Hydrothermal Performance Research Articles

Assessment of the hydro-thermal performance for a novel hexagonal mini-channel heat sink for cooling a cylindrical heat source

Liquid cooling using a mini-channel heat sink (MHS) has been highly efficient in cooling rectangular and cylindrical lithium batteries. This work proposed a new hexagonal MHS (HMHS) to cool a cylindrical heat source instead of the traditional cylindrical with smooth MHS (CSMHS). In addition to the smooth channels, four obstructed channels were proposed to further enhance the thermal performance of this HMHS. The obstructions used include: semicircular ribs–cavities, semicircular ribs–secondary flow, semicircular pin fins and semicircular pin fins–cavities. This study was numerically conducted using the finite volume method under water Reynolds number ranging from 100 to 800. CSMHS and HMHS with semicircular pin fins were manufactured and tested to verify the validity of the numerical results. Results showed that the HMHS exhibited superior hydro-thermal performance compared with the CSMHS. In addition, the HMHS with obstructed channels contributes to a significant improvement in thermal performance. The percentages of Nusselt number improvement with all channels were approximately: 12.3%, 60.5%, 71.5%, 104% and 112% for smooth, semicircular ribs–cavities, semicircular rib–secondary flow, semicircular pin fins and semicircular pin fins–cavities, respectively. Amongst all the channels, the channels with semicircular pin fins achieved the best performance with a hydro-thermal performance factor of 1.67.

Numerical simulation of an innovative design of solar air heater using spiral duct inserts for enhancing thermal efficiency

ABSTRACT An innovative design of solar air heater (SAH) with spiral shape is numerically analyzed in this paper. The spiral-shaped SAH hydro-thermal performance is studied for different air mass flow rates using CFD COMSOL Multiphysics software. The outlet air temperature difference, thermal efficiency, flow structure, thermal field and pressure drop are the main parameters which are considered to estimate the fluid flow and heat transfer behaviors of the SAH. The simulation is realized for 1000 W/m2 of solar heat flux and 25°C of ambient temperature as typical climatic conditions in a middle day. The results show that the maximum outlet temperature difference of the SAH reached 93.08°C with 0.0083 kg/s of air mass flow rate. For the range of 0.0083–0.0332 kg/s, the thermal efficiency is varied from 91.41% to 99.01%. The ambitious percentage of the thermal efficiency of 99.01% was observed for 0.012 kg/s. The proposed design provides high thermal efficiency of SAH compared to other configurations of SAH.

Convection flow of NE-phase change material-water mixture in evacuated tube solar collector manifold: Numerical analysis of MHD double-diffusive convection and exothermic reaction

This study investigates the convection flow of nano-encapsulated phase change material (NEPCM)-water mixture in an evacuated tube solar collector manifold, focusing on the effects of magnetohydrodynamic (MHD) double-diffusive convection and exothermic reaction. Computational fluid dynamics simulations using the Galerkin finite element method were employed to analyze temperature and concentration distributions, fluid flow, melting zone of PCM nanocapsules, Nusselt number, Sherwood number, entropy generation, and thermal performance. The numerical analysis considers a range of dimensionless parameters, including Rayleigh number (Ra=103−105), Lewis number (Le=0.1−10), buoyancy ratio (Nz=1−5), nanoparticle concentration (ϕ=0.01−0.035), fusion temperature (ϴf=0.1−0.9), Stefan number (Ste=0.1−0.9), Hartmann number (Ha=0−50), magnetic field inclination angle (γ=0°−90°), and Frank-Kamenetskii number (FK=0−2.5). Results show that increasing Ra enhances the average Nusselt number (Nuav) by up to 156.1 % and the average Sherwood number (Shav) by up to 104.5 %, while increasing the total entropy generation by up to 13,155 %. Increasing FK reduces Nuav by up to 42.2 % but increases Shav by up to 13.1 %. The Lewis number and buoyancy ratio significantly influence the hydrothermal performance, with Nuav exhibiting non-monotonic behavior and Shav increasing by up to 240.9 % as Le increases. The nanoparticle concentration enhances Nuav by up to 49.7 %. Interestingly, the magnetic field effects are less pronounced than in previous studies, with Ha having a minor impact on Nuav and Shav. These findings have significant implications for the design and optimization of evacuated tube solar collectors and other thermal energy storage systems, potentially leading to improved efficiency and performance in real-world applications.

Cooling of highly concentrated photovoltaic cells with confined jet impingement by introducing channel configurations

Appropriate cooling techniques are required to be integrated into highly concentrated photovoltaic cells to maintain the surface of the photovoltaic cell at a uniform temperature. This study focuses on cooling photovoltaic cells with confined jet impingement to reduce non-uniform temperature distribution and thermal and bending stresses to avoid hotspots and current mismatching problems, thereby improving the cell electrical efficiency. Channels are formed in an aluminium heat sink on the backside of solar cell layers such that the coolant strikes the heat sink surface at the centre and exits at the four corners of the module. Different designs of confined jet channel configurations are studied. The effect of the coolant mass flow rate on the hydrothermal performance of the concentrated photovoltaic thermal (CPV-T) system is examined for all channel configurations. The electrothermal performance of the CPV-T system is at its maximum with a quadrant mini-channel with a single inlet. The net electrical power generated by the PV cell is at its maximum of 30.5 W for a mass flow rate of 50 g/min with this channel configuration. Further, the pressure loss is minimal at 163 Pa at 25 g/min, and the temperature uniformity is also maximum, with a temperature difference over the cell surface of 6.3 °C at 50 g/min. The present study will be useful in the thermal management of highly concentrated photovoltaic thermal systems and high-temperature applications.

Effects of extended pin fins on the hydrothermal performance of double pipe heat exchanger

Double pipe heat exchangers (DPHEs) are crucial for effective heat transfer between two fluids in industrial processes, enhancing energy recovery and optimizing thermal performance. This study aims to enhance the efficiency of DPHEs by incorporating extended pin fins. DPHEs are vital in industrial applications for their efficient heat transfer, but optimizing their performance remains challenging. Extended pin fins, which are minor protrusions added to the heat exchanger’s surface, increase the surface area for heat transfer. A numerical study on DPHEs with pin fins of varying length ratios (R=1, 2, 3, and 4) is conducted, validating our model by comparing results with prior experimental data. Parameters such as Nusselt number (Nu), friction factor, thermal–hydraulic performance factor (TPF), and exergy efficiency across Reynolds numbers from 4400 to 9400 are calculated. The results indicate that pin fins significantly enhance heat transfer. The Nu increases by 163 %-242 % for different length ratios, while the friction factor decreases, showing reductions of 161 %-290 %. Exergy efficiency improves by 216 % with an R=4 design compared to a standard DTHE, and the TPF increases by 152 % with the R=4 configuration. These findings demonstrate the substantial benefits of using extended pin fins in improving the thermal performance of DPHEs.

Influence of pin fins and channel geometry on the hydrothermal performance of hexagonal mini-channel heat sink for cooling cylindrical batteries

This study numerically and experimentally examined the effects of pin fin configuration and channel geometry on the performance of a hexagonal mini-channel heat sink (HMCHS) to cool cylindrical lithium-ion battery cells. Various configurations of HMCHS with circular pin fins are studied, including circular fins centrally positioned within flat channels, circular fins positioned within grooved channels, circular fins situated within hybrid channels transitioning between wavy and straight channels and circular fins placed within hybrid channels that incorporate secondary flow channels between the primary flow channels. This numerical study utilized the finite volume method to investigate the laminar water flow at Reynolds numbers below 800. Findings showed that the HMCHS exhibited superior thermal performance compared with the conventional cylindrical mini-channel heat sink design. Moreover, the incorporation of pin fins into the HMCHS design was more effective in enhancing the Nusselt number than simply increasing the Reynolds number across various configurations. Meanwhile, the hybrid channel design with secondary channels, combined with the addition of pin fins, achieved the optimal overall performance of the HMCHS, resulting in the highest performance index of 1.88.

Investigate the influence of dimple distribution around the circumference of a pipe on the hydrothermal performance of dimpled tubes

Investigate the influence of dimple distribution around the circumference of a pipe on the hydrothermal performance of dimpled tubes

Proposing a New Egg-Shaped Profile to Further Enhance the Hydrothermal Performance of Extended Dimple Tubes in Turbulent Flows

Proposing a New Egg-Shaped Profile to Further Enhance the Hydrothermal Performance of Extended Dimple Tubes in Turbulent Flows

Numerical analysis of enhanced heat transfer and nanofluid flow mechanisms in fan groove and pyramid truss microchannels

A combined groove and truss structure is designed for rectangular microchannel heat sinks with 4 % Al2O3 nanofluid as the working fluid to address the heat dissipation requirements of high heat flux density electronic devices. The effects of fan shape, elliptical, waterdrop, rectangular, trapezoidal and triangular grooves on the heat transfer characteristics and mechanical properties of microchannels are investigated. The fan-shaped groove microchannels with the best overall heat transfer performance and excellent mechanical properties. The stress of the fan-shaped grooved truss microchannel is reduced by 76.41 % compared to the smooth microchannel. Three structural parameters were investigated, including the length of the truss in the spreading direction (Lx), the ratio of truss flow downstream length to upstream length (e) and truss rod diameter (d). The performance of the microchannels is reflected by the integrated heat transfer factor and the field coordination number. The individual structural parameters were analysed in a single-factor comparison. The microchannels exhibited the best hydrothermal performance in the Reynolds number range of 500 ∼ 1300 at Lx = 0.8 mm, e = 3, d = 0.2 mm. When the Reynolds number is 900, the microchannel with the optimal parameter combination exhibits a remarkable enhancement of 234 % in the Nusselt number and an 80 % increase in the integrated heat transfer factor compared to the rectangular microchannel.

Numerical analysis of hydrothermal performance and entropy generation in an active cooling system: A case study with NEPCM, double-diffusive mixed-convection and MHD

Magnetohydrodynamic and entropy generation of double-diffusive mixed convection in a curvilinear cavity filled with nano-enhanced phase change material and a rotating cylinder has been studied in this paper. Three heat sources have been considered and a range of different variables such as Reynolds number (10 ≤ Re ≤ 100), Richardson number (0.1≤ Ri ≤ 10), Hartmann number (0≤ Ha ≤50) Lewis number (0.1≤ Le ≤ 0.9), bouncy ratio (1≤ Nz ≤ 5), fusion temperature (0.1≤ θf ≤0.9) and Stephan number (0.1≤ Ste ≤0.9). These variables have been numerically solved by applying the Finite Element Method. The main results indicated that heat transfer, mass transfer and heat capacity are hugely increased with the increase of the Re, Ri and volume concentration while decreasing with the increase of the Ha number and entropy generation. Furthermore, the melting/solidification region is hugely influenced by the fusion temperature while this variable has a negligible influence on streams, heat transfer and mass transfer. Furthermore, the value of the average Nusselt number and average Sherwood number has increased by 328 % and 258 % respectively by increasing the Reynolds number from 10 to 100. Also, these two numbers have decreased by 61 % and 54 % respectively by increasing the Hartmann number from 0 to 20.

A novel case of honeycomb shaped pin fin heat sink: CFD-data driven machine learning models for thermal performance prediction

This research explores a useful thermal engineering application utilizing novel honeycomb-shaped pin fins heat sink (PFHS). 3D incompressible flow and heat transfer are examined using standard k-ԑ turbulence model for Reynolds numbers (Re) ranging from 8547 to 21367. Using the PFHS with 1.5 mm side length and pitch arrangement of (S =25 × 25), the Nusselt Number (Nu) increased by 171 % at a Re of 21367. Furthermore, Cu-Diamond composite material raises Hydrothermal performance factor (HTPF) to 3.304. At a Re of 8547, honeycomb heat sink has 200 % greater HTPF than the baseline. Predictive modeling of HTPF, Nu, and pressure drop (ΔP) was done using Artificial Neural Network (ANN), Multiple Linear Regression (MLR), Extreme Gradient Boosting Regression (XGBR), and Light Gradient Boosting Machine Regression (LGBMR). The four models with the highest R2 and lowest MRE on the test dataset performed best. Both models were implemented using Keras and Sklearn. XGBR and MLR have superior HTPF prediction accuracy (R2test = 0.977, MRE (%) = 1.1 and 0.924, MRE (%) = 2.1). XGBR and MLR predicted the Nu well with R2test values of 0.979 and MRE percentages of 1.9 and 3.9. R2test of 0.999 and MRE (%) of 0.3 indicate that XGBR predicts pressure reduction.

Systematic design of tree-like branching network microchannel heat sinks for enhanced heat transfer with nanofluids

Branched or tree-shaped networks of microchannels are often preferred heatsink designs for microelectronic cooling due to their ability to offer a substantially large surface area-to-volume ratio. Designing an optimized tree-shaped heatsink in terms of hydrothermal performance poses challenges due to the intricate geometry and small-scale fluid–structure interactions involved, making prototyping challenging. We propose a systematically designed microchannel network heat exchanger inspired by tree branching patterns, aiming for ease in rapid prototyping and improved flow distributions offering enhanced thermal performance. Starting from a simpler geometrical consideration, we systematically improve the design by introducing a pin fin at the junction for improved flow distribution and then by imparting a converging angle in the channel for enhanced thermal performance. Additionally, we conduct an entropy generation analysis to examine the thermal performance of various nanofluid concentrations within the proposed device and witness significant thermal performance improvement that can benefit the thermal management of microelectronic components and other cooling applications.

Numerical study of arrowhead, hexagonal, and concave shaped- elliptical perforated plate fin heatsinks to improve the hydrothermal performance factor

This study explores the comparison of plate fin heatsinks to address the escalating challenges and the growing demand for industrial cooling. Plate fin heatsinks may replace plane (baseline) heatsinks to improve heat transmission while retaining volume. The three novel shape designs: arrowhead fin, hexagonal fin, and concave fin are introduced which are missing in existing literature. The simulation is conducted for Reynolds number (Re) ranging from 13049 to 52195. Elliptical perforated arrowhead, hexagonal, and concave heatsinks have 16.06 %, 16.64 %, and 17.36 % lower volumes than solid arrowhead, hexagonal, and concave heatsinks. The Nusselt number improved by 65.47 %, 69.87 %, and 37.71 % respectively for elliptical perforated arrowhead fin, elliptical perforated hexagonal fin, and elliptical perforated concave fin compared to the rectangular plate fin at Re = 52915. The Nusselt number also enhanced by 23.22 %, 17.91 %, and 8.02 % for the solid arrowhead fin, solid hexagonal fin, and solid concave fin respectively compared to the baseline case at Re = 52195. The maximum HTPF is 1.23 and 1.72 for solid arrowhead plate fin and elliptical perforated hexagonal plate fin respectively. The result of this novel shaped heatsink is promising and can be used as a substitute of traditional plane fin for relevant industrial applications in future.

The Hydrothermal Performance Investigation of Gasketed Plate Heat Exchangers Using Taguchi, ANOVA, and GRA Methods

The Hydrothermal Performance Investigation of Gasketed Plate Heat Exchangers Using Taguchi, ANOVA, and GRA Methods

Numerical investigation of free convection inside square wavy enclosure using response surface methodology

AbstractFree convection is commonly applied in various engineering fields such as solar energy, electronic devices, nuclear energy, and heat exchangers. A computational simulation was used to analyze the natural heat transfer through convection in a wavy cavity with squared shape that was filled with tap water and saturated metal foam to assess the influence of hump configuration (square, triangle, circular, down semicircular, and up semicircular) and magnetic fields (magnetohydrodynamics) on heat transfer rate. The bottom wavy wall of the enclosure exhibits a high temperature (Th), whereas the top and side walls maintain a low temperature (Tc). The present paper will examine how the bottom wall hump number (N), aspect ratio (L), geometry inclination angle (θ), Hartman number (Ha), magnetic field intensity inclination angle (ɤ) affects the heat transfer rate at various Rayleigh numbers. When the circular hump design is used with specific parameters, including ɛ = 0.85, L = 1.25, N = 4, Tc = 0°C, θ = 0°, Ha = 600 and ɤ = 45°, for different Ra values, it leads to increased heat transfer and notable improvements in heat transfer enhancement (ɸ) and energy enhancement (e). The enhancements were measured at 2.5 times for heat transfer enhancement and 8.9 times for energy enhancement. Moreover, the ideal case of the current study had Ha = 600, L = 1.25, Ra = 30 × 103, and θ = 0° compared to the baseline case. Simulations were accomplished using CFD. The results demonstrate that the primary goal of the research was achieved by optimizing the design, leading to a significant improvement in hydrothermal performance for both ɸ = 2.5 and e = 8.9.

Experimental and numerical investigation on fluid flow and heat transfer behaviour of foam cladded pin fin heat sink

As technology advances, there is a growing demand for more efficient cooling solutions in electronics. Open-cell metal foams offer a unique solution, combining the strength of metals with the characteristics of foams, including being lightweight and having a high heat transfer area-to-volume ratio. Fully covering heatsinks with porous materials results in high pressure drop values, which is undesirable for electronics cooling. This study proposes a novel design that incorporates cladded aluminum foams on the pin fins within a heatsink. The hydrothermal performance of the proposed design is experimentally and numerically investigated. The results indicate that increasing the cladding thickness enhances heat transfer performance while increasing the pressure drop. For a heatsink with a pin fin diameter of 5 mm at the Reynolds number of 1121, the foam thickness of 5 mm depicts 46.5 % higher hydrothermal performance compared to a pin fin heatsink without porous while a fully porous covered heatsink depicts 38.9 % higher hydrothermal performance.

Hydrothermal performance of a heat sink using Plate-fins: Experimental and numerical investigations

The development of electronic devices is accompanied by the generation of significant heat. A novel plate-fins design with various orientation angles of 30°, 35°, 37.5°, 40° and 45° was studied. The plate-fins design aims to boost the performance by increasing the surface area and redirecting airflow towards the heat sink plate. The experimental results obtained by this work were employed to validate the numerical results for pin-fins heat sink. A three-dimensional computational domain was investigated using ANSYS Fluent 19.1. The air flow was turbulent and modelled using k-ω turbulent flow. The plate-fins with an orientation angle of 37.5ᴼ exhibit the optimum hydrothermal performance among other configurations. Equally, several optimisation parameters including the number of rows, the diameter and thickness of the pins and the width of the plate-fins were investigated. It was observed that the heat sink with two rows of plate-fins outperformed other designs. This configuration resulted in a significant reduction of 2 % in hot spot temperature and a notable reduction of 60.8 % in pressure drop.

Hydrothermal performance and irreversibility production of distilled H2O flowing in outwardly-corrugated converging pipes

The study of performance parameters that characterize the convective heat transfer performance (CHTP) and entropy production rates (EPR) of fluids is of great importance in science and engineering due to its widespread applications in the design of new thermal devices. This study considers the turbulent CHTP and EPR of distilled H 2 O flowing in outwardly-corrugated converging pipes (OCCPs) and investigates the influence of the diameter ratio DR ( 1 ≤ DR ≤ 2 ) on the behavior of performance parameters against the Reynolds numbers (Re) within the range ( 5.0 × 10 3 ≤ Re ≤ 5.0 × 10 4 ). The governing equations and boundary conditions are solved with the use of SST k − ω turbulence model. The considered OCCP is designed such that its average diameter is 0.03m while its normalized length is 26.6. It is obtained that increasing DR enhances the average Nusselt number (Nu), Poiseuille number (fRe), and EPR whereas the reverse is the case for thermal effective number ( I G ), Bejan number (Be), and performance evaluation criterion (PEC). At Re = 2.0 × 10 4 in OCCPs of DR = 1.00, 1.25, 1.50, 1.75, and 2.00, EPR is increased by factors 0.88, 1.42, 2.64, 4.84, and 9.61; fRe is improved by factors 3.39, 8.54, 16.27, 27.74, and 49.22; and Nu is enhanced by factors 1.28, 1.31, 1.34, 1.37, and 1.43, respectively. The enhancement is attributed to the flow acceleration, vortices production, and high mixing rate of the hot fluid near the wall with the cold fluid at the core fluid zone. Finally, and among other things it is revealed that the OCCPs of DR = 1.00, 1.25, and 1.50 are advantageous ( I G > 1 ) over the straight tube within the range 5 × 10 3 ≤ Re < 2.25 × 10 4 .

Effects of magnetic fields and nanoparticle concentration on hydro-thermal performance of a surface enhanced microchannel

This article numerically investigates fluid flow and heat transfer in plain wall (PWMC) and oblique fin (OFMC) microchannels under varying magnetic fields using water- Al2O3 nanofluid as a working fluid. Effects of magnetic flux (Hartmann number, Ha = 0–30), fluid velocity (Reynolds number, Re = 100–500), and nanoparticle volume fraction (ϕ = 0%–2%) on the overall thermo-fluid performance are analyzed. Magnetic fields can significantly improve the heat transfer in OFMC in a higher rate compared to the PWMC. Also, there is a less increment on the pressure drop in the OFMC in comparison to PWMC. In addition, individual, as well as combined effect of Joule and viscous heating on the thermo-fluid performance is investigated. Due to the combined effect of Joule and viscous heating, the Performance Evaluation Criterion (PEC) in OFMC can be improved by 21%. However, the PEC in OFMC can be enhanced by 55% without considering the combined effect. The detailed characteristics flow and heat transfer are also studied by analyzing the velocity contours, isotherms, streamlines, friction factors, and Nusselt numbers. The present study concludes the importance of consideration of Joule and viscous heating for an accurate modeling, where the viscous heating plays the dominant role. The present findings can be instrumental in enhancing the performance of micro heat sinks to optimize hydrothermal performance in high powered motors, nuclear fusion reactors etc., where magnetic field is present.

Experimental investigation of the performance attributes of a double pipe heat exchanger equipped with baffles of conventional or flower layouts

In industrial heat management, the design of baffles within heat exchangers is crucial. They guide fluid flow and enhance turbulence, optimizing heat transfer. Yet, their configuration must be carefully considered to balance thermal efficiency with energy expenditure and pressure management. This research conducts practical tests on the hydrothermal attributes of a counter-flow double-pipe heat exchanger. It evaluates two baffle layouts: segmental and flower, considering baffle cut-off ratio (16.7 %≤δ ≤ 50 %), pitch ratio (8.3 %≤λ ≤ 22.2 %), flower-design relative angle (30°≤γ ≤ 90°), and operating conditions of annulus-side (2660 ≤ Rean ≤ 13110, 5.21 ≤ Pran ≤ 7.48). The findings assure that installing the baffles results in notable increases in both Nu¯an and fan. Besides, lowering baffle cut-off and pitch ratios, and increasing the relative angle of flower baffles lead to additional increases. Moreover, raising the annulus-fluid temperature reduces Nu¯an with a negligible effect on fan. Increasing Rean leads to a reduced fan and greater Nu¯an. Compared with no baffles, the maximum recorded increases in the Nu¯an and fan are 147.4 % and 60.2 %, respectively, realized by incorporating flower layout. On average, the flower baffles boost the Nu¯an by 20.8 % more than those using conventional baffles, with an average increase of 4.3 % in the fan. To judge the benefit of utilizing baffles, the Hydrothermal Performance Index (HTPI) is calculated, and its highest value is recorded as 2.23, attained by running the annular pipe at the lowest flow rate and temperature, with inserting flower baffles (δ = 16.7 %, λ = 8.3 %, γ = 90°). Finally, correlations for Nu¯an, HTPI, and fan prediction are suggested.