Vertical Rectangular Fin Arrays Research Articles

Investigation of thermal performance of modified vertical rectangular fin array in free convection using experimental and numerical method

Heat transfer by free convection from fin array is influenced by modification in size and shape of the fins as well as interruption in fluid flow. The objective of heat sink is the thermal management of electronic devices by removing excessive heat and improve the lifespan of the device. The paper investigates the thermal performance of free convection heat transfer with vertical heat sink by providing slits along the vertical surface of the fins. For the evaluation purpose two different arrangements viz. plain fin and slitted fin are selected. Fins are made from high thermal conductivity aluminium material and five dissimilar heat inputs are selected for study. The experimental and numerical findings are confirmed using the theoretical correlations available from the literature.The effect of number of slits and width of slits is investigated on convective heat transfer coefficient. Numerical study is used to understand the flow patterns around the vertical fin surface. It has been observed that the presence of slits on the surface appreciably improves the thermal performance of vertical fin array.

A comparative study of 2-D and 3-D conjugate natural convection from a vertical rectangular fin array with multilayered base subjected to distributed high heat flux

This paper presents a comparative numerical study of 2-D and 3-D steady, laminar conjugate natural convection heat transfer from a vertical rectangular aluminium fin array subjected to a distributed high heat flux related to the cooling of a 105 W LED street lighting luminaire. The effect of radiation is also considered in the aforementioned models. The 2-D model uses the Stream function-Vorticity-Temperature approach. The finite-difference methodology is used to discretize the governing equations. The discretization method in the 3-D model is finite-volume. The solution algorithm is SIMPLE (Semi-Implicit Method for Pressure-linked Equations). A detailed parametric study based on a realistic lamp data is conducted to observe the effect of heat flux, fin spacing, fin height, fin width, fin thickness and fin material (aluminium, brass, copper, mild steel) on the fluid (air) velocity and temperature distributions, heat transfer and LED junction temperature. A novel finding of this work is the revelation of asymmetric flow and thermal fields in the successive channels of the fin array, as predicted by the 3-D model. In contrast with the existing studies in which fin base is treated as isothermal, an optimal fin spacing is found to exist corresponding to the maximum heat transfer coefficient in the present study. The difference between 2-D and 3-D model-predicted average heat transfer coefficients increases with increase in fin height to fin spacing ratio. The contribution of radiation heat transfer is about 8–14% of the total heat transfer in the range of dimensions of the fin array considered in this work. A penalty function based optimization study is carried out to maximize the average heat transfer coefficient while maintaining the LEDs below the safe limit of 353 K. Finally, correlations for predicting the average heat transfer coefficient in the vertical rectangular fin array heat sink, and the maximum LED temperature as a function of luminaire wattage and geometric parameters of the fin array have been presented.

Optimization of Design Parameters for Lateral Circular Perforated Fin Arrays under Forced Convection

Heat dissipation is an important issue in compactness and weight of equipment. Heat dissipaters are not only chosen for their thermal performance but also for other design parameters such as weight, cost and reliability depending on applications. The present paper reports an experimental study to investigate the heat transfer enhancement over vertical rectangular fin arrays equipped with lateral circular perforations. The cross-sectional area of the rectangular duct was 200 mm × 80 mm. The data used in performance analysis were obtained experimentally for aluminum at 200 Watts heat input, by varying the fin thickness, size of perforations and varying Reynolds number range 2.1 × 104 to 8.7 × 104. Using the Taguchi experimental design method, optimum design parameters and their levels were investigated. Average Nusselt number was considered as a performance characteristics. An L9 (33) orthogonal array was selected as an experimental plan. Optimum results were found by experimenting with porosity, Reynolds number and thickness of the fin. It is observed that the Reynolds number and maximum porosity have a larger impact on Nusselt number.

A numerical study of entry region laminar mixed convection over shrouded vertical fin arrays

A computational study of laminar mixed convection over a shrouded vertical rectangular fin array attached to a vertical base has been performed. Maintaining the base-fin system above the surrounding temperature, a fan velocity is imposed to enhance the heat transfer through the mixed convection process. Present study finds the effects of clearance spacing, fin spacing, fin length, Reynolds number and Grashof number on the thermal performance of the base-fin system. Mixed convection inlet velocity is decoupled to forced and natural convection velocity components and the resulting pressure drop across the duct length arises purely due to the forced convection velocity component. Thus, Reynolds number is estimated based on forced convection velocity component as the inlet velocity does not vanish even in pure natural convection. Computed local Nusselt number shows sharp drop near the entrance and reaches a fully developed value after a certain streamwise distance from the entrance. Further, fully developed local Nusselt number shows a clear maximum at the clearance spacing of 0.075 and 0.15 for the inter-fin spacing of 0.3 and 0.5 respectively. Pressure drop across the duct, induced natural convection velocity and overall Nusselt number are well correlated with the governing parameters of the problem.

Experimental Study of Natural Convective Heat Transfer from Vertical Rectangular Fin Array at Different Angle of Inclination

Experimental Study of Natural Convective Heat Transfer from Vertical Rectangular Fin Array at Different Angle of Inclination

Optimum geometric arrangement of vertical rectangular fin arrays in natural convection

The optimal spacing between isothermal laminar natural convection plates cooled by air for maximal heat transfer has been determined analytically and numerically. It is found that the optimal plate’s allocation spacing is different from the conventional way, where the boundary layers of the plates merge early, it is the distinguishing feature of the outlet velocity that causes an enhancement of heat transfer. Further comparison results verify that our expression and numerical results and Rohsenow expression are very consistent. In the general condition, an optimized spacing expression of the maximum heat transfer density for a given volume is derived. It may be expected that the heat transfer enhancement can be accomplished by inserting multi-scale plates into the boundary layer according to the constructal theory.

Measurements of heat dissipation from miniaturized vertical rectangular fin arrays under dominant natural convection conditions

Experiments have been conducted to investigate the effects of miniaturizing the base plate dimensions of vertically based straight rectangular fin arrays on the steady-state heat-dissipation performance under dominant natural convection conditions. The miniaturization process was initiated from a square-based array of 49×49 mm2 (maximum base area) and terminated at a square-based array of 25×25 mm2 (minimum base area) with rectangular-based arrays of varying intermediate areas in between. Two inter-fin separation distances of 3 and 11 mm were used. The effect of base plate orientation on the heat-dissipation performance was studied through comparison of present results with those of an earlier work, in which the arrays were miniaturized with the base horizontally oriented. A correlation for miniaturized vertically based straight rectangular fin arrays, which employed the fin length as the prime geometric parameter, has been presented on the basis of the experimental conditions of this investigation.

Correlations for heat dissipation and natural convection heat-transfer from horizontally-based, vertically-finned arrays

Experimental data for heat dissipation from five duralumin vertical rectangular fin-arrays with the base horizontally oriented were measured. These measurements were to extend data obtained earlier from aluminum fin-arrays using the same experimental system and method. Data collated from earlier and present work covered the range of inter-fin separation distances from 6.25 to 7.95 mm. The range of the fin base excess temperature above the ambient air temperature, however, was quite extensive, from 19.0±0.1°C to 125.0±0.1°C. The fin length range was from 127 to 254 mm, the height from 6.35 to 38.10 mm, the thickness from 1.02 to 3.10 mm and the number of fins per array from 10 to 33. Relevant non-dimensional parameters formulated by earlier similarity analyses were used to generalize the data. Two types of correlations, one which used the inter-fin separation distance as the prime geometric parameter, and the other, which used half of the fin length, were presented and deviations discussed.

98/00668 Heat-exchanger performance: influence of gap width between consecutive vertical rectangular fin-arrays

98/00668 Heat-exchanger performance: influence of gap width between consecutive vertical rectangular fin-arrays

Heat-exchanger performance: Influence of gap width between consecutive vertical rectangular fin-arrays

Two identical rectangular heat-exchanger fin-arrays, with their bases in the same vertical plane, arranged in series one above the other, were used instead of a single array of double the original length fins to dissipate heat from a vertical rectangular base, which was kept at 40°C above the ambient environment. The effect of the magnitude of the gap width between the two consecutive arrays, upon the steady-state rate of heat transfer from the heated base of the exchanger under natural-convection conditions, was investigated experimentally. When a gap width of 18 ± 2 mm is used, a saving in fin material ensues together with a slight (∼ 3%) increase in the rate of heat dissipation, being achieved.

Natural convection and radiation from vertically-based arrays of vertical, rectangular fins: a numerical model

A two-dimensional numerical model has been developed for the prediction of natural convection and radiation losses from the surfaces of a vertical rectangular fin array protruding perpendicularly outwards from a vertical rectangular base. The individual contributions of the natural convection and radiation were first estimated separately and then summed to give the overall steady-state rate of heat dissipation through the heat exchanger to the ambient air. The theoretical predictions obtained using this model have been compared with experimental observations from previous investigations.

Natural-convection characteristics of a horizontally-based vertical rectangular fin-array in the presence of a shroud

The steady-state natural convective cooling of horizontally-based, vertical rectangular fins, when in close proximity to an adiabatic horizontal shroud, situated adjacent to and above the horizontal fin-tips, was investigated experimentally. The resuls are of significance for the designers of electronic arrays, the components of which should be maintained at temperatures less than 65°C in order to ensure operational reliability. The optimal fin separation, which corresponds with the maximum rate of heat loss from the fin-array, has been deduced for various combinations of fin protrusions and distances of the shroud above the vertical fins, when the fins' base was maintained at a uniform temperature of 40 ± 0·5°C above that of the environment (21·0 ± 0·5°C). For a constant temperature-difference between the fin-base and the environment, lower optimal fin separations and higher steady-state heat-dissipation rates ensued when the shroud clearance to the fin height ratio was increased from zero to unity. Increasing the fin protrusion above the horizontal base also resulted in higher heat-dissipation rates from the fin-array. However, the fin-array with maximum shroud clearance is a much more favourable configuration (e.g. with respect to requiring less material) for achieving heat-transfer enhancement, than the fin array which employs large fin protrusions. For an open-ended duct of approximately the dimensions considered in this project (i.e. of maximum rectangular section 240 mm × 180 mm), the fins should protrude to less than half the internal height of the duct in order that a high convective performance of the fins is achieved. There is an optimal value of the shroud clearance to fin height ratio which exceeds unity for each specific operation, i.e. the exact optimal ratio being dependent upon the geometry and temperatures involved. Average Nusselt numbers, evaluated from the experimental data, are correlated non-dimensionally with respect to the fin-array geometry and the Grashof number. This correlation indicates that variations of the shroud clearance to fin height ratio produce only marginal variations in the average Nusselt number.

Effect of vibration on natural convection heat transfer from vertical fin arrays

The effect of vibration on natural convection heat transfer from vertical rectangular fin arrays of different fin spacings and fin lengths was investigated experimentally. It was seen that up to a certain threshold value of the product of amplitude and frequency (15 mm/s), the imparting of vibration did not have any significant effect on heat transfer from the fin array: Beyond this value, however, the heat transfer rate increased considerably with the increase in the intensity of vibration, the maximum increase obtained being 250% when the vibrational energy input was 90 W.

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : (Part 3, Heat Transfer from Fin Flat Surfaces)

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : (Part 3, Heat Transfer from Fin Flat Surfaces)

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : Part 4, Heat Transfer Characteristics of Nonisothermal Fin Arrays

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : Part 4, Heat Transfer Characteristics of Nonisothermal Fin Arrays

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : (Part 2, Heat Transfer from Fin Edges)

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : (Part 2, Heat Transfer from Fin Edges)

Natural Convection Heat Transfer from Vertical Rectangular-Fin Arrays : Part 3, Heat Transfer from Fin-Flats

An experimental study has been made of natural convection heat transfer from the fin-flat, one of the component surfaces of a fin array ; and the effect of fin geometry and temperature on the heat transfer coefficient has been clarified. From these data and the results of the author's previous reports, an empirical formula for the average Nusselt number of vertical open-channel is derived. Furthermore, a comparison in heat transfer between open-channels and rectangular ducts has been carried out. The existence of the minimum heat transfer coefficient for the fin-length is qualitatively confirmed.

Natural Convection Heat Transfer from Vertical Rectangular-Fin Arrays : Part 2, Heat Transfer from Fin-Edges

As a sequel to the previous report of this series, the author has this time taken up the fin-edge as one component surface composing a fin array and experimentally studied natural convection heat transfer from the fin-edges in air. The effect of fin geometry and temperature on the respective heat transfer coefficients for the upper, vertical, and lower edges of fin arrays has been clarified. Furthermore, empirical formulas for the respective average Nusselt numbers are obtained. It is found that the heat transfer coefficients for the lower and vertical edges show fairly high values, e.g. 20∼30kcal/m2hr°C.

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : (Part 1, Heat Transfer from Base Plates)

Natural Convection Heat Transfer from Vertical Rectangular Fin Arrays : (Part 1, Heat Transfer from Base Plates)