Turbulent Flow, Heat Transfer, and Mass Transfer in a Tube With Surface Suction

1970 ◽  
Vol 92 (1) ◽  
pp. 117-124 ◽  
Author(s):  
R. B. Kinney ◽  
E. M. Sparrow
Keyword(s):  
Mass Transfer ◽  
Transverse Velocity ◽  
Turbulent Transport ◽  
Turbulent Pipe Flow ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Noncondensable Gases ◽  
Axial Pressure Gradient ◽  
Flow Heat ◽  
Impermeable Boundary

The problem of turbulent pipe flow with mass removal at the bounding surface is analyzed, and numerical results are presented for the friction factor, axial pressure gradient, heat and mass transfer coefficients, and velocity and temperature profiles. The results, which are relevant to forced-convection condensation in a tube (either with or without noncondensable gases) are shown to be substantially affected by even small amounts of wall suction. Therefore, the present findings do not support the current practice of using impermeable-boundary transfer coefficients in condensation calculations. The analysis is performed under the condition that the velocity field is locally self-similar. Corresponding conditions are used for the distributions of temperature and mass fraction. The cross-sectional distributions of the transverse velocity and the shear stress are not constrained in advance, but rather, are permitted to vary in accordance with the conservation laws. The turbulent transport is expressed in terms of the mixing-length, model, modified in the neighborhood of the wall by a specially derived dumping factor.

Diffusion Layer Theory for Turbulent Vapor Condensation With Noncondensable Gases

1993 ◽  
Vol 115 (4) ◽  
pp. 998-1003 ◽  
Author(s):  
P. F. Peterson ◽  
V. E. Schrock ◽  
T. Kageyama
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Transfer ◽  
Vapor Condensation ◽  
Sensible Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Noncondensable Gas ◽  
Noncondensable Gases ◽  
Vertical Tubes

In turbulent condensation with noncondensable gas, a thin noncondensable layer accumulates and generates a diffusional resistance to condensation and sensible heat transfer. By expressing the driving potential for mass transfer as a difference in saturation temperatures and using appropriate thermodynamic relationships, here an effective “condensation” thermal conductivity is derived. With this formulation, experimental results for vertical tubes and plates demonstrate that condensation obeys the heat and mass transfer analogy, when condensation and sensible heat transfer are considered simultaneously. The sum of the condensation and sensible heat transfer coefficients becomes infinite at small gas concentrations, and approaches the sensible heat transfer coefficient at large concentrations. The “condensation” thermal conductivity is easily applied to engineering analysis, and the theory further demonstrates that condensation on large vertical surfaces is independent of the surface height.

Study of CO2 Absorption Into Aqueous Diethanolamine (DEA) Using Microchannel Reactors

2014 ◽  
Author(s):  
Stefan Bangerth ◽  
Harish Ganapathy ◽  
Michael Ohadi ◽  
Tariq S. Khan ◽  
Mohamed Alshehhi
Keyword(s):  
Mass Transfer ◽  
Carbon Capture And Storage ◽  
Liquid Product ◽  
Interfacial Area ◽  
Co2 Absorption ◽  
Transfer Coefficients ◽  
Major Step ◽  
Component Level ◽  
Cross Sectional ◽  
Absorption Performance

Removal of CO2 from gas streams is a major step in the purification of natural gas and of interest for carbon capture and storage applications. Industrial scale implementations of the process with most state of the art technologies use aqueous alkanolamines as liquid solvents to chemically absorb CO2. Although the kinetics of the absorption process are fast, sufficient absorption performance can only be met by very large columns due to the limited interfacial area present between gas and liquid phases in these systems. In the present study we utilize micro structure surfaces in two-phase regime to provide substantially higher interfacial area and hence enhanced mass transfer characteristics. We report experimental data on the separation of CO2 from a gas stream containing 10% CO2 and 90% N2 by volume. An aqueous solution of 20% diethanolamine in water by weight was used as the solvent, and absorption performance was measured by potentiometric titration of the liquid product with potassium hydroxide. The microchannel-based reactors had circular cross-sectional geometry with an inner diameter of 762 μm and two different lengths of 10 cm and 30 cm. Additionally, blank experiments were performed for component-level analysis. Parametric studies varying the gas and liquid phase superficial velocities were conducted and discussed. The potential to use microchannel reaction systems in multiple pass configurations for scaled up implementation was investigated. The present work achieved mass transfer coefficients that are at least one order of magnitude higher than those of most conventional absorption technologies, thus indicating the substantial process intensification that can be achieved using the proposed microreactor system for CO2 separation processes.

The Corresponding Relationship Between Heat, Mass Transfer Coefficients and the Flow Regime in Dual-Contact-Flow Absorption Tower

2011 ◽  
Author(s):  
Yafei Zhang ◽  
Qulan Zhou ◽  
Yi Zhang ◽  
Qinxin Zhao ◽  
Shi’en Hui
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Heat And Mass Transfer ◽  
Flow Regimes ◽  
Transition Process ◽  
Gas Velocity ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Flow Type ◽  
Flow Heat

The flow, heat and mass transfer performance under different nozzle arrays in the dual-contact-flow absorption tower has been studied, together with the interrelation between the probability dense function (PDF) and the flow, heat and mass transfer characteristics. The experimental results show that, for the same nozzle array, both the heat and mass transfer coefficients (h and hm) increase with the gas velocity increasing at first; However, both coefficients (h and hm) start to decrease due to the reduction of the liquid-gas contact time after approaching a certain extent. Moreover, with the increase of liquid injection rate νp0, the two coefficients (h and hm) decrease, while the total heat and mass transfer values rise. In addition, the mass transfer coefficient decrease with the increase of nozzle number. In the absorption tower, the leading role gradually transfers to gas phase from liquid phase with the increase of gas velocity. The flow regimes’ transition process can be explained as follows: the liquid column flow type, the liquid screen flow type, the convergent liquid screen flow type, and the gasping flow type. Moreover, the increase of gas velocity has effects on the probability dense function (PDF). With the flow regimes’ transition, change of PDF performs as follows: the number of the PDF peaks increases from one to a larger quantity and finally decreases to a single one after that; the average pressure drop ΔPmean increases as well as the peak-peak spacing δpeak. However, the pressure drop distribution range lΔP first increases and then decreases.

New Correlative Models for Fully Developed Turbulent Heat and Mass Transfer in Circular and Noncircular Ducts

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Zhipeng Duan
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Turbulent Transport ◽  
Cross Sectional Area ◽  
Turbulent Heat ◽  
Square Root ◽  
Sectional Area ◽  
Cross Sectional ◽  
Dimensionless Parameters ◽  
Simple Models

Fully developed turbulent flow in noncircular ducts is examined, and simple models are proposed to predict the friction, heat and mass transfer in most common noncircular channels. It is found that the square root of cross-sectional area is the relatively more appropriate length scale to use in defining the dimensionless parameters to ensure similarity between the circular and most noncircular ducts. By using the dimensionless parameters based on the square root of cross-sectional area, it is demonstrated that the circular tube relations may be applied to most noncircular ducts eliminating large errors in estimation. As turbulent transport phenomena are inherently complex and there, currently, is no extensive experimental data for turbulent heat and mass transfer in noncircular ducts, the simple models are valuable in spite of their limitations.

Heat Transfer and Pressure Drop Characteristics Induced by a Slat Blockage in a Circular Tube

1980 ◽  
Vol 102 (1) ◽  
pp. 64-70 ◽  
Author(s):  
E. M. Sparrow ◽  
K. K. Koram ◽  
M. Charmchi
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Pipe Flow ◽  
Turbulent Pipe Flow ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Flow Experiments

Complementary heat transfer and fluid flow experiments were performed to determine transfer coefficients and pressure drops associated with the presence of a slat-like blockage in a tube. Water was the working fluid for the heat transfer studies (Pr = 4), while for the fluid flow experiments, which were performed under isothermal conditions, air was employed. The flow was turbulent in all cases, with the Reynolds number ranging from 10,000 to 60,000. Three blockage elements were used which respectively blocked 1/4, 1/2, and 3/4 of the tube cross-sectional area. Downstream of the blockage, heat transfer coefficients were measured around the circumference of the tube as well as along its length. The heat transfer coefficients in the region just downstream of the blockage were found to be several times as large as those for a corresponding conventional turbulent pipe flow. With increasing downstream distance, the coefficients diminish and thermal development is completed (to within five percent) at about 10, 15, and 18 diameters from the respective blockages. The blockage-induced circumferential variations of the heat transfer coefficient are dissipated by about five diameters. The pressure losses induced by the blockage are high, with values for the respective blockages that are 1.2, 5.2, and 33.2 times the velocity head in the pipe flow in which the blockage is situated. These losses are comparable to those for a gate valve.

Measurements of Airway Dimensions and Calculation of Mass Transfer Characteristics of the Human Oral Passage

1997 ◽  
Vol 119 (4) ◽  
pp. 476-482 ◽  
Author(s):  
K.-H. Cheng ◽  
Y.-S. Cheng ◽  
H.-C. Yeh ◽  
D. L. Swift
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Oral Cavity ◽  
Ultrafine Particles ◽  
Empirical Relationship ◽  
Aerosol Deposition ◽  
Transfer Coefficients ◽  
Upper Airways ◽  
Cross Sectional ◽  
Flow Rates

This paper presents measurements of the geometric shape, perimeter, and cross-sectional area of the human oral passage (from oral entrance to midtrachea) and relates them through dimensionless parameters to the depositional mass transfer of ultrafine particles. Studies were performed in two identical replicate oral passage models, one of which was cut orthogonal to the airflow direction into 3 mm elements for measurement, the other used intact for experimental measurements of ultrafine aerosol deposition. Dimensional data were combined with deposition measurements in two sections of the oral passage (the horizontal oral cavity and the vertical laryngeal–tracheal airway) to calculate the dimensionless mass transfer Sherwood number (Sh). Mass transfer theory suggests that Sh should be expressible as a function of the Reynolds numper (Re) and the Schmidt number (Sc). For inhalation and exhalation through the oral cavity (O-C), an empirical relationship was obtained for flow rates from 7.5–30.0 1 min−1: Sh=15.3Re0.812Sc−0.986 An empirical relationship was likewise obtained for the laryngeal–tracheal (L-T) region over the same range of flow rates: Sh=25.9Re0.861Sc−1.37 These relationships were compared to heat transfer in the human upper airways through the well-known analogy between heat and mass transfer. The Reynolds number dependence for both the O-C and L-T relationships was in good agreement with that for heat transfer. The mass transfer coefficients were compared to extrathoracic uptake of gases and vapors and showed similar flow rate dependence. For gases and vapors that conform to the zero concentration boundary condition, the empirical relationships are applicable when diffusion coefficients are taken into consideration.

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