Characteristics Of Heat Sink Research Articles

Performance analysis on heat transfer characteristics of heat SINK with baffles attachment

The performance analysis of baffle implanted Plate-Fin Heat sink (PFHS) is considered in this analysis, which provides physical understanding of heat transfer characteristics. The baffles are made up of copper strip which act as turbulator, placed in between PFHS channel to induce turbulence in cooling medium. The study variables are heat intensity and cooling air velocity. Thermal characteristics of Baffles implanted PFHS are compared with plain PFHS by experimental and simulation methods. The experimental result shows that about 12.9% higher heat transfer in baffles attached heat sink than plain heat sink. The effect of baffle deflector on PFHS is studied and recommended to vary dimensional changes to improve heat transfer. The experimental and simulation results discover that baffles attached PFHS has more heat transfer than plain PFHS. The turbulator attachment increases pressure drop and Reynolds number, leads to reduced thermal resistance and increased heat transfer.

Influence of fin height on heat transfer and fluid flow characteristics of rectangular microchannel heat sink

Heat transfer and fluid flow behavior have been studied numerically in rectangular parallel microchannel heat sinks with varying fin height. Seven different cases have been considered by varying the fin heights from 0.4 to 1.0 mm. Completely closed heat sink (conventional configuration) of 1.0 mm fin height is one of the cases while remaining six heat sink configurations hold open space between fin top surfaces and cover wall. Three dimensional (3D) numerical simulations were carried out for the range of operating parameters where heat flux varied from 100 to 500 kW/m2 and Reynolds number from 100 to 400. Single phase liquid water flows as coolant in the heat sink to remove heat. Optimization of fin height has been done to achieve maximum heat transfer rate and overall thermal performance of the heat sink. It has been observed that proposed design of the heat sinks facilitate distinct heat dissipation capacity and fluid flow characteristics. Predicted results i.e. temperature distribution, heat transfer coefficient pressure drop and velocity profile clearly reveal that heat transfer increases with increasing fin height however, heat sinks of considerably shorter fin heights (0.4 – 0.6 mm) have less potential to transfer heat. Pressure drop also increases with fin height because flow obstruction rises. It has been found that heat sink of fin height 0.8 mm exhibits maximum heat transfer which is even higher than fin heights of 0.9 mm and 1.0 mm (completely closed heat sink). Net convective surface area and typical flow behavior caused by available open space have been identified as major reasons to influence the overall thermal performance of the proposed heat sinks.

Heat transfer and flow characteristics of sinusoidal wavy plate fin heat sink with and without crosscut flow control

This article presents new experimental data on the influence of phase shift, air velocity, heat sink base surface temperature on heat transfer coefficient, and pressure drop of airflow through sinusoidal wavy plate fin heat sinks (SW-PFHS) and crosscut sinusoidal wavy plate fin heat sinks (CCSW-PFHS). Sinusoidal wavy plate fins with a wave length of 18.68 mm, amplitude of 2.0 mm, and phase shift of 0°, 90°, and 180° are used. For CCSW-PFHS, the sinusoidal wavy plate fin is cut transversely at crests and troughs with a 2 mm length. The test runs are performed at an air velocity ranging between 1 and 5 m/s and a heat sink base surface temperature of 70 °C, 90 °C, and 110 °C. The results show that the higher phase shift and air velocity lead to the enhancement of the heat transfer coefficient and pressure drop. Conversely, the heat sink base surface temperature has a slight effect on the heat transfer coefficient and pressure drop. The heat transfer coefficient of SW-PFHS is enhanced when increasing the phase shift compared with a phase shift of 0°. Under the same phase shift, the Nusselt number of CCSW-PFHS is higher than that of SW-PFHS by about 5.9–19.1%. The CCSW-PFHS with a phase shift of 180° yields the highest TPF.

Experimental study of cooling performance of water-based alumina nanofluid in a minichannel heat sink with MEPCM layer embedded in its ceiling

This work investigates experimentally the cooling performance of Al2O3/water nanofluid with 8 wt% concentration flowing through a minichannel heat sink with a MEPCM layer in its ceiling. The hydrothermal characteristics of the nanofluid-cooled minichannel heat sink are analyzed and the dimensionless wall temperature distribution, Nusselt number, heat transfer effectiveness, coefficient of performance, figure of merit, and wall temperature thermal resistance are assessed. The measured results show that the dispersion of alumina nanoparticles inside pure water declines the wall temperature and consequently enhances the heat transfer effect and Nusselt number augments. The maximum values of average heat transfer effectiveness and FOM at the inlet of the MCHS are achieved 1.4 and 1.27 by flowing nanofluid with 8 wt% nanoparticle concentration and Re = 1549, respectively. The results revealed that embedding MEPCM layer in the ceiling of the MCHS has little influence on the cooling performance of Al2O3/water nanofluid in the minichannel heat sink.

Parametric study on thermal and hydraulic characteristics of inter-connected parallel and counter flow mini-channel heat sink

The paper presents three-dimensional numerical investigation of fluid flow and heat transfer performance of parallel and counter flow mini-channel heat sink where cross flow between parallel channels was enabled with inter-connectors. The aspect ratio (height to width) and hydraulic diameter of the investigated mini-channel were 0.33 and 750 µm respectively. In this study, water was employed as the coolant, and the flow was in the single-phase regime under laminar flow condition at Reynolds numbers ranging from 150 to 1044. A constant heat flux of 20 W/cm2 was applied at the bottom surface of the heat sink. To analyze the effect of cross flow on the overall thermo-hydraulic performance of the mini-channel heat sink, five different widths of the inter-connector were studied. The non-dimensional pressure, velocity, temperature, friction factor, overall Nusselt number (Nu), and thermal resistance were calculated to evaluate the overall performance of the inter-connected mini-channel heat sink. Finally, the performance of the inter-connected mini channel was compared with the conventional mini-channel by calculating the performance evaluation criteria (PEC). The results show that the inter-connector has a significantly larger effect on the counter flow mini-channel heat sink compared with the parallel flow mini-channel. For the counter flow mini-channel heat sink, Nu was enhanced by a maximum of 36% at Re = 1044 as compared to the conventional parallel flow mini-channel while a maximum of 31.13% reduction in friction factor was recorded at Re = 150. The PEC of the counter flow mini-channel went up to 1.33, and its value shows an increasing trend with as Reynolds number increases.

Robust optimization for the preliminary design of solar organic Rankine cycle (ORC) systems

Organic Rankine cycle (ORC) powered by solar energy is a viable and effective option for a high efficiency conversion of solar thermal energy into electricity at a distributed scale but recurring fluctuations of the thermal energy often force solar-based ORC systems to operate at part-load conditions.With the aim of including the effects of the expected variations of the heat source and heat sink characteristics, even during the design phase, a novel optimization approach for the preliminary design of ORC systems integrated with concentrating solar collectors is presented and analysed. In particular, the minimization of the expected levelized cost of energy (LCOE) of the ORC unit is chosen as an objective function, while the generation of various scenarios is proposed to face the expected fluctuations on the heat source mass flow rate and temperature and cooling inlet temperature. In this way, the expected off-design performances are involved during the design step, giving robustness to the optimal design solution.The proposed methodology is tested by referring to the solar ORC system configuration of the Ottana solar facility. Firstly, the effect of a robust optimization on the preliminary ORC design is investigated by considering an increased number of scenarios for each of the three most significant ORC input variables (heat source mass flow rate and temperature and ambient temperature). Subsequently, the proposed methodology was applied to an ORC design case by considering a concurrent variation of the three variables and three different working fluids.The results of this study demonstrate that a multi-scenario approach drives towards an ORC configuration with lower performance under design conditions, but less sensitive to the variation of the main inputs. Less expensive solutions are therefore achieved by the proposed methodology, but the annual energy production obtained is comparable with those achieved by adopting a single scenario approach, with a consequent reduction of the LCOE.

Numerical and experimental investigations on heat transfer and pressure drop characteristics of Al2O3-TiO2 hybrid nanofluid in minichannel heat sink with different mixture ratio

Heat transfer and pressure drop characteristics of minichannel heat sink are analysed experimentally and numerically (two-phase mixture model) by using hybrid nanofluids. Minichannel heat sink consists of 9 parallel rectangular shaped minichannels having depth of 3 mm and width of 1 mm. The Al2O3–TiO2 hybrid nanofluid with nanoparticles volume concentration of 0.1% with different nanoparticle mixture ratios (10:0 to 0:10) has been used as coolant to analyze the effect of volume flow rate (0.1 to 0.5 LPM), Reynolds number (90 < Re < 500) and inlet temperature (20 to 40 °C). Two-phase mixture model has good agreement with the experiment data as compared to single phase (homogenous model) approach. The developing length slightly increases by using hybrid nanofluid. A maximum enhancement of 8.5% (numerical) and 12.8% (experimental) has been observed for convective heat transfer coefficient with Al2O3 (10:0) hybrid nanofluid. Pressure drop and friction factor increase with decrease in temperature and increase in volume fraction of nanoparticles. Both numerical and experimental results reveal that the hybrid nanofluids yield no synergetic effect in heat transfer while mixing dissimilar nanoparticles with similar shape and size.

Numerical analysis of the heat transfer and fluid flow characteristics of a nanofluid-cooled micropin-fin heat sink using the Eulerian-Lagrangian approach

In the present study, the thermofluid characteristics of a water and nanofluid-cooled micropin-fin heat sink have been evaluated by implementing a two-phase Eulerian-Lagrangian model. The nanofluid consisted of an aqueous suspension of the spherical-shaped alumina nanoparticles with the particle volume fraction (φ) ranging from 0.25% to 1%. The analysis has been performed by considering a heat sink comprising the staggered arrangement of 72 micropin-fins of the circular cross-section without tip clearance. A constant heat flux of 300 kW/m2 was subjected at the base of the heat sink, whilst the utilised pressure drop (∆P) across the heat sink was limited to ∆P<3000Pa. Heat transfer and fluid flow parameters were evaluated in terms of the local heat transfer coefficient, the enhancement ratio of the average convective heat transfer coefficient, thermal resistance and volume flow rate through the heat sink. Additionally, the temperature contours and flow streamlines across the heat sink elaborated the temperature distribution and flow attributes. Results indicated that under identical ∆P conditions, replacing water coolants with nanofluids optimised the thermal performance of the heat sink with a perceptible margin at the higher particle loadings. At the optimal pressure drop and particle concentration, nanoparticle dispersion into the hosting fluid demonstrated a maximum of 16% enhancement in the average heat transfer coefficient.

A Study on Cooling Characteristics of the LED Lamp Heat Sink for Automobile by Forced Convection

A Study on Cooling Characteristics of the LED Lamp Heat Sink for Automobile by Forced Convection

Numerical simulation of a photovoltaic thermoelectric hybrid power generation system

In this study, three dimensional numerical models for a PV module and a TEG device are developed. The objective is to investigate the performance of hybrid PV + TEG power generation systems composed of thermoelectric generators attached to the backside of a PV module. The proposed numerical model ignores the inner structural complexities and considers the device as a homogeneous medium. The electric power output is modeled as an internal energy sink. The governing energy equations are solved by finite volume method. User defined functions are developed to account for the electrical behavior of PV and TEG. Results show that the hybrid system can generate more power than the simple PV in certain environmental conditions. However, the increase is marginal due to the insufficient temperature difference for the TEG device. Also, the presence of TEG may have undesirable effects on cooling of PV module. Simulations are performed for different number of TEG modules and also various optical concentration ratios. It is revealed that the maximum power generation occurs at a certain concentration ratio which depends on the heat sink characteristics.

Experimental and Numerical Study Effect of Using Nanofluids in Perforated Plate Fin Heat Sink for Electronics Cooling

An experimental and numerical investigation of the effect of using two types of nanofluids with suspending of (Al2O3 and CuO) nanoparticles in deionized water with a volume fraction of (0.1% vol.), in addition to use three types of fin plate configurations of (smooth, perforated, and dimple plate) to study the heat transfer enhancement characteristics of commercial fin plate heat sink for cooling computer processing unit. All experimental tests under simulated conditions by using heat flux heater element with input power range of (5, 16, 35, 70, and 100 W). The experimental parameters calculated are such as water and nanofluid as coolant with Reynolds number of (7000, 8000, 9400 and 11300); the air is blown in the inlet duct across the heat sink with Reynolds number of (10500, 12300, 14200 and 16000). The distance fin-to-fin is kept constant at (2.00 mm), and the channel employed in this work has a square cross-section of (7 cm) inside. It was observed that the average effectiveness and Nusselt number of the nanofluids are higher compared with those of using conventional liquid cooling systems. However, the perforated fin plate showed higher air heat dissipation than the other configuration plate fin employed in this study. The experimental results were supported by numerical results which gave a good indication to heat transfer enhancement in studied ranges.&#x0D;

A comparative study of experimental flow boiling heat transfer and pressure drop characteristics in porous-wall microchannel heat sink

In this work, we proposed a porous-wall (PW) microchannel heat sink, in which micro pin fin arrays were fabricated on sidewalls of rectangular microchannels by MEMS (Microelectrical Mechanical System) technique. High speed flow visualizations were performed simultaneously with heat transfer and pressure drop measurements to investigate the flow boiling characteristics of PW microchannel heat sink. Conventional rectangular (Rec) microchannel heat sink was also explored together as a comparison. Experiments were carried out with pure acetone liquid at inlet temperature of 30 °C, mass flux from 255 kg/(m2·s) to 843 kg/(m2·s), heat flux from 4 W/cm2 to 110 W/cm2 and the maximum vapor quality at the outlet of the channel was 0.88. Experimental results demonstrated that the PW microchannels reduce wall superheat of onset of nucleate boiling (ONB) and improve critical heat flux (CHF) compared to the Rec microchannels. Moreover, the PW microchannels show significant heat transfer enhancement, pressure drop reduction and mitigation of two-phase flow instability. The porous walls provide numerous nucleation sites and the intensive pin fins arrangements introduce significant wicking effect to maintain the liquid rewetting, which contribute to the above notable flow boiling enhancement.

Influence of chevron fin interruption on thermo-fluidic transport characteristics of nanofluid-cooled electronic heat sink

In the current study, the effects of different interruptions of fin on the transport characteristics of a nanofluid-cooled electronic heat sink with chevron shape are analyzed numerically. Seven interruptions of fin are explored and compared with the integral case. Water and water-based nanofluid with Al2O3 nanoparticle at volume fractions of 0.5% and 1.0% are tested as the coolant in laminar flow regime (Reynolds number less than 900). All coolants are also tested experimentally in the heat sink equipped with the integral fin, and the achieved data are used to verify the numerical approach. The obtained results disclose that the use of interrupted fins leads to a superior heat transfer process due to a decrease in the fin surface temperature and a rise in the outlet coolant temperature. Simultaneously, it causes considerable decrements in the pressure drop which is because of an increase in the fin porosity of the heat sink. The percentage variation in heat transfer coefficient for the interrupted fins as compared with the integral case is in the range of –9.3% to +43.6% while the percentage variation in the pressure drop is in the range of –43.5% to –92.7%. Among all interrupted models, the one reaching the performance index of 3.09 at the Reynolds number of 300 is the best. Furthermore, the water-based nanofluid shows a better thermal performance and a certain penalty in the pressure drop compared to water. The water-based nanofluid can enhance the performance index of the heat sink by an average of 14.7% and 28.3%, which correspond to 0.5% and 1.0% volume fractions of Al2O3 nanoparticle, respectively. Finally, it can be concluded that the compound technique used for the chevron fin (interruption + nanofluid) can be a good choice in practical applications to improve the overall performance of electronic heat sinks.

Experimental investigation on heat transfer characteristics of an oblique finned microchannel heat sink with different channel cross sections

The heat transfer and flow characteristics of oblique finned microchannel heat sink with a dimension of 48 × 80 mm2 were investigated experimentally with different channel cross-sections. The three-channel cross sections were namely trapezoidal, square and semi-circle is analyzed by using Al2O3/water nanofluid with 0.25% volume fraction and water as a coolant. The experiments were performed with a constant mass flow rate of 0.1 LPM and varying heat flux ranging from 5.5 to 26.5 kW/m2. The temperature and pressure drop across the inlet and outlet of the microchannel heat sink were measured to obtain heat and flow characteristics. The result shows that trapezoidal cross-section performs better and it provides 8.5 and 10.3% increased heat transfer rate than square and semi-circle cross sections respectively. Similarly, it gives 6.6 and 8.2% increase in friction factor than square and semi-circle respectively. Also, the case with trapezoidal cross-section creates lesser thermal resistance and slightly higher pumping power among the three sections.

Effect of fin shape on the thermal performance of nanofluid-cooled micro pin-fin heat sinks

The study presents the combined effects of using nanofluid and varying fin cross-sectional shape on the heat transfer characteristics of a micro pin-fin heat sink by employing discrete phase model (DPM). Three fins configurations of the square, circular and hexagon cross-section with constant fin diameter and height have been analyzed for the inline arrangement of 17 × 34 fins. Aqueous nanofluid containing spherical shaped particle dispersions of TiO2 has been simulated for the particle concentration and size of 4.31 vol% and 30 nm respectively. Constant heat flux (192 W) boundary condition at the base of heat sink has been considered for the range of Reynolds number 250 ≤ Re ≤ 550. The influence of fin shape on the thermal efficiency of the heat sink has been analyzed by evaluating heat sink base temperature, Nusselt number, convective heat transfer coefficient distribution and temperature contours along the surface of the heat sink. Additionally the velocity streamlines and contours have also displayed to elaborate the fluid flow attributes. Results demonstrate that under identical flow conditions, the nanofluid cooled circular fins displayed most efficient thermal performance followed by the hexagon and square fins. While the water cooled square fins depicted lowest heat transfers characteristics. The best thermal performance of the circular fins is the response of the delayed flow separation along the smooth surface of fins and the subsequent uniform flow distribution along the whole sink. For all the cases, upstream fin rows played a primary contribution in flow distribution and hence thermal characteristics of the heat sink.

Thermal characteristic research of associated power devices based on three-level inverters and power-loss calculation

To reduce the size and improve the power density of three-level inverters, two or more associated power devices are assembled on the same heatsink, which, however, has a great influence on the thermal characteristics of heatsink because of heat accumulation, and is the main cause of thermal faults. The NPC (Neutral Point Clamped) three-level inverter was taken into this paper as a research target and platform. The dynamic power losses of two power devices were calculated firstly according to the working condition and then put into the solid model. Secondly, the thermal characteristics of heatsink with associated power devices on it were analyzed through finite element analysis, and the temperature rise of power devices were studied as well. Finally, the thermal characteristic experiment was conducted on a 1 MW NPC three-level inverter platform, and the results proved the effectiveness of the research method on thermal characteristics of heatsink with associated power devices.

Numerical simulation of heat transfer characteristics of jet impingement with a novel single cone heat sink

Jet cooling is one of the most effective ways for transferring high heat flux, and the shape of the heat sink for jet impingement is the key factor that affects heat transfer. A novel array cone heat sink was proposed in this work, where heat transfer jet impingement enhancement using a single cone heat sink was experimentally investigated first. A numerical simulation method was used to evaluate the thermal characteristics of the novel single cone heat sink, and the reliability analysis was conducted to show that numerical simulation was feasible. The effects of several main parameters of a cone heat sink on average Nusselt number (Nu‾) were analyzed through numerical methods to explore the characteristics of jet flows and heat transfers in a single cone heat sink. These characteristics included the cone angle (A, A=0–70°), cone bottom diameter to nozzle diameter ratio (d1/d, d1/d=1–3), jet height to nozzle diameter ratio (H/d, H/d=3–7), Reynolds number (Re, Re=16,000–32,000) and heat flux density (q, q=60–100W/cm2). Results showed that the cooling effect of fluid impinging on a cone heat sink is superior to that of a conventional flat plate heat sink. A new impact region (transition region) was formed during fluid jet impingement on a single cone heat sink, consequently improving the heat transfer effect. The best cooling effect was observed at the following conditions: A=50°, d1/d=2, and H/d=5. In addition, Nu‾ increased considerably when the Re increased within the range of 16,000–32,000, and a large q was obtained at increased top temperature on the heat source surface at the same jet flow rate.

Heat transfer enhancement in microchannel heat sink using hybrid technique of ribs and secondary channels

The flow and heat transfer characteristics of microchannel heat sink with secondary oblique channels in alternating direction and rectangular ribs (MC-SOCRR) are studied numerically for Reynolds number (Re) ranging from 100 to 500. The effects of secondary channels and ribs on the Nusselt number and friction factor are investigated. A comparative analysis has been conducted to the performance of the proposed design with related geometries such as microchannel with rectangular ribs (MC-RR) and microchannel with secondary oblique channels (MC-SOC). The results emphasized the superiority of overall performance of MC-SOCRR over both MC-RR and MC-SOC. The strategy which pursued by new design is the exploitation of larger flow area which provided by secondary channel to reduce pressure drop caused by ribs. Besides, the existence of the ribs in central portion of the channel is utilized to inject more flow through secondary channels for further enhancement in flow mixing. The effect of three geometrical parameters; relative width of secondary channel (λ) relative rib width (β) and angle of secondary channel (θ) on the convective heat transfer and pressure drop have been investigated. The MC-SOCRR with parameters; λ=0.666, β=0.5 and angle=45° yields the best overall performance with Pf=1.98 at Re=500.

Analysis of the Dependence of the Characteristics of a Biodegradable Composite Heat Sink on the Metal Additive

Analysis of the Dependence of the Characteristics of a Biodegradable Composite Heat Sink on the Metal Additive

Heat Development and Comparison Between the Steady and Pulsating Flows Through Aluminum Foam Heat Sink

Continuous improvements in electronic devices for high-performance computers have led to a need for new and more effective methods of chip cooling. The first purpose of this study was to investigate the heat transfer development and characteristics of aluminum foam heat sink subjected to steady water flow for electronics cooling (Intel core i7 processor). The second purpose was to implement a new type of water flow through the aluminum foam, which is pulsating or oscillating flow in order to achieve more uniform temperature distribution over the electronic surfaces. The aluminum foam heat sink was subjected to a water flow covering the non-Darcy laminar flow regime (297–1353 Reynolds numbers). The bottom side of the heat sink was heated with a heat flux between 8.5 and 13.8 W/cm2. The pulsating flow frequency was ranged from 0.04 to 0.1 Hz. In addition, in order to complement the experimental studies, a numerical model was developed using finite element method and compared with the experimental data. The results revealed that the thermal entry length of the fluid flow through metal foam (porous media) is much smaller than that for laminar internal flow through empty channel. The result also showed that the local surface temperature increases along with increasing the axial flow direction for steady water flow case. On the other hand, for pulsating flow, the local temperature distributions act as a convex profile with the maximum surface temperature at the center of the test section. In addition, it was observed that the pulsating water flow through the aluminum foam heat sink achieves enhancement by 14% in the average Nusselt number and by 73% in temperature uniformity over the surface compared with steady water flow case.