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在φ500 mm×5000 mm的冷模实验装置中,使用自制传热探头,对无内构件的空塔和安装31根竖直换热列管的鼓泡塔内列管传热系数进行了测量.实验表明,列管传热系数随表观气速的增加而增大,传热系数沿径向呈抛物型分布,垂直列管内构件的加入使得传热系数的径向分布变得更为陡峭.基于表面更新理论,结合鼓泡塔内气含率和液速分布的测量及计算结果,提出了计算传热系数的数学模型.该模型既可以用于空塔的局部传热系数与平均传热系数计算,也可以用于安装列管束的局部传热系数与平均传热系数计算.模型计算值与实验数据符合良好,最大相对误差为5.62%. 相似文献
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采用挤条型催化剂载体Al2O3和合成氨铁系催化剂为填充物,以空气为介质,在床层被冷却的情况下,研究固定床中内置圆管被冷却的错流传热。被冷却床层中的等温线是以流动方向为长轴的椭圆形曲线,被冷却的区域主要在换热管的后方,其前方几乎没有影响。错流传热过程与流体流动方向密切相关,床层被冷却时,热量传递是逆流体流动方向进行,顺流动方向几乎不发生热量传递。得到了气体雷诺数为10-220,床径/粒径为3~15条件下填充低导热系数颗粒和高导热系数颗粒床层的传热关联式。 相似文献
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Boiling of water/triethyleneglycol (TEG) binary solution has a wide-ranging application in the gas processing engineering. Design, operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution. In this investigation, nucleate pool boiling heat transfer coef-ficient has been experimentally measured on a horizontal rod heater in water/TEG binary solutions in a wide range of concentrations and heat fluxes under ambient condition. The present experimental data are correlated using major existing correlations. In addition a correlation is presented for prediction of pool boiling heat transfer for the system in which the vapour pressure of one component is negligible. This model is based on the mass transfer rate equation for prediction of the concentration at the bubble vapor/liquid interface. Based on this prediction, the temperature of the interface and accordingly, the boiling heat transfer coefficient could be straightforwardly calculated from the known concentration at the interface. It is shown that this simple model has sufficient accuracy and is acceptable below the medium concentrations of TEG when the vapor equilibrium concentration of TEG is almost zero. The presented model excludes any tuning parameter and requires very few physical properties to apply. 相似文献
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The effects of drying parameters on heat transfer during drying of fermented ground cassava in a rotary dryer were studied. The fermented ground cassava was dried in a bench-scale rotary dryer at different inlet air temperatures, inlet air velocities, relative humidities, feed rates, drum drive speeds, and feed drive speeds. It is shown that inlet air temperature, inlet air velocity, and feed rate have significant effects on the specific heat transfer coefficient and heat load in the material. Models that predict the specific heat transfer coefficient as a function of inlet air temperature and inlet air velocity and the heat load as a function of inlet air temperature, inlet air velocity, and feed rate are also presented. Predictions of the models are compared with experimental data and good agreement is obtained. 相似文献
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In literature, there are several Nu=f(Re) equations to specify the heat transfer coefficient between solids and the drying gas, but these equations differ significantly because of the inaccuracy of determining the contact surface between the two phases. A pilot‐plant fluidized‐bed dryer is developed to study the heat and mass transfer phenomena during the drying process. A volumetric heat transfer coefficient is applied for modeling fluidized‐bed dryers. A modified Nusselt number is defined to compare the experimental results and those of the literature. The modified Nu'=f(Re) equation exhibits a proper correlation between the results of the experiments in the literature and those of our experiments. 相似文献
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分析了搅拌塔式反应器(SCR)中多级冷却盘管隔板的传热特性,用稳态和非稳态的传热方法进行了实验研究。提出了同时考察拌雷诺数和轴向液流雷诺数影响的SCR中多级冷却盘管隔板表面传热膜系数的关联式。研究结果表明,对于SCR中冷却盘管隔板表面的传热膜系数,轴向液轩诺系数的影响与搅拌雷诺数的影响相比具有同等的重要性。 相似文献
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A simple experimental approach was developed to measure the gas phase volumetric heat and mass transfer coefficients in a bubble column and a slurry bubble column employing a single gas nozzle. The experimental technique was based on a transfer model that simulates humidification and direct contact evaporation models in the case of a gas bubble rising in a liquid of uniform temperature. The temperature and relative humidity of the inlet and outlet gas in the column are the only measurements required in this technique. Experiments were carried out in a 0.15 m inner diameter column using water as the liquid phase, air as the gas phase, and cation resins of 0.1 mm diameter and a specific gravity of 1.2, as the solid phase. The results showed that, when using solid concentrations in the range of 7–10 wt %, both the volumetric gas‐phase heat and mass transfer coefficients increased with an increase in the gas superficial velocity and were further enhanced by increasing the solid load after a certain minimum superficial velocity had been reached in the column (0.044 m/s in the system used). Increasing the solid load beyond 10 wt %, did not contribute to a further increase in these coefficients. Furthermore, the gas holdup in the column increased with the superficial gas velocity and was further enhanced when the solid‐phase load was in the range of 7–10 wt %. These observations agree well with previously reported findings by other investigators. 相似文献
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垂直管内不互溶液滴群直接接触汽化传热 总被引:2,自引:0,他引:2
在一气升式外循环实验设备中研究了冷剂正戊烷与热流体水在垂直管内直接接触汽化传热过程。根据单液滴不互溶冷剂汽化关联式,推导出多液滴汽化过程中局部和平均体积传热系数表达式,表达式较好地解释了实验结果。讨论了冷剂表观流速、冷剂与热流体间的传热温差对体积传热量qv和体积传热系数av的影响;以及冷剂表观流速对冷却温差的影响。 相似文献
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振动流化床与浸没水平管间局部传热系数的测试方法 总被引:3,自引:0,他引:3
本文提出了振动流化床中测试水平加热管局部传热系数的新方法。该法考虑了管体温度场的非均匀性对测量结果的影响。根据管体的材质和结构。扣除了由于分布引起热损失。从而采用较简单的测试手段就能够获得较准确的局部传热系数数据。将本所所得测试结果与其他研究者的测试结果作了比较。并上局部热系数求得的平均传热系数和实测的平均传热作了比较。结果表明,本文提出的测试方法可靠。 相似文献
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The heat transfer and pressure drop in a thermoplate heat exchanger operating as a condenser have been investigated experimentally. In order to separate the heat transfer resistances in the condensation process, the single phase forced convection has been studied using distilled water and Marlotherm oil in the thermoplate and correlations developed for the Nusselt number and the friction factor. For the condensation experiments, an apparatus has been constructed comprising two identical condensers composed of the same thermoplate type as employed in the single phase experiments. Isopropanol is used as a test fluid at pressures below atmospheric pressure. The heat transfer resistances in the condensation experiments are separated and expressions for the condensation heat transfer and pressure drop are developed with the aid of the results obtained in the single phase studies. 相似文献
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水平矩形散热片的流动特性及传热性能 总被引:3,自引:0,他引:3
水平矩形散热片的流动特性及传热性能沈文生陈烈强(华南理工大学,广州510641)梁振华梁天培(香港理工大学)关键词散热片速度分布传热系数1前言作为强化传热元件之一的散热片因制造方便、结构简单及传热效率高而广泛地应用于许多工程系统,例如电子设备、热电设... 相似文献
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Dongsheng Wen 《Chemical engineering science》2006,61(11):3532-3542
This paper reports an experimental study of both the transient and steady-state heat transfer behaviour of a gas flowing through a packed bed under the constant wall temperature conditions. Effective thermal conductivities and convective heat transfer coefficient are derived based on the steady-state measurements and the two-dimensional axial dispersion plug flow (2DADPF) model. The results reveal a large temperature drop at the wall region and the temperature drop depends on the axial distance from the inlet. The 2DADPF model predicts the axial temperature distribution fairly well, but the prediction is poor for the radial temperature distribution. Length-dependent behaviour of the effective heat transfer parameters and non-uniform flow behaviour are proposed to be responsible. A comparison with previously published correlations and data in the literature shows that the relationships proposed by Bunnell et al. and Demirel et al. agree well with the measured effective radial thermal conductivity, whereas the wall-fluid heat transfer coefficient is better represented by the Li-Finlayson correlation. 相似文献