Analysis of Fouling Characteristic in Enhanced Tubes Using Multiple Analogies

2010 ◽  
Author(s):  
Wei Li ◽  
Guanqiu Li ◽  
Zhengjiang Zhang ◽  
Zhiming Xu ◽  
Shanrang Yang
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat Flux ◽  
Transfer Coefficient ◽  
Cooling Tower ◽  
Comprehensive Analysis ◽  
Von Karman ◽  
Enhanced Tubes ◽  
Plain Tube ◽  
Von Kármán

This paper provides a comprehensive analysis on cooling tower fouling data taken from seven 15.54 mm I.D. helically ribbed, copper tubes and a plain tube at Re = 16000. A new mathematical model has been developed. The mass transfer coefficient Km is calculated through three analogies, which are Prandtl analogy, Von-Karman analogy, and j factor analogy. Fouling deposition is assumed to be determined by two processes, which are corresponding to heat flux and fluid friction. Von-Karman analogy is proved the best analogy among the three. Series of semi-theoretical fouling correlations as a function of the product of area indexes and efficiency indexes were developed. They were applicable to different internally ribbed geometries. The correlations can be directly used to assess the fouling potential of enhanced tubes in actual cooling tower water situations.

Performance of the volumetric mass transfer coefficient in a cooling tower

2018 ◽  
Vol 11 (41) ◽  
pp. 1999-2006
Author(s):  
Jorge Duarte Forero ◽  
Guillermo Valencia Ochoa ◽  
Luis Obregon Quinones
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Cooling Tower ◽  
Volumetric Mass Transfer Coefficient

scholarly journals Performance of a Cooling Tower with the Use of a New Kind of High-density Polyethylene (HDPE) Packing

2021 ◽  
Author(s):  
Nagam Obaid Kariem ◽  
◽  
Mohammed A. Rasheed ◽  
Zainab T. Al-Sharify ◽  
◽  
...  
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Water Flow ◽  
High Density Polyethylene ◽  
Cooling Tower ◽  
Water Flow Rate ◽  
Research Work ◽  
High Density ◽  
Airflow Rate ◽  
Flow Rates

This research work deals with the performance of high-density polyethylene sheets arranged in splash used as a fill for a cooling tower. “A forced-draught counter flow cooling tower” of 400 mm × 400 mm cross-sectional area and 1.7m in height was built. The fill has been studied theoretically and experimentally. Air rates of 0.6, 1.2, and 1.8 kg/s.m2 were utilized with water flow rates within the range of 1 to 1.6 kg/s.m2. The overall volumetric heat transfer coefficient, volumetric mass transfer coefficient (Mt), and the tower characteristics (Mt/L) are shown to be functions of the air and water flow rates concurrently. Four available input parameters were inlet water temperature, airflow rate, water flow rate, and full height. A computer program was prepared to perform numerical analysis for reducing data sets obtained from the plant. In addition, analysis was carried out for evaluating the volumetric heat and mass transfer coefficients along with the performance coefficient.

scholarly journals Development of Modified Incompressible Ideal Gas Model for Natural Draft Cooling Tower Flow Simulation

2018 ◽  
Vol 180 ◽  
pp. 02037
Author(s):  
Tomáš Hyhlík
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Cooling Tower ◽  
Flow Simulation ◽  
Ideal Gas ◽  
Specific Humidity ◽  
Boussinesq Model ◽  
Natural Draft ◽  
Ideal Gas Model

The article deals with the development of incompressible ideal gas like model, which can be used as a part of mathematical model describing natural draft wet-cooling tower flow, heat and mass transfer. It is shown, based on the results of a complex mathematical model of natural draft wet-cooling tower flow, that behaviour of pressure, temperature and density is very similar to the case of hydrostatics of moist air, where heat and mass transfer in the fill zone must be taken into account. The behaviour inside the cooling tower is documented using density, pressure and temperature distributions. The proposed equation for the density is based on the same idea like the incompressible ideal gas model, which is only dependent on temperature, specific humidity and in this case on elevation. It is shown that normalized density difference of the density based on proposed model and density based on the nonsimplified model is in the order of 10-4. The classical incompressible ideal gas model, Boussinesq model and generalised Boussinesq model are also tested. These models show deviation in percentages.

scholarly journals Characteristics of supercritical heat transfer during filmboiling of nanofluids on a vertical heated wall

2018 ◽  
pp. 29-35
Author(s):  
А. Avramenko ◽  
M. Kovetskaya ◽  
A. Tyrinov ◽  
Yu. Kovetska
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Mass Transfer ◽  
Heat Flux ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Heated Surface ◽  
Heated Wall ◽  
Film Boiling

Nanofluid using for intensification of heat transfer during boiling are analyzed. The using boiling nanofluids for cooling high-temperature surfaces allows significantly intensify heat transfer process by increasing the heat transfer coefficient of a nanofluid in comparison with a pure liquid. The properties of nanoparticles, their concentration in the liquid, the underheating of the liquid to the saturation temperature have significant effect on the rate of heat transfer during boiling of the nanofluid. Increasing critical heat flux during boiling of nanofluids is associated with the formation of deposition layer of nanoparticles on heated surface, which contributes changing in the microcharacteristics of heat exchange surface. An increase in the critical heat flux during boiling of nanofluids is associated with the formation of a layer of deposition of nanoparticles on the surface, which contributes to a change in the microcharacteristics of the heat transfer of the surface. Mathematical model and results of calculation of film boiling characteristics of nanofluid on vertical heated wall are presented. It is shown that the greatest influence on the processes of heat and mass transfer during film boiling of the nanofluid is exerted by wall overheating, the ratio of temperature and Brownian diffusion and the concentration of nanoparticles in the liquid. The mathematical model does not take into account the effect changing structure of the heated surface on heat transfer processes but it allows to evaluate the effect of various thermophysical parameters on intensity of deposition of nanoparticles on heated wall. The obtained results allow to evaluate the effect of nanofluid physical properties on heat and mass transfer at cooling of high-temperature surfaces. The using nanofluids as cooling liquids for heat transfer equipment in the regime of supercritical heat transfer promotes an increase in heat transfer and accelerates the cooling process of high-temperature surfaces. Because of low thermal conductivity of vapor in comparison with the thermal conductivity of the liquid, an increase in the concentration of nanoparticles in the vapor contributes to greater growth in heat transfer in the case of supercritical heat transfer.

Research on Mass Transfer Coefficient Measurement Model of External-Loop Airlift Reactor

2012 ◽  
Vol 512-515 ◽  
pp. 2405-2411
Author(s):  
Qian Wu ◽  
Ma Lin Liu ◽  
Tong Wang Zhang
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Measurement Model ◽  
Airlift Reactor ◽  
Continuous Stirred Tank Reactor ◽  
Volumetric Mass Transfer Coefficient ◽  
External Loop ◽  
Coefficient Measurement

A mathematical model considering the inter-phase mass transfer both in the down-comer and the riser of an external-loop airlift reactor was established in this paper. The calculated global volumetric mass transfer coefficient based on the assumption of continuous stirred tank reactor (CSTR) was different from the local volumetric mass transfer coefficients by the newly proposed mathematical model and the difference was discussed. The effects of mass transfer in the down-comer, the hydrodynamic pressure and the experimental time on the mass transfer coefficient measurement model have been studied in detail. And it was also proved that only the global volumetric mass transfer coefficient, but not the local volumetric mass coefficient, can be obtained from a time-concentration curve in the external-loop airlift reactor.

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