Temperature Thermal Resistance Research Articles

Cooling of power electronic devices using rectangular flat heat pipes with externally and internally cooled condenser regions

In traditional heat pipes employing external cooling, the internal flow pattern undergoes a transition to annular flow. In this stage, vapor moves through the central region of the heat pipe, while a liquid film develops on the inner wall surface. This liquid film acts as a thermal barrier, impeding the condensation of vapor within the vapor core area, which reduces the coolant's ability to condense vapor effectively. To address this issue, a rectangular flat heat pipe with an internal condenser (RFHP-IC) has been designed and tested for heat loads up to 360 W with different fill ratios. The RFHP-IC incorporates a tube-in-tube structure within the condenser section of the heat pipe, facilitating the condensation of the working fluid while maintaining a compact form factor. Results indicate that employing an internal condenser reduces thermal resistance and evaporator wall temperature by 67.5% and 20.1% respectively when compared to an external condenser. Furthermore, the RFHP-IC allows vapor to make direct contact with the cold surface of the internal condenser, increasing the condensation rate by 8.5% in comparison to an external condenser under the same heat load. The findings of this study can improve the performance, capacity, and reliability of RFHPs, making them more suitable and efficient solutions for thermal management applications.

Enhancing heat transfer performance in 3D-printed integrated vapor chamber using composite structures

The demand for lightweight heat dissipation devices in aerospace and various other fields has spurred the development of aluminum-based vapor chambers. However, the surface of the aluminum particles is covered by a dense alumina layer, which poses a challenge in preparing the aluminum-based porous wick structure by sintering aluminum powder. In this study, two aluminum-based vapor chambers (60 mm × 50 mm × 4 mm) with distinct wick structures were integrated with the container utilizing 3D technology. The wicks of the vapor chamber included an aluminum-based grooved wick structure (GVC) and an aluminum-based grooved-porous composite wick structure (GPVC). A comprehensive experiment was conducted to evaluate the heat transfer characteristics of the vapor chamber, including startup performance, temperature uniformity, and thermal resistance, under different filling ratios and wick structure parameters. The working fluid was acetone. The results indicated that the GPVC demonstrated excellent startup performance under both low and high heat loads. The startup time of the GPVC was found to be 230 s, 30.3% less than that of the GVC under a heat load of 80 W. Furthermore, at a 60% filling ratio, the GPVC demonstrated lower thermal resistance and better temperature uniformity compared to the GVC. The GPVC achieved a minimum thermal resistance of 0.033 K/W with a maximum temperature difference of only 4.51 °C. This resulted in a reduction of thermal resistance by 47.5% and an improvement in temperature uniformity by 69%. The findings of this study provide valuable insights to the application of 3D printing technology to the production of aluminum-based composite porous wick structures.

Thermal stability and oxidation resistance of non-equimolar ratio AlTiVCrNb refractory high-entropy alloys

In this work, we investigated the thermal stability, oxidation resistance and high temperature mechanical properties of refractory high entropy alloys Ti75Al10V5Cr5Nb5, Ti67Al12V7Cr7Nb7 and Ti55Al15V10Cr10Nb10(at.%). It is found that the second phase would be precipitated and occurs order-disorder transformation in refractory high entropy alloys at high temperature. The HCP phase produced orderly B2 phase and decreased the orderly B2 phase precipitation with the increasement of temperature in Ti67Al12V7Cr7Nb7 and Ti55Al15V10Cr10Nb10. According to the oxidation kinetics of high entropy alloys after 100h oxidation at 800 °C, the oxidation index factor n is between 1.1 and 1.2 and the degree of oxidation is between oxidized and inoxidized, all three refractory high entropy alloys formed oxides with rutile structure, the Ti67Al12V7Cr7Nb7 being less oxidation resistant due to the generation of Nb2O5 which is less stable at high temperature. Ti67Al12V7Cr7Nb7 has a yield strength of 522 MPa with 50% elongation at 650 °C. Ti75Al10V5Cr5Nb5 and Ti67Al12V7Cr7Nb7 have lower strength but 150% deformation without fracture when stretched at 750 °C. The multi-component intermetallic compound nanoparticles formed by the second phase and ordered phase together in the refractory high entropy alloys have an Orowan strengthening effect, to improve the mechanical properties at high temperature since it effectively prevents dislocation movement and stores dislocations.

Performance analysis of single-phase immersion cooling system of data center using FC-40 dielectric fluid

Immersion cooling technologies have become an emerging cooling method for data center cooling. The studies available in open literature dealt with immersion cooling performance of data servers using mineral oil, EC-100, and Opticool 872552, but the studies focusing on the performance of FC-40 dielectric fluid is not available. Therefore, this study aimed to develop a single-phase liquid immersion cooling system using FC-40 dielectric fluid for a 1U (44.45 mm height) data server. The present study experimentally investigated the influence of different design and operating parameters, including the inlet/outlet port configuration (T and Z configurations), the bypass effect, the flowrate (1–3 LPM), the heating load (200–600 W), the inlet fluid temperature (15–35 °C), the presence of suction fan with various arrangements, and different heat sink bases (solid base, vapor chamber and heat pipe base). The results showed that the T-configuration could provide a 12.6% and 0.5–2.8 °C reduction in thermal resistance and case temperature compared to the Z-configuration, respectively. Furthermore, the heat sink with heat pipe and vapor chamber base offered a minimum case temperature of 56.7 °C and 55.2 °C against the 60 °C experienced in the heat sink with flat plate base, respectively.

Microstructural evolution and properties enhancement of SiC refractory castables bonded with the special CNFs/calcium aluminate cement

To overcome the bottleneck in improving the high-temperature mechanical properties of SiC castables bonded with vulnerable oxides, a lab-synthesized special carbon nanofibers/calcium aluminate cement (CNFs/CAC) was used as a binder for SiC castables. The microstructural evolution, thermal shock resistance and high temperature modulus of rupture properties were investigated. The results showed that uniform and continuous SiC nanowire networks were generated in the matrix of SiC castables bonded with CNFs/CAC. The continuous network-like SiC nanowires were grown in the liquid phase using carbon nanofibers as templates. The high temperature modulus of rupture (HMOR) of the SiC castables bonded with CNFs/CAC was 52.2% higher than that of SiC castables bonded with Secar71. The residual strength ratio of the SiC castables bonded with CNFs/CAC after thermal shock increased by 28.3% (from 70.5% to 90.5%) compared to that of the SiC castables bond with Secar71. This is because the oxide binder was significantly reinforced by the SiC nanowires.

Effect of load application method on thermal contact resistance and uniformity of temperature distribution

Traditionally, the research on thermal contact resistance based on real rough surfaces is often limited to the uniform load. This study investigated the effects of the material, surface roughness, pressure load, and temperature on the thermal contact resistance and contact interface temperature distribution non-uniformity under a concentrated load. First, rough surfaces with different surface roughness degrees were generated by using a random generation method, and microscopic contact numerical models of three different materials were established. Then, the real contact area of different pressure loads under uniform and concentrated loads were calculated. Finally, heat transfer analysis was performed at different temperatures based on the microcontact state, the thermal contact resistance and the contact interface temperature distribution non-uniformity were calculated. Compared with the uniform load, the thermal contact resistance and the non-uniformity of the temperature distribution were improved under the concentrated load, and the effect was more obvious under the conditions of a large pressure load and small surface roughness degree. In addition, it was found that the uniformity of the temperature distribution on the contact surface was proportional to the real contact area and temperature instead of the thermal contact resistance except when the real contact area was very small.

Studies on the Platinum Thick Film Sensor Conformally Written by Laser Micro-Cladding: Formability, Microstructure, and Performance

In this paper, laser micro-cladding technology (LMC) was conducted to prepare high-temperature Pt thick film sensors in situ. The formability, microstructure, sintering mechanism, and electrical properties of the LMCed Pt thick films were first studied systematically. Results indicated that with the increase of laser power density, the sintering degree of the Pt thick film increased obviously, improving its adhesion strength and reducing its resistivity. However, when the laser power density exceeded the threshold, holes or grooves were formed in the Pt film, leading to the degeneration of its properties. A Pt thick film with good adhesion strength, excellent conductive networks, and the minimum resistivity (46 ± 2 μΩ·cm) was obtained at a laser power density of 1.37 × 106 W·cm-2. Then, Pt thick film temperature sensors (including Pt thermal resistance temperature (RTD) and Pt-Pt10%Rh thermocouple sensors) were conformally prepared by LMC. Their temperature-sensing performance became stable after the initial high-temperature calibration, with a linearity of 0.9985 for the RTD with a TCR of 2.46 × 10-3/°C (at 920 °C) and a linearity of 0.9905 for the thermocouple with a Seebeck coefficient of 9.7 μV/°C, both of which are better than that made by direct DC magnetron sputtering deposition. Therefore, this work provides a novel feasible way to conformally integrate high-performance Pt film sensors in situ.

Thermal management of GaN HEMT devices using subcooled flow boiling in an embedded manifold microchannel heat sink

Ultra-high heat flux thermal management has been an urgent demand for high electrical performance and reliability of GaN HEMT electronic devices, and direct fabrication of embedded heat sinks have proven to be an effective approach for its thermal management. In this work, a self-developed solver based on OpenFOAM has been employed and verified for numerical investigations of three-dimensional two-phase flow coupled with conjugate heat transfer. An extremely uneven heat source distribution in GaN HEMT is accounted for in the numerical modeling with localized refined mesh. The thermal performance and pressure drop during subcooled flow boiling are investigated and presented considering parametric effects of heat flux, mass velocity, inlet/outlet width ratio, manifold thickness and channel aspect ratio as well as substrate materials. The results indicate that GaN-on-Diamond structure provides a lower thermal resistance and better temperature uniformity, and the superior performance of GaN-on-SiC and GaN-on-Diamond are augmented with increasing heat flux during subcooled flow boiling. Additionally, it can be concluded that maximum temperature and pressure drop decrease with increasing channel height firstly, and then flatten out as the height/width ratio reaches 8 and 6, respectively. The flatten-out relationship between increasing height/width ratio and thermal/hydraulic performance is partly attributed to the balance of decreasing convective heat transfer coefficient and increasing effective area. Besides, flow pattern analysis for high-aspect ratio microchannels shows that hotspots at the bottom of inlet manifold promote the bubble nucleation and bubbles tend to accumulate at the bottom of channels because of nonuniform velocity distribution along the microchannel height.

Thermal Management Techniques for Lithium-Ion Batteries Based on Phase Change Materials: A Systematic Review and Prospective Recommendations

Thermal management systems for lithium-ion batteries based on the cooling and heating of phase change materials have become a popular research topic. However, the low thermal conductivity, flame resistance, high and low temperature adaptability of phase change materials, as well as the thermal runaway mechanisms and lightweight design of phase change material-based systems remain to be explored. The aim of this paper is to conduct a publication-wide macro bibliometric review on thermal management systems for lithium-ion batteries based on phase change material to date. Total of 583 associated publications were retrieved from the Web of Science Core Collection database for the period 2006–2022. A bibliometric study was conducted through the visualization software VOSviewer. The findings were derived from annual publication trends, geographical and institutional distribution, authors and their collaborative networks, keyword network analysis and analysis of highly cited publications as well as reference co-citation analysis. The findings provide a comprehensive overview of the evolution of research hotspots in the field and can help researchers who would like to work in the field to quickly grasp the research frontiers and the overall picture. Furthermore, some suggestions for future work are summarized.

Heat transfer process analysis and performance research of micro heat pipe array applied for the thermal management of proton exchange membrane fuel cells

• A new PEMFC thermal management method based on micro heat pipe array is proposed. • Micro heat pipe array has fast thermal response and good temperature uniformity. • Micro heat pipe array can enhance the heat dissipation capacity of PEMFC. Effective thermal management is critical for the safe and efficient operation of proton exchange membrane fuel cells (PEMFC). The small temperature difference between the stack and the environment brings greater challenges to the cooling system. This study proposes the integration of micro heat pipe arrays (MHPA) into bipolar plates for thermal management of small-power air-cooled PEMFC. The heat transfer performance of 2 mm MHPA under air-cooled conditions is experimentally studied, and a comparative study is conducted on the actual application of air-cooled PEMFC. The results show that the MHPA can reach a steady state within 600∼900 s when the heating power is changed. The minimum thermal resistance of the MHPA is 0.53 K/W, the uniform temperature distribution in the evaporation zone is very uniform within 2 K, showing a small heat transfer thermal resistance and good temperature uniformity performance. When the maximum temperature inside the stack does not exceed 65 ℃, the maximum output power of the MHPA-PEMFC is 25.66% higher than that of the traditional air-cooled PEMFC, and the maximum temperature difference inside the stack is reduced by 50.1%. The results of this study provide a theoretical basis for the application potential of MHPA in PEMFC thermal management.

Comparison on the heat transfer performance and entropy analysis on miniature loop thermosyphon with screen mesh wick and metal foam

Comparison on the heat transfer performance (HTP) of copper screen mesh wick and metal foam inserted evaporator section of miniature loop thermosyphon is experimentally investigated. Porosity of both screen mesh wick and metal foams are fixed to be 63%. Experiments are conducted using DI water under vertical orientation for different heat loads (40 W–280 W) and filling ratios (FR = 20%, 30% and 40%). Results showed a decrease of 12.8% and 5.2% in thermal resistance and wall temperature respectively for the metal foam inserted evaporator. In addition 10.6% enhancement is noted for heat transfer coefficient at the evaporator region for 30% FR. Reduction of 4.6% in heat transfer irreversibility is also noted for metal foam inserted thermosyphon compared to screen mesh wick condition. Increase in interstitial heat transfer between the fibers of metal foam and larger pore size of metal foams resulted in higher permeability compared to screen mesh wick are responsible for the enhancement in the overall HTP of metal foam inserted thermosyphon. Based on the observed results, the use of metal foams inserted thermosyphon will be a better substitute for thermal management applications of electronic devices.

Substrate BOX engineering to mitigate the self-heating induced degradation in nanosheet transistor

The continued scaling of 3D transistors into the ultra-scaled-down nanoscale regime causes self-heating effect (SHE) driven thermal deterioration. Particularly in silicon-on-insulator (SOI) FETs, the induced thermal degradation is more severe due to the presence of a conventional lower thermal conductivity material (i.e., SiO2) as a buried oxide (BOX), which obstruct the heat flow from the active area to substrate. Thus, the lattice temperature rises above the ambient temperature. Therefore, in this paper, we proposed a substrate-BOX engineered Nanosheet (BOXNS) FET to mitigate the self-heating-induced thermal degradation. Through well-calibrated TCAD models, we investigated the impact of incorporating a superior dielectric material with significantly higher thermal conductivity, such as crystalline diamond (kth = 2000 W m−1 K−1) in place of conventional SiO2, possessing lower thermal conductivity (kth = 1.4 W m−1 K−1) beneath the source and drain region. The results reveal that the proposed BOXNS FET effectively improves the SHE-induced thermal degradation in terms of ON current (ION), OFF current (IOFF), effective thermal resistance (Reff), and lattice temperature (Tlattice), compared to the conventional SiO2 Nanosheet (SiONS) FET. In BOXNS, the hotspots from the active (channel) region find a pathway through the realized crystalline diamond (DLC) and thus decreases the lattice temperature by 13.5 K. Moreover, the dimensional variation, such as channel thickness variation in the proposed BOXNS FET, shows less effective thermal resistance and lattice temperature fluctuations than the SiONS FET while varying the ambient temperature from 300 K to 370 K.

Study on self heating effect of enhancement-mode Ga<sub>2</sub>O<sub>3</sub> vertical MOSFET

<p indent="0mm">In this paper, a vertical enhanced Ga₂O₃ MOSFET is designed. Due to the low thermal conductivity of gallium oxide material, the output characteristics of the device under different crystal orientation materials, different thermal resistance and different temperature are studied. The thermal characteristics of Ga₂O₃ MOSFET are analyzed based on the temperature distribution characteristics of the device. The thermal conductivity model studies the effect of different orientation of gallium oxide on the output characteristics and temperature distribution of the device, and it is found that the thermal conductivity of [010] orientation is the best. When <italic>T</italic>=<sc>300 K,</sc> the thermal conductivity is about <sc>0.1 W/cm K,</sc> which is higher than that of other crystal directions, and the corresponding output saturation current is the largest under the same voltage (<italic>V</italic>_gs=<sc>3 V, </sc><italic>I</italic>_dsat&gt;<sc>400 A/cm²).</sc> Furthermore, the output characteristic curves of different crystal directions under different temperature and different thermal resistance are studied. With the decrease of thermal resistance, the heat dissipation capacity at the device boundary is improved. Thus, the influence of self-heating effect is suppressed and the drain saturation current increases. The normal operation of the device can be ensured when the boundary thermal resistance is <sc>0.01–0.005 cm² K/W.</sc> All of these provide reliable methods and reference value for optimizing device performance in the future.

An experimental investigation on the heat transfer characteristics of minichannel thermosyphon with multiports for cooling the modern miniaturized electronic devices

Thermal performance of an air cooled minichannel thermosyphon having multiports (10 ports) with hydraulic diameter of 1.18 mm is investigated. Experiments conducted at different heat loads (10 to 90 W), filling ratios (40, 50 and 60 %), inclination angles (30, 45, 60 and 90°), confluence lengths (0, 5 and 10 mm) and cooling air velocities (0.8, 1, 1.2 and 1.5 m/s) using acetone as working fluid. Results showed a maximum heat dissipation of 90 W with evaporator wall temperature of 72.2 °C at 5 mm confluence length. Multiports act as internal fins and enhance the surface area of the thermosyphon. This improves the boiling and evaporation rate, leading to reduced thermal resistance and wall temperature. An average reduction of 17.1 and 48.2 % are respectively noted in the irreversibilities of heat transfer and pressure drop at optimum condition. Liquid reservoirs at both ends of the thermosyphon overcomes the entrainment problem and supply the required quantity of working fluid and prevents it from reaching dry out condition. Analysis revealed that, the internal flow pattern transition is between Slug and Geyser flow for the tested heat loads. The present experimental findings can be a useful guide for engineering design to satisfy the requirement of cooling in miniaturized electronic devices.

Hemp Reinforced Polylactic Acid (PLA) Composite Produced By Fused Filament Fabrication (FFF)

Reinforcement of polymer matrix with natural fiber can provide an increase in mechanical properties of the related composite. Since thermoplastics, especially bio composite materials are recyclable, they contribute to a sustainable ecosystem. In this study, 10% by weight hemp reinforced polylactic acid (PLA) matrix compounds were produced. Tensile test specimens were performed in two different infill patterns, parallel and +/- 45° cross, using the Fused Filament Fabrication (FFF) method from the developed bio composite filaments. Ultimate tensile stress increases approximately 20%. It has been observed that the geometry of the infill pattern greatly affects the tensile strength. In addition, through optical and scanning electron microscopy (SEM) the the produced composite filaments were examined. Surface interactions and homogeneous fiber distribution between PLA and hemp were investigated. As a result, hemp is used as a reinforcement material in related studies, its homogeneous distribution is very important. Although the compounds were produced by twin-screw extrusion. Weakness in the form of the surface bonding is observed. This situation affects the structural performance negatively. Addition of hemp decreases the thermal resistance and melting temperature and increases the glass transition temperature comparing to pure PLA.

Investigation on the two-phase flow and heat transfer behaviors in a new central uniform dispersion-type heat exchanger

In order to improve the temperature uniformity of multiple chips, a new central uniform distributed heat exchanger (CUD) is designed. Firstly, adopting ethanol solution as coolant, the cooling ability of the heat exchanger is numerically investigated by using VOF gas-liquid two-phase flow model, and the two-phase flow experimental system is established to verify the correctness of the numerical results. The results show that the Tavg (average temperature of heat sources) error range between the experimental and numerical values is 1 K ~ 3 K, and the relative error of SDT (standard deviation of temperature) is 6% ~ 10%. This verifies the accuracy of the numerical simulation method. Secondly, the two-phase flow boiling heat transfer behavior are compared with that of single-phase flow with water as coolant. The results show that with the increase of inlet flow, the thermal resistance and average temperature of two-phase flow change are less than that of single-phase flow. This indicating that two-phase flow has better advantages in improving the temperature uniformity of multiple heat sources. Thirdly, the heat transfer characteristics of radiators with different Wi are studied. Compared with Case1, the boiling heat transfer coefficient of Case3 and Case4 can be increased by 12.3% and 18.3%, respectively. However, Case3 is a better choice by weighing the pressure drop. Finally, the prediction functions of the boiling heat transfer coefficient and pressure drop is established, and the multi-objective genetic algorithm is used to obtain the best parameters of this heat exchanger. The average heat transfer coefficient of the optimized heat exchanger can be increased by 7.56%, and the pressure drop can be reduced by 3.54% compared to the exchanger before optimization. Furthermore, the heat dissipation ability of the optimized heat exchanger design is studied numerically. The simulated results are in good agreement with the optimization results.

Degradation Induced by thermal and chemical impacts on matrix codes installed on brass and aluminium alloy parts by laser

To be securely readable, barcodes and matrix ID codes that are installed on metallic or non-metallic surfaces should be of high contrast both immediately after installation and throughout the life of the product that carries them. However, utilizing the product in hot and harsh environments (in acids, alkalis, etc.) may lead to its structural degradation and, consequently, affect the contrast of the codes making them poorly readable with the help of optical devices. The efficiency of such degradation is also governed by the product material. This paper describes the results of a study that looked at the degradation of matrix codes installed by lasers on products made of L63 brass grade and D16 aluminium alloy following thermal and chemical impacts. It is shown that the thermal resistance temperature of laser-installed ID codes for brass is 200 oC, while barcodes installed on the aluminium alloy remain readable when heated up to 600 oC. A major change is noted with regard to the effect produced by 2% acid solutions on codes installed on brass. In the case of the aluminium alloy, a 2% solution of sulphuric acid did not affect the contrast of the codes. When treated with alkaline solutions, a brass surface with a code turned dark, the contrast of the codes degraded significantly and the code became poorly readable. At the same time, alkali produced but a slight effect on the contrast of codes installed on the aluminium alloy.

Role of nano-ZrO2 powder in in-situ formation of ceramic whiskers in Al2O3-C slide plate materials

The effects of nano-ZrO2 powder on the evolution of phase composition and microstructure of Al2O3–C materials during firing have been investigated using tabular alumina, Si powder, Al powder, graphite and nano-ZrO2 powder as starting materials. The residual content of Al and Si gradually decreased with increasing temperature, and the added nano-ZrO2 facilitates the reactions involving Si and Al. The quantity of in-situ synthesized AlN and SiC whiskers exhibiting continuous interlocking networks increased gradually with temperature. Nano-ZrO2 facilitates more ceramic whiskers generated in samples, which play a strengthening and toughening role in the materials, thus improving the thermal shock resistance and high temperature strength of Al2O3–C materials. In addition, physical properties are improved due to the nano-ZrO2 filling the pores and increasing the density of materials.

Thermal-structural characterization and H2 generation capability of novel CeO2/graphene catalyst

This work focuses on the obtaining and studying a graphene-supported ceria catalyst by a simple, economic and reproducible method. The catalyst is intended for H2 generation from water dissociation via water gas shift reaction (WGSR). Different characterization techniques were used to obtain the thermal-structural and elemental information of the catalysts synthesized by a microwave-initiated polyol method. The as-prepared catalyst (graphene-supported) exhibits excellent thermal resistance and lower temperature activation than a conventional catalyst supported on alumina. The catalytic performance of the material was evaluated by running the WGSR, in which the conversion of CO was twice in comparison with that obtained using the ceria supported in an alumina support and the methane selectivity was reduced, from 31% to 16.1% for alumina-supported and graphene-supported, respectively. Besides, the graphene-supported CeO2/graphene catalyst exhibits higher selectivity towards H2 generation than alumina-supported (43.1% vs 40.6%), as a consequence of synergism between ceria and graphene, which was evaluated using EELS technique, improving the catalytic activity of the material by the spillover effect. Finally, we suggest the use of this novel composite as support for metallic nanoparticles.

Three-Dimensional Numerical Analysis of Mini-Grooved Flat Heat Pipe Filled with Different Working Fluids with Experimental Validation

Mini-grooved flat heat pipe (FHP) is an efficient approach to cool the electronics within small space. As it was hard to measure the flow and thermal characteristics inside the FHP, a novel three-dimensional model was set up to couple velocity, pressure, temperature, and mass transport inside the FHP, anticipating understanding the working mechanisms of FHP filled with different working fluids under transient and steady states. Temperature-dependent physical properties of working fluid and simulated thermal conductivity of wick were employed. The numerical results were validated by experiment with the maximum deviations in thermal resistance and maximum temperature of 17.9% and 5.0%, respectively. It was found that working fluid types, properties and input heat affected the FHP performance. The deionized water filled FHP shows more excellent thermal characteristics. Under input heat of 10 W, the thermal resistance, maximum temperature, and temperature nonuniformity of deionized water filled FHP were numerically lower than those of anhydrous ethanol filled FHP by 48.1%, 11.5% and 56.4%, and lower than those of hexane filled FHP by 54.4%, 14.3% and 62.6%, respectively. However, the starting performance of deionized water filled FHP is comparatively poorer. FHP filled with anhydrous ethanol or hexane is more appealing for electronics cooling.