Phase Change Heat Exchanger Project (Phase Change HX) - 12.06.17

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

ISS Science for Everyone

Science Objectives for Everyone
Maintaining safe temperatures is difficult in space, where there is no atmosphere to provide warmth in the shade or protection from the sun’s heat. Phase-change material heat exchangers can help by freezing or thawing a material to maintain critical temperatures inside a spacecraft, protecting crew members and equipment. Phase Change Heat Exchanger Project (Phase Change HX) tests a new type of heat exchanger that could help offset heat on future spacecraft, enabling future missions to better regulate temperatures. The test bed brings a new capability to the International Space Station (ISS) where test articles, requiring sub-zero fluid temperatures, can be tested on ISS. The Phase Change HX Payload includes a plug and play design allowing common interfaces for future payloads that require fluid temperature between -10°C to 30°C with flow rates between 50-300 lb/hr.
Science Results for Everyone
Information Pending

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

OpNom: Phase Change HX

Principal Investigator(s)
Rubik Sheth, M.S., NASA Johnson Space Center, Houston, TX, United States

Thomas Ahlstrom, NASA Johnson Space Center, Houston, TX, United States

Jacobs Engineering, Houston, TX, United States
NASA Johnson Space Center, Crew and Thermal Systems Division, Houston, TX, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Technology Demonstration Office (TDO)

Research Benefits
Scientific Discovery, Space Exploration, Earth Benefits

ISS Expedition Duration
March 2016 - September 2017

Expeditions Assigned

Previous Missions
Information Pending

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Experiment Description

Research Overview

The Phase Change Heat Exchanger Project (Phase Change HX) Experiment objectives include:
  • Creating a unique test platform using the EXPRESS Rack on the ISS for testing phase change material heat exchangers (PCM HX).
  • PCM HXs store energy by thawing a phase change material (i.e. wax or water) via hot coolant.
  • The vehicle’s radiators are capable of cooling the coolant, then refreezes the PCM for later use.
  • Providing the ability to run numerous thaw/freeze cycles for the PCM HX while logging data from numerous temperature and pressure sensors.
  • Sending the collected data to the ground team for processing and assessing how the PCM HX is performing in a micro-gravity environment.
  • Removing the currently tested PCM HX within the experiment and installing a new PCM HX prototype with a different phase change material (i.e. water vs wax). This change-out will be capable of being performed by the on-orbit crew.
The Phase Change HX Experiment benefits include:
  • Advancing the technology readiness level of phase change heat exchangers for use on future exploration missions.
  • Assessing the performance of phase change heat exchangers in a micro-gravity environment.
  • The ability to test numerous phase change heat exchangers capable of being installed by the on-orbit crew.
  • Providing a low temperature loop (down to -10°C) that could be used in the future for other experiments in need of a lower temperatures than the ISS can currently provide.
Phase Change HX Design Overview:
  • Entire experiment is contained within an EXPRESS Rack double locker.
  • Utilizes the Moderate Temperature Loop (MTL), Low Temperature Loop (LTL), two EXPRESS Rack power connections, and one EXPRESS Rack data connection.
  • Includes a contained Propylene Glycol Water (PGW) loop and a Thermal Electric Cooler (TEC) HX which provides the -10°C fluid used to freeze the PCM Heat Sink.
  • The TEC HX includes strip heaters which provide the maximum 30°C fluid used to melt the PCM heat sink.
  • Includes an avionics box which is cooled by the MTL and provides all data monitoring/logging and the software interface required to run the experiment from the ground workstation.


The primary objective of the Phase Change Heat Exchanger Project (Phase Change HX) is to create a unique test platform utilizing the EXPRESS Rack on the ISS to advance the technology readiness level of phase change heat exchangers for infusion into future exploration vehicles. Phase change material heat exchangers are a useful technology that helps certain space missions in regulating the thermal conditions on their particular spacecraft. They serve as a supplemental heat rejection device during time-varying heat loads and/or transient environments. It does so by storing waste energy by melting a phase change material during peak loads. It can then reject this energy through a radiator when conditions allow, causing the phase change material to freeze.
Wax phase change material heat exchangers were used on the Apollo lunar rover and Skylab with inconsistent results. Water based phase change material heat exchangers offer considerable mass savings due to its superior energy storage over baseline wax heat exchanger, but it is unknown how they function in a microgravity environment. Water based phase change material heat exchangers offer additional challenges due to water’s ability to expand during freezing. Both wax and water phase change material heat exchangers need to be tested in a microgravity environment to better understand their performance in space.
The Phase Change HX Payload fits into an Expedite the Processing of Experiments to the Space Station (EXPRESS) Rack double locker. It is used to test interchangeable phase change material heat exchangers in a microgravity environment, thereby providing stakeholders like Orion with flight-proven phase change material heat exchanger options. The components within the double locker include a pump, instrumentation, valves, heater, and cold plates, and a thermoelectric heat exchanger. These components are used to condition coolant to allow freezing and thawing of phase change material heat exchangers.

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Space Applications
Wax-based phase-change heat exchangers have been used in space before, including on the Apollo lunar rover and the former Skylab space station, but with inconsistent results. A water-based phase-change heat exchanger has significantly better energy storage than wax, but it has not yet been tested in space. This investigation tests these heat exchangers in a microgravity environment, providing data needed to use phase-change heat exchangers on future space missions.

Earth Applications
Phase-change heat exchangers are a low-energy means to control temperatures in chemical plants, power plants and other settings. By using materials that change phase from liquid to vapor depending on the temperature, facilities like power plants and factories can more easily move heat into areas that must be warmed by removing heat from areas that must be cooled. While this investigation is geared to space-based use, results improve basic research on phase-change heat exchangers.

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Operational Requirements and Protocols

The Phase Change HX Experiment does not require any crew subjects and runs autonomously once installed into the EXPRESS Rack.  The Phase Change HX will utilize the TReK for monitoring and commanding the experiment.  No requirement for the number of cycles or spacing of experiments exists, but the experiment will run roughly one month of thaw/freeze cycles followed by one month of standby while data is being processed on the ground.

On-orbit procedures are only required for the initial installation of the experiment into the EXPRESS Rack and any future removal and reassembles (R&Rs) to install PCM HX concepts flown. For Initial Installation, crew installs the double locker into the Express Rack and makes 4 bolt connections to secure the locker into the rack. Tightening these bolts with a torque wrench is required. The crew connect 4 flex hoses (2 for the MTL supply and return, and 2 for the LTL supply and return). The crew connects 2 power cables and 1 data cable between the EXPRESS rack and the experiment front panel. The crew then activate the experiment via a circuit breaker on the front panel-an LED light on the front panel indicates "good health."
For R&R of PCM HX Top Drawer, the crew removes power form the experiment via the circuit breaker on the front panel. The crew removes 1 data/power cable and 2 flex hose connections from the top drawer. The crew loosens 2 captive bolts on the top drawer to allow it to slide out. The crew removes the top drawer with the wax PCM and installs the future PCH HX concept drawer. The crew installs the new top drawer and tightens 2 captive bolts. These bolts need to be torqued with a torque wrench. The crew re-installs the 1 power/data connector and 2 flex hose connections that were previously removed. The crew activates the payload via the circuit breaker on the front panel.

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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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Phase Change Heat Exchanger Project (Phase Change HX)

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