Modeling Liquid Film Evaporation in a Wetted Wall Bioaerosol Sampling Cyclone

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
J. A. Hubbard ◽  
O. A. Ezekoye ◽  
J. S. Haglund
Keyword(s):  
Mass Transfer ◽  
Relative Humidity ◽  
Multiphase Flow ◽  
Heat And Mass Transfer ◽  
Nonlinear Dependence ◽  
Model Parameters ◽  
Empirical Correlations ◽  
Lab On Chip ◽  
Film Evaporation ◽  
Semi Empirical

The wetted wall bioaerosol sampling cyclone (WWC) is a complex multiphase flow device which collects and concentrates dilute bioaerosols into liquid samples for biological analysis (McFarland et al., 2009, “Wetted Wall Cyclones for Bioaerosol Sampling,” Aerosol Sci. Technol., 44(4), pp. 241–252). Understanding heat and mass transfer processes occurring inside the WWC is the key to enhancing its performance through an effective coupling to lab-on-chip analysis platforms which require small volumes of liquid output. There exists a critical liquid input rate below which there is no sample collection since all liquid is lost to evaporative effects. The purpose of this study was to model critical film evaporation based on first principles and develop semi-empirical WWC performance correlations as an improvement to existing empirical correlations. A one-dimensional, coupled heat and mass transfer model was developed approximating WWC multiphase flow as cocurrent air-film flow. Governing equations were simplified and approximate solutions were used to optimize model parameters like the heat transfer coefficient based on empirical data from previous works. Optimized model parameters were then used in the full numerical solution to calculate liquid evaporation rates within the WWC over the full range of relative humidity and air temperature. Semi-empirical correlations developed in this study were compared to existing empirical models and showed much improvement: proper physical behavior at the extreme limits of temperature and relative humidity was observed, and the nonlinear dependence of evaporative effects on environmental conditions was also captured.

scholarly journals ANALYSIS OF HEAT AND MASS TRANSFER ON COOLING TOWER FILL

2020 ◽  
Vol 14 (1) ◽  
pp. 25
Author(s):  
Abdul Aziz Rohman Hakim ◽  
Engkos Achmad Kosasih
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Relative Humidity ◽  
Heat And Mass Transfer ◽  
Cooling Tower ◽  
Stream Velocity ◽  
Design Data ◽  
Analogy Method ◽  
Ambient Relative Humidity ◽  
Air Stream

This paper discusses heat and mass transfer in cooling tower fill. In this research, dry bulb temperature at the bottom fill, ambient relative humidity, air stream velocity entering fill, dry bulb temperature leaving the fill, relative humidity of air leaving the fill, inlet and outlet water temperature of cooling tower were measured. Those data used in heat and mass transfer calculation in cooling tower fill. Then, do the heat and mass transfer calculation based on proposed approch. The results are compared with design data. The design and analogy method showed different  result. The parameter which influence the heat transfer at cooling tower are represented by coefficient of heat transfer hl and coefficient of mass transfer k­l. The differencies result between design and analogy method shows that there is important parameter which different. Deeply study needed for it.

scholarly journals Performance Assessment of an NH3/LiNO3 Bubble Plate Absorber Applying a Semi-Empirical Model and Artificial Neural Networks

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4313
Author(s):  
Carlos Amaris ◽  
Maria E. Alvarez ◽  
Manel Vallès ◽  
Mahmoud Bourouis
Keyword(s):  
Neural Networks ◽  
Mass Transfer ◽  
Artificial Neural Networks ◽  
Heat And Mass Transfer ◽  
Empirical Model ◽  
Mass Flux ◽  
Ann Model ◽  
Artificial Neural ◽  
Semi Empirical ◽  
Plate Absorber

In this study, ammonia vapor absorption with NH3/LiNO3 was assessed using correlations derived from a semi-empirical model, and artificial neural networks (ANNs). The absorption process was studied in an H-type corrugated plate absorber working in bubble mode under the conditions of an absorption chiller machine driven by low-temperature heat sources. The semi-empirical model is based on discretized heat and mass balances, and heat and mass transfer correlations, proposed and developed from experimental data. The ANN model consists of five trained artificial neurons, six inputs (inlet flows and temperatures, solution pressure, and concentration), and three outputs (absorption mass flux, and solution heat and mass transfer coefficients). The semi-empirical model allows estimation of temperatures and concentration along the absorber, in addition to overall heat and mass transfer. Furthermore, the ANN design estimates overall heat and mass transfer without the need for internal details of the absorption phenomenon and thermophysical properties. Results show that the semi-empirical model predicts the absorption mass flux and heat flow with maximum errors of 15.8% and 12.5%, respectively. Maximum errors of the ANN model are 10.8% and 11.3% for the mass flux and thermal load, respectively.

scholarly journals Computational Study of Liquid Film Evaporation along a Wavy Wall of a Vertical Channel

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Monssif Najim ◽  
M’barek Feddaoui ◽  
Abderrahman Nait Alla ◽  
Adil Charef
Keyword(s):  
Mass Transfer ◽  
Liquid Film ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Computational Study ◽  
Vertical Channel ◽  
Wavy Wall ◽  
Gas Phases ◽  
Multiple Parameters ◽  
Film Evaporation

A numerical study of mixed convection heat and mass transfer along a vertical channel with a wavy wall is performed. The wavy wall is heated by a constant flux, while the other is adiabatic. The discretisation of equations in both liquid and gas phases is realised using an implicit finite difference scheme. Results of simulation compare the effect of multiple parameters, especially amplitude and characteristic length of the curve, on the liquid film evaporation process. The results indicate that heat and mass transfer is enhanced by increasing the amplitude and number of wall waves. Moreover, a very small value of waves amplitude of the wall may reduce the sensible heat and mass transfer.

Sign in / Sign up

Export Citation Format

Share Document