Vapor Chamber Research Articles

Pool Boiling Performance of a Sintered Aluminum Powder Wick for a Lightweight Vapor Chamber

Aluminum vapor chambers have become an important component used to solve heat dissipation problems in lightweight applications due to their low density and good heat transfer characteristics. In this paper, a new sintered aluminum powder wick is provided for an aluminum vapor chamber. An aluminum porous wick was sintered using liquid phase sintering technology. Using acetone as the working medium, the influence of the structural parameters of the aluminum wick on its boiling heat transfer performance was studied. The influence of thickness on the boiling heat transfer performance of a sintered porous wick is particularly significant. Thinner, porous wicks have better critical heat flux (CHF). The porosity and particle diameter mainly affect the heat transfer coefficient (HTC). At a low heat flux, the sintered wick with low porosity and a small particle diameter has a higher HTC. The HTC of porous wicks, with a larger particle diameter and porosity, decreases slower. The optimal porosity ranges from 46.4 ± 2.5% to 51.8 ± 2.5%. Compared with the polished aluminum plate, the CHF is increased by 1.7 times, and the HTC is increased by about 4.6 times under the same heat flux.

Experiments on thermal performance of heat pipes using nanoparticle layer as the wick

To enhance the usability of heat pipes and vapor chambers as the cooling device for portable electronic systems, necessity of thin wick is rapidly increasing. In the present work, the layer of silica nanoparticles of about 10 μm in thickness was formed on the copper tube inner wall to explore experimentally if it works as the thin wick. It was demonstrated that in comparison with the ordinary heat pipe using a wire mesh as the wick, the thermal resistance was even improved (0.62 to 0.23 K/W) and the deterioration of the maximum heat transfer rate was not significant (120 to 78 W). This indicated that the present nanoparticle layer can be used as a very thin wick of the heat pipes and vapor chambers. If the mass of nanoparticles deposited on the heat pipe inner wall was sufficient, the thermal performance was not deteriorated even after the maximum heat transfer rate condition was experienced. It was also demonstrated that the maximum heat transfer rate can be enhanced up to 100 W when the nanoparticles were suspended in the working fluid enclosed in the container.

Effect of humidity level and aspect ratio on convective heat transfer coefficient and water productivity of a solar still: Experimental and theoretical analysis

This article proposes a new correlation to estimate the convective heat transfer coefficient inside the evaporation chamber (enclosed space over the basin) of a single slope solar still with a low humidity level. The Rayleigh number, aspect ratio (width to the average height of chamber) and the relative humidity of the chamber are the main variables in proposed correlation. Existing models use only Rayleigh number to characterise the convection and neglect the effect of vapour pressure. Therefore, they fail to accurately predict the convection in higher water temperatures or in unsaturated humidity levels. In this work, the natural convection Nusselt number is generated based on a theoretical approach and the constant values in the correlation are calculated using the multiple linear regression analysis on experimental data obtained in this work. The transient thermal model of solar still using the new correlation predicts daily water yield within 7.6% of experiments under different humidity levels and aspect ratios. Higher performance is obtained in larger aspect ratio and lower humidity inside solar still. The modified solar still with a relative humidity of 62% generated 3.49 kg m−2 d−1 of water during summer in Melbourne, demonstrating an 18% increase in water yield.

Improvement in the environmental, exergy, energy, and economic performance of hemicylindrical solar still integrated with a built in active condenser: Experimental investigation

ABSTRACT In this paper, an experimental study is performed to investigate the effect of utilizing an internal condenser (IC) on augmenting the performance of a hemicylindrical type solar still (HSS). The proposed SS body is divided by a metal basin into two chambers; the upper chamber for evaporation and the bottom for condensation and located on the under of the basin absorber. Salt water is heated by solar radiation and then evaporated. Some of the produced vapor is condensed on the surface transparent cover, while the rest is naturally circulated to the condensation chamber to be condensed there. Hence, the novelty in the current work is utilizing the IC with natural air circulation in HSS instead of forced circulation and evaluate its effects on the thermal, thermodynamic, economic, and environmental performance based on energy, exergy, exergoeconomic (EXC), enviroeconomic (ENC), exergoenvironmental (EXE), and exergoenviroeconomic (EEC) parameters. For comparison, the traditional SS without an IC (HSS-C) is also tested. Depending on energy, exergy, cost, EXC, EXE, and EEC, the modified HSS with an IC (HSS-M) demonstrated outstanding performance. Comparing HSS-M to HSS-C, the daily water yield is increased by roughly 99.9%, while costs have decreased by 46.6%. Utilizing an IC increases the energy and exergy efficiency of HSS-C by around 60.4 and 51.9%, respectively. Based on energy and exergy approaches, the CO2 net emissions reduced annually for HSS-M by approximately 104.9%. The use of ICs has been successful in improving the energy, efficiency, economic, and environmental performance of HSS.

High-performance electrodeposited copper wicks for heat-spreading vapor chambers

A capillary wick structure is a key component for producing the capillary pressure that drives two-phase circulation in phase-change heat transfer devices such as heat pipes and vapor chambers. This study examines the capillary performance of a porous Cu wick structure fabricated using a new electrodeposition process. This Cu wick exhibits large channels generated by hydrogen bubbles and small pores in the dendritic Cu deposits resulting from high-current electrodeposition. The capillary wick performance can be effectively enhanced by adjusting the morphology of the dendritic Cu deposits. Dendritic Cu wicks with different porous features are prepared using different electrodeposition current densities and Cu sulfate concentrations in the electrolyte. A capillary rate-of-rise method is used to assess the liquid permeability (K), effective pore radius (Reff), and capillary performance (K/Reff) of dendritic Cu wicks with deionized wateras the working fluid. The Cu wick is then thermally treated at 700 °C in ambient N2 for 90 min to improve its structural integrity. Despite partial welding occurring between the fine Cu dendrites, the Cu wick shows a superior K/Reff of 1.5 ± 0.06 μm and excellent structural stability. The high capillary performance can enhance the mass transport rate and effective transport distance of the working liquid in vapor chambers for high-density and large-area heat dissipation applications. A vapor chamber integrated with an electrodeposited Cu wick demonstrates excellent heat-spreading characteristics, with a vapor thermal conductivity of up to 6500 W/m⋅K.

Optimization of the geometry of double-chamber basin-type passive solar stills to maximize yield

AbstractDeveloping countries require simple low-technology methods to desalinate drinking water. Passive solar stills are an example of a simple low-technology innovation that can desalinate saline water for small populations. Compared to single-chamber solar stills, double-chamber solar stills have the potential of increasing the yield of solar stills due to an increased condensation surface area. An experiment was carried out to determine the optimal angle of double-chamber solar stills. The set-up comprised double-chamber solar stills with angles of 10°, 20°, 30° and 40°, with a control set-up of a 20° single-chamber solar still. The experiment was conducted in January 2022 at Juja in Kiambu County, Kenya. The double-chamber solar stills comprised an evaporation chamber and a condensation chamber. The dimensions of the chambers were 0.5 m × 0.5 m with a height of 0.25 m. The main assumptions were that there existed steady-state conditions and that the solar still was leakproof. The research found that the 40° double-chamber solar still had the highest yield of 3.756 l/m2/day and the 10° double-chamber solar still had the least yield of 1.644 l/m2/day. Comparing the 20° double-chamber still and the 20° single-chamber still (control), the double-chamber solar still had a higher external efficiency.

Achieving robust and enhanced pool boiling heat transfer using micro–nano multiscale structures

Vapor chamber thermal management technology has become a high-reliability cooling method to solve the heat dissipation problem. However, this is still a crucial challenge to overcome when the capillary wick is exposed to harsh service environments. In this paper, a fabrication method of capillary wicks with micro–nano multiscale structures combining micro hot embossing and high-pressure hydrothermal treatment is proposed. Micro pyramid-channel is fabricated by micro hot embossing, and when the axis-to-diameter ratio of nanobars reaches 3.16–3.17, superhydrophilicity is realized. In the pool boiling experiment, the heat transfer performance of the pyramid-channel is better than that of the triangular-channel. Importantly, the superhydrophilic micro–nano structures achieve significantly improved critical heat flux and heat transfer coefficient simultaneously, increased by 162.1% and 180.8%. Moreover, the fabricated micro–nano capillary wick, which comprise high-strength pyramid-channel and specific wettability nanostructures, can maintain their outstanding superhydrophilicity and superhydrophobicity and their enhanced boiling property even after high-pressure high-velocity fluid scouring. The proposed cost-effective fabrication method provides an ideal and industrialized approach for the mass production of vapor chamber capillary wicks suitable for severe application environments.

A novel ultra-thin vapor chamber with composite wick for portable electronics cooling

With the development of integrated and ultra-thin portable electronics, the ultimate heat dissipation power in extremely narrow spaces (<1 mm) is increasing year by year. However, the current critical power of ultra-thin vapor chamber (UTVC) is still at a low level, which hinders the development of high-power portable electronic products. In this study, novel UTVCs with a thickness of only 0.5 mm are prepared by utilizing the composite capillary wick. Different from the traditional multi-layer 2D copper mesh wick, the composite (CA/CB) wick is composed of multi-layer 2D copper mesh and 3D spiral woven mesh. UTVCs prepared from three different wicks, referred as to 2D-UTVC, CA-UTVC, CB-UTVC, were compared. Under different working conditions, the CA/CB-UTVC has better heat transfer performance than 2D-UTVC. In the horizontal state, the maximum effective thermal conductivity (Keff) of CA-UTVC and CB-UTVC is significantly improved by 86.8% and 60.2% compared to that of reference 2D-UTVC. The CA design is recommended for low heating power within 40 W, while the CB design is the optimal choice for high heating power above 40 W. The maximum critical power of CB-UTVC is up to 60 W with gravity support. Even at 50 W under anti-gravity condition, the thermal conductivity of CB-UTVC is still up to 11817.1 W/(m K), which is 29.5 times that of copper. The improved heat dissipation is due to the enhanced capillary force of the composite wick. This positive effect is facilitated by the combination of multiple 3D spiral woven meshes in the CB design. The optimized UTVC effectively reduces the maximum temperature by 14.3 °C compared to copper sheet under natural convection at 10 W heating power. The novel UTVC could provide a guarantee for the heat dissipation of high-power integrated portable electronic devices in the future.

Experimental investigation of the thermal characteristics of a novel pure-metal-based flexible ultrathin vapour chamber

The rapid development of high-performance flexible electronics requires novel metal-based flexible ultrathin vapour chamber (FUTVC) with higher heat transfer capacity to meet their heat dissipation needs. Although many works on flexible vapour chambers have been published, there are few works on metal-based flexible vapour chambers. Therefore, in this paper, a novel pure-metal-based FUTVC was proposed. Three kinds of FUTVCs were fabricated by brazing process and laser welding process, which were cost-effective processes suitable for mass production. The effect of manufacturing process, test direction and bending condition on the heat transfer performance of FUTVC was clarified, and the thermal mechanism of the FUTVC under bending conditions was theoretically analyzed. Results indicated that both laser welding and brazing can effectively seal the FUTVC. Wick sintered on the cover plate can effectively improve the thermal performance of the FUTVC. The maximum heat transfer capacity of the FUTVC in gravity state, horizontal state and anti-gravity state were 19 W, 16 W and 14 W, respectively. Furthermore, the maximum heat transfer capacity of the FUTVC with bending of 15°, 30°, 60° and 90° were 11 W, 10 W, 9 W and 8 W, respectively. The maximum effective thermal conductivity of the FUTVC was over 26000 W/(m•K) in horizontal state and over 10000 W/(m•K) under different bending conditions, which were approximately 65 times and 25 times higher than that of pure copper, respectively. The proposed novel FUTVC is promising for solving the heat dissipation problem of high performance ultra-thin flexible electronics.

Innovative solar natural vacuum desalination system

The main target of the work is a design of an innovative solar natural vacuum desalination (SNVD) system and improve performance of such systems. The natural vacuum is developed by raising up an evaporation chamber to 9.8 m above the ground. The waste heat is efficiently utilized in that system to minimize the system heat loss. The fresh water is first preheated by condensing vapor from the evaporation chamber before it is heated by a flat-plate collector as a heat source of the evaporation chamber. On the other side, the sea water is preheated by the produced warm water, and it is reheated by the exit brine water before it is supplied into the evaporation chamber. A mathematical model and a transient simulation were established to investigate the annual performance of system. A heat balance of each system component was provided to estimate the inlet and outlet temperature and flow rate of it. Moreover, the collector area was estimated based on assumed mass flow rates of both feed sea water and coolant water. It was found that the system can produce a daily production of 6.2 L of pure water per a quadratic meter of collector on annual average basis. That Productivity can be estimated as 1.12 L of water per kWh solar radiation. Accordingly, the evaporation rate was estimated as 2.82% while the gain output ratio (GOR) was obtained as 0.63. The system performance can be accepted compared with the corresponding published systems.

Study of low-level pool boiling in vapor chamber of wickless micro-heat pipe based on Lattice Boltzmann pseudopotential method—Effects of superheat and wall wettability

The lattice Boltzmann method, a mesoscopic numerical method with a solid kinetic basis, is used to establish a low-level pool boiling model to exhibit the transport phenomena inside an evaporation chamber of a wickless micro heat pipe using DI water as the working fluid. The effects of wall superheat and wall wettability on bubbles’ nucleation, growth, and detachment in the evaporation chamber were compared and analysed. Moreover, the influence of the wall superheat on the thermal performance of the micro heat pipe was specifically examined. It is found that the low-level pool boiling occurs with a wall superheat that is higher than 0.357T c, indicating a high heat flux for heat removal. Interestingly, when the relatively hydrophobic chamber wall is superheated by 0.46T c, there are more nucleation sites, and the complete bubbles cycle containing nucleation, growth, and detachment is longer. In contrast, on a hydrophilic surface under the same and sufficient superheat condition, the number of bubble nucleation sites is less than that on the hydrophobic surface, and the complete cycle of bubbles is shorter. It is worth mentioning that the model has values for predictions of homogeneous nucleation of bubbles and thermal transport on hydrophobic or hydrophilic surfaces.

Three-dimensional temperature field inversion calculation based on an artificial intelligence algorithm

An increasing number of practical problems in heat transfer area are attributed to inverse heat transfer problems (IHTPs). One of the typical applications of the inverse problem is the prediction of the temperature field of an object from discrete temperature measurements of the surface. The study combines machine learning algorithms with numerical heat transfer methods to inversely predict the heat transfer boundary conditions of a hexahedral geometry from a finite number of discrete temperature measurements on its surface and then calculate the overall temperature field distribution. For the implementation of the numerical heat transfer forward problem, we first complete the coding of the finite element program to generate a training dataset for the inverse calculation by batch inputting the predefined boundary conditions. The inverse problem is modelled by constructing a neural network (NN) approach. The model is trained by calling data from the above dataset. The discrete temperature data are brought into the trained neural network for temperature field prediction. The results are tested for accuracy and generalisability. Finally, by comparing different hyperparameters and different training methods, a method of improving the efficiency and accuracy of the reconstruction results is proposed. The inversion calculation error is finally controlled to less than 0.1. In addition, the model implements the validation of commercial software simulation data and application to aero-engine turbine blades and vapour chambers. The approach can be extended as a generalised 3D temperature field reconstruction method.

Experimental study on the thermal characteristics of a 3D thermosyphon heat sink

Phase change heat transfer has received extensive attention in the thermal management of electronic devices. Most studies of heat pipe or vapor chamber were limited to one- or two-dimensional heat transfer mode. Enhancing the phase change heat transfer to three-dimensional mode in heat sinks and exploring the thermal behavior of the heat sinks deserve a dedicated study. In this paper, a three-dimensional thermosyphon (3D-TS) heat sink combining the superiorities of the vapor chamber, thermosyphon and folded fins was experimentally investigated. The experimental reliability was validated and consolidated by the heat loss analysis, and an iteration method was proposed to estimate the saturation temperature to facilitate the in-depth analysis of the results. The coupling characteristics of the air forced convection and phase change heat transfer, and the effects of the heating power and air volume flow rate on the thermal resistance of 3D-TS were involved in the discussion. The main results indicate that the overall thermal resistance exhibits a negative correlation with the heating power and the air volume flow rate. The lowest thermal resistance of 0.14 K·W−1 was achieved with Qtotal = 300 W and 100 CFM air volume flow rate. High temperature on the folded fins indicates that the phase change heat transfer extends from the flat vapor chamber to the vertical thermosyphon tubes. It is also found that for a small heating power, a relatively large air volume flow rate is not able to further reduce the overall thermal resistance due to inadequate phase change intensity. The proposed heat sink is expected to solve the heat dissipation problems for densely packed electronic devices, which can produce favorable performance according to the input heating power and appropriate air volume flow rate.

Process-dependent anisotropic thermal conductivity of laser powder bed fusion AlSi10Mg: impact of microstructure and aluminum-silicon interfaces

PurposeAlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the thermal conductivity of as-built materials as a function of processing (energy density, laser power, laser scanning speed, support structure) and build orientation, are not well explored in the literature. This study aims to elucidate the relationship between processing, microstructure, and thermal conductivity.Design/methodology/approachThe thermal conductivity of laser powder bed fusion (L-PBF) AlSi10Mg samples are investigated by the flash diffusivity and frequency domain thermoreflectance (FDTR) techniques. Thermal conductivities are linked to the microstructure of L-PBF AlSi10Mg, which changes with processing conditions. The through-plane exceeded the in-plane thermal conductivity for all energy densities. A co-located thermal conductivity map by frequency domain thermoreflectance (FDTR) and crystallographic grain orientation map by electron backscattered diffraction (EBSD) was used to investigate the effect of microstructure on thermal conductivity.FindingsThe highest through-plane thermal conductivity (136 ± 2 W/m-K) was achieved at 59 J/mm3 and exceeded the values reported previously. The in-plane thermal conductivity peaked at 117 ± 2 W/m-K at 50 J/mm3. The trend of thermal conductivity reducing with energy density at similar porosity was primarily due to the reduced grain size producing more Al-Si interfaces that pose thermal resistance. At these interfaces, thermal energy must convert from electrons in the aluminum to phonons in the silicon. The co-located thermal conductivity and crystallographic grain orientation maps confirmed that larger colonies of columnar grains have higher thermal conductivity compared to smaller columnar grains.Practical implicationsThe thermal properties of AlSi10Mg are crucial to heat transfer applications including additively manufactured heatsinks, cold plates, vapor chambers, heat pipes, enclosures and heat exchangers. Additionally, thermal-based nondestructive testing methods require these properties for applications such as defect detection and simulation of L-PBF processes. Industrial standards for L-PBF processes and components can use the data for thermal applications.Originality/valueTo the best of the authors’ knowledge, this paper is the first to make coupled thermal conductivity maps that were matched to microstructure for L-PBF AlSi10Mg aluminum alloy. This was achieved by a unique in-house thermal conductivity mapping setup and relating the data to local SEM EBSD maps. This provides the first conclusive proof that larger grain sizes can achieve higher thermal conductivity for this processing method and material system. This study also shows that control of the solidification can result in higher thermal conductivity. It was also the first to find that the build substrate (with or without support) has a large effect on thermal conductivity.

Photovoltaic Devices Using Sublimed Methylammonium Lead Iodide Perovskites: Long‐Term Reproducible Processing

Fully evaporated solar cells using methylammonium iodide (MAI)‐based perovskites can reach power conversion efficiencies exceeding 20%. An important point to advance perovskite photovoltaics is to ensure reproducibility from batch to batch. Sublimation control of organic ammonium halides is critical in achieving this for evaporated perovskite solar cells. Herein, a reproducible procedure for the coevaporation of PbI2 and MAI based on an evaporator chamber setup with only two quartz crystal microbalances (QCMs) is described. One QCM monitors exclusively the PbI2 precursor (PbI2‐QCM) and the second QCM monitors the total amount of MAPbI3 mass reaching the substrates (MAPbI3‐QCM). It is shown that the MAI evaporation can be reliably monitored, indirectly, through the MAPbI3‐QCM. In this way, the fluctuating sublimation rates usually observed due to variations of MAI purity are avoided. This allows one to obtain consistently high‐performing solar cells over a period of one and a half years.

Air-cooled hybrid vapor chamber for thermal management of power electronics

Vapor chambers (VC) are passive heat spreaders that dissipate localized heat by distributing their working liquid’s latent heat in efficient ways, and in turn, promoting device performance. In this study, the role of the physicochemical characteristics of the condenser side of a VC using a wick-free uniformly hydrophobic surface versus a wettability-patterned surface opposing a wick-lined copper evaporator is investigated. The device’s cooling capacity with water as working fluid is evaluated via two silicon-based metal–oxide–semiconductor field-effect transistors (MOSFET) as heat sources and an air-cooling mechanism simulating a real-world application in power electronics. The results show that both VC types with wickless condensers outperform a solid copper plate at high heat fluxes. A maximum heat removal of 202 W was achieved via a wettability-engineered condenser with a minimum thermal resistance below 0.01 K/W.

Wetting hysteresis as the mechanism of heat pipe post-dryout thermal hysteresis and recovery

Heat pipes and vapor chambers are passive thermal management devices used for efficient heat transport by phase change. Their passive operation is enabled by capillary pumping of the working fluid in a porous wick, which is operationally limited by the maximum pressure head it can provide. This capillary limit marks the maximum heat input at which the capillary pressure generated can overcome the pressure drop in the wick; operating above the capillary limit at steady state leads to dryout. Heat pipes and vapor chambers are increasingly being used in electronics systems where end-user activity dictates the transient power input which can therefore be highly variable and time-dependent. It was recently shown that heat pipes can withstand a power pulse exceeding the capillary limit for brief time intervals. Under such operating conditions, the heat pipe will experience dryout only if the duration of the pulse load is longer than a certain characteristic time interval. The pulse-load-induced dryout may result in an increased thermal resistance when the power is reduced back down to pre-dryout levels, thus exhibiting a hysteresis in heat pipe thermal performance. In this work, we experimentally characterize the recovery from pulsed-load-induced dryout. We further propose that the observed change in steady-state thermal performance before and after dryout results from contact angle hysteresis at the three-phase contact line of the wick-liquid interface. A model is developed based on this proposed mechanism to predict the nature of recovery from dryout-induced thermal hysteresis, as well as to identify that a given heat pipe has a maximum possible hysteresis. The experiments illustrate the trends inferred from the model for the recovery process and confirm the existence of a “maximum hysteresis line,” which identifies the worst-case scenario for thermal hysteresis after heat pipe dryout. Based on these mechanistic learnings, a new testing protocol is proposed for experimentally characterizing this post-dryout maximum hysteresis signature for a heat pipe.

Encapsulating High-Temperature Superconducting Twisted van der Waals Heterostructures Blocks Detrimental Effects of Disorder.

High-temperature cuprate superconductors based van der Waals (vdW) heterostructures hold high technological promise. One of the obstacles hindering their progress is the detrimental effect of disorder on the properties of the vdW-devices-based Josephson junctions (JJs). Here, a new method of fabricating twisted vdW heterostructures made of Bi2 Sr2 CuCa2 O8+δ , crucially improving the JJ characteristics and pushing them up to those of the intrinsic JJs in bulk samples, is reported. The method combines cryogenic stacking using a solvent-free stencil mask technique and covering the interface by insulating hexagonal boron nitride crystals. Despite the high-vacuum condition down to 10-6 mbar in the evaporation chamber, the interface appears to be protected from water molecules during the in situ metal deposition only when fully encapsulated. Comparing the current-voltage curves of encapsulated and unencapsulated interfaces, it is revealed that the encapsulated interfaces' characteristics are crucially improved, so that the corresponding JJs demonstrate high critical currents and sharpness of the superconducting transition comparable to those of the intrinsic JJs. Finally, it is shown that the encapsulated heterostructures are more stable overtime.

MOF based coated adsorption system for water desalination and cooling integrated with Pre-treatment unit

Recently, the adsorption technologies received significant interest for water purification and desalination application as well as for clean cooling production, since they offer an environmentally friendly solution using low-grade energy compared to the conventional systems. In this work, a hybrid adsorption system based on combining a pre-treatment unit for heavy metal removal with a desalination and cooling unit is experimentally investigated. Activated carbon and zeolite in powder and beads forms have been used in pre-treatment unit as adsorbent materials for the removal of iron, lead, manganese and nickel from ground water, while a coating form of aluminium fumarate MOF adsorbent material is used in heat powered adsorption heat pump for desalination and cooling unit. For the formation of activated carbon/zeolite beads, 45 % polymer loading showed the highest efficiency for the removal of the heavy metals which reached 87 % of iron. After taking the purified water from the pretreatment unit, the desalination and cooling unit produced higher than 260L/day of distilled water and 6.9 kW of cooling power with a coefficient of performance of 0.26 using a coating thickness of 0.75 mm on the wire finned tube heat exchanger adsorber beds. With the hybrid system, a practical mitigation of the accumulation of some chemical compounds on the evaporator surface with continuous operation was achieved. The effect of evaporator and condenser chamber volumes are investigated to minimize the compactness of the MOF adsorption heat pump. This hybrid adsorption system demonstrates a promising solution for pure water and cooling production over the conventional available ones.

Numerical Investigation of a Bionic Vapor Chamber Based on Leaf Veins for Cooling Electronic Devices

In order to solve the problem of integrated heat dissipation in electronic chips under continuous high-intensity operation and thus ensure their stable and normal operation, a novel bionic vapor chamber with a composite structure of leaf vein grooves is proposed. Leaf veins produce effective nutrient transport; however, how the wick core of the leaf vein groove porous composite structure affects heat transfer and flow in the vapor chamber remains elusive. In this study, the effects of the groove parameters, including the central groove diameter (D), the ratio of the inner and outer circle diameter (γ), and the number of grooves (N), on the temperature, velocity, and pressure distribution of the bionic vapor chamber were investigated based on a simplified numerical model. The results show that the maximum temperature difference at the condensing surface was reduced by approximately 50% as compared to the conventional vapor chamber, implying better temperature homogeneity. In addition, the heat and mass transfer performance of the vapor chamber improved as parameter γ increased. Moreover, the effects of variations in parameters N and D on the performance of the vapor chamber were competitive, with larger values of parameters N and D enhancing the heat transfer performance of the vapor chamber, and smaller parameter values reducing the flow pressure drop of the liquid. This provides a reference for research on the optimization of bionic vapor chambers.