Sun Feng-rui

Improvement of tree-like network constructal method for heat conduction optimization

The analysis of the “tree-like network” construct method has been repeated. The high effective conduction channel distribution has been optimized again, without the premise that the new order assembly construct must be assembled by the optimized last order construct. It is proved that the “tree-like network” construct method is faultiness. A more optimal construct is obtained, and when the thermal conductivity and the proportion of the two heat conduction materials are constant, the limit of the minimum heat resistance is derived. All these conclusions can be used to guide the engineering application.

Thermal insulation constructal optimization for steel rolling reheating furnace wall based on entransy dissipation extremum principle

Analogizing with the heat conduction process, the entransy dissipation extremum principle for thermal insulation process can be described as: for a fixed boundary heat flux (heat loss) with certain constraints, the thermal insulation process is optimized when the entransy dissipation is maximized (maximum average temperature difference), while for a fixed boundary temperature, the thermal insulation process is optimized when the entransy dissipation is minimized (minimum average heat loss rate). Based on the constructal theory, the constructal optimizations of a single plane and cylindrical insulation layers as well as multi-layer insulation layers of the steel rolling reheating furnace walls are carried out for the fixed boundary temperatures and by taking the minimization of entransy dissipation rate as optimization objective. The optimal constructs of these three kinds of insulation structures with distributed thicknesses are obtained. The results show that compared with the insulation layers with uniform thicknesses and the optimal constructs of the insulation layers obtained by minimum heat loss rate, the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate are obviously different from those of the former two insulation layers; the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate can effectively reduce the average heat loss rates of the insulation layers, and can help to improve their global thermal insulation performances. The entransy dissipation extremum principle is applied to the constructal optimizations of insulation systems, which will help to extend the application range of the entransy dissipation extremum principle.

Constructal optimization for H-shaped multi-scale heat exchanger based on entransy theory

Analogizing with the definition of thermal efficiency of a heat exchanger, the entransy dissipation efficiency of a heat exchanger is defined as the ratio of dimensionless entransy dissipation rate to dimensionless pumping power of the heat exchanger. For the constraints of the total tube volume and total tube surface area of the heat exchanger, the constructal optimization of an H-shaped multi-scale heat exchanger is carried out by taking entransy dissipation efficiency maximization as optimization objective, and the optimal construct of the H-shaped multi-scale heat exchanger with maximum entransy dissipation efficiency is obtained. The results show that for the specified total tube volume of the heat exchanger, the optimal constructs of the first order T-shaped heat exchanger based on the maximizations of the thermal efficiency and entransy dissipation efficiency are obviously different with the lower mass flow rates of the cold and hot fluids. For the H-shaped multi-scale heat exchanger, the entransy dissipation efficiency decreases with the increase in mass flow rate when the heat exchanger order is fixed; for the specified dimensionless mass flow rate M (M<32.9), the entransy dissipation efficiency decreases with the increase in the heat exchanger order. The performance of the multi-scale heat exchanger is obviously improved compared with that of the single-scale heat exchanger. Moreover, the heat exchanger subjected to the total tube surface area constraint is also discussed in the paper. The optimization results obtained in this paper can provide a great compromise between the heat transfer and flow performances of the heat exchanger, provide some guidelines for the optimal designs of heat exchangers, and also enrich the connotation of entransy theory.

Cooling Load Density Analysis and Optimization for an Endoreversible Air Refrigerator

The performance analysis and optimization of an endoreversible air refrigerator is carried out by taking the cooling load density, which is defined as the ratio of cooling load to the maximum specific volume in the cycle, as the optimization objective in this paper. The results obtained are different from those with the cooling load objective. Numerical examples show the effects of pressure ratio and allocation of heat exchanger inventory on the cooling load density of the refrigerator.The performance analysis and optimization of an endoreversible air refrigerator is carried out by taking the cooling load density, which is defined as the ratio of cooling load to the maximum specific volume in the cycle, as the optimization objective in this paper. The results obtained are different from those with the cooling load objective. Numerical examples show the effects of pressure ratio and allocation of heat exchanger inventory on the cooling load density of the refrigerator.

Numerical simulation of sinter cooling processes in vertical tank and annular cooler

针对烧结矿冷却的两种基本模式——环冷式和竖罐式, 分别建立了环冷机、竖罐内对流换热过程的非稳态模型, 并运用场协同理论进行了分析比较. 结果表明: 在相同的冷却效果下, 竖罐式冷却过程传热的场协同数明显大于环冷式, 因此可以大大加强热烧结矿高温显热的回收. 同时研究了气料比、料层总高度、料层半径等因素对于竖罐式烧结矿冷却过程场协同数的影响, 从节约能耗的角度, 指出了在兼顾冷却传热性能、实际生产需求的条件下, 应当选择相对较小的气料比, 且冷却竖罐应由“瘦高型”向“矮胖型”发展.

Progress in study on finite time thermodynamic performance optimization for three kinds of microscopic energy conversion systems

With the development of molecular biology technology, nanotechnology and micro electronic technology, more and more attentions have been paid to the microscopic energy conversion systems. The research on energy conversion mechanism and efficiency for micro-energy conversion system is a new subject concerning the interdisciplinary integration of thermodynamics, statistical mechanics, physics theory, etc. Performance optimization is one of the key science problems in revealing the mechanism of energy conversion and improving efficiency of energy utilization for micro-energy conversion system. On the basis of introducing the origin and development of the finite time thermodynamics theory, this paper reviews the recent advances of thermodynamic optimization for three kinds of typical microscopic energy conversion systems, i.e., the thermal Brownian motors, energy selective electron engines and the thermionic energy conversion devices, and proposes the future research prospects.

Application of Improved BCC Algorithm and RBFNN in Identification of Defect Parameters

The identification of defect parameters in thermal non-destructive test and evaluation (TNDT/E) was considered as a kind of inverse heat transfer problem (IHTP) and a kind of structure design optimization problem, and the design results should meet the surface temperature profile of the apparatus with defects. An improved bacterial colony chemo taxis (IBCC) optimization algorithm and a radial basis function neural network (RBFNN) are applied to the identification of defects parameters. The RBFNN is a precise and convenient surrogate model for the time costly finite element computation, which obtains the surface temperature with different defect parameters. The IBCC optimization algorithm is derivatively-free, and the convergence speed is fast. This method is applied to a simple verification case and the result is acceptable. The algorithm is also compared with the particle swarm optimization (PSO) algorithm, and the IBCC algorithm can access the optimum with faster speed.

Thermodynamic analysis and optimization for a two-stage thermoelectric generator device with cylindrical tubes driven by sintering flue gas heat

针对钢铁工业中烧结烟气余热资源丰富但回收利用率低的现状, 建立了烧结烟气余热驱动圆筒式两级热电发电装置的有限时间热力学模型. 以最大功率输出为目标函数, 应用Matlab优化工具箱优化了热电单元尺寸和工作电流, 分析了烟气换热通道几何尺寸和多边形边数对优化变量和最优性能的影响, 并从经济性角度计算了投资回收周期. 结果表明: 对于正方形截面管道, 烧结烟气为350℃时, 优化前功率为5.59 kW, 优化后功率为7.97 kW, 提高42.39%. 热电模块价格为40元/块时, 设备回收周期为6年左右.

Pipe defect sizing with matching pursuit based on modified dynamic differential evolution algorithm to recognize guided wave signal

The modified dynamic differential evolution (MDDE) algorithm is proposed and applied to matching pursuit (MP) method. Two kinds of steel pipes with blind holes, and notches of different size, respectively, are tested by guided wave test system. The measured signals are decomposed by MP and the defect signals are easy to recognize from the processed signals. The average square root of the residual signals (ASRRS) after each matching pursuit iteration are calculated. The decline trend of ASRRS becomes greater when the defects are bigger. This feature can work as a criterion to estimate the defect size of steel pipes.

Guided waves modes identification in pipes detection by application of the matching pursuit method

Guided waves have the multi-modes and dispersive characteristic and the mode conversion at boundary or with defects in pipes, which make it very difficult to identify different guided waves mode reflection signals in pipes detection. The experiment method is using guided waves to detect two stainless steel pipes, one pipe has no defect and another pipe has a hole defect. The guided waves detection echo signals are obtained. By calculating the Chirplet match atom parameters and the time frequency distributions spectrum of guided waves detection echo signals, guided waves mode with T(0,1),F(1,2) and L(0,2) are respectively identified for no defect pipe detection, and defect echo consisted by two wave-packets with T(0,1) and F(1,2) mode is also identified for defect pipe detection. The results show that the matching pursuit method has a tremendous advantage to identify different guided waves modes signals in pipes non-destructive testing.