Showing papers on "Thermal energy published in 1969"

Thermal stratification in lakes: Analytical and laboratory studies

Abstract: Theories are developed for the time dependent vertical temperature distribution in a deep lake during the yearly cycle of solar heating and cooling. A portion of the incoming solar radiation is assumed to be absorbed at the water surface, whereas the remainder is absorbed exponentially beneath the surface. Heat is also conducted downward by molecular diffusion. A heat flux balance at the water surface, which accounts for back radiation and evaporative heat loss, is formulated as a boundary condition. The linear, second-order heat transfer equation is solved by superposition of solutions for the surface absorbed radiation and the internally absorbed radiation. Analytical solutions are given for three different assumptions regarding the time dependence of the incoming radiation and the surface heat losses. At certain times, the resulting temperature and density distribution in the epilimnion are unstable. Under these conditions convective mixing and turbulent diffusion are accounted for by generating a surface mixed layer of uniform temperature. The depth of the surface mixed layer is determined by a thermal energy balance. The theory shows good agreement with field observations of temperature distributions in Lake Tahoe. Experiments are performed using artificial insolation (mercury vapor and infrared lamps) on a laboratory tank. We conclude that it is possible to simulate the development of thermal stratification under laboratory conditions.

Temperature-controlled discrete sample analyzer

Abstract: There is disclosed an apparatus for controlling the temperature of discrete sample containers in analytical instrumentation. A conveyor containing discrete samples to be analyzed is located in a subcompartment within a larger enclosure. A fan is mounted in a first opening in the subcompartment to move air from the large enclosure into the subcompartment. A second opening in which a thermal energy transfer element is mounted allows the passage of the air over the thermal energy transfer element back into the larger enclosure. A temperature sensor contacts a sample container being measured to provide a control signal which is applied to a proportionally controlled power supply connected to the thermal energy transfer element.

Thermally cascaded thermoelectric generator

Abstract: A THERMALL CASCADED THERMOELECTRIC GENERATOR IS DISCLOSED. THE GNENERATOR INCLUDES A FIRST STAGE CONTAINING HIGHTEMPERATURE THERMOELECTRIC ELEMENTS AND A SECOND STAGE CONTAINING LOWER TEMPERATURE THERMOELECTRIC ELEMENTS. THE STAGES ARE CONNECTED IN THERMAL SERIES BY MEANS OF AN ELONGATED HEAT TRANSFER PIPE CONTAINING A LIQUID METAL AND A WICK. A PORTION OF THE HEAT RADIATED TO THE FIRST STAGE FROM A HIGH-TEMPERATURE RADIOISOTOPE SOURCE IS CONVERTED TO ELECTRICITY. THE HEAT REJECTED BY THE FIRST STAGE IS CONDUCTED TO THE HEAT PIPE AND ABSORBED BY THE LIQUID METAL AS LATENT HEAT OF VAPORIZATION. THE VAPOR RISED TO THE SECOND STAGE AND CONDENSES TO GIVE UP LATENT HEAT OF CONDENSATION WHICH IS TRANSFERRED TO THE SECOND STAGE AND IS CONVERTED TO ELECTRICITY THEREIN. THE CONDENSED LIQUID RETURNS ON THE WICK TO THE VICINITY OF THE FIRST STAGE.

Replacement Free Energy in the Thermodynamics of Small Systems

Abstract: The object of this study is to present an analysis of the origin and calculation of the replacement free energy in the thermodynamics of small systems. An exact expression is obtained for the replacement free energy of a one‐dimensional “crystal” with free ends.

Gaseous laser cooling system

Abstract: A system for the removal of thermal energy from nonmetallic material which forms the boundary of a gaseous laser.

Apparatus for converting acoustic energy into a visible image

Abstract: Apparatus for converting information in the acoustic domain into visible patterns. Acoustic energy is conducted through a wavetransmitting medium to impinge on an absorptive layer which converts the acoustic energy into thermal energy. The thermal energy is transmitted to a layer of a suitable thermochromic substance such as cholesteric liquid crystals, so that the thermochromic layer undergoes a characteristic color change corresponding to the intensity and the location of the wave of vibratory energy.

Method of and means for regulating thermal energy transfer through a heat pipe

Abstract: A method of and means for regulating the rate of thermal energy transfer through a heat pipe containing a heat transfer fluid in its liquid and vapor phases by regulating the pressure at the liquid-vapor interface. A regulated thermal generator embodying thermally regulated heat pipe means for transmitting thermal energy at a controlled rate to a heat sink or thermal load.

Device for transporting thermal energy from a lower to higher temperature level

Abstract: A method and apparatus operating with normal and superfluid 4He at temperatures below the -point of liquid helium, for cooling wherein a first superleak through which passes only superfluid 4He, produces a fountain-pump effect which is applied to a second superleak which provides cooling an object within a second enclosure.

Rotary heat engine

Abstract: A ROTARY HEAT ENGINE FOR EFFICIENTLY GAS THERMAL ENERGY TO MECHANICAL ENERGY COMPRISING A HOLLOW GENERALLY CYLINDRICAL HOUSING, A HEAD SECURED AT EACH END, ONE OF THE HEADS HAVING GAS INTAKE MEANS AND THE OTHER OF THE HEADS HAVING GAS EXHAUST MEANS, BEARINGS MOUNTED IN THE HEADS SUPPORTING A SHAFT ON WHICH IS MOUNTED A ROTOR. THE ROTOR HAS A PLURALITY OF INTERNAL SPIRALLY DISPOSED FLUID OR GAS CHAMBERS EACH OF WHICH HAS THE SAME HAND AND PITCH AND EACH OF WHICH DEFINES A SUCCESSION OF COVERGING, DIVERGING AND CONSTANT AREA SECTIONS SO THAT FLUID INTRODUCED UNDER PRESSURE TO THE CHAMBERS RELEASES ITS HEAT ENERGY WHICH IS CONVERTED TO MECHANICAL ROTATIONAL SHAFT POWER.

Evaporation of High-Velocity Particles in Free-Molecule Flow

Abstract: An effective heat-transfer coefficient X has been determined for microscopic iron particles traversing rarefied target gases at velocities between 25 and 40 km/sec. X is defined as the ratio of the increase in internal energy of the particles to the energy incident on the surface of the particles from the colliding gas molecules. The particles were completely vaporized in the target gas and the increase in internal energy was taken as the total vaporization energy. The total energy incident on the particle surface from the colliding gas molecules was determined experimentally. For an air target gas, X decreased more or less linearly from a value of 0.68 d= 0.07 at 25 km/sec to a value of 0.27 ± 0.07 at 4Q km/sec. Results for oxygen and argon target gases were similar. other than completely elastic molecule-surface collisions, the passage of a high-velocity object through a rarefied gas results in an increase in the internal energy of the object. The rate of energy input is a function of both the velocity and the gas density. If the rate of energy input is small, radiation cooling may be sufficient to establish thermal equilibrium. For very high rates, however, evaporative cooling may be required. Obviously evaporation reduces the mass of the object and, under certain conditions, it may be completely consumed in the process. This behavior is typical of high-velocity photographic and visual meteors as well as many man-made objects that re-enter the earth's atmosphere. The objective of the experiment discussed in this paper was to determine the efficiency with which the kinetic energy of molecules impinging on the surface of high-velocity particles was converted into internal energy of the particles. The experiment was accomplished by injecting high-velocity (25 < v < 40 km/sec) microscopic iron particles of measured velocity and mass into target gases of known density. The gas pressure was such that free-molecule flow conditions prevailed and, in all cases, the particles were completely vaporized within the target gas volume. Both the total energy required to vaporize the particles and the total energy flux incident on them from the colliding gas molecules were determined. The ratio of these two quantities yields what may be called an effective heat-transfer coefficient A which, in turn, is related to details of the molecule-surface interactions. Although the experiment was conducted with microscopic particles under idealized conditions, the results are quite fundamental in nature and may be applied to problems involving much more massive objects such as meteors or other objects entering the earth's atmosphere. 2. Experimental Approach

Model for the Shock Hugoniot for Condensed Media

Abstract: A simple model is presented for the Hugoniot energy change in condensed media subjected to a strong shock. Approximating the structure of the liquid by a cell model and assuming an n − 6 pair potential, an expression is obtained for the configurational portion of the internal energy change. Changes in thermal energy and the effects of relaxation processes are ignored since the final state involved in the energy balance is selected to coincide with the state of molecules just after they have attained the particle velocity, but before significant translational relaxation has taken place. The Hugoniot energy change is then approximated by the change in configurational energy. The derived Hugoniot fits available data for five simple liquids within experimental error when a consistent and realistic value of n is chosen. A single value of 8.5 is found to produce good agreement between experimental and predicted results for argon at initial temperatures of 86° and 148°. Values of n for argon and nitrogen agree c...