Showing papers on "Thermal energy published in 2003"

Simplified thermal lattice Boltzmann model for incompressible thermal flows

Abstract: Considering the fact that the compression work done by the pressure and the viscous heat dissipation can be neglected for the incompressible flow, and its relationship with the gradient term in the evolution equation for the temperature in the thermal energy distribution model, a simplified thermal energy distribution model is proposed. This thermal model does not have any gradient term and is much easier to be implemented. This model is validated by the numerical simulation of the natural convection in a square cavity at a wide range of Rayleigh numbers. Numerical experiments showed that the simplified thermal model can keep the same order of accuracy as the thermal energy distribution model, but it requires much less computational effort.

Microwave-Assisted Chemical Reactions

Abstract: This article reviews the state of the art of microwave-assisted reactions and the influence of microwaves on mass and heat transfer. The heating behavior of representative test reactions and single substances is compared for heating with microwaves and thermal energy. Similarities and differences between convective heating and dielectric irradiation methods are discussed with regard to the yield, the selectivity, and the enantiomeric purity of the reaction products. Furthermore, prevailing problems related to the scale-up of microwave-assisted reactions are discussed considering the energy absorption of the substances and mixtures to be heated, and their dependence on the energy consumption and the amount of substance.

Thermal management system and method for electronics system

Abstract: A thermal energy management system is provided having a heat spreading device that is operatively engaged with at least one semiconductor chip and a thermal bus operatively engaged with the heat spreading device so as to transport thermal energy from the heat spreading device to a heat sink. The heat spreading device includes a heat pipe and the thermal bus includes a loop thermosyphon. A second thermal bus may be operatively engaged with the first thermal bus so as to transport thermal energy from the first thermal bus to a heat sink. The second thermal bus may also include a loop thermosyphon. A method of managing thermal energy in an electronic system is also provided that includes spreading thermal energy generated by one or more devices over a surface that is relatively larger than the devices, thermally coupling an evaporator portion of a loop thermosyphon to the surface, and thermally coupling a condensing portion of the loop thermosyphon to a thermal energy sink, e.g., a second loop thermosyphon, convection fin, or cold plate.

Internal heat integration – the key to an energy-conserving distillation column

Abstract: This paper illustrates the thermal energy conservation potential of the so-called heat integrated distillation column (HIDiC), which combines advantages of direct vapour recompression and diabatic operation at half of the normal column height. In a typical close boiling mixture separation, compared with a column utilising the usual vapour recompression scheme, HIDiC halved the consumption of exergy at approximately the same capital cost, indicating a strikingly short pay-off time. The complexities of integrating the heat transfer equipment in the stripping section with proven gas/liquid contacting devices, which may work adversely to practical implementation of HIDiC concept, are also addressed.

Systems and methods for generating electrical power from solar energy

Abstract: Systems and methods capable of producing electrical power from solar energy through the use of air cycles without fossil fuel combustion. The system includes a solar receiver, a generator, a compressor, and an expander. The expander is coupled to the generator to drive the generator and coupled to the compressor to drive the compressor. The system uses solar generated heat from the solar receiver to heat compressed air from the compressor. The solar generated heat can be directly transferred from the solar receiver to the compressed air as the compressed air flows through receiver tubes of the solar receiver, or the solar receiver can transfer the solar generated heat to a liquid metal, with the liquid metal transferring thermal energy to the compressed air. The expander receives and expands the heated compressed air to drive the generator to produce electricity, and to drive the compressor to compress air.

Thermal bus for electronics systems

Abstract: A thermal management system for an electronic device is provided a first thermal energy transfer assembly that is thermally coupled between a heat generating structure located on a circuit card and a first thermal interface surface that is spaced away from the heat generating structure. A second thermal energy transfer assembly includes a second thermal interface surface which is arranged in confronting relation to the first thermal interface surface. A clamping mechanism is arranged to move the second thermal interface surface between (i) a first position that is spaced away from the first thermal interface surface, and (ii) a second position wherein the second thermal interface surface is pressed against the first thermal interface surface so as to allow the busing of thermal energy from the first thermal energy transfer assembly to the second thermal energy transfer assembly by heat transfer from the first thermal interface surface to the second thermal interface surface.

Integrated solar energy roofing construction panel

Abstract: A solar assembly comprising two components: a multi-functional solar collecting apparatus and a mounting embedment integrated with building construction material. The mounting embedment component is affixed to a building frame structure using standard construction techniques and receives the multi-functional solar collecting apparatus that is secured with fasteners. The multi-functional solar collecting apparatus converts solar energy to electrical energy using a photovoltaic grid mounted on a copper plate that provides even temperature dispersion across the plate and acts as a thermal radiator when the apparatus is used as a radiant cooler; and a plurality of interconnected heat transfer tubes located within the apparatus enclosure disposed on the plane below the copper plate but conductively coupled to the copper plate for converting the solar energy to thermal energy in a fluid disposed within the heat transfer tubes.

A Parametric Study of the Gas Flow Patterns and Drying Performance of Co-current Spray Dryer: Results of a Computational Fluid Dynamics Study

Abstract: A computational fluid dynamic study was carried out to investigate airflow pattern, temperature, and humidity profile at different levels in the drying chamber. Good agreement was obtained with published experimental data. The effects of operating pressure, heat loss from the chamber wall and inlet air conditions on the gas flow pattern, droplet trajectories, and overall dryer performance also were investigated. Results are presented and discussed in terms of the gas velocity, temperature, and humidity profiles within the chambers. The volumetric evaporation values, heat transfer intensity, and thermal energy consumption per unit evaporation rate were computed and compared for drying of a 42.5% solids solution in a spray chamber 2.215 m in diameter with a cylindrical top section 2.005 m high and a bottom cone 1.725 m high. Wall regions subject to formation of undesirable deposits are also identified.

Optimal energy management of an industrial consumer in liberalized markets

Abstract: This paper presents an optimization model for mid-term management of a thermal and electricity supply system of an industrial consumer under liberalized energy markets. Electricity is supplied from the electric grid or from a gas engine, while thermal energy is satisfied through a boiler or the mentioned gas engine. The objective is to minimize the overall annual energy supply costs in order to make optimal contracting decisions. Mixed-integer linear programming is applied to solve the problem since binary decision and operation variables have been employed. A realistic case is presented to illustrate the model capabilities.

Integrated power and cooling architecture

Abstract: An integrated thermal apparatus for improved electronic device performance has an energy storage device coupled with a thermoelectric management device for managing thermal energy generated by the electronic device. The thermoelectric management device can include a semiconductor thermoelectric device and phase change material, which can be integrated into a foam aluminum structure. The energy storage device can be a nanometallic device. The electrical load electrical efficiency is improved by co-locating it with thermoelectric management device directly on a composite substrate foundation to provide enhanced waste heat conversion to electrical energy. The apparatus manages the thermal and power issues at the substrate level in close proximity to the electrical load and incorporates the needed thermal mass into the support structure by way of a phase change material.

The Tropical Oceanic Energy Budget from the TRMM Perspective. Part I: Algorithm and Uncertainties

Abstract: The earth's weather and climate is driven by the meridional transport of energy required to establish a global balance between incoming energy from the sun and outgoing thermal energy emitted by the atmosphere and surface. Clouds and precipitation play an integral role in the exchange of these sources of energy between the surface, atmosphere, and space—enhancing reflection of solar radiation to space, trapping thermal emission from the surface, and providing a mechanism for the direct transfer of energy to the atmosphere through the release of latent heat in precipitation. This paper introduces a new multisensor algorithm for extracting longwave, shortwave, and latent heat fluxes over oceans from the sensors aboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The technique synthesizes complementary information from distinct retrievals of high and low clouds and precipitation from the TRMM Microwave Imager (TMI) and Visible and Infrared Scanner (VIRS) instruments to initialize broadb...

The Determination of the Total Injected Power in Solar Flare Electrons

Abstract: We here review the procedure by which the injected power in bremsstrahlung-producing electrons is determined from the hard X-ray spectra that they produce. In particular, we note that low-energy photons are produced in large part by electrons with energies that do not greatly exceed the thermal energy of the target with which they interact, so that the commonly used assumption of cold-target energy loss is not applicable over the entire energy range. We show that this significantly reduces the inferred energy content of the injected electron distribution and even makes the oft-dwelt-upon concept of a lower cutoff energy in the injected electron spectrum moot. Convenient formulae are provided for the total power in the injected electrons.

Tunneling-effect energy converters

Abstract: Tunneling-effect converters of thermal energy to electricity with an emitter and a collector separated from each by a distance that is comparable to atomic dimensions and where tunneling effect plays an important role in the charge movement from the emitter to the collector across the gap separating such emitter and collector. At least one of the emitter and collector structures includes a flexible structure. Tunneling-effect converters include devices that convert thermal energy to electrical energy and devices that provide refrigeration when electric power is supplied to such devices.

Method and apparatus for absorbing thermal energy

Abstract: An apparatus for absorbing thermal energy has an electronic component, a support structure for the electronic component having a first set of surfaces defining an interior volume containing a plurality of secondary surfaces, and a thermal energy absorbing material integrated within the interior volume, in contact with at least a portion of the secondary surfaces to form a composite structure The thermal energy absorbing material is in operative thermal communication with the electronic component such that at least a portion of the thermal energy generated by the electronic component flows, via the support structure, into the thermal energy absorbing material A method for controlling a temperature of an electronic component mounts an electronic component on a support structure in thermal communication with a thermal energy absorbing material integrated into an interior volume of the support structure At least a portion of a thermal load from the electronic component is transported to the thermal energy absorbing material, and the portion of the thermal load is absorbed with the thermal energy absorbing material while undergoing an endothermic reaction during a phase change of the material, such that a temperature of the electronic component is maintained below a mounting surface temperature

A Numerical Study of Heat Transfer Mechanisms in Gas–Solids Flows Through Pipes Using a Coupled CFD and DEM Model

Abstract: A two dimensional numerical model has been developed to simulate heat transfer in gas–solids flows through pipes, in which the gas phase is modelled as a continuum using the Computational Fluid Dynamics (CFD) approach and the solids phase is modelled by the Discrete Element Method (DEM). This allows interactions between gas, particles, and pipe wall to be accounted at the scale of individual particles and convective and conductive heat transfers to be calculated using local gas and solids parameters. The predicted changes to the flow structures and the various heat transfer mechanisms due to the presence of particles were analyzed and compared with other workers' findings. This study has quantitatively demonstrated the crucial effect of particle transverse motion on heat transfers due firstly to the thermal energy transport by rebounding particles and secondly to the modification of the fluid thermal boundary layer characteristics.

Engine for converting thermal energy to stored energy

Abstract: The engine for converting thermal energy to stored fluid energy includes expansion cylinders (61a-f) with eypansion chambers (62a-f) and flexible membranes (63a-f). Heating and cooling of working fluid inside the cylinders (61a-f) is carried out by fluid supply lines (73, 71) communicating with external heat resources and sinks. Pressure accumulator (66a) is adapted to store a pressurised fluid (64a-f), such as hydraulic oil, from the individual cyliners (61a-f). In use, this pressurised fluid is delivered at an elevated and above a minimum threshold pressure level, irrespective of the irregularities of the movement of the expansion cylinders (61a-f).

Design tool for the thermal energy potential of asphalt pavements

Abstract: This paper describes the development of a design tool for the calculation of the thermal energy potential of a so-called asphalt collector. Two types of numerical models have been developed and validated against experimental results from a full-scale test-site. The validation showed to be a tedious procedure due to the complexity of the full-scale testing of this type of systems. Nevertheless, the models are found to be applicable for performing design studies with. Example results presented in the paper indicate that the thermal energy potential of an asphalt collector is lower than that of a normal solar hot water system. The quality of the energy is also less. However, further advantages of the use of an asphalt collector are found in the reduced maintenance of the road and the avoidance of slippery roads in winter time. The latter is also an example of the heat exchanger capabilities of the asphalt collector.

Evaluation of Energy, Environmental, and Economic Characteristics of Fuel Cell Combined Heat and Power Systems for Residential Applications

Abstract: Residential combined heat and power (CHP) systems using fuel cell technology can provide both electricity and heat and can substantially reduce the energy and environmental impact associated with residential applications. The energy, environmental, and economic characteristics of fuel cell CHP systems are investigated for single-family residential applications. Hourly energy use profiles for electricity and thermal energy are determined for typical residential applications. A mathematical model of a residential fuel cell based CHP system is developed. The CHP system incorporates a fuel cell system to supply electricity and thermal energy, a vapor compression heat pump to provide cooling in the summer and heating in the winter, and a thermal storage tank to help match the available thermal energy to the thermal energy needs. The performance of the system is evaluated for different climates. Results from the study include an evaluation of the major design parameters of the system, load duration curves, an evaluation of the effect of climate on energy use characteristics, an assessment of the reduction in emissions, and a comparison of the life cycle cost of the fuel cell based CHP system to the life cycle costs of conventional residential energy systems. The results suggest that the fuel cell CHP system provides substantial energy and environmental benefits but that the cost of the fuel cell sub-system must be reduced to roughly $500/kWe before the system can be economically justified.

Confinement and bursty transport in a flux-driven convection model with sheared flows

Abstract: Transport and confinement within the resistive-g paradigm are investigated by means of two-dimensional numerical simulations. The system is driven by a constant incoming heat flux at the inner radial boundary. Different confinement and transport states are identified, involving self-sustained sheared poloidal flows. At the onset of turbulent convection the probability distribution functions of pressure and radial velocity fluctuations measured in the centre of the plasma layer have a nearly Gaussian form. Further increasing the heat flux drive these distributions become increasingly non-Gaussian, developing exponential tails. This large-scale intermittency is ascribed to the presence of bursting in the domain averaged convective transport and the fluctuation energy integrals. The quasi-periodic bursts are separated by shear-dominated quiescent periods in which the mean flow energy decreases and the confined heat increases on diffusive timescales. The time-averaged thermal energy confined within the plasma layer shows a power law dependence and significant increase with the injected power over the range of turbulent convection investigated.