Advanced Research Thermal Passive Exchange (ARTE) - 10.04.17

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Temperatures in space change dramatically from extreme heat to extreme cold, but transferring warmth from heat-producing components such as electronics is an efficient way to heat colder areas or to cool down heated areas or equipment. Advanced Research Thermal Passive Exchange (ARTE) studies the performance of a new type of heat pipe, which is a passive, low-weight device used to increase a material’s heat transfer capability. The investigation researches a new technology, called Axially Grooved Heat Pipes, which could be integrated into existing spacecraft, as well as used for future missions.
Science Results for Everyone
Information Pending

The following content was provided by David Avino, M.S., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom: Thermal Exchange

Principal Investigator(s)
Nicole Viola, Professor, DIMEAS - Dipartimento di Ingegneria Meccanica e Aerospaziale, I Facoltà di Ingegneria, Politecnico di Torino, Torino, Italy

David Avino, M.S., Argotec Srl, Torino, Italy
Joel L. Plawsky, Sc.D., Rensselaer Polytechnic Institute, Troy, NY, United States

Argotec, Torino, Italy

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Italian Space Agency (ASI)

Research Benefits
Space Exploration, Earth Benefits

ISS Expedition Duration
September 2015 - March 2016; March 2016 - September 2016; September 2017 - February 2018

Expeditions Assigned

Previous Missions

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Experiment Description

Research Overview

Heat pipes are passive devices used to transfer heat. They are used in several branches of engineering, and one of the most important applications is in space. For example, they could be used to transfer heat produced by avionic systems to cooler, remote locations. By knowing the amount of power to be dissipated, it is possible to design appropriate heat pipe devices which are able to satisfy the heat transfer requirement, with reduced costs, mass, and dimensions.
Heat pipes rely on liquid/gas phase change to transport heat, and capillary pressure to transport mass. If one end of the heat pipe (evaporator) is heated, the fluids in contact with that surface evaporate. Fluid vapor is at a higher pressure than the vapor in contact with the surface at the opposite end of the device (condenser). Thus, vapor flows from the evaporator to the condenser, releases its latent heat of evaporation and condenses. The liquid travels back to the heated end due to capillary action. To increase the capillary action, several grooves are created inside the heat pipe. Such a grooved device is filled with pure fluids or mixtures such as pentane-isohexane (5% wt), and self-rewetting fluids (like water-butanol) to improve performance via Marangoni phenomena.
Several tests are planned to verify if the performance in space is different from the ground, and to obtain correlation laws. During the ground and on-board tests, hysteresis (delay of response) effects are also analyzed to assess the flight readiness for future integration in real space applications.
Ground experiments cover an essential role in proving the applicability of the heat-pipe systems in other fields, such as aeronautics and renewable energy applications.


The aim of Advanced Research Thermal Passive Exchange (ARTE) is to evaluate the performance of heat pipes, passive heat transfer devices used to increase the effective conductivity of a material while keeping the overall mass low, generally used in space, aeronautical, renewable energy, and industrial applications.
Heat pipes rely on phase change to transport heat and capillary pressure to transport mass. If one end of the heat pipe (evaporator) is heated the fluid in contact with that surface evaporates. Fluid vapor is at a higher pressure than the vapor in contact with the cooler surface at the opposite end of the device (condenser). Thus, vapor flows from the evaporator to the condenser, releases its latent heat of evaporation and condenses. The liquid travels back to the heated end due to capillary action. Meanwhile, the menisci in the corners change shape to create the capillary pressure gradient needed to pump the liquid to the heated end.
Up to now, a few number of heat pipes have been tested in microgravity environment. However, no research has been carried on applying real working conditions. The goals of this experimental analysis are to perform tests (on ground and in flight) on Axially Grooved Heat Pipes, about 20 cm long, with a circular section, filled with pure fluids or mixtures like pentane-isohexane (5%wt) and self-rewetting fluids (water-butanol) in real working conditions (10°C -100°C). The experiment uses low toxicity fluids that, unlike the ones currently used on the external ISS thermal loops (i.e. ammonia), make this investigation compatible with future human exploration applications.
The large number of experiments conducted on heat pipes in Earth’s gravity conditions has strongly contributed to increased knowledge on their performance. However, their behavior in microgravity environment is still to be investigated. Hence, this research on the International Space Station (ISS) could be an important milestone to design a completely passive device suitable on a wide range of applications.
The starting point for designing the device has been mainly taken from existing literature. To reduce dimensions and mass, the heat pipes are made of aluminum (Al-6060 or other aluminum alloys certified for space applications) instead of copper. Aluminum has a lower density than copper, which reduces the mass, and it is characterized by a lower fluids contact angle, which increases the capillary action.
The capillary pressure, that could be considered the driving force of the device, is generated by several grooves in the axial direction. Grooves promote the return of the liquid phase to the condenser reducing the risk of dry out phenomena]. The design of the grooves is based on the analysis of capillary pressure, pressure losses in micro-channels and pressure losses in the vapor phase. A first set of results suggests the use of rectangular grooves instead of triangular ones.
As already mentioned, the heat pipes are filled with pure substances or mixtures, as pentane-isohexane (5% wt). Pentane has already been used in a previous experiment on board the ISS, the Constrained Vapor Bubble (CVB) experiment.
Other literature sources suggest the use of self-rewetting fluids (e.g. water-butanol) to improve performance due to the Marangoni effect. Therefore, heat pipe performance with these fluids could be tested.

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Space Applications
The Heat Pipe is a simple device that is currently used for the heat transfer in different space and ground applications. The present experiment aims at increasing the real performance of a grooved Heat Pipe in microgravity, in order to give an important input for their near future use in space systems. In the wide field of the heat dissipation, the heat pipe represents one the best passive solutions to reduce the system complexity and mass, enhancing the reliability and the performance offered by a common active heat exchanger. Such a design makes Heat Pipes suitable to a wide range of space applications, such as cooling of microelectronic components and satellites, and space vehicles thermal control systems. Furthermore, their simple design allows an easy integration with any existing systems, reducing the production costs. The passive heat transfer reduces the need for remote control of the on-board thermal system. In addition, the use of low toxicity fluids (such as pentane-isohexane mixtures) allows the use of these kinds of heat pipes inside the space module, satisfying safety requirements.

Earth Applications
Many Earth-based technologies rely on heat transfer to keep electronics cool, from supercomputers to generators to aerial vehicles. Using high-performance heat pipes such as those in the A investigation improves the performance of these systems and offers the benefit mentioned above (e.g. reliability, low mass, low fluid toxicity, simple design, simple integration, etc.). For example, heat pipes could be used to transfer warmth generated by an unmanned airplane’s avionics systems, melting ice on the wings or to prevent fuel from freezing.

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Operational Requirements and Protocols

The requirements necessary to carry out the investigation are:
Crew Time
Installation of the Experiment Container into Microgravity Science Glovebox (MSG) (15 min); retrieval and installation of the NIKON D3S-IR Camera (TBC min); MSG Rack Activation (10 min); Experiment Activation and photo imaging during the experiment run (5 min) - the experiment activation is a ground activity; MSG Rack deactivation (10 min); uninstallation and stowage of the NIKON D3S-IR Camera (TBC min); uninstallation of the Experiment Container from MSG and pack for return (15 min); transfer of the IR images to a SSC via SD card (5 min); transfer of the experimental data to a SSC via SD card (5 min).
NIKON D3S-IR Camera (currently located in the Cupola – CUP1).
Flexible Brackets for Camera installation inside the MSG.
Station Support Computer (SSC) for images and data transfer and downlink.
Power interface with MSG Payload Rack (including cables): Power @28 VDC.
Thermal Interface with MSG Cold Plate at 15-20°C.
One Observation made of 4 intermediate runs on the 4 Heat Pipes, plus additional runs providing for each Heat Pipe higher thermal loads. Total time of the experiment run ranges from 150 to 360 minutes.
Experimental Data and IR images downlink.
EC disposal/return following the experiment execution.

In-flight testing phase is supported by crew members on-board the ISS, as well as by the ISS Payload Flight Controllers. Installation and integration of the Experiment Container inside the MSG requires a specific amount of crew time. The sequence of activities necessary to complete the investigation is documented in the following paragraphs:
Experiment Container and IR Camera Installation
The time required for completion of this activity is approximately To Be Confirmed (TBC) minutes, consisting of 15 minutes for the installation of the EC inside the MSG Glovebox (cables connections included), and TBC minutes for retrieval and installation of the NIKON D3S-IR Camera (currently located in the Cupola) inside the MSG, by means of a Bogen-Arm.
MSG Rack Activation
MSG Rack activation is accomplished in two phases: The Rack is activated by ground command, and it is necessary to enable and route the ISS power and data resources to the MSG. The completion of Rack activation is done by crew procedure.
Experiment Activation and Run
The experiment activation is provided by ground command. Experiment execution consists of two different types of tests: The first type is aimed at analyzing the performance of the Heat Pipes when a gradual increase of power is supplied (in incremental steps of a few Watts each). This is done for each of the four Heat Pipes in a parallel way; The second type of test consists of stressing the performance of each Heat Pipe by supplying a peak power and higher power steps to detect the limit conditions. For this, the power supply is cut off and the heat pipe is brought to the initial conditions.
The tests described above are implemented via the following sequence of activities: 1) Parallel runs of the heat pipes with incremental increase of power (5 minutes of thermal camera photo shooting during the last step are included) [70 minutes], 2)Parallel or sequential power decreasing steps to achieve a fixed temperature value [10 minutes], 3)Run of peak power sequence [60 minutes], and 4)Cooling down of all heat pipes [10minutes], including the stowage of the NIKON D3S-IR Camera.
The minimum time assessed for the experiment installation, activation, and run is 150 minutes. The optimal time is 360 minutes (this allows for additional investigations to be performed).
MSG Rack Deactivation
MSG Rack deactivation is accomplished in two phases. 1) Rack is deactivated by crew procedure, and 2) the completion of Rack deactivation is done by ground command. This is necessary to disable the MSG data and power.
De-installation and Stowage
This activity consists of 1)10 minutes for transferring IR images and experiment data on a Station Support Computer (SSC), and 2) 15 minutes for the uninstallation of the EC from the MSG (including labelling for disposal).

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Related Websites

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image Schematic of the Experiment Container with its internal components.
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image Timeline of the Experiment Run for a single heat pipe.
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image Crew Activities
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