Thermodynamics Of Heat Engines Research Articles

A Simple Theory for Waterspouts

Abstract It is shown that the simple thermodynamic theory for dust devils, proposed by Renno et al., also applies to waterspouts. The theory is based on the thermodynamics of heat engines and predicts the central pressure and the wind speed of these convective vortices. Moreover, it provides a simple physical interpretation of their general characteristics. In particular, the heat engine theory shows that convective vortices are more likely to form in the regions where the occurrence of the warmest and moistest updrafts and the coldest and driest downdrafts are supported by the local environment. These are the regions where both the heat input into the convective heat engine is maximum and the solenoidal generation of vorticity is the greatest. This explains why waterspouts are frequently observed near the boundaries between relatively warm and relatively cold waters. Moreover, since the work done by the convective heat engine is equal to the total heat input multiplied by the thermodynamic efficiency, th...

Convective Circulations Induced by Surface Heterogeneities

A simple theory for convective circulations induced by surface heterogeneities is proposed. The theory is based on the thermodynamics of heat engines and provides a simple physical explanation for the general characteristics of circulations forced by surface inhomogeneities in sloping terrains. In particular, the theory is applied to a mesoscale circulation induced by deforestation. It predicts that the intensity of the mesoscale convective circulation forced by deforestation depends on the difference of the near-surface nonadiabatic temperature and humidity between the forest and cleared regions and on the depth of the convective boundary layer. The theory was successfully tested against observations made during a field experiment in the Amazon forest and a nearby clearing.

Martian and terrestrial dust devils: Test of a scaling theory using Pathfinder data

The Mars Pathfinder meteorological station recorded wind, pressure, and temperature fluctuations that have been interpreted as dust devils: warm‐core vortices that form at the bottom of connective plumes. We apply a scaling theory [Rennó et al., 1998], developed to explain terrestrial dust devil observations, to test the validity of this interpretation and to provide a simple physical interpretation of the general characteristics of Martian dust devils. The theory is based on the thermodynamics of heat engines and predicts the central pressure and the wind speed of the connective vortices. Our findings are as follows: For the best documented candidate event (sol 25), observed wind and pressure fluctuations are consistent with those predicted by the model and hence strengthen the interpretation of this case as a dust devil. A number of other candidates, less well documented, however, also are consistent with passage of a dust devil over or near the lander. Temperature fluctuations observed on other sols permit dust devils an order of magnitude larger than the ones measured by the meteorology package. The strongest dust devils predicted by our theory have a central pressure deficit of about 50 Pa and wind speed of about 60 m s−1. The strongest dust devils are capable of lofting dust and hence support the interpretation of selected Pathfinder images as showing the passage of dust devils within sight of the lander.

Gross Thermodynamics of Heat Engines in Deep Interior of Earth

From the gross conservation laws of thermodynamics in a convecting material we derive a bound on the ratio of the rate of production of mechanical or magnetic energy to the rate of internal radioactive heating which drives the convection. Our bound for this "efficiency" depends on the temperatures in the material, and can exceed unity. Whether the bound can be attained by "efficiencies" in real fluids is not known, but a simple machine shows that "efficiencies" larger than unity are physically realizable. Our bound gives upper limits on the viscous dissipation in the earth's mantle and ohmic heating in the core, but these limits are too large to be physically interesting.

The Thermodynamics of Heat Engines

THIS is a very good specimen of that sort of book which is an amplification of the lecture notes of a professor who has carefully prepared problems for students. We may not always like the way in which he introduces the subject to his pupils, and we may say that it is unphilosophical and even cryptic, and sometimes too brilliant, but such comments are often due to the fact that his way happens not to be the usual way of presenting the subject. The way of Prof. Reeve probably suits his particular class of unscientific pupils very well. He uses terms in senses somewhat different from those in common use. He is absolutely correct in many statements with which we would willingly find as much fault as Macaulay did with those of Robert Montgomery. For example:— The Thermodynamics of Heat Engines. By Sidney A. Reeve, Professor of Steam-Engineering at the Worcester Polytechnic Institute (U.S.A.). Pp. xiv + 316 + 42. (New York: The Macmillan Company; London: Macmillan and Co., Ltd., 1903.) Price 10S. 6d. net.

Thermodynamics of Heat-Engines

Thermodynamics of Heat-Engines

Thermodynamics of Heat-Engines

Thermodynamics of Heat-Engines

Thermodynamics of Heat-Engines . By Sidney A. Reeve, Professor of Steam Engineering at the Worcester Polytechnic Institute New York and London, The Macmillan Company. 1903. 12mo. Pp. 304; figs. 58; steam tables, etc.

<i>Thermodynamics of Heat-Engines</i> . By Sidney A. Reeve, Professor of Steam Engineering at the Worcester Polytechnic Institute New York and London, The Macmillan Company. 1903. 12mo. Pp. 304; figs. 58; steam tables, etc.