Showing papers on "Thermal energy published in 1992"

Ink-jet head

Abstract: PURPOSE:To use thermal energy for the curvature vibrations of a cover plate without waste by composing an ink-jet head of a base substrate, to which a plurality of ink liquid chambers are formed, the cover plate consisting of a sheet-shape insulator thermoelastically curved by thermal energy and a plurality of thin-film resistors for converting electric energy into thermal energy. CONSTITUTION:Thin film resistors 40 convert electric energy into thermal energy, and the top face of a cover plate 10 made up of sheet-shaped insulators with orifices 30 is given thermal energy. A temperature gradient can be generated for a minute time in the cover plate 10, the top face of which is given thermal energy, thus generating a thermo-elastic bending effect, then upward curving the cover plate 10 in a small quantity. When the cover plate 10 is curved upward, the volume of ink liquid chambers 24 organized of a base substrate 20 and the cover plate is increased, and ink is sucked. Since the sheet insulators having small thermal conductivity are used as the cover plate for the ink liquid chambers, heat dissipation is reduced, and ink can be flown and recorded by low driving power.

Numerical calculation of wall‐to‐bed heat‐transfer coefficients in gas‐fluidized beds

Abstract: A computer model for a hot gas-fluidized bed has been developed. The theoretical description is based on a two-fluid model (TFM) approach in which both phases are considered to be continuous and fully interpenetrating. Local wall-to-bed heat-transfer coefficients have been calculated by the simultaneous solution of the TFM conservation of mass, momentum and thermal energy equations. Preliminary calculations suggest that the experimentally observed large wall-to-bed heat-transfer coefficients, frequently reported in literature, can be computed from the present hydrodynamic model with no turbulence. This implies that there is no need to explain these high transfer rates by additional heat transport mechanisms (by turbulence). The calculations clearly show the enhancement of the wall-to-bed heat-transfer process due to the bubble-induced bed-material refreshment along the heated wall. By providing detailed information on the local behavior of the wall-to-bed heat-transfer coefficients, the model distinguishes itself advantageously from previous theoretical models. Due to the vigorous solids circulation in the bubble wake, the local wall-to-bed heat-transfer coefficient is relatively large in the wake of the bubbles rising along a heated wall.

Thermal energy storage in an unconfined aquifer: 2. Model development, validation, and application

Abstract: A fully three-dimensional numerical model for simulating coupled density-dependent groundwater flow and thermal energy transport is developed and validated. The transport solution is based on a finite element time integration algorithm which generates a symmetric coefficient matrix while retaining second-order accuracy in time. The use of a symmetric conjugate gradient solver for both the flow and transport matrices results in a high degree of computational efficiency. Three-dimensional deformable block elements are used to allow the model to conform to domains with irregular geometry. The thermal transport model is validated against the results of the Borden thermal injection field experiment presented in the companion paper. The model simulations provide an excellent match with the observed temperature distribution over time, with the effects of thermal buoyancy and losses across the ground surface accurately reproduced by the model. The model is shown to be a practical tool for simulating the type of low-temperature thermal transport problems that arise in connection with seasonal aquifer thermal energy storage and ground source heat extraction systems.

Thermally coupled pressure swing adsorption

Abstract: Pressure swing adsorption separation of a gas mixture is performed in an apparatus with a plurality of adsorbent beds cooperating to exchange energy from an adsorbent bed undergoing a depressurization step to an adsorbent bed undergoing a pressurization step, and with provision for thermal coupling in order to improve process efficiency. Thermal coupling is provided as heating to augment expansion energy recovery, and as a temperature gradient imposed in adsorbent beds to provide the function of a thermal regenerator in a regenerative thermodynamic cycle. The invention provides improved techniques for recovery of expansion energy in pressure swing adsorption, and for direct application of thermal energy to power pressure swing adsorption processes.

Thermal energy storage in an unconfined aquifer: 1. Field Injection Experiment

Abstract: A thermal injection and storage experiment was conducted to investigate the feasibility of storing thermal energy in shallow unconfined aquifers near the water table Heated water was injected into a shallow aquifer and plume temperatures were monitored over a 141-day period by means of a dense array of bundle-type piezometers The highly detailed data, which provide the three-dimensional temperature distribution within the aquifer, give good insight into the physical processes of aquifer thermal energy storage, and provide an excellent basis for the verification of simulation models The experimental data also allow the physical processes of heat advection, dispersion, retardation, buoyancy and boundary heat loss to be quantified In a companion paper, a three-dimensional density-dependent groundwater flow and thermal transport model is developed and validated using the results of the thermal injection experiment

Natural convection in a differentially heated square cavity with internal heat generation

Abstract: A high-resolution, finite-difference numerical study is reported on natural convection in a square cavity. The vertical sidewatts of the cavity are differentially heated, and a uniform internal heat generation is also present. Two principal parameters are considered, the internal Rayleigh number RaI, which represents the strength of the internal heat generation, and the external Rayleigh number Rag, which denotes the effect due to the differential heating of the side walls. The internal Rayleigh number varies in the range 1010 RaI ≤ 107, while the external Rayleigh number is set at RaE = 5 x 107 for most computations. As the relative strength of the internal heat generation increases, the flows near the tap portion of the heated sidewall are directed downward. When the effect of the internal heat generation is dominant, the thermal energy leaves the system for the surroundings over the top portion of the heated wall. Only in the bottom pari of the heated wall is heat transfer directed into the system. The...

Thermal Energy Analysis in Reciprocating Hermetic Compressors

Abstract: In this paper the thermal energy analysis of a reciprocating hermetic compressor is performed using a computational program The simulation model employed in the program is based on energy balances For the refrigerant gas inside the compressor cylinder use was made of the first law of thermodynamics including time variations of the mass and energy fluxes The required temperatures at the suction chamber, cylinder walls, discharge chamber, discharge muffler, compressor shell, and ambient inside the compressor shell are obtained from steady state energy balances at various locations within the compressor Effective overall heat transfer coefficients were determined experimentally, except for the heat transfer between the refrigerant and the cylinder walls which was obtained from existing correlations A companion simulation program which represents the compressor working features was used to calculate the mass fluxes at the suction, discharge, and the leakage flux Simulation results are presented for a small compressor and compared with experimental results Good agreement prevails indicating that the major effects affecting the thermal performance of the compressor have been considered by the proposed model INTRODUCTION There are several reports in the literature concerning numerical models to predict the performance of hermetic refrigeration compressors Those models require thermodynamic relationships to describe the behavior of the gas inside the cylinder These relationships can be obtained either through a polytropic transformation or through an energy balance A furth-er aspect to be considered is the heat transfer to and from the refrigerant as it passes through the compressor The models described in the literature differ mainly on how the two aforementioned issues are addressed On the next paragraphs some of the major works done on compressor modelling will be reviewed Qvale eta/ [l] indicated some areas where research should be done to improve the current knowledge on compressor modelling Heat transfer on the suction and discharge lines, on the valves, and between the gas and the cylinder walls are the most important points mentioned by the authors According to [l] the numerical models dealing with the cylinder of hermetic compressors have frequently employed the assumption of perfect gas in a polytropic process The exponent of the polytropic equation is usually adjusted to fit experimental results In this regard the polytropic index incorporates the combined effect of the heat transfer between gas and cylinder, friction, and deviations from the perfect gas behavior Therefore, the influence of these effects separately cannot be detected Karl! [2] investigated through the first law of thermodynamics the process described by a real gas inside the cylinder He considered the cylinder as a close system undergoing exchange of heat and work with the surroundings Prakash and Singh [3] also employed the first law of thermodynamics but assumed perfect gas behavior The heat transfer between the cylinder walls and the gas was predicted using the correlation given by Adair et a/ [4]· Rottger and Kruse [5] verified through their model that for the compressor performance it is important to use the equation of state for real gas but for the valve performance suffices to use the perfect

Integrated multi-chip module having a conformal chip/heat exchanger interface

Abstract: A multi-chip module having a conformal heat transfer interface to adapt to variations in the height and angle of integrated circuit chips and to achieve a thermal energy path between each chip and a heat sink. The conformal heat transfer interface includes a deformable metallic membrane and a liquid under pressure. The liquid has a high thermal conductivity and provides a pressure for deforming the metallic membrane to compensate for non-coplanarity of the chips. The module integrates the structural support, RF shielding, contamination-protection elements, and the heat-dissipating mechanism that are desired in the design of multi-chip modules. Double-sided cooling of the module significantly improves the thermal characteristics of a module, even in the absence of the conformal heat transfer interface.

Collisional energy transfer in highly excited molecules: Calculations of the dependence on temperature and internal, rotational, and translational energy

Abstract: Classical trajectory calculations of the rate of collisional energy transfer between a bath gas and a highly excited polyatomic method, and the average energy transferred per collision, as functions of the bath gas translational energy and temperature, are reported. The method used is that of Lim and Gilbert [J. Phys. Chem. 94, 72 (1990)], which requires only about 500 trajectories for convergence, and generates extensive data on the collisional energy transfer between Xe and azulene, as a function of temperature, initial relative translational energy (E’T), and azulene initial internal energy (E’). The observed behavior can be explained qualitatively in terms of the Xe interacting in a chattering collision with a few substrate atoms, with the collision duration being much too brief to permit ergodicity but with a general tendency to transfer energy from hotter to colder modes (both internal and translational). At thermal energies, trajectory and experimental data show that the root‐mean‐squared energy tr...

Mobile material decontamination apparatus

Abstract: A technique for decontaminating material, including disposing a grid network of perforated pipes on a base, and covering the same with contaminated soil. A barrier layer is laid on the contaminated material and provided with a vent port coupled to a vapor disposal unit via a suction system. A source of heated gas is coupled to the grid system to force heated air through the contaminated soil and vaporize the contaminants. A mobile decontamination system includes an insulated container having a top lid for loading contaminated material in the container, and an insulated back door for removing decontaminated material. Apertured pipes on the container floor convey a high temperature gas to the contaminated material to vaporize the contaminants. A suction system is coupled to a vapor outlet of the container to remove vaporized contaminants. The contaminated vapors are incinerated and either discharged as a harmless gas, or recirculated to the container for providing thermal energy and further vaporizing contaminants in the material.

Heat transfer device for use with a heat sink in removing thermal energy from an integrated circuit chip

Abstract: A heat transfer device for use with a heat sink in removing thermal energy from an integrated circuit chip. The inventive device includes a first membrane of flexible, thermally conductive material having a first surface in contact with the integrated circuit chip. A flexible, thermally conductive radial finger contact spring is disposed in contact with a second surface of the first membrane. A second membrane of flexible, thermally conductive material is included. The second membrane has a first surface in contact with the spring and a second surface in contact with the heat sink.

Automotive vehicle auxiliary component preheating method and system

Abstract: A method and system for preheating one or more auxiliary components of an automotive vehicle having an internal combustion engine or other means for producing hot exhaust gases. The method and system use waste thermal energy extracted from engine exhaust gases produced when the engine is running. This thermal energy is stored in a special thermal storage material in the form of chemical potential by a direct dehydration/hydration process. The thermal energy is released during a cold start and used to warm ambient air, which may then be conveyed to one or more desired auxiliary components, such as the catalytic converter, the passenger cabin or the like.

Antimatter-driven fusion propulsion scheme for solar system exploration

Abstract: The potential use of the proton-antiproton annihilation reaction as a driver for an inertially confined, magnetically insulated fusion plasma with application to advanced space propulsion is examined. The fusion scheme utilized is the magnetically insulated inertial confinement fusion (MICF) concept which combines the favorable aspects of both inertial and magnetic fusions into one. Using an appropriate set of governing equations for the fusion plasma, along with those that detail the annihilation reactions and the energy deposition by the annihilation products including contributions from muon catalysis, we calculate the energy gain for the system as well as the amount of antihydrogen needed to ignite the plasma. We find about 13 ng of antihydrogen are needed to supply a megajoule of energy to the plasma, and about 10 g will be needed for a 220-mT space vehicle to make a one-way trip to Mars in about 2 months. I. Introduction I N several previous publications1-3 we examined the potential use of the magnetically insulated inertial confinement fusion (MICF) concept as a propulsion device that could be utilized in solar explorations and/or interplanetary travel. The concept in question combines the favorable aspects of both magnetic and inertial fusions in that physical containment of the hot plasma is provided by a metallic shell while its thermal energy is insulated from the material wall by a strong, self-generated magnetic field as illustrated in Fig. 1. Unlike the conventional implosion-type inertial fusion schemes, energy production in this approach does not require compression of the fusion fuel to many times solid-state densities and simultaneous delivery of energy to the core to initiate the burn. Instead the fusion plasma is created through wall ablation by an incident laser beam that enters the target through a hole. The same laser gives rise to the strong magnetic field through a process known as the "thermoelectric" effect, whereby it can be shown that such a field can be generated in a hot plasma when its density gradient is perpendicular to its temperature gradient. We have seen that MICF is capable of producing specific impulses of several thousand seconds and thrusts of tens of kilonewtons that would allow round trips to Mars, for example, to be made in relatively short periods (a few months) even when the massive power supply system for the laser driver is carried on board. It is clear that such travel times can be substantially reduced if the power supply component is eliminated from the dry weight of the vehicle. Several recent studies4 have proposed beaming the needed energy from an Earth-orbiting space station, but it is evident that a more reliable performance can be assured if a compact energy source is taken along. Clearly no source can match that of matter-antima tter annihilation reactions since such a fuel (e.g., anti-hydrogen) possesses the largest specific energy, i.e., energy per unit mass, provided, of course, that the technology for producing, storing, and manipulating such

Fluid absorption receiver for solar radiation

Abstract: Disclosed are an apparatus and method used to preheat a working fluid for a subsequent solar-driven dissociation reaction. The working fluid is first passed through a blackbody receiver where it absorbs thermal energy, and is subsequently exposed to direct solar radiation. The present invention allows the working fluid to absorb relatively large amounts of solar energy at elevated temperatures, while the blackbody absorber remains at a relatively low temperature, thus minimizing energy losses through reradiation and enhancing the efficiency of the overall energy exchange.

Apparatus for recovery and use of waste thermal energy

Abstract: Energy recovery apparatus for recovering and using thermal energy comprises multiple series of shape memory elements having decreasing transformation temperatures from one element to the next in the direction of a heating fluid to extract heat over a range of fluid temperatures to effect a shape change of each element. Cooling fluid is flowed alternately through each series of elements to cool the elements and effect another shape change. The cooling fluid exiting a preceding series of elements is used as the heating fluid of the next series of elements to extract further heat indirectly from the original heating fluid. The shape changes of the elements are converted to mechanical work.

Transient Natural Convection in Enclosures With Application to Solar Thermal Storage Tanks

Abstract: Many previously studied natural convection enclosure problems in the literature have the bounding walls of the enclosure responsible for driving the flow. A number of relevant applications contains sources within the enclosure which drive the fluid flow and heat transfer. The motivation for this work is found in solar thermal storage tanks with immersed coil heat exchangers. The heat exchangers provide a means to charge and discharge the thermal energy in the tank. The enclosure is cylindrical and well insulated. Initially the interior fluid is isothermal and quiescent. At time zero, a step change in the source temperature begins to influence the flow. The final condition is a quiescent isothermal fluid field at the source temperature. The governing time-dependent Navier-Stokes and energy equations for this configuration are solved by a finite element method. Solutions are obtained for 10[sup 3] [le] Ra[sub D] [le] 10[sup 6]. Scale analysis is used to obtain time duration estimates of three distinct heat transfer regimes. The transient heat transfer during these regimes are compared with limiting cases. In this paper correlations are presented for the three regimes.

Models of energy-exchange mechanics applicable to a particle simulation of reactive flow

Abstract: Statistical particle simulations, such as the direct simulation Monte Carlo (DSMC) method, are appropriate for computationally modeling highly rarefied hypersonic flows about vehicles during atmospheric entry. Models of molecular interaction kinetics must account for the exchanges of energy occurring among the thermal energy modes during translational, rotational, and vibrational relaxation as well as dissociation, recombination, and atomic-exchange reactions in air. As presented here, models employed in a particle simulation for reaction mechanics are constrained by consideration s of detailed balance at equilibrium and conservation of linear momentum and energy. Equipartition of internal energy between rotational and vibrational modes promotes equilibrium and is compatible with the quantized nature of the simple harmonic oscillator. Postreaction energies may be proportionally partitioned among the thermal energy modes contributing to reaction, followed by thermal relaxation steps to promote detailed balance at equilibrium. Reaction selection rules, as functions of reactive collision energy, are structured to yield Arrhenius reaction-rate temperature dependence at equilibrium. The models described here are verified through simulation of superheated adiabatic reservoirs relaxing thermochemically to equilibrium.

Examination of heat transport during off-axis neutral beam injection in DIII-D

Abstract: Off-axis heating experiments have been conducted in DIII-D using 75 keV neutral beam injection as the auxiliary power source. The application of 7.5 MW of deuterium neutral beam power resulted in the plasma transiting into the high density H-mode confinement regime with equal electron and ion temperatures. The global thermal energy confinement was not affected by changing the heating location. A power balance analysis employing the 11/2-D ONETWO transport code and assuming purely diffusive heat transport found that the one-fluid effective diffusivity changed dramatically between the two cases. These results indicate the possibility that the local diffusivity is a function of some quantity other than the density, temperature and their gradients. An alternative explanation is that the diffusivity remains unchanged and that there is an inward non-diffusive heat flow to balance the power flow

Salt mixtures for storing thermal energy in the form of heat of phase transformation

Abstract: The invention relates to salt mixtures composed of Mg(NO3)2 ·6 H2 O and LiNO3 in a mass ratio of 86-81: 14-19 for storing and utilizing thermal energy in the form of heat of phase transformation. They are eminently suitable as latent heat storage media for heat reservoirs for storing and utilizing the waste heat of motor vehicle engines.

Evidence for a local diffusive model of transport in a tokamak

Abstract: Three series of recent experiments on JET have been dedicated to energy transport studies. Experiments with pellet injection followed by off-axis ICRH produce a heat sink on axis resulting in an inward thermal heat flux. A diffusive model for thermal flux with no heat pinch can adequately describe the data. It also describes the data from current ramp experiments in which total current is transiently decorrelated from the current distribution. The effective thermal diffusivity in L-mode confinement is found to scale with normalised Larmour radius according to Bohm in a series of non-dimensional scaling experiments.

Thermal interface crack problems in dissimilar anisotropic media

Abstract: The fundamental nature of an interface crack between dissimilar anisotropic media under the uniform heat flux is studied. Based on the Hilbert problem formulation and a special technique of analytical continuation, a simple and compact version of general solutions for the thermal field are given. The temperature gradients or heat fluxes are found to possess the characteristic inverse square‐root singularity in terms of the radial distance from the crack tip. Due to this singular behavior, the heat flux intensity factor is then introduced to quantify the thermal energy cumulated in the neighborhood of the crack tip. Some numerical examples are given for the application of the final results to the intensity factor of heat flux as well as the full field solutions of temperature. It is very interesting to see that the solutions associated with the dissimilar media can be easily obtained from the corresponding problem associated with the homogeneous media by a simple substitution of their own material properties. In general, the system possesses the symmetric properties of the thermal conductivity coefficients which can make the heat flux intensity factor smaller. Consequently, the thermal energy intensification is diminished.

Solar collector for combined water heating and electrical power - has panel with solar energy cells and transmits thermal energy to water

Abstract: A solar panel has a rectangular box-shaped housing (7) with a transparent cover (8). Located behind the panel is a further panel containing a matrix of solar cells (6). The cells are in good thermal contact with a heat conducting plate (9). A formed plate (10) has channels through which water is circulated from inlet (11) to outlet (12) and is heated in the process by the solar energy. ADVANTAGE - Combined heating of water and generation of electricity.

Absorption chillers improve cogeneration energy efficiency

Abstract: When power is being generated from fossil fuel and used as shaft horsepower or electrical energy, the process is only 20% to 35% thermally efficient if the waste heat from the prime mover is not effectively utilized Although there are new gas turbine engines that boast 40% thermal efficiency, they are not only on the market yet Fortunately, there are many ways to capture and utilize most of the 65% to 80% of the energy wasted in the conventional utility generation of electric energy This article discusses only those applications where the thermal energy available as waste heat can be converted to chilled water by the absorption process and used either as a commodity beyond the generation process or the enhance the generation process itself

Optimum Placement of Heat Sources in Forced Convection

Abstract: In many practical instances of heat transfer, such as furnaces, a certain minimum temperature must be attained on a given region. Usually the region is heated by forced convection with isolated heat sources upstream. The present note studies the placement of these heat sources such that the minimum temperature requirement is satisfied with the least amount of total thermal energy input. A circular region of radius R{prime} is to be heated to at least temperature T{sub 0}. There are N discrete heat sources forced by a uniform flow of velocity U. The question is, how can the authors place these sources such that the least amount of energy is required Since the thermal wake of a source in nonuniform, the answer is not obvious.

Thermomagnetic power generation apparatus using thermosensitive magnetic substance

Abstract: PURPOSE: To change low-temperature thermal energy into electric energy with high conversion efficiency by a method wherein thermosensitive magnetic substances are built into magnetic circuits, thermal energy is applied alternately to the thermosensitive magnetic substances, a change in a magnetic-flux is formed and the change is taken out as AC electric energy by an output coil CONSTITUTION: Warm water 9 and cold water 10 are changed over by a changeover valve 5, and they are sent into containers 1A, 1B which contain particles of a thermosensitive magnetic substance When the warm water is sent, the temperature of the thermosensitive magnetic substance becomes the Curie point or higher, it looses a magnetic property, and a magnetic flux does not flow When the cold water is sent, the permeability of the thermosensitive magnetic substance is increased, and a magnetic flux flow into magnetic circuits A, B as shown by arrows Since an output coil 3 is wound in the magnetic circuits A, B, a change in the magnetic flux is output to output terminals 11 as AC electric energy Thereby, low-temperature thermal energy can be changed into electric energy with high conversion efficiency COPYRIGHT: (C)1995,JPO