Comparative analysis of correlations for calculating subcooled boiling heat transfer

Results of calculations of the tube wall temperature under flow boiling of water subcooled relative to the saturation temperature are presented. These calculations are performed using different calculation techniques. The comparison and the analysis of the calculation techniques were conducted with the use of experimental data obtained by several authors.     

Development of a method for calculating high-dimension heat networks

A transition from the mass balance equations based on Kirchhoff’s first and second laws to modeling on the basis of a discretized continuity equation is made for describing a hydraulic network. A technique for calculating high-dimension hydraulic and heat networks based on the numerical finite-difference control volume method is developed. Unlike the existing approaches, the proposed technique does not involve the need to determine hydraulic loops and boils down to solving the problem of obtaining a unified field of pressures for the entire calculation region. This advantage of the proposed method opens the possibility of applying it for solving high-dimension problems containing more than a million of hydraulic links. The proposed numerical method features stable operation for hydraulic networks the neighboring links of which may have pressure drop coefficients differing from each other by more than 10 orders of magnitude. In contrast, the global gradient algorithm implemented in the standard software system EPANET is of little use for such applications. The convergence rate of the proposed technique is close to that of the Todini gradient algorithm and is almost independent of the problem dimension.     

Calculation of heat transfer in boiler furnaces during firing of fuel in a bed

A method for calculating complex heat transfer in furnaces is proposed, central to which is using the experimentally determined temperature of the bed of burning solid fuel.     

Investigating the influence of staged fuel combustion on heat transfer in the furnaces of gas-and-oil-fired boilers

Results are presented from industrial tests carried out on furnaces used in different types of gas-and-oil-fired boilers utilizing a two-stage fuel combustion scheme. It is revealed that the temperature of gases tends to increase at the end of furnaces, a phenomenon that must be taken into account during the furnace design.     

Regularities of heat transfer in the gas layers of a steam boiler furnace flame. Part II. Gas layer radiation laws and the procedure for calculating heat transfer in furnaces,fire boxes,and combustion chambers developed on the basis of these laws

The article presents the results stemming from the scientific discovery of laws relating to radiation from the gas layers generated during flame combustion of fuel and when electric arc burns in electric-arc steel-melting furnaces. The procedure for calculating heat transfer in electric-arc and torch furnaces, fire-boxes, and combustion chambers elaborated on the basis of this discovery is described.     

A universal relation for calculating convective heat transfer in transversely streamlined bundles of smooth tubes

Experimental data on convective heat transfer in smooth-tube bundles streamlined by a transverse flow in the range of Reynolds numbers from 3 × 10³ to 1 × 10⁵ are generalized. A universal relation is obtained that allows heat transfer in bundles with staggered and in-line arrangements to be calculated in the range of pitch characteristics covering all practical applications with better accuracy as compared with the well-known calculation procedures.     

基于Taguchi方法强化翅片传热性能的C型换热器

第二代风管机多采用V型分段拼接换热器,其翅片形状和表面强化结构一般均匀分布,在非均匀风场下的换热能力无法充分发挥.设计一种应用子风管机的C型换热器,采用Taguchi方法分别对高低风速区的翅片表面强化结构进行优化设计;选取5种方案进行换热仿真,对桥缝区域进行排水仿真,最终确定最优方案进行整机测试.结果 表明,低风速区桥宽1.4 mm,桥高0.6 mm,桥数为4,高风速区桥宽1.2 mm,桥高0.6 mm,桥数为2时性能最佳.表面强化结构分区处理、上下侧非对称布置以及管间距非等宽设计使得C型翅片强化传热结构与风场分布精准匹配,并且兼顾排水性能.优化后的C型换热器相比于V型,APF平均提高6.4％,换热器成本降低14.5％.     

Procedure of calculating liquid flowrates in wall film and heat transfer crisis in tubes

A brief review of investigations into liquid distribution between the flow core and wall film in tubes previously carried out is given. The relationship between mass transfer processes and heat transfer crisis is shown. The procedure of calculating heat transfer crisis in tubes with uniform heat input along the length based on experimental data from the databank of the Physics and Power Engineering Institute (FEI) is presented.     

Some results of the verification of SERPENT code while calculating heat transfer crisis in uniformly heated tubes

The results of calculating the parameters of heat transfer crisis regimes in uniformly heated tubes, obtained with the aid of look-up tables (LTs) Grnv-95 and FEI-91 are presented.     

软包装锂离子动力电池生热速率测算方法研究

从锂离子动力电池的生热原理入手,参照Bernardi电池生热模型采集相关实验数据,并对实验数据进行处理,研究电池的温升特性,测算出锂电池的等效热容值和生热速率公式,为使用数字化模型研究单体电池的温度场分布特性提供了参数依据。     

Regularities pertinent to heat transfer in the gas layers of a torch in steam boiler fireboxes. Part III. Examples of heat transfer calculations in torch furnaces and steam boiler fireboxes

A procedure for calculating heat transfer in steam boiler fireboxes is developed proceeding from the scientific discovery of laws pertinent to radiation from torch gas layers. By using this procedure, it is possible to determine the distribution of heat flux densities both along the height and perimeter of all waterwall surfaces in a firebox and to calculate the maximal densities of incident heat fluxes. Examples of heat transfer calculation in a torch furnace and steam boiler firebox carried out using the procedure developed on the basis of the above-mentioned discovery are given. The calculation results are in satisfactory agreement with the results of heat transfer measurements in a torch furnace and steam boiler firebox. The difference between the calculated data and measurement results does not exceed 12%.     

A method for describing and calculating critical heat fluxes in annular channels in a wide range of parameters

The paper presents a method for describing and calculating critical heat fluxes during flow of boiling water in concentric and eccentric annular channels heated on one and two sides for different ratios of heat fluxes on opposite walls and for different ratios of annular channel radiuses and eccentricities.     

Three-zonal engineering method of heat calculation for fluidized bed furnaces based on data on commercial investigations of heat generation distribution during biomass combustion

A three-zonal method of heat calculation of furnaces for combustion of biomass and low-caloric fuel in the fluidized bed is described. The method is based on equations of thermal and material balances that account for heat generation by fuel in the zone, heat-and-mass transfer heat exchange between the furnace media and surfaces that bound the zone, and heat-and-mass transfer between furnace zones. The calculation procedure for heat generation by fuel in the fluidized bed (FB) using the heat generation portion by the fuel is proposed. Based on commercial investigations, the main factors that affect the average temperature in the FB and the portion of fuel heat that is released in the FB are determined. Results of commercial investigations showed that the airflow coefficient in the FB should be recognized as the main operation parameter that affects the average temperature in the FB and, consequently, heat generation in the FB. The gas flow rate in the FB can be marked out as the second factor that affects the consumption degree of oxidizer supplied in the FB. Commercial investigations revealed that mixing is affected by the gas flow rate in the FB and the bed material particle size, which may be changed during the boiler operation because of the agglomeration of particles of sand and ash. The calculation processing of commercial investigations on a KM-75-40M boiler of a CHP-3 of an Arkhangelsk Pulp and Paper Mill (APPM), which was carried out using the inverse problem procedure by means of a developed computer program, determined the range of the fuel heat release share in the FB, which was 0.26–0.45 at an excess air factor of 0.59–0.93 in the bed, and the heat release share in the maximum temperature zone in the total heat release in the superbed space. The heat release share in the bed is determined as an approximating function of the excess air factor in the bed and the fluidization number. The research results can be used during designing boilers with the fluidized bed on biomass.     

A method of evaluating heat transfer during nonisothermal absorption

A method of carrying out an engineering calculation of heat and mass transfer during nonisothermal absorption on a solution film that flows down a vertical wall surface is proposed.     

Using the smith method for calculating the mean temperature difference in a cross-flow heat exchanger with a single-pass motion of nonmixing media through both cavities

Methods for calculating the mean temperature difference in cross-flow heat exchangers with single-pass motion of nonmixing media through both cavities are considered. An algorithm implementing the Smith method is proposed.     

基于差分进化算法的动态可用输电能力计算研究

基于考虑暂态稳定约束的最优潮流（TSCOPF）建立了动态可用输电能力问题的数学模型。提出了采用差分进化算法（DE）求解考虑暂态稳定约束的可用输电能力（ATC）问题。利用不需要任何惩罚系数的合成适应度函数法处理约束问题。该算法原理简单,受控参数少,实施随机、并行、直接的全局搜索,易于理解和实现,且收敛性好,计算速度快,是一种求解非线性、不可微、多极值和高维的复杂函数的一种有效和鲁棒的方法。以WSCC9节点系统的计算结果为例验证了该方法的有效性和合理性。     

Experience gained from using a computer program implementing the 3D zone-wise method for calculating heat transfer in the furnace chambers of the coal-fired boilers of 350- and 575-MW power units

We describe the experience gained from more than 10 years of using the computer program imple-menting the 3D zone-wise method for calculating heat transfer in the furnace chambers of 350- and 575-MW power units installed at thermal power stations of Israel.     

基于差分进化算法的动态可用输电能力计算研究

基于考虑暂态稳定约束的最优潮流(TSCOPF)建立了动态可用输电能力问题的数学模型.提出了采用差分进化算法(DE)求解考虑暂态稳定约束的可用输电能力(ATC)问题.利用不需要任何惩罚系数的合成适应度函数法处理约束问题.该算法原理简单,受控参数少,实施随机、并行、直接的全局搜索,易于理解和实现,且收敛性好,计算速度快,是一种求解非线性、不可微、多极值和高维的复杂函数的一种有效和鲁棒的方法.以WSCC9节点系统的计算结果为例验证了该方法的有效性和合理性.     

A simplified method for calculating the substation grounding gridresistance

A simple and accurate formula for calculating the grounding grid resistance is proposed in this paper. This method is based on a theoretical manipulation of the numerical moment method and of the current image. The formula is dependent on the substation grounding grid design, such as grid depth, grid size, number of meshes, grid-conductor diameter, etc. A comparison study is performed to check the accuracy of the proposed formula with respect to six different formulas and methods in the literature. An excellent agreement was found between the results of this formula and the results of a sophisticated computerized method     

Approximate method for calculating the impedances of multiconductors with cross sections of arbitrary shapes

This paper proposes an approximate impedance formula of a conductor with an arbitrary cross section, and also a method of approximating the conductor by an equivalent circular conductor. Thus, a multiconductor system consisting of arbitrary cross section conductors is represented by circular cross section conductors, the impedance of admittance of which are evaluated by the existing impedance and admittance formulas. The calculated results by the proposed method agree satisfactorily with measured results and numerical results by a finite-element method which is, at present, the only way of calculating such impedance, but requires a large computation time and large memory. The proposed method might be very useful in evaluating the impedance and admittance of a multiconductor system consisting of arbitrary cross section conductors.