Performance Of Pulsating Heat Pipe Research Articles

Experimental investigation on heat transfer and flow patterns of pulsating heat pipe assisted by ultrasonic cavitation

As an active enhanced method, ultrasonic cavitation could evidently improve the heat transfer efficiency of the Pulsating Heat Pipe (PHP). In this work, the influences of ultrasonic and nanofluid on the heat transfer performance of PHP were conducted and analyzed. First, the full visualization experiment was conducted with a high-speed camera to obtain the more detailed flow patterns of PHP. Then, the relative position and instantaneous velocity of vapor bubble was captured to describe the change of flow pattern and the movement of working fluid. Finally, the effects of SiO2H2O nanofluid with different concentrations (0.5 wt%, 1.0 wt%, 1.5 wt% and 2 wt%) with or without ultrasonic were experimentally investigated. The results reveal that the instantaneous velocity and driving force of working fluid are increased with the power of ultrasonic, and the startup time of PHP can be shortened simultaneously. Moreover, the microjet produced by the collapse of cavitation bubble and cavitation oscillation could promote the dispersion of nanoparticles. Thus, the heat transfer performance of high concentration nanofluid PHP is improved. The work would provide useful inspiration for further development and application of PHP with ultrasonic.

Heat transfer and flow visualization of pulsating heat pipe with silica nanofluid: An experimental study

As heat transfer device with two-phase flow, pulsating heat pipe (PHP) has a widely application prospect in the fields of improving energy efficiency and thermal management. In order to optimize the heat transfer performance of PHP, a visualization experiment was carried out with a high-speed camera, and detailed characteristics of flow pattern variations in nanofluid PHP were obtained. The effect of SiO2-H2O nanofluid with different concentrations (0.5 wt%, 1.0 wt%, 1.5 wt% and 2.0 wt%) were experimentally investigated to analyze the thermal performance of PHP. Results demonstrate that the addition of nanoparticles on the one hand promotes the phase transition of the working fluid in the PHP, and on the other hand increases the instantaneous velocity and the driving force of working fluid. These are all benefit for the reflux of condensed liquid and effectively avoid the phenomenon of ′dry out′. Additionally, the results also indicate that there exists an optimum concentration of dispersed nanoparticles in base fluid to enhance heat transfer. The maximum heat transfer enhancement efficiency with nanofluid concentration of 1.0 wt% can reach 40.1 % at the heating power of 50 W. The present results can provide useful inspiration for the development and application of new type pulsating heat pipe.

The effect of some metal oxide nanocomposites on the pulsating heat pipe performance

Increasing the performance of heat exchangers is one of industry’s most pressing challenges. Pulsating heat pipes (PHPs), as a novel technology with high-performance, are broadly used in solar distilled water and systems solar water heaters. In the present work, the impact of three nanofluids including zirconium dioxide (ZrO2), bismuth ferrite (BiFeO3)/ZrO2 (ZBF), and ZrO2/SiO2 composites under concentrations of 0.25, 0.5, and 1.0 g/L was investigated on the PHPs performance. The thermal resistance of the base fluid and the produced nanofluids was compared under a constant filling ratio of 50% and different input powers to the evaporator. The obtained results revealed that the use of working fluid such as nanofluids increased the heat transfer of PHPs in comparison to the base fluid and reduced the thermal resistance. Among the nanofluids used, the concentration of 0.25 g/L of the prepared nanocomposites provided the best performance. The resistance of the PHPs at some fluxes was reduced by up to 40%. In general, from the point of view of materials engineering, the structure of compounds used in nanofluids should have low thermal resistance, high thermal conductivity, and low viscosity. From a chemical point of view, using metals and compounds with high thermal conductivity is essential due to significant electron exchange.

Transient Numerical Model on the Design Optimization of the Adiabatic Section Length for the Pulsating Heat Pipe

In the application of pulsating heat pipes (PHPs), the lengths of the adiabatic sections are usually determined by the distance between the heat source and the heat sink, and have important effects on the performance of PHPs. However, there was little research on the effect of the adiabatic section lengths on the performance of PHPs. In this work, a new transient numerical model was proposed to investigate the transient flow and the heat transfer for PHPs with various adiabatic section lengths of 60, 120, 180, and 240 mm. Based on the numerical results, the flow and the heat transfer characteristics of the PHPs were analyzed. It was found that the flow velocities in the PHP with different adiabatic lengths increased with the increase in the heat input, and the mean velocity was calculated to be in the range of 0.139–0.428 m/s, which was consistent with the previous experimental results. The start-up performance of the PHP was better with shorter adiabatic section length. Furthermore, the thermal resistances of the PHPs with different adiabatic section lengths were calculated to analyze the effects of the adiabatic section length on the performance of the PHP. The results showed that when the heat input was 20 W, the PHP with the adiabatic section of 60 mm showed the lowest thermal resistance, whereas the PHP with longer adiabatic section length presented lower thermal resistance at high heat input (≥25 W).

The impact of ZrO2/SiO2 and ZrO2/SiO2@PANI nanofluid on the performance of pulsating heat pipe, an experimental study

The impact of ZrO2/SiO2 and ZrO2/SiO2@PANI nanofluid on the performance of pulsating heat pipe, an experimental study

Study of Thermal Performance of Closed Loop Pulsating Heat Pipe using Computational Fluid Dynamics

Abstract: Pulsating heat pipe is a heat transfer device which works on two principles that is phase transition and thermal conductivity which transfer heat effectively at different temperatures. Different factors affect the thermal performance of pulsating heat pipe. So, various researchers tried to enhance thermal conductivity by changing parameters such as working fluids, filling ratio, etc. Analysis of heat transfer characteristics of closed loop pulsating heat pipe (CLPHP) is to be carried out by using Computational Fluid Dynamics. The CLPHP is to be modelled on ANSYS Workbench, the flow of CLPHP is to be observed under specific boundary conditions by using ANSYS Fluent software. Acetone and Water are taken as the working fluid with 70% filling ratio at ambient temperature 30° C and the heat flux of 200 W is supplied at evaporator. Also, the analysis has been done to know the behaviour of PHPs under varying supply of heat flux at evaporator (inlet), the output heat flux is obtained at condenser (outlet) and find out how the heat flux is varying at different temperatures. CFD results shows the heat transfer characteristics observing the performance of CLPHP is a numerical manner. The obtained CFD results are compared with the experimental. The outputs of the simulations are plotted in graphs and outlines. Keywords: Closed Loop Pulsating Heat Pipe, CFD, Heat Transfer, ANSYS.

Simulation and experimental validation of pulsating heat pipes

• Numerical model improvements for the thermal performance prediction of pulsating heat pipes. • Model validation with new experimental data for vertical and horizontal orientation. • Flow behavior analysis on the simulated results. The one-dimensional transient numerical code of JJ Cooling Innovation has been significantly improved to simulate the thermal/hydraulic performance of pulsating heat pipes (PHPs). Using a mechanistic approach, the liquid slug and vapor plug flows and their interaction with the surrounding wall are modeled. The heat transfer is predicted using the Three-Zone Model of flow boiling in microchannels, which includes liquid film evaporation and liquid film condensation of vapor plugs and convection of liquid slugs. Discretizing the entire PHP serpentine into one continuous grid, the code solves all variables based on local conditions. The code allows the user to define the working fluid, the channel’s shape, material and wall roughness, the serpentine’s pitch, the geometrical parameters of evaporator, adiabatic region and condenser zones, and the operating parameters. The boundary conditions in the evaporator zone can either be constant heat flux or constant temperature, while on the condenser side, the coolant temperature is constant as well as the heat transfer coefficient. The code works without any fitting factor and predicts all local variables in the 1D grid as a function of time, including the liquid film thickness and the onset of boiling for the formation of new vapor plugs within the evaporating and adiabatic zones, if local nucleation conditions are reached. Growth, collapse and coalescence of generated bubbles are taken into account. The film thermal resistance is corrected to a radial conduction model. The implementation of the initial liquid film thickness laid behind a liquid slug is updated to include the effect of the bubble velocity and acceleration as well as the length of the leading slug. The nucleation of new vapor plug has also been updated. The onset of nucleation is only dependent on the local thermodynamic state. If the threshold is reached, a new method is used to simulate micro-bubbles formation and coalescence to a channel-size vapor plug. These modifications greatly improve the code accuracy and stability allowing simulations with high pressure fluid rather than ethanol only. Furthermore, in the on-going EU project Pulsating Heat Pipes for Hybrid Propulsion Systems (PHP2), a new PHP test bench has been designed and built at Provides Metalmeccanica. A copper tube PHP with a 19-turn of 2.0 mm internal diameter and 12 mm tube pitch was tested over a wide range of imposed heat loads. A microchannel water-cooling plate was used at the condenser side with an inlet temperature of 20 °C. Then, tests were done for vertical and horizontal orientations with R1233zd(E) as the working fluid. The code, which was previously validated for ethanol PHP test data from KAIST, is now successfully validated for the present experimental data points. Accurate results were obtained from low heat loads up to 250 W for a set of 49 data points, predicting 97% within an error bandwidth of 30%.

Experimental and numerical analysis of heat transfer and fluid flow characteristics inside pulsating heat pipe

Heat pipes are a popular choice for many industries and research applications to extract heat effectively by maintaining desired device/location at almost isothermal conditions. Pulsating heat pipes, also known as wickless heat pipes, transfers the heat mainly by pumping phenomenon caused by the phase change which set the pulsating vapor-fluid motion. The evaluation of fluid flow and heat transfer characteristics inside the pulsating heat pipe is complex and challenging due to the oscillating two-phase flow between the heat source and heat sink sections. In this paper, a numerical investigation of the closed-loop pulsating heat pipe is performed to study the fluid flow dynamics and evaluate its thermal characteristics. The volume of fluid method is employed to numerically simulate the two-phase unsteady incompressible flow inside the pulsating heat pipe. The heat pipe tube has a 2 mm inside diameter filled with methanol as a working fluid at a preset pressure. The thermal performance of pulsating heat pipe is evaluated for various heat pipe filling ratios (50%, 65%, and 75%) where heat input loads of 5 − 15 W are supplied at the evaporator end for each filling ratio case. The thermal characteristics of the pulsating heat pipe are presented in terms of the thermal resistance, heat transfer coefficient, and effective thermal conductivity, whereas fluid flow dynamics are presented as flow patterns produced inside pulsating heat pipe. The numerical simulations are compared and validated with experimental results. From the present numerical and experimental study, a filling ratio of 65% is an optimized charge quality for the current configuration of the pulsating heat pipe.

The impacts of utilizing nano‐encapsulated PCM along with RGO nanosheets in a pulsating heat pipe, a comparative study

Heat pipes are useful devices in heat transfer and particularly, in cooling systems. Given the high demand for cooling systems in various applications, an improvement in the performance of heat pipes has gained much attraction in recent years. In this study, the effects of utilizing working fluids with different thermal properties on the performance of pulsating heat pipes (PHP) are experimentally studied. Hence, nano-encapsulated phase change material (NPCM), reduced graphene oxide nanosheets, and their mixture, as a novel hybrid nanofluid, are prepared and dispersed in water as a working fluid. NPCM at 3 concentrations of 5, 10, and 20 g/L, as well as nanosheets at three concentrations of 0.3, 0.6, and 1.2 g/L, are synthesized and investigated. Moreover, both additives are mixed at five various concentrations to form a hybrid nanofluid. All experiments are conducted in the vertical orientation and filling ratio of 50%. It is found that due to the increase in viscosity with the increment of concentration, the highest concentration is not always the optimum concentration and the PHP's performance for each additive is optimized in a specific concentration. NPCMs could prevent the working fluid's temperature to rise by changing the phase, as a result, the effective specific heat of the working fluid is slightly augmented. Also, the thermal conductivity of the working fluid increased up to 13% using nanosheets. It is illustrated that using the mixture of nanosheets and NPCM leads to a 38% decline in thermal resistance. Meanwhile, it is found that the enhancement in the thermal performance of the PHP using nanofluids is not only purely due to the increase in thermal properties of nanofluids but also due to the increase in turbulence intensity and boiling nucleation sites created by the nanoparticles. Highlights Nano-encapsulated phase change material (PCM), reduced graphene oxide (RGO) nanosheets, and their mixture are used as working fluid in a pulsating heat pipe (PHP). The thermal performance of PHP is improved using PCM nanocapsules, RGO nanosheets, and their mixture. Nanosheets have a higher impact on the performance of PHP compared with nano-encapsulated PCM. The better performance of PHP using RGO nanosheets is due to the higher thermal conductivity and mixing of fluid containing them compared with pure water. The better performance of PHP using nanocapsules is attributed to the better mixing of the fluid.

Investigation of the effects of miscible and immiscible binary fluids on thermal performance of pulsating heat pipes

Present paper reports and discusses experimental results related to thermal and flow characteristics of asymmetrical designed flat plate closed loop pulsating heat pipe charged with miscible and immiscible binary fluids. Extensive experimental range is provided for a comprehensive analysis; which covers different binary mixing ratios (H:P, M:H and P:M = 1:1, 1:4 and 4:1) and inclination angles (0° and 90°). The filling ratio is kept constant as 50 %. H, P and M represent hexane, pentane and methanol, respectively. Results of pure fluids are also compared to binary ones, and all the processes are qualitatively analyzed via high speed visualization. It is concluded that methanol is the best choice among pure fluids; however, results completely changed when two fluids are mixed. Strongly depending on mixing ratio, immiscible binary mixtures show significantly better thermal performance compared to both the miscible binary one (H:P) and pure fluids. In this regard, optimum thermal characteristics are obtained with immiscible mixture of P:M = 1:1. On the other hand, increasing volume fraction of methanol in pentane-methanol mixture adversely affects thermal characteristics; and even, the poorest thermal performance is presented by the mixture of P:M = 1:4. Bubble dynamics and relevant flow patterns play critical role on heat transport phenomenon.

Experimental investigation of higher alcohols as self-rewetting fluids in closed loop pulsating heat pipes

Heat recovery plays an important role in all energy systems. The dissipation of heat is drastically increasing due to the advancement of electronic components. To cool the electronic components many heat recovery devices are introduced and out of which heat pipes play an important role. Pulsating heat pipe is a new type of heat transfer device which was introduced by Akachi in mid-1990. It is used mainly in the cooling of electronic components because of its potential for removing high heat flux. An experimental study was made to investigate the heat transfer performance of pulsating heat pipe using self-rewetting fluids of high carbon alcohols. The latent heat of vaporization plays an important role in the heat transfer performance of pulsating heat pipe. It was observed that the high carbon alcohols showed a decrease in the latent heat of vaporization. The high carbon alcohols such as 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol were mixed with the deionized water to form a self-rewetting fluid. These self-rewetting fluids showed a unique behavior due to the inverse Marangoni effect. It was observed that the lower thermal resistance and higher heat transfer coefficient was obtained, especially in the dilute aqueous solution of 1-octanol.

Heat transfer enhancement in pulsating heat pipe by alcohol-water based self-rewetting fluid

In the present paper, the heat transfer enhancement parameter is investigated experimentally for a four turns pulsating heat pipe (PHP) designed in a vertical orientation and made of copper (ID 1.30 mm, OD 2.20 mm and total length 1940 mm) for working fluids selected as deionized water (DIW) and 0.1 wt% hexanol in place of self- rewetting fluid (SRWF) at filling ratios (FRs) 10, 50, and 90% and heat input variation 20–140 W. Results indicate the resistance starts decreasing with the further increase in heat input as compared to DIW of SRWF after heat input 80, 100, and 120 W for FRs 10, 50, and 90%, respectively. The higher FR achieves the SRWF behavior at the lower heat input in comparison to the lower FR. Higher FR favors the sinking of heat from hot to cold region in comparison to lower FR for both SRWF and DI. The thermal performance of PHP in the case of SRWFs is explained based on the combined effect of phenomena such as the Marangoni effect, capillary effect, and wettability. The effect of temperature on properties of the working fluid, such as contact angle, electrical resistance, and surface tension of the working fluid is also studied. The occurrence of pulsating action is clarified based on the temperature profile of thermocouples installed in the condensation section at an optimum high 90% FR.

Effects of oscillation amplitudes on heat transfer mechanisms of pulsating heat pipes

The effects of oscillation amplitudes on heat transfer mechanisms of pulsating heat pipes (PHPs) are experimentally investigated. For this, a five-turn closed-loop micro PHP (MPHP) with overall dimensions of 28×67.5×1.6mm3 is made of glass top and silicon bottom. A meandering micro-channel with hydraulic diameter of 0.835 mm is engraved on the glass. Ethanol is selected as the working fluid and the filling ratio is fixed at 45%. Experiments are performed at various input powers in a vertical orientation with bottom-heating mode. The oscillation amplitude, as a representative parameter of the flow characteristics, is obtained from a high-speed imaging technique. The heat flux distribution at the interface between the fluid and the wall is simultaneously obtained from a high-speed infrared imaging technique. From the synchronization of the images of the flow visualization and heat flux distribution, the transfer of heat occurring at the interface between the fluid and the wall is divided between sensible heat and latent heat. Then, the heat transfer mechanisms of the MPHP are investigated by quantitatively analyzing the proportion of latent heat to overall heat. As the input power increases from 7 W to 16 W, the oscillation amplitude increases from 3.4 mm to 8.3 mm. The proportion of latent heat continues to increase from 54.8% to 81.9%. Due to the increased proportion of latent heat, the thermal resistance of the MPHP decreases by 13.5%. From these experimental results, it is confirmed that the proportion of latent heat increases with the oscillation amplitude, resulting in a decrease of the thermal resistance of the MPHP. These experimental findings can give a clue to improving the thermal performance of PHPs: the thermal performance of PHPs can be increased by increasing the oscillation amplitude or the proportion of latent heat in either the evaporator section or the condenser section.

An improved correlation to predict the heat transfer in pulsating heat pipes over increased range of fluid-filling ratios and operating inclinations

Previous correlations that have been used to predict the heat transfer performance of pulsating heat pipes (PHPs) offer limited thermal predictions within a narrow range of fluid-filling ratios and PHP inclinations. In this paper, a novel semi-empirical correlation with improved scope is proposed, with an increased range of fluid-filling ratios and PHP inclinations. The proposed correlation employs the dimensionless numbers governing the thermo-hydrodynamic operation of PHPs, and achieved ±30 % accuracy when predicting selected experimental data, showing reasonably good agreement. Unlike previous correlations, the new correlation can be used for different working fluids, geometrical aspect ratios, and heat loads. A comprehensive assessment of the relative significance of the correlation parameters on the total heat transfer performance is discussed. The new correlation with its flexible application range is expected to assist in faster and more enhanced thermal predictions as interest in PHPs grows.

Experimental study on heat transfer performance of pulsating heat pipes with hybrid working fluids

Pulsating heat pipe (PHP), a passive two-phase heat transfer device, has excellent application prospects in electronic cooling, renewable energy systems, heat recovery devices, etc. An experimental study was conducted to investigate the heat transfer performance of PHP with hybrid working fluids, i.e., ethanol-water mixtures (20, 30, 40, 50 and 75 vol%), graphene nanofluids (0.1, 0.3, 0.5, 0.75 and 1.0 mg/ml) and surfactant aqueous solutions (25, 50, 100, 200 and 500 ppm). For this purpose, liquid-phase exfoliated graphene (LPEG) was dispersed in 40 vol% ethanol-water mixture to prepare graphene nanofluids with excellent stability. The thermophysical properties of hybrid working fluids were then measured. Experimental results indicate that non-ionic surfactant, Pluronic® F-127, can cost-effectively exfoliate graphene from graphite using high-shear mixer. It provides a favorable condition for the large-scale application of graphene in heat transfer devices. Among ethanol-water mixtures, 30 vol% ethanol-water mixture exhibits the best thermal performance, i.e., Ep=16.01%. Graphene nanofluids as working fluids can decrease thermal resistance up to 25.16%, and the higher thermal resistance for 1.0 mg/ml graphene nanofluids is attributed to the higher dynamic viscosity and nano sheets accumulations. The heat transfer performance of PHP with surfactant aqueous solution is related to both type and concentration of surfactant. Compared with other surfactants (SDS, CTAC, Pluronic® F-127, PVP), Triton X-100 surfactant aqueous solution appears to be more effective in the improvement of thermal performance with the average enhancement ratio of 13.56%. These experimental results may help to choose the more appropriate working fluids for PHP.

Thermo-hydrodynamic model and parametric optimization of a novel miniature closed oscillating heat pipe with periodic expansion-constriction condensers

In order to promote the thermo-hydrodynamic performance of a single miniature loop pulsating heat pipe (PHP), the oscillatory behaviors and thermal transport capability of PHPs should be comprehensively and accurately analyzed. A novel closed PHP with periodic expansion-constriction condenser was proposed, where phase change and thermal transport processes could be reproduced by a comprehensive computational fluid dynamics (CFD) technique together with volume of fluid (VOF) methodology. Moreover, available experimental data were utilized in the validation of the model for the average deviations within 10%. Subsequently, a full numerical modeling for oscillating flows under different operating conditions was sensitively tested, varying thermal power and filling ratio, respectively from 18 W to 86 W and from 40% to 60%. Complicated fluid dynamical phenomena such as nuclear boiling, formation of slug, coalescence of vapor plug and flow patterns transformation have been analyzed inside the PHPs; CFD visualizations were also presented excellent agreements with flow behaviors from previous experimental photographs. Additionally, the effects of periodic expansion-constriction condenser on the flow regimes, pressure difference and thermal performance have been comprehensively analyzed. Numerical results demonstrate that 45% sharply increase in the thermal efficiency of the expansion condenser, and oscillation frequency of liquid/vapor slugs has been directly promoted for the constriction condenser. Present investigations could contribute to enhance overall performance of PHP, particularly employed for electronic cooling or heat recovery units.

The impact of gravity on the performance of pulsating heat pipe using surfactant solution

Using surfactant aqueous solution as working fluid may provide an efficient method to weaken the impact of gravity on the performance of Pulsating Heat Pipe (PHP). The Cetyl Trimethyl Ammonium Bromide (CTAB) was selected for preparation of surfactant aqueous solution in this work. For comparison, an experimental study was conducted to investigate the operation performance of a PHP charged with deionized water and CTAB solution, respectively. The results indicate that the heat transfer capacity of water PHP is clearly decreased and even lost without the assistance of gravity. However, the CTAB solution PHP shows less rely on gravity due to their higher wettability and better boiling heat transfer characteristic. Furthermore, the CTAB solution PHP presents a better thermal performance than the water PHP under the same condition. At the input power of 100 W, the thermal resistances of CTAB solution PHP are decreased by 5–51% than the water PHP when inclination of PHP varies from horizontal to vertical orientation.

Investigation of wettability on performance of pulsating heat pipe

A three-dimensional closed-loop pulsating heat pipe (CLPHP), with different wettability and charged with deionized water is numerically investigated in present work. The thermal performance and bubble dynamics of CLPHP are obtained under the condition of various input heat loads. It's found that the performance of CLPHP is affected by both surface wettability and input heat load. Under lower input heat load, CLPHP with hydrophobic surface (including superhydrophobic surface) has lower thermal resistance than that with hydrophilic surface. Conversely, CLPHP with hydrophilic surface starts up earlier, and has better thermal performance under higher input heat load. Specially, compared with the CLPHP with superhydrophobic surface, the thermal resistance of CLPHP with superhydrophilic reduces by 10.8% under the input heat load of 20 W. Moreover, the reversal of flow direction is observed in CLPHP with hydrophobic surface, while the stable directional circulation is always maintained in CLPHP with hydrophilic surface. The results indicate that the difference between advancing and receding angles (dynamic contact angle hysteresis) leads to various capillary resistance. Furthermore, due to lower flow resistance and the effect of liquid film, CLPHP with hydrophilic surface can effectively raise the dry-out input heat load.

An experimental investigation on heat transfer performance of pulsating heat pipe

Heat input and inclination angle are essential factors influencing heat transfer performance of a pulsating heat pipe (PHP). The heat transfer performance at different inclination angles is studied in this paper. The temperature distribution of a PHP at different inclination angles is obtained by using a thermocouple combined with an infrared thermal imager. The experimental results show that heat is distributed symmetrically under gravity assisted operation, and the average minimum thermal resistance is 0.17 K/W when the angle is 45°. When gravity inhibits circulation of the working fluid, temperature is distributed uniformly, and the thermal resistance increases up to a maximum value of 0.33 K/W. Meanwhile, during the gravity assist and suppression operation mode, the inclination angle only impacts the oscillating mode of the temperature. Particularly, when the angle is 90°, the PHP has the best mode of oscillation, with its heat resistance at 0.077 K/W.

Numerical and experimental investigations of hybrid nanofluids on pulsating heat pipe performance

This study investigates the thermal performance of a four-turns Pulsating Heat Pipe (PHP) using a weight concentration of 0.1 wt% Al2O3-CuO hybrid nanofluid, 0.1 wt% SiO2-CuO hybrid nanofluid and water both experimentally and numerically. The start-up pulsations, average evaporator temperatures, thermal resistance, two-phase flow, and non-linear temperature analysis were evaluated with respect to heating power and filling ratio of 10–100 W and 50–60%, respectively. Stability measurement and characterization of thermal conductivity and viscosity properties of hybrid nanofluids were determined. From the experimental results, the thermal resistance SiO2-CuO hybrid nanofluid exhibited was the lowest, i.e. 57% lower than that of water, followed by the Al2O3-CuO hybrid nanofluid, i.e. 34% lower than that of water at the heat input and filling ratio of 80 W and 60%, respectively. Nevertheless, the thermal conductivity and viscosity of Al2O3-CuO hybrid nanofluid were higher than those of SiO2-CuO hybrid nanofluid. The increased viscosity found in Al2O3-CuO hybrid nanofluid would hinder the fluid transportation in PHP, thus augmenting the thermal resistance. Meanwhile, the hybrid nanofluids were able to achieve start-up pulsations earlier and they required lower heating power to reach start-up pulsations as compared to water. At low heating power (below 30 W), the differences in average evaporator temperatures for hybrid nanofluids and water were very small. However, at higher heating power (above 30 W), the differences were significant. The numerical results compared well with those earlier experimental work, thus indicating the reliability of the current numerical simulation.