Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “refrigerators”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Process for producing an activated carbon adsorbent with integral heat transfer apparatus

A process for producing an integral adsorbent-heat exchanger apparatus useful in ammonia refrigerant heat pump systems. In one embodiment, the process wets an activated carbon particles-solvent mixture with a binder-solvent mixture, presses the binder wetted activated carbon mixture on a metal tube surface and thereafter pyrolyzes the mixture to form a bonded activated carbon matrix adjoined to the tube surface. The integral apparatus can be easily and inexpensively produced by the process in large quantities.

Jones, Jack A.↗
NASA NTRS1981

Thallous halide materials for use in cryogenic applications

Thallous halides, either alone or in combination with other ceramic materials, are used in cryogenic applications such as heat exchange material for the regenerator section of a closed-cycle cryogenic refrigeration section, as stabilizing coatings for superconducting wires, and as dielectric insulating materials. The thallous halides possess unusually large specific heats at low temperatures, have large thermal conductivities, are nonmagnetic, and are nonconductors of electricity. They can be formed into a variety of shapes such as spheres, bars, rods, or the like and can be coated onto substrates.

Lawless, William N.↗
NASA NTRS1998

Near azeotropic mixture substitute for dichlorodifluoromethane

A refrigerant and a process of formulating thereof that consists of a mixture of a first mole fraction of CH.sub.2 FCF.sub.3 and a second mole fraction of a component selected from the group consisting of a mixture of CHClFCF.sub.3 and CH.sub.3 CClF.sub.2 ; a mixture of CHF.sub.2 CH.sub.3 and CH.sub.3 CClF.sub.2 ; and a mixture of CHClFCF.sub.3, CH.sub.3 CClF.sub.2 and CHF.sub.2 CH.sub.3.

Jones, Jack A.↗
NASA NTRS1984

Vapor degreasing system

A vapor degreasing method and apparatus wherein a second cooling coil is used to prevent escape of solvent or solvent vapor from a degreaser. Gaseous refrigerant from the second coil can be released to the freeboard space above the solvent vapor zone to provide a barrier layer.

du Fresne, Eugene R.↗
NASA NTRS2004

Heat pipe systems using new working fluids

The performance of a heat pipe system is greatly improved by the use of a dilute aqueous solution of about 0.0005 and about 0.005 moles per liter of a long chain alcohol as the working fluid. The surface tension-temperature gradient of the long-chain alcohol solutions turns positive as the temperature exceeds a certain value, for example about 40.degree. C. for n-heptanol solutions. Consequently, the Marangoni effect does not impede, but rather aids in bubble departure from the heating surface. Thus, the bubble size at departure is substantially reduced at higher frequencies and, therefore, increases the boiling limit of heat pipes. This feature is useful in microgravity conditions. In addition to microgravity applications, the heat pipe system may be used for commercial, residential and vehicular air conditioning systems, micro heat pipes for electronic devices, refrigeration and heat exchangers, and chemistry and cryogenics.

Chao, David F.↗
NASA NTRS1989

Low temperature storage container for transporting perishables to space station

Two storage containers are disclosed within which food or biological samples may be stored for transfer in a module by the space shuttle to a space station while maintaining the food or samples at very low temperatures. The container is formed in two parts, each part having an inner shell and an outer shell disposed about the inner shell. The space between the shells is filled with a continuous wrap multi-layer insulation and a getter material. The two parts of the container have interlocking members and when connected together are sealed for preventing leakage from the space between the shells. After the two parts are filled with frozen food or samples they are connected together and a vacuum is drawn in the space between the shells and the container is stored in the module. For the extremely low temperature requirements of biological samples, an internal liner having a phase change material charged by a refrigerant coil is disposed in the space between the shells, and the container is formed from glass fiber material including honeycomb structural elements. All surfaces of the glass fiber which face the vacuum space are lined with a metal foil.

Owen, James W.↗
NASA NTRS2009

Utilizing Ocean Thermal Energy in a Submarine Robot

A proposed system would exploit the ocean thermal gradient for recharging the batteries in a battery-powered unmanned underwater vehicle [UUV (essentially, a small exploratory submarine robot)] of a type that has been deployed in large numbers in research pertaining to global warming. A UUV of this type travels between the ocean surface and depths, measuring temperature and salinity. The proposed system is related to, but not the same as, previously reported ocean thermal energy conversion (OTEC) systems that exploit the ocean thermal gradient but consist of stationary apparatuses that span large depth ranges. The system would include a turbine driven by working fluid subjected to a thermodynamic cycle. CO2 has been provisionally chosen as the working fluid because it has the requisite physical properties for use in the range of temperatures expected to be encountered in operation, is not flammable, and is much less toxic than are many other commercially available refrigerant fluids. The system would be housed in a pressurized central compartment in a UUV equipped with a double hull (see figure). The thermodynamic cycle would begin when the UUV was at maximum depth, where some of the CO2 would condense and be stored, at relatively low temperature and pressure, in the annular volume between the inner and outer hulls. The cycle would resume once the UUV had ascended to near the surface, where the ocean temperature is typically greater than or equals 20 C. At this temperature, the CO2 previously stored at depth in the annular volume between the inner and outer hulls would be pressurized to approx. equals 57 bar (5.7 MPa). The pressurized gaseous CO2 would flow through a check valve into a bladder inside the pressurized compartment, thereby storing energy of the relatively warm, pressurized CO2 for subsequent use after the next descent to maximum depth.

Jones, Jack↗
NASA NTRS2009

Thermostatic Valves Containing Silicone-Oil Actuators

Flow-splitting and flow-mixing thermally actuated spool valves have been developed for controlling flows of a heat-transfer fluid in a temperature-regulation system aboard the Mars Science Laboratory (MSL) rover. Valves like these could also be useful in terrestrial temperature-regulation systems, including automobile air-conditioning systems and general refrigeration systems. These valves are required to provide smoother actuation over a wider temperature range than the flow-splitting, thermally actuated spool valves used in the Mars Explorer Rover (MER). Also, whereas the MER valves are unstable (tending to oscillate) in certain transition temperature ranges, these valves are required not to oscillate. The MER valves are actuated by thermal expansion of a wax against spring-loaded piston rods (as in common automotive thermostats). The MSL valves contain similar actuators that utilize thermal expansion of a silicone oil, because silicone-oil actuators were found to afford greater and more nearly linear displacements, needed for smoother actuation, over the required wider temperature range. The MSL valves also feature improved spool designs that reflect greater understanding of fluid dynamics, consideration of pressure drops in valves, and a requirement for balancing of pressures in different flow branches.

Bhandari, Pradeep↗
NASA NTRS2009

Precision Cleaning of Oxygen Systems and Components

Currently, NASA uses Dichloropentafluoropropane (HCFC-225), a Class II ozone depleting substance (ODs), to clean contaminated oxygen systems. Starting in 20 15, the Montreal Protocols and Clean Air Act prohibit the production and importation of all hydrochlorofluorocarbons (HCFC), except for limited use in refrigeration applications. Thus, a new non-ozone depleting solvent needs to be developed for use in cleaning. Optimally, such a solvent should also be environmentally benign or green to avoid needing to replace the new solvent with yet another solvent in the future due to other environmental concerns. Work for the first year consisted of two parts. The first part was developing a method of testing the cleaning efficiency of potential solvents. Stainless steel coupons were contaminated with a known weight of various contaminants and contaminant combinations and then immersed in solvent for ten minutes. The coupons were then removed and dried in an oven until all solvent had evaporated. Once dry, the coupons were weighed and the mass of the non-volatile residue (NVR) left on the coupon was determined. The cleaning efficiency of the solvents is reported as percent cleaning, with 100% cleaning being zero NVR left on the test coupon. The second half of the first goal was to use the develop method to perform baseline testing on current solvents. The second part of the work was to begin exploring alternative cleaning solvents. A variety of hydrofluorocarbons (HFCs) were tested. Preliminary testing was also performed with ionic liquids and aqueous surfactant solutions. Once potential solvents were identified, an analysis of the performance and environmental characteristics of each was to be conducted. Four contaminants were specified for use in testing. These are Mil-Spec-H-5606 (5606), a hydraulic fluid, Mil-H-83282B (83282), another hydraulic fluid, diethylhexyl sebacate (Sebacate), and WD-40. The structures of these contaminants are all similar, with long aliphatic hydrocarbon chains of lengths between fifteen and fifty. Contaminants were tested both individually and in combination. All combinations were done with equal weights of the constituent contaminants.

McLaughlin, Russell↗
NASA NTRS2010

Wider-Opening Dewar Flasks for Cryogenic Storage

Dewar flasks have been proposed as containers for relatively long-term (25 days) storage of perishable scientific samples or other perishable objects at a temperature of 175 C. The refrigeration would be maintained through slow boiling of liquid nitrogen (LN2). For the purposes of the application for which these containers were proposed, (1) the neck openings of commercial off-the-shelf (COTS) Dewar flasks are too small for most NASA samples; (2) the round shapes of the COTS containers give rise to unacceptably low efficiency of packing in rectangular cargo compartments; and (3) the COTS containers include metal structures that are too thermally conductive, such that they cannot, without exceeding size and weight limits, hold enough LN2 for the required long-term-storage. In comparison with COTS Dewar flasks, the proposed containers would be rectangular, yet would satisfy the long-term storage requirement without exceeding size and weight limits; would have larger neck openings; and would have greater sample volumes, leading to a packing efficiency of about double the sample volume as a fraction of total volume. The proposed containers would be made partly of aerospace- type composite materials and would include vacuum walls, multilayer insulation, and aerogel insulation.

Ruemmele, Warren P.↗
NASA NTRS2010

Apparatus for Cold, Pressurized Biogeochemical Experiments

A laboratory apparatus has been devised as a means of studying plausible biogeochemical reactions under high-pressure, low-temperature aqueous, anaerobic conditions like those conjectured to prevail in a liquid water ocean on Europa (the fourth largest moon of the planet Jupiter). The experiments to be performed by use of this apparatus are intended to enhance understanding of how life (if any) could originate and evolve in the Europa ocean environment. Inasmuch as terrestrial barophilic, psychrophilic organisms that thrive under anaerobic conditions are used in the experiments, the experiments may also contribute to terrestrial biogeochemistry. The apparatus (see figure) includes a bolt-closure reaction vessel secured inside a refrigerator that maintains a temperature of 4 C. Pressurized water is supplied to the interior of the vessel by a hydrostatic pump, which is attached to the vessel via high-pressure fittings. The terrestrial organisms used in the experiments thus far have been several facultative barophilic, psychrophilic stains of Shewanella bacteria. In the experiments, these organisms have been tested for reduction of ferric ion by growing them in the presence of a ferric food source under optimized terrestrial conditions. The short-term goal of these experiments has been to select Shewanella strains that exhibit iron-reduction capability and test their ability to facilitate biogeochemical reduction of iron under temperature and pressure conditions imitating those in Europa s ocean. It is anticipated, that, once growth under Europa-like conditions has been achieved, the selected Shewanella strains will be used to facilitate biogeochemical reactions of sulfate and carbonate with hydrogen gas. Any disequilibrium of the products with the environment would be interpreted as signifying biogenic activity and the possibility of life in Europa s ocean.

Amashukeli, Xenia↗
NASA NTRS2006

Computing Isentropic Flow Properties of Air/R-134a Mixtures

MACHRK is a computer program that calculates isentropic flow properties of mixtures of air and refrigerant R-134a (tetrafluoroethane), which are used in transonic aerodynamic testing in a wind tunnel at Langley Research Center. Given the total temperature, total pressure, static pressure, and mole fraction of R-134a in a mixture, MACHRK calculates the Mach number and the following associated flow properties: dynamic pressure, velocity, density, static temperature, speed of sound, viscosity, ratio of specific heats, Reynolds number, and Prandtl number. Real-gas effects are taken into account by treating the gases comprising the mixture as both thermally and calorically imperfect. The Redlich-Kwong equation of state for mixtures and the constant-pressure ideal heat-capacity equation for the mixture are used in combination with the departure- function approach of thermodynamics to obtain the equations for computing the flow properties. In addition to the aforementioned calculations for air/R-134a mixtures, a research version of MACHRK can perform the corresponding calculations for mixtures of air and R-12 (dichlorodifluoromethane) and for air/SF6 mixtures. [R-12 was replaced by R-134a because of environmental concerns. SF6 has been considered for use in increasing the Reynolds-number range.]

Kvaternik, Ray↗
NASA NTRS2006

Vapor-Compression Heat Pumps for Operation Aboard Spacecraft

Vapor-compression heat pumps (including both refrigerators and heat pumps) of a proposed type would be capable of operating in microgravity and would be safe to use in enclosed environments like those of spacecraft. The designs of these pumps would incorporate modifications of, and additions to, vapor-compression cycles of heat pumps now used in normal Earth gravitation, in order to ensure efficiency and reliability during all phases of operation, including startup, shutdown, nominal continuous operation, and peak operation. Features of such a design might include any or all of the following: (1) Configuring the compressor, condenser, evaporator, valves, capillary tubes (if any), and controls to function in microgravitation; (2) Selection of a working fluid that satisfies thermodynamic requirements and is safe to use in a closed crew compartment; (3) Incorporation of a solenoid valve and/or a check valve to prevent influx of liquid to the compressor upon startup (such influx could damage the compressor); (4) Use of a diode heat pipe between the cold volume and the evaporator to limit the influx of liquid to the compressor upon startup; and (5) Use of a heated block to vaporize any liquid that arrives at the compressor inlet.

Ruemmele, Warren↗
NASA NTRS2010

Cryogenic Moisture Apparatus

The Cryogenic Moisture Apparatus (CMA) is designed for quantifying the amount of moisture from the surrounding air that is taken up by cryogenic-tank-insulating material specimens while under typical conditions of use. More specifically, the CMA holds one face of the specimen at a desired low temperature (e.g., the typical liquid-nitrogen temperature of 77 K) while the opposite face remains exposed to humid air at ambient or near-ambient temperature. The specimen is weighed before and after exposure in the CMA. The difference between the "after" and "before" weights is determined to be the weight of moisture absorbed by the specimen. Notwithstanding the term "cryogenic," the CMA is not limited to cryogenic applications: the low test temperature can be any temperature below ambient, and the specimen can be made of any material affected by moisture in air. The CMA is especially well suited for testing a variety of foam insulating materials, including those on the space-shuttle external cryogenic tanks, on other cryogenic vessels, and in refrigerators used for transporting foods, medicines, and other perishables. Testing is important because absorbed moisture not only adds weight but also, in combination with thermal cycling, can contribute to damage that degrades insulating performance. Materials are changed internally when subjected to large sub-ambient temperature gradients.

Fesmire, James↗
NASA NTRS2010

High efficiency thermoelectric power generation using Zintl-type materials

The invention disclosed herein relates to thermoelectrically-active p-type Zintl phase materials as well as devices utilizing such compounds. Such thermoelectric materials and devices may be used to convert thermal energy into electrical energy, or use electrical energy to produce heat or refrigeration. Embodiments of the invention relate to p-type thermoelectric materials related to the compound Yb.sub.14MnSb.sub.11.

Snyder, G. Jeffrey↗
NASA NTRS2010

Reduction of Sodium in the NASA Space Food System

Excessive sodium content of the average American diet is an issue that is gaining more and more attention due to the implications for chronic disease and thus health care costs. The typical astronaut or cosmonaut dining on the International Space Station (ISS) is consuming even more sodium per day than the average American due to the lack of refrigeration for food and the limited amount of fresh food in the diet. NASA has known for many years that the high sodium in the on orbit diet is an exacerbating factor for the bone loss that occurs in all crew members in microgravity. However, bone loss is reversed upon return to earth normal gravity. After ten years of having US crewmembers on ISS, additional medical issues have emerged in some long duration ISS crewmembers that are not necessarily being reversed upon return to earth. While it is not necessarily thought that the high sodium content of the diet is the cause of these issues, it is thought that reducing sodium intake could potentially help alleviate some of the on orbit symptoms. Thus, there is an urgent focus on sodium reduction in space food. This paper will discuss the strategies and progress of an on-going project at NASA to reformulate the US space food system to reduce the sodium content.

Kloeris, Vickie L.↗
NASA NTRS2011

Project H - A Complete Spaceport Hydrogen Solution

This slide presentation reviews Project H, and its importance in the development of Kennedy Space Center (KSC) as a Spaceport capable of multiple launches. It is known that current KSC cryogenic technology results in only approximately 55 % of purchased hydrogen being used. The rest is lost at various points in the process: transfer from transporting vehicle to tank, storage tank boil off, and from the tank to the intended propulsion tanks. Project H's goals would be to have local hydrogen production and liquifaction capability, and to increase the efficiency of hydrogen operations to greater than 80 %. The project envisions two phases: Phase 1 will build a smaller scale demonstration system, and phase 2 will build a full scale spaceport system. This initial project has proposed ideas for local hydrogen production, gaseous distribution, integrated refrigeration and storage, and high efficiency transfer lines that merit further investigation.

Notardonato, William↗
NASA NTRS2011

Comparison of Traditional and Innovative Techniques to Solve Technical Challenges

This slide presentation reviews the use of traditional and innovative techniques to solve technical challenges in food storage technology. The planning for a mission to Mars is underway, and the food storage technology improvements requires that improvements be made. This new technology is required, because current food storage technology is inadequate,refrigerators or freezers are not available for food preservation, and that a shelf life of 5 years is expected. A 10 year effort to improve food packaging technology has not enhanced significantly food packaging capabilities. Two innovation techniques were attempted InnoCentive and Yet2.com and have provided good results, and are still under due diligence for solver verification.

Perchonok, Michele↗