Simulation of Heat and Mass Transfer Involving Vapor Condensation in the Presence of Non-Condensable Gases in Plane Channels

2011 ◽  
Author(s):  
Mohammad Saraireh ◽  
Graham Thorpe ◽  
Jun-De Li
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Water Vapor ◽  
Heat And Mass Transfer ◽  
Cooling Water ◽  
Vapor Condensation ◽  
Transfer Coefficients ◽  
Cfd Simulations ◽  
Constant Wall Temperature ◽  
Mass Fractions

Results from computational fluid dynamics (CFD) simulations of heat and mass transfer involving the condensation of vapor in the presence of non-condensable gases in plane channels are presented. The simulations were carried out using FLUENT®. Convective heat and mass transfer and vapor condensation at a constant wall temperature were first investigated with the aim of comparing the CFD results with well established correlations. CFD simulations of heat and mass transfer and water vapor condensation in the presence of non-condensable air were then carried out for constant heat transfer coefficients for the condensation wall and coolant with different mass fractions of water vapor and inlet velocities. The predictions obtained from this are compared with experimental data and reasonable agreement has been found for the condensation rates of water vapor and heat flux. Finally, the condensation of the water vapor was simulated in a heat exchanger including both the cooling water and vapor-air mixture channels separated by solid walls. This simulation is close to reality and no assumptions are required for the temperature or heat transfer coefficient at the condensing wall. The difficulties of simultaneously simulating a gas mixture and liquid flowing in separate channels using commercially available CFD software are discussed and strategies to overcome these difficulties are outlined. Preliminary results from this third simulation will also be presented and compared with available experimental results.

Heat Transfer on Nanofluid Flow With Homogeneous–Heterogeneous Reactions and Internal Heat Generation

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Raj Nandkeolyar ◽  
Peri K. Kameswaran ◽  
Sachin Shaw ◽  
Precious Sibanda
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Generation ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Heterogeneous Reactions ◽  
Transfer Coefficients ◽  
Transfer Characteristics ◽  
Fluid Properties

We investigated heat and mass transfer on water based nanofluid due to the combined effects of homogeneous–heterogeneous reactions, an external magnetic field and internal heat generation. The flow is generated by the movement of a linearly stretched surface, and the nanofluid contains nanoparticles of copper and gold. Exact solutions of the transformed model equations were obtained in terms of hypergeometric functions. To gain more insights regarding subtle impact of fluid and material parameters on the heat and mass transfer characteristics, and the fluid properties, the equations were further solved numerically using the matlab bvp4c solver. The similarities and differences in the behavior, including the heat and mass transfer characteristics, of the copper–water and gold–water nanofluids with respect to changes in the flow parameters were investigated. Finally, we obtained the numerical values of the skin friction and heat transfer coefficients.

The Experimental Investigation of Steam Condensation With Non-Condensable Gas Under Natural Convection

2018 ◽  
Author(s):  
Xizhen Ma ◽  
Wen Fu ◽  
Haijun Jia ◽  
Peiyue Li ◽  
Jun Li
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
High Pressure ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Vertical Wall ◽  
Experimental System ◽  
Steam Condensation ◽  
Transfer Coefficients ◽  
Calculation Results

The non-condensable gas is used to keep the pressure stable in the steam-gas pressurizer. The processes of heat and mass transfer during steam condensation in the presence of non-condensable gas play an important role and the thermal hydraulic characteristics in the pressurizer is particularly complicated due to the non-condensable gas. The effects of non-condensable gas on the process of heat and mass transfer during steam condensation were experimental investigated. A steam condensation experimental system under high pressure and natural convection was built and nitrogen was chosen in the experiments. The steam and nitrogen were considered in thermal equilibrium and shared the same temperature in the vessel under natural convection. In the experiments, the factors, for instance, pressure, mass fraction of nitrogen, subcooling of wall and the distribution of nitrogen in the steam, had been taken into account. The rate of heat transfer of steam condensation on the vertical wall with nitrogen was obtained and the heat transfer coefficients were also calculated. The characteristics curve of heat and mass transfer during steam condensation with non-condensable gas under high pressure were obtained and an empirical correlation was introduced to calculated to heat transfer coefficient of steam condensation with nitrogen which the calculation results showed great agreement with the experimental data.

Heat and Mass Transfer With Liquid Evaporation Into a Turbulent Air Stream

1986 ◽  
Vol 108 (1) ◽  
pp. 4-8 ◽  
Author(s):  
T. Kumada ◽  
T. Hirota ◽  
N. Tamura ◽  
R. Ishiguro
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Enhancement Of Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Air Stream ◽  
Liquid Evaporation ◽  
Experimental Errors

Some of the previously reported heat transfer coefficients with evaporation are fairly large as compared with those of a dry body under similar hydrodynamic conditions. In order to clarify this curious enhancement of heat transfer, a method of error evaluation was developed and applied to correct the experimental errors in the recently reported results. An experimental study was also made on turbulent heat and mass transfer of air flowing over a water surface. The present and the previously reported experimental results revealed that the heat transfer coefficient with evaporation agrees with that of a dry body without evaporation, within experimental error, if the erroneous heat inputs into the liquid are properly corrected according to the proposed method.

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.

scholarly journals Heat and mass transfer in the process of heat treatment and drying of natural leather with the convective method of energy supply

2021 ◽  
Vol 66 (1) ◽  
pp. 84-92
Author(s):  
A. O. Ol’shanskii ◽  
A. M. Gusarov ◽  
S. V. Zhernosek
Keyword(s):  
Heat Transfer ◽  
Heat Treatment ◽  
Mass Transfer ◽  
Heat Conduction ◽  
Differential Equations ◽  
Heat And Mass Transfer ◽  
Analytical Solutions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Unsteady Heat Conduction

In the work, the authors investigated the possibility of using the results of analytical solutions of the linear differential equations of unsteady heat conduction with constant heat transfer coefficients to calculate the temperature of the material during heat treatment of leathers. Heat treatment of natural leathers as heat-sensitive materials is carried out under mild temperature conditions and high air moisture contents, the temperature does not undergo significant changes, and the heat transfer coefficients change almost linearly. When using analytical solutions, the authors made the assumptions that for small temperature gradients over the cross section of a thin body, the thermal transfer of matter can be neglected and for values of the heat and mass transfer Biot criteria less than unity, the main factor, limiting heat and mass transfer, is the interaction of the evaporation surface of the body with the environment; so, in solving the differential heat equation we can restrict ourselves to one first member of an infinite series. In this case, a piecewise stepwise approximation of all thermophysical characteristics with constant values of these coefficients at the calculated time intervals was applied, which made it possible to take into account the change in the transfer coefficients throughout the entire heat treatment process. Processing of experimental data showed that in low-intensity processes with reliable values of the transfer coefficients, it is possible to use the results of solutions of differential equations of unsteady heat conduction in heat transfer calculations. The results of the study of heat transfer during drying of leather confirm the laws of temperature change established experimentally. Together with experimental studies of drying processes, analytical studies are of great practical importance in the development of new methods for calculating heat and mass transfer in wet bodies.

Nanofluid Heat and Mass Transfer in a Deformable and Peristaltic Pump

2019 ◽  
Vol 8 (8) ◽  
pp. 1632-1639
Author(s):  
Aamir Ali ◽  
Y. Ali ◽  
D.N. Khan Marwat ◽  
M. Awais
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Surface Deformation ◽  
Wave Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Diffusion Parameters ◽  
Peristaltic Movement

Flow heat and mass transfer in a deformable channel of peristaltically moving walls is investigated in this paper. Moreover, the channel is filled with nanofluids. The purpose of this study is to examine the combined effects of surface deformation and peristaltic movement of the walls on the nanofluid flow in a channel. We have considered the effects of nanofluid in the peristaltically deformable porous channel whose walls are contracting or expanding in the normal direction. Nanofluids have been used to enhance the thermo-physical properties of fluids such as thermal diffusivity, thermal conductivity and convective heat transfer coefficients on flow and heat transfer. The analytic solution of the problem have been presented. We have analyzed the effects of different involved parameters such as Reynolds number, surface deformation parameter, Prandtl number, wave number, Brownian and thermophoretic diffusion parameters and Schmidt number on the velocity profile, the temperature profile, pressure distribution and the concentration profile with the help of graphs. The results are shown graphically and discussed physically. It is observed that the deformation increases the axial velocity and temperature of the fluid.

Numerical Simulations of Heat and Mass Transfer in Condensing Heat Exchangers for Water Recovery in Power Plants

2011 ◽  
Author(s):  
Kwangkook Jeong ◽  
Harun Bilirgen ◽  
Edward Levy
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Water Vapor ◽  
Sulfuric Acid ◽  
Heat Exchanger ◽  
Power Plant ◽  
Heat And Mass Transfer ◽  
Flue Gas ◽  
Cooling Water ◽  
Condensing Heat Exchanger

Power plants release a large amount of water vapor into the atmosphere through the stack. The flue gas can be a potential source for obtaining much needed cooling water for a power plant. If a power plant could recover and reuse a portion of this moisture, it could reduce its total cooling water intake requirement. One of the most practical way to recover water from flue gas is to use a condensing heat exchanger. The power plant could also recover latent heat due to condensation as well as sensible heat due to lowering the flue gas exit temperature. Additionally, harmful acids released from the stack can be reduced in a condensing heat exchanger by acid condensation. Condensation of vapors in flue gas is a complicated phenomenon since heat and mass transfer of water vapor and various acids simultaneously occur in the presence of non-condensable gases such as nitrogen and oxygen. Design of a condenser depends on the knowledge and understanding of the heat and mass transfer processes. A computer program for numerical simulations of water (H2O) and sulfuric acid (H2SO4) condensation in a flue gas condensing heat exchanger was developed using MATLAB. Governing equations based on mass and energy balances for the system were derived to predict variables such as flue gas exit temperature, cooling water outlet temperature, mole fraction and condensation rates of water and sulfuric acid vapors. The equations were solved using an iterative solution technique with calculations of heat and mass transfer coefficients and physical properties. An experimental study was carried out in order to yield data for validation of modeling results. Parametric studies for both modeling and experiments were performed to investigate the effects of parameters such as flue gas flow rate, cooling water flow rate, inlet cooling water temperature and tube configurations (bare and finned tubes) on condensation efficiency. Predicted results of water and sulfuric acid vapor condensation were compared with experimental data for model validation, and this showed agreement between experimental data and predictions to within a few percent. The most important parameters affecting performance of the condensing heat exchangers was the ratio of cooling water to flue gas flow rates, since this determines how much heat the cooling water can absorb. The computer program simultaneously calculates both water vapor condensation and sulfuric acid condensation in flue gas along downstream. Modeling results for prediction of sulfuric acid vapor concentration in the flue gas were compared with measured data obtained by the controlled condensation method. An analytical model of sulfuric acid condensation for oil-firing showed two trends — steep reduction within the high temperature heat exchanger and smooth reduction within lower temperature heat exchanger, which is in agreement with experimental data.

Enhancement of Combined Heat and Mass Transfer in a Vertical-Tube Heat and Mass Exchanger

1986 ◽  
Vol 108 (1) ◽  
pp. 70-75 ◽  
Author(s):  
R. L. Webb ◽  
H. Perez-Blanco
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Mass Transfer ◽  
Water Film ◽  
Vertical Tube ◽  
Transfer Coefficients ◽  
Interface Heat Transfer ◽  
Friction Performance ◽  
Predicted Values

This paper studies enhancement of heat and mass transfer between a countercurrent, gravity-drained water film and air flowing in a vertical tube. The enhancement technique employed is spaced, transverse wires placed in the air boundary layer, near the air-water interface. Heat transfer correlations for turbulent, single-phase heat transfer in pipes having wall-attached spaced ribs are used to select the preferred wire diameter, and to predict the gas phase heat and mass transfer coefficients. Tests were run with two different radial placements of the rib roughness: (1) at the free surface of the liquid film, and (2) the base of the roughness displaced 0.51 mm into the air flow. The authors hypothesize that the best heat/mass transfer and friction performance will be obtained with the roughness at the surface of the water film. Experiments conducted with both roughness placements show that the authors’ hypothesis is correct. The measured heat/mass transfer enhancement agreed very closely with the predicted values. A unique feature of the enhancement concept is that it does not require surface wetting of the enhancement device to provide enhancement.

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