共查询到20条相似文献,搜索用时 31 毫秒
1.
The paper presents the thermal and hydrodynamic analysis of the micro-heat sink with straight microtubes and multiple inlet jets. The inlet cross-sections have the rectangular shape and positioned tangentially to the tube axis. Four different configurations are considered: three of them with three inlet jets and one with five inlet jets. The fluid flow regime is laminar and water with variable fluid properties is used as a working fluid. The heat flux spread through the bottom surface of the heat sink is q = 100 W/cm2. Thermal and hydrodynamic results of the micro-heat sink with multiple inlets are compared with results obtained for single tangential inlet configuration. For all cases, the analysis is made on a fixed pumping power basis. The strong dependence of the position and number of the inlet jets on thermal and hydrodynamic characteristics of the micro-heat sink is observed. 相似文献
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N. García-Hernando A. Acosta-Iborra U. Ruiz-Rivas M. Izquierdo 《International Journal of Heat and Mass Transfer》2009,52(23-24):5433-5446
This work presents an experimental analysis of the hydrodynamic and thermal performance of micro-heat exchangers. Two micro-heat exchangers, characterized by microchannels of 100 × 100 and 200 × 200 μm square cross-sections, were designed for that purpose. The fluid used was deionized water and there was no phase change along the fluid circuit. The fluid pressure drop along the heat exchanger and the heat transfer were measured and corrections were made to isolate the contribution of the microchannels. The results were compared with the predictions of the classical viscous flow and heat transfer theory. The main conclusions show that the experimental results fit well with these theories. No effects of heat transfer enhancement or pressure drop increase were observed as a consequence of the small scale of the microchannels. 相似文献
3.
Irfan Karagoz Fuat Kaya 《International Communications in Heat and Mass Transfer》2007,34(9-10):1119-1126
This work presents a computational fluid dynamics (CFD) calculation to investigate the flow field and the heat transfer characteristics in a tangential inlet cyclone which is mainly used for the separation of the dens phase of a two phase flow. Governing equations for the steady turbulent 3D flow were solved numerically under certain boundary conditions covering an inlet velocity range of 3 to 30 m/s. Finite volume based Fluent software was used and the RNG k − turbulence model was adopted for the modeling highly swirling turbulent flow. Good agreement was found between computed pressure drop and experimental data available in the literature. The structure of the vortices and variation of local heat transfer were studied under the effects of inlet velocity. 相似文献
4.
Numerical modeling of the conjugate heat transfer in microchannel heat sink is presented. As the most of the cooling applications deals with the partial heated sections, the influence of the heating position on the thermal and hydrodynamic behavior is analyzed. The laminar fluid flow regime and the water as a working fluid are considered. It is observed that partial heating together with variable viscosity has a strong influence on thermal and hydrodynamic characteristics of the micro-heat sink. 相似文献
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《International Journal of Heat and Mass Transfer》2005,48(21-22):4498-4509
An analytical model for fluid flow and heat transfer in a micro-heat pipe of polygonal shape is presented by utilizing a macroscopic approach. The coupled nonlinear governing equations for fluid flow, heat and mass transfer have been modified and have been solved analytically. The analytical model enables us to study the performance and the limitations of such a device and provides the analytical expressions for critical heat input, dry-out length and available capillary head for the flow of fluid. A dimensionless parameter, which plays an important role in predicting the performance of a micro-heat pipe, is obtained from the analytical model. The results predicted by the model compared with the published results in literature and good agreement has been obtained. The general and analytical nature of the simple model will have its applicability in the design of micro-heat pipes. 相似文献
6.
Amir Shalchi-Tabrizi Hamid Reza Seyf 《International Journal of Heat and Mass Transfer》2012,55(15-16):4366-4375
Effect of using Al2O3–water nanofluids with different volume fractions and particle diameters on generated entropy, hydrodynamic performance and heat transfer characteristics of a tangential micro-heat sink (TMHS) was numerically investigated in this research. Results indicated that considerable heat transfer enhancement is possible when using Al2O3–water nanofluids as coolant and clearly the enhancement improves with increasing particles concentration and decreasing particles size. However, using nanofluid has also induced drastic effects on the pumping power that increases with particles volume fraction and Reynolds number. Finally, it was found that generated total entropy decreases with increasing volume fraction and Reynolds number and decreasing particles size. 相似文献
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The purpose of this study is to explore the viscous dissipation stimulus on the steady convective magnetohydrodynamic shear thickening liquid stream across a vertically stretched sheet. The impact of thermic heat, first-order velocity slip, and variable heat generation/absorption are considered and also ignored the effect of magnetic Reynold's number. We converted flow controlling equations into the set of dimensionless nonlinear ordinary differential equations by employing similarity variables to solve these coupled equations by R–K and shooting technique. The effect of different dimensionless variables on velocity, heat, friction factor, and local Nusselt numbers are presented through graphs and tables. Depreciation in velocity and growth in temperature distribution is detected when the Casson fluid parameter is increased. Temperature is the increasing function of the Eckert number. 相似文献
9.
弯曲微热管阵列传热性能的实验研究 总被引:1,自引:0,他引:1
微热管阵列是一种导热能力较强的元件,具有接触面积大、热输运能力强和承压能力强的特点。将750 mm长的微热管阵列分别弯曲成"L"形和"乙"字形,测试其在热源温度为45℃条件下的响应时间及轴向均温性,并与平直微热管阵列对比,分析弯曲对微热管阵列传热性能的影响。结果表明:弯曲会使微热管阵列响应时间滞后,"L"形、"乙"字形1号和"乙"字形2号微热管阵列响应时间约为120 s,较平直微热管阵列滞后80 s;弯曲微热管阵列两端温差随弯道数的增加而增大,随弯曲角度的增大而增大,"L"形和"乙"字形1号微热管阵列蒸发段与冷凝段温差分别为0.76℃、1.61℃,较平直微热管阵列大11.76%、106.41%;"乙"字形2号微热管阵列两端温差为1.70℃,比"乙"字形1号微热管阵列两端温差大10.84%。 相似文献
10.
Numerical simulation of fluid flow and heat transfer in a microchannel heat sink with offset fan-shaped reentrant cavities in sidewall 总被引:1,自引:0,他引:1
Lei ChaiGuodong Xia Mingzheng ZhouJian Li 《International Communications in Heat and Mass Transfer》2011,38(5):577-584
The paper is focused on the investigation of fluid flow and heat transfer characteristics in a microchannel heat sink with offset fan-shaped reentrant cavities in sidewall. In contrast to the new microchannel heat sink, the corresponding conventional rectangular microchannel heat sink is chosen. The computational fluid dynamics is used to simulate the flow and heat transfer in the heat sinks. The steady, laminar flow and heat transfer equations are solved in a finite-volume method. The SIMPLEX method is used for the computations. The effects of flow rate and heat flux on pressure drop and heat transfer are presented. The results indicate that the microchannel heat sink with offset fan-shaped reentrant cavities in sidewall improved heat transfer performance with an acceptable pressure drop. The fluid flow and heat transfer mechanism of the new microchannel heat sink can attribute to the interaction of the increased heat transfer surface area, the redeveloping of the hydraulic and thermal boundary layers, the jet and throttling effects and the slipping over the reentrant cavities. The increased heat transfer surface area and the periodic thermal developing flow are responsible for the significant heat transfer enhancement. The jet and throttling effects enhance heat transfer, simultaneously increasing pressure drop. The slipping over the reentrant cavities reduces pressure drop, but drastically decreases heat transfer. 相似文献
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A numerical study is conducted to predict the thermal performance of a parallel flow two-layered microchannel heat sink on heat transfer and compared to the case of counterflow for various channel aspect ratios. Findings reveal that the parallel flow configuration leads to a better heat transfer performance except for high Reynolds number and high channel aspect ratio. Further study on the horizontal rib thickness shows that lower thermal resistance can be achieved in a parallel flow two-layered microchannel heat sink with smaller thickness of middle rib. 相似文献
13.
Paisarn Naphon Setha Klangchart Somchai Wongwises 《International Communications in Heat and Mass Transfer》2009,36(8):834-840
Fluid flow and heat transfer in the mini-rectangular fin heat sink for CPU of PC using de-ionized water as working fluid are numerically investigated. Based on the real PC operating conditions, the three-dimensional governing equations for fluid flow and heat transfer characteristics are solved using finite volume scheme. The standard k–ε turbulent model is employed to describe the flow structure and behavior. The predicted results obtained from the model are verified by the measured data. There is a reasonable agreement between the predicted results and experiments. The results of this study are expected to lead to guidelines that will allow the design of the cooling system with improved cooling performance of the electronic equipments increasing reliable operation of these devices. 相似文献
14.
《International Journal of Heat and Mass Transfer》2007,50(15-16):3100-3114
A developing micro-channel heat transfer and fluid flow has been investigated experimentally in rectangular micro-channels of Dh = 440 μm, having water as a working fluid. Infrared technique was used to design and built a micro-channel test section that incorporate internal fluid temperature measurements. The new method that provides information about the fluid temperature distribution inside the channel and provides validation for the methods used to determine the local and average Nusselt numbers. The experimental results have been compared with theoretical predictions from the literature and results obtained by numerical modeling of the present experiment. The experimental results of pressure drop and heat transfer confirm that including the entrance effects, the conventional theory is applicable for water flow through micro-channels.These results differ from the conclusions of several researches. It was shown that data presented by some researches can be due to entrance effects. The present results highlight the importance of accounting for common phenomena that are often negligible for standard flows such as accounting for profile of inlet velocity, axial heat conduction, effect of the design inlet and outlet manifolds.This paper, to the best of knowledge, is the first presentation on the method of the bulk fluid temperature measurements along micro-channel using IR technique, and calculation of the local heat transfer coefficient based on the local heat flux and the local temperature difference between the heated wall and the bulk fluid temperature. 相似文献
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The role of jet inlet geometry in impinging jet heat transfer,modeling and experiments 总被引:1,自引:0,他引:1
Effects of jet inlet geometry and aspect ratio on local and average heat transfer characteristics of totally nine confined impinging jets have been investigated experimentally using thermochromic liquid crystals and numerically by using a 3-D low Reynolds number k–? model. Experimental study by using liquid crystals for temperature measurement was conducted for three different jet exit geometries (circular, elliptic, rectangular). In addition, simulations were performed at the same mass flow rate for totally nine jet exit geometries including circular, elliptic and rectangular jets with different aspect ratios for dimensionless jet to plate distances 2, 6, and 12.As the aspect ratio of equal cross-sectional area elliptic and rectangular jets increases, heat transfer enhancement in the stagnation region was obtained. As a result higher aspect ratio jets can be used as a passive enhancement technique for localized heating or cooling especially at small jet to plate distances. Wall jet region comprises very large portion of the impinging plate under study and generally lower heat transfer rates were attained for higher aspect ratio jets in this region especially at small jet to plate distances. Therefore as the aspect ratio increases, lower average heat transfer rates were acquired. The effect of aspect ratio on local and average heat transfer decreases with increasing jet to plate distance. Even though the mass flow rate is the same, heat transfer rate of rectangular jets were reduced with increasing the cross-sectional area. With increasing jet to plate distance very similar heat transfer characteristics were observed along the major and minor axis directions. 相似文献
18.
Experimental analysis of flow and heat transfer in a miniature porous heat sink for high heat flux application 总被引:1,自引:0,他引:1
Z.M. Wan G.Q. Guo K.L. Su Z.K. Tu W. Liu 《International Journal of Heat and Mass Transfer》2012,55(15-16):4437-4441
A novel miniature porous heat sink system was presented for dissipating high heat fluxes of electronic device, and its operational principle and characteristics were analyzed. The flow and heat transfer of miniature porous heat sink was experimentally investigated at high heat fluxes. It was observed that the heat load of up to 280 W (heat flux of 140 W/cm2) was removed by the heat sink with the coolant pressure drop of about 34 kPa across the heat sink system and the heater junction temperature of 62.9 °C at the coolant flow rate of 6.2 cm3/s. Nu number of heat sink increased with the increase of Re number, and maximum value of 323 for Nu was achieved at highest Re of 518. The overall heat transfer coefficient of heat sink increased with the increase of coolant flow rate and heat load, and the maximal heat transfer coefficient was 36.8 kW(m2 °C)?1 in the experiment. The minimum value of 0.16 °C/W for the whole thermal resistance of heat sink was achieved at flow rate of 6.2 cm3/s, and increasing coolant flow rate and heat fluxes could lead to the decrease in thermal resistance. The micro heat sink has good performance for electronics cooling at high heat fluxes, and it can improve the reliability and lifetime of electronic device. 相似文献
19.
Krishnendu Bhattacharyya Swati Mukhopadhyay G.C. Layek Ioan Pop 《International Journal of Heat and Mass Transfer》2012,55(11-12):2945-2952
The effects of thermal radiation on the flow of micropolar fluid and heat transfer past a porous shrinking sheet is investigated. The self-similar ODEs are obtained using similarity transformations from the governing PDEs and are then solved numerically by very efficient shooting method. The analysis reveals that for the steady flow of micropolar fluid, the wall mass suction needs to be increased. Dual solutions of velocity and temperature are obtained for several values of the each parameter involved. For increasing values of the material parameter K, the velocity decreases for first solution, whereas, for second solution it increases. Due to increase of thermal radiation, the temperature and thermal boundary layer thickness reduce in both solutions and also the heat transfer from the sheet enhances with thermal radiation. 相似文献
20.
Numerical computation of fluid flow and heat transfer in microchannels 总被引:12,自引:0,他引:12
K. C. Toh X. Y. Chen J. C. Chai 《International Journal of Heat and Mass Transfer》2002,45(26):5133-5141
Three-dimensional fluid flow and heat transfer phenomena inside heated microchannels is investigated. The steady, laminar flow and heat transfer equations are solved using a finite-volume method. The numerical procedure is validated by comparing the predicted local thermal resistances with available experimental data. The friction factor is also predicted in this study. It was found that the heat input lowers the frictional losses, particularly at lower Reynolds numbers. At lower Reynolds numbers the temperature of the water increases, leading to a decrease in the viscosity and hence smaller frictional losses. 相似文献