Rotating Bubble Membrane Radiator for space applications

Applied Thermal Engineering, 2008

Capillary heat loops (CHL) are heat transfer designs with high-effectiveness, high-performance, high-reliability, high-flexibility, and anti-gravitation features of interest to the space community. At the Canadian space agency a project has been initiated since 2002 to develop an understanding of CHL technology. The technology is targeted towards the thermal control systems of miniaturized satellites. This paper presents reviews of CHL modeling and space applications and introduces the recent development of loop heat pipe (LHP) technology in Canada in the hardware development, application, performance testing, analytical prediction and numerical modeling.

Gravitational and Space Biology Bulletin, 2015

In order to meet heat rejection requirements for future NASA exploration, scientific, and discovery missions, a study is being conducted for the feasibility of integral variable conductance planar heat pipe (VCPHP) technology. This represents a novel, low technology readiness level (TRL) heat rejection technology that, when developed, could operate efficiently and reliably across a wide range of thermal environments. The concept consists of a planar heat pipe whose evaporator acquires the excess thermal energy from the thermal control system and rejects it at its condenser whose outer surface acts as a radiating surface. The heat pipe is made from thermally conductive polymers in order to minimize its mass. It has a non-condensable gas that changes the active radiator surface depending on the heat load. A mathematical model of steady-state variable conductance heat pipe is developed. Two planar heat pipes are designed, fabricated, and tested to validate the theoretical model. The feasibility of the proposed VCPHP working in a space environment is discussed, based on the model.

AIP-CP-813, Space Technology and Applications International Forum (STAIF-2006), Albuquerque NM, 2006

A high temperature water heat pipes radiator design is developed for a space power system with a sectored gas‐cooled reactor and three Closed Brayton Cycle (CBC) engines, for avoidance of single point failures in reactor cooling and energy conversion and rejection. The CBC engines operate at turbine inlet and exit temperatures of 1144 K and 952 K. They have a net efficiency of 19.4% and each provides 30.5 kWe of net electrical power to the load. A He‐Xe gas mixture serves as the turbine working fluid and cools the reactor core, entering at 904 K and exiting at 1149 K. Each CBC loop is coupled to a reactor sector, which is neutronically and thermally coupled, but hydraulically decoupled to the other two sectors, and to a NaK‐78 secondary loop with two water heat pipes radiator panels. The segmented panels each consist of a forward fixed segment and two rear deployable segments, operating hydraulically in parallel. The deployed radiator has an effective surface area of 203 m2, and when the rear segments are folded, the stowed power system fits in the launch bay of the DELTA‐IV Heavy launch vehicle. For enhanced reliability, the water heat pipes operate below 50% of their wicking limit; the sonic limit is not a concern because of the water, high vapor pressure at the temperatures of interest (384 – 491 K). The rejected power by the radiator peaks when the ratio of the lengths of evaporator sections of the longest and shortest heat pipes is the same as that of the major and minor widths of the segments. The shortest and hottest heat pipes in the rear segments operate at 491 K and 2.24 MPa, and each rejects 154 W. The longest heat pipes operate cooler (427 K and 0.52 MPa) and because they are 69% longer, reject more power (200 W each). The longest and hottest heat pipes in the forward segments reject the largest power (320 W each) while operating at ∼ 46% of capillary limit. The vapor temperature and pressure in these heat pipes are 485 K and 1.97 MPa. By contrast, the shortest water heat pipes in the forward segments operate much cooler (427 K and 0.52 MPa), and reject a much lower power of 45 W each. The radiator with six fixed and 12 rear deployable segments rejects a total of 324 kWth, weights 994 kg and has an average specific power of 326 Wth/kg and a specific mass of 5.88 kg/m2. © 2006 American Institute of Physics .

Thermal Science and Engineering Progress, 2020

The use of Pulsating Heat Pipes (PHPs) in the space field is still an open issue because of the lack of data obtained during actual operation in relevant environment. A considerable amount of data is available in the literature on the thermal response of PHPs to a variable gravity condition and on the operation in the cryogenic field but in both cases the heat load at the condenser is rejected by convection to a constant temperature sink. On the other hand, barely any work in the PHP's literature deals with thermal radiation to a low temperature sink as only heat transfer mode. The present work attempts to fill the gap by testing a PHP radiator (16 turns, 1.1 mm inner diameter, 50% filled with FC-72 at 293K) in thermo-vacuum conditions in horizontal orientation at different heat loads and different environment (chamber) temperature. Fluid pressure measurements coupled with the frequency analysis characterised the effect of the cold source temperature on the device operational limits and efficiency. Results show that the device thermal performance in the radiative configuration is mostly affected by the lower operating temperatures needed to obtain a sensible heat rejection, rather than the heat transfer mode itself. The decrease of the environment temperature shortens the operational heat load range: the start-up occurs at higher heat input levels while the thermal crisis occurs at lower heat loads. The frequency analysis reveals that the equivalent thermal resistance is positively affected by higher values of the dominant frequency for all the cases.

Space Science Reviews, 1992

Single stage Stirring coolers providing refrigeration at around 80 K have been developed for space use and are now being produced commercially. Development work is now concentrating on multistage coolers for temperatures below 30 K. This paper describes results from a two stage cooler built at the Rutherford Appleton Laboratory and preliminary tests on a dosed cycle 4 K cooler.

International Journal of Thermal Sciences, 2015

A novel concept of a hybrid Thermosyphon/Pulsating Heat Pipe with a diameter bigger than the capillary limit is tested both on ground and in hyper/micro gravity conditions during the 61 st ESA Parabolic Flight Campaign. The device is filled with FC-72 and it is made of an aluminum tube (I.D. 3 mm) bent into a planar serpentine with five curves at the evaporator zone, while a transparent section closes the loop, allowing fluid flow visualizations in the condenser zone. Five heaters, mounted alternatively in the branches just above the curves at the evaporator zone, provide an asymmetrical heating thus promoting the fluid flow circulation in a preferential direction. The device has been tested at different positions (vertical and horizontal) and at different heat power input levels (from 10 W to 160 W). Ground tests show that effectively the device works as a thermosyphon when gravity assisted: in vertical position the device can reach an equivalent thermal resistance of 0.1 K/W with heat fluxes up to 17 W/cm 2. In horizontal position the fluid motion is absent, thus the device works as a pure thermal conductive medium. The parabolic flight tests point out a PHP working mode: during the micro-gravity period, the sudden absence of buoyancy force activates an oscillating slug/plug flow regime, typical of the PHP operation, allowing the device to work also in the horizontal position. In some cases the hyper-gravity period is able to eliminate partial dry-outs restoring the correct operation until the occurrence of the next microgravity period.

2001

The performance capability of a two-stage Stirling cycle cooler intended for space applications in the range of 10K has been demonstrated and characterised over a range of interface temperatures. To achieve the desired performance, several design improvements were made to an existing qualified cooler, originally intended for application in the 20-50K range. The modifications have extended the ability of the

2018

I want to thank my advisor James Nabity, all the Bioastronautics faculty members, and all the students of the Ann and H.J. Smead Aerospace Engineering Sciences that helped me to develop this work. Additionally I would like to honor the efforts by BioServe Space Technologies for allowing me the use of their facilities.

Applied Spectroscopy, 1988

The total performance of a droplet space radiator has been predicted by simulation of infrared emission spectra. Emission spectra for a droplet are simulated with the use of exact optical theory from the optical constant spectra of a low-molecular-weight silicone, which is a candidate for use as an emission medium of the radiator. Emissive power and total emittance are calculated from the simulated emission spectra for a droplet at different temperatures. It is found that the fourth-power temperature dependence of the emissive power of the blackbody and the temperature dependence of the emissivity inherent to the materials govern the emissive power of the droplet. The progressive decreases in temperature of a droplet and a droplet sheet in space are also simulated. A droplet with a diameter of 1 μm is predicted to cool from 500 K to 252 K in two seconds. The effects of the size of a droplet and the number density of the droplets in the sheet on the cooling rate are estimated. A smal...

Europhysics News, 2008

Aerospace Science and Technology, 2013

A new spacecraft thermal control hardware composed of two parallel channels working for heat pipe (HP) and solid-liquid phase change material (PCM), respectively, is suggested for the high heat dissipating component which works intermittently with short duty. In present study the honeycomb structure radiator embedded with the device combining HP and PCM is designed, and the detailed thermal math models are developed for numerical analysis. The comparison of computational results between with and without PCM shows that the HP-PCM device redistributes temporal peak heat around a whole orbit period through alternate melting and freezing of PCM, and, as a result, the maximum and minimum temperatures are effectively alleviated. The drawback of PCM application due to low thermal conductivity can be successfully resolved by means of parallel arrangement of the HP channel. The suggested HP-PCM device can be a kind of off-the-shelf component and it does not require any case dedicated configuration. Therefore, it can be used with less impact on the program cost and schedule different from most of the PCM applications.

Microgravity Science and Technology

For future space transportation and surface power applications, NASA Glenn Research Center (GRC) is currently investigating a small fission system (Kilopower system), which has operable range of 1 to 10kW e. The Kilopower system uses alkali metal heat pipes to transport heat from a nuclear reactor to the Stirling convertors to produce electricity and titanium water heat pipes to remove the waste heat from the convertors to the radiators. In a Small Business Innovation Research (SBIR) program, Advanced Cooling Technologies, Inc. (ACT) developed the titanium/water heat pipes for Kilopower waste heat rejection. These heat pipes are featured with bi-porous screen in the evaporator, and a screen-groove hybrid wick for the rest of the pipe, that allow the Kilopower system to survive and function under following four conditions: (1) space operation with zero gravity (2) ground testing with slight adverse gravity orientation (3) surface operation with gravity-aided orientation (4) and launch, with the against-gravity orientation and below freezing temperature. This paper presents the development of the titanium water heat pipes with radiator for Kilopower waste heat rejection, including the hardware design, heat pipe radiator assembly and thermal performance experimental validation.

41st AIAA Thermophysics Conference, 2009

AIP-CP-746, Space Technology and Applications International Forum (STAIF-2005), Albuquerque NM, 2005

Technologies for Space Reactor Power Systems are being developed to enable future NASA's missions early next decade to explore the farthest planets in the solar system. The choices of the energy conversion technology for these power systems require radiator temperatures that span a wide range, from 350 K to 800 K. Heat pipes with carbon-carbon fins and armor are the preferred choice for these radiators because of inherent redundancy and efficient spreading and rejection of waste heat into space at a relatively small mass penalty. The performance results and specific masses of radiator heat pipes with cesium, rubidium, and potassium working fluids are presented and compared in this paper. The heat pipes operate at 40% of the prevailing operation limit (a design margin of 60%), typically the sonic and/or capillary limit. The thickness of the carbon-carbon fins is 0.5 mm but the width is varied, and the evaporator and condenser sections are 0.15 and 1.35 m long, respectively. The 400-mesh wick and the heat pipe thin metal wall are titanium, and the carbon-carbon armor (~ 2 mm-thick) provides both structural strength and protection against meteoroids impacts. The cross-section area of the D-shaped radiator heat pipes is optimized for minimum mass. Because of the low vapor pressure of potassium and its very high Figure-Of-Merit (FOM), radiator potassium heat pipes are the best performers at temperatures above 800 K, where the sonic limit is no longer an issue. On the other hand, rubidium heat pipes are limited by the sonic limit below 762 K and by the capillary limit at higher temperature. The transition temperature between these two limits for the cesium heat pipes occurs at a lower temperature of 724 K, since cesium has lower FOM than rubidium. The present results show that with a design margin of 60%, the cesium heat pipes radiator is best at 680-720 K, the rubidium heat pipes radiator is best at 720-800 K, while the potassium heat pipes radiator is the best performer and lightest at higher temperatures >= 800 K.