Wall Temperature Research Articles

Energy conversion efficiency improvement studies on the hydrogen-fueled micro planar combustor with multi-baffles for thermophotovoltaic applications

In order to improve the energy conversion efficiency of micro thermophotovoltaic (MTPV) system, in this work, a micro planar combustor with multi-baffles is designed for thermophotovoltaic applications. Effects of baffle-to-sidewall distance, baffle-to-inlet distance, baffle length and baffle number on the performance of the micro planar combustor are numerically investigated. Results demonstrate that it is better to place the multi-baffles at the middle of combustion chamber for improving the total energy output and total energy conversion efficiency of MTPV system. However, it cannot be ignored that the pressure drop of micro planar combustor is greatly increased. Meanwhile, with the increment of baffle-to-inlet distance and baffle length, the outer wall temperature can be higher and more uniform. Furthermore, when the total length of baffles is a constant, more baffle number is good for obtaining higher outer wall temperature, as well as the total energy output and total energy conversion efficiency of the MTPV system can be improved.

Advanced modelling and optimization of steam methane reforming: From CFD simulation to machine learning - Driven optimization

Computational fluid dynamics simulations were utilized to investigate the steam methane reforming process with the aim to improve its efficiency. Key parameters examined for their impact on process performance included surface heat flux (73–108 kW/m2), tube length (1–16 m), steam-to-carbon ratio (1.4–4), and flow rate (0.22–0.38 kg/s). To analyze the simultaneous effects of these variables while reducing computational costs, Deep Neural Networks (DNN) were employed. An optimized DNN was designed to achieve acceptable performance, featuring an input layer with four neurons that represent reformer length, flow rate, heat flux, and steam-to-carbon ratio. The network includes four hidden layers with 32, 16, 8, and 8 neurons respectively, and concludes with an output layer comprising seven neurons for residual methane, water vapor, produced hydrogen, carbon dioxide, carbon monoxide, wall temperature, and gas outlet temperature. The results indicated that the proposed model achieved high accuracy, exceeding 99%, in predicting both training and test data. Following the DNN modeling, an optimization algorithm based on the random search method was developed. This algorithm searches a wide range of parameters to identify the optimal conditions for simultaneously maximizing hydrogen production and minimizing reformer length.

Effects of Heat Transfer on Combustion Characteristics in a Cylindrical Vortex Combustor

A vortex flows in micro/meso scale combustors for small-scale power generation play a crucial role in enhancing combustion efficiency and stability. They enhance mixing between fuel and air, promoting better combustion and help stabilize flames by maintaining consistent fuel-air ratios. The temperature are significantly impacts the reactant temperature due to heat conduction wall in Cylindrical Vortex Combustor (CVC). This phenomenon, known as preheating, occurs as the wall transfers heat to the reactants. ANSYS Fluent software is used for conducted a numerical investigation on a CVC. The combustor was characterized by a prescribed mass flow rate of 40 mg/s and an equivalence ratio (j) ranging from 0.5 to 1.5. Our analysis aimed to understand the combustion behavior within this confined geometry, considering factors such as heat loss and temperature behavior. The numerical findings indicate that elevated equivalence ratios correlate with the highest flame temperature in micro-combustion. Specifically, at an equivalence ratio of j=0.5, the flame temperature remains consistently low compared to the higher value of j=1.5. However, when accounting for wall temperature effects, the maximum flame temperature occurs at an equivalence ratio of j=1.3. The heat dissipation region is quite limited, especially at low equivalence ratio. In summary, heat transfer in cylindrical vortex combustors (CVC) contribute to reliable and efficient power generation, making them essential for portable energy systems.

Enhanced flow boiling by manipulating two-phase flow in Tesla channel heat sink using HFE-7100

Flow boiling of dielectric fluids in copper microchannel heat sinks is highly desirable for cooling large-sized insulated gate bipolar transistor (IGBT) power electronic modules. However, dielectric fluids present challenges in flow boiling because of their unfavorable thermophysical properties. These factors make it difficult to enhance critical heat flux (CHF) without precooling. To address this, we developed a large copper heat sink (10 cm × 5 cm) with Tesla microchannels designed to suppress vapor backflow and promote intense fluid mixing. The microchannels have a high length to hydrodynamic diameter ratio of approximately 220, significantly higher than those in previous studies. Flow boiling experiments using HFE-7100 were conducted for both Tesla and plain-wall microchannels. Tesla channels demonstrated a 26.2 % increase in CHF and a 120 % improvement in heat transfer coefficient (HTC). These enhancements are attributed to the vapor backflow suppression and improved fluid mixing. Moreover, the standard deviation of wall temperature in plain-wall microchannels was 10 times higher than in Tesla channels, highlighting the effectiveness of the periodic Tesla valves in reducing two-phase flow instabilities. Flow pattern visualization was conducted to further understand the mechanism behind vapor regulation, clarifying the role of Tesla valves in controlling vapor backflow. This study demonstrates the potential of dielectric fluids in Tesla microchannels for flow boiling applications, offering a promising solution for cooling large electronics.

Options for Implementation of IR Thermography Diagnostics in a Tokamak with Reactor Technologies TRT

AbstractOptions for implementing the IR thermography diagnostic system in a TRT facility are considered. Two variants of the optical scheme for measuring the temperature of the first wall and divertor targets are proposed: a wide-angle system combined with two divertor channels and a four-channel viewing system. The optical resolution of both systems and the levels of the collected signal are numerically simulated. On the basis of the calculations performed, conclusions are drawn about the compliance of the systems with the requirements for measuring the temperature of TRT plasma-facing elements. The sources of the temperature measurement error are considered, and the error caused by the reflection of radiation from structural plasma-facing elements by the surface under study is estimated. Calibration issues for IR thermography diagnostics are also discussed.

Transient heat transfer analysis of airflow in a thermal water-bearing tunnel considering airflow turbulence and surrounding rock seepage effects

In deep tunnels traversing fractured water-rich strata, surface water descend, heats up at depth, and then rises into the tunnel, resulting in a ‘thermal water-bearing’ tunnel. This paper investigates the transient temperature evolution of such tunnels through laboratory-scale model experiment and numerical simulation, considering the convective heat transfer of thermal water in the surrounding rock. The experimental model was designed using similarity criteria derived from the equation analysis method. The 3D numerical model simulates the interaction between thermal water-saturated surrounding rock and tunnel airflow. The thermal field of the surrounding rock accounts for the coupling effects of the flow field, which follows Darcy's law. The tunnel airflow is governed by the RANS (Reynolds-Averaged Navier-Stokes) equations and the k−ω turbulence model, combined with the LRNM (Low-Reynolds Number Modeling) method for near-wall treatment. This approach is coupled with the energy balance equation to calculate the airflow temperature. The numerical model is validated using monitoring data from experimental measurements of grouted tunnel wall and airflow temperatures. Finally, parameter studies are conducted for both ungrouted and grouted tunnels, demonstrating the effectiveness of grouting in controlling airflow temperature by blocking thermal water.

Influence of twist ratio of twisted tape turbulator on thermal and second law efficiency of spiral tube

This study aims to determine the effects of a spirally coiled tube paired with a twisted tape turbulator. The tube was maintained at a constant wall temperature, and the flow was considered to be turbulent. Effect of different flow rates has been studied in which the Reynolds number was ranging between 6000 and 52,000. The Reynolds number and twist angle of twisted tape are the main variables whose influence has been assessed on the heat transfer characteristics. It was observed that the twisted tape may totally change the hydrodynamics behavior of fluid in the spiral tube affecting both pressure drop and heat transfer. As a result of adding twisted tape the pressure drop ratio raised from 1.88 to 2.19 and the Nusselt number raised from 1.03 to 1.115. In order to evaluate both the heat transfer enhancement as a desired phenomenon and the pressure drop as an undesired phenomenon, the performance evaluation criteria (PEC) has also been studied. The amount of 0.868 was the highest PEC amount achieved through this method which indicates that the method has positive effect in enhancing the heat transfer characteristics. In order to better evaluate the proposed method, the White-Shamsundar efficiency has also been evaluated which considers both of the first and second law of thermodynamics simultaneously and reports the data based on both efficiencies of the first and second laws of thermodynamics.

Boiling critical characteristics in narrow rectangular channel under local heat flux concentration conditions

For the establishment of predicting method of local concentrated critical heat flux (CHF) in narrow rectangular channels, and also technical support for the preparation of long-life and high-performance dispersive plate fuel, this work simulates Dry-out type CHF under local concentration of heat flux condition by using Eulerian multiphase model and Enhanced near-wall treatment. The distribution of near-wall temperature and void fraction under different heat flux was calculated by Computational Fluid Dynamics (CFD) method. Dry-out CHF was predicted based on highly and quickly wall temperature rise. The influence of system pressure, mass flow rate and inlet subcooling degree were discussed on Dry-out CHF. Compared with uniform heating, the predicted average heat flux on CHF is lower under local heat flux concentration, and location of CHF is related to the position of heat flux concentration area. This work’s research method in Ansys Fluent could be applied to forecast Dry-out CHF in narrow rectangular channel under local concentration of heat flux condition.

Role of UeMsb2 in Filamentous Growth and Pathogenicity of Ustilago esculenta.

Ustilago esculenta is a dimorphic fungus that specifically infects Zizania latifolia, causing stem swelling and the formation of an edible fleshy stem known as jiaobai. The pathogenicity of U. esculenta is closely associated with the development of jiaobai and phenotypic differentiation. Msb2 acts as a key upstream sensor in the MAPK (mitogen-activated protein kinase) signaling pathway, playing critical roles in fungal hyphal growth, osmotic regulation, maintenance of cell wall integrity, temperature adaptation, and pathogenicity. In this study, we cloned the UeMsb2 gene from U. esculenta (GenBank No. MW768949). The open reading frame of UeMsb2 is 3015 bp in length, lacks introns, encodes a 1004-amino-acid protein with a conserved serine-rich domain, and is localized to the vacuole. Expression analysis revealed that UeMsb2 is inducibly expressed during both hyphal growth and infection processes. Deletion of UeMsb2 did not affect haploid morphology or growth rate in vitro but significantly impaired the strain's mating ability, suppressed filamentous growth, slowed host infection progression, and downregulated the expression of b signaling pathway genes associated with pathogenicity. Notably, the deletion of UeMsb2 did not influence the in vitro growth of U. esculenta under hyperosmotic, thermal, or oxidative stress conditions. These findings underscore the critical role of UeMsb2 in regulating the pathogenicity of U. esculenta. This study provides insights into the interaction between U. esculenta and Z. latifolia, particularly the mechanisms that drive host stem swelling.

Investigation on thermal response of high temperature heat pipe under thermal mismatch conditions

As an efficient and reliable passive heat transfer equipment, high temperature heat pipes (HTHPs) plays an important role in HTHP solid state reactor system. HTHPs often encounter thermal mismatch in reactor applications, which will lead to capillary action, entrainment, and other characteristics, resulting in HTHP failure due to heat transfer limits. In this paper, the thermal response test of liquid metal HTHP under thermal mismatch conditions is studied, and the simulation test platform of HTHP mismatch is designed and built to measure the important physical parameters. The test results show that the heat transfer performance of the HTHP is the best under the condition of horizontal inclination of 60°, and the condenser power is 5.66 kW. This condition is selected as the reference condition for the transient condition test. When the HTHP experienced a transient power increase, the middle of the evaporator section, as the part with the largest heat flux of heating power, appeared a severe overheating phenomenon. The wall temperature of the evaporator section soared from 750 ℃ to 1050 ℃ in a short time, and the heating rate reached 18.9 ℃/min, which affected the smooth operation of the HTHP. When the HTHP encounters an inclination angle transient increase condition, the entrainment phenomenon is more severe, the temperature fluctuation of the condenser section is intensified, and the heat transfer of the HTHP is in an unstable state. When the HTHP encounters an inclination angle transient decrease condition, the temperature rise of the evaporator section is less than 10 ℃, the temperature at the end of the condenser section is increased, and the start-up performance of the HTHP is improved. In summary, this paper obtains the thermal response rule of HTHPs under thermal mismatch conditions through experimental research, which provides support for the safe application of HTHPs for special equipment.

Development and experimental validation of a thermal inactivation model for airborne bacteria and its application in Trombe wall systems

Thermal inactivation technology is an effective and safe method to control indoor bioaerosols. A predictive mathematical model describing the effect of residence time and exposure temperature on the thermal inactivation process of Klebsiella pneumoniae (K. pneumoniae), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in aerosol was developed. A continuous flow experimental system was set up to determine the survival ratio of bioaerosols under the wall temperature of 45–120 °C and residence time of 1.5–12 s. The experimental results showed that the thermal stability in the order from high to low was S. aureus > K. pneumoniae > E. coli. The inactivation model was developed based on the first-order kinetic model and Arrhenius equation and the model parameters were identified through particle swarm optimization (PSO) algorithm with the input of time-dependent exposure temperature calculated by computational fluid dynamics (CFD). The survival ratio calculated by the present model corresponded well with that observed in the experiment, with root mean square error (RMSE) being 0.0445, 0.0433 and 0.0376 for K. pneumoniae, E. coli and S. aureus, respectively. Based on the heat and mass transfer model for Trombe wall, it was found that solar-driven thermal inactivation could reduce the indoor bacterial concentration by up to 57 % for E. coli with thermal efficiency being 0.424 under solar irradiance of 496 W/m2 and ambient temperature of 12.8 °C. In this way, solar driven thermal inactivation is a promising and sustainable method to deal with indoor bioaerosols.

Measurement of local condensation heat transfer coefficient (HTC) within a brazed plate heat exchanger (BPHE) and heat transfer assessment of low-GWP R134a replacements

This paper presents local condensation Heat Transfer Coefficients (HTCs) and temperature profiles of R134a and three low-GWP replacements, R1234yf, R1234ze(E), and R152a, within Brazed Plate Heat Exchangers (BPHEs). The measurement of local temperature profiles allows to couple the evaluation of thermal and hydraulic performances of refrigerants into a single parameter named Total Temperature Penalty (TTP). The experimentation was carried out in a prototype BPHE instrumented with thermocouples inserted into the plate wall to measure the local heat flux and wall temperature. The transition from gravity-controlled condensation to mixed condensation was observed in the refrigerant mass velocity interval 15−20 kg m−2s−1. The experimental HTCs were compared with existing theoretical models finding a Mean Absolute Percentage Error (MAPE) within 10–15 %. The TTP analysis highlights similar condensation performance for R134a, R1234yf and R1234ze(E) refrigerants, while R152a performs better than R134a.

Detailed thermo-hydraulic investigation of 3D octet lattice structure integrated heat sink

The present research work examined the thermo-fluidic characteristics of a heat sink packed with octet-structured periodic metal foam having varying porosity (0.83–0.93) and unit cell lengths (UCL) of 2.5–5 mm for electronic cooling application. AlSi10Mg material is considered for the octet lattice structure with water as the cooling medium, with the inlet velocity ranging from 0.02 to 0.05 m/s and a steady heat flux of 10 W/cm2 applied at base of the substrate. The effect of the porosity, unit cell length, and inlet velocity on pressure gradient, friction factor, Nusselt number, wall temperature, heat transfer coefficient, and thermo-hydraulic performance parameter is analyzed. Larger pressure gradients are observed for lower values of porosity and unit cell length, with a maximum value of approximately 5000 Pa/m for the thermal system having 0.83 porosity, 2.5 mm UCL, and 0.05 m/s inlet velocity. The wall temperature drops with a rise in inlet velocity and a reduction in porosity and UCL, with the lowest value of 311 K for the case of 0.83 porosity, 2.5 mm UCL, and 0.05 m/s inlet velocity. The case of 0.83 porosity, 5 mm UCL, and 0.02 m/s velocity was determined as optimum design based on thermo-hydraulic performance parameter.

Interaction between vapor bubbles during flow boiling heat transfer in microchannels

Microchannel flow boiling is an efficient cooling solution for high-power-density miniaturized systems. Many studies on microchannel flow boiling focused on the dynamics of single vapor bubbles, while neglecting the interaction between bubbles, which is important in relevant applications. Here, numerical simulations are carried out to study the interaction between multiple vapor bubbles in microchannel flow boiling. The results show that for different numbers of bubbles in the microchannels with the same initial size and position of leading bubbles, the bubble size in a single-bubble microchannel is larger compared to the leading bubble of multiple-bubble cases because of heat absorption by the vaporization at the rear bubbles. As the initial volume ratio between the leading bubble and the rear bubble decreases, the leading bubble size in the downstream becomes smaller because of the reduced contact with the superheated thermal boundary layer. With increasing the Reynolds number, both the leading and the trailing bubbles increase slightly in size in the upstream of the heated region, because the bubbles at higher Reynolds number move faster and firstly get in contact with the superheated fluid. The increase in the bottom wall thickness increases the growth rate of the multiple bubble sizes with earlier bubble coalescence because of the higher upstream wall temperature by heat conduction in the solid wall.

Predicting Leidenfrost Temperature and Effects of Impact Conditions on Droplet Size Distribution in Film-Boiling Regime

Abstract The interaction of a droplet with a solid wall is relevant in various engineering applications. The properties of the resulting secondary droplets are determined by the wall temperature, ambient pressure, impact momentum, and impact angle. This paper presents a comprehensive characterization of drop–wall interactions and the subsequent atomization as a function of the combined effects of such parameters. A drop–wall interaction model is derived for F-24 liquid fuel droplets using smoothed particle hydrodynamics (SPH). F-24 is a derivative of Jet-A aviation fuel with military additives, and it is the focus of this study due to its common use in military applications. The model can predict different impact outcome regimes (deposition, rebound, contact-splash, and film-splash) for different ambient pressures, wall temperatures, and impact parameters. The model also addresses the effect of ambient pressure on the Leidenfrost behavior. Size distributions of secondary droplets are compared for vertical and nonvertical impacts of F-24 droplets on superheated surfaces in the film-boiling regime. The nondimensional Sauter mean diameter (SMD) of the secondary droplets varies based on the position in the impact plane for all the nonvertical impacts but remains almost unchanged for vertical impacts. The zone of leading direction for nonvertical impact consists of larger secondary droplets, and the size decreases toward the zone of trailing direction. An empirical relation is proposed to represent this trend. This research sheds light on successive droplet impacts by studying the effects of impact frequency on SMD evolution. The results are compared to single droplet impact cases for different fuels and Weber numbers. The size of secondary droplets for successive impacts is observed to be nearly indistinguishable from that of single droplet vertical impacts.

Influence of inclined magnetic field on mixed convective cross flow across a cylinder with uniform heat flux condition

This numerical study delves into the interplay between inclined magnetohydrodynamic flow and mixed convective heat transfer in a cylindrical geometry under uniform heat flux condition. The study employs a quasi-static model, where the fluid is flowing in a cross-stream regime, satisfies the Boussinesq approximation. A higher-order finite difference scheme is adopted to discretize the non-linear Navier–Stokes and energy equations, followed by a stable pseudo-time iterative technique. This study reveals that a lower Richardson number and interaction parameter are sufficient to induce vortex shedding under positive magnetic angles that can not be achieved in case of aligned magnetic field. Increasing the strength of magnetic field tends to restore the symmetric flow structure from the buoyancy-driven asymmetric one, contingent upon the magnetohydrodynamic flow orientations. The coefficients of viscous and pressure drag, average Nusselt number become non-monotonic for the aligned magnetic field, whereas it becomes strictly monotonic for other positive magnetic inclination angles at each Richardson number. Interestingly, increasing magnetic inclination angle allows to augment the total drag coefficient and overall heat transfer drastically. Critical interaction parameter is determined for average Nusselt number at various Richardson and Reynolds numbers under aligned magnetic field. The heat transfer is significantly more enhanced under uniform heat flux condition compared to constant wall temperature condition. The enhanced heat transfer achieved through magnetic field integration and modified thermal conditions has significant potential for applications such as electronic cooling, solar collectors, material processing, and more.

Heat Transfer in Double Pipe Heat Exchangers With Small Tube Spacing

Abstract In this work, the heat transfer in double pipe heat exchangers (DPHEs) with small tube spacing is analyzed. This type of heat transfer is generally described in many literary sources; however, in laminar flow, the resulting values of the theoretical equations differ. Moreover, the small spacing of the pipes can affect the fluid flow and subsequent heat transfer. The suitability of using available theoretical methods for the design of double pipe heat exchangers (the Stephan, VDI, and Baehr methods) was evaluated. A series of experiments was carried out on a double pipe heat exchanger with a tube spacing of 1.4 mm. The experimentally determined value of the heat transfer coefficient (HTC) was up to two times higher in comparison with the values calculated according to theoretical methods. The relative increase was more significant for the lower Reynolds number values. At the same time, the difference of the wall temperature along the circumference of the outer tube was detected. This phenomenon was theoretically analyzed and can be explained by tube misalignment in the small tube spacing. The procedure of quantification of this effect was proposed. This effect may cause an inhomogeneity of the media flow and temperature distribution and, as a result, increase the performance of the heat exchanger by tens of percent.

Numerical Simulations of an Al2O3-Water Nanofluid-Based Linear Fresnel Solar Collector

This study aims to numerically investigate the performance of Al2O3-water nanofluid as a heat transfer fluid (HTF) in a linear Fresnel solar receiver. Although a reasonable number of studies have investigated the thermal behaviors of different nanofluids as HTF in solar collectors, the focus has so far been on the parabolic trough collectors, with little or no research efforts available for the linear Fresnel collectors. ANSYS-fluent software was utilized for the simulation in this study, which converted the governing equations to algebraic forms based on the control-volume approach. The Nusselt number and wall temperature were used to characterize the thermal performance of the nanofluid, while the friction factor and eddy viscosity were considered to determine the flow features. The correlation equation proposed by Gnielinski was used to determine the Nusselt number, while the flow features were computed using the Darcy-Weisbach equation. Additionally, the thermal performance of the nanofluid was compared directly with that of pure water. Results showed that the nanofluid improved the thermal performance by about 6-19 % across the solar receiver length. Also, the Nusselt number increases non-uniformly across the length, with a significant rise towards the trailing edge of the nanofluid flow. Conversely, the pressure drop also increases with an increase in the solar receiver length, albeit uniformly. Designers should always factor into the design process to determine the optimum solar collector length when a nanofluid is considered as the HTF; to maximize heat transfer and minimize pressure drop and its attendant economic consequences.

A semi-empirical model of frost formation on a cryogenic surface cooled from ambient temperature under forced convection condition

In most practical occasion, frost is formed on cold surface which is cooled from the ambient temperature. Although the initial cooling stage may account for a small proportion in the whole frosting process, the effects of the initial cooling on frosting characteristics could not be overlooked. In this paper, a semi-empirical model of cryogenic frosting involving the initial cooling process under forced convection is established by employing frost properties correlations and heat and mass balance analysis. The frost thickness calculated by the proposed semi-empirical model showed good agreement with experimental data within a maximum error of 15 %. Within the constraints of correlation validity, this model is applicable to conditions where ambient temperatures range from 10 °C to 30 °C, air flow Reynolds numbers span from 7 × 104 to 1.5 × 105, air humidity varies between 3.5 g/kg and 18 g/kg, and initial cooling durations extend from 15 min to 40 min, and the final wall temperature is decreased to about 80K. The results indicate that frost thickness increases with rising ambient temperature, air humidity, and airflow velocity. Notably, higher rates of frost growth are observed during the initial cooling under conditions of elevated air humidity or increased airflow velocity. The trend in frost mass closely mirrors that of frost thickness, however, a more pronounced increase in frost mass occurs with increasing ambient temperature. Furthermore, extending the duration of initial cooling could accelerate the frost growth rate and cause a higher frost surface temperature.

Experimental study of the flow boiling heat transfer characteristics of teardrop-like micro-pin-finned chip surface in semi-open microchannel

Phase change flow boiling heat transfer in microchannel is a very efficient thermal management mode for high-power electronics/devices. However, it is still a challenge to achieve comprehensive enhancement of flow boiling heat transfer performance at low power consumption. Herein, we devised and manufactured a set of teardrop-like micro-pin-finned chip surfaces, demonstrating their exceptional enhancement in flow boiling heat transfer efficiency within semi-open microchannels with negligible pumping energy input. Benefiting from the effective expansion area, the pinning effect and the streamlined bionic structure of the micro-pin-fins, the staggered teardrop-like micro-pin-finned surface (S37) exhibits simultaneous enhancement of critical heat flux (CHF) and heat transfer coefficients (HTC). The CHF and HTC peaks reached 414.1 W/cm² and 42,153.3 W/m²·K, with maximum enhancement ratios of 52.8 % and 78.1 % relative to the smooth surface. A nearly linear improvement in the heat flux (from 93.1 to 414.1 W/cm², enhanced by 447.8 %) is observed within a minimal fluctuation in wall temperatures, not exceeding 10 °C. The semi-open microchannels provide ample space for boiling nucleation bubbles to move efficiently, enhancing heat transfer performance while maintaining a very low pressure drop (≤1.2 kPa) and without increasing power consumption. In situ observation and analysis of the boiling bubble dynamics indicated teardrop-like micro-pin-finned chip promotes the phase change heat exchange process by massive nucleation sites, and effective control of boiling bubbles by pinning effect. These findings not only provide guidance for the rational design of boiling heat transfer-enhanced surfaces and heat sinks, but also point the way to achieving efficient thermal management of power devices.