Eur. Phys. J. Plus (2017) 132: 293
https://doi.org/10.1140/epjp/i2017-11561-2

Regular Article

Thermodynamic performance optimization for an irreversible vacuum thermionic generator

¹ Institute of Thermal Science and Power Engineering, Naval University of Engineering, 430033, Wuhan, China
² Military Key Laboratory for Naval Ship Power Engineering, Naval University of Engineering, 430033, Wuhan, China
³ College of Power Engineering, Naval University of Engineering, 430033, Wuhan, China

^* e-mail: lingenchen@hotmail.com

Received: 6 December 2016
Accepted: 18 May 2017
Published online: 4 July 2017

Abstract

Theoretical model of an irreversible vacuum thermionic generator considering external and internal finite rate heat transfer is established in this paper. By assuming radiative heat transfer processes, the general expressions of performance parameters are derived based on non-equilibrium thermodynamics and finite-time thermodynamics (FTT). The thermodynamic performances of the irreversible thermionic device are further analyzed and optimized by using the FTT theory with multiple optimization criteria such as power output, efficiency, ecological function, and efficient power. The influences of design parameters, such as output voltage, collector work function and heat reservoir temperature, on optimal performance are analyzed in detail by numerical calculations. By properly choosing the work function and output voltage, the thermionic generator can be tuned to operate in the optimal condition with maximum power or efficiency. By comparing the device performance at different design points, the optimal operation regions of power and efficiency of the irreversible thermionic generator are determined. The obtained results are of theoretical significance for the optimal design of practical solar-powered thermionic generators.