内换热式低压径向氨合成塔应用小结

介绍了国内2400mm内换热式低压径向氨合成塔内件的结构特点及合成系统工艺流程;论述了氨合成塔内件触媒的装填、升温还原方案和操作数据,总结了实际生产运行效果。72h生产运行数据表明,合成氨产量达到600t/d,最高产量可达630t/d。

炉内换热对氧化氮形成的影响

本文通过理论计算研究了燃烧气体燃料锅炉内热力型氧化氮和瞬间型氧化氮的形成与炉内换热条件的关系，确定了它们之间的相互变化规律及热力型氧化氮的近似估算公式。

带内换热器流化床节能原理

通过固定流化床干燥过程中床内空气的对流化、载热、载湿等功能的分析，提出了流化床干燥节能途径。

浅谈釜内换热器的内部芯体套装及其控制方法

釜内换热器的内部芯体套装,内部芯体由一种铝制板翅式换热器芯体,套装中容易产生内部芯体变形、损坏等问题。本文针对釜内换热器内部芯体制订套装方案和设计套装工装。通过使用,釜内换热器的内部芯体套装达到安全,高效、可靠等要求,效果显著,可为同类型釜内换热器的内部芯体套装提供借鉴经验。

新型双层壁隔热屏气膜板内壁面换热特性数值研究

为了研究加入二次倾斜冲击后双层壁隔热屏内通道的流动特征和换热分布，通过数值模拟研究了不同冲击距离和不同中间孔直径下，冲击雷诺数在2500~7500，气膜板内壁面的换热系数分布特征。结果显示：冲击距离越短，高换热区域面积越大，平均换热系数越高；冲击距离对气膜孔所在环腔内的二次冲击和旋流之间的相互作用影响较大；中间孔直径越小，平均换热系数越高，气膜孔所在的环腔内二次冲击范围越小，漩涡冲击范围越大。

凝汽式电厂循环式供水冷端系统耦合数学模型

现有的热力发电厂冷端系统运行优化模型常常把凝汽器进口循环水温度看作定值,但若冷端系统为循环式供水,应考虑冷却塔以及气候条件的影响。为了改进冷端系统运行优化模型,建立了冷却塔内空气饱和或不饱和时传热传质模型和冷却塔通风量计算模型,以及在对凝汽器内传热过程分析简化的基础上建立了凝汽器内换热模型。所建模型相互耦合,联立求解后可得到与凝汽器负荷、循环水量和环境条件相对应的冷端系统各点温度参数,可指导冷端系统优化运行。

Multipoint Infrared Telemetry System for Measuring the Piston Temperature in Internal Combustion Engines

A high precision, high antijamming multipoint infrared telemetry system was developed to measure the piston temperature in internal combustion engine. The temperature at the measuring point is converted into corresponding voltage signal by the thermo-couple first. Then after the V/F stage, the voltage signal is converted into the frequency signal to drive the infrared light-emitting diode to transmit infrared pulses. At the receiver end, a photosensitive audion receives the infrared pulses. After conversion, the voltage recorded by the receiver stands for the magnitude of temperature at the measuring point. Test results of the system indicate that the system is practical and the system can perform multipoint looping temperature measurements for the piston.

Calculation on inner wall temperature in oil-gas pipe flow

Based on the energy equation of gas-liquid flow in pipeline,the explicit temperature drop formula for gas-liquid steady state calculation was derived.This formula took into consideration the Joule-Thomson effect,impact of terrain undulation and heat transfer with the surroundings along the line.Elimination of temperature iteration loop and integration of the explicit temperature equation,instead of enthalpy energy equation,into the conjugated hydraulic and thermal computation have been found to improve the efficiency of algorithm.Then,the inner wall temperature of gas-liquid flow was calculated by using explicit temperature equation and inner wall convective heat transfer coefficient of mixed flow which can be obtained by liquid convective heat transfer coefficient and gas convective heat transfer coefficient on the basis of liquid holdup.The temperature results of gas-liquid flow and inner wall in the case example presented both agree well with those in professional multiphase computational software OLGA.

Evaluation of convective heat transfer in a tube based on local exergy destruction rate

In this study, exergy efficiency is defined to evaluate convective heat transfer in a tube based on the local exergy destruction rate from the equilibrium equation of available potential. By calculating this destruction rate, the local irreversibility of convective heat transfer can be evaluated quantitatively. The exergy efficiency and distribution of local exergy destruction rate for a smooth tube, an enhanced tube into which short-width twisted tape has been inserted, and an optimized tube with exergy destruction minimization are analyzed by solving the governing equations through a finite volume method(FVM). For the smooth tube, the exergy efficiency increases with increasing Reynolds number(Re) and decreases as the heat flux increases, whereas the Nusselt number(Nu) remains constant. For the enhanced tube, the exergy efficiency increases with increasing Reynolds number and increases as the short-width rate(w) increases. An analysis of the distribution of the local exergy destruction rate for a smooth tube shows that exergy destruction in the annular region between the core flow and tube wall is the highest. Furthermore, the exergy destruction for the enhanced and optimized tubes is reduced compared with that of the smooth tube. When the Reynolds number varies from 500 to 1750, the exergy efficiencies for the smooth, enhanced, and optimized tubes are in the ranges 0.367–0.485, 0.705–0.857, and 0.885–0.906, respectively. The results show that exergy efficiency is an effective evaluation criterion for convective heat transfer and the distribution of the local exergy destruction rate reveals the distribution of local irreversible loss. Disturbance in the core flow can reduce exergy destruction, and improve the exergy efficiency as well as heat transfer rate. Besides, optimization with exergy destruction minimization can provide effective guidance to improve the technology of heat transfer enhancement.

The Effect of Heating Direction on Flow Boiling Heat Transfer of R134a in Microchannels

This paper presents effects of heating directions on heat transfer performance of R134 a flow boiling in micro-channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500mm width 500mm depth and 30 mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm^2 and 373.3 to 1244.4 kg/m^2 s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 k W/m^2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.

Analyses of thermodynamic performance for the endoreversible Otto cycle with the concepts of entropy generation and entransy

In this paper, the endoreversible Otto cycle is analyzed with the entropy generation minimization and the entransy theory. The output power and the heat-work conversion efficiency are taken as the optimization objectives, and the relationships of the output power, the heat-work conversion efficiency, the entropy generation rate, the entropy generation numbers, the entransy loss rate, the entransy loss coefficient, the entransy dissipation rate and the entransy variation rate associated with work are discussed. The applicability of the entropy generation minimization and the entransy theory to the analyses is also analyzed. It is found that smaller entropy generation rate does not always lead to larger output power, while smaller entropy generation numbers do not always lead to larger heat-work conversion efficiency, either. In our calculations, both larger entransy loss rate and larger entransy variation rate associated with work correspond to larger output power, while larger entransy loss coefficient results in larger heat-work conversion efficiency. It is also found that the concept of entransy dissipation is not always suitable for the analyses because it was developed for heat transfer.

Simple Power-type Heat Transfer Correlations for Turbulent Pipe Flow in Tubes

The paper presents three power-type correlations of a simple form, which are valid for Reynolds numbers range from 3.10^3 ≤ Re ≤ 10^6, and for three different ranges of Prandtl number： 0.1 ≤ Pr ≤ 1.0, 1.0≤ Pr ≤ 3.0, and 3.0 ≤Pr ≤ 10^3. Heat transfer correlations developed in the paper were compared with experimental results available in the literature. The comparisons performed in the paper confLrm the good accuracy of the proposed correlations. They are also much simpler compared with the relationship of Gnielinski, which is also widely used in the heat transfer calculations.

Spring Inserts for the Intensification of the Heat Exchange Process during Boiling in Vertical Tubes--Optimization of Geometric Parameters

The paper presents new criteria for calculation of heat transfer coefficients and flow resistance during boiling inside vertical tubes with spring inserts, developed on the basis of own experimental research. Calculations of the geometric parameters of the spring insert were carried out using the Nelder-Mead optimization method for various optimization criteria(maximizing the increase ratios for heat transfer coefficient and flow resistance, minimizing entropy, own optimization criterion). The results of optimization calculations were verified by the optimization procedures available in Statistica.

Thermal Magnifier and Minifier

For thermal conduction cases,one can detect the size of an object explicitly by measuring the temperature distribution around it.If the temperature is the only signature we can obtain,we will give an incorrect judgment on the shape or size of the object by disturbing the distribution of it.According to this principle,in this article,we develop a transformation method and design a dual-functional thermal device,which can create a thermal illusion that the object inside it ＂seems＂ to appear bigger or smaller than its original size.This device can functionally switch among magnifier and miniGer at will The proposed device consists of two layers：the cloak and the complementary material.A thermal cloak can make the internal region thermally ＂invisible＂ while the complementary layer offsets this effect.The combination leads to the illusion of magnification and minification.As a result of finite element simulations,the performances of the illusions are confirmed.