scholarly journals Re-Optimization of Expansion Work of a Heated Working Fluid with Generalized Radiative Heat Transfer Law

Entropy ◽  
2020 ◽  
Vol 22 (7) ◽  
pp. 720 ◽  
Author(s):  
Lingen Chen ◽  
Kang Ma ◽  
Yanlin Ge ◽  
Huijun Feng
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Heat Bath ◽  
Working Fluid ◽  
Motion Path ◽  
Process Time ◽  
Taylor Formula ◽  
Optimal Motion ◽  
Elimination Method

Based on the theoretical model of a heated ideal working fluid in the cylinder, the optimal motion path of the piston in this system, for the maximum work output, is re-studied by establishing the changed Lagrangian function and applying the elimination method when the initial internal energy, initial volume, finial volume and the process time are given and generalized radiative heat transfer law between the working fluid and heat bath is considered. The analytical solutions of the intermediate Euler-Lagrange arc with square, cubic and radiative heat transfer laws are taken as examples and obtained. The optimal motion path of the piston with cubic heat transfer law, which is obtained by applying the elimination method, is compared with that obtained by applying the Taylor formula expansion method through numerical example. The comparing result shows that the accuracy of the result which is obtained by applying the elimination method is not affected by the length of time of the expansion process of the working fluid, so this result is more universal.

scholarly journals Effects of radiative heat transfer on the structure of turbulent supersonic channel flow

2011 ◽  
Vol 677 ◽  
pp. 417-444 ◽  
Author(s):  
S. GHOSH ◽  
R. FRIEDRICH ◽  
M. PFITZNER ◽  
CHR. STEMMER ◽  
B. CUENOT ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiation Effects ◽  
Radiative Heat ◽  
Pure Water ◽  
Molecular Transport ◽  
Working Fluid ◽  
Mean Flow ◽  
Total Energy Balance

The interaction between turbulence in a minimal supersonic channel and radiative heat transfer is studied using large-eddy simulation. The working fluid is pure water vapour with temperature-dependent specific heats and molecular transport coefficients. Its line spectra properties are represented with a statistical narrow-band correlated-k model. A grey gas model is also tested. The parallel no-slip channel walls are treated as black surfaces concerning thermal radiation and are kept at a constant temperature of 1000 K. Simulations have been performed for different optical thicknesses (based on the Planck mean absorption coefficient) and different Mach numbers. Results for the mean flow variables, Reynolds stresses and certain terms of their transport equations indicate that thermal radiation effects counteract compressibility (Mach number) effects. An analysis of the total energy balance reveals the importance of radiative heat transfer, compared to the turbulent and mean molecular heat transport.

Optimal Paths for a Light-Driven Engine with [A]=[B] Reacting System and Generalized Radiative Heat Transfer Law

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Lingen Chen ◽  
Kang Ma ◽  
Fengrui Sun
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Optimal Control Theory ◽  
Radiative Heat ◽  
Working Fluid ◽  
Rate Dependent ◽  
System A ◽  
Optimal Paths ◽  
Heat Leakage ◽  
Optimal Configurations

Abstract A generalized radiative heat transfer law is introduced into an irreversible light-driven engine with a working fluid composed of the bimolecular reacting system [A]=[B], and the effects of heat transfer laws on the optimal paths of the engine are investigated in this paper. Piston paths for maximizing work output and minimizing entropy generation are determined for such an engine with rate-dependent loss mechanisms of friction and heat leakage by applying the optimal control theory. Numerical examples for the optimal configurations with three special heat transfer laws ( n=-1, n=1 and n=4 ) are provided, and the obtained results are compared with each other. The research on the optimal paths of a light-driven engine from Newton’s heat transfer law to the generalized radiative heat transfer law enriches the finite time thermodynamics. The results presented herein can provide some guidelines for optimal design and operation of real light-driven engines.

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