Thermal Control System Research Articles

Dimensionless study of phase-change-based thermal protection for pulsed electromagnetic machines: Towards heat absorption-dissipation matching

The concept of “more- and all-electric aircraft” has become increasingly popular over the last two decades, leading to a boost in the extensive utilization of airborne electromagnetic actuators such as permanent magnet synchronous machines (PMSMs). Inevitably, considerable waste heat is generated during operation due to the incomplete energy conversion, which is a great challenge for conventional onboard thermal control systems. If the huge generated heat cannot be removed efficiently there will be a sharp temperature rise in thermal-sensitive components of the onboard devices. This overheating will cause operational failures which are intolerable in aerospace applications. Aiming to improve the current thermal protection system and gain greater compatibility with the current PMSM system, this paper proposes a phase change material-based (PCM-based) thermal protection strategy using commercial wax in two equivalent PMSMs. A comparative investigation shows that the machine temperature with PCM-based cooling strategy can be reduced under most operating conditions (the maximum temperature drop is 13.7 °C), demonstrating the advantages of deploying the proposed PCM-based cooling scheme. Further data processing towards the heat absorption-dissipation matching between the utilized PCM and the working mode of the cooling object is conducted. A dimensionless correlation of dimensionless temperature peak difference (DTPD) as a function of the pulsed factor, presented in Eq. (17), reveals an average relative error of ±4.5%. Based on the correlation, an optimal pulsed factor of ∼1.764 is calculated to reach a matching condition. Such a method can be promoted to wider applications using PCM as a cooling medium beyond the currently-utilized two types of machines in this paper.

Spacecraft smart radiation device with near-zero solar absorption based on cascaded photonic crystals

Smart radiation device (SRD) for spacecraft based on thermochromic material vanadium dioxide (VO2) attracts increasing interest due to its ability of self-adaptive emission regulation. However, the spacecraft SRD is constrained by the high solar absorption at a high temperature and low emission tunability in practical applications. In this paper, a SRD is proposed for spacecraft thermal control, which consists of a solar reflector based on cascaded photonic crystals and a thermal emitter (VO2/BaF2/Ag). By cascading four photonic crystals with photonic band gaps for different central wavelengths, the total reflection range of the SRD in the solar radiation band is broadened. It is found that the SRD can realize near-zero solar absorption and high emission modulation depth, simultaneously. Though optimizing the thicknesses of the VO2 and BaF2, the emission modulation depth can reach 0.69, and the solar absorption can reduce to 0.08. In addition, the physical mechanism is studied by the distribution of the electric field. It is proved that the near-zero solar absorption originates from the broadband total reflection of the cascaded photonic crystals. The phase transition properties of VO2 and the difference in inherent losses at high and low temperatures result in high emission modulation depth. Besides, the low solar absorption and high emission modulation depth performances of the SRD can remain excellent when the angle of incidence is small than 46° regardless of the transverse electric wave or transverse magnetic wave. This work not only provides a new idea for designing SRDs, but also is expected to accelerate the development of intelligent thermal control of spacecraft.

Numerical investigation of natural circulation loop with supercritical CO2 on the thermal control system of micro spacecrafts

Aiming at the heat dissipation problem under the strict constraints of mass, volume, and power consumption in micro spacecrafts, the feasibility of applying a natural circulation loop (NCL) to the thermal control system is performed for the CubeSats (Cube satellites) of orbiting operations or the micro-rovers of extraterrestrial explorations. A 3-dimensional NCL model under variable gravity conditions corresponding the environment of aerospace is established, and the supercritical CO2 as the coolant. The heat transfer and thermal performance of NCL under gravity range of 10−6 g to 10 g are analyzed numerically, including the Earth orbit, the surface of the Moon and the Mars etc. The calculation results present that the gravity has a great influence on the flow circulation characteristics and thermal performance of the NCL. The applicability of employing NCL on the thermal control system of micro spacecrafts is validated with the gravity no less than 0.05 g. It is worth noting that, by designing the range of temperature from inlet to outlet of the heated tube covering the large specific heat region, the superior thermal performance can be obtained on account of the strong heat-carrying capacity of supercritical fluid, even under the low gravity with a small mass flow rate. Finally, a flow correlation is proposed considering the effect of gravity, flow regime, buoyancy force, and geometric factors, which is suitable on the NCL in the thermal control system of micro spacecrafts, and the R2 is 99.77%.

Relationship between phase distribution and heat-transfer coefficient of loop heat pipe evaporator investigated by lateral observation of porous media

Loop heat pipes (LHPs) can be passively operated, require no electric power, and can be flexibly arranged, making them promising in thermal control systems for both terrestrial and aerospace applications. Understanding the two-phase state in the porous media of a capillary evaporator induced by nucleate boiling is key to enhancing the evaporator performance. This study visualized the liquid–vapor (L–V) phase distribution on the contact surface between the cylindrical evaporator casing and the wick to investigate the L–V phase distribution and to figure out its relationship with the evaporator heat-transfer coefficient. The visualization was successfully realized under conditions similar to those observed in a practical environment using a sapphire tube as the evaporator casing. The observation results showed that the wick underwent a phase transition from a liquid-saturated state to a two-phase state under the effect of nucleate boiling, and the evolution of the L–V phase distribution on the contact surface with varying heat load could be determined. The heat-transfer coefficient peaked immediately after the nucleate boiling and then decreased with increasing heat load. The three-phase contact line (TPCL) within the casing, liquid, and vapor phases showed a similar trend; however, the saturation on the contact surface was different, decreasing quickly after the nucleate boiling, followed by a gradual decrease. The correlation coefficients between the heat-transfer coefficient and the saturation/TPCL length were −0.61 and 0.83 under all heat load conditions, respectively. The characteristics of the heat-transfer coefficient as a function of the heat load were found to correspond to those of the TPCL length rather than the saturation. This finding can aid in the design of microscopically optimized porous media by additive manufacturing.

Systemic symptom detection in telemetry of ISS with explainability using FRAM and SpecTRM

Explainability is important for machine learning-based anomaly detection of safety critical systems. In this respect, we propose a new systemic symptom detection method by combining two methodologies: the Functional Resonance Analysis Method (FRAM) and the Specification Tools and Requirement Methodology-Requirement Language (SpecTRM-RL) with machine learning-based normal behavior prediction model. The method was verified with data of thermal control system of Japanese Experimental Module of the International Space Station, and the result found that the proposed method enables flight controllers and specialists to obtain additional information for identifying causes of anomaly with the method.

Laminar Rayleigh–Benard convection in a closed square field with meshless radial basis function method

Abstract Research on natural convection is exciting in some experimental and numerical cases, especially in rectangular cavities with relatively low heat dissipation and thermal control systems with low cost, reliability, and ease of use. The present study will use the meshless radial basis function method to solve the velocity formulation of the Navier–Stokes equations by varying some nominal Rayleigh numbers of 104, 105, and 106. The numerical accuracy is compared with the previous research. The advantages of the meshless method are that it does not require a structured mesh and does not require inter-nodal connectivity. The results show that the temperature pattern is identical to the previous research. The calculations have been done for three different Rayleigh numbers of 104, 105, and 106 for 151 × 151 nodes. The variations of the Ra number will affect the isothermal, velocity contours, and Nusselt number.

Cooling process analysis using the energy-flow-diagram method for the complex heat dissipation network with a typical space station cabin

The large thermal inertia, multiple mass storage links, and various heat dissipation modes will seriously affect the cooling process for complex spacecraft. The energy-flow-diagram method can reflect the flow relationship between each link, so this method is first applied in the thermal analysis of spacecraft to explore the proportion of heat transfer allocation between structures in this paper. Taking the “Tianhe” space station as an example, the heat transfer mode and flow direction in the process from heat source to cold source are analyzed, and then the thermal dynamic model of each link is established. According to the above model, the heat transfer and proportion of different heat transfer modes between sections can be obtained, and then the heat flow diagram of the spacecraft can be drawn. Finally, the heat flow distribution under typical instantaneous, full orbital periods and other working conditions is studied. The results show that the instantaneous heat absorption can reach 1.63 kW in the sunlit region and the instantaneous heat release can reach 2.26 kW in the shadow region. According to the transient heat flow in the sunlit region, only 5.18 kW of the 10 kW heat in the cabin is discharged, and nearly half of the energy is stored in the system. When the areal density of the radiator exceeds 11(kg/m2), the heat storage of the radiator will not be obvious. For pulsed heat consumption, when the proportion of high load time is between 0.5 and 0.7, the system shows a good heat transfer effect. In this paper, the analysis of heat flow distribution among spacecraft structures and the energy difference and time difference between heat source and cold source provide an important basis for spacecraft thermal management and optimization.

Numerical simulations, experimental investigation and optimization of hybrid space thermal radiators

Spacecraft thermal management is a critical issue as power requirements for high-capacity satellites and human space flights continue to grow. Radiators play a vital role in heat transportation and act as sinks in this process. This study focuses on the optimization of a novel space thermal radiator. Conventionally, space thermal radiators have parallel tubes. Recent studies have evaluated the performance of serial radiators for heat transportation in spacecraft. In this study, a hybrid radiator that combines the advantages of both parallel and serial radiators is proposed for space applications. Performance analysis through conjugate heat transfer analysis is conducted on hybrid radiators and compared with parallel and serial radiators. Hybrid radiators effectively reduce the impact of micro-meteoroids and orbital debris. By appropriately isolating the leaking tube, hybrid radiators can maintain 95.4% heat rejection even in the event of tube leaks caused by orbital debris impact. Using Taguchi signal-to-noise ratio analysis, the optimal radiator geometry only incurs a 10 Pa pressure drop, compared to the 572 Pa baseline configuration, and has a lower mass of 4.3 kg instead of 6.8 kg. The study also found that when reduction in pressure drop is a priority, increasing tube diameter is crucial, but when mass reduction is important, decreasing fin thickness should be prioritized. The study demonstrates that hybrid radiator is a better alternative to parallel and serial radiators in spacecraft heat transportation process, especially when reduction in mass and pressure drop are equally crucial.

Solar Absorptivity Degradation of Spacecraft Materials Due to UV and Charged Particles in the Gateway Environment

Gateway will be an outpost in cislunar space designed to survive a 15-year mission to support human Moon landings and future deep space exploration. The Gateway Passive Thermal Control System (PTCS) Group has identified charged particle and UV degradation of potential Gateway materials as a knowledge gap for the Near Rectilinear Halo Orbit (NRHO) and transit environment, especially the slow spiral transit planned for the first two modules. Solar absorptivity degradation is important to quantify because the end-of-life absorptivity impacts thermal performance of the system. To address this, ground testing has been completed at NASA Goddard Space Flight Center in which potential Gateway materials, including radiators, multi-layer insulation (MLI), and structural materials are subjected to the expected transit plus 15-year on-orbit charged particle fluence (9.86x1015 protons/cm2 at 2.5 keV and 3.1x1016 electrons/cm2 at 10 keV) and 5093 Equivalent Solar Hours (ESH). Reflectivity of a single sample of each material was measured in atmosphere and in vacuum inside the chamber after exposure to incremental levels of ESH and charged particle fluence. Increase in absorptivity of most samples were seen throughout the test including large differences in absorptivity of materials of the same category. Future planned testing will validate these results and include additional materials of interest.

Optimization of Circulating Fluidized Bed Boiler Combustion Key Control Parameters Based on Machine Learning

During the coal-fired circulating fluidized bed unit participation in the peak regulation process of the power grid, the thermal automatic control system assists the operator to adjust the mode focusing on pollutant control and ignoring the economy so that the unit’s operating performance maintains a huge potential for deep mining. The high-dimensional and coupling-related data characteristics of circulating fluidized bed boilers put forward more refined and demanding requirements for combustion optimization analysis and open-loop guidance operation. Therefore, this paper proposes a combustion optimization method that incorporates neighborhood rough set machine learning. This method first reduces the control parameters affecting multi-objective combustion optimization with the neighborhood rough set algorithm that fully considers the correlation of each variable combination and then establishes a multi-objective combustion optimization prediction model by combining the online calculation of boiler thermal efficiency. Finally, the NSGAII algorithm realizes the optimization of the control parameter setting value of the boiler combustion system. The results show that this method reduces the number of control commands involved in combustion optimization adjustment from 26 to 11. At the same time, based on the optimization results obtained by using traditional combustion optimization methods under high, medium, and medium-low load conditions, the boiler thermal efficiency increased by 0.07%, decreased by 0.02%, and increased by 0.55%, respectively, and the nitrogen oxide emission concentration decreased by 5.02 mg/Nm3, 7.77 mg/Nm3, and 7.03 mg/Nm3, respectively. The implementation of this method can help better account for the economy and pollutant discharge of the boiler combustion system during the variable working conditions, guide the operators to adjust the combustion more accurately, and effectively reduce the ineffective energy consumption in the adjustment process. The proposal and application of this method laid the foundation for the construction of smart power plants.

Strain gauge measurements of an oscillating heat pipe from startup to stable operation

Oscillating heat pipe (OHP) devices offer high heat flow (Q) and low thermal resistance (Rth) capabilities with convenient form factors for applications in spacecraft and terrestrial thermal management. Though prior measurements have used intrusive strain measurements in a single OHP turn to study the complex thermal-fluid mechanisms of OHP operation, minimally-intrusive external strain measurements on the casing of a multi-turn OHP have not been previously reported. Here, we affix strain gauges to the exterior casing of an ammonia filled flat plate OHP and use strain measurements to quantify the frequency response of ammonia vapor pressure fluctuations over a broad Q range. For all Q, the Fourier transformed strain signals referenced to the Q=0 W background are well-described by a low-pass filter fitting function with a low-frequency amplitude a and characteristic “knee” frequency c. In all cases, a increases with increasing Q due to the enhanced vapor pressure fluctuations at larger thermal loads. In the startup regime of Q<10W, we observe large temporal deviations in the strain response, large Rth>0.1K/W, and c values that increase with increasing Q. In the stable operating regime for Q near 100W, we observe a stable frequency response, a minimum value of Rth=0.02K/W, and Q-independent c values that saturate near 10Hz. Our strain gauge findings are consistent with a mechanism of intermittent boiling near startup followed by stable vapor plug/liquid slug motion at higher Q. Thus, our measurements show that externally placed and minimally invasive strain gauges canprovide diagnostic capabilities and additional insight into operation in both the startup and stable regimes for multi-turn, lightweight OHP devices used in aerospace and terrestrial thermal management applications.

Design and research of integrated components for microsatellite thermal control system

With the increasing development of aerospace technology, micro satellites have attracted high attention in the aerospace field due to their advantages such as short development cycle, low system investment, and flexible launch methods. Their high level of internal equipment integration, high heat flux density, complex and uncertain working modes pose new challenges to thermal control design. At present, the thermal control design of micro satellites still mainly adopts passive methods, while active thermal control design has been widely used in the fluid circuit of large spacecraft, mostly in the “task oriented design mode”. Its high design cost, long cycle, poor adaptability and other characteristics cannot be applied to low cost, short cycle, and flexible launch methods of micro satellites. In response to the new problems brought by the high power density and low thermal inertia of microsatellites in thermal control design, this paper proposes an active thermal control fluid loop system suitable for microsatellites. In addition to the cold plate and radiator at the equipment end, other equipment forms an integrated component in the form of a shared substrate. The integrated component has the characteristics of miniaturization, lightweight, and rapid replacement of board and card. Through simulation and technical analysis of key components, We believe that this scheme is reasonable and feasible, providing a new design scheme for the thermal control design of subsequent micro satellites.

ИСПОЛЬЗОВАНИЕ ПОЛУПРОВОДНИКОВЫХ ЭЛЕМЕНТОВ ПЕЛЬТЬЕ В ГАЗОИСПОЛЬЗУЮЩЕМ ВАРОЧНОМ КОТЛЕ

Cooking boilers powered by natural gas are promising equipment for the preparation of feed in private farms. Based on the patent search, it has been established that there is a wide choice of gas-using boilers with different levels of automation of the process of thermal processing of the product and ensuring safety during operation. At the preliminary stage of the study, it was found that with a smooth control of the power of the gas burner of the digester during the preparation of feed, gas savings of up to 19% are achieved. The principle of self-regulation of gas consumption by a gas burner is determined in proportion to the heat flow consumed by the digester. A working experimental sample was made on the basis of an automation kit for a digester with smooth control of the power of a gas burner. A mathematical model has been developed that describes the processes of heat and mass transfer in a feed boiler with self-regulation of power. Based on the analysis of energy supply systems in digesters and heating boilers, the expediency of developing a new promising power self-regulation scheme based on Peltier semiconductor thermoelements has been established. As shown by the results of experimental studies of automation in various operating modes, the voltage on thermoelectric elements changes in proportion to the temperature difference. It is established that the minimum voltage is 0.07V, the maximum is 0.7V. The voltage and temperature of the product and hot steam in the jacket were measured using TEK DT 830B multimeters. It has been established that the best sensitivity of the thermal regime control system is achieved if the thermoelectric converter module is equipped with nine elements that change the output voltage in proportion to the temperature difference in the steam jacket of the digester.

Assessment of vibration suppression methods for spacecraft electric pump unit

This article characterizes the spacecraft as a means of performing various tasks, including by precision equipment. Emphasis is placed on vibration as one of the influencing factors and on the need for a low level of vibration on the spacecraft. Among the side effects of the electric pump unit of the thermal control system, the urgent task is to reduce vibration activity when developing a new model for advanced spacecraft. An integrated approach to solving the problem is indicated with the consideration of electric pump unit as a system and the selection of several directions to achieve the root-mean square value of vibration acceleration of 0,01g and below. Possible methods for reducing vibration activity in each of the directions and implemented solutions in the developed sample are described in detail. On several versions of electric pump unit for experimental determination of the level of root-mean square value vibration acceleration at a frequency of 5–1000 Hz. According to the results of the experiment, the contribution to the reduction of vibroactivity in several directions is estimated. It is concluded that only an integrated approach makes it possible to achieve a very low level of vibration activity of electric pump unit.

Heat transfer enhancement of modular thermal energy storage unit for reversible heat pump cooperation

The following article presents experimental comparison research on a hexagonal shelland-tube latent thermal energy storage (TES). Such shape of a shell was deliberately chosen instead of a cylindrical one due to its high modularity and with intent for future applications in automobiles (EV and PHEV) air conditioning systems (HVAC). Two geometries of helical coils, acting as tubes, were studied in this article. One was a simple helical coil with a small pitch. The other one was a helical coil with a larger pitch but enhanced with six longitudinal fins for each corner of the hexagon. Fins were added to study the effects of higher heat transfer area as well as effects of better thermal penetration of the Phase Change Material (PCM). Geometries of coils were matched with intent to occupy the same volume in the storage tank for a better comparison of the results. Results were also compared with previous studies carried out by authors for a copper pipe placed in a cylindrical shell. PCM chosen for this study was RT18HC due to its high value of latent heat and the melting temperature close to 18°C. Melting temperature value is crucial for applications in vehicle thermal control systems.

Experimental study on low pressure heat transfer properties of water evaporator with screen separation element

Water evaporator is often used in spacecraft thermal management as heat sink. In a water evaporator, heat is transferred from the microchannels of cooled glycol liquid to the external water, which causes the phase transition of water near external fins. Due to the severe weight requirements of hypersonic vehicles, it is very important to study the heat transfer performance and water utilization of water evaporator. The present study experimentally investigated the boiling heat transfer of water evaporator on external rectangular fins (RF) at low pressure, and the heat transfer of cooled glycol liquid in microchannels with offset strip fins (OSF). At the same time, the experiment explored the effects of three types of screen devices on the heat transfer performance and water utilization efficiency of water evaporators. The heat transfer experiments of water evaporator were conducted at the pressure of 11 kPa. The inlet temperature of hot glycol liquid was controlled 85 °C, and the mass flow rate were at 1500 kg/h and 2500 kg/h, respectively. The experimental results show that when the mass flow rate of ethylene glycol is the same, the water consumption of the water evaporator significantly decreases and the water utilization efficiency increase with the increase of screen density, but it can weaken the boiling heat transfer performance. In addition, the empirical correlation of boiling in low-pressure is modified, and the maximum deviation is within ±10%. The screen separator element and the new modified correlation provide a reference for the design of water evaporator.

Experimental analysis of heat and mass transfer in non-isothermal sloshing using a model-based inverse method

Nonisothermal liquid sloshing in partially filled reservoirs can significantly enhance heat and mass transfer between liquid and ullage gasses. This can result in large temperature and pressure fluctuations, producing thrust oscillations in spacecraft and challenging thermal management control systems. This work presents an experimental characterization of the thermodynamic evolution of a cylindrical reservoir undergoing sloshing-induced thermal de-stratification. We use a 0D model-based inverse method to retrieve the heat and mass transfer coefficients in planar and swirl sloshing conditions from the temperature and pressure measurements in the liquid and the ullage gas. The experiments were carried out in the SHAKESPEARE shaking table of the von Karman Institute in a cuboid quartz cell with a cylindrical cut-out of 80 mm diameter in the center, filled up to 60 mm with the cryogenic replacement fluid HFE-7200. A thermal stratification with ΔT=25 K difference between the ullage gas and liquid was set as the initial conditions. A pressure drop of 90% in the ullage gas was documented in swirling conditions. Despite its simplicity, the model could predict the system’s thermodynamic evolution once the proper transfer coefficients were derived.

Prospects of thermal comfort management process automation

Purpose. Increasing the efficiency of the building's energy system by taking into account the interrelationship of energy sources, thermal protection, indicators of thermal comfort and microclimate parameters of the premises. Taking into account the changes in the requirements of the European Union for indoor temperature and modern economic challenges, the main goal is to develop a system for automatic control of thermal comfort in a given temperature range with minimization of energy costs. Today, there are already many installed heating and cooling air systems. Based on this, the development of a universal device for maintaining thermal comfort in the room is promising. The methods. To conduct an analysis of the developed approaches to increase the efficiency of the energy system of the building in terms of thermal comfort, to determine the features and possibilities of the energy analysis of heat and taking into account the limitations of human thermal comfort. Findings. The proposed structure of the thermal comfort regulator will make it possible to develop a universal regulator that can be used in heating and air cooling systems, or in combined systems. Improving the quality of indoor temperature control can be achieved by directly managing thermal comfort based on the predicted average PMV score and the predicted percentage of dissatisfied PDD. The originality. Typical approaches to managing indoor comfort based on temperature do not take into account radiation, humidity, air speed, clothing and user load, which leads to both the creation of uncomfortable conditions and excessive use of energy resources. For the first time, in accordance with DSTU B EN ISO 7730:2011, the structure of the thermal comfort control system was proposed, its input and output parameters and ways of obtaining non-measurable parameters were defined. The control system based on the predicted average PMV score and the predicted percentage of dissatisfied PDD determines the level of thermal comfort in the room and reduces the number of dissatisfied users. Management based on the predicted average PMV score ensures a reduction in the use of energy resources while maintaining the minimum acceptable thermal comfort indicators. Practical implementation. The resulting structure can be used in the development of new thermal comfort control systems. Taking into account the presence of a large number of already existing heating and air cooling systems, it is proposed to use thermal comfort regulators to improve the quality of their functioning. The proposed approach through the use of the thermal comfort model will make it possible to determine the heating needs under different comfort conditions, reduce the energy consumption of the building without harming human health, and assess the possibility of increasing energy efficiency by changing the comfort conditions, thermal protection parameters and the microclimate of the premises.

Design and test of a compact capacitor-based energy storage pulsed power module with high repetitive discharge frequency

Advance in electromagnetic launch have put forward higher requirements for the pulsed power supply(PPS). A capacitive PPS for electromagnetic launcher has been constructed in NJUST recently with a basic cell of 220kJ energy storage, which has a good scalability. Design of integrated 220kJ pulsed power unit (PFU) was demonstrated in the paper. To meet the requirement of compact structure of PPS, the device design and system layout are considered and combined with simulation to optimize the magnetic field distribution in the constrained space. In order to achieve the function of continuous discharge, the reliability of thermal management system, control system and safety protection system are focused on. System description was presented in the paper. A series of experiments were conducted to verify the performance of the module. The results show that the PFU shows good reliability in 10 consecutive burst-shot tests. Due to the modular setup of this pulse formation network, it can be extended to a larger-scale pulse forming network. Flexible current pulse shapes can be formed by controlling the charging voltage and the trigger time of the PFU.

The “Effect of Marangoni Convection on Heat Transfer in Phase Change Materials” experiment

Present as well as future challenges of space exploration point to the need for improved thermal control systems. The “Effect of Marangoni Convection on Heat Transfer in Phase Change Materials” experiment, which is approved by ESA for execution on board the International Space Station, aims to contribute directly to current knowledge and basic understanding of heat and mass transport in phase change materials (PCMs) that incorporate a free surface in reduced gravity. The experiment will apply fixed temperatures to opposite ends of PCM samples held in cuboidal and cylindrical containers in order to drive controlled melting and solidification cycles that will be observed by means of optical cameras. The recorded images will be complemented by thermal measurements at key positions along the samples, which will allow different thermocapillary flow regimes to be distinguished according to their temporal dynamics. It is anticipated that thermal Marangoni (thermocapillary) convection will increase the heat transfer rate in these PCM devices by a significant factor (on the order of two or more) compared to melting governed by thermal diffusion (conduction). If the PCM designs prove robust, the experiment results can be expected to lead to substantial improvements in future designs for passive PCM applications in space missions.