Liquid-gas Phase Change Research Articles

Thermally manageable and scalable reactor configurations towards efficient hydrogen release from liquid organic hydrogen carriers

In the global pursuit to minimize carbon emissions, hydrogen has emerged as a prominent alternative energy solution. This research introduces a thermally efficient, scalable, and potentially carbon–neutral system for releasing hydrogen, employing methylcyclohexane as a liquid organic hydrogen carrier (LOHC). Our heat supply mechanism utilizes benzyltoluene as a liquid–gas phase change material (PCM) to facilitate effective heat transfer from the heating units to the reactor. We have developed catalysts with high dispersion and Pt loading of Pt/γ-Al2O3 that maintain performance over extended periods, achieving a hydrogen extraction rate of 2.3 Nm3H2(g)/h (equivalent to 5 kgH2/day) in a bench-scale reactor. The bench-scale setup achieves near-equilibrium conversion at a space velocity of 2 LLOHC/(Lcat-h) and 310 °C. The PCM-enhanced system supports a scalable catalytic bed design and simplifies heat supply and startup through the use of various heating methods. We then compare catalytic dehydrogenation reactor setups using single and hybrid heat sources; the former includes an internal Joule heater, offering simplicity and reduced heat loss but depends heavily on electrical energy, while the latter combines the internal Joule heater with an external fuel combustor, facilitating rapid startup albeit with increased heat loss. Lastly, we suggest future research directions to address existing technological hurdles and to expand the application of this system in scaling up hydrogen release processes.

Preliminary design of the FCC-ee vacuum chamber absorbers

In the FCC-ee study, it is proposed that electron and positron beams circulate at high current and high energy in a 92-km circumference twin ring. The present operational scenario foresees a first running step at an energy of 45.6 GeV and around 1.4 A current, which would generate copious amounts of synchrotron radiation (SR) power and flux. To guarantee a quick decrease of the photon desorption yields and so a fast vacuum conditioning, it has been proposed to use localized SR absorbers along the vacuum chamber, spaced about 5 m apart. This would also help contain the high-energy Compton-scattered secondaries once the beam energy is increased up to 182.5 GeV, later in the experimental program. In the preliminary design of FCC-ee vacuum chamber absorbers presented in this work, the SR thermal power is intercepted along around 100 mm of slanted surface. The temperature distribution in the adsorbers is estimated by Finite Element Analysis (FEA) and needs to be assessed to avoid any liquid-gas phase change within the water-cooling circuit. The cooling channels contain a twisted tape that increases the turbulence of water. This results in the desired heat transfer coefficient. The mechanical deformations due to the non-uniform temperature map are presented and analysed as well.

Mesoscale multi-component energy density transport for natural convective microchip cooling with solid–liquid–gas phase changes

A design of microchip cooling with natural convection driven multi-phase coolant flows is proposed by using thermoelectric modules as heat sinks. A new multi-component multi-phase (MCMP) thermal energy transport model is built for convective heat transfer with solid–liquid–gas phase changes. Different from previous lattice Boltzmann models based on temperature distributions, the present model is based on MCMP energy density distributions, which track sensible and latent heat transport for each phase. The local MCMP heat fluxes are related to mesoscale relaxation times and phase volume fractions. Transient solid–liquid–gas interfaces and local temperatures are obtained through the dynamical balance of mesoscale forces and fluxes among all phases together with MCMP enthalpy–temperature distributions. Comparisons of the on and off states of the heat sink modules show that the chip temperature can drop from about 300 to 110 °C, with the coolant liquid–gas phase change temperature of 80 °C at equivalent heat source and sink intensities of 100 W/cm2. Results also show that increasing heat sink intensity to 300 W/cm2 or decreasing gas–liquid phase change temperature to 60 °C can further decrease the chip temperature to 90 °C. The effects of sizes of chips, modules, and cooling units are also illustrated. It is observed that gas bubbles attached on chips impede heat transfer due to the low gas phase thermal conductivity, which means future improvements should also focus on removing or degrading attached gas bubbles. This model provides a quantitative tool for immersion chip cooling performances.

Influence of recoil pressure, mushy zone flow resistance and reflectivity on melt pool shape in laser powder bed fusion simulation

Melt pool dimensions (depth: D and width: W) are strongly correlated with defects generated in laser powder bed fusion. The melt pool dimensions have been evaluated by CFD simulation including solid–liquid–gas phase change and laser multiple reflection. Such a multi-physics simulation requires a large number of parameters. Preliminary simulations for parameter identification require a lot of time and effort. The parameter sensitivity to the melt pool dimensions is important; however, the systematic evaluations have hardly been found in the literature. In this study, we performed systematic parametric evaluation for three parameters related to recoil pressure, flow resistance in solid–liquid mushy zone and Fresnel laser reflection. As a result, the D values increased with increasing recoil pressure, but the W values did not. The flow resistance force influenced the velocities in the mushy zone but not the melt pool dimensions. The D increased with increasing reflectivity, but the W did not. The melt pool dimensions varying recoil pressure, flow resistance force and reflectivity were all inconsistent with the experimental melt pool dimensions. In order to agree with the experimental melt pool dimensions, the problems to be solved were discussed by comparing the previous studies.

Numerical simulations of droplet evaporation and breakup effects on heterogeneous detonations

Evaporation and breakup of droplets are critical phenomena in the liquid-fueled, multiphase detonation process. Understanding the relevant conditions and times for each process is crucial for predicting real world behavior. In this paper, the effects of evaporation and breakup on the multiphase detonation process will be explored through Euler-Lagrange (EL) simulations. Various droplet sizes of n-dodecane (C12H26) are reacted with oxygen (O2) utilizing a single-step global reaction mechanism. Droplet processes are modeled using temperature dependent thermophysical properties through the liquid-gas phase change and into the supercritical regime. Two aerodynamic breakup models are considered (based on theorized hydrodynamic instability mechanisms) from both empirical and theoretical approaches. Detonation wave velocity deficits are observed to be sensitive to breakup and evaporation time. It is shown that droplets redistribute fuel vapor mass over their lifetime, perturbing the equivalence ratio and creating vapor rich regions that cannot fully react. It was shown that as the total evaporation time decreases (shorter breakup time), the detonation structure becomes more like the idealized gaseous detonation case.

High energy-density and power-density cold storage enabled by sorption thermal battery based on liquid-gas phase change process

Cold storage is essential for the preservation of food/medical goods, energy-saving of air conditioning, and emergency cooling. However, conventional cold storage in the form of sensible heat or solid-liquid latent heat suffers from the low energy density and large cold loss during long-term storage. To address the problem, a scalable sorption thermal battery (STB) with storage capacity of 30 kWh is designed and fabricated for realizing high energy-density and power-density cold storage by proposing sorption-induced liquid-gas phase change strategy. The STB utilizes the bonding energy of sorption working pair of zeolite 13X-water to achieve cold storage during charging phase, and utilizes the liquid-gas evaporation heat of water to realize cold production during discharging phase. The cold-storage performance of the STB prototype during charging/discharging processes is experimentally investigated at different operating conditions. By optimizing the assembled structure of solid-gas reactor and enhancing the heat transfer performance of liquid-gas evaporator, the STB exhibits high cold energy density up to 114.92 Wh/kg and 26.76 kWh/m3, and high power density of 455.62 W/kg and 106.10 kW/m3, over the conventional cold storage technologies. Correspondingly, the STB demonstrates a good performance in thermal management of data centers with cooling power as high as 150 kW. Moreover, the STB has the distinct advantage of near-zero cold energy loss in long-term cold storage. The proposed scalable sorption thermal battery based on sorption-induced liquid-gas evaporation heat of liquid offers a promising route to realize high energy density cold storage.

Sonosensitive Phase-Changeable Nanoparticle Mediated Enhanced Chemotherapy in Prostate Cancer by Low-Intensity Focused Ultrasound

Prostate cancer (PCa) is one of the most common cancer types. Early detection of PC offers the best chance of successful treatment. A noninvasive, image-guided therapy mediated by targeted nanoparticles (NPs) has the potential to improve the efficacy and safety of cancer therapies. Herein, we report a sonosensitive nanoparticle modified with anti-PSMA (prostate-specific membrane antigen) antibodies to activate target prostate tumors. These nanoparticles (PFP@IR780@PTX@liposome NPs) were co-loaded with the chemotherapeutic agent docetaxel and the sonosensitizer IR780, as well as phase-changeable perfluorocarbon (PFC) liquids. The liquid-gas phase change could be induced by low-intensity focused ultrasound (LIFU) in vitro. We found that the PFP@IR780@PTX@liposome NPs can specifically accumulate in prostate tumors after LIFU irradiation, as monitored by ultrasound and photoacoustic imaging. Meanwhile, docetaxel was controllably released from the nanoparticles to achieve enhanced chemotherapeutic therapy in vivo. These sonosensitive phase-changeable NPs can visually treat prostate cancers effectively and have a clinical potential.

Review of phase change heat transfer enhancement by metal foam

• Enhancement characteristics of metal foam on solid-liquid phase change heat transfer and liquid-gas phase change heat transfer are reviewed. • The mechanism of metal foam enhancing phase change heat transfer and the factors affecting the phase change heat transfer process are comprehensively discussed. • Existing methods for optimizing phase change heat transfer performance within metal foam are classified and evaluated. • The practical applications of metal foam enhanced phase change heat transfer in recent years are summarized and compared. • This review will lead to a better understanding on the designing and applying of efficient metal foam-phase change heat transfer systems. Metal foam is a novel multifunctional material with high porosity, high surface density, and excellent heat transfer performance. Embedding metal foams into phase change heat transfer systems can be used to improve the comprehensive heat transfer performance, which is receiving increasing attention in the field of thermal management. This paper focuses on the lasted advances in solid-liquid phase change heat transfer and liquid-gas phase change heat transfer within metal foams, and specifically analyzes the influencing factors on phase change heat transfer performance as well as the mechanism of metal foam effects on phase change heat transfer. Different optimized techniques for improving phase change heat transfer within metal foams and the current state of metal foam engineering applications for improving phase change heat transfer are reviewed and discussed. It is concluded that the addition of metal foam can significantly enhance the heat transfer performance of solid-liquid phase change systems and liquid-gas phase change systems, but it is accompanied by an inhibitory effect on natural convection, an obstructive effect on bubble overflow and an elevated effect on pressure drop. The application of gradient porous structure, metal foam fins, V-groove structure or changing the surface wettability of metal foam is a feasible way to alleviate the above problems. Meanwhile, it is pointed out that the heat transfer performance of phase change within metal foam is influenced by the interaction of various factors, and some key issues regarding the influence mechanism of PCM-device orientation, pore distribution, surface wettability, and structural properties on heat transfer performance still need to be studied to develop more efficient and compact heat sinks.

Advanced phase change hydrogel integrating metal-organic framework for self-powered thermal management

With increasing global installation of photovoltaic panels and more complex functionalities of smart electronic devices, a fundamental problem in photovoltaic conversion and electronic device operation is massive heat generation, which severely reduces energy utilization efficiency and service life. Herein, we proposed a self-powered thermal management strategy integrating metal-organic framework (MOF) and liquid-gas phase change hydrogel ((Poly (vinyl alcohol)/CaCl2·6H2O, PVA/CH), which is much beyond traditional solid-liquid phase change materials in phase change enthalpy. Benefiting from the self-adaptive capability of MOF, MOF@PVA/CH bilayer was capable of efficiently evaporating water molecules with a rate of ∼0.90 kg m−2 h−1 at higher temperature and capturing water molecules with a rate of 0.21 g g−1 from the surrounding humid air at lower temperature for self-regeneration. Specifically, this self-adaptive passive cooling strategy tremendously boosted the thermal management efficiency of the simulative heater, and reduced the surface temperature of solar cell by 18 ℃. Our proposed approach provides a promising reference for achieving high cooling efficiency, low-energy consumption, and self-powered thermal management for thermo-related devices.

Micro-hole drilling of 2.5D C/SiC composite with picosecond laser: Numerical modeling and experimental validation on hole shape evolution

Micro-holes of 2.5D C/SiC composites produced by picosecond laser are widely used in aerospace, military, and automotive industries. An accurate numerical model is crucial to illustrate the formation mechanism of hole shape and ablation characteristics. This paper proposes a two-dimensional transient numerical model based on solid-liquid-gas coupling in micro-hole drilling of 2.5D C/SiC composites with a picosecond laser. In the stage of solid-liquid phase transition, original mass, energy, and momentum conservation equations are optimized by considering surface tension, gravity, and hydrostatic pressure. In the stage of liquid-gas phase change, the mass transfer during the material evaporation is considered and used as a source term to optimize the level set equation. The effectiveness of the proposed model is validated by picosecond laser micro-hole drilling experiments on 2.5D C/SiC composites. Compared with the existing research, the results show that the proposed can accurately depict hole shape evolution in picosecond laser drilling of 2.5D C/SiC composites, not only including entrance, exit diameter, and hole taper, but also the hole profile and its dynamic variation. In addition, the model effectively simulates the thermal effect phenomena, such as thermal damage, pressure concentration, and recast layer. And the thermal damage is found to be the main cause of the hole quality variation, which changes from severe to smooth along the hole entrance to exit. The research provides important support for high-quality micro-hole machining of 2.5D C/SiC composites with the picosecond laser.

The Significance of PAX8-PPARγ Expression in Thyroid Cancer and the Application of a PAX8-PPARγ-Targeted Ultrasound Contrast Agent in the Early Diagnosis of Thyroid Cancer.

Objective To investigate the significance of PAX8-PPARγ expression in thyroid cancer and the application of a PAX8-PPARγ-targeted ultrasound contrast agent in the early diagnosis of thyroid cancer. Methods In this study, the expression of PAX8-PPARγ in thyroid cancer tissues, paracancer groups, and normal thyroid tissues was detected by western and immunohistochemical techniques; the effects of PAX8-PPARγ expression inhibition on thyroid cancer cell growth, clonogenic ability, and antiapoptosis were examined. The terminal carboxylactic acid/hydroxyacetic acid copolymer (PLGA-COOH) nanoparticles were prepared by the double emulsification solvent volatilization method. The in vitro cytotoxicity of the targeted contrast agent was detected by MTS and other methods; LD50 was used to evaluate its short-term in vivo toxicity after intraperitoneal injection in mice. Results PAX8-PPARγ expression was significantly increased in thyroid cancer tissues, and the expression level of PAX8-PPARγ was closely correlated with TNM staging and lymph node metastasis (P < 0.05). In addition, PAX8-PPARγ was also expressed at high levels in thyroid cancer cell lines relative to normal thyroid cells. MTS experiments showed that the PAX8-PPARγ-targeted ultrasound nanocontrast agent had no significant toxic side effects on thyroid cells; countess observed that the contrast agent had no effect on cell survival and mortality; the LD50 assay showed that the targeted contrast agent had a wide safety range. Western blot showed the expression of caspase-3, BAX, and Bcl-2 in thyroid cancer cells, indicating that the nanocontrast agent has a good biosafety. In vitro targeting experiments showed that there were more nanospheres aggregated around the cells in the targeted contrast group. In vivo targeting imaging of nude mice revealed that the ultrasound signal was significantly enhanced in the targeted group compared with the nontargeted group after 20 min of LIFU irradiation. Conclusion PAX8-PPARγ overexpression in thyroid cancer cell lines and thyroid cancer tissues promoted the proliferation and antiapoptotic ability of thyroid cancer cells and promoted the tumorigenic ability in nude mice in vivo. We successfully prepared a PAX8-PPARγ-targeted ultrasound nanocontrast agent, which has regular morphology, uniform size, and high stability, and its liquid-gas phase change can be promoted at lower temperature. Therefore, this contrast agent can achieve US-targeted imaging and temperature phase transition function, and may have enhanced ultrasound imaging potential.

Phase-Change Nanotherapeutic Agents Based on Mesoporous Carbon for Multimodal Imaging and Tumor Therapy.

A multifunctional nanotherapeutic agent based on mesoporous carbon is reported for multimodal imaging and cancer therapy. The nanoplatform consists of oxidized mesoporous carbon nanoparticles (OMCNs) as a near-infrared (NIR) photoresponse carrier and perfluoropentane (PFP) as a phase-change agent. OMCNs can absorb the NIR excitation light and convert it into heat, which not only triggers the thermal ablation of cancer cells but also promotes liquid-gas phase change for gasification of PFP to enhance the in site tumor ultrasound (US) and photoacoustic (PA) imaging signals. This nanoplatform demonstrates good biocompatibility, attractive ability to US/PA imaging, and excellent photothermal therapy efficiency.

Preparation and in vitro study of stromal cell-derived factor 1-targeted Fe3O4/poly(lactic-co-glycolic acid)/perfluorohexane nanoparticles.

Compared with traditional imaging techniques, multimodal imaging obtains more accurate images that may increase disease detection rates. The present study prepared stromal cell-derived factor 1 (SDF-1)-loaded, targeted nanoparticles coated with iron (II,III) oxide and perfluorohexane (PFH) to be used as polymer-shelled contrast agents with multimodal imaging functions, with the aim of improving tongue cancer and lymph node metastasis diagnosis. The multifunctional, targeted, polymeric nanoparticles were prepared using a double emulsion method and chemokine SDF-1 was conjugated to nanoparticles by a sulfide bond. The nanoparticles were spherical, uniform size and well dispersed. The results of the in vitro photoacoustic and ultrasonic imaging experiments demonstrated that the multifunctional nanoparticles displayed excellent multimodal imaging functions, as even small concentrations of nanoparticles presented clear ultrasound and photoacoustic imaging. When the temperature reached the boiling point of PFH (56˚C), a liquid-gas phase change occurred and the microsphere volume and acoustic impedance increased, leading to enhanced ultrasonic development. The nanoparticles were automatically targeted to tongue squamous carcinoma cells in vitro via SDF-1-CXC chemokine receptor 4 interactions. The targeted experiment and flow cytometry results indicated that the nanoparticles underwent strong targeted binding to human tongue squamous cell carcinoma (SCC-15) cells. In summary, the nanoparticles were automatically targeted to SCC-15 cells and displayed promising characteristics for ultrasound and photoacoustic imaging. Higher concentrations of nanoparticles was associated with clearer imaged and greater echo intensity value and photoacoustic value. The present study established a foundation for the development of procedures for primary tongue cancer and lymph node metastasis diagnosis.

Hybrid photovoltaic-thermal systems utilizing liquid-gas phase change material

ABSTRACT The efficiency of photovoltaic (PV) panels is a function of temperature. Efficiency decreases by 0.5%°K−1 after 25°C. Phase change material (PCM) technology due to its ability to store and transmit heat is widely adopted as a cooling medium in the present-day research. This research articulates MATLAB simulation and modeling of integrated photovoltaic-thermal (PV-T) system, utilizing acetone to attain the desired objective of cooling PV panels and generating hot water in a simultaneous manner under the climatic conditions of Jalandhar, India. The reduction in temperature of PV panel with cooling system was 8.8°C compared to standalone PV systems. The thermal system is designed for generating hot water at 50°C.The temperature of the water can be increased up to 70°C by reprogramming the microcontroller.

Polypyrrole-coated phase-change liquid perfluorocarbon nanoparticles for the visualized photothermal-chemotherapy of breast cancer

A theranostic nanoplatform (DTX/PFH@PPy-FA) for multi-modal imaging-guided photothermal-chemotherapy has been constructed. Lipid-perfluorohexane (PFH) nanodroplet loaded with docetaxel (DTX) was coated with a polypyrrole (PPy) shell. Then the folic acid (FA) molecule with active tumor-targeting function was modified on the surface of PPy shell. Due to the good photothermal conversion performance, PPy shell can raise the temperature under the near infrared laser irradiation, which not only produces photothermal effect to kill tumor cells, but also promotes liquid-gas phase change of PFH, and produces ultrasound imaging effect. The results of photothermal experiment and imaging experiment confirmed that the obtained DTX/PFH@PPy-FA possessed good photothermal, photoacoustic imaging and ultrasound imaging effects in vitro and in vivo. The results of in vitro cell experiments showed that DTX/PFH@PPy-FA had a active targeting ability to tumor cells, and its photothermal-chemotherapy synergistically inhibited the proliferation of tumor cells. In vivo study on 4T1-bearing BALB/c mice indicated that the photothermal-chemotherapy of DTX/PFH@PPy-FA not only effectively inhibited the growth of 4T1 breast cancer, but also inhibited lung metastasis. This multifunctional nanoparticle is expected to become a new nanoplatform for the visualized photothermal-chemotherapy of cancer. Statement of SignificanceIn this work, we presented a multi-modal imaging-guided photothermal-chemotherapy theranostic nanoplatform (DTX/PFH@PPy-FA) for visualized treatment of breast cancer. The docetaxel (DTX) loaded perfluorohexane (PFH) nanodroplets (DTX/PFH@SPC) were firstly prepared and then coated with polypyrrole shell (PPy). Then, PEGylated folic acid was covalently modified to obtain the folate-targeted multifunctional nanoparticle (DTX/PFH@PPy-FA). Due to the good photothermal conversion performance, PPy shell can raise the temperature under the near infrared laser irradiation, which not only produces photothermal effect to kill tumor cells, but also promotes liquid-gas phase change of PFH, and produces good ultrasound imaging effect. The PPy shell also imparts photoacoustic imaging characteristics to the nanoparticles. Experimental results show that our prepared DTX/PFH@PPy-FA possesses folic acid-mediated tumor targeting ability, ultrasound and photoacoustic imaging, and photothermal-chemotherapy synergistic effect. This multi-functional nanoparticle is expected to become a new platform for the visualized photothermal-chemotherapy of breast cancer.

Ultrastrong and High‐Stroke Wireless Soft Actuators through Liquid–Gas Phase Change

AbstractSoft actuators and robots, which depart from classical paradigms in rigid robot construction, increase the safety of robot–human and robot–environment interactions, bring superior adaptation capabilities, and extend the range of robotic operations to fragile and sensitive objects and environments. Pneumatic soft actuators are a key building block for soft robotics due to their inherent simplicity, high forces, and large strokes. However, pressure lines connected to large pumps, regulators, and valves put significant mobility limitations on these actuators. Recently, it has been demonstrated that by using phase changes of liquids, pumps can be eliminated in favor of on‐board pressure generation. Here, it is shown that power and control of soft actuators can be realized through phase change of liquids stimulated by inductor‐capacitor resonant receivers placed in an external magnetic field. The method requires no pumps, no external fluidic or electrical wiring, and no batteries on‐board, leading to the possibility of small and low profile wireless soft actuators and robots which can operate for long durations. The phase change enables ultrahigh forces and high strokes with a small volume of active material. An ultralow profile, strong and soft pneumatic bellows‐style actuator powered and controlled wirelessly demonstrates the potential of this technique.

High Seebeck Coefficient Electrochemical Thermocells for Efficient Waste Heat Recovery

An electrochemical thermocell realizes thermal to electric energy conversion when two electrodes operate the same reversible reaction but at different temperatures. Its Seebeck coefficient is determined by the entropy change of the redox reaction. Here we report a thermocell containing acetone and iso-propanol as the redox couple, which can achieve the highest reported Seebeck coefficient of −9.9 mV K–1 when the hot side is above the boiling point of acetone. Vaporization entropy of acetone increases the total entropy change in the conversion of iso-propanol to acetone. In addition, a concentration gradient of acetone caused by evaporation and condensation increases the cell voltage significantly. Stable performance of the thermocell is enabled by a Pt–Sn catalyst operating in a neutral pH electrolyte solution. The possibility of utilizing a liquid–gas phase change to increase the Seebeck coefficient of thermocells opens a new venue for exploration.

Study of Heat and Mass Transfer in MgCl2/NH3 Thermochemical Batteries

Intermittency of sustainable energy or waste heat availability calls for energy storage systems such as thermal batteries. Thermochemical batteries based on a reversible solid–gas (MgCl2–NH3) reactions and NH3 liquid–gas phase change are of specific interest since the kinetics of absorption are fast and the heat transfer rates for liquid–vapor phase change are high. Thus, a thermochemical battery based on reversible reaction between magnesium chloride and ammonia was studied. Two-dimensional experimental studies were conducted on a reactor in which temperature profiles within the solid matrix and pressure and flow rates of gas were obtained during discharging processes. A numerical model based on heat and mass transfer within the salt and salt–gas reactions was developed to simulate the NH3 absorption processes within the solid matrix, and the results were compared with experimental data to determine dominant heat and mass transfer processes within the salt. It is shown that for high permeability salt beds, the reactor uniformly adsorbs gaseous ammonia until the bed reaches the equilibrium temperature, then adsorbs gas near the cooled boundaries as the reaction front moves inward. In that mode, the heat transfer is the dominant factor in determining reaction rates.

Future Experiments to Measure Liquid-Gas Phase Change and Heat Transfer Phenomena on the International Space Station

The article presents the approach of the European Space Agency to promote research in weightlessness and in particular onboard the International Space Station. In order to maximize the return on investments, a strong international scientific collaboration is encouraged. These Science Teams support the preparation and utilisation of the flight hardware and exploit the measurement data. In the domain of physical sciences the topics dealt with at the time of writing the present paper cover fundamental physics, fluid physics, material sciences research and specific preparatory studies in anticipation of space exploration missions. The present article focuses on two-phase (liquid-gas phase change) heat transfer related experiments. These activities cover evaporation driven thermocapillary convection, pool- and flow boiling, evaporation and condensation of films together with wettability realted issues on both reference and structured surfaces, and heat pipe systems. Some hardware are in an advanced state of development, the feasibility of some was studied or is under definition at the time of the preparation of this paper. The objectives of the experiments are described together with their expected capabilities. Beyond the understanding of mostly fundamental physical processes, the data of all the described experiments are intended to be used to validate theoretical approaches and numerical tools, which are often developed by the Science Teams in parallel with the the flight hardware design activities of space industry.

Phase Change of Water in a Hygroscopic Porous Medium. Phenomenological Relation and Experimental Analysis for Water in Soil

The phenomenological relation of non-equilibrium liquid-gas phase change in a porous medium is described at the macroscopic level using the difference in chemical potentials between the liquid and its vapor. The experiments conducted consisted in lowering the partial pressure of water vapor in the pores of a hy- groscopic soil and analyzing the return to equilibrium by two measurements: the macroscopic temperature and the partial pressure of vapor. The central hypothesis of the study is that the characteristic time associated with thermal equilibrium is much lower than the characteristic time associated with mass transfers. From these measurements, it is possible to determine the relation that links phase change rate to the logarithm of the ratio of partial vapor pressure divided by the equilib- rium pressure (RH). The representation of this relation according to RH reveals two regimes in the return to equilibrium. The characteristics of these regimes are analyzed according to water content, temperature, and total gas phase pressure.