Microchannel Heat Sink Research Articles

Numerical Investigation of Increasing-Decreasing Stepped Micro Pin Fin Heat Sink Having Various Arrangements

The ongoing trend of miniaturization of electronic devices, including computer processors, high-speed servers and micro-electro-mechanical system devices, should go hand in hand with their improved performance. However, managing heat remains a major challenge for these devices. In the present study, a numerical investigation was done on a micro-channel heat sink with an open-stepped micro-pin fin heat sink with various arrangements through ANSYS software. Pin fin was varied in a fashion of increasing and decreasing. The working fluid opted for was water in a single phase. The analysis takes into account varying thermo-physical properties of water. The operating parameters, i.e. the Reynolds number was taken as 100–350 and heat flux as 500 kW/m2. Arrangements selected were staggered and inline. Observations revealed that the staggered 2 arrangement has shown better thermal performance than other arrangements within the entire investigated range of Reynolds numbers because of the effective mixing of fluids. Furthermore, the inline configuration of micro pin fin heat sink has the worst performance. It is interesting to note that a very small difference was observed in the heat transfer capability of both staggered configurations, while the pressure drop in the staggered 2 arrangement has shown an elevated value at a higher Reynold number value compared to the staggered 1 arrangement.

Heat dissipation analysis on the designed inner-outer circulation impingement double-layer microchannel heat sinks with chamfers in power electronic cooling system

This study discusses a new design which utilizes chamfers to further improve the thermal performance of inner-outer circulation impingement double-layer microchannel heat sinks by simulations and experiments manufactured with 3-Dimension printing. In contrast to former designed inner-outer circulation impingement double-layer microchannel heat sinks, inner-outer circulation impingement double-layer microchannel heat sinks with chamfer shows significant advantages in improving overall thermal performance in power electronic cooling. The results of simulation are in good agreement with those of experiment in five 3-Dimensional printing tests. It is demonstrated that the introduction of chamfers is effective in controlling the thermal gradient on substrate of heat sinks, and reducing the peak temperature on substrate of inner-outer circulation impingement double-layer microchannel heat sinks with chamfer as a result. The best performance is presented by a 0.2 mm chamfer located on the corner of the inner-outer circulation shaft in inner-outer circulation impingement double-layer microchannel heat sinks with chamfer. Experimental studies and numerical simulations both indicate that inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer significantly enhances heat transfer characteristics. In addition, the average Nusselt number for inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer is higher than that of other tests. Moreover, inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer performs better than other designs in terms of the overall heat transfer performance, which is significantly better than inner-outer circulation impingement double-layer microchannel heat sinks without chamfers.

Microchannel Heat Sinks—A Comprehensive Review

An efficient cooling system is necessary for the reliability and safety of modern microchips for a longer life. As microchips become smaller and more powerful, the heat flux generated by these chips per unit area also rises sharply. Traditional cooling techniques are inadequate to meet the recent cooling requirements of microchips. To meet the current cooling demand of microelectromechanical systems (MEMS) devices and microchips, microchannel heat sink (MCHS) technology is the latest invention, one that can dissipate a significant amount of heat because of its high surface area to volume ratio. This study provides a concise summary of the design, material selection, and performance parameters of the MCHSs that have been developed over the last few decades. The limitations and challenges associated with the different techniques employed by researchers over time to enhance the thermal efficiency of microchannel heat sinks are discussed. The effects on the thermal enhancement factor, Nusselt number, and pressure drop at different Reynold numbers in passive techniques (flow obstruction) i.e., ribs, grooves, dimples, and cavities change in the curvature of MCHSs, are discussed. This study also discusses the increase in heat transfer using nanofluids and how a change in coolant type also significantly affects the thermal performance of MCHSs by obstructing flow. This study provides trends and useful guidelines for researchers to design more effective MCHSs to keep up with the cooling demands of power electronics.

High-performance near-substrate heat sink with Tesla-like rotor-wing microchannel for chiplet cooling application

Microchannel heat sink provides a viable solution for enhancing thermal management in high-power chiplets. However, in consideration of cooling efficiency, low pressure drop, cost-effectiveness and reliability, it’s challenging to create an effective heat sink for a million-watt chip. Inspired by Tesla structure, this study introduces a Tesla-like rotor-wing microchannel (TRWM) to boost cooling performance. Due to the features of main channels, branch channels, and micro-islands in TRWM design, fluid in microchannel is effectively mixed and stirred with varied flow patterns, high temperature gradients and significant velocity gradients, which enhances the cooling capacity through precise fluid dynamics adjustment. Three different TRWMs are designed and compared by simulations. And the simulated results show that TRWM of 135° model achieves a maximum heat flux of 1514 W cm−2 @0.1 cm2 under a 60 K temperature rise, improving cooling efficiency by 19.4 % over the traditional channel design with 1221 W cm−2 @0.1 cm2. And then, the TRWM is fabricated using Ultraviolet Lithgraphie Galvanoformung Abformung (UV-LIGA) and bonding processes. Ultimately, the fabricated 135° TRWM sample demonstrated a heat dissipation capacity of up to 1446 W cm-2 @0.1 cm2 with a temperature increase of 60 K, which corresponds well with the simulated results. Moreover, the discrepancy between the actual and simulated values is less than 6.3 % under the same conditions. This performance provides a practical design solution for chiplet cooling and highlights the potential of bioinspired microfluidics.

Fabrication of microchannel heat sink using additive manufacturing technology: A review

Additive manufacturing is a cutting-edge process that enables the creation and development of complex shapes, opening new avenues for advanced heat sink designs that maximize heat transfer while minimizing pressure drop. This review provides an overview of recent results and insights from global researchers on the additive manufacturing of microchannel heat sinks. It discusses various novel microchannel heat sink types fabricated using additive manufacturing and the complexities involved in their fabrication. Additionally, the review explores geometric configurations, the application of computational optimization methods, and the impact of surface roughness on heat transfer and pressure drop. The primary focus is on the fundamental advantages of additive manufacturing in addressing complex heat transfer designs. However, the review also highlights limitations restricting its benefits in specific applications, such as material handling and availability. This review identifies future challenges for creating novel heat sinks with complex geometries and opportunities for advancements in heat transfer technology.

Numerical Simulations of Flow and Heat Exchange in Zigzag-Shaped Microchannels

Cooling of electronic components is of great importance currently. One of the most important methods of integrated circuit cooling is the use of microchannel heat sinks. The aim of this work is to analyze the cooling capacity of zigzag shaped microchannels. The heat exchange for four different microchannels was tested depending on the flow rate of the cooling liquid (water) and the temperature of the cooled element. The system of differential equations that describe fluid flow and heat transport is presented in the paper. The equations were solved using the finite volume method. The work showed that both the increase in the number of zigzag sections and the increase in the flow velocity cause an increase in the flow resistance. In contrast, an increase in the temperature of the cooled element causes a decrease in fluid viscosity, which results in a decrease in flow resistance. From the point of heat exchange, both the increase in the number of segments, the flow rate, and the temperature of the cooled element increase the cooling capacity of the microchannel. Research shows that zigzag shaped microchannels are excellent cooling elements, especially for geometrically small heat sources such as electronic components.

Qualitative analysis of the coupling effect of fluid velocity distribution in microchannels on the performance of water-cooling lithium-ion batteries system

ABSTRACT Lithium-ion batteries are the direct power sources of electric vehicles, but their high heat flux density restricts their development. Microchannel heat sinks (MCHS) can assist in heat dissipation to overcome this. The distribution of fluid velocity among microchannels has a considerable effect on the performance of MCHS for a water-cooling lithium-ion batteries system. In this paper, a new microchannel heat sink with high depth to width aspect ratio is proposed and the influence of four different aspect ratios on the distribution of fluid velocity among microchannels and heat transfer performance of MCHS was numerically studied by computational fluid dynamics (CFD). The results showed that at the same inlet flow rate, the larger the aspect ratio of the microchannels, the better the uniformity of the internal fluid velocity. The heat performance of microchannel structures with four different aspect ratios for a water-cooling lithium-ion batteries is further investigated experimentally. Compared with the simulation results of the fluid velocity distribution, the coupling effect between the fluid velocity distribution in the microchannels and the heat dissipation performance of a water-cooling lithium-ion batteries is analyzed. The results fully demonstrated that a larger aspect ratio of the microchannels results in a better heat dissipation performance on the surface of the lithium-ion batteries. Optimizing the aspect ratio of the microchannels to facilitate a relatively uniform velocity distribution to improve heat dissipation performance of the water-cooling system may be a key factor to be considered, which provides a new idea for passive thermal management of batteries.

A Numerical Study on the Novel Composition of Porous and Solid Ribs to Augment the Thermal Performance of a Hybrid Nanofluid-Based Microchannel Heat Sink with External Fins

A Numerical Study on the Novel Composition of Porous and Solid Ribs to Augment the Thermal Performance of a Hybrid Nanofluid-Based Microchannel Heat Sink with External Fins

Cooling characteristics of nanofluids in a snowflake and squid fin composite bionic microchannel heat sink

To improve the heat dissipation performance of electronic components, this study proposed a novel biomimetic microchannel design inspired by snowflakes and squid fins. A numerical simulation method was employed to investigate the cooling characteristics of nanofluids at different concentrations within this biomimetic microchannel heat sink. The microchannel is shaped like a snowflake, while the base plate features a biomimetic squid fin structure. The study focused on analyzing the effects of waveform height (amplitude A = 0.1–0.4 mm) and waveform frequency (B = 0.5–2π) on heat transfer performance. The results indicated that when nanofluids flow over a base plate with a wavelength frequency of B = 0.5π, there is a significant enhancement in heat exchange while simultaneously reducing flow resistance. In the microchannel heat sink (A = 0.3 mm, B = π), the thermal conductivity of the nanofluids can be increased by up to 32.56 %, with a maximum comprehensive evaluation index of 1.68. This research provides important guidance for the application of nanofluids and biomimetic microchannels in the thermal control of electronic devices.

Flow boiling heat transfer in multi-stage enhanced open microchannels with micro/nano structures

In the realm of flow boiling research, open microchannels heat sink is garnering more attention due to its potential in enhancing heat transfer and mitigating flow instability. Nevertheless, growing heat dissipation needs necessitate further enhancement of the heat removing capability of flow boiling within open microchannels. In this paper, experimental research on flow boiling in open microchannels utilized a new environmentally friendly refrigerant SF-33 and presented a novel heat transfer enhancement strategy, specifically, a multi-region enhancement strategy for diverse flow pattern stages. A copper heat sink with 25 open microchannels was fabricated, and a layer of copper powder particles was sintered on the channel bottom to create a microporous structured surface in about 1/3 of the inlet region. Several layers of copper wire mesh with micropores were sintered in about 1/3 of the outlet region, and the nanostructures were grown on the wire mesh by chemical treatment, resulting in a micro-nanocomposite structure. The final product formed the multi-stage enhanced open microchannels (MSEOM). The heat transfer performance and pressure drop of SF-33 saturated flow boiling in MSEOM under different operating conditions were determined, and the transitions of flow patterns were visualized to analyze the mechanism of two-phase heat transfer. The study demonstrated that despite SF-33 having a low latent heat of vaporization, its flow boiling heat transfer coefficient in MSEOM was high. This was attributed to the enhanced effect of multi-region surface modifications on heat transfer. Additionally, a vapor plug breakup-dispersed bubble flow pattern was observed for the first time, which resulted from the combined influence of the low surface tension property of SF-33 and the boosted nucleate boiling triggered by the micro-nanostructures in the outlet region.

Investigation of hydrothermal characteristics and entropy generation in a microchannel heat sink with elliptical fins

Abstract As the integration of microelectronic devices continues to increase, thermal management issues become increasingly prominent. Microchannel heat sinks are effective for heat dissipation in high heat flux microelectronic devices. This study designs five elliptical finned microchannel heat sinks with different aspect ratios (γ) while maintaining a constant elliptical area to enhance heat transfer performance. The values of γ are 0.74, 0.86, 1, 1.17, and 1.35, respectively. Over the Reynolds number (Re) range of 293 to 740, the hydrothermal characteristics and entropy generation of the microchannels with elliptical fins (MC-EFs) are investigated through numerical simulations. The thermal enhancement mechanism of MC-EFs is analyzed via flow, temperature, and pressure fields. The optimal γ value is determined by maximizing the overall performance factor (OPF) and minimizing the augmentation entropy generation number (Ns,a). Results indicate that introducing elliptical fins in the straight microchannel (SMC) significantly improves heat dissipation. An increase in γ enhances thermal performance but also raises flow resistance. Specifically, when γ increases from 0.74 to 1.35, the Nusselt number (Nu) improves by 10.71%-25.64%, and the friction coefficient (f) increases by 30.92%-57.27%. Overall, at Re = 740, the OPF of the MC-EF with γ = 1.35 reaches a maximum of 1.285, and at Re = 597, the Ns,a for this configuration is minimized to 0.578. These findings provide valuable insights for effective thermal management in microelectronic devices.

Numerical Study on Heat Transfer Efficiency and Inter-Layer Stress of Microchannel Heat Sinks with Different Geometries

As electronics become more powerful and compact, laminated microchannel heat sinks (MCHSs) are essential for handling high heat flux. This study aims to optimize the MCHS design for improved heat dissipation and structural strength. An orthogonal experiment was established with the average surface temperature of the heat source as the evaluation metric, and the optimal structure was determined through simulation. Finally, cooling uniformity, fluidity, and performance evaluation criterion (PEC) analyses were carried out on the optimal structure. It was determined that the optimal combination was the triangular cavity microchannel (MCTC), with a microchannel width of 0.5 mm, a microchannel distribution density of 60%, and the presence of surface undulation on the microchannels. The result shows that the optimal structure’s peak inter-layer stress is just 34.8% of its longitudinal tensile strength. Compared to the traditional parallel straight microchannel (MCPS), this structure boasts an 8.6 K decrease in the average surface temperature and a temperature variation along specific paths that is only 9.9% of that in traditional designs. Moreover, the optimal design cuts the velocity loss at the microchannel entrance from 75% to 59%. Thus, this research successfully develops an effective optimization strategy for MCHSs.

Enhanced flow boiling heat transfer with three-section sudden expansion microchannels

In this study, a three-section sudden expansion microchannels (TSE-MCs) heat sink was proposed to stabilize the flow boiling and improve the thermal performance of the heat sink exposed to high-heat-flux scenarios. The structural effect of newly designed TSE-MC and operating conditions on the heat transfer coefficient (HTC), pressure drop penalty, and flow instability were experimentally investigated and contrasted with continuous straight microchannels (CS-MCs). The experiments were performed at a saturation temperature of 35.5 °C, the mass flux ranging from 468–1033 kg/m2 s, and the heat flux up to ∼132 W/cm2. A comparative analysis based on the experimental results was conducted. Compared to CS-MCs, the nucleate boiling in TSE-MCs was initiated in advance with 0.2–1.2 °C reduction of wall superheat. The maximum HTCs at four mass fluxes, which was up to 62784 W/m2 K, were enhanced by 18.9–23.6 %. The uniformity of wall temperature was improved and the average wall temperature was reduced. HTCs and visualized results indicated that the dominant mechanism for heat transfer in TSE-MCs was nucleate boiling. Meanwhile, the pressure drop in TSE-MCs was slightly reduced, and pressure drop oscillations were greatly suppressed. The flow reversal in the inlet plenum was completely eradicated, and the performance evaluation criterion (PEC) of TSE-MC outperformed that of CS-MCs and was improved by 79.81 %–86.25 %. Overall, the present work demonstrates the great advantages of the newly proposed TSE-MCs, it offers a reference for the design of microchannel heat sinks for the real high heat flux dissipation applications.

Experimental study of subcooled flow boiling in microchannel heat sinks integrated with different embedded pin fin arrays microstructures

The optimized microchannel heat sinks could enhance flow boiling for effectively tackling the electronics cooling. The flow boiling experiment for three microchannel heat sinks integrated with different layouts of entrenched pin fins is conducted at flow rate of 273.6–456 kg/(m2.s) and inlet subcooling of 35∼50 K. The overall/local heat transfer features, pressure drop and boiling mechanism are studied. The hybrid pattern presents earliest initial boiling and lower superheat than the microchannel heat sink with uniform pin fins arrangement at moderate and large flow rates. The trend of overall and local HTC (heat transfer coefficient) is similar, which occurs peak at onset nucleation boiling, and then decreasing with increasing heat flux. At the largest flow rate, the hybrid pattern exhibits 2.7–3.5 times peak HTC promotion than other patterns. As for lowest flow rate, the hybrid pattern does not manifest remarkably superior performance due to downstream vapor cores clogging effect. The hybrid pattern shows largest pressure drop, and the smaller inlet subcooling manifests inferior heat transfer and resistance performance. The comprehensive performance factor (CPF) is proposed, and the pattern with uniform small-sized pin fins shows optimal CPF especially for low flow rate, which is considerable compared with the reference heat sink structures until high heat flux. This study may provide some insight into the design of microchannel for flow boiling heat dissipation.

Thermal management for microelectronic chips under non-uniform heat flux with supercritical CO2

With the rapid growth of information technology and the evolution in the use of microelectronic chips, these components are facing major challenges of high heat dissipation and inhomogeneous heat flux. To address the hotspot issues, a combination of microchannel heat sinks (MCHS) with cavity-rib designs and supercritical fluids is a potential solution. This study compares the thermo-hydraulic properties of water and supercritical carbon dioxide (sCO2) under various boundary conditions and hotspot locations during non-uniform heating. The results showed that sCO2 can effectively improve temperature uniformity along the heat sink in the presence of hotspots as compared to water. Considering a mass flow rate of 600 kg/(m2·s), the inhomogeneity index of the basal temperature of sCO2 is found to be 0.24, significantly lower than 4.22 for water. This indicates that sCO2 eliminates hot spots by rapidly increasing specific heat capacity near the pseudo-critical temperature. Furthermore, it is noted that maintaining the operating temperature of sCO2 near the pseudo-critical temperature can increase the specific heat capacity of the fluid in a short time, in addition to reducing the corresponding density and viscosity. Consequently, the entropy generation rate of sCO2 under ideal conditions is 46.6 % of that of water. Therefore, the proposed combination of a microchannel of complex structure and sCO2 in this study is demonstrated to effectively reduce the influence of hot spots and improve the overall thermal performance of heat sinks.

Numerical and experimental study on manifold-distributed jet microchannel with micro-pin-fins

Traditional parallel microchannels are inadequate for managing the thermal requirements of newer, large-area and high-heat-flux chips. This inadequacy arises from its high flow resistance and poor temperature uniformity. Therefore, A novel manifold microchannel heat sink combining manifold inlet/outlet structures, distributed array jets, and micro pin-fins is introduced. Numerical simulations and experimental methods were employed to investigate the flow and heat transfer performance of the heat sink. Experimental results show that, with an average heat flux density exceeding 330 W/cm2 and a total power of 2500 W, the average chip temperature remains below 70 °C, ensuring efficient heat dissipation. Secondary impingement occurs at sufficiently low jet chamber heights, resulting in an increase of 3 times in the average Nusselt number for a smooth base plate. For the micro-pin-finned surface, it is shown that the presence of micro-pin-fins is not necessarily conducive to heat transfer enhancement. A critical volume fraction of micro-pin-fins (critical fin-ratio) exists where the obstructive effect and enhancement effect balance each other out. This value is influenced by multiple parameters. Finally, a novel relationship for predicting the average Nusselt number of jet impingement was proposed, with an average absolute error of less than 15 %. This series of investigations addresses the existing gaps in research on manifold-distributed array jet heat sinks and provides a meticulous theoretical foundation for the design and optimization of heat sinks facing the high-power chips.

Numerical study on heat transfer and flow characteristics of symmetric Tesla-type microchannel heat sinks

This study numerically investigates the thermal performance of multi-stage Tesla valve microchannels (TVM) and a symmetric variant (SYMTVM) using single-phase deionized water, with mass flow rates ranging from 0.5459 to 1.6377 g/s. Both designs, particularly under reverse flow, exhibit lower peak temperatures and reduced temperature gradients compared to forward flow. The SYMTVM, characterized by its increased vortices and bifurcations, periodically disrupts and redevelops the thermal boundary layer, enhancing heat transfer efficiency. The TVM exhibits a significantly higher pressure drop than the SYMTVM across all flow conditions, with the reverse flow in TVM reaching up to 2.48 times that of forward flow and exceeding SYMTVM, especially at a peak flow rate of 1.6377 g/s. The performance evaluation criteria (PEC) and thermal resistance criteria (PECTR) demonstrate the superior performance of SYMTVM, with a reduced connection angle between the trunk and helix regions enhancing thermal efficiency. Furthermore, the SYMTVM-Reverse structure with a 30° interconnection angle demonstrates superior performance compared to the conventional rectangular microchannel (RM), achieving a Nusselt number (Nu) that is five times higher than that of the RM and an overall performance up to 2.59 times greater. These results indicate the SYMTVM-Reverse’s high heat transfer efficiency and its capacity to effectively balance thermo-hydraulic performance, even with increased power dissipation.

Optimizing microchannel heat sink performance: Effect of step-gap design and contraction on flow boiling stability and heat transfer

Liquid cooling with cold plates (microchannels) is an advanced thermal management technique used in high-performance electronics and computing systems. Conventional microchannels have a straight fin array that shows instabilities during two-phase flow boiling. The present experimental investigation continues previous studies to explore the effects of combining the contraction before the microchannels (CBM) and a step gap above the microchannels (SGAM) in the enclosed cover of the heat sink to improve two-phase convective boiling performance. The microchannel heat sink is sized at 49 mm × 52 mm, featuring a channel width of 200 μm and a height of 3 mm, with a fin thickness of 200 μm. Dielectric fluid HFE-7000 was used as the working fluid, and the mass flux ranges from 30 to 260 kg/m2·s, with concentrated heat flux varying from 50 to 156 W/cm2. The results reveal that the combination configuration significantly reduces pressure drop by approximately 23–56 % lower than that of the plain (Conventional) configuration. This combination of configurations is especially effective at a high heat flux above 100 W/cm2. Experimental results indicate that the combination configuration lowers wall superheat temperatures compared to the plain sample, therefore enhancing the overall heat transfer coefficient by 30–154 % across the tested mass flux range. These findings underscore the potential of combining contraction before microchannels (CBM) and step gap above microchannels (SGAM) configurations to significantly enhance flow boiling stability and heat transfer performance while incurring a much lower pressure drop penalty.

Study on the flow and heat transfer characteristics of a hybrid nanofluid jet impingement microchannel heat sink with airfoil fins

AbstractDue to the continuously increasing power density of electronic devices, the improvement of the temperature uniformity and the reduction of the irreversible energy losses became crucial in these studies on enhanced cooling capacity of the heat sinks. In this paper, a jet impingement microchannel heat sink with airfoil fins (AF‐JIMHS) is proposed. The AF‐JIMHS with reversed fins arrangement has very high comprehensive heat transfer performance. The increase of the internal tangent circle radius and chord length of fin can improve the temperature uniformity of the AF‐JIMHS bottom surface and reduce the irreversible energy losses, at the expense of reducing its comprehensive heat transfer performance. Although the increase of the tangent arc length of fin reduces the temperature uniformity and increases the irreversible energy losses of the AF‐JIMHS, it improves the comprehensive heat transfer performance in a specific parameter range. The increase of fin height improves temperature uniformity of the AF‐JIMHS, while reducing its irreversible energy losses and improving its comprehensive heat transfer performance. Compared with the AF‐JIMHS with uniform height fins, the one with decreasing height fins has higher comprehensive heat transfer performance and lower irreversible energy losses. Moreover, the AF‐JIMHS with increasing height fins has better temperature uniformity.

Numerical investigation of tip clearance designs for oblique-cut fin microchannels

Tip clearance represents a simple design intervention strategy to mitigate the high hydraulic penalties often associated with microchannel heat sinks. This approach has not been widely explored for enhanced microchannel heat sinks, having previously focused only on conventional (uniform) tip clearance design for straight microchannels. In view of this, the present work investigates the performance of an enhanced heat sink, specifically oblique-cut fin microchannels, with tip clearance designs. Two different designs are considered, namely conventional/uniform tip clearance (utc) and a newly conceptualized modulated tip clearance (mtc). Numerical simulations are conducted using ANSYS FLUENT 2022 R1 first for straight microchannels, which are considered the baseline to which oblique-cut fin microchannel designs are compared. The simulations are carried out under laminar flow regime including conjugate heat transfer in a heated solid substrate for flow rates of 250 – 650 mL/min. The results indicate that utc significantly reduces pressure drop though can increase thermal resistance for the oblique channels. The underlying physical mechanisms responsible for this observation are elucidated by examining thermal and flow behaviours in and around oblique cut slots. Based on the flow behaviour in oblique slots with utc, modulated tip clearance (mtc) concept is introduced and investigated. When compared to utc cases, mtc tends to reduce the thermal resistance substantially, though depending upon oblique cut angle and flow rate. However, the Performance Index (PI) shows that utc improves the overall performance in the range of 10–15 % compared to that observed with mtc cases, though the factor of improvement reduces closely to 5 % at 650 mL/min. In addition, the overall performance in terms of heat transfer and hydraulic pumping power further show that utc and mtc design strategies are competitive, and warrant further multi-objective optimization investigations to determine the best design option overall.