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Developing energy-saving and high-efficiency crop managements is required for food and energy security. Huang-Huai-Hai Plain produces more than 60% of the wheat in China. However, no published studies have investigated the energy budget of wheat production in this area. Using an input-output energy analysis from 2012 to 2014, we assessed energy flow of various managements. The average energy input...
The present study aims to investigate the performance of a thermoelectric generator (TEG) under the influence of sinusoidal temperature distribution at the hot side or cold side surface. The impacts of the period and amplitude of the periodic temperature, the temperature difference between the two surfaces, and the external load resistance on the power output and efficiency of the TEG are studied...
DME (Dimethyl ether) synthesis from syngas with CO2 utilization through two-step and single step processes is analyzed thermodynamically. The influences of reaction temperature, H2/CO molar ratio, and CO2/CO molar ratio on CO and CO2 conversions, DME selectivity and yield, and thermal behavior are evaluated. Particular attention is paid to the comparison of the performance of DME synthesis between...
This work developed a three-dimensional, multiphysics, and transient model to investigate transient supercooling of TECs (thermoelectric coolers). The model coupled the heat and electricity conductions and considered all thermoelectric effects. The model was well validated by dynamic test data for a TEC (Thermoelectric cooler) start-up process and was compared with the previous heat conduction model...
A multi-objective and multi-parameter optimization is implemented to design the optimal structure of bismuth-telluride-based TEG (thermoelectric generator) module. A multi-physics TEG model combining the SCG (simplified conjugate-gradient) algorithm is used as the optimization tool. The semiconductor pair number, leg length, and base area ratio of semiconductor columns to TEG module significantly...
This paper is based on dynamic optimization methodology to investigate the economic energy efficiency issues in developing countries. The paper introduces some definitions about energy efficiency both in economics and physics, and establishes a quantitative way for measuring the economic energy efficiency. The linkage between economic energy efficiency, energy consumption and other macroeconomic variables...
This work for the first time uses a three-dimensional multi-physics model to optimize the performance of three kinds of two-stage TECs, connected electrically in series, in parallel, and separated, respectively. The optimizations are performed for the two-stage TEC with 30 thermoelectric elements. The number ratio and current ratio are searched to reach the optimal cooling capacity, COP, and maximum...
This paper develops an inverse problem approach to optimize the geometric structure of TECs (thermoelectric coolers). The approach integrates a complete multi-physics TEC model and a simplified conjugate-gradient method. The present TEC model couples the heat and electrical conductions and accounts for all physical mechanisms occurred within TECs. Three geometric parameters, the semiconductor pair...
Thermoelectric devices (TEs) can achieve direct conversion of heat and electricity by semiconductor materials, coupling of heat transfer and electric conduction is important to accurately predict the performance of TEs. This paper develops a general, three-dimensional numerical model of TEs with consideration of coupling of temperature field and electric potential field. The model is used to figure...
A three-dimensional, two-phase, non-isothermal model has been developed to explore the interaction between heat and water transport in proton exchange membrane fuel cells (PEMFCs). Water condensate produced from the electrochemical reaction may accumulate in the open pores of the gas diffusion layer (GDL) and retard the oxygen transport to the catalyst sites. This study predicts the enhancement of...
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