Showing papers on "Thermal energy published in 1990"
TL;DR: The response to a boundary heating of a very compressible, low-diffusivity, supercritical fluid under zero-gravity is studied by solving numerically the full non-linear one-dimensional Navier-Stokes equations.
Abstract: The response to a boundary heating of a very compressible, low-diffusivity, supercritical fluid (${\mathrm{CO}}_{2}$) under zero-gravity is studied by solving numerically the full non-linear one-dimensional Navier-Stokes equations. Both short (acoustic) and long (diffusion) time scales are investigated. A new mechanism of heat transport is seen, where the thermal energy is transformed into kinetic energy in a hot expanding boundary layer (the piston), which in turn is transformed in the bulk into internal energy. Steeply profiled waves are observed. In contrast to the ``critical slowing down'' behavior, the enhancement of heat transport is so important that it is nearly completed after 1% of the diffusion time.
199 citations
TL;DR: In this paper, the dependence of the x-ray emission from aluminum implosions above 1 keV on the energy per ion and per centimeter of the imploded Z-pinch array was investigated.
Abstract: Two energies are identified that define the x‐ray emission characteristics of Z‐pinch array implosions. One, the kinetic energy per ion, is intensive, and the other, the kinetic energy per centimeter, is extensive. From a series of one‐dimensional axisymmetric hydrodynamic calculations, we have calculated the dependence of the x‐ray emission from aluminum implosions above 1 keV on these energies. These calculations are carried out for a specially chosen theoretical case where the kinetic energy that is generated during implosion is converted to thermal energy and x rays during the plasma collision on axis in the absence of current. In this case, we determine the I4 to I2 transition of the scaling of emission with peak current, I, as a parametric function of the kinetic energy per ion. We also determine a functional dependence of the emission on this energy when the mass of the imploded aluminum array is held fixed. It is seen that the ability of the plasma to radiate large amounts of energy in either I4 o...
105 citations
Patent•
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24 Apr 1990
TL;DR: In this paper, the authors proposed to reduce the thermal deformation of a shadow mask by temperature up by forming a thermoelement layer of a compound semiconductor material on at least either surface on the electron gun side and panel face side of the shadow mask of a color picture tube.
Abstract: PURPOSE:To reduce the thermal deformation of a shadow mask by temperature up by forming a thermoelement layer of a compound semiconductor material on at least either surface on the electron gun side and panel face side of the shadow mask of a color picture tube. CONSTITUTION:A part of electron beams emitted from an electron gun is passed through a transmission hole 7 of a shadow mask and reached to a fluorescent film 5. About 40% of the remaining electron beams are reflected by a thermoelement layer 11A to the electron gun 9 side, while the dynamic energy of the further remaining electron beams is changed to a thermal energy in the element layer 11A. In addition to the Joule heat, an exothermic effect is caused by the Peltier effect. As the element layer 11A composed of a P-type compound semiconductor material has a high heat radiation rate and a small heat conductivity, the heat is difficult to transmit to a polymerized mask 6, and the generated heat in the element layer 11A is released into a vacuum envelope. Further, as the element layer 11A is polymerized with the iron mask 6, the mask 6 is cooled by the endothermic effect of the generated Peltier effect, and the thermal deformation is reduced.
104 citations
Patent•
18 May 1990
TL;DR: In this paper, an ad-sorption thermal storage system consisting of an evacuated vessel comprising a refrigerant, and an adsorbent heating or cooling section and an refrigerant condensing or evaporating section located in communication with each other, the former section including a finned heat transfer tube, the latter section including heat transfer tubes placed in dishes.
Abstract: An adsorption thermal storage apparatus formed of an evacuated vessel comprising therein a refrigerant, and an adsorbent heating or cooling section and a refrigerant condensing or evaporating section located in communication with each other, the former section including an adsorbent and finned heat transfer tubes, the latter section including heat transfer tubes placed in dishes. An adsorption thermal storage system comprising the aforesaid apparatus; a heat source (e.g. a condenser of a compression refrigerator) for adsorbent heating; a cold source (e.g. an evaporator) for refrigerant condensation; an exothermic heat source (e.g. cooling tower); an endothermic heat source (e.g. air cooling coil); and a utilization equipment (e.g. air conditioner), the foregoing elements being connected so that during thermal storage period, the adsorbent heating or cooling section and the refrigerant condensing or evaporating section communicate with the heat source and the cold source, respectively, whereas during utilization period, the adsorbent section communicates with the exothermic heat source or heat utilization equipment and the refrigerant section communicates with cold utilization equipment or the endothermic heat source. By the desorption, the refrigerant is condensed and thermal energy is stored whereas cold is generated by latent heat of evaporation of the refrigerant liquid and heat, by adsorption heat of the refrigerant vapor, whereby heat and cold may be utilized singly or simultaneously.
60 citations
Patent•
22 Feb 1990TL;DR: A thermal management system includes micro heat pipes extending radially outward from a heat sink which surrounds a heat source, rapidly conducting thermal energy away from the heat source as discussed by the authors, improving significantly the storage of thermal energy in the heat sink.
Abstract: A thermal management system includes micro heat pipes extending radially outward from a heat sink which surrounds a heat source, rapidly conducting thermal energy away from the heat source, improving significantly the storage of thermal energy in the heat sink, and providing a means for later dissipating thermal energy from the heat sink to an ultimate heat sink over a period of time.
47 citations
TL;DR: The technology is a long way behind that of infrared systems, but nevertheless microwave thermography has an interesting future.
Abstract: The association between temperature and disease is centuries old. Clinical thermology was established by Wunderlich, in 1851, who systemically recorded oral temperature with one of the first thermometers capable of reproducible measurement. Thermal imaging is highly developed with contemporary infrared imaging systems having thermal and spatial resolution far in excess of the earlier systems of the 1960s. Real time imaging, together with efficient on-line processing, has greatly improved the ease of use and quality of information. Microwave energy also forms a (smaller) part of the body's natural reactive heat loss. Research into natural microwave detection has shown that 3 GHz and 212 GHz energy can be measured. At the former wavelength a deeper source of thermal energy is measured; the actual depth varies with the characteristics of the superficial tissues, but may be up to several centimetres below the skin. The technology is a long way behind that of infrared systems, but nevertheless microwave thermography has an interesting future.
44 citations
01 May 1990
TL;DR: The elementary heat conduction experiment presented in this article is designed for associate degree technology students in a simple manner to enhance their intuition and to clarify many confusing concepts such as temperature, thermal energy, thermal conductivity, heat, transient and steady flows.
Abstract: The objective is to familiarize students with steady and unsteady heat transfer by conduction and with the effect of thermal conductivity upon temperature distribution through a homogeneous substance. The elementary heat conduction experiment presented is designed for associate degree technology students in a simple manner to enhance their intuition and to clarify many confusing concepts such as temperature, thermal energy, thermal conductivity, heat, transient and steady flows. The equipment set is safe, small, portable (10 kg) and relatively cheap (about $1200): the electric hot plate 2 kg (4.4 lb) for $175: the 24 channel selector and Thermocouple Digital Readout (Trendicator) 4.5 kg (10 lb) for about $1000; the three metal specimens (each of 2.5 cm diameter and 11 cm length), base plate and the bucket all about 3 kg (7 lb) for about $25. The experiment may take from 60 to 70 minutes. Although the hot plate surface temperature could be set from 90 to 370 C (maximum of 750 watts) it is a good practice to work with temperatures of 180 to 200 C (about 400 watts). They may experiment in squads of 2, 3 or even 4, or the instructor may demonstrate it for the whole class.
42 citations
Patent•
01 Mar 1990
TL;DR: In this paper, the authors consider a vehicle that must operate at its rated thermal output for at least the duration of a minimum desired operational cycle to provide the selected thermal capacity to the reservoir.
Abstract: Thermal energy is provided to a vehicle (20) that operates efficiently when operated for at least the duration of a minimum operational cycle. A reservoir (25) contains heat transfer liquid having a thermal capacity selected so that the burner must operate at its rated thermal output for at least the duration of the minimum desired operational cycle to provide the selected thermal capacity to the reservoir (25). With the liquid in the reservoir at maximum operating temperature and the burner off, heat is transferred from the thermal reservoir (25) to meet thermal demands of the vehicle (20). These demands decrease the temperature of the liquid to a minimum operating temperature, whereupon the burner is operated for at least the duration of the minimum desired operational cycle to raise the temperature of the liquid to the maximum operating temperature.
41 citations
TL;DR: In this article, a transient one-dimensional two-phase model is used to describe the temperature fields in the air and solid media constituting the bed, and numerical solution of the resulting two-coupled partial differential equations is obtained, and the variation of thermal energy stored with time is computed.
Abstract: The present paper is concerned with studying the effects of storage medium properties on the thermal behaviour of packed beds during charging. A transient one-dimensional two-phase model is used to describe the temperature fields in the air and solid media constituting the bed. The numerical solution of the resulting two-coupled partial differential equations is obtained, and the variation of thermal energy stored with time is computed. Solutions are obtained for a wide range of storage media (the solid phase) properties, namely density, thermal conductivity and specific heat. The results show that increasing either the density or specific heat increases the rate and capacity of energy storage, and decreases the rate of temperature rise throughout the storage medium. On the other hand, increasing the thermal conductivity is found to markedly increase the rate of temperature rise and energy stored inside the bed up to a certain time during charging, beyond which this trend completely reverses. In addition, the thermal storage properties of aluminum, steel and rock-packed beds are computed and compared.
41 citations
TL;DR: In this article, a correlation method of nucleate boiling heat transfer by considering the factors that affect the heat-transfer processes is described. And the authors also illustrate potential measures for augmentation of NBO heat transfer and some results obtained.
Abstract: Publisher Summary Nucleate boiling is a complicated phenomenon accompanied with a phase change from liquid to vapor. The nucleate boiling heat transfer is one of the most important modes of heat exchange occurring in several constituent devices of thermal plant. The augmentation of nucleate boiling heat transfer significantly contributes towards the efficient use of the thermal energy. The chapter describes a correlation method of nucleate boiling heat transfer by considering the factors that affect the heat-transfer processes. It presents the effect of surface configuration on the nucleate boiling along with the nucleate boiling heat transfer in a narrow space and in a liquid film. The chapter also illustrates potential measures for augmentation of nucleate boiling heat transfer and some results obtained. As the nucleate boiling heat transfer is greatly influenced by surface conditions, the unified rule of the nucleation factor for several surface conditions, which is similar to the emissivity encountered in the heat transfer by thermal radiation, needs to be developed in the future.
35 citations
TL;DR: In this article, an experimental study of natural convection heat transfer from a heat source module of finite thickness, mounted on a vertical or horizontal surface, is carried out, where temperature distributions in the flow and along the surface are measured.
01 Sep 1990
TL;DR: In this article, thermal energy storage (TES) can aid in the efficient use and provision of thermal energy, wherever there is a mismatch between energy generation and use, and many different media are available within each type.
Abstract: This paper discusses how thermal energy storage (TES) can aid in the efficient use and provision of thermal energy, wherever there is a mismatch between energy generation and use. Three fundamental types of thermal energy storage processes (sensible, latent, and thermochemical) can be used, and many different media are available within each type. Various subsets of these processes are being researched and developed to accelerate TES implementation, focusing on applications in building heating and cooling, industrial energy efficiency, and utility and space power systems. TES can contribute significantly to meeting society's needs for more efficient, environmentally benign energy use in these and other sectors.
Patent•
24 Sep 1990
TL;DR: In this paper, an Energy Producing Conglomerate (EPCON) system using wind energy, solar panels, and steam turbines producing electricity from the kinetic energy of wind and the thermal energy of the sun is described.
Abstract: The specification discloses an Energy Producing Conglomerate (EPCON) system using wind energy, solar panels, and steam turbines producing electricity from the kinetic energy of the wind and the thermal energy of the sun. A novel single shaft configuration that supports multiple induction generators which are driven by rotors of four windtraps and/or by steam turbines which receive steam pressure from solar panels. The steam is generated by solar lens panels. Solar parabolic collector dish or a natural gas steam boiler are also contemplated in the EPCON system. The energy producing field consists of up to a thousand of these windtrap units supported by a common water resource. A system controller supports the system by monitoring wind speeds, sun intensity, and load requirements and activates or deactivates system elements. An interconnect to a utility line and/or energy storage facility is part of the system. The units are mostly pre-fabricated with final installation on site without the need of any heavy equipment making it possible for buyers to install the EPCON system on their own. The windtrap unit along with the solar panels are shipped to the site via a specialized transporter that assists in the installation process. The system is further uniquely designed to be lowered to a relatively safe harbor in the event of excessive wind conditions. System maintenance is also simplified with this feature.
Journal Article•
TL;DR: In this article, the results of a comprehensive study specifically conducted to model transient CHF in pool boiling are presented, which includes the analysis of thermal energy conduction within the heater coupled with a macrolayer thinning model.
Abstract: The results of a comprehensive study specifically conducted to model transient CHF in pool boiling are presented in this paper. The model we developed includes the analysis of thermal energy conduction within the heater coupled with a macrolayer thinning model. Statistical variations in the vapor mass behavior also are incorporated into the model
TL;DR: Magnetic fluids, produced using highly temperature-sensitive ultrafine ferrites coprecipitated in alkaline solution containing zinc and calcium ions, were used in the heat convection pipe as mentioned in this paper.
01 Jun 1990-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, a mathematical model for the analysis and design of a combined direct current (DC) and radio frequency (RF) plasma reactor for advanced materials synthesis has been developed, where the velocity and temperature fields in the plasma are calculated by solving the turbulent Navier-Stokes equations and the thermal energy balance equation.
Abstract: A mathematical model for the analysis and design of a combined direct current (DC) and radio frequency (RF) plasma reactor for advanced materials synthesis has been developed. The RF electromagnetic field is calculated by solving Maxwell’s equations expressed in terms of the vector potential, which permits great flexibility in the specification of the RF coil design. The velocity and temperature fields in the plasma are calculated by solving the turbulent Navier-Stokes equations and the thermal energy balance equation. The model is used to study the thermal decomposition of silicon tetrachloride through the solution of the mass diffusion equation arid the associated reaction kinetics. It is found that the coupling between the flow and temperature fields generated by the RF and DC components significantly improves the silicon production and recovery in the reactor as compared with either DC or RF systems alone. In addition, the conversion efficiency of the hybrid system is found to depend on both the design and the operating parameters of the RF coil.
TL;DR: In this paper, the authors developed a macrolayer thinning model to predict critical heat flux (CHF) behavior during steady-state and transient conditions in a pool boiling environment.
Abstract: Understanding and predicting critical heat flux (CHF) behavior during steady-state and transient conditions is of fundamental interest in the design, operation, and safety of boiling and two-phase flow devices The results of a comprehensive study specifically conducted to model transient CHF in pool boiling are presented in this paper The model the authors developed includes the analysis of thermal energy conduction within the heater coupled with a macrolayer thinning model Statistical variations in the vapor mass behavior also are incorporated into the model The resultant model provides new insight into the basic physics of the CHF phenomenon and indicates favorable agreement with the experimental data from cylindrical heaters with small radii
Patent•
10 Aug 1990TL;DR: A thermal energy storage system comprising a germanium phase change material and a graphite container is described in this paper, where the graphite containers are used to store the phase change materials.
Abstract: A thermal energy storage system comprising a germanium phase change material and a graphite container
TL;DR: In this paper, the authors point out the need for a more rigorous definition of a heat exchanger as a system component, especially in a thermodynamic analysis of a system, and point out that the traditional heat exchange is useless for multi-fluid heat exchangers, especially concerning the definition of the single, overall heat exchange eflectiveness.
TL;DR: In this paper, the authors describe the use of photothermal signals, obtained from a photovoltaic cell subjected to periodic excitation, as a function of applied electrical potential, and of a simple geometrical construction, based on a plot of these, to analyze the photon energy by the cell.
Abstract: The authors describe the use of photothermal signals, obtained from a photovoltaic cell subjected to periodic excitation, as a function of applied electrical potential, and of a simple geometrical construction, based on a plot of these, to analyze the use of photon energy by the cell. The method is illustrated using examples obtained by a variety of experimental thermal detection schemes with crystalline Si, amorphous Si, and GaAs solid-state cells, as well as with liquid-junction (photoelectrochemical) cells, taking into account complications that arise if only part of the solar cell surface is illuminated, if only part of the thermal energy flux emanating from the cell's surface is detected, or if quantum efficiencies for current collection differ substantially from unity. >
TL;DR: In this paper, a high-temperature axially grooved heat pipe (HP) incorporated with thermal energy storage (TES) to mitigate pulse heat loads is presented, and the transient behavior of the HP/TES device is simulated using a three-dimensional numerical model based on finite-difference approximations.
Abstract: A novel design of a high-temperature axially grooved heat pipe (HP) incorporated with thermal energy storage (TES) to mitigate pulse heat loads are presented. The transient behavior of the HP/TES device was simulated using a three-dimensional numerical model based on finite-difference approximations. A phase-change material (PCM) encapsulated in cylindrical containers was used as thermal energy storage. The transient response of three different HP/TES configurations were compared: 1) heat pipe with one big empty cylinder installed in the vapor core, 2) heat pipe with one big PCM cylinder, and 3) heat pipe with six small PCM cylinders. From the numerical results, it was found that the PCM is very effective in mitigating the adverse effect of pulse heat loads on normal heat pipe operation.
Patent•
07 Jun 1990TL;DR: In this article, a process and an apparatus are described for the production of energy from biomass, the biomass if required ensiled or pelleted and fed to a biogas installation, in which natural fertiliser and natural gas from a public gas grid is burnt in a first apparatus and converted into thermal energy and/or electrical energy.
Abstract: A process and an apparatus are described for the production of energy from biomass, the biomass (at 10) if required ensiled or pelleted and fed to a biogas installation (12) in which biogas (arrow 20) and natural fertiliser (arrow 22) are produced. The biogas and/or natural gas from a public gas grid (26) is burnt in a first apparatus (30) and converted into thermal energy and/or electrical energy. By means of the electrical energy generated by the first apparatus (30) and, if necessary, by electrical energy from a public electricity grid (40) an electrolysis cell (34) is operated in which water is divided into hydrogen and oxygen. Hydrogen and oxygen can be converted back to electrical energy in a fuel cell (62), but the oxygen can also be used to improve the quality of wastewater (effluent) (at 60). The hydrogen can be stored in a storage facility (57) and/or be converted in a second apparatus (78) into thermal energy and/or into electrical energy or be used to drive motor vehicles (96) equipped with hydrogen engines.
Patent•
24 Oct 1990
TL;DR: In this article, the authors proposed a method to protect a semiconductor active device from thermal breakdown without actually measuring the temperature of the active device, instead, they measured the magnitude of the forward electrical signal generated by the active devices and the reflected electrical signal resulting from the interaction of the forwarding electrical signal and a load.
Abstract: The present invention relates to the protection of a semiconductor active device from thermal breakdown without actually measuring the temperature of the semiconductor active device. Instead, the present invention measures the magnitude of the forward electrical signal generated by the active device and the reflected electrical signal resulting from the interaction of the forward electrical signal and a load. The thermal energy generated by the active device is a function of these electrical signals. The generated thermal energy is transferred out of the active device at a predetermined rate. The temperature of the active device is calculated as a function of the thermal energy generated by the active device and the amount of thermal energy transferred out of the active device. When the calculated temperature is above a predetermined value, the active device is shut off, thereby preventing further generation of thermal energy.
TL;DR: In this article, the results of the study of the optimum thermo-fluid dynamic design concept are presented for turbine units operating within the open-cycle ocean thermal energy conversion (OC-OTEC) systems.
Abstract: The results of the study of the optimum thermo-fluid dynamic design concept are presented for turbine units operating within the open-cycle ocean thermal energy conversion (OC-OTEC) systems. The concept is applied to the first OC-OTEC net power producing experiment (NPPE) facility to be installed at Hawaii's natural energy laboratory. Detailed efficiency and performance calculations were performed for the radial turbine design concept with single and double-inflow arrangements. To complete the study, the calculation results for a single-stage axial steam turbine design are also presented. In contrast to the axial flow design with a relatively low unit efficiency, higher efficiency was achieved for single-inflow turbines. Highest efficiency was calculated for a double-inflow radial design, which opens new perspectives for energy generation from OC-OTEC systems.
Patent•
30 Apr 1990TL;DR: A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime.
Abstract: A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers arranged in a vertical string. The transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings.
TL;DR: In this paper, a field theory is developed analytically which isolates the effects of mesocracks in an added matrix of the thermal resistance, and the concept of mesocack damage in the process of heat transport is further illustrated by considering a three-dimensional and isotropic medium transferring the thermal energy according to Fourier's law of heat conduction.
Patent•
06 Nov 1990
TL;DR: In this paper, a method and apparatus for determining a process parameter of a material in a processing system having two containers is presented, where the material being monitored is disposed in one container and a single thermal energy control device is applied to both containers.
Abstract: A method and apparatus are provided for determining a process parameter of a material in a processing system having two containers. The material being monitored is disposed in one container and a single thermal energy control device is applied to both containers. The heat flux of each container is determined while the single thermal control device is applied to both containers. The process parameter is determined in accordance with the determined heat flux. The thermal energy control device may be a single heating surface for warming the two containers, or a cooling device such as a refrigerator. The process parameter may be the drying rate of the material and the drying rate can be determined during the processing of the material. The drying rate and the percent of drying can be displayed and the thermal energy level of the containers can be controlled according to the determined drying rate. A calibration procedure for calibrating the apparatus is also provided.
TL;DR: In this paper, a microcomputer-based system was developed to automate the operation of the guard heaters and to provide a record of the power outputs of each heater with time, and the experimental results showed that thermal energy from the heaters, as they responded to the combustion front, was transported upward by convection in the annulus.
Patent•
21 Sep 1990
TL;DR: In this article, the thermal energy source is arranged in a hood which is impervious to microwaves and which is formed at the top of the cooking space, and a reflector associated with the thermal-energy source and situated in the transition area between the heating space and the cooking area is connected to a metal grid in an electrically conductive manner and is connected but insulated from the housing.
Abstract: For an electric range featuring combined heating by microwave energy, and/or thermal energy a compact and space-saving construction impervious to microwave energy is provided by the thermal-energy source being arranged in a hood which is impervious to microwaves and which is formed at the top of the cooking space. A reflector associated with the thermal-energy source and situated in the transition area between the heating space and the cooking space is connected to a metal grid in an electrically conductive manner and is connected to but insulated from the housing.
Patent•
17 Aug 1990
TL;DR: In this paper, a thermal energy device for receiving and storing externally applied thermal energy is described, where the thermal energy receiver is adapted to receive the external thermal energy to heat and expand a fluid in the receiver.
Abstract: This invention relates to a thermal energy device for receiving and storing externally applied thermal energy. The thermal energy device includes a thermal energy receiver which is adapted to receive the intermittent externally applied thermal energy to heat and expand a fluid in the thermal energy receiver. A thermal energy store is in fluid communication with the thermal energy receiver to receive and store the heated and expanded fluid received from the thermal energy receiver. The thermal energy store is responsive to the receiving and storing of the heated and expanded fluid such that, as the heated and expanded fluid is received and stored, the thermal energy store delivers more of the fluid to the thermal energy receiver to continue accommodating the intermittent externally applied thermal energy. The thermal energy store is also responsive to dissipation of the intermittent externally applied thermal energy into the fluid such that, as the intermittent externally applied thermal energy is dissipated and the heated and expanded fluid contracts, the thermal energy store returns the fluid to the thermal energy receiver in preparation for subsequent intermittent externally applied thermal energy.