Thermal-hydraulic Characteristics Research Articles

Modeling and Simulation Analysis on Mixing Characteristics of Two-Phase Flow Around Spacer Grid

The spacer grid has a significant impact on the thermal-hydraulic characteristics of the rod bundle channel, which directly determines the possibility of a boiling crisis. The multi-phase flow model coupling boiling model is proposed to acquire the secondary flow and void fraction for subcooled flow boiling in the fuel assembly. Compared with the experimental data, the RNG k–ε turbulence model is selected in the current research. In addition, the thermal-hydraulic parameters of subcooled boiling flow in the 5 × 5 rod bundle with a spacer grid are studied focusing on the influence of different arrangements of mixing vanes. It is found that the distribution of the vapor phase is greatly influenced by the intensity and flow direction of secondary flow. In addition, the thermal–hydraulic characteristics in the sub-channels and around the fuel rods are investigated, which demonstrates that uniform crossflow makes vapor harder to accumulate around the fuel rods. Furthermore, the mixing characteristics of different types of spacer grids are also discussed in detail.

Numerical Study on Thermal-Hydraulic Performance of Printed Circuit Heat Exchangers during Natural Gas Trans-Critical Liquefaction

Printed Circuit Heat Exchangers (PCHEs) are considered an excellent alternative for the main cryogenic heat exchanger of Floating Liquefied Natural Gas (FLNG) facilities due to their compact structure and strong heat transfer performance. However, it is unclear how to configure the geometry of the PCHE channels to achieve its optimal performance in the trans-critical liquefaction process of natural gas (NG), which is critical for the main heat exchanger. In this paper, we numerically studied the thermal-hydraulic characteristics of PCHEs with different channel types under the specified condition. The results elucidate that all channels have an enhancement of heat transfer near the pseudo-critical point of NG. All the wavy channels could improve the heat transfer performance of PCHEs, where the trapezoidal channel achieves the largest promotion. Compared with the straight channel, the local heat transfer coefficient could be increased by up to 53% in the trapezoidal channel. Additionally, vortex appeared at the bends of the wavy channels, which greatly increase the local friction loss. Among several channels, the total pressure drop of zigzag, fillet and the sinusoidal channel was almost the same, while that of the trapezoidal channel was the largest. Furthermore, we compared the comprehensive performance of different types of channels and found that the benefit of heat transfer enhancement could not offset the penalty of flow deterioration. Our work provides important guidance for the design of PCHEs employed in FLNG.

Experimental study on thermal hydraulic characteristics of natural circulation loop under motion condition

• Comparatively studied thermal hydraulic characteristics of natural circulation loop under various motion conditions. • Obtained the periodic average frictional resistance coefficient and Nu. • Obtained the empirical relation of frictional resistance coefficient in turbulent region. • Under large flow rate conditions, rolling motion affects heat transfer characteristics mainly by affecting flow rate. • Some suggestions on the layout of marine natural circulation loop were given. In this present paper, an experimental research was carried out to investigate the influence of various motion conditions on the flow and heat transfer characteristics in natural circulation loops. A natural circulation loop was built on the six-degree-of-freedom motion experiment platform at Xi’an Jiaotong University (XJTU). First, it was found that the small acceleration heaving would not cause significant changes on flow rate of the natural circulation loop. Then, the influence mechanism of rolling motion on the natural circulation loop is different as the central axis of rolling is changed. The increase of additional inertial force along the coolant flow direction causes larger flow fluctuation. The periodic average frictional resistance coefficient under different working conditions is obtained, which is divided into flow fluctuation region ( Re < 5000) and turbulence region (5000 < Re < 35000). Last, according to the experimental data, a mathematical model to predict the periodic average frictional resistance coefficient which is suitable for the turbulent region is obtained, and the deviation between the predicted value and the experimental data is less than 20%. Beyond that, the period average Nu under different working conditions is also achieved. It shows that the rolling motion promotes the heat transfer with the small flow rate, while the rolling motion affects the heat transfer characteristics mainly by affecting the flow rate under the large flow rate conditions. Based on our research, some suggestions on the layout of marine natural circulation loop were given.

Thermal hydraulic characteristics of silicon irradiation in a typical MTR reactor

Abstract In this work, a three-dimensional study is conducted for silicon ingot irradiation facility in a typical MTR reactor. The silicon ingot heat generation is allowed to change around its nominal value in the range of 0.25, 0.5, 0.75, 1.0, and 1.25 W/g. The dimensionless clearance ratio ζ between the ingot and the outer casing is changed for values of 0.01, 0.05, 0.1, 0.15, and 0.2. The computational fluid dynamics code ANSYS FLUENT is employed to carry out these calculations. The temperature profile inside the silicon ingot during irradiation is of significant importance for uniform doping. Therefore, the impact of Rayleigh number and dimensionless clearance ratio ζ on the radial and axial temperature profiles through the ingot is reported. A best estimate correlation for the silicon irradiation facility global Nusselt number in terms of Rayleigh and dimensionless clearance ratio is presented. The dimensionless clearance ratio ζ value of 0.05 gives the best thermal hydraulic performance. Comparison with the available experimental correlations in the literature shows good agreement.

Numerical study on thermal-hydraulic characteristics of flattened microfin tubes

Abstract The thermal-hydraulic characteristics and performance of the circular and flattened straight tubes with longitudinal inward microfins are studied with isothermal wall condition and Reynold numbers (Re) between 10,000 and 30,000. The geometric models with fins (8, 12, and 16 fins) and three flattening ratios (1.4, 2, and 3.4) are considered for the simulation. The results indicate that the longitudinal microfins have a limited effect on the improvement of heat transfer, but the application of microfins increases the pressure drop significantly. Furthermore, an increase in Reynolds number increases the heat transfer characteristics. Therefore, a discriminative use of longitudinal microfins for circular tubes to improve thermal performance is advised. Flattening the microfin tubes has shown a significant increase in heat transfer coefficient and friction factor compared to circular cross-section tubes with microfins. The percentage gain in heat transfer with the flattening ratio of 3.4 is about 52% compared to the circular fin tube at Re = 30,000. A 61% increase in centreline velocity is observed at Re = 10,000. Area-based Enhancement Factor (AEF) and performance evolution factor (PEF) are more than 1 for flattened tubes with microfins. It shows an improvement in the overall thermal-hydraulic characteristics of tubes.

Separate-effect drainage tests in a core make-up tank

Passive safety systems are widely used in the advanced nuclear reactors, such as AP1000 and CAP1400. As an important component in the passive safety system, the core make-up tank (CMT) plays a key role for the safety injection and the core decay heat removal. Although the structure of the CMT system is simple, it involves many thermal-hydraulic phenomena, most of which significantly impact the peak temperature of the fuel cladding and the liquid level of the core. Since the CMT not only provides full-pressure injection but also triggers the auto depressurization system by its liquid level signal during small-break loss of coolant accident (SBLOCA), its thermal hydraulic behaviors significantly affect the performance of the passive core cooling system (PXS). Therefore, separate effect tests are inevitable to verify the feasibility of CMT applied to passive safety and injection systems and to study its operating characteristics. In this work, a separate-effect CMT test facility was designed and constructed. Experiments were performed to investigate the CMT's thermal hydraulic characteristics under the effects of system pressure, steam condensation, and flow friction. The study found that the delay drainage phenomenon is the result of a pressure balance between the pipe line and the gravity head. Whether delayed drainage occurs depends on the degree of subcooling of the fluid at the top of the CMT. The flowrate is not affected by the heat transfer coefficient of steam direct contact condensation. The flow friction of the drainage pipeline has no effect on the delayed drainage process, but has a great influence on the gravity drainage process.

CFD investigation on thermal-hydraulic characteristics of a helical cruciform fuel bundle

The thermal-hydraulic performance of nuclear fuel has a very important effect on the safety and economy of a reactor. The helical cruciform fuel (HCF) is an innovative fuel design with a lot of potential advantages. HCF assembly is a self-supporting assembly. It needn't spacer grid which is usually used in the cylindrical fuel assembly. It has larger surface-to-volume ratio in comparison to the cylindrical fuel, which can increase the power output without necessarily altering the operating surface heat flux. In this research, the thermal-hydraulic characteristics of a 4 × 4 HCF bundle were investigated by numerical method. A numerical model of the bundle was developed and validated with experimental data. Based on this model, five flow conditions were respectively calculated. The transverse flow in the HCF bundle was analyzed, and the temperature distributions of the bundle and the water were discussed. The results show that the transverse mixing of water in the bundle is enhanced due to the helical geometry of the HCF rod. The mixing intensity periodically varies with twist angle increasing, and every twist angle of 90° is a variation cycle. The temperature distribution on the rod surface helically varies along the flow direction, and the temperature in the valley region is obviously higher than that in the lobe region. Additionally, the water temperature in the back of the lobe is higher than that in the front of the lobe.

Numerical investigation of heat transfer and flow resistance characteristics of interpenetrated flying-wing finned tubes

In the present study, three possible interpenetration modes named vertical insertion, horizontally staggered shift, and streamwise staggered shift are proposed to improve the compactness of the flying-wing finned tube heat exchanger. Also, the effects of these modes on heat transfer and flow resistance characteristics of the finned tubes are numerically analyzed in the Reynolds number range of 1500–3000. It was found that a large vertically embedded depth (Lv), which in the present study has a maximum value of 3.4 mm, creates an acute-angled slit in the fin gradual contraction region. This slit weakens the convective heat transfer. However, the flow resistance characteristic is improved to a certain extent with increasing Lv. It was also found that the monotonous characteristic curves obtain a local inflection point in the range of 2.35–3.05 mm of Lv. An equivalent insertion coefficient is proposed to simplify the comparison of heat transfer rate (Φ). When the envelope size of the heat exchanger core, finned tube number, and pressure drop (Δp) are fixed, the overall thermal-hydraulic characteristics (Φ versus Δp) of the interpenetrated flying-wing finned tube heat exchanger are most significantly improved with Lv equal to 2.7 mm by 6.5% on average. Finally, two interpenetration correction factors are proposed to quantify the effect of interpenetration on the thermal-hydraulic characteristics.

Thermalhydraulic comparison of supercritical fluids in minichannel heat sink to assess the suitability of macroscopic scaling rules

Suitability of supercritical fluids as heat transport media in mini-/microscale has not been explored much, despite showing enormous potential in macrochannels. One major hindrance thereof is the absence of scaling rules devised specifically for such scales. Present numerical study explores the thermalhydraulic characteristics of five different supercritical fluids, identified based on the diversity in their respective critical-point parameters, for a particular minichannel employing a conventional set of scaling relations. Supercritical fluids exhibit consistently-superior heat transfer coefficient compared to single-phase, and even boiling, channels. Substantial level of similarity has been observed in the visual nature of the dimensionless momentum and thermal fields and local recirculation patterns across the fluids, as a consequence of the imposed scaling. Noticeable difference, however, exists in characterizing dimensionless groups, such as local Reynolds number and local and area-averaged Nusselt number, pointing toward the deficiency of the scaling model. R134a can be earmarked as the optimum fluid among the considered ones, both in terms of Nusselt number and dimensionless pressure drop, though it experiences the largest entropy generation as well. It is suggested to consider the profiles of Prandtl number and dimensionless thermal conductivity with dimensionless enthalpy for improving the used scaling rules.

A Numerical Study on Heat Transfer Enhancement and Fluid Flow of Enhanced Tube With Ellipsoidal Dimples and Protrusions

Abstract Heat transfer enhancement is an important thermal–hydraulic phenomenon in heat exchangers. Previous investigations mostly focused on unidirectional heat transfer enhancement inside the tube. In order to realize the bidirectional heat transfer enhancement inside and outside the tube, an enhanced tube with ellipsoidal dimples and protrusions is proposed. Through comparison among three computational conditions, the non-conjugate and periodic condition is adopted in this paper. Flow characteristics and heat transfer performance of the enhanced tube are investigated by numerical method. The distributions of temperature and flow fields are carried out to illustrate the heat transfer enhancement mechanisms. The Nusselt number, friction coefficient, and performance evaluation criteria (PEC) are presented to reveal thermal–hydraulic performance. Moreover, the effects of the geometric parameters such as dimple depth, dimple pitch, dimples/protrusions numbers in the circumference, and arrangement mode on thermal–hydraulic characteristics are investigated. The results show that the structure of dimples and protrusions induces intensive impingement and interrupts the boundary layers, improving the heat transfer for the internal and external flow, respectively. Besides, the Nu increases with depth and dimples/protrusions numbers in the circumference and decreases with the pitch in most cases. The overall heat transfer performance of staggered arrangement is better than that of aligned arrangement. For the present parameter conditions, when D = 2 mm, P = 25 mm, n = 6, and Re = 5000, the largest PEC of 1.40 and 1.42 occurs for the internal and external flow, respectively.

Numerical investigation on thermal–hydraulic characteristics in a mini-channel with trapezoidal cross-section longitudinal vortex generators

The stringent requirement and rapid increase in heat dissipation for the high heat flux devices have brought great challenges to cooling performance of mini-channel heat sink (MCHS). Longitudinal vortex generator (LVG) is an effective technology for heat transfer enhancement in MCHS. It remains unclear, however, what effects of LVG cross-section on the thermal–hydraulic characteristics of MCHS are. Herein, a new mini-channel with trapezoidal cross-section LVGs is designed, as well as the effects of front width (a), back width (b) and height (h) of trapezoidal cross-section LVG on local and overall thermal–hydraulic characteristics are explored at the Reynolds number (Re) of 347–868 using numerical simulation method. As results, comparing with rectangular cross-section LVG, trapezoidal cross-section LVG mostly brings better thermal performance, and trapezoidal cross-section LVG with a > b generally performs better comprehensive performance. The best comprehensive performance can be achieved as h equivalents to half of channel height. The recommended optimal parameters are a = 0.6 mm, b = 0.3 mm and h = 0.75 mm to obtain the best comprehensive performance, yielding the maximum performance evaluation criterion (PEC) of 1.756 at Re = 543. Furthermore, comparing to previous studies with LVG, the PEC in present study is better at studied range of Re. Overall, the trapezoidal cross-section LVG as a new and effective technology with optimal parameters is conducive to heat transfer enhancement and comprehensive performance improvement in MCHS.

Optimization of the coupling groove parameters of composite porous vapor chamber

The recently developed composite porous vapor chamber (CPVC) with central and radial grooves shows small thermal resistance and good thermal performance under high heat fluxes. However, the groove parameters are difficult to optimize due to their coupling relationship and the lack of sound scientific ground. This paper addresses the issues by proposing an optimization method based on design of experiments (DOE) and response surface methodology (RSM) with the help of a developed decoupling strategy. In this method, a decoupling strategy inspired by the golden section rule is proposed to break the coupling relationship between groove parameters. Then DOE and RSM analyses are performed to provide data for single-objective and multi-objective optimization of groove parameters. Results indicate that, due to the decoupling strategy, the total number of sampling points is reduced by about 40% and the ratio of effective sampling points is increased by about 65.43% in DOE analysis. The influence of the groove parameters is nonmonotonic, and groove depth (T) has the greatest effect on the thermal hydraulic characteristics of CPVC, while the influence of central circular diameter (D) and groove width (W) is similar. The effect trend of the number of grooves (N) is contrary to that of W at small values due to the dramatic decrease of W. The thermal hydraulic performances can not reach the minimum or maximum value simultaneously, and the groove parameter configuration of D = 29 mm, W = 3.7 mm, T = 2.1 mm and N = 16 can be chosen as the optimal, leading to the decrease of the maximum temperature and the maximum temperature difference on the condensing surface, and the liquid pressure drop by 0.005 K, 0.015 K and 9.68%, respectively, compared with the initial design. The proposed method may pave a more objective and scientific alternative to design the structural parameters of CPVC.

Numerical investigation of a plate-type steam generator for a small modular nuclear reactor

A numerical feasibility study was conducted to investigate the thermal–hydraulic characteristics of a steam generator with corrugated plates for a small modular reactor. Accordingly, a one-dimensional thermal–hydraulic analysis code was developed based on the existing state-of-the-art thermal–hydraulic models and correlations for corrugated plate heat exchangers. Subsequently, the pressure loss, heat transfer, and instability characteristics of the steam generator with corrugated plates were investigated according to the chevron angle and mass flux. Additionally, the characteristics of rectangular and disk-type corrugated plate steam generators with equivalent heat transfer areas were analyzed. The steam generator with disk-type corrugated plates exhibited better performance in terms of pressure loss and heat transfer rate than the rectangular type. In addition, when the mass flux decreased from the onset of boiling points, reverse gradients of the total pressure change were observed in both types. Thus, it was confirmed that Ledinegg instability could occur in the steam generator with corrugated plates. However, it was dependent on the chevron angle, and the optimal chevron angle to minimize instability was 45° under the conditions of the present analysis.

Research on Thermodynamic Characteristics of Hydraulic Power Take-Off System in Wave Energy Converter

Hydraulic power-take-off (PTO) systems which utilize high-pressure oil circuits to transmit energy are widely applied in wave energy generation. The properties of hydraulic oil are significantly influenced by environmental conditions, and its dynamic viscosity is sensitive to temperature, especially in relatively low-temperature cases. This paper studies the characteristics of the hydraulic PTO when started in different temperature conditions via numerical analysis and experimental verification. An improved numerical model of the hydraulic PTO system is proposed, in which the effects of temperature on the hydraulic oil viscosity and hydraulic motor efficiency are quantitatively investigated, and consequently, the thermal-hydraulic characteristics can be sufficiently considered. The performances of the hydraulic PTO in start-up processes with different initial temperatures and in long term operation are assessed. The results show that the presented model can reasonably describe the hydraulic PTO characteristics. The efficiency of hydraulic PTO degrades when it starts at low temperatures. The efficiency increases in relatively high temperature, while larger fluctuations of the flow rate and output power are observed. This study can provide guidance for enhancing the efficiency and consistency of hydraulic PTO operating in actual sea conditions.

Numerical study of blowdown period of double-end break loss of coolant accident in PWR based on RELAP5

Loss of coolant accident (LOCA) is one of the most severe accidents of nuclear power plants (NPP). During the early blowdown period, the system is in a high-pressure gradient and high-velocity gradient state. Therefore, the hydrodynamic forces and safety analysis are highly related to calculating thermal-hydraulic parameters in the flow field. This paper studied the factors and modeling methods that affect the calculation of thermal-hydraulic characteristics under large break LOCA conditions. Firstly, the reactor core and primary system of a typical two-loop pressurized water reactor (PWR) NPP is modeled using the system analysis code RELAP5 Mod4.0. The normal operation state is obtained after the steady calculation. Then, transient calculation of double-end break LOCA is implemented considering the effects of break opening time and the pressurizer. The influence of the results on the calculation of hydrodynamic force has also been analyzed. Finally, the modeling method of reactor pressurized vessel (RPV) downcomer is presented. It is found that the flow field can be better simulated when the downcomer is modeled with parallel channels and several transverse junctions. Thus, this paper provides meaningful suggestions for modeling and simulation in the early blowdown period under LOCA conditions and contributes to further hydrodynamic load calculation and reactor safety analysis.

Experimental and numerical analyses of thermal-hydraulic characteristics of aluminium flying-wing fins

• In general, the flying-wing fin performs better than the wavy fin at the same Re . • The field synergy of the flying-wing fin is much better than that of the wavy fin. • There exist the butterfly-shaped low velocity zones perpendicular to the streamwise direction. • The heat transfer coefficient on the obtuse-angled side of the fin is larger. • Both fin length and fin thickness have little effect on the performance of the fin. The secondary heat transfer surface of the shovel-cut finned tube, called the flying-wing fin, eliminates the thermal contact resistance. In the present study, the thermal-hydraulic characteristics of the flying-wing fin at Reynolds number range of 1500–3000 were studied, including overall quantitative analysis and three-dimensional thermophysical field analysis. It was found that the ratio of Nu · η 0 / f 1/3 of the flying-wing fin (Case A1) is about 8.6% larger than that of the wavy fin (Case B3). The fundamental reason is that the flying-wing fin has a smaller average field synergy angle than the wavy fin. There is a butterfly-shaped low-velocity zone at the root of the wave trough of the monitoring section on the acute-angled side of the flow channel. In addition, along the fin height direction, the influence range of this low-velocity zone on the flow field is less than around 1.34 mm. Similarly, there are butterfly-shaped zones for the temperature and field synergy angle distributions. The average value of the convective heat transfer coefficient on the left side of the flying-wing fin is greater than that on the right side. In general, the promising flying-wing fins show better thermal-hydraulic performances than the wavy fins with similar geometric parameters, which deserve further promotion and engineering application.

Numerical investigation on thermal-hydraulic characteristics of the micro heat sink with gradient distribution pin fin arrays and narrow slots

Targeting at decreasing the pressure drop in the micro heat sink, a gradient distribution pin fin arrays and narrow slots (GPN) is proposed. In addition, in order to further reduce the pressure drop of the micro heat sink, three improved are proposed, including GPN48, GPN2244, GPN264 by changed the number and position distribution of the pin fin arrays in the narrow slots. The results show that the pressure drop of the three improved gradient distribution pin fin arrays and narrow slots decreases by 28.7%–33.4% at a certain volumetric flow rate (Qv = 120 ml/min, Re = 563) when comparing with the conventional gradient distribution. Furthermore, when Re ranged from 188 to 1125, the maximum wall temperature of the three improved gradient distribution pin fin arrays and narrow slots decreases by 4.4 K–26.6 K when comparing with the gradient distribution (GPN). When the Re = 563, the heat flux limit of GPN is only 82 W/cm2, while GPN48, GPN2244 and GPN264 reached 109 W/cm2, 114 W/cm2 and 120 W/cm2 respectively. Especially, comparing with GPN, the average heat transfer coefficient of GPN48, GPN2244 and GPN264 increases by 11.9%–23.0% (Re = 118), which greatly improves the application reliability in the micro heat sink.

Heat transfer enhancement of ferrofluid flow in a solar absorber tube under non-uniform magnetic field created by a periodic current-carrying wire

A novel configuration for heat transfer enhancement in parabolic trough solar collector absorbers by the use of a ferrofluid and an external magnetic field generated by a current-carrying wire is analyzed using numerical simulation. This new configuration consists of a wire which varies its position periodically along the tube. The analysis is focused on the study of the thermal hydraulic characteristics, Nusselt number and friction factor, and the average flow patterns in the turbulent flow regime (15·103⩽Re⩽250·103). In addition, different parameters of the periodic wire are analyzed: wire pitch and position angle. Ferrofluid Fe3O4/Therminol 66 is considered for this application. Firstly, the effect of an increase on the magnetic field intensity is studied. The periodic wire configuration shows a higher increment of the Nusselt number in comparison to the straight wire for the same magnetic field increase. The results reveal that the presence of a non-uniform magnetic field generates a disturbed flow with a high velocity region near the current-carrying wire. The periodic wire configuration leads to a spatially-periodic behavior that increases the average Nusselt number and the friction factor, in comparison to a straight wire. Among the studied cases, the position angle θ=30° and the pitch length l=3D are found to provide the maximum Nusselt number (Nu = 244.25 for Re = 15000).

Development of Conceptual Lead Cartridge Design to Perform Irradiation Experiments in VTR

This paper seeks to introduce the latest design of the Extended Length Test Assembly–Cartridge Lead (ELTA-CL) with associated thermal-hydraulic (TH) assessment and related experiment activities to support the critical component development performed by the ELTA-CL team (Los Alamos National Laboratory, Westinghouse Electric Company, and the University of New Mexico). The goal of the ELTA-CL program is to develop and validate an experimental capability to perform irradiation experiments in the Versatile Test Reactor (VTR) addressing Lead Fast Reactor (LFR) technology gaps, in support of the commercial development of advanced lead-cooled fast reactor concepts. Through a design maturation process and parametric study, a conceptual design is proposed to meet the requirements for material and corrosion testing. Thermal-hydraulic characteristics for the conceptual design at desired operating conditions are assessed with systems-level (one-dimensional) and computational fluid dynamics (three-dimensional) simulations. Along with the conceptual design work, experimental activities for the development of critical components such as the pump and flowmeter are undertaken. From both the modeling study and the experimental results, the design requirements of the Phase 1 ELTA-CL (e.g., 500°C and 2 m/s) are achievable with the current conceptual design. Additional design improvements and safety assessments at both steady-state and transient conditions for the final ELTA-CL design will be pursued.

Volume of fluid-based numerical analysis of a pump-driven phase change heat transport device

We numerically studied the thermal-hydraulic characteristics of a pump-driven two-phase (liquid–vapor) heat transport device. The volume of fluid (VOF) method was adopted to capture the liquid–vapor interface, and the temperature recovery method was used to estimate heat and mass transfer due to the phase change. First, we tested our model on two-dimensional film boiling and condensation problems. The numerical heat transfer coefficient results for the film boiling and condensation problems agreed well with Klimenko's and Nusselt's correlations, respectively, confirming the reliability of our model. Further, the effect of pressure difference in the flow channel on the heat transport performance of the device with phase change was investigated. In the case of a small pressure difference, the working fluid underwent a complete phase change and became superheated or subcooled. Conversely, increasing the pressure difference led to vapor plug thinning and liquid film thickening (around the vapor plug), which suppressed heat transfer via phase change.