High-Performance Cooling: The Influence of Turbulent Air Inlet Velocity on Triangle Fins for Efficient Heat Transfer

The evaluation of heat transfer from a heat source located beneath a linear triangular fin on a horizontal surface was conducted in an air tunnel, as seen schematically in Figure 1(a). The setup comprises an air tunnel, a heat sink positioned within the test section of the air tunnel, and an electrical heating element attached to the base of the heat sink. The air tunnel walls are located 25 mm from the edges of the heat sink in all directions, except at the outlet, which is 150 mm from the back edge of the sink, and no space between the heat sink bottom and the air tunnel bottom as shown in Figure 1(b). The uniform velocity, U∞, was modified from 2 m/s to 6 m/s in increments of 2 m/s, maintaining a turbulence intensity of 0.5%. The constructed air channels and heat sink mimic fin channels oriented with the incoming flow. A heating element was attached to the base of the heat sink, which was considered thermally insulated to reduce heat losses. The heat flux applied to the lower surface of the heat sink was 10,000 watts/m². The steady-state temperature of the fin surfaces, Ts, was measured at U∞ = 2, 4, and 6 m/s, the last three models with the three-inlet velocity had just one inlet as shown in Figure 1(a), the fourth case has a 2 m/s inlet velocity with three inlets from the front and two sides. The temperature was measured at four separate locations on the fin surface at the same height from the base to evaluate consistency. The study investigated the results of the inlet velocity variations in the first three cases, then compared the best results with the three inlet models with the lowest inlet velocity (2 m/s) to find the optimum design.

1a.jpg

1b.jpg

Figure 1. (a) Air tunnel (enclosure) dimensions from the heat sink, (b) bottom side dimensions

The hydraulic diameter of the channel section is defined by:

$D_h=4 A / P$    (1)

where, A (= sH) represents the channel cross-sectional area, and P (= s + 2H) indicates the wetted perimeter of the channel. The average Nusselt number (Nu) is computed utilizing the average forced convection coefficient (h) and hydraulic diameter (D_h) as follows [16]:

$N_u=h D_h / K_f=Q D_h /\left(A_t\left(T_s-T_{\infty}\right) K_f\right)$    (2)

where, k_f signifies the thermal conductivity of air at the film temperature, A_t represents the total convective heat transfer surface area of the fins, T_s denotes the fin surface temperature, and T∞ indicates the free-stream inlet air temperature. All air properties are evaluated at the film temperature T_f = (T_s + T_∞) / 2, and variations in air properties are deemed unimportant in the numerical simulations due to the small temperature rise.

2.jpg

Figure 2. Heatsink SOLIDWORK model design and dimensions

The fin array analyzed in this research is representative of those employed in the cooling of electronic devices with a fan. The SOLIDWORKS model and fins dimensions are shown in Figure 2. The fins were constructed from aluminum alloy. In the numerical calculations, it was assumed that the thermal conductivity, K = 167 W/mK, and the emissivity ≈ were 0.8. The air temperature at the fin array entrance was 20℃. Reynolds number ranges from 2692 to 6728, signifying a turbulent flow regime. The heatsink model was designed by the SOLIDWORKS software, then imported to the ANSYS fluid, and the dimensions of the heatsink model are illustrated in Figure 2. Researchers examined heat transmission and flow dynamics using three-dimensional flow simulations using ANSYS Fluent CFD. Radiative heat transfer was modeled utilizing the surface-to-surface radiation model from sources [17] for triangular straight fins in natural convection; further details are available in the previous study [18]. The surface-to-surface radiation model evaluates energy exchange between fin surfaces, determined by their dimensions, separation, and orientation, quantified by a geometric quantity known as the view factor. Additionally, it presumes that absorption, emission, or scattering may be disregarded. Consequently, the radiation energy flow from the fin surfaces comprises emitted and reflected energy. The characteristics of the intake air utilized in the simulations were as follows: the inlet air density was treated as an incompressible ideal gas, specific heat capacity (Cp) was 1006.34 J/kgK, viscosity was modeled using Sutherland's law, thermal conductivity (k) was 0.0242 W/mK, and the molecular weight was 28.966 kg/kmol. The turbulent flow was simulated using the realizable k-e model coupled with standard wall functions, and a no-slip boundary condition was applied on the fin surface.

Case modeling and resolution using ANSYS FLUENT 2024 R1. A distinct implicit solver option was used to solve the governing equations. Mass, momentum, and scalar transport governing equations are discretized first, followed by the formulation of an algebraic system of equations. Computational fluid dynamics (CFD) programs often use the finite volume technique, a branch of the finite difference numerical methodology, to compute flows. The fundamentals of finite volume computations will be covered here. The RANS equations were discretized using the k-epsilon turbulence model throughout the instance executions of this project in order to account for flow variations caused by turbulence. In order to describe differential expressions in up air or other higher-order techniques, the equations were discretized using distinct differencing systems. The algebraic equations derived from the integral equations were solved at each cell node. These equations contained terms from the differencing scheme related to turbulence parameters, momentum, and energy [20]. In order to get the value of the scalar attributes, such as temperature, at a certain point in the computational domain, the calculation also has to consider the flow's direction and velocity. One sequential technique that outperforms the linked solver in terms of memory use is the segregated solver, which is used in numerical computation. The SIMPLE method is utilized for the computations in this project. Executed the standard procedure for pressure interpolation and SIMPLE pressure-velocity coupling. As seen in Figure 4, the CFD simulations, which comprised 20,000 iterations, were designed with a residual root-mean-square (RMS) goal value of 10-4 for continuity and 10-5 for the energy equation.

The realizable version of the k-ε turbulence model is the more popular one, which the authors select as a robust, computationally-effective approximation of fully turbulent flows in general, especially the ones relevant in practical engineering applications (e.g., heat sink air cooling applications). Therefore, airflow over triangular-shaped fins of an air tunnel in the current study has a Reynolds number in the range between 2,692 to 6,728, having dominant turbulence in the airflow, without an overpowering high-Re number causing it to exceed high-Re. The k-ε model is a strong weapon, especially when weighed against the typical wall functions to model the mean flow properties, level of turbulence, and heat transfer without significant amounts of computational expenditure. The k-ε model solves two transport equations: k, the transport equation of turbulent kinetic energy; and epsilon, the dissipation equation of kinetic energy. This provides a good compromise between reality in physical terms and numerical stability. The authors used the so-called realizable model, which makes the flows with large recirculation and streamline curvature - that matter in the triangular fin designs with separation region and reattachment zone that have high heat transfer - more accurate. What is more, the k-ε model is highly applicable in ANSYS Fluent using a standard calibration constant set and has a high capacity in addressing forced convection cooling issues. Table 3 shows the essential differences between K-ε, K-ω, and (LES Large Eddy Simulation) models.

In this study, it is a forced convection problem, in which the flow is overall turbulent and steady. The main objective is to comprehend average heat transfer, but not transitional eddy processes. The k-ε model is the best compromise model between realism, numerical stability, and computational time. Other options, such as the SST k-ω, might be slightly more accurate with the wall layers, but more expensive, and LES would be overly expensive at design-level cooling simulations. Therefore, the selection of the authors is consistent with the conventional CFD approach to the turbulent cooling of electronic heat sinks.

4.jpg

Figure 4. Simulation energy equation solution

Table 3. K-ε, K-ω, and (LES Large Eddy Simulation) models' comparison

6.1 Heatsink temperature profile analysis

The researchers study the way temperature reaches different parts of the heat sink and compare the heat released in three heat sink models using air speeds of 2 m/s, 4 m/s, and 6 m/s. The simulations relied on ANSYS software, which is used for computational fluid dynamics (CFD) and thermal analysis. Aluminum is commonly used for making heat sinks because it conducts heat well and has a good price for its performance. All three models are exposed to a steady supply of heat from below, representing what happens in actual heat sinks: the base creates heat that needs to be removed quickly and efficiently to the surrounding world. The heat distribution models and the outlet average temperature of the three simulation models with 2, 4, and 6 m/s inlet velocity are illustrated in Figures 5(A), (B), and (C).

5a.jpg

5b.jpg

5c.jpg

Figure 5. Heatsink temperature distributions, (A) 2 m/s inlet speed, (B) 4 m/s inlet speed, and (C) 6 m/s inlet speed

As seen in Figure 5(A), where the air speed at the inlet is just 2 m/s, the temperature distribution on the heat sink features a greater change in temperature. Air is weaker at the ground, so it does not cool things as much as expected. You can see from the thermal contours (Figure 5(A)) that the heat sinks coupling in this system have temperatures that vary from roughly 67.5℃ to 79.8℃. According to the heat sink fins at the top, the cooling is less efficient, probably because a slow airflow makes it difficult for heat to move away. Very high temperatures are seen at the base, indicating that some heat is being trapped there, which becomes a worry for overheating if this system is used for practical purposes. An increase in air speed (to 4 m/s, in Figure 5(B)) clearly results in a faster transfer of heat from the heat sink to the air. By increasing the air speed to the continental case, the temperature decreased, temperature range between 51–62℃ was recorded at this speed. The greater the air speed is, the faster heat is transferred, simply because more air contacts the surface of the heat sink. The extra air moving helps the heat sink dispose of heat more effectively, mainly from its highest area. The effect is that the temperature is more even throughout the heat sink and less heat forms at the bottom. It is more effective thermally to run the system with an inlet speed of 4 m/s because it produces less heat and takes less effort to cool than when the speed is only 2 m/s.

Among all the settings, the strongest air inlet at 6 m/s (Figure 5(C)) is the best for cooling the object. The range of temperature in this area is lower; it drops from around 41.6℃ to 52.5℃. More efficient heat transfer occurs because increased airflow speed improves the convective heat transfer coefficient. Because of this, the temperature at the base of the heat sink is now much lower than before in conditions when airflow is low. The fins of the heat sink are now colder, and the air temperature is more uniform, which means heat is being spread away efficiently. This setup gives the highest cooling performance for this kind of heat sink under the specific conditions. Fundamental principles of thermal and fluid dynamics are pivotal to the configurations of the observed temperature profiles. Increasing airflow velocity enhances the convective heat transfer coefficient, hence improving heat removal efficiency. Air traveling at 6 m/s conducts heat far more rapidly than air moving at 2 m/s. The acceleration of incoming air and expanded heat exchange area improve convective heat transfer, reducing temperature. Reduced airflow leads to a broader boundary layer, reducing heat transfer efficiency. Elevating airspeed reduces boundary layer thickness, enhancing heat transmission efficiency. Turbulence intensifies at a maximum airflow velocity of 6 m/s, enhancing fluid dynamics and heat dissipation. Aluminum heat sinks conduct heat from the base and disperse it along fins, affecting thermal efficacy. Fin configuration, quantity, and spacing also affect thermal efficacy. Elongating and thinning fins increase surface area for heat transfer but also affect thermoregulation based on air velocity [22].

6.2 Heatsink temperature distribution analysis

Figure 6 shows how the temperature is distributed on a heatsink center along the x-axis at 0.025 meters high from its base for air inlet rates of 2 m/s, 4 m/s, and 6 m/s. The length of the air tunnel in which the heatsink is placed goes from -0.1 to 0.20 meters on the x-axis, while the heatsink area lies within -0.10 and approximately 0.002 m. The graph illustrates how temperature changes as the air moves through the air inlet. As we move the heatsink at varying speeds (2 m/s, 4 m/s, and 6 m/s), we notice that it gets hotter in the middle before the temperature goes down as air leaves it. The area closest to the heat source or the center of the heatsink seems to get the hottest. With increased velocity, there is usually less peak temperature in the heatsink, which means the higher the airflow, the more effectively the heatsink is cooled. A higher velocity causes convection to speed up heat transfer, lowering the heat sink's hottest point compared to low velocities. Near airflow velocity of 2 m/s, a location near the center of the heatsink (about 0.002 m along the x-axis) may attain a temperature of 45℃. The spectrum of potential temperatures diminishes with an increase in velocity. Enhanced air circulation facilitates superior heat dissipation, with air reaching its peak temperature of around 35℃ at a velocity of 4 m/s. At an air speed of 6 m/s, the temperature may attain 30℃. The heatsink appears to be cooled most efficiently by the swiftest airflow. As one progresses laterally from the heatsink along the x-axis, air temperatures decrease, facilitating the transfer of heat from the heatsink to the air within the air tunnel. The majority of heating occurs near the heatsink, with a rapid decline in temperature as the distance from it increases, as seen by the temperature graphs for the three speeds. The heat sink’s core, at 0.00 m, has the highest thermal intensity due to direct solar radiation heating. Heat transfers through convection, and as airspeed increases, efficiency improves.

6.jpg

Figure 6. Heatsink temperature distribution along the x-axis at the heatsink center for the three inlet velocities

Air molecules directly touch the heatsink, removing thermal energy. However, 2 m/s air flow increases boundary layer thickness, reducing heat dissipation efficiency. Accelerated airflow decreases the opposing effect and therefore increases heat transfer. At a velocity of 2 m s^-1, the air flow forms a dense thermal boundary layer and which prevents the heat flow. As the air velocity gets even higher, the thickness of this boundary layer reduces further, and hence a better transfer of heat is achieved from the heatsink to the surrounding air. Heat is transferred into the heatsink, causing a slow reduction of its temperature. At higher air velocities, the convective heat dissipation becomes more efficient. Laminar flow is dominant for low velocities, while turbulent flow allows better mixing of air and thus improved heat transfer. Increased air velocity across the heatsink improves its heat dissipation capacity, reducing thermal resistance [23]. Figure 7 illustrates how the temperature varies near the heatsink outer wall (at a distance of 0.003 m) and along the x-axis, for three inlet velocities of 2 m/s, 4 m/s, and 6 m/s. On the x-axis, the length of the air tunnel and where the heatsink is located runs from -0.1 m to 0.002 m. The maximum recorded temperature of around 27℃ was seen at the heat sink at a velocity of 2 m/s. It pertains to the area in contact with the heatsink, when thermal energy from the solid transfers to the air. As air moves down the positive x-axis, a rapid decrease in temperature is observed, particularly at greater distances from the heatsink. At an air speed of 4 m/s, the temperature reaches a maximum of around 23℃, which is lower than the top of 28℃ seen at 2 m/s.

Thus, enhanced air movement improves the efficiency of convective heat transfer and the removal of heat. The reduced temperature differential allows air traveling at 5 m/s to collect and dissipate heat from the underlying ground more efficiently. The minimum temperature occurs at a velocity of 6 m/s, reaching around 22℃. This demonstrates an efficient method for dissipating heat. In this scenario, the gradient is less pronounced, indicating that the temperature decreases at a more uniform pace within the heatsink. As the air accelerates, heat dissipates more effectively from the sink.

7.jpg

Figure 7. The distribution of the heatsink temperature along the x-axis at the heatsink wall for the three inlet velocities

The air near the heatsink wall (x = 0 m) exhibits the maximum temperature due to its proximity to the heater. As air velocity increases, peak temperatures decrease (from 27℃ to 22℃). Moving right along the x-axis (away from the heatsink): As air advances, temperatures decrease, with higher speeds indicating better heat dissipation along the airflow. Low air velocity leads to a larger boundary layer near the heatsink wall, reducing heat transfer efficiency. At 4 m/s, thermal diffusion occurs more easily due to surface movement. At 4 m/s, the boundary layer diminishes, allowing efficient heat transfer across surfaces. The temperature around the heatsink decreases, allowing downstream air to absorb and dissipate heat, facilitating swift cooling. An increase in velocity increases the heat transfer coefficient, facilitating more effective heat removal. At 2 m/s, the boundary layer is extensive, resulting in elevated surface temperatures and increased thermal resistance. At 4 m/s and 6 m/s, heat transmission is more efficient due to reduced boundary layer thickness, allowing heat to dissipate more efficiently and securely. Laminar flow transpires at reduced velocities, resulting in prolonged heat dissipation [24]. Turbulent flow is more prevalent at speeds of 4 m/s or 6 m/s compared to lesser velocities of 1 m/s and 2 m/s. In turbulent heat transfer, the flow becomes chaotic, enhancing the mixing rate and reducing the thickness of the fluid layer where heat absorption occurs. Aerial heat transfer accelerates heat removal from the heatsink as air movement increases, hence reducing the temperature differential between the air and the heatsink surface. The data indicate that temperatures around the heatsink decrease as air velocity increases.

6.3 Air tunnel bottom temperature profile analysis

The heat sink's fins in Figures 8(A), (B), and (C) show thermal energy moving out into the open air tunnel. The plotted curves indicate the difference in temperature and the way that temperatures are arranged behind the heat sink while air flows in the tunnel. Models are tested with the base temperature set, and each design has air moving into the model at 2 m/s, 4 m/s, and 6 m/s.

In Figure 8(A), a significant amount of heat accumulates behind the heat sink fins when air flows at 2 m/s, as indicated by the elevated temperatures in the heat sink area. The temperature is significantly higher towards the fins of the heat sink, an indication that there is a large temperature gradient. The air flowing at only 2 m/s has too little momentum to transfer heat away from the heat sink efficiently. The blockage of the tunnel of the air causes the increase in heat at the exit (behind the heat sink) to be higher, as well as the warmth discharging at a leisurely pace. A strong thermal boundary layer is then formed as the temperature in the tunnel starts at a large distance from the rear of the heat sink fins. The airflow has not pulled away any thermal energy at all, which implies that the fan does not work very well when it comes to cooling the bulb at low speed. A discernible, gradual decrease in temperature continues from the heat sink to the tunnel exit; however, the clearly pronounced concentrations of heat near the heat sink suggest the lack of a sufficient amount of convective cooling. Due to the flow characteristics, an appreciable percentage of the heat produced by the sink is dissipated inefficiently as the heating element is largely covered with laminar flows of air [25].

8a.jpg

8b.jpg

8c.jpg

Figure 8. Heat distributions in the heatsink and at the bottom of the air tunnel in cases (A), (B), and (C) with inlet velocities of 2 m/s, 4 m/s, and 6 m/s

In the second configuration with an inlet flow velocity of 4 m/s, the heat removal from the substrate of the heat sink is significantly enhanced by the improvement of extracting of thermal energy extraction and transport into the ambient tunnel. This operating condition minimizes thermal nonuniformity, increases the thermal conductivity, and allows the flow of air, which is close to the sink, to absorb heat before it is transferred to the downstream regions. Measurements show that the sink surface temperature at 4 m/s is always lower and indicates a better heat dissipation ability from the electronic component. In addition, the reduced boundary layer thickness is also responsible for a further reduction of local air temperature and hence produces a more uniform thermal field behind the sink. The third operating condition, with an inlet airflow rate of 6 m/s, gives the highest heat removal efficiency. Under these circumstances, the zone of elevated temperature is confined to a tiny layer just behind the heat sink so that more thermal energy can be dissipated more rapidly in the surrounding air mass [26]. Thus, the conduit temperature tends to approach ambient temperatures before the exhaust. A steep temperature decrease is seen within the tunnel, with little heat content residue at the sink position.

6.4 Bottom fluid dynamics and thermal transport analysis

The heat exergy transmission from the heat sink is mainly promoted by convective transfer, in which the convective heat transfer coefficient shows an upward trend with the rise of air velocity. At low velocities, a relatively thick boundary layer is formed, which reduces the overall heat transfer rate. In contrast to the suction for the CFD, it is observed that when the free stream is present at a speed of 4 m/s and 6 m/s, the boundary layer thickness decreases, and therefore, the convective heat transfer is increased. Increased turbulent air flow at 6 m/s further increases the heat transfer efficiency due to the increased air flow mixing and corresponding decrease of thermal resistance between the heated sink at the heat sink surfaces. Conductive heat transfer along the heat sink decreases due to a thicker boundary layer, which leads to a steep temperature gradient at 2 m/s. Increasing the velocity results in a high rate of boundary layer disruption and a resultant faster heat dissipation and lower temperature gradient. The fast-flowing air acts like a heat exchanger and removes heat from the heat sink. The highest temperature in the tunnel is found near the heat sink fins, and the lowest temperature is obtained near the tunnel front [27].

6.5 Air tunnel temperature profile analysis

The heat dissipation capability of the heat sink is mainly determined by the convective heat transfer, in which the convective heat transfer coefficient will also increase with the increase of the airflow velocity. At smaller values of velocity, the production of a thicker boundary layer leads to a decrease in the rate of heat transfer. When the velocity of the airflow is 4 m/s and 6 m/s, it will contract the boundary layer and consequently increase the convective heat transfer. Turbulent flow at 6 m/s further promotes heat transfer efficiency because of the better mixing of air and reduced resistance to the flow of air over the heat sink surface. At an air flow speed of 2 appropriately m/s, the higher layer impedes the conduction of heat from the heat sink to create a major gap in temperature. Increased flow velocities cause a thin boundary layer to form rapidly, and heat energy is dissipated more quickly, and a temperature difference. The fast air movement acts well like a heat exchanger, moving the thermal energy away from the heat sink. The highest temperature inside the tunnel is measured near the heat sink fins, while the lowest temperature is near the front part.

6.6 Air tunnel section fluid dynamics and thermal transport analysis

From Figure 9, at 2 m/s, the convective heat transfer rate is inadequate, but it rises significantly with the increase in air velocity to 6 m/s. At the air velocity of 2 m/s, the flow is still laminar in nature, thus forming a thick boundary layer around the heat sink, which decreases the heat transfer coefficient over that air velocity. At an air velocity of 4 m/s, more rapid creation of the boundary layer causes a more rapid attenuation of the boundary layer and the ensuing convective heat transfer, although to a limited extent. As the velocity increases to 6 m/s, the flow becomes turbulent, which vastly increases heat transfer. This leads to a better spread of temperature, so that the air-conditioning system can cool down the living space. Electricity is transferred to the fins of the heat sink, and the thickness of the boundary layer depends on the air velocity. A low-velocity heat transfer coefficient is observed when the resin thickness is low; meanwhile, the heat dissipation effect is enhanced as the velocity increases and the thickness of the boundary layer decreases. Turbulence of 6-m/s increases heat dissipation via breaking the thermal boundary layer, reducing the sink temperature, and enhancing the heat transfer in the air duct. The higher the airspeeds, the faster the thermal diffusion, and so the temperature of the air will be uniform over the duct [28].

9a.jpg

9b.jpg

9c.jpg

Figure 9. Air tunnel section heat distributions (A) 2 m/s inlet speed, (B) 4 m/s inlet speed, and (C) 6 m/s inlet speed

6.7 Air tunnel outlet temperature analysis

Figures 10(A), (B), and (C) illustrate the temperature variation of the air exiting a heat sink within an air tunnel at three different velocities. Air circulates over the heat sink, and the distribution of heat is governed by the heat flux beneath the heat sink, analogous to a genuine electrical device. The temperature in the tunnel reaches 35.7°C near the heat sink and decreases with increasing distance from it (Figure 10). The transition from red, signifying elevated temperatures, to blue, representing lower temperatures, illustrates the temperature gradient, with the central region adjacent to the heat sink exhibiting higher temperatures and the peripheries displaying cooler temperatures.

10a.jpg

10b.jpg

10c.jpg

Figure 10. Outlet heat distribution models (A) 2 m/s inlet speed, (B) 4 m/s inlet speed, and (C) 6 m/s inlet speed

The heat sink's temperature gradient is influenced by the air velocity, with a 2 m/s entry air velocity causing a reduced heat transfer rate. The heat sink gradually releases heat, which means a rise in temperature above the surrounding air temperature. However, the air around the laptop is relatively cold due to the resultant low thermal mass interaction. An increase of the airflow to 4millipascals of air per second(ms-1) leads to an increased convective heat transfer coefficient, resulting in more homogeneous temperature distributions. As a result, the heat sink emits the heat more efficiently due to the increased fan airflow. At a maximum of 6 m/s, the air temperature in the outward movement is surveyed at 26.2℃. In such conditions, the temperature gradient at the outlet is getting steeper and steeper, and the hot spots next to the heat sink are significantly reduced. Improved performance - the enhanced rotation of the heat sink makes it highly efficient in dissipating the heat, thus enhancing the capacity of the chip to be cooled. This is in keeping with the spatial temperature distribution that confirms adequate thermal transfer when adequate air circulation is present. Figure 10 shows that the outlet temperature decreases with an increase in airflow velocity. With increased axial velocity, it helps in more heat transfer and hence lowers the outlet temperature and, in turn, provides a more uniform temperature distribution. In these simulations, the primary control on the disposition of the temperatures is that of heat transfer from the heat sink to the ambient air. Increased air circulation facilitates the waste heating from the heat sink, thus preventing overheating at the outlet. All of the researches show that the air near the edge of the heat sink is relatively colder than the air at the center, which indicates the reduced heat conduction efficiency at the outer section [29].

6.8 Air tunnel Bottom and the outer wall velocity profile analysis

Figure 11 shows how the air speed around heat sink fins reacts when placed inside an air tunnel with air entering at different speeds (2 m/s, 4 m/s, and 6 m/s). This affects thermal management and creates a less turbulent flow around the heat sink. A localized region cannot flow past the surface of the heat sink is created by this limited flow rate, resulting in a reduced convection zone and thus heat transfer. The device also does not dissipate the heat effectively; this may find its result in a hot point adjacent to the heat sink. Moved by a lowered airflow, it allows for less efficient cooling of the heat sink because the flow insufficiently cools its surface, and hence reduces the heat dissipation rate.

11a.jpg

11b.jpg

11c.jpg

Figure 11. The air tunnel bottom and outer wall velocity distribution is modeled for three inlet velocity conditions: (A) inlet velocity of 2 m/s, (B) inlet velocity of 4 m/s, and (C) inlet velocity of 6 m/s

The stagnant stream enables the pressure of air to be applied on all sides of the heat sink, which makes the temperature in the area high. In the 4 m/s scenario (Figure 10(B)), the air speed is more balanced as opposed to the 2 m/s scenario. The heat sink liquid has a faster velocity and increased movement around the fins, especially in the downstream. The flow velocity of 4 m/s causes random movement of the components of the media, which promotes mixing and transfer of heat. A higher speed of the fan allows it to take out more heat in the heat sink and release it to the outside. The circulation of air around the heat sink is also increased, which is observed through the high gradient of the velocity field. When there is more airflow, the heat sink is viewed to have a much more efficient cooling ability. Increased velocity of air above the fins maximizes its thermal transfer capacity, thereby increasing thermal dissipation. The optimum functioning of the heat sink is when the air velocity is as high as possible, and in this manner, the flow velocity is not skewed in any part of the heat sink. Such an even distribution enables the highest velocities to touch the whole surface. The high air flow around the heat sink is conducive to the mixing and cooling of the heat. Turbulent flow reduces hot spots on the surface of the heat sink, which can cause possible damage to the components. The maximum cooling of the heat sink is attained by the maximum heat dissipation, which does not allow stagnation in the parts, which might cause a bottleneck [30].

6.9 Air tunnel section velocity profile analysis

The findings of ANSYS modeling of the air flow around a triangular fin-shaped heat sink in an air tunnel at different inlet air speeds (2 m/s, 4m/s, and 6 m/s) are shown in Figure 12. These pictures represent the attributes of airflow around the heat sink and the effect on the rate of heat dissipation out of the heat sink. Figure 12(A) shows blue colors predominating around the heat sink and the bottom of the image in case the inlet velocity is 2 m/s, and the surrounding airflow is stagnant. At the top of the tunnel (red), the air flow is fast, and the airflow does not go through the heat sink. The lower velocity near the heat sink (0.8 to 2.4 m/s) indicates the presence of a very stagnant fluid on the edges of the heat sink. These places have a lot of air stagnation that prevents them from cooling down the surrounding environment in an effective way. This, in turn, raises the temperature of the heat sink, thereby reducing the effectiveness of the cooling role. The slow velocity of air leads to the failure of transmission of heat efficiently between the heat sink and the air. The laminar flow lowers the amount of heat that is transmitted and hence increases resistance to heat. This causes less heat to dissipate, which may overheat the device, hence overheat the heat sink.

On green and yellow patches that surround the heat sink at an air speed of 4 m/s, the deeper the airflow, as high as 5.5 m/s, is useful in heat dissipation. Turbulence generated over the heat sink promotes efficient heat extraction from the CPU. Triangular fins create a swirling vortex, optimizing surface heat transfer. An enhanced airflow design improves the cooling efficiency of the heat sink, enhancing its capacity to transfer heat to the air and remove it more efficiently. High air velocity enhances greater air mixing, leading to more homogeneous surface temperature and also lesser thermal resistance. This airspeed will cause rapid cooling and hence increased mixing and faster heat transfer, reducing stagnant air and causing uniform heating in the entire tunnel.

12a.jpg

12b.jpg

12c.jpg

Figure 12. Model of air tunnel section velocity distribution (A) 2 m/s inlet speed, (B) 4 m/s inlet speed, (C) 6 m/s inlet speed

6.10 Outlet velocity profile analysis in air tunnel

Figure 13 shows the distribution of velocity at the tunnel outlet with three triangular-shaped fin heat sinks in place, and an electrically powered apparatus at the bottom releases heat to the vicinity air. Spatial variation of velocity in the duct is investigated in three different inlet air velocities: 2 m/s, 4 m/s, and 6 m/s. The flow field in Figure 13(A) builds up with the length of the tunnel. In the central part of the image, all of the velocities are between 0.4 and 2.4 m/s, and the color scheme suggests that the tunnel walls and edge areas have the greatest velocities and reach 3.7 m/s. Some of the air near the heat sink produces significantly slower speeds. The triangular inserts bring about a localized turbulence, though at this low flow rate, the effects on the overall performance are also minimal. The slow-moving air results in inadequate circulation in the heat sink, hence hindering the quick removal of surface heat. This means that the heat sink is driven in a mostly laminar regime; hence, it reduces mixing of the surrounding air and reduces its ability to dissipate heat. The conditions lead to intense thermal sources on the surface of the sink, which makes it difficult to cool the equipment.

13a.jpg

13b.jpg

13c.jpg

Figure 13. Air tunnel outlet velocity distribution models (A) 2 m/s inlet speed, (B) 4 m/s inlet speed, and (C) 6 m/s inlet speed

Figure 13(B) shows a much higher flow rate as compared to Figure 13(A). Velocities are between 2.4 and 4.9, when it was 3-5 m/s in the area around the heat sink. The field of velocity around the heat sink is smoother, and the number of fins causes significant turbulence, and in a result increase in the flow of the surrounding air. With an inlet velocity of 4 m/s, turbulence induced by the outflow velocity raises the stagnated sheet of air near the heat sink and enhances heat exchange. The improved passage of air, in turn, improves the dissipation of the heat out of the system, results in a more balanced temperature distribution, and alleviates the presence of hot spots. This has the overall effect of minimizing the temperature of the component attached to the heat sink. Figure 13(C) indicates the highest velocity of 11 m/s, the highest velocity of flow that was attained during this research. Within the center portion of the heat sink, it will create a uniform velocity distribution through the domain as a result of the vigorous mixing. Heavy turbulence and deep mixing are also witnessed in the fluid at an inlet velocity of 6 m/s, which enhances convective heat transfer even better.

The air velocity is rapid to facilitate the swift dissipation of heat from the heat sink. Enhanced turbulence compels the heat boundary layer to alter continuously, resulting in more consistent heat transfers and improved performance. Due to its rapidity, the engine dissipates heat swiftly and effectively. The heat sink performs optimally in cooling due to the rapid airflow that dissipates heat from its surface. As a result, the heating of the heat sink is more homogeneous, which will guarantee the electronic equipment to be in a safe thermal temperature range. Convective heat transfer is improved as the rate of input air flow is enhanced, hence increasing the efficiency of the heat sink to dissipate heat to the chip. Turbulence is increased, thus enhancing the mixing of air, hence making the heat sink exchange a larger amount of heat with the air around it. When the translation velocities are low, the flow field has lower uniformity; conversely, as the velocity rises, the flow field gets more uniform [31]. With low speeds (around 2 m/s), the airflow stagnation will follow, which will cause the heat to accumulate inside the area of the heat sink. When the air currents accelerate to 4 m/s and 6 m/s, the flow becomes increasingly turbulent, facilitating enhanced heat distribution. Optimal cooling is achieved when the fan operates at maximum velocity (6 m/s), since this generates increased turbulence and enhanced air circulation. It ensures that the heat sink dissipates heat rapidly, preventing excessive thermal accumulation near the heat source.

6.11 3-way air inlet temperature profile analyzes

Figure 14 shows a temperature distribution in a heat sink because of a 10,000-watt heat source at the bottom. The air tunnel with a heat sink inside has an air inlet velocity of 2 m/s from the front and the two sides. This design shows that a thorough study of the heatsink thermal performance under forced cooling should be carried out. The color contour scale shows the heat sink has a temperature range between 38.5℃ to 57.0℃, and the zones show the colder temperatures in blue and the hotter temperatures in red. Through this contour, authors can study how the heat generated by the base is transferred through the fins to be distributed by the air around the heat sink.

Convective heat transfer in a system depends on the speed of air entering the system. At 2 m/s, forced convection transfers heat faster due to uniform air movement. This design helps remove more heat by creating airflow in various directions. Faster airflow speeds increase the thermal boundary layer thickness at the heat sink, speeding up heat transfer. Heat across the fins is uneven, with temperatures rising from the base and decreasing as air rises. The area near the base has the steepest temperature gradient. The center of the heat sink is generally hotter than the edges due to turbulent and slower-moving air. Figure 14(B) shows the temperature distribution in a system, with hot regions in red and cool areas in blue. The hottest region is at 56.5℃, while the coldest is at 26.8℃. The heat sink fins have the highest temperatures, with the hottest being at the core. The air in the frontal flow zone is chilly, indicating deficient thermal energy. The gradient shows temperature variation as air is transported from the entrance to the heat source. Air enters the heat sink to provide uniform velocity and temperature, reducing the likelihood of local hotspots. Turbulence and boundary layer disruption are crucial for achieving a high local Nusselt number. Heat transfer occurs more rapidly on the back fins, providing lateral circulation for cooling. Heat extraction improves with increased turbulence and Reynolds number in an aircraft featuring compound inlets [32]. The fins exhibit stability and consistent heat dissipation outward. The light blue hue of the wake indicates significant convection heating.

14a.jpg

14b.jpg

Figure 14. (A) 3-way 2 m/s air inlet heat sink temperature distribution profile, (B) 3-way air inlet heatsink and air tunnel bottom heat distributions

15a.jpg

15b.jpg

Figure 15. (A) 3-way air inlet heat sink and air tunnel cross-section heat distribution, (B) 3-way air inlet, air tunnel, and outlet temperature distribution

The XY cross-sectional view of the heat sink, as shown in Figure 15(A), illustrates the presence of fins inside the tunnel, so this is used in the analysis. The electronic device absorbs heat using vertical fins, which promotes the heat flow to the surrounding air, hence cooling the electronic device. The strengthened thermal performance of the heat sink is associated with forced convection. There are three different directions in which ambient air is introduced, and this guarantees equal distribution of heat as well as effective dissipation. The tri-inlet configuration spreads the thermal load and hence prevents the overheating risk, which in turn preserves the performance of the system. The inflow of hot air at the upper, lateral, and inferior positions disturbs the thermal layer in the exterior of the fins, causing inefficient heat transfer. The intake structure has a checkboard form, which reduces the thickness of the boundary layer to a minimum, increasing heat loss through the fins. The color gradient of the fins is red (at the base), blue (at the end), indicating a progressive fall in temperature as one goes closer to the base than the apex. Figure 15(B) shows the temperature distribution at the heat sink outlet assembly ranged between 26.9℃ (blue) and 33.5℃ (red). The experimental data shows that the heat sink dissipates the heat to the surrounding air successfully. The high temperature record in the area surrounding the heat sink, where the thermal energy is concentrated. When the air reaches the heat sink, the temperature of the air will reduce as it gets farther, explaining that the outgoing air is much cooler in comparison with its original temperature. The spatial pattern of the temperature of the air in the tunnel provides an assessment criterion of cooling performance and thermal structuring of the system.

The peak temperature would be expected to be close to the heat sink, which is how heat is transferred through the process of exchanging it between the source and the environment [33]. The cooling system uses forced convection, and the air flow enters the system via three discrete ports at a speed of 2 m/s. Increasing the speed of air passing over the fin enhances mixing, decreases the layer of stagnant hot air close to the fin blades, and improves the efficient and quick removal of heat from the heat sink.

6.12 Velocity profile of a three-way air inlet

The results of the CFD simulation of air leaving a heat sink that has triangular-shaped fins indicate a clear and uniform water velocity within the intake area. The air velocity ranges between 2.1 m/s to 18.5 m/s at the intake, which evidences shifting slowly moving air, rapid shifting to the limit, and swiftly moving air. When the air touches the heat sink fins, the speed of the air changes and hence causes turbulence to the fluid in the surroundings. Regions just out of the fins where streamlines are constricted are the ones with increased velocities compared to other sections. The sharp edges are classified as rapid acceleration because of an increased velocity in the particular area. The water then moves around the triangular-shaped fins to increase its speed, which reaches a maximum of 18.5 or so towards the fins. The fins offer a narrowed channel to the flow and thus increase the velocity of the flow in that area and consequently cause high velocities. The speed of air decreases towards the fin, thus resulting in a slowing of the flow and high turbulence. Massive drag in velocity is experienced at the surfaces of the fins due to the effect of the boundary layer. As the distance of the fins increases, air pressure and velocity increase once more. The high to the low velocity shifts are sudden, with a velocity of 18.5 m/s at the tip of the fin and either 10.3 m/s or below in the wake.

The thermal radiations given by the base of a heat sink are used to increase the temperature of the surrounding air, which causes the development of a thermal boundary layer. This layer makes the air near the heat sink flow at a lower speed; thus, a reduction in the speed of the surface wind occurs. The ambient airflow gets disrupted by the upward movement of the hot air in the heat sink, creating the fluctuation of air velocity in a stipulated area. Streamlines can separate as the convection moves the hot air to the top, and velocities of about 10 m/s and some more may develop, as the hot air is accelerated because it is of lesser density. The thermal flow zone can also cause mixing between the heated air and the surrounding air, and this would cause an alteration in the velocity pattern. These thermally induced currents can form certain areas where there is an augmented current in comparison to the nearby cooler spaces. The air velocity is enhanced by a few millimeters per second due to the convection process, whereby it increased to 12.3 m/s instead of 6.2 m/s. Towards the periphery of the heat sink, the walls and triangular fin structure that surrounds the construction affect the airflow. Inside the tunnel, the air is moving at high velocities, between 10.30 m s^-1 and 18.50 m s^-1, as fewer objects may occur. Conversely, the air near the sidewalls and fins has a lower velocity as compared to the remainder of the flow [34].

16a.jpg

16b.jpg

Figure 16. (A) 3-way air inlet velocity profile. (B) 3-way air inlet tunnel outlet velocity profile

Figure 16(B) exemplifies the velocity distribution (at the exit of the air tunnel) of an air stream through the heated fins and the variation in the distribution of the velocity. The shape of the heat sink, as well as the contact with the fins, influences the flow out of the outlet. During the intermediate part, the velocity of the air mass is extremely high (18.5 m/s). However, the funneling effect of outflow suggests a constricting point, or a neck, in the middle of it, which suggests that the flow has hastened as it leaves the heated area. The velocity decreases gradually beside the tunnel walls, with a minimum of 2.1 m/s. The heat flux conducted through its lower surface changes the velocity across the heat sink. Through the heat gradient, a very thin layer of air builds up, creating quicker air flow. The flow rate of 18.5 m/s by the inner stream means that the flow is accelerating when it flows around the sink. Heat sink and triangular fins probably increase the level of operation of fans due to the reduction of the aperture.

17a.jpg

17b.jpg

Figure 17. (A) and (B) bottom, walls, and outlet 3D 3-way air inlet tunnel velocity model

Figure 17 shows the air flow in the air tunnel by giving a comparative analysis of the velocity of air and the working mechanism of the mechanism of cooling system, that is, the heat sink and the triangular fins. The flow of air moves through the tunnel entrance, causing a flow, and it reaches the heat sink, coming into contact with the fins, which causes strong differences in the velocity. The sharp edges of the triangular fins create high velocity streams of air, and turbulence caused by the fins increases the speed of central airflow, but at the same time slows it down in the deep downstream areas.

Having moved through the triangular fins, the flow displays acceleration, resulting in regions of significantly lower speed. These zones are reflected as spectral coloring, with the blue color representing the areas where the airflow is less, as the air is no longer attached to the fin surfaces. The thermal layer is formed on the surface of the heat sink, which is due to the release of heat at the bottom of the heat sink, and this cools the air, causing a slowing of the air temperature. The resultant loss of velocity is within the range of 4.1 m/s to 6.2 m/s. Thermal effects are also noticeable within the vicinity of the source of heat, and in places where the air rises.

After the airflow arrives on the tunnel walls, it is further slowed down by viscous friction in the boundary layer, and is sufficient to reach such wall velocities as 2.1 m/s: this is due to the confinement effects imposed by the tube shape. The flow along the walls is slower than at the middle of the tunnel. Triangular fins accelerate airflow, constricting the airflow and enhancing velocity in their vicinity. Turbulence generated by fins creates vortices downstream, establishing areas of diminished velocity. The streamlining is ineffective due to the presence of turbulent eddies behind each fin, impeded flow, and reduced velocity. Wake regions contribute to enhanced mixing and heat transmission throughout the system. Heat is delivered near the base of the heat sink, resulting in reduced air density.

6.13 Model assumptions affect

Some assumptions and simplifications are made on the basis of the research model that can affect the accuracy and relevance of the results. The heat sink and fins were designed using a simplified geometry of idealized triangles, fin shapes in SOLIDWORKS, although real-world manufacturing failures and highly complex real-world surface finishes. The simplification can cause a bias in the results when analyzing a uniform geometry of a fin, i.e., underestimation of effective heat dissipation. The thermophysical properties, thermal conductivity, and emissivity, are likely to remain stable and temperature independent and might affect the predictions at different operational temperatures. The air was regarded as an ideal gas that is incompressible and whose flow is in steady-state turbulent flow, without taking into account the conditions of transience and little compressibility that might arise in short-term changes in heat. It was simulated in the realizable k-ε model, which is deemed a decent compromise between the accuracy and the cost of computation. This model, however, averages small-scale eddies and can also fail to involve small-scale turbulent structures and near-wall effects relative to more complex models, such as LES. The steady-state approach overlooks any transient thermal change and temporary heat transfer change in the transient state of real electronics cooling processes, when temporary thermal change and dynamic airflow change are commonly experienced in practice (usually in electronics cooling). In the case of the computational domain, some spatial limitations were imposed that include the size of air tunnels and no side gap between the heat sink base and the tunnel base, which cannot adequately characterize all actual installation environments. The simplification of these boundary conditions may have an impact on the behavior of airflow and heat transfer, which is used to predict the heat sink performance. Overall, despite consideration of the modeling and geometry assumptions, which give a good understanding of the mechanisms of heat transfer to illustrate the advantages of turbulent airflow over triangular fins, the idealization and simplification of both models can change the outcomes, which can influence them, and experimental validation under realistic conditions is suggested to check the results.

The data in the study on the triangular heat sink fins were assessed by the authors against the previous works of other researchers in order to confirm their relevance. The simulation by the use of computational fluid dynamics proves performance and fluid dynamics in the heat sink.

8.1 Effect of triangular fins on heat transfer performance

Based on numerical calculations, triangular fins are greatly beneficial to increase heat sink capacity and dissipation of thermal energy by modifying the boundary layer and causing greater turbulence. The investigation by Menni et al. [35] studied the effect of fin geometric features, such as a triangular fin, on turbulent heat transfer with respect to fin spacing. The authors argue that triangular fins offer more surface area and geometric complexity, thus enhancing heat-transfer efficiency at turbulent flow conditions [35]. The simulations below show that a simulation in which the airflow rate is increased will increase the rate of heat transfer to the surroundings of the device faster and will thus support the central role of the unique geometry of the fins in improving cooling effectiveness. The triangular shape performs better than circular and rectangular ones due to the enhanced turbulence generated by the shape that facilitates mixing of air, destabilization of thermal boundary layer and provides more uniform temperature conditions on the surface of the heat-sink. The results of the CFD presented in this paper indicate that as the air velocity decreases, it rises to 2 m/s to 6 m/s, and the temperature of the hottest part of the heat sink is reduced to values as low as 52.5℃. This is credited to the fact that triangular fins form a smaller boundary layer, and localized air acceleration (later on 18.5 m/s in and around the tips of the fins) increases the intensity of the convective heat transfer. These increased speeds ensure that the flow develops. into full turbulence, and the triangular geometry facilitates the formation of vortexes and recirculation of the air that facilitates heat dispersion. Table 5 compares the results with the previous research papers' results for more accuracy of these results.

Table 5. Triangular fins result in comparisons with the previous studies

8.2 Comparison with heat sink performance

The study's finding is corroborated by Kishore's research on the effectiveness of triangular fins in CPU heat sinks. Kishore's computer simulations demonstrated that triangular fins disperse heat far more efficiently than rectangular fins, particularly under varying circumstances or airflow. The results of the simulation in this study indicate that triangular fins enhance convective heat transfer, particularly at elevated air velocities [36].

8.3 Validation of flow and thermal characteristics

These fluid dynamics and heat transport in the proximity of the triangular fins are in line with the results of Hithaish et al. [37]. Their numerical study encompassed CFD simulations of triangle pin fin heat sinks, where it is examined that triangle fin types support greater fluid mixing and additionally decrease the thickness of the boundary layer of heat, thereby promoting greater heat transfer. The current results are consistent with the results reported by Hithaish et al. [37], which highlight that dissipation of heat is easier due to the higher rate of airflow.

8.4 Improvement in cooling efficiency

Hameed et al. [38] investigated the efficacy of heat sinks, including diverse triangular fin configurations, utilizing computational fluid dynamics (CFD). The study indicates that triangular fins facilitated airflow that is more equitable and enhanced cooling efficiency. The study indicates that triangular fins provide more uniform heating throughout the heat sink, particularly under conditions of increased airflow. In summary, the simulation statistics corroborate prior research demonstrating that triangular fins enhance the performance of heat sinks. Menni et al. [35] asserted that triangular fins enhance cooling by increasing surface area and inducing more turbulence. Bhuvan and Kishore [36] concur with the findings, indicating that triangular fins are more effective at cooling than rectangular fins. Hithaish et al. [37] and Hameed et al. [38] showed via their experiments that triangular fin heat sinks enhance heat dissipation by optimizing fluid flow, consistent with this research.