Carl E. Nielsen

Solar ponds for space heating

Solar ponds are shallow bodies of water in which an artificially maintained salt concentration gradient prevents convection. They combine heat collection with long-term storage and can provide sufficient heat for the entire year. We consider the absorption of radiation as it passes through the water, and we derive equations for the resulting temperature range of the pond during year round operation, taking into account the heat that can be stored in the ground underneath the pond. Assuming a heating demand of 25000 Btu/degree day (Fahrenheit), characteristic of a 2000 ft2 house with fair insulation, and using records of the U.S. Weather Bureau, we carry out detailed calculations for several different locations and climates. We find that solar ponds can supply adequate heating, even in regions near the arctic circle. In midlatitudes the pond should be, roughly speaking, comparable in surface area and volume to the space it is to heat. Under some circumstances, the most economical system will employ a heat pump in conjunction with the solar pond. Cost estimates based on present technology and construction methods indicate that solar ponds may be competitive with conventional heating.

Phase Space Hydrodynamics of Equivalent Nonlinear Systems: Experimental and Computational Observations

The one‐dimensional Vlasov equation describes the behavior of an incompressible self‐interacting classical fluid which moves in the (q, p) phase plane. This type of phase fluid occurs in many physical problems and its hydrodynamic properties can be examined from a general point of view. A characteristic feature with initially unstable spatially homogeneous configurations is the development of stable nonlinear phase structures. Such examples occur as the result of the gravitational Jeans instability, or the two‐stream and negative‐mass instabilities of charged‐particle beams. These structures can be related to one another by extending a duality principle due to Dory. The stable cavities in phase space which have been observed in numerical calculations on the two‐stream instability are compared with stable proton clusters which develop from the negative‐mass instability in the mirror experiment DCX‐1.

Dependence of ground heat loss upon solar pond size and perimeter insulation: calculated and experimental results

Abstract Ground heat losses from solar ponds are modelled numerically for various perimeter insulation strategies and several solar pond sizes. The numerical simulations are steady state calculations of heat loss from a circular or square pond to a heat sink at the outer boundaries of an earth volume that surrounds the pond on the bottom and sides. Simulation results indicate that insulation on top of the ground around the pond perimeter is rather ineffective in reducing heat loss, and that uninsulated sloping side walls are slightly more effective than insulated vertical side walls, except for very small ponds. The numerical results are used to derive coefficients for a semi-empirical equation describing ground heat loss as a function of pond area, pond perimeter and insulation strategy. Experimental results for ground heat loss and energy balance in the 400 m 2 solar pond at the Ohio State University are reported. Analysis of this data, along with data on solar energy input, heat gain by the pond, heat loss through the gradient zone, and heat extraction from the pond yields a good energy balance. Numerical simulation of ground heat loss from this pond shows good agreement with the results obtained from pond measurements. Loss turns out to be large because of unexpectedly high values of earth thermal conductivity in the region.

A Continuously Sensitive Cloud Chamber

A particularly simple cloud chamber is described that is continuously sensitive to ion tracks. The chamber operates on the principle of vapor diffusion from a hot to a cold surface. The sensitive region is a shallow horizontal layer near the cold surface. The chamber has been placed in a magnetic field and curved tracks of β‐particles from a radioactive source have been photographed. Pictures of such electron tracks are shown.

DIFFUSION CLOUD CHAMBERS

Three forms of diffusion cloud chamber are described. Diagrams indicate their construction, and their operation is discussed. The direction of diffusion may be upward or downward. Various alcohols and water‐alcohol mixtures may be used. A stable diffusion cloud chamber giving tracks of the quality shown in the typical photographs is simple to construct and operate. The sensitive volume, while necessarily in the form of a horizontal region shallower than the chamber itself, can be made to include most of the chamber volume.

CONDITIONS FOR ABSOLUTE STABILITY OF SALT GRADIENT SOLAR PONDS

Salt-gradient-stabilized solar ponds normally consist of three zones, a convective surface layer, a nonconvective gradient zone, and a second convective layer at the bottom. The behavior of the convective-nonconvective zone boundaries determines the durability in thickness of the gradient zone and hence the reliability of the pond. Observations presented indicate that for any given convective zone temperatures and salinities there exists an absolutely stable gradient zone of some equilibrium thickness. These observations are discussed in terms of a qualitative description of the processes determining boundary position.

Steady-state analysis of the rising solar pond

Abstract The rising solar pond is a configuration in which brine is injected into the pond so as to give all or part of the gradient an upward velocity. This injection alters the salinity profile, steepening it adjacent to the gradient zone upper boundary and thus helping to minimize gradient erosion there. This paper presents analytic expressions for the steady-state salinity profiles in a rising pond, calculated as a function of injection and pond parameters for a constant solutal diffusivity, and also for a temperature-dependent diffusivity. Salinity profiles for various cases are related to specified temperature profiles to determine stability within the gradient zone. Injection into the gradient near the upper boundary is shown to provide the needed increase of boundary gradient with minimal reduction of the margin of safety for internal stability. Suggestions are given for practical implementation of the rising pond concept.

Electrostatic bounce modes in mirror plasmas

Bounce modes are plasma waves which result from the coherent bounce motion of trapped particles. Such modes can occur in mirror devices when the relative spread in electron bounce frequencies is small. When electron bounce modes have perpendicular wavelengths comparable to typical ion gyroradii and frequencies near the ion gyrofrequency or some harmonic, they couple effectively with the ions and can be destabilized by a loss‐cone ion distribution. A one‐dimensional integral dispersion equation for electron bounce modes in a mirror plasma is derived and solved numerically for the wave eigenfrequencies. Predicted threshold densities for bounce mode instabilities in the Baseball I and Baseball II devices are compared with experimental values. Good agreement is found for Baseball II, but in Baseball I the predicted thresholds are consistently below observed values.

Scattering of Light from Small Drops

Curves are given for the angular distribution of light scattered from drops of radius 1.4×10−3 cm and 4.8×10−4 cm for angles from 28° to 147°. The distribution is more nearly symmetrical than had been speculated and depends strongly on the drop size. The intensity of the scattered light was measured with a phototube circuit and galvanometer. The drops were produced in a downward diffusion chamber.

MEASUREMENT OF HEAT TRANSFER THROUGH EARTH IN SITU

ABSTRACT We report measurements of heat transfer through earth in situ , avoiding the disturbance of soil properties inherent in sampling. Data were taken using a heat source with thermocouples to measure the temperature response of the earth after the source was turned on. Diffusivity and heat capacity are found by fitting a universal solution of the heat conduction equation to the experimental points. The solution is written in a form allowing separate independent evaluation of the two thermal parameters, avoiding need for simultaneous two parameter fitting. An experimental arrangement insensitive to environment thermal perturbations is described, and results obtained are presented.