Flow In Microchannel Heat Sink Research Articles

Numerical Analysis for Augmentation of Thermal Performance of Single-Phase Flow in Microchannel Heat Sink of Different Sizes with or without Micro-Inserts

With the development of miniaturized and enormous heat density generating novel technologies, the microchannel heat sink is rapidly establishing itself in modern cooling fields. Enhancement of heat transfer performance of microchannels is done by incorporating improved design structure, changing working fluids and flow conditions, using different materials for fabrication, etc. Coupling of two parameters influencing heat transfer performance of microchannels is in a nascent age, and complex coupling of heat transfer influencing parameters of microchannel sinks has not been clearly understood yet. This study provides the thermal-fluid flow features–fluid flow characteristics and heat transfer characteristics- of single-phase flow in microchannel of different sizes with or without microinserts by the use of computational fluid dynamics. The numerical simulation is performed by employing distilled water with thermophysical properties that depends on temperature for the Reynolds number range of 56–2242. The effect of microinserts on characteristics of fluid flow and heat transfer is analyzed. The results of numerical analysis show that heat transfer performance in microchannel with microinserts is enhanced effectively, however resistance in fluid flow is increased simultaneously. The 0.5 mm microchannel with microinserts shows the best performance of heat transfer characteristics with enhancement of 1–9% in the Reynolds number range of 56–2242 with simultaneous maximum increase in pressure drop by 14.5%. It’s overall performance, evaluated by thermal performance factor, is found to be best among all cases of three different channel sizes with and without microinserts. The maximum enhancement of heat transfer is found to be in case of 0.5 mm channel size with microinserts by a factor of 1.09. The maximum pressure drop is increased is found to be by factor of 2.28 in case of 2 mm channel size with microinserts.

Heat transfer characteristics of two-phase flow in a double-layer microchannel heat sink

Coolant two-phase flow in microchannel heat sinks can provide efficient and attractive solutions for disposing of high heat fluxes generated in electronic components and other similar engineering devices. Moreover, the coolant flow in double-layer microchannels has been proven as an also more effective way than a single layer. This paper introduces some useful results of an experimental study with coolant two-phase flow conditions in double-layer microchannels. The double layers microchannels were fabricated by end milling using a CNC machine. The effects of the applied heat flux up to 82 W/cm2, the mass flux in the range of 200 to 426 kg/m2.s, and the maximum microchannel depth of 550 μm, on the thermal behaviour and associated coolant pressure drop, were investigated. The study handles ‘in integrated approach’ the important topics of the boiling heat transfer characteristics and hydraulic performance. Among these topics, the flow boiling curve and average boiling heat transfer coefficients have received much attention in the present work. Numerical values of this coefficient were predicted using an accurate mathematical model combined with in-house solution code which was developed and reported in this paper. The coolant two-phase flow good square surface temperature uniformity for the double layer microchannels.

Multi-objective optimization and performance assessment of microchannel heat sinks with micro pin-fins

In this study, laminar, steady-state microchannel flow and conjugate heat transfer in a microchannel heat sink (MCHS) with micro pin-fins were investigated numerically. Computational Fluid Dynamics (CFD) simulations were performed with ANSYS Fluent for heat and fluid flow in MCHSs with circular-, square- and diamond-shaped micro pin-fins of the same hydraulic diameter. Arrangements of micro pin-fins in the MCHS were optimized for each shape using a multi-objective genetic algorithm (MOGA) method called Non-dominated Sorting Genetic Algorithm (NSGA-II). The fluid entered the microchannel at channel Reynolds numbers ranging from 100 to 350, corresponding to circular- and square-shaped pin-fin Reynolds numbers ranging from 20 to 110 and diamond-shaped pin-fin Reynolds numbers ranging from 20 to 190. In all simulations, uniform heat flux of 60 W/cm2 was applied from the bottom surface of substrate. As the cooling fluid, water with temperature-dependent variable viscosity was assigned in the fluid domain and copper with constant thermophysical properties was considered for the entire solid domain. Design variables were selected in order to represent both the pin-fin arrangement and flow-characteristics: porosity number and pin-fin Reynolds number, respectively. As objective functions, pressure drop ratio was defined as the hydrodynamic performance indicator and the Nusselt number was chosen to represent the thermal performance. To represent the trade-off between two objective functions, optimization was conducted after a systematic parametric study and pareto-fronts were obtained. Optimized solutions of each pin-fin shape showed that square-shaped pin-fin was unfavorable compared with the performance of other shapes of pin-fins. Among all configurations, diamond-shaped pin-fins significantly enhanced heat transfer at an increased pressure drop ratio. Depending on the pin-fin shape, optimal configurations emerged over a wide range of porosity values mostly at the upper limit of the pin-fin Reynolds number, with average Nusselt numbers varying between 3 and 12 and corresponding pressure drop ratios varying between 1 and 12.

2D computational investigation into transport phenomena of subcooled and saturated flow boiling in large length to diameter ratio micro-channel heat sinks

This study computationally investigates into the transport phenomena and heat transfer mechanisms associated with subcooled and saturated flow boiling of R-134a in large length to diameter micro-channel heat sinks. A two-dimensional computational model has been developed for analysis of the interfacial behavior of flow boiling that widely changes from bubbly to annular flow in micro-channel. OpenFOAM based 2D CFD solver was developed by using the volume of fluid method and Lee phase change model, enabling nucleate boiling occurs within the single-phase flow, to solve the transport equation for interface tracking. The conjugate heat transfer at the solid and liquid interface has been considered for the channel wall temperatures, which were compared with experimental results for assessing accuracy of developed CFD model. The high-speed images of flow boiling at multiple locations along the micro-channel were compared with flow patterns acquired from the computational simulation and showed an overall good agreement, which is verified by comparing with the void fractions estimated by the empirical correlations. The measured experimental data were also compared with the simulation results and showed good agreement for limited cases those without dry-out occurrence. The accuracy of two-dimensional CFD simulation in predicting the annular flow under asymmetric heating condition is compromised by excluding the flow along the sidewall which redistributes the flow in circumferential direction. The nonuniform film evaporation at the top and bottom side of the channel precipitates the pseudo dry-out leading to unexpected temperature rise and erroneous thermal responses. In spite of the successful simulation of coexisting subcooled and saturated flow boiling for limited cases without dry-out, this study unveils the causes and mechanisms that limit accurate 2D CFD simulation for widely varying two-phase flow in micro-channel heat sinks.

Numerical simulation study of thermal and hydraulic characteristics of laminar flow in microchannel heat sink with water droplet cavities and different rib columns

Microchannel heat sink is an effective technology to dissipate heat for high flux density devices. However, it is still unknown that what geometric structure form of channel will most effectively improve the overall performance of microchannel heat sinks. Three-dimensional numerical simulations were carried out to investigate the flow and heat transfer characteristics of microchannel heat sinks designed with an innovative combination of water droplet cavities and rib columns. Five different shaped rib columns were considered, including triangular, rectangular, diamond, elliptical and trapezoidal rib columns. A comparative analysis was presented to discuss the performance of these geometric configurations according to average Nusselt number (Nu), friction coefficient (f), entropy production (SΔ) and overall performance factor (η). It was found that the combination of water droplet cavities and rib columns can greatly improve the overall performance of microchannel heat sinks due to the full use of the advantage of rib columns to enhance heat transfer with the strengthened fluid flow disturbance and the advantage of cavities to reduce pressure drop with the enlarged flow area. The rib column shape and geometric parameters have significant effect on hydrothermal performance. Furthermore, the microchannel with water droplet cavities and elliptical rib columns has the best overall performance in all the cases and its overall performance factor achieves up to 1.513 with α = 0.3 and ξ = 0.5 at Re = 331.32.

Effect of circular pin-fins geometry and their arrangement on heat transfer performance for laminar flow in microchannel heat sink

A computational simulation of seventeen types of microchannel heat sink (MCHS) models with the channels equipped with circular pin fins having various diameters (0.25 and 0.5 mm), spacing (1.5, 3.0 and 6.0 mm) and height (0.1, 0.25, 0.4 and 0.5 mm) in order to compare their performance with the conventional MCHS was performed. Mesh independence validation and experiments on MCHS without any pin fins were used to assess the reliability of computer simulation results. The simulation was carried out for five different Reynolds numbers in the range from 100 to 1000. Hydraulic and thermal parameters including pressure drop, Nusselt number and thermal resistance were considered for performance evaluations. To evaluate comprehensive performance, the heat sink effectiveness factor which represents a combination of the hydraulic and thermal performance was defined and corresponding figures were provided to define an optimum geometry. It was observed that thermal resistance substantially depends on the height of the pins: the higher are the pins, the better is the heat flux. The optimal pin placement step sp was revealed as six diameters dp of the pin: sp = 6 dp for the height of the pins hp = 0.1–0.25 mm; for hp = 0.5 mm the effectiveness factor of MCHS has the maximum value at sp = 3 dp.

Numerical study of flow reversal during bubble growth and confinement of flow boiling in microchannels

The flow boiling instability caused by confined bubbles generated during the flow boiling process in parallel microchannels leads to flow reversal and earlier critical heat flux (CHF), which is a major problem with the extensive application of two-phase flow in microchannel heat sinks. In this study, single bubble growth in one of the two nearby microchannels is investigated through numerical methods. The VOF method, Hardt's phase-change model, conjugate heat transfer between solid and fluid domains were adopted within a self-developed OpenFOAM solver. After the growing bubble being confined by the sidewalls, the flow path of the channel is blocked thus the inlet liquid flow tends to flow into the other channels instead of pushing the confined bubble, which caused the confined bubble to extend towards upstream and flow reversal. By increasing the mass flux, the flow reversal is suppressed, but the flow boiling heat transfer enhancement is minimized due to the less evaporation area. The method of combination of microchannel and microgap (CMC) has little effect on flow reversal until the bubble enters the microgap. And its thermal performance is worse than the original heat sink. The confined bubble in the finned microchannel (FMC) heat sink would flow into the nearby channel through the secondary channel between the fins thus prevent flow reversal. Furthermore, the evaporation area between the bubble and solid walls increases, thus significantly lower thermal resistance (for about 40%) can be obtained. Considering the overall flow stability and heat transfer performance, the finned microchannel is recommended to be fabricated in industrial applications.

Numerical investigation on fluid flow and convective heat transfer in a microchannel heat sink with fan-shaped cavities and ribs

In the present study, a detailed numerical simulations of liquid flow in microchannel heat sink with four different geometry of ribs: rectangular (RR), backward triangular (BTR), forward triangular (FTR) and diamond (DR) arranged symmetrically inside reentrant fan shaped cavities (FC) on side walls has been conducted and compared with smooth channel (SC) to acquire fluid flow and heat transfer characteristics between Reynolds numbers of 136−588. The local pressure, temperature and heat transfer coefficients were determined to understand the convective heat transfer regimes and to analyze local flow behavior. The three-dimensional conjugate heat transfer model, investigation is done extensively to identify the influence of geometrical parameters towards augmenting thermal performance with parametric optimization. Evolved governing equations are solved by using SIMPLEC algorithm. Attempt has been made to improve heat extraction ability with reasonable pressure drop by replacing the existing simple design of microsink. It is observed that Nusselt number and friction factor are in good agreement with previous experimental data. Based on detailed parametric study, it was found that FC-RR is good in achieving maximum Nusselt number, but due to higher pressure drop penalty giving lower performance. Out of four proposed, FC-DR is conferring upstanding balance between heat transfer, pressure drop and giving the best thermal performance of 1.97 at Re = 391.47.

CFD analysis for heat transfer and fluid flow in microchannel heat sink with micro inserts

Space limitation and low cost heat removal process requirements leads to creation of professional equipment provided researchers goal of reduction in size of heat transfer equipment with improved thermal performance. Heat transfer may get intensified by decrement in thermal resistance or increasing turbulence such as by micro inserts. In the present study the computational investigation is performed to study the heat transfer and fluid flow in microchannel heat sink with outside micro inserts. In the present study the artificial roughness is provided using micro inserts. The simulation is performed using water as working fluid. The effects of inserts and fluid flow velocity on intensification of heat transfer were analyzed. In this study the effect on friction factor is also analyzed. The results of present study put light on the fact that heat transfer gets intensified due to addition of inserts and by increasing the fluid flow velocity.

Development of two-phase flow microchannel heat sink applied to solar-tracking high-concentration photovoltaic thermal hybrid system

To enhance the energy conversion efficiency of a concentration photovoltaic (CPV) system, a high-concentration photovoltaic thermal (HCPVT) hybrid system is proposed in this study. This system extends the functionality of the CPV from simply generating electricity to simultaneously providing electricity and heat. Thus, the utilization of the exhaust heat, which would otherwise be lost to the environment, could enhance the overall system efficiency and boost the economic value of the generated power output. However, in view of the significant influence of the operating temperature on the photovoltaic efficiency and longevity of the solar cells, an efficient cooling of the photovoltaic module during the solar-tracking process has become a great challenge to the development of HCPVT hybrid systems. In the present work, a radially expanding microchannel heat sink (REMHS) employing two-phase flow boiling is proposed to achieve the twin objectives of cooling the solar cells and generating steam from the recovered heat. The radially expanding microchannels are designed to facilitate a spontaneous vapor removal while alleviating flow maldistribution arising due to the changes in orientation of the device. By conducting flow boiling tests of deionized water, the heat transfer characteristics of the proposed REMHS under various orientation angles were investigated. The local heat transfer coefficient of the REMHS increased by 32%, as the orientation angle of the microchannels increased from 0° to 45°, and then remained steady with any further increase in the orientation angle. In addition, the heat transfer capability of the REMHS exhibited a strong dependence on the heat flux and was weakly correlated with the flow rate, which is typical of an evaporation liquid film heat transfer. Additionally, by conducting outdoor real-time sun tracking tests under a concentration ratio of 1070 suns, it was found that the proposed REMHS maintained a superior flow boiling performance under a high-concentration solar energy. The highest surface temperature on the cell surface remained below 110 °C and the observed maximum temperature difference was below 5 °C.

Performance evaluation of simple radial fin design for single phase liquid flow in microchannel heat sink

This paper numerically investigates heat transfer performance and characteristics in single-phase liquid cooling in microchannels with radial arrangement of fins having inherent symmetry to mitigate the problem of flow maldistribution. The effects of number of fins, channel depth and flow rate on Nusselt number and substrate temperature are obtained. The relative thermal performance and overall efficiency are compared with respect to two different base cases having minimum number of channels and minimum channel depth. For increasing values of flow rate and channel depth, contradicting effects in terms of temperature uniformity are obtained. By varying only number of channels, has no significance until it is coupled with channel depth, which suggests that aspect ratio of inlet cross-sectional area should be considered as a significant factor which is capable of generating secondary flows in single phase liquid flows. The overall efficiency of case with 70 number of channels, 200 µm depth and 15 ml/min is found to be highest.

Pressure Drop of Microchannel Plate Fin Heat Sinks.

The entrance region constitutes a considerable fraction of the channel length in miniaturized devices. Laminar slip flow in microchannel plate fin heat sinks under hydrodynamically developing conditions is investigated semi-analytically and numerically in this paper. The semi-analytical model for the pressure drop of microchannel plate fin heat sinks is obtained by solving the momentum equation with the first-order velocity slip boundary conditions at the channel walls. The simple pressure drop model utilizes fundamental solutions from fluid dynamics to predict its constitutive components. The accuracy of the model is examined using computational fluid dynamics (CFD) simulations and the experimental and numerical data available in the literature. The model can be applied to either apparent liquid slip over hydrophobic and superhydrophobic surfaces or gas slip flow in microchannel heat sinks. The developed model has an accuracy of 92 percent for slip flow in microchannel plate fin heat sinks. The developed model may be used to predict the pressure drop of slip flow in microchannel plate fin heat sinks for minimizing the effort and expense of experiments, especially in the design and optimization of microchannel plate fin heat sinks.

Enhanced model for annular flow in micro-channel heat sinks, including effects of droplet entrainment/deposition and core turbulence

This study investigates pressured drop and heat transfer characteristics for saturated flow boiling in a micro-channel heat sink specific to the annular flow regime. A theoretical control-volume-based model is presented, which relies on new relations for liquid droplet entrainment and deposition. While prior models have been attempted for annular flow, these models were based on simplified depictions of the vapor core based on average velocity. On the other hand, the present model provides detailed assessment of turbulence effects in the core, enabling the development of detailed cross-sectional profiles for momentum diffusivity, velocity, and shear stress. Predictive accuracy of the model is assessed against experimental data for R134a using a 609.6-mm long and 203.2-mm wide micro-channel heat sink containing 100 of 1 × 1-mm2 flow channels. The model shows good accuracy against 69 experimental pressure drop data points, with mean absolute error (MAE) of 16.22%, and 97.10% and 100.0% of the data predicted within 30% and 50%, respectively. It also shows very good accuracy against 388 data points for local two-phase heat transfer coefficient, evidenced by a MAE of 8.35%, and with 98.45% and 99.74% of the data predicted within 30% and 50%, respectively.

The influence of microchannel heat sink configurations on the performance of low concentrator photovoltaic systems

A new cooling technique for concentrator photovoltaic (CPV) systems is developed using various configurations of microchannel heat sinks. Five distinct configurations integrated with a CPV system are investigated, including a wide rectangular microchannel, a single layer parallel- and counter- flow microchannel, and a double layer parallel- and counter- flow microchannel. A comprehensive, three-dimensional thermo-fluid model for photovoltaic layers, integrated with a microchannel heat sink, is developed. The model is numerically simulated and validated using the available experimental and numerical data. Based on the results, the temperature contours on a plane located at the mid-thickness of the silicon layer are presented at different operating conditions and heat sink configurations. Accordingly, the maximum local temperature can be detected and temperature uniformity can be accurately estimated. Furthermore, at a concentration ratio of 20, the CPV system integrated with a single layer parallel- flow microchannel heat sink configuration (B) achieves the highest cell net power, electrical efficiency, and the minimum cell temperature. On the contrary, at the same operating conditions, the use of a single layer counter-flow microchannel heat sink configuration (C) is found to be the least effective cooling technique. The results of this study can guide industrial designers to adopt compact heat sink configurations and simple designs in the manufacturing process of hybrid CPV-thermal systems.

Thermal and Hydraulic Performances of Nanofluids Flow in Microchannel Heat Sink with Multiple Zigzag Flow Channels

This article presents an experimental investigation on the heat transfer performance and pressure drop characteristic of two types of nanofluids flowing through microchannel heat sink with multiple zigzag flow channel structures (MZMCHS). SiO 2 nanoparticles dispersed in DI water with concentrations of 0.3 and 0.6 vol.% were used as working fluid. MZMCHS made from copper material with dimension of 28 × 33 mm. Hydraulic diameter of MZMCHs is designed at 1 mm, 7 number of flow channels and heat transfer area is about 1,238 mm 2 . Effects of particle concentration and flow rate on the thermal and hydraulic performances are determined and then compare with the common base fluid. The results indicated that the heat transfer coefficient of nanofluids was higher than that of the water and increased with increasing particle concentration as well as Reynolds number. For pressure drop, the particle concentrations have no significant effect on the pressure drop across the test section.

Fluid flow and heat transfer of nanofluids in microchannel heat sink with V-type inlet/outlet arrangement

The fluid flow and heat transfer characteristics of laminar nanofluid flow in microchannel heat sink (MCHS) with V-Type inlet/outlet arrangement are numerically studied. A constant heat flux boundary condition is applied on the base plate of MCHS and all the other surfaces of MCHS are insulated. Four different kinds of nanofluids are utilized as working fluids which are SiO2, Al2O3, ZnO and CuO dispersed in pure water as a base fluid. Three different volume fractions of 1%, 1.5% and 2% and three distinctive nanoparticle diameters of 30nm, 40nm and 60nm were employed. The results specify that the SiO2 nanofluid has the uppermost heat transfer rate compared to other tested nanofluids. Increasing the nanoparticles volume fraction together with decreasing the nanoparticles diameter enhances the Nusselt number value. The pressure drop coefficient did not change significantly by using nanofluid with various volume fractions and varied nanoparticle diameters. Moreover, the results indicate that nanofluid can enhance the performance of MCHS with V-shaped inlet/outlet arrangement.

Experimental Analysis of Heat Transfer and Fluid Flow in Micro-Channel Heat Sink

In this paper heat transfer in single phase through micro-channels was studied. The validation of classical correlations of conventional channels to micro-channels is explored. It is found that classical approach is in good agreement with the experimental results of heat transfer in micro-channels .The material used for micro-channel heat sink (MCHS) is copper, experiments were conducted using water as cooling agent in this study. Micro-channels are made with the help of EDM machine on the upper surface of MCHS. Variation of heat transfer rates, effect of friction factor, effect of pressure drop and variation in temperature distribution is investigated in this study. It is observed in the study that with decrease in velocity flow friction also decreases.

Thermal design exploration of a swirl flow microchannel heat sink for high heat flux applications based on numerical simulations

Numerical simulations of velocity and temperature fields to explore the design of a single phase microchannel cooling system with spiraling radial inflow for high heat flux applications are presented. Total pressure drop and average wall heat flux are calculated for different flow rates and the effects of changing the microchannel height, flow inlet angle, and working fluid are investigated. Rotation of the fluid induces a crossflow and entrainment, this is found to enhance convective heat transfer considerably due to motion of fluid towards the heat exchange surface. The strength of this effect depends on the structure of hydrodynamic boundary layers, which is characterized by the Reynolds number and the flow inlet angle. The effect of reducing the Prandtl number is evaluated changing the working fluid from water to a 2vol% and a 4vol% water-Cu nanofluid suspension. For the cases studied, it is found that heat transfer enhancement by increasing the inlet swirl is greater than that of decreasing the Prandtl number using a nanofluid, though at a much higher pumping cost. In order to improve the performance of the device for high heat flux applications, admission of the flow should be as tangential as practically possible. It is found that, when reducing the microchannel height, boundary layers may merge and the entrainment effect is lost, therefore the total heat flux may not always increase with a decrease of the flow passage area, as opposed to conventional microchannels. The swirl flow microchannel heat sink showed promising cooling characteristics for applications such as thermal management of electronics or concentrated photovoltaics, with a ratio of pumping cost to heat rate of 0.02% for the base design studied.

Parametric study on thermal and hydraulic characteristics of laminar flow in microchannel heat sink with fan-shaped ribs on sidewalls – Part 1: Heat transfer

In this first part of a three-part study, a three-dimensional numerical model has been conducted to study the heat transfer characteristics of laminar flow in microchannel heat sinks with different geometric fan-shaped ribs on sidewalls for Reynolds number ranging from 187 to 715. The numerical model considers entrance effect, conjugate heat transfer, viscous heating and temperature-dependent thermo-physical properties. The water and silicon are used as fluid and solid for the computational domain. The computations base on the finite volume method and implement the SIMPLEC algorithm. The microchannel has the width of 0.1mm and depth of 0.2mm in the constant cross-section region. The geometric parameters include the width (0.05–0.4mm), height (0.005–0.025mm) and spacing (0.2–5mm) of aligned or offset fan-shaped ribs. The present study firstly examines the effect of fan-shaped ribs on velocity contour, temperature distribution and local heat transfer characteristics for laminar flow in such microchannel heat sinks. It is apparent that the fan-shaped ribs can effectively prevent the decline of local heat transfer coefficient along the flow direction. Secondly, the average Nusselt number and the total thermal resistance for such microchannel heat sinks have been studied. Results show that the height and spacing of fan-shaped ribs have significant influences on the heat transfer characteristics, while the width of ribs shows less. For the microchannel heat sinks with lower height and lager spacing of fan-shaped ribs, the aligned arrangement shows higher heat transfer coefficient than the offset one. For the studied Reynolds number range and geometric parameters of fan-shaped ribs, there are a 6–101% increase in average Nusselt number and a 3–40% decrease in total thermal resistance for the microchannel heat sink with aligned fan-shaped ribs, while a 4–103% increase in average Nusselt number and a 2–42% decrease in total thermal resistance for the microchannel heat sink with offset fan-shaped ribs, comparing with the smooth one. New heat transfer correlations for such microchannel heat sinks are developed, which fit the present data with a mean absolute error of 2.5% for the ones with aligned fan-shaped ribs and 3.8% for the ones with offset fan-shaped ribs.

Parametric study on thermal and hydraulic characteristics of laminar flow in microchannel heat sink with fan-shaped ribs on sidewalls – Part 2: Pressure drop

This second part of a three-part study concerns pressure drop of laminar flow in microchannel heat sinks with water and silicon used as fluid and solid for the computational domain. In the rectangular microchannel with width of 0.1mm and depth of 0.2mm, the repeating aligned or offset fan-shaped ribs are mounted to the channel sidewalls. To examine the influence of fan-shaped rib’s geometry on thermal and hydraulic characteristics of laminar flow, three non-dimensional variables, representing the width (0.05–0.4mm), height (0.005–0.025mm) and spacing (0.2–5mm) of fan-shaped ribs are designed. The present study firstly presents the pressure distributions in microchannels to analyze the local hydraulic characteristics, and then examines the local pressure and friction factor along the flow direction for different geometry of fan-shaped ribs. Results show that the fan-shaped ribs can lead to large increase of local pressure in comparison with the smooth microchannel, especially for the aligned fan-shaped ribs. Further, the effect of fan-shaped ribs’ geometry on the average friction factor has been investigated. Results show that with the increase of fan-shaped ribs’ width, the friction factor ratio of the studied microchannels to the smooth one firstly decreases and then increases. The increase of fan-shaped ribs’ height and decrease of ribs’ spacing can lead to the extreme increase of average friction factor, especially for the microchannels with aligned fan-shaped ribs. For Reynolds number ranging from 187 to 715, the microchannels with aligned fan-shaped ribs show the average friction factor 1.1–8.28 times larger than the smooth one, while those with offset fan-shaped ribs show 1.22–6.27 times higher. New pressure drop correlations for such microchannel heat sinks are developed, which fit the present data with a mean absolute error of 13.2% for the ones with aligned fan-shaped ribs and 13.5% for the ones with offset fan-shaped ribs.