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To utilize heat from round shaped heat sources or heat sinks effectively, a segmented annular thermoelectric generator was proposed. Each leg is composed of two materials with different optimum operating temperatures jointed in series. Based upon a developed theoretical model, the influences of annular shape parameter, height ratios of high temperature segment to leg in p- and n-type legs, temperature...
A solar thermoelectric generation system characterized by Fresnel lens, cavity receiver and heat pipe, i.e., FCH-STGS, was proposed. To analyze the performance of FCH-STGS accurately, a comprehensive theoretical model was built, where a finite element method was employed to consider the Thomson effect and temperature-dependence of thermoelectric materials. With this model, the influences of emissivity...
Based on one-dimensional steady analysis, a comprehensive theoretical model for analyzing the performance of TEGs (thermoelectric generators) is proposed, in which finite element method and integral-averaged Seebeck coefficient are employed to effectively consider the effects of temperature-dependence of thermoelectric materials and Thomson effect respectively. The optimal segments for each case are...
A multi-objective function F(X) by the incorporation of single-objective functions, i.e., net power output Wnet, exergy drop of the exhaust gas from inlet to outlet ΔEg, total exergy destruction rate I and system total cost C2013, has been put forward as the subcritical organic Rankine cycle (ORC) performance indicator and solved with the method of linear weighted evaluation function. The optimization...
The performance of the ORC (organic Rankine cycle) systems using zeotropic mixtures as working fluids for recovering waste heat of flue gas from industrial boiler is examined on the basis of thermodynamics and thermo-economics under different operating conditions. In order to explore the potential of the mixtures as the working fluids in the ORC, the effects of various mixtures with different components...
This paper presents an economical evaluation and parametric optimization on subcritical ORC (organic Rankine cycle) system for recovering the low-temperature waste heat of flue gas which is released from industrial boilers. First, the effects of the PPTD (pinch point temperature difference) in evaporator and condenser, and evaporating temperature on the system performance are examined with the EPC...
This paper presents a case study of recovering the waste heat of the exhaust flue gas before entering a flue gas desulphurizer (FGD) in a 600 MW power plant. This waste heat can be recovered by installing a low pressure economizer (LPE) to heat the condensed water which can save the steam extracted from the steam turbine for heating the condensed water and then extra work can be obtained. The energy...
Organic Rankine cycle (ORC) is a promising technology for converting low-grade waste heat into the electricity. This paper carries out an exergoeconomic analysis and performance optimization of a condenser for a binary mixture of vapors in the ORC system. In this model, the exergy loss due to heat transfer between a binary mixture of vapors and the cold fluid is taken into account and other exergy...
The exergy transfer characteristics of fluid flow and heat transfer inside a circular duct under fully developed laminar and turbulent forced convection are presented. Temperature is kept constant at the duct wall. The exergy transfer Nusselt number is put forward and the analytical expressions for exergy transfer Nusselt number are obtained as functions of heat transfer Nusselt number, Reynolds number,...
In this paper, exergy transfer effectiveness is defined to describe the performance of heat exchangers operating above/below the surrounding temperature with/without finite pressure drop. It is discussed systemically that the effects of heat transfer units number, the ratio of the heat capacity of cold fluids to that of hot fluids and flow patterns on exergy transfer effectiveness of heat exchangers...
The examination of exergy transfer characteristics caused by forced convective heat transfer through a duct with constant wall heat flux for thermally and hydrodynamic fully developed laminar and turbulent flows has been presented. The exergy transfer Nusselt number is put forward and the dependence relationships of the exergy transfer Nusselt number on the heat transfer Nusselt number, Reynolds number...
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