Ronald DiPippo

A high-temperature oscillating-disk viscometer

Abstract The paper describes a new, high-precision, oscillating-disk viscometer in which it is possible to make absolute determinations of the viscosity of gases at atmospheric pressure in a temperature range 20–950°C, approximately. The effect of differential thermal expansion on the spacing between the disk and the fixed plates as well as that of high internal damping in the wire, both of which precluded the use of this method at high temperatures in the past, has been eliminated by making all such parts, including the suspension strand, of fused quartz. This was made possible by a novel method of drawing the strand. Estimates of precision and tests of reproducibility suggest that the measurements are accurate to ±0.1%. Preliminary results on pure nitrogen up to 500°C are presented. Excellent agreement with the most reliable determinations, which are available up to 75°C, is obtained, thus inspiring confidence in the results at higher temperatures.

Geothermal energy Electricity generation and environmental impact

Abstract Geothermal energy is widely used as a reliable source of electricity generation. In 21 countries geothermal plants are in operation and have a combined installed capacity of over 6 000 MW. Technology now permits the utilization of a broad range of resources, from moderate-temperature to hypersaline brines, as well as natural steam with high levels of non-condensable gases. This paper describes geothermal energy conversion systems and the potential environmental impacts associated with geothermal plants. In comparison with alternatives, geothermal plants are among the most environmentally benign. Emissions abatement, water and land-use, and other aspects are discussed, along with the costs for environmental controls.

Sourcebook on the production of electricity from geothermal energy

Twenty separate abstracts were prepared for individual chapters and sections of this book. (MHR)

Geothermal energy as a source of electricity : a worldwide survey of the design and operation of geothermal power plants

An overview of geothermal power generation is presented. A survey of geothermal power plants is given for the following countries: China, El Salvador, Iceland, Italy, Japan, Mexico, New Zealand, Philippines, Turkey, USSR, and USA. A survey of countries planning geothermal power plants is included. (MHR)

Composition dependence of the thermal conductivity of dense gas mixtures

In this paper we present a method for predicting the composition dependence of the thermal conductivity of dense gas mixtures. The method requires the knowledge of the thermal conductivities of the pure component gases at high density, of the zero-density values of the thermal conductivities both of the pure components and of one binary mixture, and of the virial coefficients Bij and their derivatives dBijdT. The Thorne-Enskog hard-sphere theory, after a minor correction for consistency with the Onsager reciprocal relations, is then used as an interpolating formula between the end points. An extension of the method to mixtures of dense polyatomic gases is also provided. For these gases, the transport of internal energy is assumed to be entirely kinetic (diffusion mechanism).

Viscosity of Three Binary Gaseous Mixtures

This paper reports relative measurements of the viscosity of three binary mixtures: Ne–N2, He–CO2, N2–Ar. Measurements were made at 20° and 30°C at pressures from 1–25 atm.

Geothermal preheating in fossil-fired steam power plants

A thermodynamic analysis of a hybrid fossil geothermal power plant in which the low-grade geothermal energy is used for preheating the feedwater in a fossil-fired steam power plant is presented. By restricting the geofluid to sensible heat addition, the entropy production in this process can be reduced. This results in an overall improvement in the utilization of the two energy sources. The performance of the hybrid system is studied in terms of suitably defined figures of merit. These include criteria for the choice of the appropriate hybrid utilization strategy, given the finite nature of geothermal and fossil resources. The question of optimum bleed conditions in a cycle comprising both geothermal and regenerative feedwater heating is discussed.

Fossil superheating in geothermal steam power plants

Results of thermodynamic studies of geothermal steam power systems incorporating fossil-fired superheaters are reported. One- and two-stage systems are covered. Realistic assumptions have been included to account for losses that may be incurred in actual plants. The systems are evaluated on the basis of a number of appropriate figures of merit. It is found that fossil superheat hybrid geothermal power plants offer a thermodynamic advantage over individual fossil and geothermal plants for a wide range of operating conditions, and deserve consideration whenever fossil and geothermal energy resources are found in reasonable proximity.

Hybrid Solar-Geothermal Power Generation to Increase the Energy Production from a Binary Geothermal Plant

This article examines how hybridization using solar thermal energy can increase the power output of a geothermal binary power plant that is operating on geothermal fluid conditions that fall short of design values in temperature and flow rate. The power cycle consists of a subcritical organic Rankine cycle using industrial grade isobutane as the working fluid. Each of the power plant units includes two expanders, a vaporizer, a preheater and air-cooled condensers. Aspen Plus was used to model the plant; the model was validated and adjusted by comparing its predictions to data collected during the first year of operation. The model was then run to determine the best strategy for distributing the available geothermal fluid between the two units to optimize the plant for the existing degraded geofluid conditions. Two solar-geothermal hybrid designs were evaluated to assess their ability to increase the power output and the annual energy production relative to the geothermal-only case.Copyright

Viscosity and Binary Diffusion Coefficient of Neon—Carbon Dioxide Mixtures at 20° and 30°C

This paper reports relative measurements of the viscosity of Ne–CO2 mixtures which do not seem to have been studied before. Measurements were made at 20° and 30°C at pressures from 1 to 25 atm.