Showing papers on "Thermal reservoir published in 1969"

Thermal control and power flattening for radioisotopic thermodynamic power system

Abstract: A thermal control device utilizing the heat pipe principle Heat receiving and heat rejecting surfaces are spaced from each other along the length of the heat pipe In a preferred form, a radioisotope fuel capsule is in thermal conducting relationship with the heat receiving surface and a noncondensible gas is mixed with the working fluid of the heat pipe A noncondensible gas automatically expands as the threshold temperature of the system drops to block off more of the heat rejecting surface In other alternate preferred embodiments, a nonvaporizable liquid is utilized in lieu of a noncondensible gas to reduce the area of the heat receiving surface as the threshold temperature of the system drops or a second material is mixed with the working fluid which changes to a solid phase to block the flow of the working fluid between the heat rejecting and heat receiving surfaces as the threshold temperature of the system drops

Apparatus and method for measuring the thermal conductivity of insulating material

Abstract: Apparatus for quickly determining the thermal conductivity of a material over a wide temperature range in a single test. The apparatus comprises a heat sink of metal of known heat capacity, a shell surrounding and spaced away from the metal heat sink providing a space in the shell for placing a sample material, the thermal conductivity of which is to be determined, essentially all around the metal heat sink, means for measuring the temperature of the metal heat sink, and means for measuring the temperature of the shell to thereby determine the temperature difference through the sample.

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.

Fixed temperature, rapid response, high energy heating device

Abstract: A rapid response heating device employing a heat funneling principle combined with minimal thermal resistances for attaining heat fluxes up to 50 kw/ft2 and for maintaining a fixed temperature at the output working surface despite large changes in thermal load. The device is heated with an electric foil heater having its power input regulated by a control device responsive to temperature changes within said device and has a large heat input area as compared with a small heat output area.

Nonlinear Resonance Effects in Multilevel Quantum Systems Weakly Coupled to a Thermal Reservoir

Abstract: Calculations are made to determine the response (power absorbed, magnetization, etc) of a multilevel quantum system under the influence of any number of classically described driving fields (well defined in amplitude and phase) A nonperturbative theory is developed to account for those fields that are in resonance with the system The nonresonant effects, such as virtual energy shifts, are included in the theory We limit ourselves to a discussion of quantum systems that are in weak contact with a thermal reservoir The procedure is the following A projection-operator formalism is developed which separates the density matrix of a system into two parts One part is related to those portions of the driving fields that interact quite strongly with the system The other part is the nonresonant or weakly interacting portion An exact equation of motion, which includes the effects of the nonresonant part, is derived for the strongly interacting part of the density matrix It is then shown that when relaxation can be represented by phenomenological decay constants, a unitary transformation can be found which reduces the equation of motion for the strongly interacting part of the density matrix so that an exact solution is possible This solution is shown to give the major effects of the driving fields and can be used as the zeroth-order solution in a perturbation treatment of the whole density matrix Frequency shifts such as the Bloch-Siegert shift and shifts due to couplings between the levels of interest (resonance levels) and other levels (nonresonance levels) all arise in the same natural way in our treatment Our results in many instances are the extensions of the well-known results for a two-level quantum-mechanical systemm to an $N$-level one, and include resonant multiple quantum effects As an example, a straightforward application of the method is carried out in order to compute the shifts in the resonance frequencies of a four-level system, driven by two oscillating fields connecting three of the levels, due to the counter-rotating components of the driving fields and the presence of the fourth level, which is not coupled to the other levels by the driving fields

A matrix method for heat conduction in multi-layered media

Abstract: A matrix formalism is developed to facilitate computation of temperature distribution in the steady state in the interior of a multi-layered earth. The idealized model consists of homogeneous and isotropic layers of constant (but arbitrary) values of heat production as well as thermal conductivities. The known surface data is continued by this method to define the thermal structure at any desired point of the interior for planar and spherical stratification. Extension of the problem to the unsteady flow conditions has been presented.

Paper stabilization heater

Abstract: Apparatus for the heat stabilization of spectrally sensitized printout paper on a continuous basis having means for forming a latent image on the paper; means for transporting the paper into thermal contact with a passive heat shunt and raising the temperature of the paper a predetermined increment; heat reservoir means in thermal contact with the paper for raising the temperature an additional predetermined increment; heater means for raising the temperature of the paper to that required for stabilization of the image; means for maintaining the stabilization temperature for a predetermined period of time while the strip is in motion; means for returning the heat from the paper to the heat reservoir; and additional means for returning heat to the heat shunt.

Thermal Stresses in a Semi-infinite Body with an Instantaneous Heat Source on Its Surface

Abstract: There is the Green's function or the Neumann's one as the fundamental solution of a ther-moelastic problem for an elastic body whose surface temperature or surface heat flow is given by a function of time and position. Each function for a semi-infinite body with a surface heat source has been introduced. When the body surface is exposed to a medium whose temperature varies throughout the space and with the time, however, the fundamental solution of thermoelasticity, which is the Robin's function, has not been investigated though the solution covers even the Green's and the Neumann's Then the author introduces the Robin's function. In other words, when the surface of the body, which has initially zero temperature, is exposed to a medium with zero temperature, and an instantaneous heat source generates on its surface, the temperature field and thermal stress distributions are analysed. Thereafter the variations of temperature and thermal stresses with time are numarically shown.

The problem of thermal conductivity for a finite rate of heat propagation

Abstract: A solution is given for the problem of heat propagation along semibounded and bounded rods with a constant-power heat source, with and without consideration of the transfer of heat from the side surface for a finite rate of heat propagation.