264 Matching Results

Search Results

Advanced search parameters have been applied.

Non-Adiabatic Effects on Combustion Front Propagation in Porous Media: Multiplicity of Steady States

Description: The sustained propagation of combustion fronts in porous media is a necessary condition for the success of an in situ combustion project for oil recovery. Compared to other recovery methods, in situ combustion involves the added complexity of exothermic reactions and temperature-dependent chemical kinetics. In the presence of heat losses, the possibility of ignition and extinction (quenching) exists. In this report, we address the properties of combustion fronts propagating at a constant velocity in the presence of heat losses.
Date: March 11, 2002
Creator: Akkutlu, I. Yucel & Yortsos, Yanis C.
Partner: UNT Libraries Government Documents Department

Method for cutting steam heat losses during cyclic steam injection of wells. Sixth quarterly report

Description: Slot-cutting tests were made in a 3.5 in. OD steel pipe representative of the proposed liner of the twin gravel-packed horizontal drainholes used in this Method, for the following purposes: (1)To determine the force required to punch through the liner wall in order to achieve its full penetration with a cutting wheel, (2)To select the most effective profile for the cutting wheel. The results of these tests, made at UC-Berkeley indicated that, with four cutting wheels, as included in the tool design presented in the Fourth Quarterly Report, the total force required was nearly 60,000 lb. In view of the limited tool diameter, the creation of such a large force with a single piston required a hydraulic pressure which would exceed the capability of the Triplex pump, most commonly available in the oil fields. A re-design of the 4-wheel slot-cutting tool with two tandem pistons was done, but revealed a high degree of complexity, related to the difficulty of providing a high-pressure fluid path in the thin housing wall from the hydraulic cylinder above the first pair of arms to a cylinder for the tandem piston located below the first pair of cutter arms and operating the second pair of arms. By reducing the number of cutting wheels from 4 to 3 a single piston driver was sufficient and could result in a tool much simpler to build and to maintain in the Field.The re-designed 3-wheel slot-cutting tool is presented here. It is currently under construction at UC-Berkeley. A second test program will follow, when this simplified modular tool has been assembled. The objective of this second series of tests is to determine the required characteristics of the opposing spring, or Belleville rings stack which, in the new design, is used for retraction of the cutters, rather than for their ...
Date: August 1, 1995
Partner: UNT Libraries Government Documents Department

Heat loss from an open cavity

Description: Cavity type receivers are used extensively in concentrating solar thermal energy collecting systems. The Solar Total Energy Project (STEP) in Shenandoah, Georgia is a large scale field test for the collection of solar thermal energy. The STEP experiment consists of a large field array of solar collectors used to supplement the process steam, cooling and other electrical power requirements of an adjacent knitwear manufacturing facility. The purpose of the tests, conducted for this study, was to isolate and quantify the radiative, conductive, and convective components of total heat loss, and to determine the effects of operating temperature, receiver angle, and aperture size on cavity heat loss. An analytical model for radiative heat loss was developed and compared with two other methods used to determine radiative heat loss. A proposed convective heat loss correlation, including effects of aperture size, receiver operating temperature, and receiver angle is presented. The resulting data is a source to evaluate the STEP measurements.
Date: December 1, 1995
Creator: McDonald, C.G.
Partner: UNT Libraries Government Documents Department

Effects of plumbing attachments on heat losses from solar domestic hot water storage tanks. Final report, Part 2

Description: The Solar Rating and Certification Corporation (SRCC) has established a standardized methodology for determining the performance rating of the Solar Domestic Hot Water (SDHW) systems it certifies under OG-300. Measured performance data for the solar collector component(s) of the system are used along with numerical models for the balance of the system to calculate the system`s thermal performance under a standard set of rating conditions. SRCC uses TRNSYS to model each of the components that comprise the system. The majority of the SRCC certified systems include a thermal storage tank with an auxiliary electrical heater. The most common being a conventional fifty gallon electric tank water heater. Presently, the thermal losses from these tanks are calculated using Q = U {center_dot} A {center_dot} {Delta}T. Unfortunately, this generalized formula does not adequately address temperature stratification both within the tank as well as in the ambient air surrounding the tank, non-uniform insulation jacket, thermal siphoning in the fluid lines attached to the tank, and plumbing fittings attached to the tank. This study is intended to address only that part of the problem that deals with the plumbing fittings attached to the tank. Heat losses from a storage tank and its plumbing fittings involve three different operating modes: charging, discharging and standby. In the charging mode, the tank receives energy from the solar collector. In the discharge mode, water flows from the storage tank through the distribution pipes to the faucets and cold city water enters the tank. In the standby mode, there is no forced water flow into or out of the tank. In this experimental study, only the standby mode was considered.
Date: March 1, 1998
Creator: Song, J.; Wood, B.D. & Ji, L.J.
Partner: UNT Libraries Government Documents Department

Method for cutting steam heat losses during cyclic steam injection of wells. Final report

Description: Heavy Oil is abundant in California. It is a very viscous fluid, which must be thinned in order to flow from wells at economical rates. The best method of oil viscosity reduction is by cyclic steam injection into the oil-containing rock formations. Making steam in conventional generators fueled with Natural Gas is, however, a costly process. The main objective of this Project is to reduce the cost of the required steam, per Barrel of Oil produced. This is made possible by a combination of Patented new technologies with several known methods. The best known method for increasing the production rate from oil wells is to use horizontal drainholes, which provide a much greater flow area from the oil zone into the well. A recent statistic based on 344 horizontal wells in 21 Canadian Oil fields containing Heavy Oil shows that these are, on the average six times more prolific than vertical wells. The cost of horizontal wells, however, is generally two to three times that of a vertical well, in the same field, so our second goal is to reduce the net cost of horizontal wells by connecting two of them to the same vertical casing, well head and pumping system. With such a well configuration, it is possible to get two horizontal wells for the price of about one and a half times the price of a single vertical well.
Date: December 1, 1995
Creator: Gondouin, M.
Partner: UNT Libraries Government Documents Department

System for reducing heat losses from indoor swimming pools by use of automatic covers. [Quarterly] report No. 5, January 1, 1995--March 31, 1995

Description: To maintain comfortable and healthful temperatures in an indoor swimming pool, heat must be continually supplied to the pool water and to fresh air-that must be brought in for ventilation. Nearly all the heat added to the water is lost by evaporation into the air above the water surface. That very moist air must then be removed and replaced with relatively dry outdoor air that requires heating during most of the year. The cost of natural gas for supplying heat in a typical institutional pool is $10,000 to $25,000 Per Year. When the pool is not being used, typically half to two-thirds of the time, evaporation and the resulting heat demands can be eliminated by placing impervious covers on the water surface. On a schedule of use such as at Skyland, the pool can be covered and evaporation suppressed about two-thirds of the time, thereby saving about ten thousand dollars per year. Determination of the actual savings achieved by use of pool covers is the principal objective of this project. The program goal is the development of the technology and tools for achieving major reductions in the nation`s waste of energy.
Date: May 1, 1995
Partner: UNT Libraries Government Documents Department

IN-SITU MEASUREMENT OF WALL THERMAL PERFORMANCE: DATAINTERPRETATION AND APPARATUS DESIGN RECOMMENDATIONS

Description: Although the U-values of many building materials have been determined by laboratory testing, the in-situ thermal performance of walls, under either static or dynamic conditions, is not so well documented. This report examines the use of field measurements of heat flow and surface temperatures to determine the dynamic as well as static thermal performance of walls. The measurement strategies examined include both active devices, which generate their own heat fluxes on the wall surfaces, and passive devices, which rely on the weather to induce the required fluxes and temperature differences. Data obtained with both devices are analyzed with the Simplified Thermal Parameter (STP) model, which was designed to characterize a wall from flux and temperature measurements rather than from assumed material characteristics. The active measurement data are also analyzed with a modified version of the STP model that takes into account lateral heat losses. Some possible sources of error for both active and passive measurement strategies are also examined, and recommendations for both measurement strategies are given.
Date: September 1, 1984
Creator: Modera, M.P.; Sherman, M.H. & de Vinuesa, S.G.
Partner: UNT Libraries Government Documents Department

Development of fundamental power coupler for high-current superconducting RF cavity

Description: Brookhaven National Laboratory took a project of developing a 704 MHz five-cell superconducting RF cavity for high-current linacs, including Energy Recovery Linac (ERL) for planned electron-hadron collider eRHIC. The cavity will be fed by a high-power RF amplifier using a coaxial Fundamental Power Coupler (FPC), which delivers 20 kW of CW RF power to the cavity. The design of FPC is one of the important aspects as one has to take into account the heat losses dissipated on the surface of the conductor by RF fields along with that of the static heat load. Using a simple simulation model we show the temperature profile and the heat load dissipated along the coupler length. To minimize the heat load on FPC near the cavity end, a thermal intercept is required at an appropriate location on FPC. A 10 K intercept was chosen and its location optimized with our simulation code. The requirement on the helium gas flow rate for the effective heat removal from the thermal intercept is also discussed.
Date: May 20, 2012
Creator: P., Jain; Belomestnykh, S.; Ben-Zvi, I. & Xu, W.
Partner: UNT Libraries Government Documents Department

On a thermal analysis of a second stripper for rare isotope accelerator.

Description: This memo summarizes simple calculations and results of the thermal analysis on the second stripper to be used in the driver linac of Rare Isotope Accelerator (RIA). Both liquid (Sodium) and solid (Titanium and Vanadium) stripper concepts were considered. These calculations were intended to provide basic information to evaluate the feasibility of liquid (thick film) and solid (rotating wheel) second strippers. Nuclear physics calculations to estimate the volumetric heat generation in the stripper material were performed by 'LISE for Excel'. In the thermal calculations, the strippers were modeled as a thin 2D plate with uniform heat generation within the beam spot. Then, temperature distributions were computed by assuming that the heat spreads conductively in the plate in radial direction without radiative heat losses to surroundings.
Date: August 4, 2008
Creator: Momozaki, Y. & Nolen, J.
Partner: UNT Libraries Government Documents Department

Fabrication and testing of thermoelectric thin film devices

Description: Two thin-film thermoelectric devices are experimentally demonstrated. The relevant thermal loads on the cold junction of these devices are determined. The analytical form of the equation that describes the thermal loading of the device enables one to model the performance based on the independently measured electronic properties of the films forming the devices. This model elucidates which parameters determine device performance, and how they can be used to maximize performance.
Date: March 1, 1996
Creator: Wagner, A.V.; Foreman, R.J.; Summers, L.J.; Barbee, T.W. Jr. & Farmer, J.C.
Partner: UNT Libraries Government Documents Department

Improving the energy efficiency of refrigerators in India

Description: Five state-of-the-art, production refrigerators from different manufacturers in India were subjected to a variety of appliance rating and performance evaluation test procedures in an engineering laboratory. Cabinet heat loss, compressor calorimeter, high-ambient pull-down, and closed-door energy consumption tests were performed on each unit to assess the current status of commercially available Indian refrigerators and refrigerator component efficiencies. Daily energy consumption tests were performed at nominal line voltages and at 85% and 115% of nominal voltage to assess the effect of grid voltage variations. These test results were also used to indicate opportunities for effective improvements in energy efficiency. A widely distributed ``generic`` computer model capable of simulating single-door refrigerators with a small interior freezer section was used to estimate cabinet heat loss rates and closed door energy consumption values from basic cabinet and refrigeration circuit inputs. This work helped verify the model`s accuracy and potential value as a tool for evaluating the energy impact of proposed design options. Significant differences ranging from 30 to 90% were seen in the measured performance criterion for these ``comparable`` refrigerators suggesting opportunities for improvements in individual product designs. Modeled cabinet heat loadings differed from experimentally extrapolated values in a range from 2--29%, and daily energy consumption values estimated by the model differed from laboratory data by as little as 3% or as much as 25%, which indicates that refinement of the model may be needed for this single-door refrigerator type. Additional comparisons of experimentally measured performance criteria such as % compressor run times and compressor cycling rates to modeled results are given. The computer model is used to evaluate the energy saving impact of several modest changes to the basic Indian refrigerator design.
Date: April 1, 1995
Creator: Sand, J.R.; Vineyard, E.A. & Bohman, R.H.
Partner: UNT Libraries Government Documents Department

Measurement techniques for single junction thermophotovoltaic cells

Description: Several measurement systems and techniques for the electrical and thermal characterization of thermophotovoltaic (TPV) cells are discussed. One computer controlled system measures the quantum efficiency of cells from 0.8 to 2.6 microns. A probe resistor is used to account for cells with low shunt resistances. In the second system, a production-style robot provides automated measurements of I-V characteristics under dark, blackbody, and flashed illumination conditions. The system measures the length and width of each cell, and calculates the open circuit voltage, short circuit current, fill factor, and maximum power for each cell. The mean and standard deviation of the measured parameters are also computed. The third system measures the overall cell efficiency by a calorimetric technique. Heat losses due to radiation, conduction, and convection are factored into the analysis method.
Date: October 1, 1998
Creator: Danielson, L.R.; Parrington, J.R.; Charache, G.W.; Nichols, G.J. & Depoy, D.M.
Partner: UNT Libraries Government Documents Department

Higher order mode analysis of the APT superconducting cavities

Description: In another contribution to this conference the design of superconducting cavities for low velocity proton beams will be reported. Besides an optimization of the rf properties of the accelerating {pi}-mode, other modes, possibly excited by the traversing proton beam, need to be regarded. The full spectrum of modes in {beta} = 0.64 and {beta} = 0.82 5-cell cavities, as proposed for the Accelerator Production of Tritium (APT) facility, has been calculated up to frequencies higher than 2.0 GHz. These have been evaluated for their potential to affect the beam. The presence of {open_quotes}trapped{close_quotes} modes has also been investigated. In addition to the specific mode spectrum, the total power deposited into the cavities by the beam has been determined from the induced wake-fields. Due to the operation with beams below the velocity of light, extreme care was required to prevent incorrect results by wave reflections from the boundaries of the calculation volume. The simulations indicate that a power deposition of up to 17 W per cavity can be expected in the worst case. This power might have to be removed by higher order mode couplers, which is a technically feasible task. Transporting this power out to a room temperature dump does not even noticeably increase the requirements to the cryogenic system. Also for the prevention of beam break-up effects and for suppression of resonant excitation of specific higher order modes (HOMs) it is of interest to investigate the removal of this HOM-power. Different approaches to implement this removal technically are entertained.
Date: August 1, 1997
Creator: Krawczyk, F.L.
Partner: UNT Libraries Government Documents Department

Thermal management of batteries using a Variable-Conductance Insulation (VCI) enclosure

Description: Proper thermal management is important for optimum performance and durability of most electric-vehicle batteries. For high-temperature cells such as sodium/sulphur, a very efficient and responsive thermal control system is essential. Heat must be removed during exothermic periods and retained when the batteries are not in use. Current thermal management approaches rely on passive insulation enclosures with active cooling loops that penetrate the enclosure. This paper presents the design, analysis, and testing of an enclosure with variable conductance insulation (VCI). VCI uses a hydride with an integral electric resistance heater to expel and retrieve a small amount of hydrogen gas into a vacuum space. By controlling the amount of hydrogen gas, the thermal conductance can be varied by more than 100:1, enabling the cooling loop (cold plate) to be mounted on the enclosure exterior. By not penetrating the battery enclosure, the cooling system is simpler and more reliable. Also, heat can be retained more effectively when desired. For high temperatures, radiation shields within the vacuum space are required. Ceramic spacers are used to maintain separation of the steel enclosure materials against atmospheric loading. Ceramic-to-ceramic thermal contact resistance within the spacer assembly minimizes thermal conductance. Two full-scale (0.8-m {times} 0.9-m {times} 0.3-m) prototypes were designed, built, and tested under high-temperature 200{degrees}-350{degrees}C battery conditions. With an internal temperature of 330{degrees}C (and 20{degrees}C ambient), the measured total-enclosure minimum heat loss was 80 watts (excluding wire pass-through losses). The maximum heat rejection was 4100 watts. The insulation can be switched from minimum to maximum conductance (hydrogen pressure from 2.0 {times} 10{sup -3} to 8 torr) in 3 minutes. Switching from maximum to minimum conductance was longer (16 minutes), but still satisfactory because of the large thermal mass of the battery.
Date: May 1, 1995
Creator: Burch, S.D.; Parish, R.C. & Keyser, M.A.
Partner: UNT Libraries Government Documents Department

Apparatus to measure liquid helium boil-off from low-loss superconducting current leads

Description: A low-loss liquid helium dewar was constructed to measure the liquid helium boil-off rate from high-temperature superconducting current leads. The dewar has a measured background heat leakage rate of 12 mW. Equations calculating the heat leakage rate from the measured vapor mass flow rate in liquid helium boil-off experiments are derived. Parameters that affect the experiments, such as density ratio, absolute pressure, and rate of pressure variation, are discussed. This study is important as superconducting current leads may be used in superconducting magnetic energy storage systems.
Date: June 1, 1995
Creator: Cha, Y.S.; Niemann, R.C. & Hull, J.R.
Partner: UNT Libraries Government Documents Department

Aquaculture information package

Description: This package of information is intended to provide background information to developers of geothermal aquaculture projects. The material is divided into eight sections and includes information on market and price information for typical species, aquaculture water quality issues, typical species culture information, pond heat loss calculations, an aquaculture glossary, regional and university aquaculture offices and state aquaculture permit requirements. A bibliography containing 68 references is also included.
Date: August 1, 1998
Creator: Boyd, T. & Rafferty, K.
Partner: UNT Libraries Government Documents Department

System for reducing heat losses from indoor swimming pools by use of automatic covers. Final report, October 1, 1993--September 30, 1995

Description: This final report is an account of the principal activities of Lof Energy Systems, Inc. in a two-year project funded by the Energy Related Inventions Program (ERIP) of the U.S. Department of Energy. The primary objective has been the development of a fully practical and economical system for saving energy in indoor swimming pools by use of motorized covers. The goal is wide-spread use of a fully developed product, in institutional swimming pools. Four major tasks, depicted in the accompanying Performance Schedule, have been completed, and one other has been initiated and its completion committed. Principal accomplishments have been the selection and improvement of cover materials and designs, lengthening and strengthening of reels and improvements in motorized components and their control, design and installation of pool covers in full scale demonstration and evaluation of fully developed commercial system, preparation and dissemination of manuals and reports, finalization of arrangements for Underwriters Laboratory certification of products, and final report preparation and submission. Of greatest significance has been the successful demonstration of the fully developed system and the verification and reporting by an energy consultant of the large savings resulting from pool cover use. Probably the best evidence of success of the DOE-ERIP project in advancing this invention to a commercial stage is its acceptance for sale by the Lincoln Equipment Company, a national distributor of swimming pool supplies and equipment. A copy of the relevant page in the Lincoln catalog is included in this report as Annex A. Representatives of that company now offer Tof motorized pool cover systems to their pool owner customers. In addition to the plans for securing UL certification the company expects to continue making design improvements that can increase system reliability, durability, and cost-effectiveness.
Date: January 1, 1996
Partner: UNT Libraries Government Documents Department

Evaluation of Foamseal ceiling panels in the large scale climate simulator under winder conditions. Phase I

Description: This report serves to document Phase I of tests on ceiling panels fabricated by Foamseal Urethane Technology, Inc. in the Large Scale Climate Simulator (LSCS). The work reported here was accomplished during August, 1991.
Date: November 1, 1991
Creator: Wilkes, K.E. & Childs, P.W.
Partner: UNT Libraries Government Documents Department

Thermal characteristics of a low-loss liquid-helium dewar

Description: A liquid helium dewar has been designed, fabricated, and operated successfully with a minimum background heat-loss rate of only a few milliwatts. The objective is to provide a facility that can be used to measure relatively low heat-loss rate (1--100 milliwatts) in a liquid helium environment. The experimental system consists mainly of an inner helium reservoir within an outer helium reservoir that is thermally shielded from the room-temperature environment by multiple insulation layers in a vacuum environment and a liquid nitrogen reservoir. The inner helium reservoir has a reduced cross-sectional (neck) area to minimize radiative and convective heat transfer to the liquid helium in the lower portion of the reservoir. Experimental results indicate that it takes a long time (>16 hours) for the system to cool down and reach the minimum heat-loss condition. Strong thermal interactions were observed between the inner and the outer reservoirs above the reduced cross-sectional area of the inner reservoir which is separated from the outer reservoir by a cylindrical stainless steel wall. Temperature measurements showed stratification in the vapor space above the liquid helium in the inner reservoir. Temperature distributions in the vapor space are not one-dimensional, and horizontal temperature gradients exist; this strongly suggests that natural convection may have persisted in the vapor space above the liquid helium in the inner reservoir. To alleviate the problem of strong thermal interactions between the inner and the outer reservoirs, we have since redesigned and tested an improved inner helium reservoir. The new reservoir has a heat intercept, an extended vacuum insulating space between the two helium reservoirs above the heat intercept, and an upper portion made of a thermally insulating epoxy fiberglass composite. Testing showed that interaction between the inner and the outer helium reservoirs of the new system is significantly lower than the original system.
Date: May 1, 1994
Creator: Cha, Y.S.; Niemann, R.C. & Hull, J.R.
Partner: UNT Libraries Government Documents Department

Insulation for a Thermionic Microbattery

Description: Microelectronmechanical Systems (MEMS) have not gained wide use because they lack the on-device power required by many important applications. To supply this need power, on can consider power from fossil fuels, but nuclear sources provide an intriguing option in terms of power density and lifetime. In order to make use of alpha particles, one is forced to use thermal approaches because diodes are damaged by the high energy of the alpha particles, one is forced to use thermal approaches because diodes are damaged by the high energy of the alphas. One difficulty, though, is that the surface to volume ration increases as we move to smaller scales and heat losses thus become significant at MEMS scales. Hence, efficient microscale insulation is needed to permit high overall efficiencies. This research explores concepts for one variety of microscale insulation created using MEMS fabrication techniques.
Date: September 19, 2004
Creator: Blanchard, James P.
Partner: UNT Libraries Government Documents Department

Les Software for the Design of Low Emission Combustion Systems for Vision 21 Plants

Description: Previous LES calculations for one SIMVAL case ({phi}{sub inj} = 0.7) have repeatedly shown that the heat transfer/heat losses were not correctly captured, resulting in predicted NO{sub x} emissions being much higher than measurements. In a current Navy Phase I SBIR project, we are studying ways to improve the prediction of heat transfer/heat loss in LES calculations. To improve our understanding of heat transfer at walls, a series of thermal channel flow cases were analyzed and compared to DNS predictions. When trying to fully resolve the boundary layer, it was found that the grid size in all directions (i.e. {Delta}x, {Delta}y, and {Delta}z) must be smaller than the size of eddies formed in the boundary layer. Thus, the cell aspect ratio at the wall needs to typically be less that 25 when the boundary layer is being resolved. In previous SIMVAL LES calculations, this cell aspect ratio requirement was not followed, and thus the heat transfer was less than desired. For this quarter, the grid was adjusted, and the SIMVAL case was rerun. The LES results show that vortices are now formed in the exhaust duct near the walls, resulting in more heat loss from the exhaust duct flow and lower NO{sub x} predictions (more in line with the measurements).
Date: April 1, 2004
Creator: Smith, Clifford E.
Partner: UNT Libraries Government Documents Department