Thermal Resistance Of Heat Pipe Research Articles

Development of a Freeze Resistant Heat Pipe with Water as Working Fluid for Automotive Applications

Abstract In this paper, we present a heat pipe with ethylene glycol and water as working fluid that can prevent any damage to the copper container on exposure to cyclic freezing and thaw. Different mass concentrations of water and ethylene glycol have been tested for freeze protection of heat pipes in this research. Experimental investigations have shown that 3.5% by mass concentration of ethylene glycol with water is able to sustain the cyclic freezing and avoid any damage to the copper pipe. For this research the freezing and heating cycle is set to operate between -40°C to 90°C. Heat pipes used for testing in this research are 6mm in diameter and 150mm long with copper fibre spiral wick. Thermal performance tests have been carried out on these heat pipes with charging ratio of working fluid varying between 10%-30% by volume. It is observed that the thermal resistance of heat pipe with working fluid charging ratio in range of 10%-25% by volume varies from 0.6°C/W-0.2°C/W for the rate of heat transfer of 10W-50W. While the charging ratios beyond 25% have shown the higher thermal resistance in the range (0.8-1.0°C/W) for similar rate of heat transfer. Accelerated life tests are performed on these heat pipes for up to 500 hours and have not shown any signs of degradation in its thermal performance.

Heat transfer performance of high-temperature heat pipe startup in small heat pipe reactors

High-temperature heat pipe is an important heat transfer component in small heat pipe reactors (SHPR). Research on the transient heat transfer characteristics during heat pipe startup is crucial for safety analysis of SHPR. This manuscript investigates the startup performance of a lithium heat pipe from the frozen state with various influencing factors, including heating power, inclination angle, and convection heat transfer coefficient. The objective of this work is to speed up the heat pipe startup process in a safe and economic manner based on its heat transfer characteristics. In order to illustrate the startup characteristics and further to reduce the startup time, this manuscript constructs a CFD heat pipe model via the multi-physics simulation software, COMSOL. The phase change process of heat pipe startup is described by the Phase Change Material method, with the fluid velocity and pressure fields of wick established using the Brinkman equation. Results show that the heat pipe thermal resistance decreases with increasing heating power, positive inclination angle, or convection heat transfer coefficient. On the other hand, the heat pipe startup time reduces with increasing heating power, increasing positive inclination angle, or decreasing convection heat transfer coefficient. Moreover, numerical analysis indicates that heat pipe temperature rises faster in the evaporation section than in the condensation section at the beginning of startup. Temperature rise process in the condensation section occupies the majority of the entire heat pipe startup process. Therefore, to speed up the startup process, this work proposes a novel extra heating method applying to the condensation section at early startup. Compared with the conventional startup, the proposed method is able to shorten the startup time by 10.5 % and 15.8 % with an extra heating power of 10 % Full Power (FP) and 20 %FP respectively.

Experimental and analytical investigations on heat transfer performance of naphthalene heat pipe heat exchanger

The heat transfer performance of a naphthalene heat pipe (HP) heat exchanger (HE) was theoretically analyzed and experimentally confirmed. The tested HE comprised a staggered 9 × 17 array of copper tubes with 144 U-bends, forming a closed loop. The working fluid was naphthalene with a filling ratio of 45 %. The operating temperature range was 80–300 °C, and the airflow rate was 100, 150, 200, or 400 m3/h. The maximum heat transfer rate was discovered to be 3.86 kW, and the HP thermal resistance was approximately 0.00553 K/W for an air flow rate of 100 m3/h and at an operating temperature of 300 °C; the maximum thermal conductivity was 7155.43 W/m·K. The experimental data were compared with the predictions of empirically derived equations; the best predictions were obtained when the Jouhara and Robinson correlation for condensation was combined with the Kutateladze correlation for evaporation. The mean deviations of the predictions were 36.05 % for the overall thermal resistance and 17.34 % for the average temperature difference between the evaporation and the air side. Although the thermal conductivity of the naphthalene HP was much lower than that of a water HP, it improved as the temperature increased; hence, naphthalene HPs are effective for high-temperature heat recovery.

Transient recovery from heat pipe dryout by power throttling

Heat pipes and vapor chambers are passive heat spreaders driven by capillary pumping of an internal working fluid via a porous wick. The capillary limit is the maximum steady-state heat input at which the fluid pressure drop can be supported by the capillary pressure head generated in the wick. However, heat pipes and vapor chambers often find application in devices where the heat input is highly transient and can exceed the capillary limit for brief time intervals. Operating heat pipes briefly above the capillary limit will not result in a dryout if the operating time interval does not exceed a characteristic time-to-dryout. Operation over a duration that exceeds this time-to-dryout can induce transient dryout and may lead to thermal hysteresis, that is, the original heat pipe thermal resistance may not be recovered even after the heat input is lowered back below the capillary limit. To fully recover the heat pipe performance after a transient dryout event, our recent experiments have shown that the heat input must be lowered (or throttled) significantly below the capillary limit. Due to the highly transient nature of power dissipation from electronic devices, it becomes imperative to characterize the throttling power level and duration required to ensure full recovery of a heat pipe from dryout under transient operations. This work experimentally characterizes recovery of heat pipes from dryout by power throttling under transient conditions, where ‘power throttling’ is the act of reducing the operating power level significantly below the capillary limit to eliminate post-dryout thermal hysteresis. We deduce from the experiments that the power must be throttled for longer than a minimum throttling time interval, defined as the time-to-rewet, in order to eliminate dryout-induced thermal hysteresis. The dependence of this time-to-rewet on the throttling power level is explored, and guidelines are presented on the need for throttling and the choice of throttling power under transient conditions.

Numerical simulation and optimization of heat pipes using nanoparticles: a feasibility study

This study investigated the effect of different particle sizes on the thermal effectiveness of a cylindrical screen mesh heat pipe using silver nanoparticles as the test substance. The study compared the effects of three different particle sizes (30, 50, and 80 nm) on heat transmission characteristics of the heat pipe. The results showed that the heat pipe’s thermal conductivity increases as the particle size decreases. The thermal conductivity measurements revealed 250 W/mK, 200 W/mK, and 150 W/mK for particles of 30, 50, and 80 nm sizes. Furthermore, the study analyzed thermal resistance of heat pipe for each particle size and found that as particle size decreases, thermal resistance decreases as well. The heat transfer coefficient values for particle sizes of 30, 50, and 80 nm were found to be 5500 W/m2K, 4500 W/m2K, and 3500 W/m2K, respectively. The ANOVA method was used to analyze the results statistically. The 30 nm particle size was found to have significantly higher thermal conductivity, lower thermal resistance, and a higher heat transfer coefficient than other particle sizes. Additionally, simulations were conducted to analyze the temperature variation of the hot source as a function of power dissipation for design and optimization.

A novel neural network and sensitivity analysis method for predicting the thermal resistance of heat pipes with nanofluids

It is critical to accurately predict the heat transfer performance of heat pipes with nanofluids for the design of the thermal management system. The current prediction models for the thermal performance of heat pipe with nanofluids are mostly developed based solely on their experimental data, resulting in poor universality and low predictive performance. Moreover, there is a lack of quantitative analysis of the correlation degree of selected input parameters on the thermal performance of heat pipe. The innovation of this work lies in the development of a novel thermal resistance prediction model based on neural network and sensitivity analysis method, characterized by a broad range of inputs and high accuracy. Firstly, a neural network database was established based on our own experimental data and published literature. The effects of the learning rate and the number of nodes in the hidden layer on the prediction performance were investigated. Subsequently, the Garson algorithm was used for sensitivity analysis of the input parameters. The results showed that when the Adam adaptive optimization algorithm and 28 nodes in the hidden layer were used, the neural network model had the highest prediction accuracy, with a mean square error (MSE) of only 0.0020 and a mean absolute error (MAE) of 0.03 K/W, and a mean relative error (MRE) of 7.86 %, demonstrating that the developed model can be used for predicting the performance of heat pipes. The ranking of the influence of each input variable on the thermal resistance from high to low is as follows: heat load, confinement number, inclination angle, cold source temperature, filling ratio, thermal conductivity, and concentration. Moreover, the influence of concentration on the accuracy of the model cannot be ignored. This work provides a direct guidance for developing a performance prediction model for heat pipe with nanofluids with high universality and accuracy.

Enhancements of heat transfer and thermoelectric performances using finned heat-pipe array

Phase change materials (PCMs) are highly promising for heat storage and passive cooling due to the combined advantages of high latent heat and selectable phase-change temperature, whereas suffer from the defect of low thermal conductivity. However, limited improvement of thermal conductivity of phase change materials (PCMs) by flat fins has severely restricted the cooling and latent heat release rates of PCMs. Moreover, previous literature has seldomly focused on the application of exhausted heat or PCM-stored latent heat. Confronted with above issues, we experimentally demonstrated a new enhancement regime for both phase-change heat transfer and thermoelectric power using PCM embedded with heat-pipe (HP) array instead of traditional fins. Results indicated that adding HP array significantly enhanced the phase-change of PCM with the wall temperature reduced by 51 ℃ compared with pure PCM. Moreover, the maximum vertical and horizontal temperature gradients were less than 1.5 ℃ and 2.5 ℃ due to the small thermal resistance of HPs. TEG power with single HP was nearly four times higher than that with three HPs, whereas at the expense of 20 ℃ increment in wall temperature. PCM convection contributed 20 ℃ of wall temperature drop, but reduced the thermoelectric power.

EXPERIMENTAL STUDY ON IMPROVING HEAT TRANSFER ABILITY OF A HEAT PIPE UTILIZING IRON OXIDE-FERRIC OXIDE HYBRID AND NICKEL FERRITE MONO-MAGNETIC NANOFLUIDS

Heat carrier refining of a heat pipe employing the iron oxide-ferric oxide hybrid magnetic nanofluid and nickel ferrite mono-magnetic nanofluid as an operating medium in the process of various performing conditions was investigated experimentally. A thermosyphon-type heat pipe constructed of copper with 20-mm internal and 18-mm external diameters was used in this experimental work. The fulfillment of the heat pipe was examined by operating three separate operating fluids: distilled water, hybrid and mono-magnetic nanofluids. The fluid was injected into the system with a filling ratio equal to 1/3 of the total volume of the heat pipe for all individual experiments. Practical analysis was performed under three distinct input heats and two different nanofluid weight percent as an operating medium in the evaporator section and three different coolant mass flow rates in the condenser area of the system. Wall temperature fluctuations, index factor (efficiency), Nusselt number, and thermal resistance magnitudes were obtained for distilled water, iron oxide-ferric oxide hybrid magnetic nanofluid, and nickel ferrite mono-magnetic nanofluid for each experiment. The highest improvement rates in heat transfer ability, Nusselt number, and heat pipe thermal resistance magnitude were 30.55%, 26.9%, and 61.8%, respectively, when the iron oxide-ferric oxide hybrid magnetic nanofluid was employed as an operating fluid compared to distilled water. The thermal performance of the system increased significantly with increasing the weight percent of both hybrid and mono-magnetic nanofluids. Basically, the efficiency of the system was improved by 3.92% by increasing the weight percent of the hybrid magnetic nanofluid from 0.5 wt.% to 1 wt.%.

Experimental investigation, CFD and theoretical modeling of two-phase heat transfer in a three-leg multi-channel heat pipe

Muti-channel flat heat pipe is an innovative technology recently used at the rear of photovoltaic cells to absorb and reuse the wasted heat. To better understand the fundamentals of two-phase heat transfer (boiling and condensation) taking place inside multi-channel heat pipes, a unique three-leg heat pipe has been built. This one-of-a-kind heat pipe was used to develop both computational fluid dynamic (CFD) and theoretical models of a multi-channel heat pipe. To simulate the heat pipe operation with ANSYS Fluent, the Volume of Fluid (VOF) approach and Lee model were investigated. Different types of Lee models using user defined function (UDF) were compared and the influence of the condenser's boundary condition, saturation temperature, and mass transfer coefficient on the simulations was studied. For the first time, major limits of the Lee model for the simulation of heat pipes are identified. It is concluded that the available Lee model cannot predict the heat pipe temperature as it shows low physical meaning and can easily be manipulated to adjust the simulation's results. Based on the three-leg heat pipe experimental data, a new multi-channel theoretical model was developed that uses the thermal-electrical resistance analogy to predict the three-leg heat pipe thermal resistance. By selecting the optimum correlations for pool boiling and filmwise condensation, the developed iterative theoretical model was able to predict the three-leg heat pipe thermal resistance with an error of 8.2%.

유도가열을 이용한 히트파이프 작동유체 주입에 대한 연구

The heat pipe is a device that effectively transfers heat through phase-change of the internal working fluid, and is a two-phase closed system. A general heat pipe is fabricated by maintaining a vacuum state on the inside and then injecting a working fluid that has undergone a degassing process. Such a degassing method has no problem in fabricating individual heat pipes but requires more time to manufacture heat pipe heat exchangers that require many heat pipes. Therefore, the present research proposed a method of manufacturing a heat pipe by using induction heating that can be heated to a degassing temperature in a short time and compared thermal performance with a heat pipe fabricated by the existing method. This study conducted numerical analysis and experiments using 5/8 in and 1 in diameter copper pipes. The error was found to be up to 7%; however, the trends between numerical analysis and experimental data were almost consistent. Based on the numerical analysis results, induction heating manufactured heat pipes under conditions of 90 V and 32 A. In addition, thermal resistance was measured, similar to the thermal resistance of heat pipe fabricated by the conventional degassing method. The manufacturing method by induction heating was validated by comparing thermal resistance with the existing method. It is expected that the manufacturing time of heat pipes can be meaningfully reduced and applied to the manufacture of heat pipes under various conditions using numerical analysis.

The effects of particle mass fraction and static magnetic field on the thermal performance of NiFe2O4 nanofluid in a heat pipe

In this study, experimental investigations are performed in order to determine the thermal performance of NiFe2O4 nanoparticles dispersed in deionized water in a thermosyphon-type heat pipe. The effects of the magnetic flux density and nanoparticle mass fraction were analyzed at different heat inputs and cooling water flow rates. The magnetic field was generated by the current-carrying solenoid. Our results indicated that the use of NiFe2O4 nanofluid significantly improves the thermal performance of the heat pipe which also showed that the enhancement of heat transfer coefficient can be obtained with increasing mass fraction and in presence of a low parallel magnetic field. A decrease of 26.6% was achieved in the temperature difference between the evaporator and the condenser regions compared to distilled water at a 3% mass fraction and under a magnetic field. The maximum improvement in heat pipe's thermal resistance was found as 30.4%, through NiFe2O4 nanofluid usage under magnetic field. Compared to base fluid, the application of magnetic nanofluid and parallel magnetic field reduces the thermal resistance, increases heat pipe efficiency and the heat transfer coefficient.

Experimental Investigations on Performance Analysis of a Wickless Thermosiphon Heat Pipe With Two Heat Sources and Multiple Branches

Abstract In an electronic circuit of laptops, supercomputers with multiple central processing units, spacecraft etc., it is required to arrange the cooling system for multiple heat loads in the smallest possible space in view of power-saving opportunities. In the present study, the experimental investigations are carried out on a wickless multi-branch heat pipe in gravity-assisted mode with two evaporators and one condenser on each of the individual branches. The start-up and dynamic characteristics were studied with different filling ratios (range, 40–70%), with equal heat loads (range, 0–200 W) and unequal heat loads (range, 0–100 W) on evaporators. The results are analyzed in terms of temperature variation in axial direction, thermal resistance, and heat transfer coefficient for a multi-branch thermosiphon heat pipe (MBTHP). It was found that the optimal filling ratio depends on the applied heat load under tested conditions. In a thermosiphon mode, the heat pipe was capable of transporting a maximum heat load of 210 W and maximum heat flux of 20.31 W/cm2 with the maximum evaporator temperature lower than 100 °C. The minimum wickless thermal resistance of heat pipe was found to be 0.21 °C/W at 50% filling ratio and 160 W and maximum total heat transfer coefficient was found as 6.33 k W/m2 °C.

Experimental and theoretical investigation of the influence of heat transfer rate on the thermal performance of a multi-channel flat heat pipe

Recently, flat heat pipes have been proposed for surface cooling applications to passively extract and recover thermal energy from hot surfaces. For instance, flat heat pipes have recently been proposed as thermal absorber for photovoltaic/thermal (PV/T) applications or for the thermal management of batteries. Following promising surface cooling results, increasing the fundamental knowledge of the two-phase heat transfer taking place inside such multi-channel flat heat pipes can participate to its widespread and lead to further improvement of the technology. Indeed, until now, the investigations have focused on the application only and not on the performance of the flat heat pipe itself. In this regard, this manuscript experimentally and theoretically investigates the thermal performance of a multi-channel flat heat pipe used for surface cooling applications. Heat transfer rates in the range 0–1500 W are studied and their impact on the boiling, condensation, and total thermal resistance of the multi-channel flat heat pipe is measured. In order to predict the thermal performance of the multi-channel flat heat pipe at all heat transfer rates, a theoretical model is proposed, which considers the impact of the multi-channel geometry. This model uses a multi-channel thermal resistance network. Furthermore, an important number of two-phase correlations for pool boiling and condensation are compared with experimental data and the optimum equations are integrated into the multi-channel model. As a result, over the whole range of heat transfer rates investigated, the proposed multi-channel flat heat pipe model was able to predict the boiling, condensation, and total thermal resistances of the heat pipe with an average error of 17.2%, 14.4% and 13.1%, respectively. Finally, the impact of the tilt angle is also studied, and infrared imaging of the flat heat pipe surface is presented.

Experimental investigation of heat pipe thermoelectric generator

Thermoelectric generators can generate electricity directly from low-temperature energy sources, such as solar and geothermal energy. Because of the low heat flux of the heat source, heat pipes are used to increase the hot end temperature of the thermoelectric module, and thus improve its conversion efficiency. We developed a heat pipe thermoelectric generator and quantitatively studied the effects of the heating power of the heat pipe evaporator and the number of modules used in the condenser, on the thermoelectric performance, heat transfer characteristics, and temperature uniformity of the generator. As the heating power increased, the heat pipe thermal resistance decreased, and the thermoelectric conversion efficiency increased. As the number of thermoelectric modules increased, the proportion of heat pipe thermal resistance increased and became dominant, which caused the hot end temperature of the modules to decrease. The system attains maximum efficiency when there is only a single module at the condenser. The temperature of the evaporator can be effectively increased to improve the output power. When the temperature of the evaporator remained constant, increasing the number of modules reduced the temperature of the hot end slightly, however, the output power was greatly improved, and the maximum output power reached 10.85 W with four modules used in the experiment. The non-uniformity of the module output performance was obvious at a low heat flux, and the module output power was high near the evaporator. These results contribute to understanding the working characteristics of heat pipe thermoelectric generators and provide some guiding significance for the optimization of generator operations.

Thermal performance evaluation of the heat pipe by using 1-pyrene carboxylic-acid functionalized graphene nanofluid

The experiments are conducted to characterize a low-cost nanofluid and evaluate its effect on the sintered-wick heat pipe efficiency. Stable aqueous dispersions of 1-pyrene carboxylic acid (PCA)-functionalized graphene nanofluid were used to investigate the heat transfer characteristics in a sintered wick heat pipe. The various parameters being investigated include different fluids (concentration range from 0.01 to 0.06 mass%), tilt angles of the heat pipe (0 ͦ to 90 ͦ), and input powers (60 W, 80 W, 100 W, and 120 W). The result shows the enhancement of thermal conductivity of nanofluids are in the range of 21% and 40% as concentration and temperature were increased. It is found that the tilt angle of heat pipe has a substantial impact on the thermal properties, which could enhance the thermal performance by 79%. The experimental results indicated that the heat pipe thermal resistance is reduced using these nanofluids. The reduction in thermal resistance was the best at the high heat flux. The most considerable enhancement on overall heat transfer coefficient was achieved at 0.06 mass% by 13.9 kW/K.m2.

Experimental investigation of heat pipe performance under translational acceleration

Heat pipes provide highly efficient heat transfer and are powerful tools in thermal management systems. In contrast to most established systems, heat pipes operating within moving systems such as electric vehicles or machine tools are exposed to unsteady acceleration forces. In order to guarantee proper heat pipe function in scenarios involving accelerated movement, it is necessary to examine the effect of acceleration forces on the heat pipe behavior. This paper presents experimental investigations on the thermal performance of translationally moving heat pipes. The designed experimental set-up consists of a measurement platform mounted to a linear direct drive. By obtaining the temperature gradient between evaporator and condenser section, the thermal resistance of heat pipes is determined at standstill and under linear motion. The experiments were conducted using heat pipes with sintered, mesh and grooved wicks. The results demonstrate the motion influence on the thermal resistances depending on the heat pipe orientation and heat input.

An advanced conduction based heat pipe model accounting for vapor pressure drop

Heat pipes are passive heat transfer devices which play an increasingly important role in state-of-the-art cooling solutions for various technologies like consumer electronics or electric machines. During design phase, reliable simulation results are the key for optimal performance and efficiency. In system level simulations, heat conduction models, characterized by low computational effort, are widely used to predict heat pipe thermal resistance. In order to accurately calculate overall thermal characteristics, a precise prediction of the vapor core’s temperature drop is crucial. In this study, a novel conduction-based method for calculating heat pipe performance is presented. Taking velocity components perpendicular to the main vapor flow into account, an analytic expression for calculating the axial pressure gradient is developed and validated through detailed CFD simulations. Assuming saturation conditions, results are used to determine the vapor core’s local effective thermal conductivity. Parameters needed for calculation are provided for both circular and flat heat pipes under various operating conditions. The final model accounts for phase change thermal resistance and temperature dependent fluid properties. The presented method yields significantly different results compared to state-of-the-art approaches in which thermal vapor resistance is either assumed to be zero or calculated assuming (Hagen-)Poiseuille flow. Simulation results suggest a strong dependence of vapor thermal resistance on evaporation and condensation mass fluxes, thermophysical fluid properties and local vapor temperature.

A Experimental and Numerical Approach to Evaluate Thermal characteristics a of Heat Pipe

Nanofluid as working fluid for the improvement of thermal performance, in case of heat pipe, is the newly emerging area of research. Superior thermal characteristics of nanofluids attracted the researchers towards the application of nanofluid in heat pipes. In present study, a 2D analysis is applied to evaluate the thermal performance of heat pipe having CeO2/H2O nanofluid. The heat transfer analysis of heat pipe having nanofluid (0.5, 1.0, &1.5 wt. % concentration) at operating temperature of 60, 80, 100,& 120°C has been done numerically through CFD simulation and results was compared with the experimental results. The results predicted by numerical analysis show that the application CeO2/H2O nanofluid diminishes the temperature of surface wall and thermal resistance of heat pipe as compared to that of water. The efficiency as well as effective thermal conductivity of the heat pipe increased with the use of CeO2/H2O nanofluid as compared to that of water heat pipe. A good agreement has been observed between experimental and numerical results. The present study concludes that heat pipe using CeO2/H2O nanofluid as working fluid has better heat transfer characteristics than the water.

Thermal Resistance of Cascade Heat Pipe as CPU Cooling System to Maintain Safe Temperature for Computer

Computer will overheat quickly if used in a state of full load continuously. One component on a computer that generates heat is the central processing unit (CPU) which is a key component on a computer where program instructions are processed. One of the right solutions to cool the CPU is the use of heat pipes as cooling system, using several size container, loaded with a special liquid liquid to deliver the heat from the evaporator zone to the other end called condenser zone, but because the heat pipe condenser output temperature is still high therefore a cascade heat pipe was created to lower the output temperature. In this study there are four CPU cooling systems used namely single condenser cascade heat pipe and a double condenser cascade heat pipe, while others two cooling systems as a comparison namely non-cascade heat pipe and non-cascade heat pipe with fan. This study aims to find out the cooling performance of cascade heat pipe as CPU cooling system in a small form factor desktop PC by testing variations in workload, the workload given is idle load (12W) where the processor only runs the operating system without the software load so the processor utilization is only 1% -10%. Next is the medium load (30W) that uses 2 threads with processor utilization of 50% -90%. The last workload is full load (35W) with the number of threads used being 4 with processor utilization of 90% -100%. This research found that the thermal resistance of the cascade heat pipe tended to be higher than that of the non-cascade heat pipe, however the increase that occurred was not too large compared to the resulting performance of 60.2°C in the processor and 40.4°C in the heat sink for the cascade double condenser, the operating temperature of the CPU does not increase significantly as the thermal resistance increases on the cascade heat pipe.

Analysis on start up and heat transfer performance of mercury heat pipe under alternating heating power

Heat pipe may be affected by the high temperature heat source during operation, resulting in unsteady oscillation heating. In this paper, the influence of alternating power and period on the start-up and heat transfer performance of mercury heat pipe is studied by using the method of equivalent thermal resistance of heat pipe. The results are as follows:1) The start-up time of alternating power heating and steady-state power heating is basically equal; 2) For the alternating power heating, the steady-state temperature of heat pipe changes periodically, increasing the alternating period or the amplitude of alternating power will lead to the increase of the fluctuation amplitude of heat pipe temperature, and the influence of alternating period is greater than that of changing the amplitude of alternating power. 3) Under the condition of alternating power heating, the steady-state thermal resistance of heat pipe changes periodically. The fluctuation amplitude of steady-state thermal resistance of heat pipe increases with the increase of alternating period and alternating power amplitude, and the influence of alternating power amplitude is greater than that of alternating period.