Showing papers on "Thermal reservoir published in 1974"

Solar heated building

Abstract: A solar heated building of generally hemispherical shape which supports on its surface solar heat collectors. The solar heat collectors are in the shape of spherical sectors and cover an arcuate area defined by the receipt of usable solar heat energy; consideration being given to the diurnal and seasonal positions of the sun. Heat collecting fluid is passed in thermal contact with the solar heat collectors and is in circulation with a heat storage reservoir. Air is passed in thermal contact with the solar heat collector to prevent overheating when the heat collecting fluid is cut off or to provide hot air when the heat storage reservoir is fully heated or when the solar heat collector is warmer than ambient but not hot enough to supply heat to the heat storage reservoir. The solar heat collectors are segregated by the heat collecting fluid circulation system piping into discrete arrays each covering about 15° of azimuth arc and each such array is controlled by one or more valves which admits or blocks heat collecting fluid flow. Each of the solar heat collector arrays and the heat reservoir is provided with a temperature sensor. A temperature comparison device compares the temperature of each of the solar collectors with the temperature of the heat reservoir to automatically open the valves to only such arrays as will supply heat to the heat reservoir. The air circulation system through the solar heat collectors is automatically activated for cooling when the solar heat collectors are not being used for heat storage. When air is passed through the solar heat panels, the heated air may be used to directly provide hot air for space conditioning or other purposes and thereby conserve the stored heat. The dual-mode capability of air-fluid operation enables the system to extract the maximum amount of solar energy for usable purposes.

Core Convection as a Power Source for the Geomagnetic Dynamo-A Thermodynamic Argument

Abstract: The mechanical (or magnetic) energy available in principle from convection in a fluid body with an adiabatic temperature gradient is shown to be related to the convective heat transport by the efficiency of an ideal thermodynamic engine working across the adiabatic temperature difference. The temperature gradient at any level within the core is presumed to take either the adiabatic value or the diffusive gradient corresponding to the heat flux at that level, whichever is less. Then the convective power is calculable in terms of the assumed distribution of heat sources, the values of thermal conductivity K and the thermodynamic Gruneisen ratio, γ. Numerical results are presented for the case of heat sources uniformly distributed through the outer core, with γ=1.15. These indicate that with K=28Wm-1deg-1 (our preferred value) and an inner core temperature of 4000°K the thermodynamic efficiency of core convection rises from zero at a total heat generation Q0=2.5×1012W to 6.4% at Q0=7.5×1012W, but increases only slowly with further heat input. The efficiency is scaled in terms of the ratio K/Q0. The upper limit of plausible convective power in the core is about 7×1011W.

Winter-regime thermal response of heated streams

Abstract: The increase in water temperature in natural streams due to waste heat disposal from thermal power plants leads to extensive ice-free reaches during winter periods. It is shown that the surface heat exchange between water and the atmosphere can be expressed, for most practical purposes, as a linear function of the water temperature. Using this approximation, a closed-form solution of the one-dimensional unsteady convection-diffusion equation is developed to predict temperature distributions in streams and the lengths of ice-free reaches downstream from the thermal discharge sections.

Thermal Stresses Around Circular Inclusion Due to Heat Source and Sink One

Abstract: There have been treated some thermo-elastic problems of a heat source in the steady-state heat condition In this paper, the stress analysis of a circular inclusion between point sources producing heat and absorbing it in an elastic plate is made, under the assumption that all the heat flowing out from the heat source passes through a circular inclusion or near it and flows out from the sink heat source, being always kept under the steady-state heat condition

Consistency of variational approximations in statistical thermodynamics

Abstract: It is shown that a large class of approximations in statistical thermodynamics that are based on the free-energy variational principle for the density operator yield expressions for the macroscopic quantities of the system that are consistent from both the statisticalmechanical and thermodynamical points of view. This corrects some erroneous statements in the literature. In an exact treatment of the statistical mechanics of a system in thermal equilibrium there is complete consistency between the definitions of the macroscopic quantities from the statisticalmechanical point of view and the corresponding ones from the standpoint of phenomenological thermodynamics. This great achievement of statistical mechanics can easily be established within the formulation of statistical therraodynamics„because the exact Hamiltonian of the system is a purely mechanical quantity independent of any thermodynamic parameters, such as temperature, etc. In various unavoidable approximation procedures for the thermal-equilibrium properties of systems, ho~ever, the Hamiltonian is approximated by an effective one that depends on such thermodynamic parameters. In such a case the statistical-thermodynamic consistency mentioned above is brought into question. In fact, it has been stated' that in the weil-known thermal Hartree-Fock approximation" for a system of interacting fermions this consistency is sacrificed. An approximation scheme in statistical thermodynamics that yields results that violate the consistency between the statistical and thermodynamical definitions of various observable quantities is clearly undesirable (at the very least one would have to give a reason for choosing one rather than the other definition}. In the following we shall show that there is a large class of approximations in statistical thermodynamics that are free from this serious drawback. According to the laws of thermodynamics' the complete macroscopic description of a system in thermodynamic equilibrium under certain constraints is provided by the fundamental relation appropriate to the constraints on the system, i.e., by a function of the appropriate independent variables. For example, for a simple, singlecomponent system of volume V in contact with a heat reservoir at temperature T and a particle reservoir at chemical potential p, , the fundamental relation is

Physical applications of multiplicative stochastic processes. II. Derivation of the Bloch equations for magnetic relaxation

Abstract: The multiplicative stochastic process treatment of the time development of the density matrix for a subsystem in contact with a heat reservoir is applied to the specific problem of the relaxation of a nuclear magnetic moment which is interacting with a fluctuating magnetic environment. A model for the fluctuating interaction Hamiltonian, appropriate for the magnetic moment case, is presented, and the Bloch equations for nuclear magnetic relaxation are constructed as a consequence. Agreement with empirical observations is noted.

Thermal Behavior of Multifluid-Saturated Formations Part 2: Effect of Vapor Saturation - Heat Pipe Concept and Apparent Thermal Conductivity

Abstract: When porous systems contain liquids at or near their vapor pressures and saturation tempertures, evaporation- condensation reactions may combine with capillary pressure gradients and greatly enhance the heat transfer capacity of the system. This behavior was simulated by the so-called heat pipe, a mechanism which is capable of transferring heat at rates much higher than those observed by simple conduction. A conceptual model was derived for the theoretical analysis of the heat pipe concepts in porous media. Equations were developed for expressing the heat pipe effect in the form of an additional thermal conductivity as a function of the system's characteristics. The mechanism was illustrated experimentally by testing 4 different rock samples with 2 liquids of different latent heats of vaporization. Results, which were in consistent agreement with the derived theory, showed that vapor saturations resulted in high apparent thermal conductivities for the rock samples that were, in some cases, several times greater than the expected basic value. (16 refs.)