Enhanced Heat Transfer Characteristics Research Articles

Numerical investigation on the enhanced heat transfer characteristics of non-Newtonian viscoelastic fluids in microchannel with chip arrays

Elastic turbulence is an efficient heat transfer method at microscale. In this work, we conduct a systematic investigation on the flow and heat transfer performances of viscoelastic polymer solutions in microchannels with chip arrays by means of high-fidelity numerical simulations. Focusing on the effects of fluid elasticity [i.e. polymer relaxation time (λ)] and flow Reynolds number (Re), we find that the synergistic interplay between inertial and elastic forces is strategically exploited to amplify convection, thereby facilitating an enhanced heat transfer performance. For highly elastic fluid, the Nusselt number (Nu) can be improved by 76.13 % compared to that of less elastic fluid, while the pressure drop is reduced appropriately. In addition, as the fluid elasticity increases, the pressure drop decreases and eventually converges to a constant. In the zone of elastic turbulence, the fluid reinforces the convective heat transfer, which can be ascribe to the deformation of long-chain polymer molecules. Particularly, we consider the effect of temperature-dependent λ on the heat transfer performance. Our results demonstrate that the increased temperature-dependent λ decreases the value of Nu, and the variation between values of variable and constant λ is reduced with increasing Re or λ. Hence, in some cases of large fluid elasticity or high Re, it is possible to safely ignore the impact of temperature-dependent λ with an acceptable accuracy. The present work provides important insights into the enhanced heat transfer via elastic turbulence, which could guide the applications in the field of chip cooling.

Heat transfer enhancement characteristics of sinusoidal corrugated tubes fabricated via laser powder bed fusion

Laser powder bed fusion (LPBF) has emerged as a powerful tool to develop heat transfer devices with higher efficiency. Corrugated tubes are commonly used components to achieve enhanced heat transfer in these devices. However, there still lacks a comprehensive study on the thermal-hydraulic performance of LPBF-fabricated corrugated tubes. In this work, we investigated the heat transfer enhancement characteristics of sinusoidal corrugated tubes (SCTs) fabricated via LPBF. SCTs with different amplitude-to-diameter ratios (A/D ratio) and wavelength-to-diameter ratios (S/D ratio) were designed and fabricated. The geometrical morphologies and surface roughness of LPBF-fabricated SCTs were characterized. Numerical simulations were performed to investigate the effects of A/D ratio and S/D ratio on the flow patterns and flow dynamics. A test system was developed to measure the pressure loss and thermal performance. Performance Evaluation Criterion were calculated to characterize the heat transfer enhancement. A/D ratio was found to have more significant impacts on the friction factor and Nusselt numbers than S/D ratio. Correlation models were developed to predict friction factors and Nusselt numbers based on the least square method. Mean prediction errors of ±3.3 % and ±5.3 % and maximum prediction errors of ±11.6 % and ±18.1 % were achieved for Nusselt numbers and friction factor, respectively.

Enhanced heat transfer characteristics using dimples in the receiving end of laser wireless power transmission system

Laser wireless power transmission is a method of transmitting energy using laser as the carrier and photovoltaic cell as the receiving end. The study of cooling of its receiving end is significant, which can improve the efficiency and extend the service life of the system. In this article, dimples and protrusions with different heights are designed as heat dissipation components, which is the first application to laser wireless power transmission. And numerical simulations are conducted using the standard k-ω model to analyze and compare the heat transfer characteristics and electrical characteristics of photovoltaic cooling system under different geometric parameters. The results show that, under the same flow rate, the backside temperature of the cells with dimples and protrusions packs is 1 ∼ 3 K lower and the average Nusselt number increases by 30 %∼54 % compared to that of the smooth flat plate. At the same geometric parameters of the heat sinks and the Reynolds numbers of 7207, 14413, and 28106, the power peaks are increased by 15.3, 16.7and 17.7 times compared to that of the cells without the heat sinks.

Modeling of magneto bioconvection Williamson nanoliquid through modified heat flux: The significance of entropy

The combination of microbes and nanofluids has noteworthy consequences for technological and engineering progress, particularly in the realm of heat transfer applications. This study explains radiative flow with chemical reactions affect the emergence of microorganisms in magnetic mixed convective Williamson nanofluid flow. The Cattaneo-Christov heat flux theory and the effects of heat source/sink have been examined about the energy equation. The prime idea of this analysis is to enhance heat and mass transport. The modelled equations have been converted to dimensionless by considering suitable alteration. The dimensionless expression is then numerically tackled using MATLAB's bvp4c approach. The graphs for different profiles—that is, momentum, temperature, concentration and concentration of microorganisms that move—are made visible for particular nondimensional factors. Furthermore, entropy generation minimization has been obtained through law of thermodynamics. The drag friction, heat and mass transfer rate, and microbe density are also computed in a tabular manner. The most important findings that are pertinent to this study are that an increase in the values of the Brownian motion, thermal radiation and thermophoresis significantly enhance heat transfer characteristics. A consistent pattern can be observed when comparing the current results with earlier research.

Heat Transfer and Fluid Flow Characteristics in a Micro Heat Exchanger Employing Warm Nanofluids for Cooling of Electronic Components

The heat transfer enhancement and hydrodynamic characteristics of nanofluid use in a micro heat exchanger is investigated for cooling electronic components working in hot climatic conditions. The cooling fluid employed was water and TiO2 nanoparticles at mass concentrations of 1% and 5%, the Reynolds numbers ranged from 400 to 2000, and the inlet temperatures ranged between 35 °C and 65 °C. At a nanofluid inlet temperature of 55 °C and a nanoparticle concentration of 1%, the Nusselt number increased by 23% up to 54% as the Reynolds number varied between 400 and 2000. At a nanoparticle concentration of 5%, the percentages that correspondingly enhanced the Nusselt number were 32% and 63%. The temperature of the electronic heating component decreased by 4.6–5.2 °C when the nanofluid concentration was increased from 0 to 5% at a Reynolds number of 400 and a nanofluid inlet temperature of 35 °C. Small increments in the pressure drop of about 6% and 13% were observed at nanofluid concentrations of 1% and 5%, respectively. With nanoparticle concentrations of 1% and 5%, a Reynolds number of 2000, and a nanofluid inlet temperature of 35 °C, performance evaluation criterion (PEC) values of 1.36 and 1.45 were obtained. When the nanofluid inlet temperature increased to 65 °C, the PEC parameter decreased to 1.02–1.10 for both concentrations.

Investigation of heat exchanger tube fitted with triangular perforated nail head twisted‐tape inserts

AbstractA numerical investigation of the Nusselt number, heat transfer augmentation efficiency, and friction factor in a laminar flow tube with triangular perforated nail head twisted tape (TPNHTT) is reported using ANSYS 19.2 Fluent. The effects of triangular cut (each side 3 mm) in the middle pitch of the tape along the height, diameter, and top diameter of the nail head (10, 2, and 2.5 mm, respectively) have been explored for (300 ≤ Re ≤ 1800) in a tube of 22 mm diameter. In this paper, implementation has been done with a TPNHTT varying width (14 ≤ b ≤ 20) twist ratio (TR) ranging from (3 ≤ TR ≤ 6), inserts in a tube for laminar flow. Twisted tape (TT) produces a swirl flow associated with fluid resulting in heat transfer enhancement and pressure drop characteristics other than that for the plain tube (PT). The performance of the Nusselt number and friction factor increased up to 123.62% and 495.30%, respectively, on the application of TPNHTT as compared with PT. A maximum thermal performance efficiency of 2.98 has been achieved using the twisted‐tape ratio of the current tube in laminar flow at a Reynolds number of 1700. In addition, correlation equations (11) and (12) have been developed for the friction factor and Nusselt number valid for 300 ≤ Re ≤ 1800, 14 ≤ b ≤ 20, and 3 ≤ TR ≤ 6. The study has proved that applying TT is an upgraded approach for laminar convection heat transfer. This novel work finding will be supportive for researchers to design the latest heat exchangers.

Structural optimization of thermal management system for bionic liquid cold battery based on fuzzy grey correlation analysis

An energy-efficient battery thermal management system with efficient enhanced heat transfer characteristics, low power consumption and backflow inhibition performance is of great importance for electric vehicle power batteries. Based on the design of the Tesla valve and inspired by bionics, a new type of bionic blade-like mini-channel liquid cold plate with high efficiency, low power consumption and certain anti-reverse flow performance was proposed. Firstly, the initial liquid-cooled plate thermal simulation model at 5C discharge was established by CFD method and its reliability was verified by experiment. Then, orthogonal tests and fuzzy correlation analysis (FGRA) were used as evaluation methods to analyze the effects of four structural parameters (inner angle α, circumcenter angle θ1, circumcenter angle θ2, and channel height d) on the average temperature, heat transfer coefficient, and friction coefficient. The results show that the variation of the channel height d had the highest degree of influence on the mean temperature (Tave) and friction coefficient f, and that the internal angle α had the highest correlation with the heat transfer coefficient h. Finally, based on the optimization results, a better model within the range of values of each factor was obtained. When α = 25°, θ1 = 90°,θ2 = 75°, and d = 1.2 mm, Nu was increased by 0.932 (95.08 %), and ΔP was decreased by 501.686 Pa (84.74 %).The results of the optimization were shown in the following table.

Experimental and numerical analysis of PV-PCM integrated with novel shaped corrugated fins

In this paper, performance of a PV-PCM system with novel internal corrugated fins is analysed by dynamic simulation and experiments for the inclinations of 0°, 15°, and 30° against a flux of 750 W/m2 using a solar simulator. The impact of fins (n) is investigated numerically, and the optimal number of fins is found. Performance parameters such as temperature, power output, and efficiency are compared for PV, PV-PCM, and finned PV-PCM systems. The validity of the numerical model is established by comparing the simulated and experimental PV temperatures, which reduces cost and time and allows the numerical models to optimise the design and performance of the system. Results showed that an increase in inclination leads to improved performance of the PV due to an increased convection heat transfer rate. The effect of the fins is pronounced at lower inclinations. Corrugated fins enhance the heat transfer rate compared to traditional flat fins, and the heat transfer enhancement characteristics of corrugated fins within the finned PV-PCM system can provide valuable insights for optimised performance. Compared to the PV-only system, the maximum PV temperature reductions for PV-PCM and finned PV-PCM systems are 30.1 °C and 38.6 °C for θ=0° and 25.23 °C and 34.1 °C for θ=30°. The optimal number of fins is 4 for all inclinations. The maximum efficiency enhancement for optimal systems decreased from 28.15 % at θ = 0° to 22.27 % at θ = 30°. Finally, the experimental performance of finned PV-PCM at a latitude corresponding to Calicut, India, is also conducted.

A numerical study of a novel centrally bifurcated mini-channel liquid cooling plate for enhanced heat transfer characteristics

Temperature rise and poor temperature consistency of lithium-ion batteries due to heat accumulation affect the safe application of batteries. Mini-channel structured liquid cooling plates (LCP) with excellent battery thermal management effects is investigated. In order to obtain a better temperature management effect and temperature consistency at lower pressure drops, a double-layer mini-channel structure LCP bifurcated from the center to the periphery is innovatively designed. Using the simulation software, the impact of the novel LCP's structural elements on battery thermal management efficiency is studied. According to research, the LCP with a double-inlet and double-outlet arrangement provides the best temperature control while requiring the lowest pressure drop. With a 25.7 Pa pressure drop, the LCP can decrease the maximum temperature and maximum temperature difference of the battery to 38.83 °C and 6.57 °C during discharging at 2C. Subsequently, the effects of main channel width, branch channel structural elements and inlet mass flow rate on the performance of the LCP are investigated. Compared to the structural elements, the inlet mass flow rate has more influence on the effectiveness of battery thermal management. However, when the inlet mass flow rate is increased to more than 0.8 g ·s−1, the influence gets less significant. Compared to the other four structural LCPs, the batteries maximum temperature and maximum temperature differences while discharging at 2C are the lowest at 0.8 g ·s−1 inlet mass flow rate with just 152 Pa pressure drop, 33.64 °C and 6.89 °C, respectively. All of these findings could be help to optimize the structure design of mini-channel liquid cooling plates used to battery thermal management.

Experimental Investigation of Local Nusselt Profile Dissemination to Augment Heat Transfer under Air Jet Infringements for Industrial Applications

An experimental study is presented in this paper to evaluate the enhancement of heat transfer characteristics. This includes the study of a steady air jet impinging on a planar aluminum plate with constant heat flux. Extensive industrial applications of heat transfer include electronic heat sinks, the food industry, automobiles, and heat exchangers. The magnitude of the local Nusselt number along the streamwise direction is determined through detailed experimental computation using the infrared radiometry technique. The range of Reynolds number was selected between 6500 ≤ Re ≤ 15000 and the air jet outlet-to-target surface spacing 2 ≤ Y/D ≤ 6. The objective is to develop a semi-empirical correlation that can be used to determine the distribution of local Nusselt numbers over a flat plate. Considering the objective function of the spacing between the air jet outlet and target surface spacing (Y/D), Reynolds number (Re), and non-dimensional number from stagnation point in the radial direction of the plate (r’/D), it was observed that the heat transfer rates are higher for the configuration Y/D = 4 for varying Reynolds numbers, a 5 percent increase was observed. The stagnation Nusselt number shows an increasing trend up to Y/D = 4, for Reynolds numbers 10,000 and 12,000 respectively, the corresponding stagnation Nusselt numbers are 110 and 115. In comparison to the stagnation Nusselt number, which is the same Reynolds number corresponds to, the transition field Nusselt number had heat transfer values that were 12% lower.

Experimental study for the enhancement of heat transfer characteristics and development of thermal correlations of a roughened solar collector

AbstractThe thermal performance of the flat plate solar collector is very low. The most beneficial and worthwhile method for increasing the thermal performance of a solar‐powered air heater (SPAH) is to include a roughness element in the working zone of heat transfer that is located beneath the shear layer of the absorber surface. In this research work, efforts are made to enhance thermal performance and develop thermal correlations for the estimation of the Nusselt number and friction factor of a roughened SPAH. Experiments are performed for various ranges of flow, Reynolds numbers, and roughness parameters. The experimental technique of liquid crystal thermography is utilized to assess the dispersal of Nusselt number over the roughened surface for all roughness parameters. A maximum thermal performance enhancement index of 2.69 is obtained with the optimum value of the roughness parameter at a relative roughness pitch (RRP) of 9, a relative staggering distance (RSD) of 4, and a relative roughness length (RRL) of 6.15. Second, a mathematical correlation is developed using a regression model to estimate the Nusselt number and friction factor in terms of nondimensional roughness and flow parameters operated as RRP, RSD, RRL, and Re. The degree of discrepancy between the established the relationships and the findings from the experiment reveals incredibly satisfying results. Hence employing twisted V‐ribs as an artificial roughness element no doubt increases the Nusselt number, and thermohydraulic performance enhancement index, but it also exerts less frictional power across the SPAH duct.

Thermal management of an asymmetrical wavy microchannel heat sink via Ag/water nanofluid

The ever-increasing demand for electronic systems to enhance their performance and processing speed has exponentially increased their heat generation, especially those containing microstructures with reduced surface area. Tackling these complex thermal management challenges creates an urgent need to design and model compact efficient cooling systems. In this investigation, a unique design of a microchannel heat sink with sinusoidal and absolute sinusoidal wavy walls with/without nanofluid is proposed. Heat transfer enhancement and fluid flow characteristics are numerically investigated by developing a two-dimensional finite element model for Reynolds numbers 5, 100, and 500. The periodicity of the wavy section and the different volume fractions of silver nanoparticles ranging from 0 to 4% in water are further considered. The entropy generation is analyzed using the Bejan number. The findings revealed that while the entropy generation rises in the absolute sinusoidal channel, it has a better heat transfer performance by 10.3%, 15.8%, and 16.6% than a straight microchannel for the ascending Reynolds numbers. Interestingly, the channel's heat transfer and thermal efficiency decrease when an unnecessary number of sinusoidal periods are used. The thermal efficiency improves by 3.35% compared to the straight microchannel by employing only one absolute sinusoidal wavelength along the channel.

Analytical analysis of inclined three-layered composite channel with cobalt ferrite nanoparticles and Hall current in Darcy medium

The present study explores the influence of electromagnetic effects on the flow of a nanofluid in a saturated permeable medium, confined between a clear viscous fluid in an inclined channel. The nanofluid consists of cobalt ferrite nanoparticles dispersed in ethylene glycol. The governing equations are derived considering Darcy's law for the permeable medium and Tiwari's model for fluids containing nano-sized particles. Additionally, radiation and dissipation effects are incorporated into the energy equation. The equations are transformed into dimensionless form and solved analytically using the perturbation technique. The results are analyzed through graphs and tables for different material parameters. The findings reveal that higher electric and magnetic strengths have a significant impact on the fluid velocity at the interface of the two fluids, resulting in reduced shear both at the clear fluid surface and the interface between them. This highlights the crucial role played by electric and magnetic strengths in modifying flow phenomena. Consequently, combining electric and magnetic strengths with nanofluids can be utilized to achieve desired qualities in multi-fluid flow and enhance heat transfer characteristics.

Study on the heat transfer enhancement characteristics by flow-induced vibration of inserting polyethylene membrane inside the channel

With the development of science and technology, the heat dissipation problem of high-density electronic products has gradually emerged in engineering practice. In this paper, the enhanced heat dissipation process of fluid induced oscillation through flexible membrane is proposed, which belongs to the multi-field synergistic bidirectional coupling effect of thermal-fluid-solid coupling. Through the comparative numerical analysis of the flow induced oscillation of the flexible membrane and the fixed rigid fin in the flow channel, the mechanism of the fluid induced oscillation of the flexible polyethylene membrane is revealed. Based on the two-way fluid-solid coupling method, a numerical model for the heat transfer process of polyethylene membrane with thickness of 0.02 mm in the fluid channel was established. The temperature field, Nu (Nusselt number) and PEC (Performance comparison index) number of the rigid fin and polyethylene membrane installed in the channel under different Reynolds numbers were calculated respectively. The ratio of the length of the membrane to the height of the channel was adjusted for multiple groups of calculations to verify the positive effect of the polyethylene membrane installed in the channel on the heat exchange effect. The results show that in the fully developed area of heat transfer, the channel with polyethylene membrane is better than that with rigid fins in terms of turbulence and vortex shedding; at Re = 4400, the comprehensive enhanced heat transfer factor of heat exchange is the largest, up to 1.27; as the ratio of the height of the new flexible membrane to the height of the channel is 1, the heat transfer enhancement effect is best. In the next step, the correlation theory between oscillation characterization parameters and heat transfer enhancement effect under pulsating fluid excitation will be investigated.

Study of the enhanced heat transfer characteristics of wavy-walled tube heat exchangers under pulsating flow fields

Heat exchangers have a very wide range of applications in many industrial fields, so the rational design and the performance are to improve the heat exchanger energy efficiency and reduce the production cost of an important means. In this paper, the heat transfer mechanism of pulsation is revealed by simulating and analyzing the effects of three pulsation parameters: volumetric flow rate, pulsation frequency, and pulsation amplitude on the flow and heat transfer of a wavy-walled tube heat exchanger, with the study focusing on the instability behavior that affects the heat transfer mechanism. The results reveal that the combined heat transfer performance of the wavy-walled tube heat exchanger is about 8.2% higher than that of the straight-walled tube heat exchanger. The flow field of the heat exchanger is more fully developed under the pulsating flow field, and its performance evaluation coefficients (PECs) are all greater than 1. It is also found that with the increase in the volume flow rate Qv, the heat transfer enhancement coefficient and PEC first increase and then decrease, and reach the maximum value near Qv = 2.0 m3/h; with the increase in the amplitude A, the vortex and heat transfer enhancement coefficient inside the heat exchanger increase, but the integrated heat transfer performance of the heat exchanger is gradually weakened; with the increase in the frequency fT, the heat transfer enhancement coefficient and PEC first increase gradually, but the increase gradually decreases and levels off in the later stages, reaching a maximum value near fT = 0.5 Hz. Meanwhile, the field coefficients of the wavy-walled tube heat exchanger were analyzed and found to be much smaller than 1, with an order of magnitude of 10−4, and the results also showed that the field coefficients were inversely proportional to the volume flow rate and directly proportional to the amplitude of pulsation and that the field coefficients showed a tendency of increasing and then decreasing with the change of pulsation frequency and reached a maximum value near fT = 0.5 Hz. This work provides an important reference for current manufacturing industries to optimize heat exchanger sizing and develop efficient thermal management systems.

Thermal analysis of magnetohydrodynamics (MHD) Casson fluid with suspended iron (II, III) oxide-aluminum oxide-titanium dioxide ternary-hybrid nanostructures

This study is carried out to enhance and analyze the thermal performance of non-Newtonian Casson fluid by immersing Ternary hybrid nanoparticles Fe3O4-Al2O3-TiO2 uniformly. To model the behaviour of such complex phenomena mathematically, a system of complex transport differential equations is developed by utilizing a non-Fourier heat transfer model for energy transport. The non-dimensional system of transport equations involving physical parameters is analyzed numerically by employing the Galerkin finite element methodology (G-FEM). The simulations predicted promising enhanced heat transfer characteristics in Ternary hybrid Casson fluid. The Casson fluid parameter has shown remarkable behavior on temperature distribution. Ternary hybrid nanoparticles have increased the overall thermal conductivity of the fluid and consequently, the temperature distribution is significantly raised. Hence ternary hybridity of nano-structures in Casson fluid is shown as an effective technique in improving the thermal performance of complex fluid.

Analytical analyzing mixed convection flow of nanofluid in a vertical channel using python approach

This study uses analytical methods to investigate the impact of parameters on the mixed convection flow of nanofluid in a vertical channel. The research aims to explore the heat transfer characteristics of nanofluids for more efficient heat transfer in devices. The study analyzes the influence of the Reynolds, Grashof, and Prandtl numbers on nanofluid flows. It also examines the effects of temperature and nanoparticle concentration distributions on parameters such as Brownian motion (Nb), thermophoresis (Nt), and Lewis number (Le). The presence of nanoparticles significantly enhances the heat transfer characteristics in the flow problem. Reynolds number, Grashof number, and Prandtl number significantly impact flow behavior. Velocity, temperature, and nanoparticle volume fraction profile trends are thoroughly investigated and found to vary. Akbari-Ganji's method (AGM) and the homotopy perturbation method (HPM) demonstrate the potential of computational tools in analyzing nanotechnology fluid dynamics. The accuracy and reliability of the proposed analytical techniques are confirmed through comparisons with a numerical method. The novelty of this research lies in its comprehensive analysis of parameter effects on the mixed convection flow of nanofluid, the enhanced heat transfer characteristics in the presence of nanoparticles, and the unique contributions offered by the utilization of Python programming in this field. The outcomes of this study provide insights for designing and optimizing heat transfer systems using nanofluids, contributing to advancements in nanotechnology.

Enhancement in heat transfer characteristics by using truncated conical turbulators in a double pipe heat exchanger under turbulent conditions

Enhancement in heat transfer characteristics by using truncated conical turbulators in a double pipe heat exchanger under turbulent conditions

Efficiency Enhancement of Heat Transfer Fluids by Using Carbon Dots Nanoparticles Derived From Aloe Vera

Modern technological progress in transportation, medical, electronics and HVAC systems has resulted in an extreme need for a performance-enhanced heat transfer system. Heat transfer employing a flowing fluid is most used, and the thermal properties of liquids play a decisive role in heating and cooling applications in industrial processes. The thermal conductivity of a liquid is an important physical property that decides its heat transfer performance. Conventional heat transfer fluids have inherently poor thermal conductivity, making them inadequate for ultra-high heat transfer applications. Nanofluids are a new class of liquids whose properties are controllable by adding nanoparticles. A great deal of attention has been drawn to their enhanced heat transfer characteristics relative to that of pure fluid. This paper synthesizes three various Nano Fluids and experimentally compares their heat transfer capabilities using a shell and tube heat exchanger setup. An attempt is made to suggest applications for enhanced heat transfer. Al2O3 Nanofluid is compared with Nanofluid containing carbon dots derived from Aloe vera, and it has been found that carbon. Aloe vera yields more heat transfer

Heat transfer enhancement and flow characteristics of internal cooling channels with slit vortex generators

Vortex generators can boost heat transfer performance greatly, although they are always linked with significant pressure drops. In this article, to reduce the pressure drop while improving the thermal efficiency simultaneously, traditional delta winglet pair vortex generators (DWPVG) with slits are installed in the rectangular channel. Besides, the effects of slits on DWPVG on pressure drops and heat transfer performances for different Reynolds numbers are studied. To reveal the fluid flow characteristics, three-dimensional calculations using a confirmed turbulence model are undertaken and the underlying thermo-fluid processes are exposed for the various investigated cases. To reveal the overall thermal performance of different cases, two overall thermal performance factors Nu ave/Nu 0/(f/f 0) and Nu ave/Nu 0/(f/f 0)1/3 are used. The findings suggest that when the fluid flows through slits, induced vortices are located closer to the bottom surface, generating an improvement of the local Nusselt number behind DWPVG. Furthermore, DWPVG with slits can decrease the pressure drop, but also make the local thermal efficiency improve in the channel with a high blocking ratio. Moreover, the increase in the overall thermal performance of the slit DWPVG channel with a high blocking ratio is enlarged with the Reynolds number raise. Besides, the highest heat transfer enhancement is provided by opening slits on five DWPVGs in the rectangular channel.