Isaac Shnaid

Thermodynamically consistent description of heat conduction with finite speed of heat propagation

Abstract In this work, governing equations for heat conduction with finite speed of heat propagation are derived directly from classical thermodynamics. For a one-dimensional flow of heat, the developed governing equation is linear and of parabolic type. In a three dimensional case, the system of nonlinear equations is formulated. Analytical solutions of the equations for one-dimensional flow of heat are obtained, and their analysis shows characteristic features of heat propagation with finite speed, being fully consistent with classical thermodynamics.

Novel Compressed Air Energy Storage (CAES)Systems Applying Air Expanders

In Compressed Air Energy Storage (CAES) systems, off-peak electric energy is consumed by air compressors that charge CAES reservoirs. During peak load hours, air released from the CAES reservoir expands, producing electric power. Two novel CAES systems, improving their reliability and efficiency, are introduced.The first system is the CAES Plant Integrated with a Gas Turbine (CAESIGT), in which 40 percent of the power output is produced by a standard gas turbine, and 60 percent by an air expander utilizing compressed air that is preheated by the exhaust gases of the gas turbine. For certain initial parameters of the compressed air, its temperature after expansion becomes lower than the ambient temperature. This cold air can be used as a source for refrigeration of the gas turbine inlet air and for other purposes.In the CAES system of the second type, multistage expansion of compressed air is applied. Reheating air between expander stages is provided either by refrigerated substances, by heat sources from surroundings, or by non fuel heat sources such as the waste heat from industry, solar ponds, etc.Thermodynamic and economic analyses of the novel CAES systems are carried out.Copyright

Governing Equations for Heat Conduction With Finite Speed of Heat Propagation

In heat conduction, two different analytical approaches exist. The classical approach is based on a parabolic type Fourier equation with infinite speed of heat propagation. The second approach employs the hyperbolic type governing equation assuming finite speed of heat propagation. This approach requires fundamental modifications of classical thermodynamics which are developed in the frame of extended thermodynamics. In this work, governing equations for heat conduction with finite speed of heat propagation are derived directly from classical thermodynamics. For a linear flow of heat, the developed governing equation is linear and of parabolic type. In a three dimensional case, the system of nonlinear equations is formulated. Analytical solutions of the equations for linear flow of heat are obtained, and their analysis shows characteristic features of heat propagation with finite speed, being fully consistent with classical thermodynamics.Copyright

Thermodynamic Optimization of Reheat Gas Turbine Cycles Combined With Bottoming Cycles

In this work, thermodynamic optimization of reheat gas turbine cycles (without intercooling and recuperative heat exchange) combined with bottoming cycles, is done. Thermodynamic conditions ensuring the combined cycle engine maximal specific work and thermal efficiency are formulated for a general case of arbitrary number of reheat stages with different inlet gas temperatures and isentropic efficiencies.Parametric analyses show that application of reheat cycles brings significant improvement of gas turbine and combined cycle specific work and efficiency in comparison with a case of a simple cycle gas turbine.Copyright