Strip Fin Heat Sink Research Articles

Effect of local hot spots on flow boiling in a parallel strip fin heat sink

The present study experimentally explored the flow boiling phenomena in mini-scale heat sinks under local heating conditions. A parallel strip fin heat sink (PSFHS) and a mini-channel heat sink (MCHS) are comparatively tested using R141b as working fluid. Nine separate spot-heaters are uniformly attached to the backside of the heat sinks to simulate the non-uniform heating condition. Thermocouples integrated in the nine heaters are used to gain the temperature profile. It can be found that the two-dimensional expansion of vapor in PSFHS improves the distribution of vapor and reduces the local vapor quality. Besides, the additional nucleation sites produced by the interrupted configuration of PSFHS generate more bubbles enhancing the local flow boiling. However, the bubbles coalesce and form slugs continuously, which would weaken the inflow of the working fluid. It is concluded that the temperature rise at the hot-spot location is significantly influenced by the structural configuration of the heat sinks. It is noted that for mini-scale heat sinks designed for hot-spot cooling, the interrupted channel configuration has a difference with the continuous channel configuration, but perhaps not significant.

Flow Boiling in a Parallel Strip Fin Heat Sink With Nonuniform Heat Flux Conditions

Abstract This study investigates the thermal performance of a parallel strip fin heat sink (PSFHS) under various heat flux conditions at a flowrate of 100 ml/min, including uniform heat flux and nonuniform heat flux. The heat sink consists of 150 fins with a width of 1 mm, a height of 5.5 mm, and a pitch of 1 mm and has a Z-type inlet/outlet arrangement. Nine separate heaters offer thermal load to the heat sink in order to provide a uniform or nonuniform heat flux. The flow boiling process is captured by a high-speed camera. The temperatures of the heaters have been measured under the uniform and nonuniform heat flux conditions. In addition, the pressure drops inside the heat sink are also obtained. A minichannel heat sink (MCHS) with the same channel dimensions and inlet/outlet configuration is tested too. A comparison between MCHS and PSFHS is discussed in detail, which helps to understand the flow boiling characteristic in PSFHS.

Influence of inlet/outlet arrangement on flow boiling of a parallel strip fin heat sink

This paper experimentally investigates a parallel strip fin heat sink (PSFHS) with various types of inlet/outlet arrangements (IOAs) including I-type, L-type, and U-type. The heat sink contains 150 fins 1 mm wide and 5.5 mm high on a square in-line configuration with a 1 mm pitch. Nine thermocouples are placed inside the base plate of the heat sink to map the temperature distribution in it. Because of the difference in IOAs, the resultant temperature distributions are different. The corresponding boiling curves and flow pattern are discussed in detail. In addition, the two-phase thermal resistance and temperature uniformity are utilized to evaluate the thermal performance of the heat sink. The experiment results show that the inlet/outlet arrangements have a significant influence on local dry out and temperature distribution, both of which are also affected by the discontinuous passage configuration. It is found that L-type PSFHS has relatively small thermal resistance with a moderated temperature uniformity, and I-type PSFHS has the worst performance in temperature distribution.

A Modification of Offset Strip Fin Heatsink with High-Performance Cooling for IGBT Modules

For reliability and thermal management of power devices, the most frequently used technique is to employ heatsinks. In this work, a new configuration of offset strip fin heatsink based on using the concept of curvy fins and U-turn is proposed with the aim of improving the heat transfer performance. With this aim, a three-dimensional model of heatsink with Silicon Insulated-Gate Bipolar Transistors (IGBTs) and diodes, solder, Direct Bonded Copper (DBC) substrate, baseplate and thermal grease is developed. Richardson’s extrapolation is used for increasing the accuracy of the numerical simulations and to validate the simulations. To study the effectiveness of the new offset design, results are compared with conventional offset strip fin heatsink. Results show that in aspects of design of heatsinks (including heat transfer coefficient, maximum chip temperature and thermal resistance), the new introduced model has advantages compared to the conventional offset strip fin design. These enhancements are caused by the combination of the longer coolant passage in the heatsink associated with generation of disturbance and recirculation areas along the curvy fins, creation of centrifugal forces in the U-turn, and periodic breaking up boundary layers. Also, it is shown that due to narrower passage and back-and-forth route, the new introduced design can handle the hot spots better than conventional design.

A numerical investigation of thermal airflows over strip fin heat sinks

The benefits of using strip fin heat sinks (SFHSs) where the cross-sectional aspect ratio of the fins lie between those for plate fins (high aspect ratio) and pin fins (aspect ratio≈1) are explored computationally, using a conjugate heat transfer model. Results show that strip fins provide another effective means of enhancing heat transfer, especially when staggered arrangements of strip fins are used. A detailed parameter investigation demonstrates that perforating the strip fins provides additional improvements in terms of enhanced heat transfer, together with reduced pressure loss and heat sink mass. Results are also given which show that, for practical applications in micro-electronics cooling, perforated SFHSs offer important benefits as a means of achieving smaller processor temperatures for reduced mechanical power consumption.

Thermal Analysis of Air-Cooled Electronic Units With Integrated Offset Strip-Fin Heat Sink

This short communication addresses a numerical investigation of the thermal behavior of an electronic unit. The unit consists of several parallel planes and on the top and bottom planes heat is generated by a number of electronic chips. The heat is transported by conduction through plastic and copper-invar layers. Finally, the heat is rejected by a forced air stream in the center of the unit. The channel system for the cooling air is designed as an offset strip fin surface. A three-dimensional numerical method based on a thermal resistance or conductance network has been developed. The grid points on the cooling air side are staggered compared to the grid points in the solid materials. Details of the numerical method as well as some temperature distributions on the chip planes are provided.

Multi-objective thermal design optimization and comparative analysis of electronics cooling technologies

A multi-objective thermal design optimization and comparative study of electronics cooling technologies is presented. The cooling technologies considered are: continuous parallel micro-channel heat sinks, in-line and staggered circular pin-fin heat sinks, offset strip fin heat sinks, and single and multiple submerged impinging jet(s). Using water and HFE-7000 as coolants, Matlab’s multi-objective genetic algorithm functions were utilized to determine the optimal thermal design of each technology based on the total thermal resistance and pumping power consumption under constant pressure drop and heat source base area of 100mm2. Plots of the Pareto front indicate a trade-off between the total thermal resistance and pumping power consumption. In general, the offset strip fin heat sink outperforms the other cooling technologies.

Analysis of Convective Thermal Resistance in Ducted Fan-Heat Sinks

The thermal performance of plate fin, round pin-fin, and offset strip-fin heat sinks with a duct-flow type fan arrangement was analytically evaluated. Heat sinks of 65mmtimes60 mm plan areatimes50 mm height with a 4300-RPM dc fan (60mmtimes15mm) were chosen for the performance comparison. A constant temperature, 6-mm thick heat sink base plate is assumed so that thermal spreading resistance is not involved. The operating point on the fan curve is based on the flow pressure drop impedance curve through a heat sink using the friction factor correlation for the chosen heat sink. The loss coefficients at both the entrance and the exit of the heat sink are included in the flow impedance curve. The operating point is defined by the balance point of the flow impedance curve and the fan performance curve. After determining the operating air velocity, the convective thermal resistance of heat sinks is evaluated from the Nusselt number correlation for the chosen heat sink. Results obtained show that optimized round pin-fin heat sinks provide 32.8%-46.4% higher convective thermal resistance compared to an optimized plate-fin heat sink. The optimized offset strip-fin heat sink shows a slightly lower convective thermal resistance than the plate-fin heat sink. As the offset strip length decreases, however, thermal performance seriously deteriorates

스트립휜 히트싱크의 냉각특성

Air-cooled heat sinks are employed in many eletronic cooling applications since they provide significant heat transfer enhancement and operational flexibility. Strip-shaped fin heat sink is of interest and needs to be investigated as general cooling products for more applicability. The purposes of this study are to evaluate heat sink performance without bypass flow condition and to determine optimal heat sink geometries. The results show that the decreasing rate of thermal resistance of a heat sink decreases with increasing inlet air velocity, and the increasing rate of pressure drop increases with increasing inlet air velocity, but is not affected by input power. The increasing rate of optimal longitudinal fin spacing is larger than that of transverse fin spacing. The strip fin heat sink tested in this study showed better cooling performance compared to that of other plate fin type.

Modeling of the thermal and hydraulic performance of plate fin, strip fin, and pin fin heat sinks-influence of flow bypass

Tests have been conducted in a wind tunnel with seven types of heat sinks including plate fin, strip fin, and pin fin heat sinks. In the case of strip fin, and pin fin heat sinks, both in-line and staggered arrays have been studied. The pin fin heat sinks had circular and square cross-sections. For each type, tests were run with fin heights (H) of 10, 15, and 20 mm while the heat sink width (B) was kept constant and equal to 52.8 mm. In total, 42 different heat sinks were tested. The width of the wind tunnel duct (CB) was varied in such a way that results were obtained for B/CB=0.84, 0.53, and 0.33. The wind tunnel height (CH) was varied similarly, and data were recorded for H/CH=1, 0.67, and 0.33 while the duct Reynolds number was varied between 2000 through 16500. An empirical bypass correlation has been developed for the different fin designs. The correlation predicts the Nusselt number and the dimensionless pressure drop and takes into account the influence of duct height, duct width, fin height, fin thickness, and fin-to-fin distance. The correlation parameters are individual for each fin design. Further, a physical bypass model for plate fin heat sinks has been developed to describe the bypass effect.