrid notched fins and also performance of normal notched fins with inverted notched fins. Methods: SolidWorks Flow Simulation software is used for the present computational studies. Three types of vertical plate fin arrays viz. plain rectangular fin, rectangular fin with square notch and rectangular fin with semi-circular notch are used with their seven combinations. These fin array combinations are: plain rectangular, rectangular square notched, rectangular semi-circular notched, rectangular inverted square notched, rectangular inverted semi-circular notched, hybrid rectangular square-semi-circular notched and hybrid rectangular inverted square-semi-circular notched. Findings: The highest average heat transfer coefficient of 7.82 W/m2K is found to be for inverted hybrid square-semicircular notched fin array. This value of heat transfer coefficient is about 8% higher than compared to that with plain rectangular plate fin array (7.25 W/m2K) subjected to same operating conditions. Average heat transfer coefficients for inverted plate fin array combinations are high as compared with the non-inverted combinations. Also, hybrid plate fin arrays, whether inverted or not, show higher heat transfer coefficient values as compared with uniform notched fin arrays. Novelty : Seven types of plate fin array combinations are studied computationally. SolidWorks Flow Simulation software is used very effectively for this 3D CFD analysis. The behaviour of fluid i.e. air during natural convection flow is studied using air flow velocity trajectories. Surface contours are effectively used for studying variation in surface temperature and heat transfer coefficient at all locations of fin arrays. Keywords Natural convection, plate fin array, heat transfer coefficient, CFD, heat transfer enhancement

Free convection heat transfer analysis of slitted fin heat sink of vertical orientation using CFD

ABSTRACT The free convection heat transfer using different kinds of fins is influenced by changes in geometry and interruptions in fluid flow. This paper investigates the enhancement of natural convection heat transfer using a new slitted fin configuration over the vertical plate-fin heat sink. Two different kinds of fins configurations (rectangular plain fin and slitted fin) with a constant fin spacing was selected for investigation. Aluminium with good thermal conductivity was selected for fins and five different heat inputs are considered for the analysis. The numerical results were validated with experimental results and available theoretical correlations. The various flow patterns have been examined for vertical mounted plain and slitted rectangular fin configuration. The results demonstrated that an interruption provided in plain fins reduces the weight and improves the free convection heat transfer rate. The maximum enhancement due to the addition of the slits into the fins was found to be 69%.

Thermal Analysis of Vertical Plate Fin Heat Sink

Heat Sinks are widely used to remove the heat from the components which are generating heat during their functioning. Overheating causes malfunctioning of the components as well as it is responsible for reducing their life. Free convection is very common way of heat transfer from the heat sink considering power requirement, pressure drop and cost of the forced convection. This paper presents the thermal analysis of vertical plate fin heat sink by theoretical and experimental method at variable heat input. The results are obtained by taking experimental observations and are validated with already existing correlations suggested by various researchers in the literature.

Optimization of Fin Spacing of Vertical Plate Fin Heat Sink in Natural Convection

Heat sinks are frequently used in the cooling of electrical and electronics devices If the heat sink have very close fin spacing, it increases the surface area but reduces the heat transfer coefficient. On the other hand, if heat sink has wide fin spacing, it reduces the surface area but increases the heat transfer coefficient. Therefore, there is need to optimize the fin spacing that enhanced the heat transfer from the heat sink. A properly selected heat sink may reduced the operating temperature and reduce the risk of failure of components. A steady state natural convective heat transfer from aluminum plate fin heat sink was examined experimentally. The length and thickness of fin was kept constant while height were varied from 5mm to 25mm and spacing varied between 5.5mm to 17mm.After experimentation, it was observed that fin spacing plays important role than any other geometrical parameters. Response surface methodology is used for optimization of fin spacing. It is observed that optimum fin spacing of heat sink is 8.28mm.The error analysis is done with the help of ANN and flow visualization were done using CFD

Computational study of mixed convective heat transfer from a shrouded vertical dual-height plate fin array

Shrouded fin heat transfer has been investigated by many researchers in the recent time because of its broad applicability in engineering/industrial applications. Literature unveils the fact that almost all studies involving shrouded fin consider the fixed-height fin array. There is a limited literature in which it is predicted that dual-height fin array augments the heat transfer. These results are important since they require lesser material for enhanced heat transfer. In this present study, a computational code is developed to study the mixed convective heat transfer from a shrouded vertical dual-height plate fin array for possible improved heat transfer. Results indicate that induced velocity increases with decreasing reduced-height of fin for smaller fin spacing which enhances the heat transfer rate. Variation of friction factor multiplied by the Reynolds number (fRe) with the geometric parameters shows lower value for the case of dual-height fin array. Overall heat transfer coefficient shows improved results for the dual-height fin array involving lower Grashof numbers at different inlet velocities. But, for higher velocities, better results are noticed only in the case of larger clearances. The thermo-hydrodynamic performance parameter is found to be greater for the dual-height fin array than that of the fixed-height fin array. Computed axial pressure difference and overall Nusselt number are correlated with the governing parameters of the problem.

Natural and forced convection heat transfer coefficients of various finned heat sinks for miniature electronic systems

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 sink under natural convection were investigated. Power inputs were kept from 5 to 40 W in order to keep operating temperatures below 100 ℃. Comparison of the experimental heat transfer coefficients and those obtained from well-known existing Nusselt number correlations show that agreement was poor for the bare plate but satisfactory for the plate and cylindrical fin heat sinks. Although they are within the generally accepted range, it would be advisable for actual measurements to be carried out in order to provide more accurate sizing for thermal measurements.

Experimental and Numerical Investigation of Forced Convection Heat Transfer in Heat Sink with Rectangular Plates at Varying Inclinations on Vertical Base

Heat exchange upgrade is a vital territory of research area. Utilization of reasonable systems can bring about noteworthy specialized points of interest coming about reserve funds of cost. Rectangular plates are viewed as best balance arrangement utilized for heat exchange improvement. This gives an enlargement strategy to heat exchange with beginning of limit layer and vortex development. To assess and look at the rate of heat exchange enhancement by rectangular plate fins with differing inclinations (0°–30°–60°), shifting Re and heat supply under forced convection are the principle destinations of this study. The study is done by fluctuating introductions of fins with various inclinations, input heat supply and Re under forced convection. The coefficient of heat transfer increments observed with the expansion in air speed for all the examined designs. The coefficient of the heat transfer is discovered higher at the edge of introduction of fins at 30° for inline arrangement and 0° for staggered arrangement. Looking at both the arrangements, it is discovered that the heat transfer coefficient in 0° fin staggered arrangement is about 17% higher than 30° inline arrangement and 76% higher than the vertical plate fin. For plate fin heat sink, boundary layer formation and growth results in decrease of the coefficient of heat transfer in forced convection. This issue is overcome by accommodating some rectangular fins on the plate fin. It brings about increment of heat transfer coefficient of the RPFHS under the states of trial factors. As indicated by past research, it is discovered that examination of the plate fin heat sink with various sorts of fins for horizontal orientation is done yet but this investigation expects to discover the upgrade of transfer coefficient of plate fin heat sink for its vertical position with rectangular plates at different inclinations under the shifting scopes of heat input supply, fin arrangements and Reynolds number (Re).

Performance comparison of latent heat storage systems comprising plate fins with different shell and tube configurations

For design and optimization purposes, understanding the performance characteristics of different configurations of PCM systems during charging and discharging processes is crucial, particularly for thermal storage in CSP. A numerical study using FLUENT has been performed to explore and compare the characteristics and behavior of PCM in different shell and tube configurations; namely counter flow and parallel flow in vertical and horizontal orientations. These designs have been compared with that of an alternative design using plate fins. The main practical advantage of the alternative design is decoupling the PCM location from the path of flow of the heat transfer fluid that reduces the constraints on the materials. Confined heating/cooling pipes in a channel at the bottom of the PCM enclosure makes it more flexible to match the required working pressures, and simplifies the design and material (PCM/plate) selection. This is a significant issue as higher temperatures and pressures are being required for improving the overall solar thermal system performance. Based on the same heat transfer area, amount of PCM and input energy, a performance comparison was determined based on exergy maximization. Using sodium nitrate as the PCM, the results show a higher heat transfer rate for the vertical arrangement of plate fins compared to the counter flow shell and tube configurations, as well as a more uniform heat transfer rate compared to all shell and tube arrangements for both the charging and discharging processes. The proposed design leads to less redundant PCM, as well as a smaller and more cost effective PCM system as a heat storage unit. Overall, the vertical plate fin configuration maximizes the useful heat that can be extracted for a given amount of heat and PCM, which has direct applicability to thermal storage solutions for CSP and other applications. Moreover, its modular design facilitates the selection and optimisation for different scales and applications e.g. as a heat storage for electricity production or as a protection system for a receiver from high thermal stresses in a CSP plant.

Numerical and experimental study of natural convection heat transfer characteristics for vertical plate fin and tube heat exchangers with various tube diameters

This study uses three-dimensional computational fluid dynamics commercial package along with experimental data and various flow models to investigate the natural convection heat transfer and fluid flow characteristics of a single-tube vertical plate fin and tube heat exchangers for various values of fin spacing and tube diameter. Temperature and velocity distributions of air between the two fins, fin temperature and heat transfer coefficient on the fins are determined using FLUENT along with various flow models. The inverse method in conjunction with the finite difference method and the experimental temperature data is applied to determine the fin temperature and heat transfer coefficient for the smaller tube. More accurate results can be obtained, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. The numerical results of the fin temperature at the selected measurement locations also coincide with the experimental temperature data. The results show that RNG k–ε turbulence model is more suitable for this problem than laminar flow model. Three proposed new correlations between the Nusselt number and the Rayleigh number are in good agreement with the inverse results and numerical results obtained.

Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger

The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.

Comparative analysis of boiling and condensation heat transfer in upflow for freon R-21 in minichannels

The paper presents results of experimental investigation of heat transfer in boiling and condensation of Freon R-21 in upflow in a vertical plate-fin heat exchanger with straight and perforated fins at a small mass flow rate and heat flux, which are typical for the industry, but are insufficiently studied. Comparative analysis of heat transfer in boiling and condensation in identical conditions is performed and the influence of perforation on the heat-transfer coefficient in a wide range of equilibrium vapor quality is demonstrated.

Thermal optimization of plate-fin heat sinks with fins of variable thickness under natural convection

In this study, thermal performance of a vertical plate-fin heat sink under natural convection was optimized for the case in which the fin thickness varied in the direction normal to the fluid flow. For this optimization, the averaging approach presented in an earlier paper for the case of the heat sinks under forced convection was extended to study the performance of heat sinks under natural convection. In the case of an air-cooled heat sink, the thermal resistance decreases by up to 10% when the fin thickness is allowed to increase in the direction normal to the fluid flow. However, the difference between the thermal resistances of heat sinks with uniform thickness and the heat sinks with variable thickness decreases as the height decreases and as the heat flux decreases.

Closed form correlations for thermal optimization of plate-fin heat sinks under natural convection

In the present paper, closed form correlations that allow for thermal optimization of vertical plate-fin heat sinks under natural convection in a fully-developed-flow regime are suggested. Analytical solutions for velocity and temperature distributions for high channel aspect ratios, high conductivity ratios, and low Rayleigh numbers are presented using the volume averaging approach. To validate the analytical solutions, both experimental and numerical studies are performed, and it is shown that the analytical solutions are applicable to the range of H/wc >> 1, ks/kf > 10, and Ra″<1000. From the analytical solutions, explicit correlations for optimal fin thickness and optimal channel width, which minimize thermal resistance for given height, width, and length of heat sink, are proposed. The correlations show that the optimal fin thickness depends on the height, the solid conductivity, and the fluid conductivity only and is independent of the Rayleigh number, the viscosity of the fluid, and the length of the heat sink.

Conjugate heat transfer for free convection along a vertical plate fin

In this study, a new and effective improved Semi-Analytic and Semi-Empirical formula f(Pr)= {ie337-1} has been proposed to solve a conjugate problem with free convection in the incompressible laminar boundary layer flow and heat conduction in a solid wall for the flow passing a flat plate fin. A combination of flat-plate flow and flat-plate fin heat conduction has been considered in the present study. Finite-difference solutions for the interface temperature profiles and the heat transfer rates have been presented over the entire thermo-fluid-dynamic field for Prandtl numbers from 0.001 to 10000. First, the similar flow field has been solved by the Runge-Kutta method and the shooting methods, then the correlation equation of the local heat transfer coefficient have been obtained. Finally, the empirical formula has been substituted into the fin temperature heat conduction calculation processes to obtain the iterative solutions of the conjugate problems.

Estimation of heat transfer coefficient on the vertical plate fin of finned-tube heat exchangers for various air speeds and fin spacings

The finite difference method in conjunction with the least-squares scheme and experimental temperature data is proposed to predict the average heat transfer coefficient h ¯ and fin efficiency η f on a vertical square fin of one-circular tube plate finned-tube heat exchangers for various air speeds and fin spacings. The distribution of the heat transfer coefficient on the fin can be very non-uniform, thus the whole square fin is divided into several sub-fin regions in order to predict the h ¯ and η f values. These two predicted values can be obtained using the present inverse scheme in conjunction with the knowledge of the temperatures recordings at several selected measurement locations. The results show that the heat transfer coefficient on the upstream fin region can be markedly higher than that on the downstream fin region. The h ¯ value increases with increasing the fin spacing S and air speed V air, and the η f value decreases with increasing the S and V air values. The h ¯ and η f values respectively approach their corresponding asymptotical values obtained from a single fin as S → ∞. The distributions of the fin temperature depart from the ideal isothermal situation and the fin temperature decreases more rapidly away from the circular center with increasing the fin spacing and air speed.

Natural convection heat transfer from a thermal heat source located in a vertical plate fin

A steady state conjugate conduction–convection investigation is performed on vertical plate fin in which a small heat source is located. Heat from the fin surface is transferred to the surroundings by laminar natural convection. The governing equations for the problem are the heat conduction equation for the fin and the boundary layer equations, which are continuity, momentum and energy equations, for the fluid. A computer program is written by using the finite difference method in order to solve the governing equations which are nonlinear and coupled. The best location of the heat source in the fin for maximum heat transfer rate depends on two parameters which are the conduction–convection parameter and the Prandtl number. The obtained results have shown that for the fin with large conduction–convection parameter, a heat source location for maximum heat transfer rate exists.

Conjugate free convection from a vertical plate fin with a rounded tip embedded in a porous medium

In this paper the two-dimensional conjugate free convection in a porous medium is investigated from a vertical plate fin. Both physically and mathematically it is important to consider a smooth profile for the tip of the fin, such as a rounded tip of an arbitrary shape. Such fin shapes approximate well the rectangular fin, and their study allows a more accurate prediction of the heat transfer quantities, since no restrictive conditions have to be imposed, such as an insulated tip, and there are no singularities appearing in the mathematical formulation. The governing equations of the convective flow in the porous medium are coupled to the governing equation for the heat flow in the fin by the conditions of continuity of the temperature and the heat flux at the solid/porous media interface. The governing non-dimensional parameters are the convection–conduction parameter, N cc, and the aspect ratio of the fin, λ.

The Inverse Estimation of Local Heat Transfer Coefficient in a Vertical Plate Fin with Its Base Subjected to Periodically Oscillated Temperature

In this study, an inverse method is provided to determine the convective heat transfer coefficient of the vertical fin with its base subjected to periodically oscillated temperature. The finite-difference method is used to discretize the governing equations and then a linear inverse model is constructed to identify the undetermined heat transfer coefficients. The present approach is to rearrange the matrix forms of the differential governing equations so that the unknown heat transfer coefficients can be represented explicitly. Then, the linear least-squares-error method is adopted to find the solutions. The results show that only a few measuring points at discrete grid points are needed to estimate the unknown quantities even when measurement errors are considered. Also discussed are the effects due to the variations of the conjugate convection-conduction parameter Nc, the buoyancy parameter Ω, as well as the oscillation amplitude A and frequency ω* of the base temperature on the heat transfer coefficients. In contrast to the traditional approach, the advantages of this method are that no prior information is needed on the functional form of the unknown quantities, no initial guesses are required, no iterations in the calculating process are necessary, and the inverse problem can be solved in a linear domain. Furthermore, the existence and uniqueness of the solutions can be easily identified.