Showing papers on "Thermal energy published in 1993"

Application of adsorption cooling systems to automobiles

Abstract: Adsorption cooling systems using water as the working fluid could minimize environmental problems associated with current automobile air conditioning systems. The exhaust heat could be used to provide the thermal energy input to the system. A number of problems have to be addressed, including adsorbent design and bed configurations. Techniques which might be used to achieve performance targets are discussed.

The production of hydrogen from solar radiation at high efficiency

Abstract: A method of producing hydrogen comprising, converting solar radiation into thermal energy and electrical energy, and using the thermal energy and the electrical energy for producing hydrogen and oxygen by electrolysis of water.

Hydrodynamic modes of a uniform granular medium

Abstract: This paper uses a fluid‐mechanical model of a granular medium to calculate the hydrodynamic modes of a spatially uniform basic state. These modes are the granular analogs of the heat, sound, and shear modes of the standard fluid. Attention is focused on the possibility of an unstable mode that might result in the spontaneous development of inhomogeneities in density. Two cases are considered: the cooling medium which loses energy without replenishment, and the heated medium which reaches a steady state when an energy source balances the loss of energy through particle collisions. The spatially uniform state of the cooling granular medium is unstable. Two modes, analogous to the shear and heat conduction modes of a standard fluid, are unstable at long wavelengths. The growth of these modes is algebraic, rather than exponential, in time. The shear mode does not involve the formation of density inhomogeneities, but the heat mode does. At long wavelengths the heat mode can be visualized by imagining a converging velocity increasing the density of particles in a certain region. The increased collisional dissipation of granular thermal energy reduces the pressure, and prevents it from reversing the convergent velocities, so the condensation is not checked. The stability of the heated granular medium depends on the energy source. If the energy source selectively deposits energy in hot regions of a disturbance, the diffusion and collisional damping can be overwhelmed, and the disturbance grows exponentially. The standard fluid (completely elastic particles) can be recovered as a special case of the heated granular medium. In all cases, waves analogous to the sound and heat conduction modes are present. In some cases, a second type of sound wave is present at long wavelengths with the peculiar property of being damped more quickly for more elastic particles.

Ocean Energies: Environmental, Economic and Technological Aspects of Alternative Power Sources

Abstract: State of the art offshore wind power stations ocean current energy conversion solar ponds waves current assessment of ocean thermal energy potential is tidal power coming of age? salinity energy geothermal energy marine biomass energy.

Solar chromospheric and transition region response to energy deposition in the middle and upper chromosphere

Abstract: We present results of a series of numerical simulations modeling chromosphere and transition region response to deposition of thermal energy ranging from ∼5×10 24 to 5×10 28 ergs in the middle or upper chromosphere. Assuming an initial model solar atmosphere on a rigid, vertical magnetic flux tube, we introduce a thermal energy source in the middle chromosphere and solve the resulting one-dimensional hydrodynamic equations. Our calculations include the dissipative effects of heat conduction, optically thin radiation losses in the corona, and an approximate expression for the radiation losses of lower temperature plasma

Thermally integrated heat exchange system for solid oxide electrolyte systems

Abstract: A thermally integrated heat exchange system for solid oxide electrolyte systems includes a thermally insulated furnace enclosure structure having an internal chamber therein and a plurality of solid oxide electrolyte plates disposed within the internal chamber. A heat exchanger particularly suited for use with the thermally integrated system has gas passageways for the flow of gases therethrough and is associated with the walls of the furnace enclosure. Thermal energy radiated from an operational solid oxide electrolyte system within the furnace enclosure may be used to preheat incoming reactant gases destined for use by the electrolyte plates. Exchange of thermal energy between hot exhaust gases and cooler incoming gases may also occur in the heat exchanger gas passageways that are substantially thermally integrated along their length.

Microwaved-activated thermal storage material; and method

Abstract: A thermal storage mixture activated by exposure to microwave energy is provided. The thermal storage mixture comprises a liquid phase of a microwave active fluid; and, a solid phase suspended within the microwave active fluid. The solid phase is preferably selected from material having a melting point at or below a temperature to which the liquid phase is heated, during use. The thermal storage mixture may be utilized in a container, to provide a thermal storage unit in a variety of applications. Herein, a thermal storage construction (heating construction) comprising a seat cushion having a thermal storage unit therein, to advantage, is described. Further, a process of storing thermal energy for release over an extended period of time is described.

Thermal nozzle combustion method

Abstract: A method for providing oxidant (3) into a combustion zone (2) employing a thermal nozzle (1) converting thermal energy into kinetic energy whereby a high injection velocity may be attained even at a low oxidant supply pressure and the injection velocity may be varied at any given supply pressure without changing nozzles or using an adjustable nozzle.

Thin-Film Selective Emitter

Abstract: Direct conversion of thermal energy into electrical energy using a photovoltaic cell is called thermophotovoltaic energy conversion. One way to make this an efficient process is to have the thermal energy source be an efficient selective emitter of radiation. The emission must be near the band-gap energy of the photovoltaic cell. One possible method to achieve an efficient selective emitter is the use of a thin film of rare-earth oxides. The determination of the efficiency of such an emitter requires analysis of the spectral emittance of the thin film including scattering and reflectance at the vacuum-film and film-substrate interfaces. Emitter efficiencies (power emitted in emission band/total emitted power) in the range 0.35-0.7 are predicted. There is an optimum optical depth to obtain maximum efficiency. High emitter efficiencies are attained only for low (less than 0.05) substrate emittance values, both with and without scattering. The low substrate emittance required for high efficiency limits the choice of substrate materials to highly reflective metals or high-transmission materials such as sapphire.

Integral heat sink interface

Abstract: An apparatus comprises a thermal energy generating device and a thermal energy dissipating device having a reduced thermal resistance of the interface between the two. The reduction is achieved by interposing a xylylene polymer layer between the two contact surfaces and applying a surface pressure sufficient to deform the xylylene polymer layer into the surface irregularities of the two surfaces. A reduction in the thermal resistance comparable to that which may be achieved by the use of a silicone grease or an indium foil may be realized if the layer is kept below eight times the air gap mean thickness caused by the surface irregularities. Layer thicknesses beyond this will serve to insulate or increase the thermal resistance between the two surfaces.

Fluid absorption receiver for solar radiation to power a Stirling cycle engine

Abstract: Disclosed are apparatus and methods 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. Also disclosed is a non-driven-flow fluid absorption receiver for preferred use with a Stirling engine incorporating absorption of infrared radiation.

Heat transfer via dense gas in a fluid circulation system

Abstract: A system and method for inducing flow of a dense gas through a fluid circuit without the use of a compressor or other pumping means. A heat absorption chamber has an outlet in fluid communication with the inlet of a heat rejection chamber and has an inlet in fluid communication with an outlet from the heat rejection chamber. Thermal energy absorbed by the dense gas in the heat absorption chamber causes the density of the dense gas to decrease sufficiently to cause the dense gas to flow to the heat rejection chamber. After heat energy is subsequently rejected from the heated dense gas, its density increases, and gravitational or radial acceleration forces acting thereupon induce the cooled, dense gas to flow to the heat absorption chamber displacing the dense gas therewithin. The fluid flow system of the present invention may be used for heat transfer or may be applied to processes such as solvent extraction, reduction of particle size, and oxidation of organic materials employing supercritical water.

Volatile organic compound abatement system

Abstract: A volatile organic compound (VOC) abatement system is provided which incorporates a carbon or zeolite type concentrating adsorption device, with VOCs collected upon the adsorption surfaces. A heat source is required heat gases flowing to the adsorption device in order to remove the concentrated VOCs. Also, heat is required to oxidize the VOCs into a safe form prior to their release into the atmosphere. The present invention employs a regenerative thermal oxidizer for efficiently combusting the VOCs prior their release into the atmosphere. The present system also employs a bypass valve for introducing a portion of the VOCs directly into a combustion chamber without regenerative preheating. The resulting lowering of thermal efficiency of the regenerative thermal oxidizer allows the exhaust from the regenerative thermal oxidizer to carry more thermal energy. The thermal energy from the exhaust is then transferred to a heat exchanger to heat gasses flowing into the adsorption device.

Web thickness control

Abstract: An improved apparatus providing for uniformity of web thickness is disclosed. In one aspect, the apparatus includes a plurality of gap-controlling, thermal energy sources, and in heat-exchange communication with the thermal energy sources, an assembly for compensating for temperature variation proximate to the thermal energy sources and across the apparatus width. The thermal compensating assembly includes a heat exchange jacket, and in combination therewith, a heat-exchanging, working fluid that undergoes a phase change in performing its heat exchange function.

Ion induced structures and electrical conduction in implanted polymer films

Abstract: A conducting-grain picture is presented, based on the idea that the ion-polymer interaction process can be simply described as a rapid dissipation of the thermal energy converted from the kinetic energy in the ion track region. Thermal dissipation and efficiency through electronic ionization and nuclear collisions are quite different. A critical transient temperature, determined by the critical energy deposition density, is necessary to activate a thermodynamic relaxation process along the ion track creating conducting graphitic grains. Our high resolution temperature-dependent dc conductivity data reveal a two component conductivity that depends on both one-dimensional variable-range hopping (VRH) and three-dimensional VRH. The relative importance of 3-D VRH conductivity over the entire conductivity seems to depend on the relative rate of the ion energy loss through electronic ionization processes.

Gelatinization and Melting of Starch and Tribochemistry in Extrusion

Abstract: Cooking of starch is traditionally achieved by supplying sufficient thermal energy to it as in baking and broiling processes. Whereas in extrusion cooking, both thermal and shear energy are usually present in doing the job. The relative importance of each of the two energy sources are difficult to assess in the process. The interactions between water and the anhydroglucose unit of the starch are discussed. The kinetics of starch conversion to cooked starch at excess or limited water contents are reviewed. Calorie per calorie, shear energy is more efficient in cooking starch than thermal energy. And shear energy alone, without thermal energy input, can cause cooking of starch if the energy level is high enough. In order to capitalize on the effect of shear energy on starch cooking, running the extruder at low temperatures, say lower than 50°C is recommended.

Thermal problem of curvilinear cracks in bonded dissimilar materials

Abstract: Boundary problems for a circular insert bonded partially to the interior of an infinite medium of another material under an uniform heat flow are formulated and solved in closed form. The unbonded portions of the interface may be regarded as circular arcs of discontinuities or curved cracks. By application of the complex function theory dealing with sectionally holomorphic functions, the present problem is reduced to the solution of the problem of linear relationship or Hilbert problem. Exact solution is given for an example of a single circular‐arc crack. It is found that the temperature gradients or heat flux near the tips of a curved crack possess the characteristic inverse square‐root singularity in terms of the radial distance away from the crack tip which is the same as those obtained for a straight crack between dissimilar materials. Due to this singular behavior, the heat flux intensity factor is introduced to measure the thermal energy intensification cumulated in the vicinity of the crack tip. Numerical results for the temperature and heat flux intensity factor are provided in graphic forms. It is shown that the material of a circular insert having a lower heat conductivity would make the heat flux intensity factor smaller. Consequently, the thermal energy intensification is diminished.

Method and system for storing thermal energy (heat energy)

Abstract: The present invention relates to a method and a system for storing thermal energy, chiefly as solar energy, by means of a thermal energy reservoir which alternately absorbs thermal energy with the aid of a heat carrier (heat-carrying medium, heating medium), and also gives it off again via said heat carrier. The method is characterised in that, in a manner temporally coupled to the supply of thermal energy, the heat carrier gives off thermal energy to a preferably thermochemical storage material in which the thermal energy is used for desorption of a working medium, and in the reverse case of the sorption of the gaseous phase of this working medium is given off again to the heat carrier.

Cooling apparatus for fluid and eatable foams

Abstract: The invention relates to an apparatus with a control for deep-freezing edible foams or other fluids to temperatures below -10 DEG C, while simultaneously producing a creamy state. At the same time, since use is made of a special twin-screw system which is temperature-controlled on the outside and on the inside, it is ensured that there is a mechanical energy input which is homogeneous to a great extent at the same time as heat dissipation which is spatially constant to a great extent. The optimum matching of mechanical energy input, homogeneous structural loading, subcritical shearing (minimisation of structural destruction), cooling gradient (taking into account dispersed energy) and freezing process is carried out according to the invention by means of controlling the mechanical and thermal energy balance on the basis of detecting the product consistency as the target variable. The product consistency is determined, for example, by means of on-line viscosity measurement.

Numerical investigation of thermo-chemical and mechanical erosion of ablative materials

Abstract: A transient, 2D material erosion model is developed to describe the simultaneous processes of thermochemical ablation and mechanical erosion of ablative materials. The model predicts the rate of surface recession and the erosion pattern by considering the effects of (1) thermal loading (i.e., applied surface heat flux and duration of heating), (2) particle loading, (3) transient heat conduction in the ablative material, (4) conversion of the kinetic energy of the impacting particles into thermal energy, (5) thermochemical degradation or pyrolysis of the polymer matrix, (6) advection due to the flow of decomposition gases, (7) thermal expansion of the carbonaceous char-layer, and (8) variation of the thermomechanical properties of the ablative material with temperature. Numerical calculations of the surface erosion for H41N have been performed. It is found that particle impact substantially alters the thermochemical ablation and thermal effect also changes the mechanical erosion. The predicted results for overall material erosion of H41N are found to agree reasonably well with available experimental data.

Operation method of thermal energy supply plant

Abstract: PURPOSE:To plan at a high speed an operation schedule having excellent energy saving and economization in a thermal energy supply plant including a heat storage apparatus. CONSTITUTION:A method comprises an initial heat storage plan preparation process 1000 in which there are prepared a plurality of heat storage plans each of specifying the amount of heat storage and the amount of heat radiation for each time so as to satisfy heat storage/dissipation conditions, a plan estimation process 2000, a plan selection process 3000 in which a plan is selected following an estimation value, and a plan alteration process 4000 in which the heat storage plan is partly altered, whereby a genetic algorithm is applied to the preparation and alteration of the heat storage plan to estimate a purposed heat storage plan. An optimum solution is therefore estimated at a high speed. Further, a plurality of alternate plans are estimated together with the optimum solution and any practical inconvenience of the estimated optimum solution is dealt with easily.