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An optimization model is established for the reaction process of CO2 hydrogenation to light olefins in a fixed-bed tubular reactor based on finite time thermodynamics or entropy generation minimization theory. In the present study, the specific generation rate (entropy generation rate averaged by the production rate of the target product) is proposed as an optimization objective function and the optimal...
Taking the exergy loss minimization as the optimization objective, an optimization model of coking process is established based on the material balance and energy balance. The optimization problem is solved with the practical production data of a coking plant. The minimum exergy loss and the optimal design parameters are obtained. Performances of the mixed coal before and after optimizations are compared...
A technical solution recycling exhaust gas sensible heat based on thermoelectric power generation is proposed by using finite time thermodynamics. The effects of some key parameters such as exhaust gas inlet temperature, exhaust gas and cooling water heat transfer coefficient on the optimum length of the thermoelectric elements are analyzed. It is found that the gas temperature drops rapidly because...
For the recovery and utilization of high-temperature basic oxygen gas (BOG) generated in the basic oxygen furnace (BOF) process within iron and steel production, a thermochemical recovering method of tubular plug flow reaction is proposed. Accounting for efficient utilization of residual heat and capture of carbon dioxide, methane reforming with carbon dioxide reaction is introduced. With a linear-temperature...
Ecological performance of a single resonance ESE heat engine with heat leakage is conducted by applying finite time thermodynamics. By introducing Nielsen function and numerical calculations, expressions about power output, efficiency, entropy generation rate and ecological objective function are derived; relationships between ecological objective function and power output, between ecological objective...
For the fixed total raw material cost and based on constructal theory and finite time thermodynamics, a BFIM (blast furnace iron-making) process is optimized by taking a complex function as optimization objective. The complex function is integrated with HM (hot metal) yield and useful energy of the BF (blast furnace). The optimal cost distribution of raw materials (namely “generalized optimal construct”)...
Theoretical modeling for a microscopic ESE (energy selective electron) heat engine with double-resonance energy filters is performed in this paper. The heat flow characteristics and performance parameters are discussed in two different cases according to the positions for central energy level of double resonances. It is found that the analytical expressions for performance parameter such as power...
Constructal theory is introduced into the hot metal yield maximization of the blast furnace in this paper. Generalized constructal optimization of a blast furnace is performed for a specified total raw material cost. The optimal distribution of each raw material cost in the total cost, namely “generalized optimal construct”, is obtained. Besides, the optimal charge composition of the blast furnace...
A sulphuric acid decomposition process in a tubular plug-flow reactor with fixed inlet flow rate and completely controllable exterior wall temperature profile and reactants pressure profile is studied in this paper by using finite-time thermodynamics. The maximum production rate of the aimed product SO2 and the optimal exterior wall temperature profile and reactants pressure profile are obtained by...
An optimization model based on material balance and energy balance for a blast furnace iron-making process is established, in which exergy loss minimization is taken as optimization objective. Optimization results are obtained by using sequential quadratic programming method. Effects of coal ratio, top gas temperature, slag basicity and blast parameters on the optimization results are analyzed. The...
Based on constructal theory, the disc-shaped solid–gas reactors combined heat and mass transfer are investigated in this paper. Radial- and branched-pattern of the discs are considered, and the two pattern discs are optimized based on entropy generation rate minimization. The results show that there exist a minimum value of the entropy generation rate and the corresponding optimal construct of the...
A physical and numerical model of two-stage thermoelectric energy harvesting system driven by blast furnace slag water waste heat is established. The performance of the system with counter-flow type heat exchangers is investigated by numerical simulation. In the case of the temperatures of heat reservoirs change over flow passage, the effects of inlet temperature of flushing slag water, convective...
Based on constructal theory, generalized constructal optimization of a solidification heat transfer process of slab continuous casting is carried out by taking a complex function as optimization objective. The complex function is composed of the functions of the heat loss rate and surface temperature gradient of the slab subjected to the constraints of shell thickness, surface temperature and liquid...
Focusing on the low recycling rate of low temperature waste heat in China's iron and steel industry, this study presented a technical solution recycling blast furnace slag flashing water sensible heat based on thermoelectric power generation. The physical and numerical models are established. The effects of some key parameters such as slag washing water temperature, the thermoelectric element length,...
A total momentum filtered energy selective electron (ESE) heat pump model with heat leakage is established in this paper. The analytical expressions of heating load and coefficient of performance (COP) for both the total momentum filtered (k r -filtered) ESE heat pump and the conventionally filtered (k x -filtered) ESE heat pump in which the electrons are transmitted according to the...
Taking into account inner and external multi-irreversibilities, a complete numerical model of commercial thermoelectric generator with finned heat exchangers is established by combining thermodynamics with heat transfer theory. A significant novelty is that physical properties, geometric dimensions, temperature parameters and flow parameters are all considered in the model. The inner effects include...
A multistage irreversible Carnot heat engine system operating between a finite thermal capacity high-temperature fluid reservoir and an infinite thermal capacity low-temperature environment with generalized convective heat transfer law [q∝(ΔT)m] and the irreversibility of heat resistance and internal dissipation is investigated in this paper. Optimal control theory is applied to derive the continuous...
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