Bottom Wall Temperature Research Articles

Heat transfer performance of microchannel heat sink with combined manifolds and bottom wall structures

The heat generated during operation gradually increases with the continuous miniaturization and integration of electronic components. High temperatures and thermal non-uniformity pose serious threats to the stability and reliability of the devices. Therefore, four bottom wall structures for manifold microchannel heat sinks were proposed, namely straight, wavy, zigzag, and right-angled triangle bottom walls. The results show that the right-angled triangle bottom wall exhibits optimal cooling performance, bottom wall temperature uniformity, and comprehensive temperature uniformity among these four structures. Additionally, 56 types of microchannel heat sinks with combined manifolds and right-angled triangle bottom walls for numerical study were designed. For bottom wall temperature uniformity and overall temperature uniformity, the optimal microchannel heat sink with combined manifolds and right-angled triangle bottom wall had a temperature uniformity factor and comprehensive temperature uniformity factor of 0.360 and 0.828, respectively. Compared to the straight bottom wall, the optimal right-angled triangle bottom wall reduced the temperature uniformity factor and comprehensive temperature uniformity factor by 16.86 % and 17.20 %, respectively. In terms of cooling performance, the optimal microchannel heat sink with combined manifolds and right-angled triangle bottom wall had an average temperature of the bottom wall of 324.02 K. Compared to the straight bottom wall, the optimal right-angled triangle bottom wall reduced the average temperature of the bottom wall by 4.07 K. This study provides valuable references for the design of microchannel heat sinks for high heat flux electronic devices.

Thermal analysis of a turbulent wall jet over an adiabatic wavy surface

The impact of wavy wall amplitude on the turbulent characteristics of a wall jet has been investigated experimentally, where the wavy wall is given an adiabatic condition. In the experimental study, the mean and turbulent velocity are measured using a constant temperature anemometer manufactured by Dantec Dynamics. For temperature measurement over the wall and within the flow domain, the FLIR camera and k-type thermocouple are used, respectively. For the current study, uniformly heated at △T0 = (T0 − T∞) = 30 ± 1.2 0C with a Reynolds number of 15,000 is utilized to flow over a sinusoidal wavy wall (y = A*sin (ωx)), where “A = Amplitude ⁄ a” is the amplitude normalised by the nozzle height “a". The nozzle height is 20 mm and to maintain the Reynolds number 15,000 at the inlet, velocity is set at 10.95 ± 0.36 m ⁄ s. The amplitude of the wavy wall is varied between 0.2 and 0.6 and the results are compared to those of the plane wall jet. The current problem is also numerically solved using the k − ε RNG and k − ω SST models. Based on the results, it is concluded that the k − ε RNG model predicts the wavy wall results quite well. It is also discovered that the thermal self-similar profile deviates from the Gaussian curve at the crest of the wavy wall. The influence of the wavy surface on the thermal characteristics of the turbulent wall jet is more pronounced in the near flow field. It is observed that the bottom wall temperature, fluctuating temperature and turbulent heat flux decrease with the increase in amplitude. This indicates that for the higher amplitude, the turbulence increases, which increases the intermixing of jet fluid with the colder ambient fluid. The present results can be used as a benchmark for validating numerical models working in this area.

Numerical study of continuous Czochralski (CCz) silicon single crystal growth in a double-side heater

The effect of heater power control on heat, flow, and oxygen transport for the CCz growth of 8-inch diameter silicon crystal in a triple-crucible was numerically studied. Three different designs of a double-side heater at different power ratios of the lower and upper side heaters (PRSD = 0.25, 1, and 4) were compared with the case of a single-side heater. For the cases considered in the present work, a design in which the upper side heater was shorter than the lower one at PRSD = 0.25 could be a good choice for improving the crystal quality and CCz growth. This was shown by the reductions in the crystal-melt interface deflection and oxygen content and the increase in the melt temperature in the feeding zone. In this case, reducing the interface deflection and crucible bottom wall temperature could enhance the pulling speed. However, the power consumption in this condition was higher than that in the single-side heater case. Achieving a lower heater power was feasible with a higher PRSD value. However, it was important to note that the oxygen content would be higher, and the melt temperature in the outer melt significantly dropped.

Heat transfer enhancement in turbulent dual jet and its thermal characterizations using large eddy simulation

Heat transmission is the prime aim of any thermal device that requires effective cooling. This requirement becomes significantly more vital for a turbulent jet, which is encountered quite often in industrial and engineering purposes. The present study investigates thermal and turbulence characteristics of a turbulent dual jet using Large Eddy Simulation (LES). The bottom surface is maintained at isothermal and isoflux boundary conditions and the flow Re is 7500. The profiles of Reynolds shear-stress, turbulence kinetic energy, wall friction coefficient, r.m.s. temperature, mean Nusselt number, bottom wall temperature, and turbulent heat fluxes are investigated and scaled using outer, thermal and inner parameters. Variations in Nusselt number and bottom wall temperature are also studied. A significant rise in Nusselt number is observed nearer to the jet exit which enriches the cooling rate. Overall, the finding shows that compared to the wall jet and parallel flowing offset jet, the inflection point in the mean temperature profile of the present dual jet scaled with the thermal variable and outer variable is higher. Further, it is also observed that the thermal transmission spreading out of the wall is quite efficient in the low-pressure area of the dual jet. Near-wall eddies and the development of roller-like structures are seen. The interaction occurring through the inner and outer layers increases the momentum transfer along with turbulent heat-flux and a large amount of heat is lost due to turbulent flow.

Local hydrothermal characteristics and temperature uniformity improvement of microchannel heat sink with non-uniformly distributed grooves

In order to improve the temperature uniformity of bottom walls, a novel design of microchannel heat sink with From-Sparse-To-Dense embowed grooves (MC-FSTD) was proposed as well as a comparative one with From-Dense-To-Sparse embowed grooves (MC-FDTS). The local hydrothermal characteristics and temperature distribution variance of bottom wall of microchannel heat sinks were numerically investigated for Reynolds number (Re) ranging from 100 to 800. The results showed that the denser grooves led to lower flow velocity, lower local friction factor and higher local pressure as well as the lower bottom wall temperature (Tw) and higher local Nusselt number (Nuz). The local Nusselt number and the bottom wall temperature of MC-FSTD were 2.17 times higher and 9.1K lower than that of MC-SC at z = 10 mm, respectively. MC-FSTD also had the most uniform temperature of the bottom wall and the corresponding temperature variance was 6.42 times lower than that of MC-SC at Re = 795.38. The heat transfer entropy generation rate and the total entropy generation rate of MC-FSTD were also the lowest with an acceptable friction entropy generation rate. Finally, the effects of the decreasing magnitude (Li) of the distance between two adjacent grooves on the local hydrothermal characteristics and temperature uniformity of MC-FSTD were explored and the total entropy generation rate was further reduced to 5.22 × 10−4 W/K at Li = 0.015 mm and Re = 795.38.

Experimental investigation on heat transfer of supercritical water flowing in a horizontal tube with axially non-uniform heating

For a heat exchanger, the heat flux is usually non-uniform in the axial direction, and the knowledge about heat transfer of supercritical water with axially non-uniform heating is scarce. To fill the gap, experiments were conducted in a horizontal tube to study the heat transfer characteristics of supercritical water with axially sinusoidal heating. The pressures varied from 23.5 to 26.5 MPa, mass fluxes 200 to 400 kg·m−2·s−1 and average heat fluxes 50 to 150 kW·m−2. Compared with uniform heat flux, the temperature difference between the top and bottom wall is larger than that of the axially sinusoidal heat flux. The inner-wall heat flux is non-uniform along the circumference due to the temperature difference, being higher at the side wall and lower at the top wall. A relative heat flux parameter is defined to describe the relative magnitude of the local heat flux. The relative heat flux parameter of the top generatrix, which is inversely proportional to the average heat flux, decreases linearly with the increase of the temperature difference between the top and side generatrix. The non-uniform degree of heat flux along the circumference is positively correlated with the average heat flux. Additionally, the local heat transfer characteristics should be considered in horizontal tubes. On the one hand, the heat transfer deterioration may occur when the fluid temperature near the top wall is higher than the pseudo-critical temperature and it can be suppressed with increasing Reynolds number. On the other hand, the local heat transfer can be enhanced if the side and bottom wall temperatures exceed the pseudo-critical temperature.

Enhanced heat transfer of supercritical n-decane in cooling channels with triangular ribs for regenerative cooling

• A continuous ribbed channel is designed to enhance the cooling capacity. • The channel can provide up to 2.04 times superior heat transfer performance. • The insertion of ribs enhances the uniformity of buoyancy distribution. • The triangular rib channel improves axial temperature uniformity. • The mechanism of generating vortices in the slot is analysed. Regenerative cooling is regarded as an effective method for managing the heat of scramjet combustors, and the design of cooling channels is critical for removing more heat from the engine. A continuous triangular rib channel was proposed. The effects of rib position, height, and pitch on the heat transfer performance were investigated using Fluent 18.0. The SST k –ω turbulence model was used to study the thermal behaviour of supercritical n-decane in channels and showed good agreement with the experimental data. Results show that the insertion of triangular ribs at the bottom and top can reduce the bottom wall temperature by 243.8 K in the studied case. The triangular rib channel can provide up to 2.04 times superior heat transfer performance. The continuous triangular ribs significantly reduced axial temperature inhomogeneity. Local streamlines were studied to demonstrate the influence of rib parameters on the flow and heat transfer processes. A local heat transfer enhancement occurs when the rib has a large inclination. For the studied conditions, the generation of vortices was carefully evaluated, and it was found that the generation of vortices in the slot was related to the value of h / p .

Numerical investigations on the effect of multi-dimensional stepness in open micro pin fin heat sink using single phase liquid fluid flow

In present work, the square shaped micro pin fin configuration of microchannel heat sink has been numerically investigated under different geometrical variation. Considering effectiveness of open microchannel, the pin fin height has been varied in two different styles. Firstly, the consecutive pin fins are varied in step of two and three rows. Secondly, the step variations were opted along only the channel length (unidirectional) and along both channel length and channel width (bidirectional). Furthermore, all configurations are having equal convective area so that influence of out of plane mixing can be studied more precisely. Estimated findings clearly indicated that stepped configuration has superior thermo-hydraulic performance compared to uniform configuration due to out of plane fluid motion resulting in enhanced flow mixing. Afterwards, bidirectional step has shown augmented performance compared to unidirectional step heat sink configuration because of enhanced secondary fluid flow and distinct vortices formation behind each pin fins. Among all considered configurations, three stepped bidirectional micro pin fin heat sink has yielded best performance i.e. 28.3% higher heat transfer rate and 2% lesser average bottom wall temperature compared to uniform height pin fin configuration.

Dehydrogenation of perhydro-dibenzyltoluene for hydrogen production in a microchannel reactor

A preliminary study regarding the dehydrogenation of perhydro-dibenzyltoluene as a liquid organic hydrogen carrier with switching from a stirred tank reactor to a continuous flow microchannel reactor is presented. The hydrogen production percentage in the case of a continuous flow microchannel reactor was found greater when compared to that of a stirred tank reactor. The hydrogen production was increased from 64.1% to 82.2% with the increase in bottom plate temperature from 260 to 320 °C for 0.01 mL/min flow rate. A maximum of 88% of hydrogen was generated for a 40 hours of operation, at a bottom wall temperature of 290 °C. The kinetic model for the microchannel reactor dehydrogenation was presented with a pre-exponential factor of 3.272 s−1 and activation energy of 13.79 kJ/mol. The results revealed that a continuous microchannel reactor can be an appropriate technology for the dehydrogenation of perhydro-dibenzyltoluene.

Performance Enhancement of Double-Layer Microchannel Heat Sink by Employing Dimples and Protrusions on Channel Sidewalls

High-temperature gradient causes thermal stress and is indirectly responsible for other demerits in nonstacked microchannels. High-temperature gradient is overcome by employing double layers in the heat sink. Utilization of dimple and protrusion in such double-layered sink to enhance overall performance is done in the present numerical study. Before placement of dimples and protrusions on sidewalls of the sink, optimum width and depth of channel have been assessed. Microsinks with the protruded-dimpled bottom layer and microsinks with protruded-dimpled layers are investigated. The parameters such as maximum bottom wall temperature difference (ΔTb), Nusselt number ratio (Nu/Nuo), and thermal performance factor (η) have been evaluated. The impact of aligned and staggered arrangements of dimple and protrusion is also compared. Deionized water as a coolant for the range of Reynolds number of 89–924 is examined. It has been realized that aligned models offer higher heat transfer coefficient, maximum Nu, and minimum ΔTb, but in terms of overall performance, staggered sinks are superior. The heat sink with both layers protruded and dimpled, showing Nu/Nuo and η of 1.36 and 1.32, respectively, is observed as one of the optimum sinks which offers an excellent lowest ΔTb of 1.48 K.

Simulation Research on Flow Boiling and Heat Transfer of Micro-channel for Electronic Cooling

Micro-channel heat exchanger is a popular device for the electronic cooling. Heat transfer of flow boiling in micro-channel is a research hotspot. For the convenience of the theoretical research on micro-channel, a high efficiency simulation model on flow boiling and heat transfer of micro-channel was established. In the simulation research, the influence rules of operating conditions and thermal properties of refrigerants (working fluids) on the flow boiling were studied; the distribution rules along flow direction of characteristic parameters such as vapor quality, Heat Transfer Coefficient (HTC), pressure drop and bottom wall temperature of micro-channel T w were analyzed; the key factors on the distribution of characteristic parameters were proposed. The characteristic parameters based on the refrigerants R134a and R1234ze(E) in micro-channel were compared and researched. According to the simulation results, HTC and pressure drop of R134a are larger and smaller than those of R1234ze(E) respectively, the uniformities of HTC and T w of R134a are all better than those of R1234ze(E) respectively.

Heat transfer enhancement using double taper microchannel

A three-dimensional numerical study on the combined effect of height as well as width tapering on the thermal performance of double taper microchannel is presented in this paper. The channel inlet width is considered as 300 µm, taper ratio on sidewalls and bottom wall are varied from 0 to 1 and 1 to 3.9, respectively. The thermal resistance ratio, average bottom wall temperature, temperature difference ratio, and pumping power ratio of the channel are evaluated for various flow rates, height, and width tapering. Results showed higher reduction of wall temperature with combined effect height as well as width tapering compared with straight channel. The optimal size of the micro channel to minimize the pumping power and average wall temperature on the constraint of heat flux and footprint area is found. The reduction in average bottom wall temperature is 17.34%, and pumping power ratio is 0.44 (56% power reduction) noted, respectively, at Reynolds number 340. Finally, optimal dimension of double taper microchannel is evaluated for better thermo-hydraulic performance.

Experimental Investigation of Near- and Supercritical Heat Transfer to R125 Flowing in a Horizontal Tube

Knowledge about supercritical heat transfer to refrigerants with horizontal flow is scarce and experimental data is mostly lacking. This makes an accurate sizing of heat exchangers impossible. In addition, the majority of the tested geometries in literature are limited to an inner diameter of only 16 mm. In order to close the gap and increase the knowledge about supercritical heat transfer, a novel experimental setup was used to investigate supercritical heat transfer phenomena on larger tube diameters. The test section consists of a horizontal counter current tube-in-tube heat exchanger. R125 flows in the inner tube having an inner diameter of 24.77 mm. The influence of mass flux (226 - 585 kg/m2s), heat flux (7.7 - 21.9 kW/m2) and supercritical pressure (3.7 - 4.1 MPa, corresponding to 1.03 - 1.12 times the critical pressure) on local forced convective heat transfer was investigated. No visible influence of pressure on the convective heat transfer coefficient is noticed, indicating that buoyancy is present and influential in the performed measurements. The applied heat flux does have an effect, with a decrease in the heat transfer coefficient for an increase in heat flux. This effect is more pronounced at higher mass fluxes. At high mass flux, increasing the heat flux with 42% results in a drop in heat transfer coefficient of 46%, while this is only 40% and 26% at medium and low mass flux, respectively. However, there appears to be a limit to this detrimental effect at higher mass fluxes. Finally, heat transfer increases for an increase in mass flux. Increasing the mass flux with 76% results on average in a rise in heat transfer coefficient of 88%, for measurements at medium heat flux. At high heat fluxes, an increase of 71% is observed for a rise in mass flux of 59%. Nine heat transfer correlations are evaluated. The majority underestimates the heat transfer significantly, however, two correlations operate adequately and are proposed as a basis for future correlation development. The unique dataset and insights presented in this work enable a better understanding of the heat transfer in supercritical vapor generators. Future work includes incorporating top and bottom wall temperature measurements, adjusting control and application of the heat flux and investigating refrigerants with a low Global Warming Potential.

Numerical analysis to study enhancement in heat transfer using wavy surface in turbulent dual jet

Enhancement in the heat transfer rate is an essential research area in the present time. Therefore, to achieve this goal in the present case, a sinusoidal wavy wall surface is used in a turbulent dual jet. The changes in amplitude (A) and number of cycle (N) of the sinusoidal wavy surface, not only affect the turbulent characteristics but also improve the heat transfer rate. In comparison to the plane wall surface in a dual jet, it is found that nearly 20.70% of improvement in heat transfer is achieved when N = 7 and A = 0.7. The A and N of the sinusoidal wavy surface are varied from 0.1 to 0.7 and 4 to 12 with an interval of 0.1 and 1, respectively. The Reynolds number (Re), offset ratio, and Prandtl number (Pr) are set to 15 × 103, 5 and 0.71, respectively, for all the computational simulations. The average Nusselt number (Nuavg) increases almost linearly when the amplitude changes from 0.1 − 0.7 up to N = 7. A new scaled self-similarity solution for the crest and trough positions is performed to neglect the effect of bottom wall variation. The similarity solution of the crest for various number of cycles in the combined region for different amplitudes suggests that when A ≥ 0.5, the profiles of all the number of cycles spread close to the wall region and in the outer region. Whereas, the self-similarity behaviour of trough shows that when A ≥ 0.3, the profiles of all the number of cycles spread only close to the wall region and almost coincide in the outer region and inflection point rises in the crosswise distance as amplitude increases. It is also noticed that the decay in bottom wall temperature increases with increasing A when N = 10, thereafter, the decrease in bottom wall temperature is nearly same beyond N > 9.

Thermohydraulic performance improvement and entropy generation characteristics of a microchannel heat sink cooled with new hybrid nanofluids containing ternary/binary hybrid nanocomposites

AbstractRecently, the combination of hybrid nanofluids with microchannel heat sinks (MCHSs) has led to superior heat removal from high heat flux electronics chips. The present work aimed to evaluate numerically the first and second law performances of MCHSs using the new cost‐effective binary/ternary hybrid nanofluids. Water‐based binary and ternary hybrid nanofluids include the MgO/TiO2 nanocomposite and the CuO/MgO/TiO2 nanocomposite, respectively. The effects of the hybrid nanofluid volume concentration (vol.%) and Reynolds number (Re) on the heat transfer, pressure drop, combined thermohydraulic characteristics, and entropy generation characteristics of the MCHSs are discussed. The results show that higher values of the convective heat transfer coefficient, pressure drop, and frictional entropy generation rate are obtained when using hybrid nanofluids with high Re and vol.% values. Furthermore, by increasing the Re and vol.% values of the hybrid nanofluids, the bottom wall temperature, total thermal resistance, and thermal entropy generation rate decreased, and an increased temperature uniformity was obtained on the bottom surface of the MCHSs. In conclusion, the applied hybrid nanofluids are considered to be more promising heat transfer fluids when compared with conventional fluids such as water. Particularly, the CuO/MgO/TiO2‐water ternary hybrid nanofluid exhibited a better heat transfer efficiency than did the MgO/TiO2‐water binary hybrid nanofluid.

Comparative Analysis of Heat Transfer and Fluid Flow in Circular and Rhombus Pin Fin Heat Sink Using Nanofluid

Abstract Numerical investigation has been carried out to compare the heat transfer performance and fluid flow behavior of microchannel heat sinks with circular and rhombus pin fins which are arranged in an in-line manner. Diameter and sides are 1 mm for circular and rhombus fins. Three-dimensional (3D) computational domain has been simulated using two types of cooling medium, i.e., water and Al2O3–H2O nanofluid. A comprehensive comparative analysis has been presented considering the coolants and pin fin profiles as variable parameters. Two operating variables, i.e., heat flux (q) and Reynolds number (Re), are varied in the range of q = 100–400 kW/m2 and Re = 100–400. A total of 64 cases have been simulated to identify the promising features of both the pin fins attributed to improved heat transfer and overall thermal performance. Comparison has also been made between the coolant medium to find out their heat dissipation potential and flow characteristics in the heat sink. Results obtained in terms of average bottom wall temperature, heat transfer coefficient, Nusselt number (Nu), and pressure drop demonstrate that heat sink with rhombus pin fins dissipates more heat compared to its counterpart. It is attributed to the shape and geometry of rhombus fins that facilitate distinct fluid flow behavior; nevertheless, the pressure drop is less in the circular fin heat sink. Moreover, for constant value of Re, nanofluid extracts more heat compared to water in both configurations of the heat sink.

Single-phase and Two-phase Flow and Heat Transfer in Microchannel Heat Sink with Various Manifold Arrangements

The manifold microchannel (MMC) heat sink, which possesses better heat transfer performance and less pressure drop than the traditional microchannel heat sink, has attracted much attention from researchers in recent years. But not much of them, either single-phase or two-phase ones, focused on the problems about flow maldistribution and wall temperature nonuniformity that might ultimately lead to system breakdown. To investigate the flow distribution in the MMC heat sink, six types of manifold, namely Z-type, C-type, H-type, U-type, ZU-type, and HU-type are considered in the current study. All six manifolds are investigated in single-phase cases with water, while the latter three are adopted in two-phase cases with HFE7100. The cases are solved with the self-developed codes based on the OpenFOAM package. The manifold arrangement has a strong impact on the overall heat transfer performance and pumping power required. The HU-type and ZU-type MMC heat sinks are recommended to be fabricated in the single-phase heat transfer application due to their small thermal resistance lower than 2×10−5 m2·K/W and pressure drop less than 500 Pa. Besides, if the pumping power is not a restriction factor in the system, Z-type MMC is also recommended. In the two-phase cases, the flow distribution is naturally not uniform within a parallel microchannel system, and the microchannels with large flow velocity appear to have higher wall temperatures. The authors recommend using HU-type MMC heat sink in the flow boiling application due to its bottom wall temperature distribution is relatively uniform with a difference of less than 2 K.

3D Lattice Boltzmann simulations for water droplet's impact and transition from central-pointy icing pattern to central-concave icing pattern on supercooled surfaces. Part I: Smooth surfaces

A water droplet's impact and its subsequent spreading, recoiling and freezing on a smooth substrate at a supercooled temperature is studied numerically using a 3D pseudo-potential lattice Boltzmann method, in combination with a solid-liquid phase-change model with volume expansion of water at 0°C taken into consideration. Simulated results show that a water droplet after its impact on a smooth surface at a supercooled temperature can form either a central-pointy icing pattern with a single ice peak, or a central-concave icingpattern in a donut shape, depending on the contact angle and the supercooled degree of the wall. Itisshown that the recoiling motion of the droplet after its impact on the supercooled substrate plays the dominant role in the formation of the central-pointy icing or central-concave icing pattern. The central-pointyicingpattern is formed on a substrate having a large contact angle where the recoiling motion of the droplet is strong while the central-concave icing pattern is formed on a substrate having a high degree of supercooled temperature (i.e., a large Stefan number) where the recoiling motion is terminated prematurely because of early nucleation of freezing on the supercooled substrate. The volume expansion during liquid to ice phase-change process at 0°C does affect the movement of the liquid phase although its effect on the formation of icing patterns is small. Effects of movement of freezing fronts on the shape of the icing patterns are illustrated. At fixed values of We= 320 and Re = 164.9, a map showing effects of contact angle and Stefan number (bottom wall temperature) on the formation of central-pointy icing or central-concave icingpatterns after a water droplet's impact (with D0= 100 and Pr = 13.5) on smooth supercooled surfaces is presented.

Surface coke deposition influences on flow and heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts

Surface coke deposition influences on the flow and heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts were experimentally investigated at supercritical pressures, to research the active cooling technology of new flying vehicles. The SS304 test tubes had a 4 mm inner diameter and a 6 mm outer diameter. The twist ratios of the two types of twisted-tapes are 6.31 and 12.63. The experimental system pressure, outlet temperature, and mass flow rate were fixed at 3 MPa, 893.15 K, and 1.20 g·s−1, respectively. The results indicated that the twisted-tape insert mixed the fluid, washed coke deposited on the inner wall, and improved the heat transfer. With the insertion of a twisted-tape, the maximum value of the pressure drop of the test section decreased more than 85%, the total amount of coke decreased more than 93%, and the wall temperature were significantly decreased. At the same axis position, the difference between the top and bottom wall temperatures decreased and the heat transfer coefficient improved compared with a plain tube. A well-predicted correlation of the Nusselt number was proposed.

Numerical investigation on the impact of protrusions mounted on sidewalls of double layered micro channel heat sink

Several passive cooling methods are utilized in electronics cooling. for the sake of their more reliability than active cooling and microchannel heat sink is the device suitable in such present trends of technology. With the evolution of microchannel, researchers predicted that microchannel with double layered pattern is more beneficial in terms of performance. The modification of channel geometry is implemented to get enhanced Nusselt number and heat transfer coefficient. The present work has the objective to implement protrusions on sidewalls of double layered microcahnnel. The influence of protrusions on thermal characteristics along with hydraulic profiles is investigated in the work. Two cases with protruded channel are evaluated and compared with a base smooth sink. Performance parameters are interestingly found superior for both protruded cases. These cases exhibit better Nusselt number and heat transfer coefficient than that of smooth-channel sink at all range of Re. For example, Nu of Case 1 is calculated maximum as 11.13 at the highest Re. In the study of bottom wall temperature, it has been found that convection heat transfer in channel occurs at higher rate due to the presence of protrusions.