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Showing papers on "Thermal energy published in 1994"


Patent
08 Aug 1994
TL;DR: In this paper, a fluid connection is provided between the distal portions of two adjacent, thin-walled, high strength fluid lumens to define a closed loop fluid circulation system capable of controlled delivery of thermal energy to or withdrawal from remote internal body locations.
Abstract: Heat transfer catheter apparatus and methods of making and using same are disclosed wherein a fluid connection is provided between the distal portions of two adjacent, thin-walled, high strength fluid lumens to define a closed loop fluid circulation system capable of controlled delivery of thermal energy to or withdrawal of thermal energy from remote internal body locations.

381 citations


Journal ArticleDOI
TL;DR: In this article, the entropy production is separated into three subprocesses: (1) combined diffusion/fuel oxidation, (2) internal thermal energy exchange (heat transfer), and (3) product constituent mixing process.
Abstract: Approximately 1/3 of the useful energy of the fuel is destroyed during the combustion process used in electrical power generation. This study is an attempt to clarify and categorize the reasons for the exergy destruction taking place in combustion processes. The entropy production is separated into three subprocesses: (1) combined diffusion/fuel oxidation, (2) “internal thermal energy exchange” (heat transfer), and (3) the product constituent mixing process. Four plausible process paths are proposed and analyzed. The analyses are performed for two fuels: hydrogen and methane. The results disclose that the majority (about 3/4) of the exergy destruction occurs during the internal thermal energy exchange. The fuel oxidation, by itself, is relatively efficient, having an exergetic efficiency of typically 94% to 97%.

240 citations


Journal ArticleDOI
TL;DR: A review of the theoretical bases describing heat transfer in each regime is followed by a discussion of the obstacles confronted in current research as discussed by the authors, highlighting the potential applications of micro-scale heat transfer for cryogenic systems, material processing, and electronic, optical, and optoelectronic devices.
Abstract: This work addresses challenges in the emerging field of microlength scale radiative and conductive heat transfer in solids and recommends specific directions of future research. Microlength scale heat transfer involves thermal energy transport processes in which heat carrier characteristic lengths become comparable to each other or the characteristic device dimension. Identification of these characteristic lengths leads to the definition of different microscale heat transfer regimes. A review of the theoretical bases describing heat transfer in each regime is followed by a discussion of the obstacles confronted in current research. Engineering challenges are illustrated with the applications of microscale heat transfer in cryogenic systems, material processing, and electronic, optical, and optoelectronic devices. The experimental difficulties discussed have hampered the development of microscale heat transfer research and deserve great efforts to overcome them. 84 refs., 9 figs., 3 tabs.

150 citations


Patent
20 Jun 1994
TL;DR: In this article, a power generating system comprises a solar concentrator defining an effectively concave reflective surface on a surface of the earth for concentrating incoming solar energy, and a solar collector is disposed in an underground chamber provided with an access opening.
Abstract: A power generating system comprises a solar concentrator defining an effectively concave reflective surface on a surface of the earth for concentrating incoming solar energy. A solar collector is disposed in an underground chamber provided with an access opening. The solar collector receives solar energy concentrated by the concentrator and converting the concentrated solar energy to another energy form, generally thermal energy, which is subsequently convertible to electrical power. Directional componentry is provided for directing concentrated solar energy from the concentrator along a predefined folded transmission path through the access opening to the collector.

90 citations


Journal ArticleDOI
TL;DR: In this paper, the authors employed data from the airborne Thermal Infrared Multispectral Scanner (TIMS) to measure thermal (i.e., longwave) energy responses, emitted or upwelling, from discrete surfaces that are typical of the city landscape within Salt Lake City, Utah, over a single diurnal time period.
Abstract: This study employs data from the airborne Thermal Infrared Multispectral Scanner (TIMS) to measure thermal (i.e., longwave) energy responses, emitted or upwelling, from discrete surfaces that are typical of the city landscape within Salt Lake City, Utah, over a single diurnal time period (i.e., a single day/night-time sequence). These data are used to quantify the disposition of thermal energy for selected urban surfaces during the daytime and night-time, and the amount of change in thermal response or flux recorded between day and night. An analysis is presented on the thermal interrelationships observed for common urban materials for day, night, and flux, as identified from the TIMS data through the delineation of discrete surface type polygons. The results from the study illustrate that such factors as heat capacity, thermal conductivity, and the amount of soil moisture available have a profound impact on the magnitude of thermal energy emanating from a specific surface and on the dynamics of ...

90 citations


Patent
11 Aug 1994
TL;DR: In this paper, the authors present a thermal energy storage system for maintaining a temperature in a vehicle compartment, which includes a thermal charging cycle and a thermal discharging cycle, each of which is operable in heating capacity storage and discharge modes.
Abstract: A thermal energy storage system is operable in heating capacity storage and discharge modes and cooling capacity storage and discharge modes for maintaining a temperature in a vehicle compartment. Each mode includes a thermal charging cycle and a thermal discharging cycle. The thermal energy storage system communicates with a vehicle air conditioning system including a compressor and a vehicle coolant system including a vehicle engine. The thermal energy storage system comprises a thermal storage apparatus housing thermal energy storage material that stores thermal energy. The thermal storage apparatus is connected to the air conditioning system and the coolant system so that a refrigerant or coolant flows through the thermal storage apparatus in heat transfer relationship with the thermal energy storage material.

65 citations


Patent
19 Oct 1994
TL;DR: The Atmospheric Energy Projection System (AEPS) as discussed by the authors is a means to project electrical/thermal energy using microwave radiation at the resonant frequency of oxygen, which excites a column through the ambient atmosphere to a temperature such that air within the column is converted from an insulator to a conducting channel or focused medium.
Abstract: The Atmospheric Energy Projection System (AEPS) is a means to project electrical/thermal energy using microwave radiation at the resonant frequency of oxygen. The radiation excites a column through the ambient atmosphere to a temperature such that air within the column is converted from an insulator to a conducting channel or focused medium. An electrical current is subsequently applied to the channel to transmit an electric charge a predetermined distance. Rapid release of pulses of 60 GHz microwave radiation at a field strength below that for breakdown for the waveguide feeding the antenna or at the antenna aperture creates a channel without premature plasma generation. Once the channel is energized sufficiently, an electric charge is released into the channel and flows down it from the source to whatever solid the channel intersects. If no solid intrudes the charge diffuses harmlessly at the end of the heated channel as the channel cools back to the ambient temperature. Channel duration is a function of cross-sectional area, and channel length is a function of the amount of 60 GHz microwave energy radiated into the volume of interest. The radiated energy to make the channel in turn is a function of the power available and microwave source used. Shorter ranges require less power to create the channel. The amount of electrical charge released on the channel is dependent on the desired range and the amount of energy needed for the task at the end of the channel.

50 citations


Patent
23 Sep 1994
TL;DR: In this article, the authors proposed a recovery system for the dissipated energy of an engine motor vehicle during its running conditions, where the potential energy represented by compressed air, which is stored in a suitable storage vessel for its later use to produce mechanical energy, implies remarkable advantages for the huge saving of fuel and also for the absence of pollution of the environmental air.
Abstract: The instant invention is referred to a recovery system for the dissipated energy of an engine motor vehicle during its running conditions; such a system is substantially formed by the following subsystems: subsystem A: primary cooling system subsystem B: secondary cooling system subsystem C: exhaust gases circuit subsystem D: compressed air circuit subsystem E: braking circuit having an air compressor Such a system, wherein the thermal energy dissipated during the cooling of the engine motor and the kinetic energy 1/2 mv 2 dissipated during the braking action of the vehicle, are both recovered in form of potential energy represented by compressed air, which is stored in a suitable storage vessel for its later use to produce mechanical energy, implies remarkable advantages, in an absolute sense, for the huge saving of fuel and also for the absence of pollution of the environmental air.

50 citations


Patent
15 Apr 1994
TL;DR: In this paper, the authors propose a composition for thermal energy storage or thermal energy generation comprising a silica based gel or dry powder in the form of silica particles containing a water/urea phase change material for thermal storage or an endothermic or exothermic compound for thermal power generation.
Abstract: A composition for thermal energy storage or thermal energy generation comprising a silica based gel or dry powder in the form of silica particles containing a water/urea phase change material for thermal energy storage or an endothermic or exothermic compound for thermal energy generation. The water/urea phase change material stores and releases at least 50 cal/gm of thermal energy in freezing and melting, and has a melting and a freezing point in the range of -11° C. to -15° C. The endothermic compound is preferably ammonium nitrate, urea, or combinations thereof. The exothermic compound is preferably calcium oxide or calcium chloride. The thermal energy storage composition may find use in a variety of applications including medical wraps, food servingware, and "blue ice" for cold packs or food storage. The thermal energy generation composition may find use as medical wraps, food servingware, and refrigerators when endothermic and medical wraps, food servingware, heaters, stadium seats, boots, vests, caps ear muffs, and scarves when exothermic.

47 citations


Journal ArticleDOI
01 Jan 1994
TL;DR: In this paper, the temperature field over the whole cross section of an asynchronous electric machine (windings, stator and rotor core, insulation, air gap) is calculated under both steady-state and transient conditions.
Abstract: The temperature field over the whole cross section of an asynchronous electric machine (windings, stator and rotor core, insulation, air gap) is calculated under both steady-state and transient conditions. Thermal sources (copper losses) depend on rotor slip, deep-bar effect and windings temperature. All these quantities are, in the transient condition, functions of time. The thermal part of this coupled electro-thermal process is solved by the finite element method (FEM), while the electromagnetic part is dealt with by the equivalent circuit of the asynchronous machine. The air-gap problem is specially treated. The presented method can be applied to other electric machines having negligible axial thermal heat flow.

45 citations


Journal ArticleDOI
TL;DR: In this paper, the optical reflectance and transmittance spectra of complete windows for near normal and oblique angles of incidence are calculated from spectra for individual panes taking multiple reflections into account.

Patent
21 Nov 1994
TL;DR: A heat sink assembly for dissipating thermal energy from heat generating electrical components is described in this article.The heat sinking assembly includes a component support member and a housing which surrounds and clamps the electrical components to the heat sink wherein the components are not heat sunk until the first half of the housing assembly is attached to the circuit board or to the second half of a housing assembly.
Abstract: A heat sinking assembly for dissipating thermal energy from heat generating electrical components wherein the heat sinking assembly includes a component support member and a housing which surrounds and clamps the electrical components to the heat sink wherein the components are not heat sunk until the first half of the housing assembly is attached to the circuit board or to the second half of the housing assembly The clamping force for the electrical components may also be varied for optimum heat transfer

Journal ArticleDOI
TL;DR: In this paper, a generalized multi-parameter economic model was developed for optimizing the design and performance of hot dry rock (HDR) geothermal systems and key technical and institutional obstacles to universal heat mining were discussed in a more general context.
Abstract: The extraction of heat or thermal energy from the Earth—heat mining—has the potential to play a major role as an energy supply technology for the 21st century. However, even if reservoir productivity goals are achieved, the role of heat mining with today's energy prices and development costs is limited to only a small fraction of the Earth's surface. A generalized multi‐parameter economic model was developed for optimizing the design and performance of hot dry rock (HDR) geothermal systems. Key technical and institutional obstacles to universal heat mining are discussed in a more general context. Advanced concepts in drilling technology are reviewed in light of their potential impact on overcoming some of these obstacles to universal heat mining

Patent
20 Jan 1994
TL;DR: In this paper, a process and device for converting chemical energy from a fuel into thermal and at the same time directly into electrical energy, in which the primary fuel flow (1) is divided into at least two parallel and separately regulated partial flows (2, 3) taken to a fuel cell and a burner, and the oxygen vehicle flow (8) is regulated either in its entirety or in partial flows, in such a way that the electrical and thermal energy flows are fully decoupled.
Abstract: A process and device for converting chemical energy from a fuel into thermal and at the same time directly into electrical energy, in which the primary fuel flow (1) is divided into at least two parallel and separately regulated (4; 5) partial flows (2; 3) taken to a fuel cell (6) and a burner (7) and the oxygen vehicle flow (8) is regulated either in its entirety or in partial flows (12; 13) in such a way that the electrical and thermal energy flows are fully decoupled. The partial flow (12) of the oxygen vehicle intended for the high-temperature fuel cell (6) is preheated (14) by the entire exhaust gas current (25). The latter's thermal energy is used to prepare the primary fuel by evaporation (27) and conversion (26) and to provide useful heat (18; 19). A compact, integrated construction with a container (20) containing the fuel cell (6), the burner (7), the after-burner (28) and the converter (26) in the central section and the heat exchanger, lines, controls and accessories in the peripheral section.

Patent
04 Jul 1994
TL;DR: In this article, a method for improving the total production of useful energy in an energy utilization system of a thermal power engine that is liquid-cooled and is used for the production of thermal energy as well as mechanical energy.
Abstract: A method for improving the total production of useful energy in an energy utilization system of a thermal power engine (1) that is liquid-cooled and is used for the production of thermal energy as well as mechanical energy. In the energy utilization system, thermal energy is taken from the coolant of the engine cooling system. At least a part of the coolant from the engine is led to a vaporization space (5) where, either by lowering the pressure or by increasing the amount of thermal energy within that space (5), a part of the coolant is transformed to vapor. The vapor is used within the energy utilization system for energy transport and/or as a medium for recovering energy.

Journal ArticleDOI
TL;DR: In this paper, the authors show that near-critical variations in fluid properties can enhance convective heat transfer by a factor of 10 ¼ or more (superconvection) if permeability is sufficiently high.
Abstract: Near-critical extrema in the properties of water may influence flow patterns in hydrothermal systems, but singularities in equations of state for H2O at its critical point have inhibited quantitative modeling Posing governing equations in terms of pressure (P) and enthalpy (H) avoids these singularities and facilitates computation Numerical simulations with a P-H based model show little near-critical enhancement in heat transfer for systems in which flow is driven by fixed pressure drops However, in density-driven systems, near-critical variations in fluid properties can enhance convective heat transfer by a factor of 10² or more (“superconvection”) if permeability is sufficiently high Near-critical two-phase processes (“heat pipes”) are at least equally effective at dissipating thermal energy The restriction to high-permeability environments within a fairly narrow P-H window suggests that superconvection may be quite rare in natural systems

Patent
08 Sep 1994
TL;DR: In this paper, a rotary fan is mounted adjacent the outer extremity of the pins of the heat sink body, providing a large surface area for the Heat Sink body.
Abstract: Heat sink apparatus for cooling large electronic devices is formed with a heat sink body having a plurality of pins extending outwardly from the base of the heat sink body and a rotary fan having a blowing surface mounted adjacent the outer extremity of the pins. The pins are separated by intersecting grooves providing a large surface area for the heat sink body. The surface area of the heat sink body is sufficiently large to provide a thermal impedance of substantially less than 1.0° C./W and the volume occupied by the heat sink is sufficiently small to provide a volume performance value of less than about 6° C. in 3 /W.

Journal ArticleDOI
TL;DR: A steady-state thermal radiance model to compute thermal exitance and energy balance within forest canopies is described and comparisons for a dense spruce-fir forest study site in central Maine are given.
Abstract: A steady-state thermal radiance model to compute thermal exitance and energy balance within forest canopies is described. The model treats fully leafed canopies as discrete ensembles of leaves partitioned into slope-angle and height classes. Short-wave energy flux absorbed within the canopy is estimated by solving simplified radiosity equations. Sensible heat exchange is estimated using a logarithmic wind profile above the canopy and a modified exponential profile within the canopy. The latent heat boundary layer resistance is estimated from site-specific measurements summarizing the effects of solar irradiance, air temperature, and vapor pressure deficit on stomatal conductance. Example comparisons for a dense spruce-fir forest study site in central Maine are given. For clear days the resulting root mean square error in modeled versus measured canopy temperatures was 1.2/spl deg/C. Corresponding errors in latent and sensible heat flux energy budget terms were 30 and 32 W/m/sup -2/, respectively. For partly cloudy days the root mean square error in predicted temperature was 1.0/spl deg/C and corresponding errors in latent and sensible heat were 40 and 110 W/m/sup -2/. >

Patent
17 May 1994
TL;DR: In this article, a recording head has a substrate which includes plural thermal energy generating elements for generating thermal energy, plural wiring lines electrically connected with associated thermal energy generators, and a temperature detecting element built in the substrate.
Abstract: The present invention involves recording apparatus having such a recording head that records using thermal energy. The recording head has a substrate which includes plural thermal energy generating elements for generating thermal energy, plural wiring lines electrically connected with associated said thermal energy generating elements, and a temperature detecting element built in the substrate. This temperature detecting element is either a diode or a transistor.

Journal ArticleDOI
TL;DR: In this paper, energy balance equations for a passive solar crop dryer with shallow bed, including the effect of a reflector placed over the wall of the chimney, have been written in terms of design and climatic parameters.

Patent
23 Sep 1994
TL;DR: In this paper, a hybrid combined cycle power plant including a solar central receiver for receiving solar radiation and converting it to thermal energy is described. But the power plant includes a molten salt heat transfer medium for transferring the thermal energy to an air heater, and the air heater is used to preheat the air from the compressor of the gas cycle.
Abstract: A hybrid combined cycle power plant including a solar central receiver (7) for receiving solar radiation and converting it to thermal energy The power plant includes a molten salt heat transfer medium (8) for transferring the thermal energy to an air heater (9) The air heater (9) uses the thermal energy to preheat the air from the compressor (12) of the gas cycle The exhaust gases from the gas cycle are directed to a steam turbine (16) for additional energy production

Journal ArticleDOI
TL;DR: In this article, the authors describe two developments which shall lead to prototype systems of a heat transformer for industrial use and a thermal energy store for small-scale solar energy stations, which can contribute significantly to an environmentally clean energy technology.

Journal ArticleDOI
TL;DR: In this article, a general form of the Green's function solution method for finite bodies is introduced for wave-type conduction equations, where the wave nature of thermal energy transport is dominant.

PatentDOI
TL;DR: In this article, a pin array is used to provide a convex fluid-solid interface in a plane perpendicular to an axis for acoustic oscillation of fluid between the two heat exchangers.
Abstract: A thermoacoustic stack for connecting two heat exchangers in a thermoacoustic energy converter provides a convex fluid-solid interface in a plane perpendicular to an axis for acoustic oscillation of fluid between the two heat exchangers. The convex surfaces increase the ratio of the fluid volume in the effective thermoacoustic volume that is displaced from the convex surface to the fluid volume that is adjacent the surface within which viscous energy losses occur. Increasing the volume ratio results in an increase in the ratio of transferred thermal energy to viscous energy losses, with a concomitant increase in operating efficiency of the thermoacoustic converter. The convex surfaces may be easily provided by a pin array having elements arranged parallel to the direction of acoustic oscillations and with effective radial dimensions much smaller than the thicknesses of the viscous energy loss and thermoacoustic energy transfer volumes.

Patent
01 Aug 1994
TL;DR: In this article, a simple, reliable and thermally efficient apparatus for incorporating thermal energy storage in domestic-sized air-conditioning systems is disclosed, which incorporates a chilled-water (or other chilled liquid) loop with two previously patented apparatus.
Abstract: A novel simple, reliable and thermally efficient apparatus for incorporating thermal energy storage in domestic-sized air-conditioning systems is disclosed. This thermal energy storage apparatus for chilled water air-conditioning systems incorporates a chilled-water (or other chilled liquid) loop with two previously patented apparatus. The addition of a reliable and low cost chilled water loop to thermal energy systems for domestic-sized air-conditioning systems enables simple citing and modular construction of the thermal energy storage apparatus

Patent
05 May 1994
TL;DR: In this paper, a printed wiring board having electronic circuit devices such as semiconductors including a heat sink forming a housing for the printed wires board, one of the electronic devices being mounted on one portion of a heat spreader that is formed of a material having high thermal conductivity, another portion forming a thermal energy flow path to the heat sink, thereby lowering the junction temperature at the electronic device and increasing the reliability of the wiring board.
Abstract: A printed wiring board having electronic circuit devices (13, 44) such as semiconductors including a heat sink forming a housing (32, 36) for the printed wiring board, one of the electronic devices (13) being mounted on one portion (12) of a heat spreader that is formed of a material having high thermal conductivity, another portion (10) of the heat spreader forming a thermal energy flow path to the heat sink, thereby lowering the junction temperature at the electronic device (13) and increasing the reliability of the wiring board.

Patent
22 Sep 1994
TL;DR: In this article, a Stirling motor (hot-gas motor) is coupled with an electrical machine (12) which in the operating state works as an asynchronous generator and in the starting state works with an asynchronous motor.
Abstract: There exist installations which burn fuel and generate both electrical and thermal energy. In the emergency generating set, the electrical energy is generated only for one's own requirements; in the heating and power station, the thermal energy is transported to the surrounding area as long-distance heat. Transportation of long-distance heat is expensive and requires an independent pipeline system, the transportation of electrical energy on the other hand is simple and can use the existing network. Based on this, the invention sets itself the object of providing a heating installation which consumes the generated thermal energy for heating one's own house and feeds electrical energy which has not been consumed by oneself into the general network. The network is thus relieved in times of peak demand. The invention solves this object by virtue of the fact that a Stirling motor (hot-gas motor) (10) which receives its inflow heat via the burner (6) and delivers its outflow heat to the heating circuit (1, 2, 3, 4, 5) is coupled to an electrical machine (12) which in the operating state works as an asynchronous generator and in the starting state works as an asynchronous motor. The concept of the invention can be applied in principle to any fuel-fired domestic heating installation.

Journal ArticleDOI
TL;DR: In this paper, the thermal energy flux of a rf plasma delivered to a silicon surface has been studied by a calorimetric method, and the energy flux appears to be proportional to the product of the average ion energy and the ion flux, which was calculated from the Bohm criterion using measured plasma parameters.
Abstract: The thermal energy flux which a rf plasma delivers to a silicon surface has been studied by a calorimetric method. The energy flux appears to be proportional to the product of the average ion energy and the ion flux, which was calculated from the Bohm criterion using measured plasma parameters. Furthermore, the value and energy dependence of the kinetic energy transfer efficiency (about 0.5) suggests that the microscopic interaction of impinging ions in the eV range with a silicon surface can be described by a binary collision model.

Journal ArticleDOI
TL;DR: In this paper, a two-dimensional, axisymmetric finite difference computer program was developed to model the canister walls, salt, void, and heat engine working fluid coolant.
Abstract: The Solar Dynamic Power Module being developed for Space Station Freedom uses a eutectic mixture of LiF-CaF[sub 2] phase-change salt contained in toroidal canisters for thermal energy storage. This paper presents results from heat transfer analyses of the phase-change salt containment canister. A two-dimensional, axisymmetric finite difference computer program which models the canister walls, salt, void, and heat engine working fluid coolant was developed. Analyses included effects of conduction in canister walls and solid salt, conduction and free convection in liquid salt, conduction and radiation across salt vapor-filled void regions, and forced convection in the heat engine working fluid. Void shape and location were prescribed based on engineering judgment. The salt phase-change process was modeled using the enthalpy method. Discussion of results focuses on the role of free convection in the liquid salt on canister heat transfer performance. This role is shown to be important for interpreting the relationship between ground-based canister performance (in 1-g) and expected on-orbit performance (in micro-g). Attention is also focused on the influence of void heat transfer on canister wall temperature distributions. The large thermal resistance of void regions is shown to accentuate canister hot spots and temperature gradients.

Patent
07 Oct 1994
TL;DR: A thermal energy storage and exchanger device includes a plurality of horizontal, superimposed, spaced plates defining a clear, horizontal, continuous, uniformly spaced flow passageways between them.
Abstract: A thermal energy storage and exchanger device includes, a plurality of horizontal, superimposed, spaced plates defining a plurality of clear, horizontal, continuous, uniformly spaced flow passageways between them; and introduction means selectively operable for driving a thermal energy exchanger fluid horizontally through the flow passageways to introduce thermal energy to the plates in one mode and extract thermal energy from the plates in a second mode; the plates being vertically spaced and horizontally oriented for minimizing convection and heat exchange in a third, storage mode when the thermal energy exchanger fluid resides in the flow passageways undriven by the introduction means.