Showing papers on "Thermal reservoir published in 1991"

Reservoir simulation of cyclic steam stimulation in the Cold Lake oil sands

Abstract: Steam injectivity during cyclic steam stimulation (CSS) as Cold Lake can be achieved only by injecting at pressures high enough to fail the formation mechanically. The reservoir also exhibits water/oil relative permeability hysteresis. This paper describes enhancements made to a thermal reservoir simulator to incorporate these Cold Lake physics. The geomechanical model allows both localized fracturing and global reservoir deformation (dilation and history-dependent recompaction). This representation allows the simulator to match injection and production pressures that are otherwise difficult to reproduce. The history-dependent relative permeability hysteresis model calculates gridlock relative permeabilities that always lie on or between input imbibition and drainage bounding curves. The model makes it possible to use laboratory-derived relative permeabilities in a simulation and still matchmatch field WOR's.

Properties of a macroscopic system as a thermal bath

Abstract: A macroscopic system acting as a heat reservoir affords a simplified description in terms of a collection of independent modes. Although in most cases this model is unable to account for the behavior of the macroscopic system itself, it provides a consistent desciption of the macroscopic degrees of freedom acting as a dissipation mechanism for a microscopic system. This is found to be a consequence of the statistical properties of bath quantities relevant to the dynamics of the microscopic system. Furthermore, these properties ensure that the unphysical features of the independent bath model do not affect its performance as a heat reservoir.

Cordless electric hair-dryer

Abstract: A cordless electric hair dryer and stand are provided in which the portable hair dryer unit has a rechargeable battery and a thermal heat reservoir. The fan blows ambient air over the thermal reservoir in heat exchange relationship to expel hot air from the dryer when in use. The stand has an electrical circuit inductivley coupled through a coil in the base of the stand to a coil in the rear of the housing of the dryer which provides power to charge the rechargeable battery in the handle of the dryer and to heat the thermal storage medium in the dryer. The heating is accomplished by resistors mounted in heat exchange relationship with the thermal reservoir material. The rechargeable battery is used only to run the fan during drying operation of the portable unit.

Thermal budget of multicomponent porous ices

Abstract: A relation for the temperature evolution of multicomponent porous ices is derived from the energy equation of multicomponent systems. It is demonstrated that the predominant energy transfer mechanisms can be incorporated into an effective thermal conductivity (λeƒƒ), which is strongly temperature dependent, and that the heat conduction equation can be written in a Fourier type form. The vapor of volatile ices significantly contributes to λeƒƒ by the transfer of latent heat of sublimation but otherwise hardly affects the energy balance. The general results are applied to porous water ice, porous H2O–CO2 ice and porous H2O–CO ice. In all cases it is found that the major part of the deposited energy per unit volume is consumed for heating of the ice. Depending on the material parameters and temperature, energy is transferred mainly by solid state conduction or by the transport of latent heat due to sublimation-condensation processes.

Quantum Markovian master equation for a system of identical particles interacting with a heat reservoir

Abstract: The author's earlier quantum kinetic theory of systems in thermal contact with a heat reservoir is now applied to systems of identical particles. A statistical description of such systems is provided by a hierarchy of many-particle density matrices for which a system of “linked” equations is obtained. The quantum Markovian master equation is derived, which makes it possible to determine the single-particle density matrix. Consideration is given to three examples of the application area of this equation, viz. the latter is described for three cases in which particles experience (1) random walks in a crystal lattice, (2) migration in a homogeneous isotropic continuum, (3) thermoactivated transitions between quantum states. In each of these cases the density matrix is found to describe the stationary state of a system of identical particles.

On the thermodynamics of a superconducting ring interrupted by a weak superconducting junction. III, Thermodynamic fluctuations

Abstract: A superconducting ring interrupted by a weak Josephson junction can have two metastable magnetic flux states separated by a potential energy barrier in case an external magnetic field of appropriate strength is applied. In a previous article, part I, the thermodynamic Gibbs surface of this system was constructed together with the relevant contribution to the entropy being the negative of the corresponding partial derivative of the Gibbs function, while in part II the magnetic availability of this system, being the minimum work an external source must perform to bring the small system reversibly from a state of equilibrium with the surroundings to a given non-equilibrium state, was constructed. Calculations were presented of relevance in intepreting thermodynamic fluctuation phenomena of the total embraced flux which are determined by the potential magnetic availability of the system with respect to the surroundings fixed by the temperature of the heat reservoir and the external magnetic field. In the present article (part III) it is argued that the probability of the equilibrium steady state solution is determined by the total dynamic availability of the system, containing contributions both from the potential availability and from the kinetic energy. The total dynamic availability is a function of the fluctuating parameters: the embraced flux, the flux velocity and the local temperature of the junction. In order to find the distribution in the magnetic flux alone the other variables, the flux velocity and the temperature are integrated out by numerical methods.

Room cooling hot water supplying apparatus using night power

Abstract: PURPOSE:To effectively use night power by driving a heat pump by night power in a room cooling season, cooling heating liquid medium in a heat reservoir, heating water in a hot water supply tank by the heat pumped from the liquid medium, and reserving the heat. CONSTITUTION:A heat pump 3 to be operated by night power, a heat exchanger 6 connected to a heat reservoir 1 to circulate heating liquid medium 8 in the reservoir 1 as a cold source, and a hot water supplying unit 7 for feeding hot water 9 from a hot water tank 2 are at least provided. The exchanger 6 installed in a housing is connected to the reservoir 1, and the liquid 8 is circulated between the reservoir 1 and the exchanger 6. That is, the liquid 8 in the reservoir 1 is heat exchanged with the air in a room 23. The exchanger 6 is composed, for example, of a heat exchanging coil 25 in which the liquid 8 supplied from the reservoir 1 is fed, a fan 26 and an accessory facility thereof. A circulation pump 18 is provided at a tube 17 for connecting the exchanger 6 to the reservoir 1, and the medium 8 is circulated between the reservoir 1 and the exchanger 6.

The effect of thermal capacitance and phase change on outside plant enclosures

Abstract: The use of heat storage materials in outside plant (OSP) enclosures to reduce internal temperatures is examined. A simple thermal analog model is used to represent the heat flow in an enclosure that contains a thin envelope of phase change material (PCM). From this model, two sets of equations are developed for the internal and the PCM temperatures. The first set defines temperatures when the PCM is in a sensible-heat-storage mode, in which it acts as a simple thermal capacitor, and the second set defines temperatures when the PCM is in its latent-heat-storage mode. Exact solutions are obtained for both modes when the daily outside temperature and solar load are modeled by sinusoidal functions. >

``Heat reservoir'' boundary condition as limiting relation

Abstract: Asymptotic analysis provides a basis for deriving the “heat reservoir” boundary condition when a solid surface is in contact with a region of vigorous liquid motion; it simplifies the formulation of multilayer heat and mass transfer problems under definite conditions. An effective heat conduction equation resembling Taylor's dispersion equation is obtained for the heat transfer in the liquid.

Heat reservoir and thermal accumulation device

Abstract: PURPOSE:To provide a less-expensive and compact-sized device and improve an efficiency of regenerating thermal accumulated heat and installing and maintenance adaptability by a method wherein cement plate-like molded members arranged with both side surfaces being in parallel with a direction of air flow or plate-like molded members having a cement applied as a coupling material and a plurality of heat reservoirs composed of a moisture-proof layer arranged at the surface thereof are provided within a chamber of a heat exchanging passage. CONSTITUTION:A thermal accumulation device 12 is provided with a chamber 51 formed in a closed state with a thermal insulation material. Both sides are formed as uniform pressure chambers 52a and 52b and then a heat reservoir block 53 is stored in a remained space. A wall part forming one uniform pressure chamber 52a is provided with an opening 54 connected to a main duct, and another wall constituting the other uniform pressure chamber 52b is provided with an opening connected to an auxiliary duct. The heat reservoir block 53 is provided with a main body 56 of the heat reservoir composed of a plate-like molded member 55 or another plate-like molded member formed with a cement applied as a coupling member, and a moisture-proof layer 57 at this surface. Several layers are overlapped with the orientations of the projections 58 and 58 being overlapped in the same direction and stored in the chamber 51 so as to constitute an air passage 59.

Heat recovery and transportation from thermal plants

Abstract: A process for heat recovery from a thermal plant and transportation over a large distance is presented and discussed. Heat is carried in the vapour phase of a working fluid at the ambient temperature without thermal losses. The performance of the process compares favourably, even for distances of about 100 km, with the local use of a heat pump at the site where the thermal energy is to be consumed. Water can be used as a suitable alternative to freons in such a process of heat transportation.

Latent heat using heat recovery system

Abstract: PURPOSE: To obtain an efficient heat recovery system using heat medium changing in phase. CONSTITUTION: Capsuled heat medium CP varying in phase in a temperature range between a heat source 1 and a heat reservoir 2 is continuously circulated between the source 1 and the reservoir 2, the medium is brought into direct contact with fluids to be heat exchanged. Heat transporting and accumulating functions are incorporated in the medium so that heat stored in the reservoir 2 can be used for a heat pump 100. Since the heat exchange and accumulation are executed while directly continuously circulating the medium using its latent heat, a high heat recovery system in which a large capacity of heat can be recovered in a small size even at a low temperature difference with high reliability is obtained. COPYRIGHT: (C)1993,JPO&Japio

The Second Law of Thermodynamics

Abstract: The first law of thermodynamics was developed in Chapter 4 from a study of the effects of adiabatic work on the state of a system. This law introduces the concept of internal energy (a non-primitive state function) and imposes certain limitations on the changes that can occur in a system under given constraints. For example, the first law shows that when two isolated systems, A and B, are brought into thermal contact, the heat absorbed by A is equal in magnitude but opposite in sign to that absorbed by B. However, the first law is unable to allocate the signs to these two quantities of heat. This is done by the second law, one statement of which has been discussed in Section 3.1. The second law indicates that when two isolated systems are placed in thermal contact, the temperature of the hotter one falls and that of the colder one rises, provided that phase changes do not occur in either system.

Relaxation of nonlinear oscillator

Abstract: i. The problem of the distribution function of a system with a finite number of levels that interacts with a thermal reservoir and with an external harmonic force arises in the solution of many problems in physics. As examples, we can mention systems that consist of atoms or molecules in the field of a laser wave, the particles existing in a solid or gas that play the role of the thermal reservoir. Many studies have been devoted to the solution of such problems [i-ii]. In many studies, the treatment is restricted to twoand threelevel systems (see, for example, [2]). The anharmonic oscillator is often investigated by means of perturbation theory, the correction to the harmonic potential (the anharmonicity parameter) being regarded as a small quantity [3-6]. In [7,8], nonlinearity is taken into account only in the form of a dependence of the oscillator vibration frequency on the level number, ~(n), and the distribution function is found by means of the quasiharmonic approximation, i.e., the solution for a harmonic oscillator with the frequency replaced by the dependence ~(n). These studies do not take into account higher harmonics in the solution, and this is equivalent to taking into account transitions only between neighboring levels. The nondiagonal elements of the density matrix are also not taken into account, so that the original equation for the density matrix reduces to the solution of the system of balance equations for the populations.

Solution of the generalized master equation for an externally driven and environmentally damped two-level system

Abstract: Using the Generalized Master Equation (GME) we investigate the dynamics of a two-level system which is subjected both to the influence of a thermal reservoir and to an external driving field. The coupling with the phonon reservoir is represented by the usual (energy-conserving) linear-displacements interaction, which makes the model exactly solvable in the absence of the external field. The coupling with the external field is treated within the Rotating Wave Approximation (RWA). We obtain an exact formal solution of the GME and we construct a hierarchical class of weak-driving approximations avoiding usual assumption of a weak coupling to the bath. The populational difference is damped in a nontrivial manner: the relaxation is nonexponential with long-time tail behaviour in the asymptotic region. The evolution is analysed as a function of temperature, the strength of the coupling, the strength of the external field and the detuning. Our model is formally identical to the spin-boson model and our approach gives a systematic improvement of the noninteracting-blip approximation.