Steady-state and transient performance of hot reservoir gas-controlled heat pipes
Liquid or vapor phase working fluids penetration effects on steady state and transient performance of hot reservoir gas controlled heat pipes
Fleischman, G. L.↗
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Operation and Security Considerations for Heat Pipe Cooled Microreactors
Microreactors and small modular reactors (SMRs) are anticipated to be key elements in the United States' carbon-free energy portfolio, serving as reliable power sources for remote communities, disaster relief zones, extraterrestrial deployments, and backup power needs. Microreactors employ technologies that are substantially more advanced and recent compared to conventional reactors. Furthermore, they are of a drastically smaller scale and are designed to be operated in a diverse set of locations, offering operational flexibility and mobility. In addition, the autonomous or semi-autonomous operation of microreactors with minimal or no on-site staff is anticipated. These factors give rise to specific challenges with regards to their safety and security. The present work investigates considerations related to heat pipe operation, reactor transport, and cyber/cyberphysical security to ensure the indirect and direct consequences of nefarious actors’ actions are understood and can be mitigated by design or through physical security measures. In addition, future directions are proposed for consideration by both HPMR designers and for regulators.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
A split-core heat pipe reactor concept for an out-of-core thermionic power system
Design and operation of split fueled cores with axial heat pipes for 350 kwe out-of-core thermionic power converter system
Lantz, E.↗
Fabrication of carbon-carbon heat pipes for space nuclear power applications
Significant advancements have been made in the development of lightweight, high performance, carbon-carbon heat pipes for space nuclear power applications. The subject program has progressed through the concept definition and feasibility analysis stages to the current test article component fabrication and assembly phase. This concept utilizes a carbon-carbon tube with integrally woven fins as the primary structural element and radiative surface, Nb-1Zr liners to contain a potassium working fluid, and welded end caps and fill tubes. Various tests have been performed in the development of suitable liner bonding techniques and in the assessment of material stability.
Rovang, Richard D.↗
Rewetting of monogroove heat pipe in Space Station radiators
The annual status report for the experimental work in progress regarding the rewetting of a monogroove heat pipe in a microgravity environment is presented. This report is divided into two sections. The first details improvements in the experimental apparatus, and the second reports the ground based and theoretical results.
Chan, S. H.↗
Innovative Heat Pipes Using New Working Fluids: Proof of Concept Research
Both experimental and mechanism analysis studies about the concept of the innovative heat pipe using new working fluids have been conducted. The major study activities and results are summarized summarized.
Zhang, Nengli↗
High Conductivity Carbon-Carbon Heat Pipes for Light Weight Space Power System Radiators
Based on prior successful fabrication and demonstration testing of a carbon-carbon heat pipe radiator element with integral fins this paper examines the hypothetical extension of the technology via substitution of high thermal conductivity composites which would permit increasing fin length while still maintaining high fin effectiveness. As a result the specific radiator mass could approach an ultimate asymptotic minimum value near 1.0 kg/m2, which is less than one fourth the value of present day satellite radiators. The implied mass savings would be even greater for high capacity space and planetary surface power systems, which may require radiator areas ranging from hundreds to thousands of square meters, depending on system power level.
Juhasz, Albert J.↗
Using Thermoelectric Converters for Loop Heat Pipe Operating Temperature Control
This paper describes an experimental study to investigate the effectiveness of using thermoelectric converters (TECs) to control the loop heat pipe (LHP) operating temperature. Tests were conducted on an LHP having two evaporators and two condensers. Each evaporator has its own integral compensation chamber (CC). One side of the TEC is attached to the CC, and the other side is connected to the evaporator through a copper thermal strap. A bi-polar power supply is used to provide the power for the operation of each TEC. The bipolar supply will automatic change the direction of the current to the TEC depending on whether the CC requires heating or cooling in order to maintain its temperature at the desired set point. When cooling the CC, the heat pumped by the TEC plus the power needed to operate the TEC is dissipated to the evaporator, and is ultimately transmitted to the condenser. When heating the CC, the TEC can draw heat from the evaporator to supplement the required control heater power. Test results showed that the TEC could control the LHP operating temperature within h1K of the set point temperature. The control heater power required for TEC operation was also much less than that of using electrical heaters.
Ku, Jentung↗
Capillary Pump Loop (CPL) heat pipe development status report
The capillary pump loop (CPL) was re-introduced as a potential candidate for the management of large heat loads. It is currently being evaluated for application in the thermal management of large space structures. Test efforts were conducted to establish the feasibility of the CPL heat pipe design.
Source record↗
Test program for transmitter experiment package and heat pipe system for the communications technology satellite
The test program is described for the 200 watt transmitter experiment package and the variable conductance heat pipe system which are components of the high-power transponder aboard the Communications Technology Satellite. The program includes qualification tests to demonstrate design adequacy, acceptance tests to expose latent defects in flight hardware, and development tests to integrate the components into the transponder system and to demonstrate compatibility.
Depauw, J. F.↗
Measurement of high-temperature thermal conductivity of Lucalox /Al2O3/ using a heat pipe technique.
The thermal conductivity of Lucalox, a high-purity form of aluminum oxide, has been measured over the temperature range from 870 to 1400 C. The technique employed is a novel one using a lithium-filled heat pipe in series with a gas-gap variable-heat-conductance unit as a heat source. The procedure makes it possible to measure heat flux through the sample directly. The measurements indicate that the thermal conductivity of high-purity aluminum oxide has a minimum value of about 0.05 W/cm deg C at 950 C and increases with higher temperatures to values in the range of 0.3 W/cm deg C at 1400 C.
Forman, R.↗
Heat Pipe Reactor Dynamic Response Tests: SAFE-100 Reactor Core Prototype
The SAFE-I00a test article at the NASA Marshall Space Flight Center was used to simulate a variety of potential reactor transients; the SAFEl00a is a resistively heated, stainless-steel heat-pipe (HP)-reactor core segment, coupled to a gas-flow heat exchanger (HX). For these transients the core power was controlled by a point kinetics model with reactivity feedback based on core average temperature; the neutron generation time and the temperature feedback coefficient are provided as model inputs. This type of non-nuclear test is expected to provide reasonable approximation of reactor transient behavior because reactivity feedback is very simple in a compact fast reactor (simple, negative, and relatively monotonic temperature feedback, caused mostly by thermal expansion) and calculations show there are no significant reactivity effects associated with fluid in the HP (the worth of the entire inventory of Na in the core is .<el, so fluid movement and temperature changes will cause very minor effects). In previous SAFE-100 tests, the point kinetics model was based on core thermal expansion via deflection measurements. It was found that core deflection was a strung function of how the SAFE-100 modules were fabricated and assembled (in terms of straightness, gaps, and other tolerances). To remove the added variable of how this particular core expands as compared to a different concept, it was decided to use a temperature based feedback model (based on several thermocouples placed throughout the core).
Bragg-Sitton, Shannon M.↗
Heat pipe thermal control system concept for the space station.
A program was undertaken to design and evaluate a high reliability, long life thermal control system for Space Station application. The program consisted of three sequential steps including the investigation of many thermal control elements to select the most reliable. The elements are combined into several system concepts. The most desirable approach is then selected and its characteristics are determined. The result of this project is a conceptual thermal control system design that employs heat pipes as primary components, both for heat transport and variable temperature control.
Scollon, T. R., Jr.↗
NASA Lewis Steady-State Heat Pipe Code Architecture
NASA Glenn Research Center (GRC) has developed the LERCHP code. The PC-based LERCHP code can be used to predict the steady-state performance of heat pipes, including the determination of operating temperature and operating limits which might be encountered under specified conditions. The code contains a vapor flow algorithm which incorporates vapor compressibility and axially varying heat input. For the liquid flow in the wick, Darcy s formula is employed. Thermal boundary conditions and geometric structures can be defined through an interactive input interface. A variety of fluid and material options as well as user defined options can be chosen for the working fluid, wick, and pipe materials. This report documents the current effort at GRC to update the LERCHP code for operating in a Microsoft Windows (Microsoft Corporation) environment. A detailed analysis of the model is presented. The programming architecture for the numerical calculations is explained and flowcharts of the key subroutines are given
Mi, Ye↗
Low-temperature heat pipe research program
Wick fluid flow and evaporator performance data of various fluids and materials varying in structure and thickness derived for low temperature spacecraft heat pipe design
Phillips, E. C.↗
Priming considerations of heat pipes in zero-G
Investigations into the forces which govern the geometric configuration of the liquid vapor interface in Grumman's high capacity monogroove Heat Pipe are made. Two separate methods are used to determine the time to prime and computer programs using these mathematical techniques are developed and presented. A description of the two techniques along with a discussion of the variation of the results follows. In addition, experimental procedures for tests designed to verify modeling predictions are described.
Peterson, G. P.↗
Effects of Gravity on Start-up of a Miniature Loop Heat Pipe with Multiple Evaporators and Multiple Condensers
This paper describes an experimental study on the effect of gravity on the start-up of a miniature loop heat pipe (MLHP) with two evaporators and two condensers. Each evaporator has an outer diameter of 9 mm and has its own integral compensation chamber (CC). The MLHP was placed under five configurations where the relative elevation and tilt among the loop components were varied. The four well-known initial conditions between the evaporator and CC prior to the LHP start-up were created in this experimental study through combinations of: 1) the test configuration; 2) the method of preconditioning the loop prior to start-up, and 3) the heat load distribution among the evaporators. A total of 165 start-ups were conducted under the five test configurations. All of these start-ups were successful. However, the effect of gravity on start-up transients was clearly seen under otherwise the same heat load distribution and sink temperatures. An analytical model was used to simulate the MLHP transient behaviors, and the model predictions agreed very well with the experimental results.
Ku, Jentung↗
Heat pipes in space: A NASA summary
Experiences derived from the development, integration, and flight of NASA spacecraft and sounding rockets are presented. They include the International Heat Pipe Experiment, OAO 3, and ATS-6. Typical flight data are presented to show the performance.
Ollendorf, S.↗