Critical heat flowrates in subcooled flow boiling

Matters related to calculating critical heat flowrates during boiling in a highly subcooled flow are considered. Existing data on heat transfer for swirl flow with one-sided heating are analyzed, and a formula for calculating critical heat flowrates is proposed. The conditions under which the thermodynamic limit of boiling is reached are analyzed.     

半壁受热管内插扭带的过冷流动沸腾传热特性数值模拟

本文使用欧拉多相流模型数值模拟水在半壁受热管内插入扭带的过冷流动沸腾的传热特性,并用公开发表的实验数据对模拟数据进行验证,2种数据吻合良好。同时,在插入扭带的不同扭转比y=4.0、8.0、11.4,质量流量G=900、1 165 kg/(m²·s),热流密度q=570、741 kW/m²情况下,对过冷流动沸腾下截气率、沸腾起始点（ONB）、水温、壁面温度分布和传热系数等传热特性进行了分析。结果表明,管内插入扭带对于半壁面加热的过冷流动沸腾具有传热强化作用,而且扭转程度越大的扭带对半壁加热的过冷流动沸腾强化换 热越强烈。     

Peculiarities of boiling in subcooled flow

Peculiarities of heat transfer during boiling in high-velocity flow subcooled relative to the saturation temperature are analyzed. Flow structure is analyzed. Boiling in swirled flow and boiling in flow heated on one side are considered.     

Heat transfer under conditions of film boiling in turbulent flow of subcooled liquid

Results are given of analysis of experimental data on heat transfer in film boiling in a swirl turbulent flow under conditions of high subcooling. An equation is derived that both describes well our experimental data and agrees with the results of other experimental investigations.     

An analysis of correlations for calculating critical heat fluxes in substantiating the safety of a reactor plant

The experimental data and correlations for calculating critical heat flux that are used in substantiating the safety of a VVER-1200 reactor plant are analyzed.     

Applicability of the standard method for calculating heat transfer in furnaces with stokers

Features pertinent toheat transfer in furnaces during combustion of solid fuel in a bed are considered. The results from the tests are compared with the calculated characteristics of heat transfer. A conclusion is drawn regarding the need to revise the calculation method for furnaces with a bed of burning fuel.     

Studying heat transfer enhancement for water boiling on a surface with micro- and nanorelief

We present the results from a study of heat transfer enhancement for bulk water boiling at atmospheric pressure on a surface with micro- and nanorelief, including a relief formed from silicon carbide and aluminum oxide nanoparticles. Horizontally oriented steel tube 1.2 mm in diameter and copper plate 15 × 3 mm in size were selected as test sections. The process was recorded by means of a video camera, and the values of heat transfer, critical heat fluxes, and contact angles were measured. The use of surface with micro- and nanorelief makes it possible to obtain a significantly higher critical heat flux and boiling heat transfer coefficient owing to a change of surface wettability. The results of investigations can find use in compact heat exchangers, refrigerating plants, heat pipes, in the mirrors of high-capacity lasers, in the targets and resonators of charged particle accelerators and for external cooling of reactor vessels under emergency conditions.     

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.     

Heat transfer during the boiling of liquid on microstructured surfaces. Part 2: Visualization of boiling and critical heat fluxes

Results from visualization of boiling process and experimental study of critical heat fluxes on microstructured surfaces are presented. The studied surfaces were obtained using the deforming cutting method and have different design shapes and sizes. Mechanisms of heat transfer enhancement are substantiated. A factor of 4.1 higher value of critical heat flux is obtained.     

不同扩展换热面传热、积灰、磨损特性对比

为了对低温换热器优化选型,利用热力计算和数值模拟的方法,对比分析了螺旋肋片管和H型鳍片管的传热、积灰、磨损特性。结果表明:常规结构参数下,单位长度的螺旋肋片管具有更大的换热效率,在达到相同换热量时,其钢材消耗是H型鳍片管的42.87%,烟气阻力是H型鳍片管的61.45%;H型鳍片管由于其特殊的沟槽结构,形成的涡流方向与主流速度相反,垂直冲刷基管背风面,达到自清灰的目的,其鳍片无侧向气流冲刷,整体磨损较轻。因此,螺旋肋片管的换热性能更好,但H型鳍片管的防积灰和耐磨性均优于螺旋肋片管。     

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.     

低沸点工质在余热利用中的应用分析

针对火力发电厂烟气排放带走大量余热的问题,阐述了低沸点工质选择依据及利用特性,提出了利用低沸点工质对烟气余热进行回收使之发电的方案,通过计算确定了系统相关参数,分析了低沸点工质发电系统的经济性、节能性及环保效益。分析结果表明,利用低沸点工质进行发电利用了烟气余热,可以有效节约煤炭消耗量,提高锅炉热效率。     

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.     

凝汽器传热端差的计算与分析

对凝汽器传热端差的各个主要影响因素及它们之间的关系进行了分析 ,解释了有关表达式及相关概念难以理解的问题 ,利用不同容量级机组的有关参数进行计算 ,并联系工程实际 ,进一步验证分析方法及结果的正确性。该结果不仅适用于凝汽器端差的分析 ,对于其它换热器的传热端差计算同样具有实用意义     

Heat transfer under nucleate boiling: Possibilities and limitations of a theoretical analysis

Analysis of different methods of studying nucleate boiling of liquids and results of numerical simulation of primary processes that determine its regularities are presented. The important role of approximate theories, which include the most significant aspects of the boiling process, is shown.     

The effect of an electric field on boiling heat transfer ofrefrigerant-11-boiling on a single tube

The effect of an electric field on boiling refrigerant R-11 was investigated experimentally. The test section consisted of a flat plate and a single tube with several rows of electrode wire. The influence of refrigerant oil, the surface roughness of the test tube, and polarity of an applied voltage on the heat transfer performance were studied. The following results were obtained: as the applied voltage increased, the number of boiling bubbles decreased but the heat transfer coefficient increased; no deterioration of heat by the oil contamination occurred; and the polarity of the applied voltage affected the boiling heat transfer     

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.     

Study of pressure drop and heat transfer in a swirl flow with one-sided heating in a range of heat flowrates below boiling crisis

A representative mass of experimental data on pressure drop and heat transfer under forced convection and boiling in a swirl water flow under one-sided heating conditions is obtained. Recommendations are given for calculating pressure drop in a swirl flow. A method of calculating heat transfer in channels with onesided heating is proposed.     

Heat transfer during the boiling of liquid on microstructured surfaces. Part 1: Heat transfer during the boiling of water

Results from an experimental investigation of heat transfer on microstructured surfaces obtained using the deforming cutting method and having different design shapes and sizes are presented. Heat transfer enhancement by a factor of up to 9 as compared with that on a smooth surface is obtained. Principles for constructing physical models of boiling enhancement are given.     

Numerical analysis method of heat transfer in an electronic component using sensitivity analysis

Numerical models applied to real-life engineering processes have many input parameters that are not always known with a sufficient degree of certainty. Moreover, models are characterized by their mathematical complexity and time-consuming calculations. In this context, our certified reduced basis (crb) model is developed taking into account the input uncertainties which produce many uncertain and different outputs. In order to assess more precisely the relative importance of input parameters on the model outputs, we complete and use a quantitative sensitivity analysis which is a crucial tool in the development and evaluation of complex models. In the current paper, the parametrized crb method is introduced and applied successfully for a simplified 2D heat transfer of electronic components. Furthermore, different sensitivity analysis methods have been compared; Specifically, we have used linear sensitivity methods, one factor at a time design, and global techniques such as Morris one factor at a time, Sobol’s methods and Monte Carlo sampling coupled with scatter plot and correlation analysis.