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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.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Evidence of Nematicity in K 0.8 Fe 1.7 Se 2

We proposed that the superconducting state of K 0.8 Fe 1.7 Se 2 is phase separated from a non-superconducting magnetic state. These results from a recent neutron diffraction study on a single crystal of K 0.8 Fe 1.7 Se 2 provide evidence for a continuous transition between the I 4 /m m m high temperature phase in which the Fe vacancies are randomly distributed and the I4/m vacancy ordered phase in the temperature range between T (C) and T (S). Upon cooling, the I 4 /m phase becomes more populated, increasing the √5 X√5 X 1 superlattice structure, resulting in an enhancement of the (101) superlattice peak. Moreover, the same temperature dependence is observed for the magnetic peak as well. Moreover, due to the Fe site splitting with the transition, its z-coordinate fluctuates, and so must the d xz and d y z orbitals. Finally, the orbital fluctuations couple to the magnetic ordering as seen here and may lead to a realization of nematic order in this system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Challenges and Opportunities of Gas Engine Driven Heat Pumps: Two Case Studies

Gas engine driven heat pumps (GHP) currently hold a small market share. This share is considerably smaller than what the full potential of GHP technology can realize. Of the main benefits of the GHP technology is their better primary energy utilization mainly due to the ability to recover the engine heat. However, development and market penetration of GHP technology have been challenged by various market and technical barriers. The main barriers are the high initial cost, low awareness of the technology, and poor perception. On the other hand, several opportunities arise that the GHP technology can take advantage of to increase its market share. The most direct opportunity is the abundance of cheap natural gas. This translates directly into monetary savings and higher ROI. GHPs offer the advantage of reducing the peak demand by 80% compared to electric counterpart. From the point of view of utilities, this eliminates the need for lower-efficiency peaking power plants and over-expansion only to cover maximum peak times. From the point of view of renewable customers, GHPs eliminate the need to buy power from the grid at a high price. This is especially important in hot climates with high cooling loads. When built and operated as distributed generation, GHPs can improve the reliability of power delivery to consumers. The paper discusses the challenges and opportunities as seen during the development and commercialization of two different GHP products; a 10-ton packaged unit and 5-ton split unit.

Abu-Heiba, Ahmad↗
NASA NTRS2001

Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Skukuza and Mongu Sites

The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF (bidirectional reflection function) measurements were obtained over different natural surfaces and ecosystems in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS (Earth Observing System) satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 S, 31.5 E) and Mongu tower, Zambia (15.4 S, 23.3 E). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 microns), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 microns). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of approximately 20 degrees and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and with a 1 degree IFOV, the pixel resolution is about 10 m at nadir and about 270 m at an 80 degree viewing angle from the CAR.

Gatebe, C. K.↗
NASA NTRS2001

Airborne spectral Measurements of Surface-Atmosphere Anisotropy for Several Surfaces and Ecosystem over Southern Africa

The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF measurements were obtained over different natural surfaces and ecosystem in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 deg S, 31.5 deg E) and Mongu tower, Zambia (15.4 deg S, 23.3 deg E). Additional sites are also considered and include, Maun tower, Botswana (20.0 deg S, 23.5 deg E), Sowa Pan, Botswana (20.6 deg S, 26.2 deg E) and Etosha Pan, Namibia (19.0 deg S, 16.0 deg E). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 micrometers), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 micrometers). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of approximately 20 degrees and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and with a 1 deg IFOV, the pixel resolution is about 10 m at nadir and about 270 m at an 80 deg viewing angle from the CAR.

Gatebe, Charles K.↗
NASA NTRS2002

Airborne Spectral Measurements of Ocean Anisotropy during CLAMS

The Cloud Absorption Radiometer (CAR) aboard the University of Washington Convair CV-580 research aircraft obtained bidirectional reflectance-distribution function (BRDF) of Atlantic Ocean and Dismal Swamp between July 10 and August 2, 2001. The BRDF measurements (15 in total, 8 uncontaminated by clouds) obtained under a variety of sun angles and wind conditions, will be used to characterize ocean anisotropy in support of Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRDF models of the ocean. In this paper we present results of BRDF of the Ocean under different sun angles and wind conditions. The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 micron), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 micron). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and with a 1 degree IFOV, the pixel resolution is about 10 m at nadir and about 270 m at an 80 deg. viewing angle from the CAR.

Gatebe, C. K.↗
DOE OSTI2017

CYCLE MODELING AND OPTIMIZATION OF AN INTEGRALLY GEARED sCO2 COMPANDER

This paper presents the selection of a system configuration and off-design control method for an integrally geared compander based on cycle modeling and optimization. The goal of the cycle modeling was to determine a cycle configuration that would reach an efficiency of 50% at design conditions and to optimize off-design control to maintain high efficiencies. The compander is being developed for use in a concentrated solar power supercritical carbon dioxide power plant with expected turbine inlet temperatures of 705°C and utilizing dry cooling leading to compressor inlet temperature varying between 35°C and 55°C. The compander is unique as it consists of eight turbomachinery stages on four pinions all being driven by a single bull gear. The separate stages offer the opportunity to consider a variety of flow splits and cycle configurations including intercooling and multiple stages of reheat. Cycle modeling was conducted in two stages: on-design and off-design. On-design modeling was simulated with all components operating at their design point. This was used to compare the performance of different cycle configurations and design temperatures. Off-design modeling was then performed to investigate the temperature dependence of the cycle efficiency and power output and to develop a control strategy. Strategies considered and discussed include: turbine bypass, compressor recycle, inlet guide vanes, and inventory control. To determine the best operating conditions for each configuration and control strategy, a genetic algorithm was implemented to optimize the cycle performance across the range of operating temperatures being considered. The final selection of cycle configuration, design temperature and control strategy is also presented.

bennett, jeffrey↗
DOE OSTI2016

The Alpenglow Instruments All Phase Water Probe: SBIR Phase I Final Report

Current approaches for measuring water vapor, ice water content, and liquid water content in the atmosphere have a variety of limitations. This is particularly true for ice water content measurements, which are needed in a variety of contexts including understanding the impact of clouds on global climate. The Alpenglow All-Phase Water Probe, which was motivated by limitations of current approaches to measuring water vapor, liquid water, and ice water content in the atmosphere, uses Raman scattering to derive these quantities. The use of Raman scattering signals for retrieval of water vapor mixing ratio, liquid and ice water content has been used in remote sensing applications. This project explored the use of the same approach in an in situ probe to measure all three phases of water in the atmosphere. The prototype device developed in this Phase 1 DOE SBIR proposal was used to demonstrate proof of concept for using Raman scattering to detect signals from water vapor, liquid water, and ice water. The prototype instrument consisted of the transmitting laser (355 nm, 7ns pulse), collector optics and receiver body, and data system. The receiver section body split the return signal into four channels, one for nitrogen plus channels dominated by water vapor, liquid water, and ice. Tests were conducted over a range of conditions ranging from ambient conditions in the lab (low water vapor mixing ratio, no liquid or ice water content), through a cool but saturated plume produced by an off-the-shelf humidifier (moderate water vapor mixing ratio plus some liquid water content), and hot, saturated stream containing extremely high water vapor mixing ratios with liquid water. Data from these tests, which was recorded using a Licel photon-counting data system, demonstrated the sensitivity of the system to varying water vapor mixing ratios ranging from ~5 g m -3 to > 20 g m -3 . Signals in the water vapor and ice channels were observed during the humidifier and hot vapor tests, as expected given the overlap between the ice and water vapor Raman spectra, with the relative contributions to each channel varying as expected with temperature.

58 GEOSCIENCES↗
DOE OSTI2015

Temperature-dependent ordering phenomena in single crystals of germanium antimony tellurides

The temperature-dependent behavior of quenched single-crystalline (GeTe){sub n}Sb{sub 2}Te{sub 3} (n~2.8, n~5 and n~11) was investigated by semiquantitative modeling of diffuse X-ray scattering. The structure at room temperature exhibits trigonal twin domains, each comprising a stacking-disordered sequence of distorted rocksalt-type slabs with variable thicknesses. Ge and Sb share the cation position and vacancies are partially ordered in defect layers (van der Waals gaps) between the slabs. The average structure determined with resonant diffraction data corresponds to a rocksalt-type structure whose cation position is split along the stacking direction. Upon heating, cation ordering leads to a metastable superstructure of the rocksalt type at ~400 °C, which transforms to a rocksalt-type high-temperature phase with randomly distributed cations and vacancies at ~500 °C; this structure was also refined using resonant diffraction. Cooling at high or intermediate rates does not yield the long-range ordered phase, but directly leads to the twinned disordered phase. - Graphical abstract: Development of the diffraction patterns of (GeTe){sub ~11}Sb{sub 2}Te{sub 3} upon heating; the insets symbolically sketch the real structure at the corresponding temperatures. - Highlights: • The structure of disordered (GeTe){sub n}Sb{sub 2}Te{sub 3} is described as a function of temperature. • Structural changes are tracked by modeling diffuse X-ray scattering. • Quenched crystals exhibit distorted NaCl-type slabs with different thicknesses. • Vacancy ordering upon heating leads to a metastable superstructure of the NaCl type. • Further heating leads to an undistorted disordered NaCl-type high-temperature phase.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Photocell heat engine solar power systems

A combined photocell heat engine concept is proposed for high efficiency solar energy conversion in space. In this concept the short wavelength portion of the solar spectrum is split by a dichroic filter and sent to a bank of photocells. The long wave-length remainder of the spectrum is used by the heat engine. This technique allows the photocells to operate with the minimum amount of waste heat, increasing their efficiency and reducing the amount of cooling required. The heat engine operates by direct absorption in a working fluid containing broadband absorber molecules or particulates. A window in the heat engine admits the long wave-lengths from the solar spectrum. The window may also reflect a portion of the internal gaseous reradiation spectrum (e.g., a heat mirror) to help reduce radiation losses. Flow-induced thermal gradients may also reduce reradiation losses in the case of optically thick working fluids. The efficiencies computed for the photocell heat engine solar energy converter can be as high as 42 percent.

Taussig, R. T.↗
NASA NTRS1992

Application of computational fluid dynamics to the design of the film cooled STME subscale nozzle for the National Launch System

The status of computational fluid dynamics (CFD) calculations for the Space Transportation Main Engine (STME) film/dump cooled nozzle design is presented, with an emphasis on the timely impact of CFD on the design of the sub-scale nozzle coolant system. The following aspects of the sub-scale coolant delivery system were analyzed with CFD: 1) a design trade study of a mechanical flow splitting device for uniform distribution of the subsonic cavity flow, 2) a design trade study of the subsonic cavity lip to achieve film integrity, and 3) an analysis of the primary flow interaction with the core/secondary coolant streams. All design calculations were performed with the Generalized Aerodynamic Simulation Program (GASP), a 3-D, multi-block, generalized Navier-Stokes code capable of solving with frozen, finite-rate or equilibrium chemical kinetics. The initial design of the subsonic cavity flow used square posts to distribute the sonic orifice jets into a uniform flow. Calculations for this design indicated that an unacceptable mal-distribution of film occurred. Design modifications involving curved and slotted posts were computed in an effort to uniformly distribute the secondary coolant flow. Analysis of these configurations showed that although the flowfield improved in uniformity, it was still unacceptable, especially at higher feed pressures. Results from these studies were then incorporated into a design that resulted in the insertion of a porous metal ring into the subsonic cavity. Subsequent water flow model studies showed that this concept was successful in uniformly distributing flow exiting the cavity. In addition to the design of the subsonic cavity, CFD was also used to analyze the secondary coolant lip and the primary flow interaction with the core/secondary coolant streams. A series of calculations were first performed to modify the subsonic cavity lip contour. The flow over the modified lip was then computed simultaneously with the primary injectors to determine the impact of the subsonic coolant stream on the primary slot jets. Pressure, temperature, velocity, and coolant mass fraction contours are presented for these configurations. Information is given in viewgraph form.

Garrett, Joseph L.↗
DOE OSTI2013

Development of Technologies and Capabilities for Coal Energy Resources

This is the final report for the Aerojet Rocketdyne (AR) Advanced Gasification Systems Development (AGSD) project that was initiated on October 1, 2004. The project’s primary objective is to demonstrate technologies that improve the availability and efficiency of gasification-based power plants and to reduce plant capital and operational costs. The objective will be accomplished by (1) development and testing of cooled refractory liners, (2) feed system development and demonstration, (3) pilot plant definition and planning, (4) transport gasifier feed analysis, (5) coal-biomass mixture feed analysis, and (6) coal-biomass mixture pilot scale tests. Task 1, development and testing of cooled refractory liners, was conducted at CANMET Energy Technology Centre in Ottawa, Canada. The test objectives were to screen high conductivity CMC materials with alternate manufacturing methods and a variety of surface treatments for cooled metal tubes in a slagging gasifier environment. During the CMC testing, it was found that a constantly cooled CMC will survive in good conditions and that high porosity CMC resulted in high material erosion and corrosion. During cooled tube testing, it was found that hard metal spray coat and bare Haynes 188 performed the best. Task 2, feed system development and demonstration, was conducted at at the Energy and Environmental Research Center (EERC) at the University of North Dakota (UND). For tasks 2.1-2.6, the test objective was to demonstrate 400-tons/day coal feed system operation (to 1,000 psia gasifier pressures) in ultra-dense phase flow without plugging and to achieve multi-element injector flow-split non-uniformities below 2 %RSD. Testing was successfully completed with no feed system plugging of the feed system. The majority of the other Task 2 activities were associated with the Dry Solids Pump design (Task 2.8 and 2.11), development (Task 2.10), fabrication (Task 2.12), amd testing (Task 2.13-2.15). A variety of tests were performed that verified the capability of the Dry Solids Pump to consolidate various pulverized feedstocks to a state capable of sealing and sustaining downstream outlet pressures during mechanical operation of the pump as well as during periods when the pump was turned off. However, the final operating goals were not achieved. Task 3, pilot plant definition and planning, was to define requirements for an advanced commercial gasifier with a cooled liner and to establish a preferred commercial gasifier system configuration to serve as the reference point for an advanced gasifier pilot plant concept definition. A pilot plant concept was successfully defined that is scalable and traceable to the commercial gasifier configuration. The schedule and cost for design, installation, and long-duration test operation of a pilot plant were estimated at 33 months and $\$$25.6M. Taks 4, transport gasifier feed analysis, was to determine the effects of larger sized transport gasifier low rank coals within the AR dry solids pump. It was found for the two low-rank +100 mesh size transport gasifier coals that the cohesion of these larger materials was significantly less than the coals ground to minus 200 mesh. Also, the gas permeability of the MSL transport coal was found to be significantly higher than the permeability of the PRB transport coal. Task 5, coal-biomass mixture feed analysis, was to determine the effects of coal biomass blends within the AR ultra-dense phase feed system and dry solids pump, and to determine the cost of electricity increase of an integrated gasification combined cycle (IGCC) operating on coal/biomass blends with the AR dry solids pump and ultra-dense phase feed system. In summary, it was found that 75/25 wt% coal/corn stover blends produce reasonable economic results for IGCC operation with minimal dry solids pump modifications – especially if the coal is a low rank coal and the corn stover biomass is pelletized. The increase in electricity cost was found to be 1.1 cents/kWh. Task 6, coal-biomass mixture pilot scale tests, was to determine which coal/biomass blends could be tested in the current dry solids pump without major modifications. As reported in detail in the reports by Sprouse (2010) and Sprouse and Darby (2013), the coal/biomass blend having the least impact on pump configuration and operation is the 90/10 wt% Illinois #6 to corn stover ratio blend. The AGSD program was initiated on October 1, 2004. The interim final report was submitted on October 21, 2010 and covered Task 1, Task 2.1-2.9, and Task 3, performed during budget period 1. This final report covers Task 2.10-2.16, 4, 5, and 6, performed during budget period 2. The interim final report is attached as part of the appendix to this report.

Darby, Alan K.↗
DOE OSTI2024

Benefits and challenges in deployment of low global warming potential R290 refrigerant for room air conditioning equipment in California

High global warming potential gases (“high GWP”) are the fastest growing sector of greenhouse gas emissions in the world and in California and are primarily used as refrigerant gases in refrigeration and cooling equipment. Hydrofluorocarbons (HFCs) refrigerants are the dominant type of high GWP gases with GWP values thousands of times larger than CO 2 on a 100-year timescale. Refrigerant-grade propane (“R290”) has a very low GWP (GWP = 3.3) with good thermodynamic properties and good cooling equipment performance but the flammability of any leaked refrigerant makes equipment design, handling, and maintenance critical factors to manage. This paper focuses on the potential climate benefits and costs of transitioning to R290 refrigerant in small room air conditioning (AC) units, specifically window AC, packaged terminal AC/heat pumps (PTAC/PTHP), and mini-split heat pumps. Overall climate impact for a transition to all three types of air conditioning units in the 2022–2051 timeframe is found to be from 15 to 64 million metric tons of greenhouse gas (GHG) savings in California with a cost of saved CO 2 eq that ranges from $14.50 per ton of CO 2 eq saved to -$50.30 per ton of CO 2 eq saved (net savings) depending on whether the baseline refrigerant is R32 or R410A and depending on the relative energy efficiency for R290 units compared to baseline units.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Broadband rotational spectroscopy of trans 3-pentenenitrile and 4-pentenenitrile

Titan, a moon of Saturn, has a nitrogen- and methane-rich atmosphere that is similar to prebiotic earth, and is replete with organic nitriles. Pentenenitriles have not yet been detected in Titan's atmosphere or in molecular clouds, but are potential precursors to hetero-aromatic compounds such as pyridine. We performed broadband microwave studies in the 8–18 GHz range on the trans isomer of 3-pentenenitrile (3-PN) and 4-pentenenitrile (4-PN) under jet-cooled conditions. Strong-field coherence breaking (SFCB) was used to selectively modulate the intensities of microwave transitions in a conformer-specific manner for 3-PN, aiding analysis. Two conformers of 3-PN and five conformers of 4-PN were identified and the rotational transitions were assigned. Evidence for methyl internal rotation splitting was observed for both the conformers of 3-PN, and the barrier heights of both conformers was determined experimentally. Comparison is made of the conformational preferences, stability and isomerization barriers through the acquired rotational spectra and potential energy surface (PES) calculations of the structural isomers 3-PN and 4-PN.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1987

High-resolution synchrotron X-ray study of the structure of La(1.8)Ba(0.2)CuO(4-y)

X-ray diffraction of La(1.8)Ba(0.2)CuO(4-y) reveals two macroscopically segregated tetragonal (K2NiF4-type) phases of nearly identical lattice parameter. Many peaks show additional broadening upon cooling. This broadening is consistent with a spontaneous monoclinic distortion, with an onset temperature of about 150 K, and is possibly relevant to the superconducting properties. Small single crystals of about 70 micron diameter within the powder aggregate are also studied and show a similar two-phase constituency and a resolvable peak splitting at low temperature.

Moss, S. C.↗
NASA NTRS1989

Forced air heat sink apparatus

A high efficiency forced air heat sink assembly employs a split feed transverse flow configuration to minimize the length of the air flow path through at least two separated fin structures. Different embodiments use different fin structure material configurations including honeycomb, corrugated and serpentine. Each such embodiment uses a thermally conductive plate having opposed exterior surfaces; one for receiving a component to be cooled and one for receiving the fin structures. The serpentine structured fin embodiment employs a plurality of fin supports extending from the plate and forming a plurality of channels for receiving the fin structures. A high thermal conductivity bondant, such as metal-filled epoxy, may be used to bond the fin structures to either the plate or the fin supports. Dip brazing and soldering may also be employed depending upon the materials selected.

Rippel, Wally E.↗
NASA NTRSDate not supplied

Numerical Modeling of No Vent Filling of a Cryogenic Tank with Thermo-dynamic Vent System Assisted Injector

This paper presents a multi-node finite volume model of No Vent Filling (NVF) of a cryogenic tank with Thermo-dynamic Vent System (TVS) assisted injector, using the Generalized Fluid System Simulation Program (GFSSP), a general purpose flow network code. NVF tests were conducted in a CRYOgenic Orbital Testbed (CRYOTE) tank which was filled by liquid nitrogen using a TVS assisted injector with vent valve closed during the entire filling process. In TVS assisted injector, the liquid flow splits into two streams: one stream is routed to a Joule-Thomson (J-T) orifice where the flow immediately flashes from liquid to vapor or two phase mixture because the downstream to J-T leg is maintained at vacuum level.; the other stream is injected into the tank after being cooled by cold vapor of J-T leg in a heat exchanger. The flow through J-T leg is also used to cool the outer metal matrix of the injector which in turn cools the vapor in the tank ullage. The cooling of vapor in the ullage by cold injector surface reduces ullage pressure that allows liquid to enter and fill the tank. An integrated numerical model of the test set up was developed. The model included the dual lines of TVS assisted injector, tank and tank wall. The tank was discretized into multiple fluid nodes and branches to represent the ullage and liquid nitrogen and multiple solid nodes to represent the tank wall and structure. The heat transfer between solid to fluid was calculated from pool boiling correlations which include film, transition, and nucleate boiling, as well as natural convection during pre- and post-boiling. The model also accounts for the condensation of vapor at ullage-injector interface and when it comes in contact with the liquid spray. The predicted pressure, resident mass, wall temperature in the tank were compared with the test data.

Alok Majumdar↗
DOE OSTI2013

Energy Simulation of Integrated Multiple-Zone Variable Refrigerant Flow System

We developed a detailed steady-state system model, to simulate the performance of an integrated five-zone variable refrigerant flow (VRF)heat pump system. The system is multi-functional, capable of space cooling, space heating, combined space cooling and water heating, and dedicated water heating. Methods were developed to map the VRF performance in each mode, based on the abundant data produced by the equipment system model. The performance maps were used in TRNSYS annual energy simulations. Using TRNSYS, we have successfully setup and run cases for a multiple-split, VRF heat pump and dehumidifier combination in 5-zone houses in 5 climates that control indoor dry-bulb temperature and relative humidity. We compared the calculated energy consumptions for the VRF heat pump against that of a baseline central air source heat pump, coupled with electric water heating and the standalone dehumidifiers. In addition, we investigated multiple control scenarios for the VRF heat pump, i.e. on/off control, variable indoor air flow rate, and using different zone temperature setting schedules, etc. The energy savings for the multiple scenarios were assessed.

Energy Modeling↗