Thermal Control System Research Articles

Experimental Operation of a Prototype 750C Advanced Chloride Molten Salt Bellows Valve

To achieve DOE 2030 SunShot targets that reduce the cost of liquid-based solar by an additional 40% to 70% beyond 2018 costs, a more reliable, highly manufacturable flow valve, capable of achieving operational temperatures of >700°C is required [1]. This paper investigates the development of an innovative high-temperature chloride molten salt valve, with operation up to 750°C. This valve is intended to be employed within Gen 3 CSP liquid-based thermal energy storage (TES) systems as well as Gen 4 modular salt reactor (MSR) technologies. This work details the general design and flow testing of a bellows-seal flow control valve (FCV). This design includes an integrated closed-loop thermal control system to ensure robust design for freeze-thaw cycles. The self-contained thermal management STM system, is unique in the salt valve industry since it is an integrated solution to provide a consistent, repeatable alternative to typical heat tracing. Additionally, the design includes the employment of a novel heat pipe valve stem to facilitate enhanced passive thermal management into the valve assembly. This valve stem heat pipe is designed to facilitate natural circulation within the bonnet to ensure robust operation, during both nominal and transient thermal operation. The valve body and trim will be designed using SS316H, consistent with Flowserve Corporation’s existing product base and is code qualified but will utilize clad material for materials corrosion, manufacturing cost reduction and compatibility to ensure design flexibility. A test campaign was performed in this investigation utilizing a novel 750°C ternary chloride (20%NaCl/40%MgCl2/40%KCl by mol. wt. %) molten salt flow loop. A discussion about the design and installation of the valves within this test bed is provided for this investigation. Valve test results from this study assessed Cv curves as well as multiple actuator cycles, under varying thermodynamic and operational mode conditions, which would be characteristic within a commercial molten salt facility. The results indicate nominal operation for the baseline design, though improved performance and reliability is expected with the full designed FCV.

Study on the thermal control performance of lightweight minimal surface lattice structures for aerospace applications

With the rapid evolution of aerospace technology and the increasing complexity of space environments, the demand for lightweight, thermally insulated, and highly efficient heat dissipation materials in aircraft equipment has surged. This study addresses this critical need by investigating Triply Periodic Minimal Surface (TPMS) lattice structures, offering a novel design approach to enhance spacecraft thermal management under extreme temperatures. Our work introduces a methodology to quantitatively assess the thermal insulation and heat dissipation performance of various lightweight lattice sandwich structures. We constructed implicit function models of low volume fractions, including Gyroid, Diamond, Primitive, and IWP, and conducted experiments using an active cooling setup under controlled heating conditions at 300 °C. Key findings reveal that, at flow velocities ranging from 0.25 to 1.5 m/s, the Diamond model exhibited the highest convective heat transfer coefficient, surpassing the Gyroid, Primitive, and IWP models by 6.9 % to 427.3 %, 87.1 % to 485.6 %, and 1.5 % to 98.7 %, respectively. Conversely, at velocities between 1.5 and 3.75 m/s, the Gyroid model demonstrated superior heat exchange performance, improving by 14.6 % to 67.2 %, 73 % to 167.7 %, and 9 % to 64.8 % compared to the Diamond, Primitive, and IWP models. During thermal insulation tests at temperatures from 200 to 400 °C, the Diamond model showed the best insulation effect, while the Primitive model performed poorly. Based on the experimental data, we established empirical relationships between the Nusselt number, friction coefficient, and Geometric Surface Ratio (GS). These findings not only underscore the significant potential of TPMS lattice structures in aerospace applications but also provide a robust theoretical framework and practical guidelines for achieving efficient thermal management in lightweight aerospace manufacturing.

Achieving high robust aluminum alloy annular laser directed energy deposition based on thermal field assistance system

High thermal conductivity and large fluctuations in laser absorptivity with temperature make aluminum alloy prone to deformations, collapses, spheroidization, and other defects during directed energy deposition (DED) processes. To achieve stable and high-quality annular laser DED (AL-DED) of aluminum alloy, an in situ thermal field assistance system was designed, wherein a preheating-cooling temperature control thermal balance model was established. The thermal field assistance system effect during the AL-DED process of AlSi10Mg has been evaluated, and the control ability of the thermal balance model on absorptivity and temperature field has been analyzed. A continuous 500-layer AL-DED forming of the aluminum alloy was conducted. The results indicate that the in situ thermal field assistance control system can achieve thermal balance during the aluminum alloy component AL-DED process, causing stable laser absorption rate and uniform temperature fields, while reducing surface roughness of components to 2.3 μm. The microstructure and elemental distribution were uniform, transforming the Al–Si eutectic structure from a mesh-like to a dispersed distribution and, consequently, achieving the deposition of a 500-layer, 2.0 mm-thick Al thin-walled component with high dimensional accuracy and stability. This thermal field assistance system effectively improves the stability of absorptivity and the thermal field, providing novel ideas for high-quality AL-DED additive manufacturing of materials sensitive to thermal fields and large absorptivity fluctuations, such as aluminum and copper.

Thermal Design and Experimental Validation of a Lightweight Microsatellite

The multiple working modes, complex working conditions, frequent changes in external heat flux, and high-power consumption of satellites all pose great difficulties to their thermal design. In this paper, the material MB15 magnesium alloy was used, which has not been performed for the main structure of satellites. This material not only reduces the weight of the structure and the launch cost, but also its good thermal conductivity is very helpful for the thermal control design of the satellite. This paper mainly describes the design of a thermal control system for lightweight microsatellites. Firstly, the satellite structure, thermal control indices of the main equipment, and the power consumption of the equipment in different working modes are introduced. Then, the external heat fluxes are analyzed, the position of the heat dissipation surface and extreme conditions are confirmed, and detailed thermal designs of each part of the satellite are determined via the combination of active and passive thermal control. Finally, the thermal balance test is carried out for the whole satellite. It is found that the deviation between the temperature of the thermistor and thermocouple at the same moment in the thermal analysis simulation data and thermal balance test is generally within 0.5 °C, and the maximum difference is not more than 1.7 °C, which indicates that the simulation model is well established and that the thermal analysis is reliable.

Thermally Conductive Shape-Stabilized Phase Change Materials Enabled by Paraffin Wax and Nanoporous Structural Expanded Graphite.

Paraffin wax (PW) has significant potential for spacecraft thermal management, but low thermal conductivity and leakage issues make it no longer sufficient for the requirements of evolving spacecraft thermal control systems. Although free-state expanded graphite (EG) as a thermal conductivity enhancer can ameliorate the above problems, it remains challenging to achieve higher thermal conductivity (K) (>8 W/(m·K)) at filler contents below 10 wt.% and to mitigate the leakage problem. Two preparations of thermally conductive shape-stabilized PW/EG composites, using the pressure-induced method and prefabricated skeleton method, were designed in this paper. The expanded graphite formed a nanoscale porous structure by different methods, which enhanced the capillary action between the graphite flake layers, improved the adsorption and encapsulation of EG, and alleviated the leakage problem. The thermal conductivity and the latent heat of the phase-change materials (PCM) prepared by the two methods mentioned above are 9.99 W/(m·K), 10.70 W/(m·K) and 240.06 J/g, 231.67 J/g, respectively, at EG loading by 10 wt.%, and the residual mass fraction was greater than 99% after 50 cycles of high and low temperature. In addition, due to the excellent thermal management capability of PW/EG, the operating temperature of electronic components can be stably maintained at 68-71 °C for about 15 min and the peak temperature can be reduced by at least 23 °C when the heating power of the electronic components is 10 w. These provide novel and cost-effective methods to further improve the management capability of spacecraft thermal control systems.

A Comprehensive Assessment of the Economic Performance of an Innovative Solar Thermal System: A Case Study

An economic assessment of an innovative solar thermal system called Application to Solar Thermal Energy to Processes (ASTEP) was conducted. It considered its three main subsystems: a novel rotary Fresnel SunDial, Thermal Energy Storage (TES) and Control System. Current Fresnel collectors are unable to provide thermal energy above 150 °C in high-latitude locations. Therefore, the key contribution of this study is the assessment of the economic performance of the ASTEP system used to provide high-temperature process heat up to 400 °C for industries located at low and high latitudes. The ASTEP system is installed at two end-users: Mandrekas (MAND), a dairy factory located in Greece at a latitude of 37.93 N and ArcelorMittal (AMTP), a manufacturer of steel tubes located in Romania at a latitude of 47.1 N. The life cycle costs (LCC), levelised cost of energy (LCOE), energy cost savings, EU carbon cost savings and benefit–cost ratio (BCR) of the ASTEP system were assessed. The results showed that AMTP’s ASTEP system had higher LCC and LCOE than MAND. This can be attributed to the use of two TES tanks and a double-axis solar tracking system for AMTP’s ASTEP system due to its high latitude location, compared to a single TES tank and single-axis solar tracking system used for MAND at low latitude. The total financial savings of the ASTEP system were EUR 249,248 for MAND and EUR 262,931 for AMTP over a period of 30 years. This study demonstrates that the ASTEP system offers financial benefits through its energy and EU carbon cost savings for industries at different latitudes while enhancing their environmental sustainability.

Design, analysis and verification of thermal control system for satellite laser communication terminal

Design, analysis and verification of thermal control system for satellite laser communication terminal

Performance analysis on an integrated three-area thermal AGC system with various wind velocities considering HCSA-optimized PI-TIDN Controller

This article investigates the impact of a high-voltage direct-current (HVDC) link and a wind turbine system (WTS) on the dynamics of a three-area thermal automatic generation control (AGC) system. A novel controller, the cascade of proportional-integral (PI) and tiltintegralderivative (TID) with filter coefficient (N) (PI-TIDN) controller is projected. The WTS units are subjected to various wind velocity scenarios, including fixed and random wind velocities. The controller parameters are concurrently enhanced using the hybrid crowsearch algorithm (HCSA). The system dynamics corresponding to the PI-TIDN controller are superior to those of PIDN and TIDN controllers. Additionally, studies with different wind velocities demonstrate that responses with fixed wind velocities are better than those with random wind velocities. Moreover, integrating WTS units with the thermal system improves dynamics compared to the thermal system alone. It is also apparent that the parallel AC-HVDC system enhances dynamics. Furthermore, sensitivity analysis exposes that the PI-TIDN controller values at nominal settings are vigorous and do not require retuning.

Gamma‐ray and neutron attenuation of carbon fiber/epoxy composites with carbon nanotubes and boron nitride nanoparticles for passive shielding applications in space

AbstractComposite materials have made far‐reaching changes in the space industry since they have been adopted into the structural and thermal control subsystems of space vehicles because of their several multi‐functions, including being lightweight as well as having advanced mechanical and thermal properties. The use of composites as space radiation shielding materials is also one of the most crucial applications because space radiation is a major impediment for current and future deep‐space missions. Investigation of carbon fiber composites with a diverse array of element and nanoparticle reinforcements has revealed their potential as an alternative to conventional radiation shielding materials in space. This study focused on the alleviation of gamma‐ray and neutron radiation by carbon fiber/epoxy composites incorporated with various weight ratios of carbon nanotube (CNT) and boron nitride (BN) nanoparticles. A narrow beam geometry setup was used for gamma radiation tests with a Cs‐137 gamma‐ray source, while neutron radiation experiments were conducted in a neutron howitzer with a 239Pu‐Be neutron source. Six groups of specimens, namely, pure carbon fiber/epoxy, 0.5 wt% CNT, 0.5 wt% BN, 0.5 wt% CNT + 0.5 wt% BN, 1 wt% CNT + 1 wt% BN, and 2 wt% BN, were examined against these two types of radiation. Results have indicated that the 2 wt% BN specimen showed the best attenuation properties against both gamma‐ray and neutron radiation among all tested specimens; furthermore, it was almost three times more effective against neutron radiation than against gamma‐ray radiation.Highlights Varying weight ratios of CNT and BN nanoparticles used for radiation shielding. A Cs‐137 gamma‐ray source used in narrow beam geometry. Neutron radiation studies were conducted in a 239Pu‐Be neutron howitzer. The 2 wt% BN sample showed the best attenuation against gamma‐ray and neutron radiation. It resulted in an HVL of 6.86 cm for gamma‐ray radiation and 2.13 cm for neutron radiation.

Thermodynamic Analysis of Cyclic Operation of On-Board Nanoporous Carbon-Based Adsorbed Methane Storage Tank with Various Thermal Control Systems

Thermal effects of adsorption and desorption, leading to temperature fluctuations and losses of adsorption storage systems capacity in the processes of gas charging and discharging, are the main obstacle to the wide practical application of adsorbed natural gas (ANG) technology. This work presents a numerical simulation of heat and mass transfer processes under various cyclic operation modes of a full-scale adsorption storage tank with various thermal control systems. The high-density monolithic adsorbent KS-HAM, obtained on the basis of industrial activated carbon KS-HA, was used as the adsorption material. The phase composition, surface morphology, and porous structure of the sorbents were studied. The adsorption of methane on the KS-HA adsorbent was measured. It is shown that increasing the duration of charging leads to obtaining additional capacity of the ANG system; however, the final efficiency and benefit at the end of the charging–discharging cycle are determined by the efficiency of the thermal control system and the gas-discharging mode. It has been shown that the presence of a finned thermal control system allows for charging the adsorption storage tank 3–8 times faster and provides an 8–24% greater amount of gas discharged at the discharging stage compared to the ANG system without fins.

In-orbit validation of a ferrofluidic Thermal Switch in ISS microgravity

AbstractFerrofluids offer a wide range of applications by enabling wearless systems for future space missions. As part of the FARGO (Ferrofluid Application Research Goes Orbital) project, an active Thermal Switch using ferrofluid was developed and validated during a 26-day International Space Station (ISS) mission. This experiment was conducted as part of the Überflieger2 competition organized by the Space Agency within the German Aerospace Center (DLR). Thermal management of spacecraft (S/C) and satellites is a universal challenge. In the development of thermal management components, it is therefore essential to minimize or even eliminate stress/strain peaks and potential safety risks for S/C operation and payloads induced by thermal differences. The thermal management system shall be able to keep all components within their acceptable temperature ranges. This shall be achieved under all orbit conditions, for example, when solar irradiance heats one side of the S/C resulting in possibly unwanted temperature gradients toward the cold vacuum of space. An active Thermal Switch allows heat flows to be routed along different paths within the S/C depending on the prevailing conditions. Within project FARGO, an active Thermal Switch was tested during an ISS mission. Tests on the ground already verified a measurable difference in thermal conductivity depending on the state of the switch. Magnetically moving the ferrofluid allows the creation of a thermally isolating and conducting Thermal Switch state. The ferrofluid utilized for the FARGO experiment is EFH-1 with a thermal conductivity of $${0.19\,\mathrm{\text {W}\text {m}^{-1}\text {K}^{-1}}}$$ 0.19 Wm - 1 K - 1 . The Thermal Switch consists of two silver rods in line, acting as heat conductors, separated by an airgap. One side of the switch is heated, and the other one cooled by one thermoelectric cooler (TEC) each. The gap between the conductors can be bridged by ferrofluid moved via magnetic fields. As the EFH-1 has a higher thermal conductivity k than air, thermal conductive change is achieved by switching. The temperature difference between hot and cold side are measured in the ON state as well as the OFF state. From these measurements, the switching ratio as a performance characteristic is calculated. The switch was tested under various heat loads and switching times. Electropermanent magnets (EPMs) are magnets that can be magnetically switched on and off by a current pulse. Compared to conventional electromagnets, heat generation and power generation are significantly reduced. In addition, the switch remains reliably in the selected state, even if a failure of the control electronics occurs, making it bi-stable. Moreover, electric power is only required to switch the state of the EPM, but not to maintain it.

Green building interior design based on digital image processing and thermal environment simulation

With the increasingly severe global climate change and energy crisis, this study aims to explore effective strategies for green building interior design, especially in terms of thermal environment control, through digital image processing and thermal environment simulation. The study simulates indoor scenes based on image processing technology, using methods such as image acquisition, localization, and object detection to improve the accuracy of scene reconstruction, and conducts in-depth analysis of detection effects, laying the foundation for subsequent thermal environment simulations. In the design of the thermal energy environment control system, the calculation of indoor cooling load was studied and compared with existing thermal environment models to determine the impact of user activities on the indoor thermal environment. By establishing a thermal energy environment control model and implementing precise environmental regulation for different usage scenarios, indoor comfort and energy efficiency have been significantly improved. The experimental results show that the use of digital image processing simulation technology can effectively improve the accuracy and flexibility of indoor thermal environment control in green buildings, optimize energy efficiency, emphasize the importance of thermal factors in interior design, and provide theoretical basis and practical guidance for future building design practices.

(Invited) Improving Low-Temperature Lithium-Ion Battery Performance through 3D Structure-Controlled Anodes with Optimized Charge Storage Mechanisms

The performance of lithium (Li)-ion batteries (LIBs) significantly decreases at low temperatures, primarily due to the slow diffusion of Li ions within the graphite anode. This issue often necessitates the use of complex thermal control systems to safeguard the batteries, enhancing their cost, mass, and volume, especially under extreme conditions. Here, we introduce both structure-controlled graphene and graphite composite anodes, which employ controlled charge storage mechanisms to accelerate Li-ion charge storage kinetics and maintain structural stability under low-temperature conditions. [1-3] By transitioning from layered graphite to crumpled graphene or expanded graphite (composite), we effectively utilize diffusion- and surface-controlled charge storage mechanisms. These structure-controlled anodes exhibit superior rate capability and exceptional performance at temperatures as low as -50 °C. Through comprehensive low-temperature analyses, this research provides a detailed understanding of the relationships between anode structure, charge storage mechanisms, and performance under low-temperature conditions. Our findings offer valuable insights for the development of advanced energy storage devices optimized for low-temperature operation.

Development of an experimental unit and methodology for ground-based experimental testing of two-phase thermoregulation systems for spacecrafts

This article presents a detailed description of an experimental setup for testing two-phase thermal control systems of spacecraft. The setup is a climatic chamber for simulating real operating conditions of elements in the subzero temperature range and includes three circuits: a coolant pumping circuit corresponding in parameters to the thermal control system under study, a cooling system circuit, and a thermal load simulator circuit. Electric heating elements are used as a thermal load simulator. Transparent inserts provide the ability to visually monitor the structure of a two-phase flow during boiling and estimate the volume content of the vapor phase. A testing methodology was developed for the installation under consideration, including a testing algorithm and a description of the software and hardware testing tools. The software and hardware testing tools include electronic measuring tools for the main parameters of the operating modes of the two-phase thermal control system and an automated testing process control system. The developed automated testing process control system provides the ability to monitor a wide range of thermal and physical parameters of the coolant at various points in the circuit. The control system is based on the use of programmable logic controllers. To automate the operation of the installation, the OWEN PLC200 controller is used in the stand – a monoblock controller with discrete and analog inputs/outputs, designed to control and manage the operating modes of small systems. The software part of the algorithm is based on the CODESYS environment. The results obtained in the work can be used in planning and implementing programs for ground-based experimental testing of two-phase thermal control systems, in developing test stands for conducting research on spacecraft systems.

Fuzzy TOPSIS optimization of MHD trihybrid nanofluid in heat pipes

Heat pipes have the potential to benefit from nanofluid flow between coaxial cylinders. Heat is effectively transferred from one place to another by means of heat pipes. Heat pipes can be used for electronics cooling, spacecraft thermal management, and heat recovery systems by adding nanofluids, which enhances the heat pipe's thermal conductivity and heat transfer capability. This work aims to discover an approximate solution for the flow of a trihybrid nanofluid (THNF) consisting of graphene, copper, and silver between two coaxial cylinders in magneto-hydrodynamics, taking into account the broad variety of applications. The nanomaterial is tested in a system with a fixed inner cylinder and a rotating outer cylinder. It contains graphene, copper, silver, and kerosene oil as the base fluid. For examining the flow characteristics, magnetic field is applied along radial direction of the cylinder, while inner cylinder is fixed, and outer cylinder is rotating. Moreover, temperature of the outer cylinder is higher than the lower cylinder. The objective of this study is to develop a mathematical model of the problem and solve the governing equation numerically using the MATLAB built-in routine called bvp4c. Additionally, we identify the most effective physical parameter to optimize the heat transfer rate using Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). Using a variety of factors, we calculate fluid velocity, skin friction, temperature, and Nusselt number graphically. According to the study, higher Brinkman numbers (Br) and magnetic parameter (M) characteristics lead to higher temperatures. Furthermore, Fuzzy TOPSIS shows that alternative A11 (ϕ=(0.9,1.0,1.0),M=(0.5,0.7,0.9),Br=(0.9,1.0,1.0)) has the maximum heat transfer rate, while another A8 (ϕ=(0,0,0.1),M=(0,0,0.1),Br=(0,0,0.1)) has the lowest.

Electric Vehicle Energy Management via Traffic Light Detection and Segmental Velocity Forecasting

Abstract Predictive-based power control has been widely recognized as a promising approach to boost driving range and improve system-level energy efficiency for electric vehicles (EVs), in which vehicle velocity forecasting generally serves as a preliminary input to optimally schedule the operations of varying onboard electrical and thermal systems. A segment-based velocity forecasting approach for individual commuting vehicles developed in this study reveals that it is challenging to forecast the velocity at intersection segments only using the velocity data. To address this challenge, this study seeks to develop a YOLO-V2-based object detection deep network to recognize the traffic lights in advance and leverage the detected signals to establish a forecasting model that integrates with the probability-based hybrid forecasting approach. The case study results show that the traffic light detection-based forecasting model can significantly improve the forecasting accuracy for intersection segments. Based on the forecasting velocity 5–15 s ahead, the effectiveness of model predictive control-based energy management strategy is further evaluated with a liquid-based battery thermal control system. The proposed battery thermal management system (BTMS) model shows promising results in maintaining battery temperature within an appropriate range, thus improving the overall energy efficiency of the EV. Moreover, a traffic light-based real-time energy management framework is developed to directly control the power demand from the air conditioning (AC) system.

Investigation on the heat transfer characteristics of thermal control system based on phase change material coupled with three-dimensional arrayed pulsating heat pipe

The rapid development of electronic devices necessitates reliable thermal control systems for efficient thermal management. The combination of pulsating heat pipes (PHPs) with phase change materials (PCMs) facilitates uniform and efficient thermal regulation. This study presents a novel coupled thermal control module that integrates a three-dimensional arrayed pulsating heat pipe (3D-APHP) with a dual-plane and arrayed structure and solid-solid PCM composites. The heat transfer characteristics of the 3D-APHP, the phase change characteristics of the PCM composites, and the interaction between the 3D-APHP and PCM composites under different heating powers and filling rates were experimentally investigated. The results show that the latent heat absorption properties of the PCM composites significantly reduce the temperature fluctuation range and pulsation amplitude of the 3D-APHP, enhancing the temperature uniformity and lowering the overall temperature of the 3D-APHP by approximately 3–10 °C. The efficient thermal conductivity mechanism of the 3D-APHP ensure that the axial temperature difference of the PCM composites is controlled within 10 °C and the radial temperature difference is controlled within 1.5 °C, effectively promoting uniform heat distribution and enhancing the overall temperature rise rate. Additionally, in passive operating mode, the overall temperature difference of the 3D-APHP is smaller and the heat transfer stability is enhanced; in passive/active coupling operating mode, the average temperature of the evaporation section of the 3D-APHP decreases and the thermal response speed increases. The working characteristics of these two modes can be applied to different scenarios, highlighting the innovative integration of PHPs and PCMs in advanced thermal management solutions.

Design of thermal management system for high-power liquid-cooled charging pile

Abstract High-power ultra-fast charging causes the charging gun to rapidly heat up, posing safety hazards. Therefore, the focus of the research is on thermal management during the overcharge process. To address this, a novel thermal management control system (TMS) for high-power liquid-cooled charging piles has been designed. The liquid circulation channels connect the cables and the charging gun, with coolant flowing through the pipes. A pump delivers the coolant to the charging gun to remove heat. The TMS monitors temperature, pressure, and flow to control the oil pump and fan speeds, maintaining the perforating gun temperature within a preset range and managing the system’s heat. This TMS system enables the liquid-cooled charging cables to carry larger currents, significantly enhancing charging power.

Experimental study on thermal performance of a novel serpentine-looped flat microchannel heat pipe

The pulsating heat pipe is an efficient heat transfer element widely used in a variety of applications due to the simple wickless structure and no external power requirements. Increasing the number of pipe turns can enhance the pulsation, but reduce the structural compactness. A new type of serpentine-looped flat microchannel heat pipe (SLFMHP) is proposed with numerous turns by series connection of flow channels and good thermal contact by large flat surface. The thermal performance of SLFMHP is experimentally investigated and compared with that of the copper pulsating heat pipe. Results show that the minimum thermal resistance of SLFMHP is 0.036 K/W, 80 % smaller than 0.19 K/W of the copper pulsating heat pipe. The maximum effective thermal conductivity of SLFMHP reaches 37400 W/(m·K), five times of 7233 W/(m·K) of the copper pulsating heat pipe. The sensitivity to inclination angle has also been reduced with thermal resistance at 0° improved by over 90 %. As the inclination angle increases, the thermal resistance decreases first sharply and then slowly, and the turning point is defined as the critical pulsation angle, about 15° and 8° with the filling ratio of 20 % and 40 %, respectively. The SLFMHP can provide a possible solution for the demand of the thermal control systems with miniaturization, light weight and high heat transfer capability.

Hydraulic Performance Comparison of Centrifugal Closed Impellers Fabricated by Means of Additive Manufacturing and Classical Machining for Space Active Thermal Control Systems of Satellites

The current paper addresses the challenges in manufacturing a critical component of a centrifugal pump for space active thermal control systems of satellites, namely, the closed centrifugal impeller. Compared to the classical technologies, there is an obvious advantage of additive manufacturing of closed impellers, due to the possibility of creating complex geometries, which boost the hydraulic performances of the part and, implicitly, of the pump. In this regard, the authors performed a comparative analysis between a closed impeller obtained by classical machining and three manufactured by additive technology (selective laser melting) by means of dimensional inspection, non-destructive testing, and experimental evaluation. The study performed here showed that the additively manufactured closed impellers exhibited similar hydraulic performances to the classical one, without the need for performing post-processing of internal surfaces. Also, in terms of dimensional and geometrical stability, the additively manufactured closed impellers were within the imposed tolerances, demonstrating the feasibility of obtaining such complex parts by using additive manufacturing. Subsequently, the allocated time for manufacturing decreased by 75% for the closed impellers manufactured by additive technologies, and the need for using four technological processes was decreased to only two, printing and post-processing.