Minichannel Heat Sink Research Articles

Thermal performance of double serpentine minichannel heat sinks: Effects of inlet-outlet arrangements and through-holes

To decrease the substrate temperature gradient of a traditional single serpentine mini-channel heat sink, we present a novel double serpentine heat sink and perform experimental and numerical tests by employee ANSYS FLUENT (version 15) code to trade off the flow and thermal performance of the heat sink. The effects of three inlet-outlet arrangements, the through-hole numbers and the diameter of through-hole on the cooling capacity are compared and analyzed. It can be found that the introduction of interleaved inlet-outlet outperform provides much better uniform substrate temperature, meanwhile, the pressure drop can be reduced by up to 43%, and the average Nusselt number can be raised by up to 26% through punching holes on the channel wall at Qv = 0.159 L/min. It is also suggested that the double serpentine heat sink using more holes exhibits much better thermal performance attributed to the distinct alleviation of the maximum substrate temperature.

Numerical study on convective heat transfer of nanofluid in a minichannel heat sink with micro-encapsulated PCM-cooled ceiling

In this work, the convective heat transfer of Al2O3-water nanofluid in a three-dimensional minichannel heat sink is exaimed numerically. The finite volume method (FOV) is applied to discrete the governing equations, and the LINE SOR and TDMA algorithms are used for solving the equations. The FORTRAN program has been developed for the numerical calculation. Ceiling of the minichannel is covered with the micro-encapsulated phase change material. The N-eicosane with the melting temperature of 34.7 °C and the latent heat of 24,300 J/kg is considered as the phase change material. The purpose of placing this material on the ceiling of the minichannel is to cool the working fluid by absorbing the heat from the fluid during melting. All simulations are performed for three values of solid volume fractions of nanoparticles including 0%, 2%, and 10%, two outer surface temperatures of ceiling including 28 °C and 30 °C, and the Reynolds number in the range of 500–2000. The effects of different parameters including the usage of the phase change material, the solid volume fractions of nanoparticles, the outer surface temperature of ceiling, and the Reynolds number on the thermal field, heat flux, melting rate of micro-encapsulated phase change material, and thermal resistance in the mini-channel heat sink are studied. The results reveal that the thermal resistance decreases about 10.88% by using the nanoparticles with solid volume fraction of 10% at Rebf = 500 and Tcw,0 = 28 °C for the case of bare celling. The heat flux received by the ceiling in heating section decreases by using the micro-encapsulated phase change material(MEPCM). In addition, the MEPCM melts faster at lower values of the Reynolds number.

Experimental and numerical study on the performance of a minichannel heat sink with different header geometries using nanofluids

Inefficient distributor and collector header design in a minichannel heat sink causes flow maldistribution which can severely degrade the thermal and hydraulic performance of the heat sink. This paper presents an experimental and numerical investigation on the thermohydraulic performance of minichannel heat sinks with two different header geometries using nanofluids. A series of tests are conducted on a minichannel heat sink with optimized and conventional header geometries by using (Al2O3-H2O) nanofluids and distilled water as coolants. The effects of header geometry, nanoparticle concentration, and coolant flow rate on the overall heat transfer coefficient, heat transfer enhancement, thermal resistance, and base temperature are investigated. The experimental and numerical results exhibited good agreement, indicating that the thermohydraulic performance of the heat sink with the optimized header geometry is superior to that with the conventional header geometry. The minichannel heat sink with the optimized header geometry exhibited 17% higher overall heat transfer coefficient and 43% reduction in pressure drop while achieving lower values for base temperature and thermal resistance for each employed flow rate and volumetric concentration of nanoparticles. Furthermore, the performance evaluation criteria (PEC) indicated a 41% improvement in hydraulic performance while using minichannel heat sink with optimized header geometry compared to that with the conventional header geometry.

Flow and thermal analysis of hybrid mini-channel and slot jet array heat sink

In this paper, experimental tests and numerical studies were performed for better understanding the flow and heat transfer characteristics of the hybrid mini-channel and slot jet array heat sink. The average heat transfer coefficients were experimentally obtained and compared with independent mini-channel heat sink and slot jet array heat sink with a dimension of 10 mm × 10 mm at a flow rate from 0.1 L/min to 1.2 L/min, heat flux of 35.74 W/cm2 and 62.22 W/cm2. The results showed that the hybrid scheme has a better heat transfer performance than other two heat sinks at the same flow rate. Numerical simulations were conducted to further analyze thermal-hydraulic performance of the hybrid heat sink at an inlet Reynolds from 230 to 2760. Compared with k-ε models, numerical results with transition SST flow model match better with the experimental results. According to the numerical results, we found vortexes in the channel of the hybrid heat sink and these vortexes are beneficial to the heat transfer. The influence of geometries on the overall thermal resistance and total pressure drop were discussed using numerical simulations. The results demonstrated that the base thickness, channel height, side wall to channel width ratio and channel number of the hybrid heat sink all have significant effect on the cooling performance and thermal resistance and pressure drop can be reduced obviously via geometry optimization.

Numerical Investigations of Mini-Channel Heat Sink for Microprocessor Cooling: Effect of Slab Thickness

High heat generation in microelectronics devices is an inevitable consequence of high processing loads. One of the important factors in design of electronic devices is to design a smart cooling system to remove the generated heat well in time for a reliable and longer life. Water-cooled heat sinks are replacing air-cooled heat sinks with the rapid compactness and high process requirements. In this work, we introduced a slab in mini-channel and evaluated the thermal performance of mini-channel heat sink. The boundary layer separately develops in upper and lower portions of channel, which enhanced the heat transfer. We changed the thickness of slab from 0.2 to 1.6 mm for fin spacing of 0.5 mm and 1 mm, respectively, to determine the effects of thickness on overall thermal performance of heat sink. The computed values were then compared with the data available in the literature without slab. The minimum base temperatures recorded for 0.2-mm-thick slab with fin spacing of 0.5 mm and 1.0 mm were 40.1 °C and 42.4 °C, respectively. This represents a reduction of 12.5% and 16.2%, respectively, in the base temperature as compared to the base temperature without a slab.

Experimental investigation on flow boiling characteristics of radial expanding minichannel heat sinks applied for two-phase flow inlet

Generally, two-phase (TP) flow inlet condition is not allowed for conventional microchannel heat exchangers, and a certain subcooled degree of liquid is strictly required to guarantee the efficient operation of system. To solve multi-heat sources cooling issue, a type of circular radial expanding minichannels heat sink (REMHS) utilizing flow boiling of deionized water is proposed in present work. Flow boiling heat transfer of REMHS is investigated with the inlet vapor mass qualities in the range of 0.01–0.53. Under TP flow inlet, slug-annular and annular flows are the main flow patterns observed in REMHS in this work, where the low-medium mass flux (22–132 kg/m2s) and medium-high heat flux (33.1–176.4 kW/m2) conditions are applied. The experimental results illustrate that the proposed REMHS under TP flow inlet maintains a stable and high flow boiling heat transfer performance without occurring heat deterioration. When xin increases from 0.04 to 0.53, the maximum local heat transfer coefficient increases by 22% from 42.5 to 51.9 kW/m2K. The flow distribution among the expanding channel array is relatively uniform and the heat transfer capability in the REMHS displays a good symmetry under TP flow inlet. The maximum discrepancy in heat transfer coefficient is below 19% within our experimental range. Six classic flow boiling heat transfer correlations are compared with the experimental results, and Li & Wu's correlation gives a good prediction on all the measured data with MAE of 21.1%. Besides, the thermal independence of REMHS connected in series is also examined, and the mutual interaction in heat transfer between the REMHS in series is trivial, the proposed REMHS is expected to be applied to multi-heat source cooling.

Thermal-hydraulic analysis for alumina/water nanofluid inside a mini-channel heat sink with latent heat cooling ceiling-An experimental study

Abstract In this paper, an experimental investigation is carried out to evaluate the heat dissipation performance of the parallel mini-channel heat sink with the latent heat cooling ceiling. The heat sink is under the influence of an isothermal heating from the below. To enhance the cooling capacity of the system, the alumina/water nanofluid with various mass fractions of nanoparticles is considered as the working fluid. A micro-encapsulated phase change material layer is installed on the ceiling of the heat sink to cool down the fluid along the length of the heat sink. The experiments are performed for different values of mass fraction of nanoparticles, Reynolds number, mean temperature of bottom wall, inlet temperature of fluid, and mean temperature of cooling upper plate. The effects of these parameters on the friction factor, the mean Nusselt numbers dependent on the inlet and bulk temperatures difference, and the coefficient of performance are investigated. The experimental results indicate that the inlet temperature of the nanofluid has negligible effects on the friction factor for the base fluid Reynolds numbers of 483 and 968. However, the friction factor decreases as the inlet temperature increases for the base fluid Reynolds number of 161. The mean Nusselt numbers dependent on the inlet and bulk temperatures difference decrease by using a working fluid with the higher inlet temperature. The coefficient of performance increases with increasing the mean temperature of bottom wall from 50 °C to 55 °C. Finally, the mean temperature of cooling upper plate has negligible influences on the coefficient of performance.

Thermal analyses of minichannels and use of mathematical and numerical models

Growth in electronic devices comes with a challenge to engineers to provide proficient cooling mechanism in order to evade performance decline. Minichannel heat sinks are one among type of cooling devices to absorb heat formed in the electronic devices. Air is largely employed as cooling fluid in minichannels, but innovative methods are also adopted to enhance the heat transfer during the process. These days with modifications in the fluid flow passage and using liquid coolants such as nanofluids the Nusselt number is enhanced. These structural modifications adopted and different nanofluids employed with various volume concentrations and flow rates passed through minichannels to obtain enhancement in heat transfer rate are compiled in this article. The approach for these investigations is majorly categorized into numerical and experimental works. Numerical studies consisting of wide spread modeling methods like single phase/two phase flow modeling, laminar, transition/turbulent modeling etc. are reviewed. The related in-depth numerical and mathematical models used for computational analyses are detailed out exclusively. Experimental methods consisting of unusual passive techniques such as dimples/protrusions, pin fins, and corrugated channels. to achieve betterment in minichannel thermal performance are also provided. Another prime highlight of this article is compilation (in tabular form) of all the correlations and mathematical models used and developed to analyze different factors/properties during the thermal analyses. This article is concluded by providing an overall idea of different mathematical models and methods adopted in minichannels heat transfer analyses and future aspects to be addressed. Several important areas in minichannels heat transfer analyses exist which demand the optimization of heat and fluid flow processes and the use of machine learning concepts for analysis.

Numerical investigation of laminar flow and heat transfer in a liquid metal cooled mini-channel heat sink

With the recent trend of miniaturization and high-power output, effective heat dissipation has become the top priority in several industrial applications. This work contributes to the novel and efficient cooling technique that utilizes the liquid metal as working fluid. A numerical analysis of laminar flow and forced convective heat transfer of Galinstan through a mini-channel heat sink exposed to a constant heat flux has been presented. A detailed parametric analysis of the influence of heat sink's geometry, and the inlet velocity on the pressure drop, pumping power and the maximum heat flux has been carried out. Optimized heat sink's dimensions and inlet velocity are obtained. Furthermore, the numerical results are compared with the analytical correlations and discussion concerning the agreement and discrepancy is made. In addition, the flow and heat transfer performance of mini-channel heat sink cooling using liquid metal, nanofluid and water are compared, which intuitively shows the advantage of using liquid metal as coolant.

Numerical Investigation of Rough Micro- and Mini-channel Heat Sinks for Varying Aspect ratio

Numerical simulations are performed to study the impact of aspect ratio on the micro- and mini-channel heat sink behaviours in the presence of sinusoidal surface roughness. A CFD model is first validated with the relevant reference data for laminar flow conditions using ANSYS-Fluent analysis. The found results of this validation study show that the simulation results agree well with the reference data. The considered channel height, absolute roughness height and diameter are 250 µm, 30 µm and 366 to 374 µm, respectively. The top and bottom rough walls are under constant heat flux conditions, while other walls are adiabatic with air as the working fluid. The micro- and mini-channels with long wetted perimeter and lower aspect ratio have shown more convective heat transfer but with slightly higher frictional resistance. The convective heat transfer and thermal performance factor both improve with the increase in Reynolds number where all the values are higher than 1. The maximum value of the thermal performance factor is noted up to 1.6 for the channel having aspect ratio of 0.038 (Reynolds number = 250). This study shows that micro- and mini-channel heat sinks are sensitive to surface roughness, Reynolds number where varying aspect ratio have influence on both flow and heat transfer performances in laminar regime.

Study of Mini Channel Heat Sink with Different Internal Configuration

In this paper a numerical analysis of three-dimensional laminar flow through rectangular channel heat sinks of different geometric configuration is presented and a comparison of thermal performance among the heat sinks is discussed. Liquid water was used as coolant in the aluminum made heat sink with a glass cover above it. The aspect ratio (section height to width) of rectangular channels of the mini-channel heat sink was 0.33. A heat flux of 20 W/cm2 was continuously applied at the bottom of the channel with different inlet velocity for Reynold’s number ranging from 150 to 1044. Interconnectors and obstacles at different positions and numbers inside the channel were introduced in order to enhance the thermal performance. These modifications cause secondary flow between the parallel channels and the obstacles disrupt the boundary layer formation of the flow inside the channel which leads to the increase in heat transfer rate. Finally, Nusselt number, overall thermal resistance and maximum temperature of the heat sink were calculated to compare the performances of the modified heat sinks with the conventional mini channel heat sink and it was observed that the heat sink with both interconnectors and obstacles enhanced the thermal performance more significantly than other configurations. A maximum of 36% increase in Nusselt number was observed (for Re =1044).

Enhancing thermal-hydraulic performance of counter flow mini-channel heat sinks utilizing secondary flow: Numerical study with experimental validation

Continual growth of hydraulic and thermal boundary layers along stream wise direction in conventional straight fin mini-channel heat sink (MCHS) causes gradual deterioration of their thermal performance. To enhance thermal-hydraulic performance by breaking and re-development of the boundary layers, this research aims to introduce a novel water cooled inter-connected counter flow mini-channel sink (ICMCHS). Two inter-connectors (ICs) were positioned transversely between two counter flow mini-channels (CMCs) which segmented the flow domain into three zones (zone 1–3). Secondary flow was generated through the ICs utilizing the pressure difference of the adjacent CMCs resulting in disruption of the hydraulic and thermal boundary layers. To examine the effect of the ICs location and width on the thermal-hydraulic characteristics of the counter flow mini-channel heat sink (CMCHS), the present numerical studies were carried out for nine different cases (case 1–9) by varying ICs width from 1 mm to 1.5 mm and ICs location from 4 mm to 9 mm. A corresponding conventional CMCHS was chosen as the base case in contrast to the newly proposed ICMCHS. Experiments were also carried out for CMCHS to validate numerical results, and excellent agreement was found between measured values and the corresponding numerical results. At the lowest considered Re (Re = 150), a maximum value of Performance Evaluation Criterion (PEC) was achieved to ~1.22 for the highest length of zone 1 and 3 and the lowest ICs width (case 7), whereas at the highest Re (Re = 1044), the maximum PEC value (~1.42) was recorded for the intermediate length of zone 1 and 3 and the highest ICs width (case 6).

Effect of different nanoparticle-dispersed nanofluids on hydrothermal-economic performance of minichannel heat sink

Hydrothermal and energy-economic performances of minichannel heat sink are experimentally compared by using water-based different nanoparticle-dispersed mono and hybrid nanofluids. Al2O3, AlN, CNT, Cu and capric acid as phase change material (PCM) are considered. Different nanoparticles combinations (oxide–PCM, oxide–nitride, oxide–carbon nanotube and oxide–metal) in 50/50 volume ratio with water (base fluid) are taken as working fluids. The effects of volume flow rate (0.1–0.5 LPM) or Reynolds number (50 to 500) and total particle volume concentration (0.01–0.1%) are investigated. Convective heat transfer coefficient and pressure drop increase by about 42.3% and 22%, respectively, for Al2O3 + CNT nanofluid. The maximum reduction of 26.6% in thermal resistance is obtained for Al2O3 + CNT nanofluid as compared to base fluid. Heat transfer effectiveness and figure of merit are above one for all the hybrid nanofluids, which conclude that hybrid nanofluid is a better option over base fluid for minichannel heat sink. Al2O3 + CNT hybrid nanofluid is better in terms of heat transfer effectiveness, but Al2O3 + AlN hybrid nanofluid yields higher heat transfer coefficient to pressure drop ratio and coefficient of performance. The lower nanoparticle volume concentration in nanofluid is preferable due to higher stability, lower clogging and lower cost per cooling capacity of heat sink.

Thermal performance of phase change nano-emulsion in a rectangular minichannel with wall conduction effect

The minichannel heatsink is one of the small heat exchangers, having high heat capacity and being able to remove substantial heat within a very small volume, in line with the current demand for heat dissipation of electronic components. In the present study, the convection cooling characteristics in a rectangular minichannel considering wall conduction effect was investigated numerically. Numerical simulations are performed under 2% and 10% volume fractions of PCM particles (n-eicosan). The results reveal that the axial wall conduction plays a more pivotal role in the minichannels at the lower Reynolds number. Besides, the employment of phase change nano-emulsion in the working fluid in the rectangular minichannel suppresses the wall temperature and improves the heat transfer performance up to 4.23% and 9.36%, respectively, compared with the application of pure water. In addition, it is demonstrated that a high concentration of PCM particles may have detrimental effect on pressure drop and extended wall heat dissipation efficiency under certain circumstances thus the concentration of PCM particles needs careful selection.

Experimental hydrothermal characteristics of minichannel heat sink using various types of hybrid nanofluids

The hydrothermal characteristics of minichannel heat sink are analyzed experimentally by using deionized (DI) water based different nanoparticles mixture dispersed hybrid nanofluids. Al2O3, MgO, SiC, AlN, MWCNT and Cu nanoparticles are considered for this study. Different nanoparticles combinations (oxide-oxide, oxide-carbide, oxide-nitride, oxide-carbon nanotube and oxide-metal) in 50/50 vol ratio with base fluid (DI water) have been taken as coolants for volume concentration of 0.01%. Effects of volume flow rate (0.1–0.5LPM), fluid inlet temperature (20–40 °C) and Reynolds number (50–500) are studied for heat flux of 50 W/cm2. Convective heat transfer coefficient and pressure drop are increased by about 42.24% and 22% for Al2O3 + MWCNT hybrid nanofluid. The maximum reduction of 21.36% in thermal resistance is obtained for Al2O3 + MWCNT hybrid nanofluid in comparison to DI water. Heat transfer effectiveness and figure of merit are above one for all the hybrid nanofluids which conclude that hybrid nanofluid is better option for electronics cooling over DI water. Al2O3 + MWCNT hybrid nanofluid is better in terms of heat transfer effectiveness; whereas, Al2O3 + AlN hybrid nanofluid (oxide-nitrite mixture) has maximum heat transfer coefficient to pressure drop ratio and coefficient of performance.

Water-based nano-PCM emulsion flow and heat transfer in divergent mini-channel heat sink—An experimental investigation

In this work, an experimental investigation is performed to study the water-based nano-PCM emulsion flow and heat transfer in the divergent mini-channel heat sinks (MCHSs). The divergent rectangular MCHS is selected in this study as it provides a higher heat transfer along with smaller value of pressure drop as compared with the parallel one. The water-based microencapsulated n-eicosane PCM suspension is considered as the coolant. Indeed, the particles of microencapsulated n-eicosane PCM are suspended in the water. The diameter of these particles is 130 nm. The divergent angle of 2.06° is used for fabricating the divergent mini-channels. The influences of various parameters such as the Reynolds number, the heat flux, and the concentration of nano-PCM particles on the thermal resistances, the figure of merit (FOM), the friction factor, coefficient of performance (COP), and the heat transfer effectiveness are investigated. The findings of this study indicate that the mean and maximum thermal resistances decrease about 0.5% and 4.92%, respectively by increasing the input heat flux from 40.38 W to 60.08 W at Re = 100 for the case of base fluid. The maximum FOM value is equal to 1.02 that can be achieved at ωPCM = 2%, Re = 305, and qh″=4.79W/cm2. Using the nano-PCM emulsion with a large concentration increases considerably the pressure drop penalty and provides a poor FOM index. The mean heat transfer effectiveness is higher than unity for smaller values of the Reynolds number. However, the mean heat transfer effectiveness diminishes for larger values of the Reynolds number.

Experimental hydrothermal behavior of hybrid nanofluid for various particle ratios and comparison with other fluids in minichannel heat sink

The effect of the particle mixture ratio in hybrid nanofluid on minichannel heat sink performance is analyzed experimentally. The heat sink, made of aluminium, contains nine parallel rectangular minichannels having cross section of 1 mm × 3 mm with 30 mm length. Total 0.01% volume concentration of Al2O3 and MWCNT nanoparticles for various mixing ratios (10:0, 8:2, 6:4, 4:6, 2:8 and 0:10) is used to synthesize water-based hybrid nanofluids. Different parameters as volumetric flow rate (0.17–0.5 LPM), fluid inlet temperature (20–40 °C) and heat flux (8.3 W/cm2) are considered. Present Al2O3-MWCNT hybrid nanofluid is compared as well with hybrid nanofluids available in literature based on both thermophysical-transport and hydrothermal properties. Heat transfer coefficient, Nusselt number, pressure drop and friction factor increase with an increase in MWCNT fraction in hybrid nanofluid. Maximum heat transfer coefficient and pressure drop increments are 44.1% and 68.1%, respectively, for MWCNT nanofluid. Inlet fluid temperature has a negative effect on pressure drop and positive effect on heat transfer coefficient. Nusselt number to friction factor ratio is observed maximum at 6:4 mixing ratio of Al2O3 and MWCNT. Al2O3 + MWCNT (optimum mixing ratio of 6:4) hybrid nanofluid is found better as compared to existing hybrid nanofluids at total volume concentration of 0.01%.

Second law analysis for nanofluid flow in mini-channel heat sink with finned surface: a study on fin geometries

In this numerical work, a second law analysis is carried out for the nanofluid flow and heat transfer in the mini-channel with finned surface. The mini-fins with various geometries, including trapezoidal, square, triangular, and sinusoidal, are located on the bottom surface of the mini-channel. The effects of mini-fins geometry, mini-fins number, Reynolds number, and solid volume fraction of nanoparticles on the temperature and velocity distributions, frictional and thermal irreversibilities, and Bejan number inside the mini-channel are studied. The numerical method is validated with the experimental data. The results show that the sinusoidal, triangular, square, and trapezoidal mini-fins generate up to 66.23%, 61.87%, 59.21%, and 57.80%, respectively, lower thermal irreversibility as compared with the smooth mini-channel. Among mini-fin geometries, the triangular mini-fins generate the maximum frictional irreversibility, while the trapezoidal mini-fins provide the minimum frictional irreversibility. The frictional irreversibility increases about 108.56%, while the thermal irreversibility decreases up to 46.33% as the mini-fin number increases from one to nine. The thermal irreversibility diminishes about 49% by boosting the Reynolds number from 100 to 500. Usage of nanofluid increases both frictional and thermal irreversibilities. Finally, the thermal irreversibility is a dominant term in the total irreversibility and the effects of frictional irreversibility can be ignored.

Thermally Developing Flow and Heat Transfer in Elliptical Minichannels with Constant Wall Temperature.

Laminar convective heat transfer of elliptical minichannels is investigated for hydrodynamically fully developed but thermal developing flow with no-slip condition. A three-dimensional numerical model is developed in different elliptical geometries with the aspect ratio varying from 0.2 to 1. The effect of Reynolds number (25 ≤ Re ≤ 2000) on the local Nusselt number is examined in detail. The results indicate that the local Nusselt number is a decreasing function of Reynolds number and it is sensitive to Reynolds number especially for Re less than 250. The effect of aspect ratio on local Nusselt number is small when compared with the effect of Reynolds number on local Nusselt number. The local Nusselt number is independent of cross-section geometry at the inlet. The maximum effect of aspect ratio on local Nusselt number arises at the transition section rather than the fully developed region. However, the non-dimensional thermal entrance length is a monotonic decreasing concave function of aspect ratio but a weak function of Reynolds number. Correlations for the local Nusselt number and the thermal developing length for elliptical channels are developed with good accuracy, which may provide guidance for design and optimization of elliptical minichannel heat sinks.

Particle ratio optimization of Al2O3-MWCNT hybrid nanofluid in minichannel heat sink for best hydrothermal performance

Interesting hydrothermal behavior of hybrid nanofluid containing combination of dissimilar particles (completely different in terms of shape, size and properties) by changing their ratio is unexplored yet, which is analyzed experimentally for minichannel heat sink. Nine parallel rectangular minichannels are used in the heat sink each of which has 1 mm width, 3 mm depth and 30 mm length. Al2O3–MWCNT/water hybrid nanofluid of 0.01% volume concentration with various nanoparticle mixture ratios is used as coolant to analyze the effect of Reynolds number and working fluid inlet temperature. Nanoparticles mixing ratios (5:0, 4:1, 3:2, 2:3, 1:4 and 0:5) have been taken as volume ratios. Convective heat transfer coefficient, Nusselt number, pressure drop and friction factor increase with an increase in fraction of MWCNT in hybrid nanofluid. A maximum enhancement of 44.02% has been observed for the convective heat transfer coefficient with MWCNT (5:0) hybrid nanofluid as compared to water. Maximum pressure drop has been increased by 51.2% over base fluid at an inlet temperature of 20 °C for the MWCNT (5:0) hybrid nanofluid. Inlet fluid temperature has negative effect on pressure drop and positive effect on heat transfer. The observed optimum volumetric mixing ratio of Al2O3 and MWCNT is around 3:2, for which hybrid nanofluid yields maximum heat transfer coefficient to pressure drop ratio. Performance evaluation criteria (PEC) has been evaluated greater than 1 for all the nanofluids, which concludes that nanofluids are better option as compared to conventional fluid (DI water). Based on the experimental data, correlations for Nusselt number and friction factor have been introduced with R2 values of 98.8% and 96.3%, respectively, and compared with available correlations.