Atmospheric Vortex Engine

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2. Thermodynamics

2.1 What is Carnot Efficiency?

Heat and work are two forms of energy. The first law of thermodynamics states that energy must be conserved: energy can neither be created nor destroyed. Work can readily be converted to heat. The second law thermodynamics sets a limit on the fraction of a given quantity of heat energy that can be converted to work. The production of work from heat requires heat flow from a hot source to a cold sink.

Carnot efficiency is the maximum efficiency that can be achieved when heat is transferred from the hot source to the cold sink. Carnot efficiency n is: n = 1- TC/TH, where TH is temperature of the hot source and TC is the temperature of the cold source, and where temperatures are in [K] degrees Kelvin. The portion of the heat that is not converted to work is delivered as low temperature waste heat at the cold sink.

Carnot devised an ideal cycle where the heat is received and given up at two definite temperatures. The efficiency of other ideal cycles such as the gas turbine cycle is close to the Carnot efficiency if one uses the average temperature at which the temperature is received and given up, closer yet if one uses average of logarithm of temperature.

2.2 What is the efficiency of thermal power plants?

The efficiency of typical gasoline engines is around 20%. The efficiency of coal and nuclear power plant is typically around 35%. The efficiency of modern high performance coal plants can be up to 45%. The efficiency of combined cycle gas turbine power plants can be up to 55%.

The heat sink for all of the above engines is either the air at the bottom of the atmosphere or a water body whose temperature is likely to be close to the air temperature. For calculation purposes engineers use a nominal cold source temperature of 288 K (15°C). The maximum work that can be produced by transferring heat from a given hot source temperature to 15°C is called exergy.

The maximum efficiency of nuclear power plants is less that that of a coal power plant because the fuel temperature must be kept low to prevent damage to the fuel bundles.

2.3 What is the efficiency of the atmospheric upward heat convection process?

The efficiency of the atmospheric process is the Carnot efficiency calculated using the average temperature at which heat is received as the hot source temperature and the average temperature at which heat is given up as the cold source temperature. Taking the average temperature of the hot source as +20°C and the average temperature of the cold source as -20°C, the efficiency is 14%. 14% of the 128 W/m2 transported upward by convection is converted to work. Atmospheric work production averages 18 W/m2.

The thermodynamic efficiency of atmospheric upward heat transport is roughly independent of whether the heat is transported as sensible or latent heat. For more information on atmospheric efficiency see: Thermodynamic cycle of the atmospheric upward heat convection process.

2.4 What is a reversible process? What is an irreversible process?

A reversible process is a process where work production is the maximum allowed by the Carnot principle. An irreversible process is a process where the work is less than allowed by the Carnot principle. Work readily reverts to heat. In order to capture work, controlled expansion has to take place in a device such as a turbine; there must be a means of getting the work out of the system such as a mechanical shaft – thus the name shaft work.

2.5 Is upward convection in the atmosphere a reversible process?

Atmospheric convection is a highly irreversible process. The kinetic energy of the wind all eventually reverts to heat. In addition, failure to constrain the expansion results in the production of heat instead of work.


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