S. Manikandan

Performance Optimization of Two-Stage Exoreversible Thermoelectric Converter in Electrically Series and Parallel Configuration

A two-stage exoreversible semiconductor thermoelectric converter (TEC) with internal heat transfer is proposed in two different configurations, i.e., electrically series and electrically parallel. The TEC performance assuming Newton’s heat transfer law is evaluated through a combination of finite-time thermodynamics (FTT) and nonequilibrium thermodynamics. A formulation based on the power output versus working electrical current and efficiency versus working electrical current is applied in this study. For fixed total number of thermoelectric elements, the current–voltage (I–V) characteristics of the series and parallel configurations have been obtained for different combinations of thermoelectric elements in the top and bottom stage. The number of thermoelectric elements in the top stage has been optimized to maximize the power output of the TEC in the electrically series and parallel modes. Thermodynamic models for a multistage TEC system considering internal irreversibilities have been developed in a matrix laboratory Simulink environment. The effect of load resistance on Vopt, Iopt, Voc, and Isc for different combinations of thermoelectric elements in the top and bottom stage has been analyzed. The I–V characteristics obtained for the two-stage series and parallel TEC configurations suggest a range of load resistance values to be chosen, in turn indicating the suitability of the parallel rather than series configuration when designing real multistage TECs. This analysis will be helpful in designing actual multistage TECs.

Performance optimisation of two-stage exoreversible thermoelectric heat pump in electrically series, parallel and isolated configurations

A configuration of the behaviour of an exoreversible two-stage semiconductor thermoelectric heat pump (TEHP) in three different modes, i.e., electrically series, electrically parallel and electrically separated is devised. The TEHP performance assuming Newtons heat transfer law is evaluated through a combination of finite time thermodynamics (FTT) and non-equilibrium thermodynamics. A formulation based on the heating load versus working electrical current and coefficient of performance (COP) versus working electrical current is applied in this study. For fixed total number of thermoelectric elements, optimisation of number of thermoelectric elements of the top stage for maximising the heating load and COP is done here. The complete analysis of effects of various design parameters on the performance of TEHP is formulated. Three thermodynamic models for multi-stage TEHP system considering internal irreversibilities are developed in the matrix laboratory Simulink environment. For typical operating conditions of TEHP system with total 30 thermocouples, the maximum value of COP is improved from 4.56 to 5.20 for same current in electrically parallel mode. This analysis will be helpful in designing the actual multistage TEHPs.

Multi-objective optimization of two stage series connected thermo-electric generator using genetic algorithm

Two-stage thermoelectric generator in exo-reversible mode is thermodynamically optimized in view of finite time thermodynamics (FTT) and multi-objective genetic algorithm (MOGA). Electrically series configuration with only internal irreversibilities of thermoelectric generator has been considered for investigation in the current research. Power output and thermal efficiency of the aforementioned system are considered as dual objective functions obtained from FTT technique. These two objectives are maximized at the same time with the use of multi objective genetic algorithm. For MOGA optimization of thermoelectric generator, five decision variables as number of thermoelectric element pairs at the bottom and top stage as m and n, heat source temperature and heat sink temperature and working electric current has been considered in the current study. MATLAB environment is used to obtain the Pareto Optimal frontier between power output and thermal efficiency and their best optimal values are selected by Fuzzy Bellman-Zadeh decision making technique. A comparative analysis of single objective and dual objective optimization of aforementioned objectives has been carried out and discussed.

Thermodynamic modelling and analysis of thermoelectric cooling system

Exergy analysis has gained significance in analysing the thermal energy systems since it locates and quantifies the irreversibilities in the system. This paper investigates the thermoelectric cooler through exergy analysis. Four thermodynamic models of the thermoelectric cooler considering the internal and external irreversibilities are developed with temperature dependent material properties and then analysed in MATLAB Simulink environment for various operating temperatures. Moreover, analytical expressions for exergy efficiency and irreversibilities for the thermoelectric cooler are developed. The results show that the exergy efficiency of the thermoelectric cooler is lower than the energy efficiency for all thermodynamic models. For a typical operating condition in the irreversible thermoelectric cooler with 31 thermocouples and with TH and TC of 303K and 293K respectively, the maximum energy and exergy efficiency obtained are 2.61 and 8.91% at optimum current of 5.88A. The results also shows that the effect of internal irreversibilities is more pronounced than the external irreversibilities in the performance of thermoelectric cooling system. The effects of irreversible heat transfer and the contact resistance in the exergy efficiency are also studied. This study will be helpful in designing the actual thermoelectric cooling systems.