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.

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.

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

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.

Local Heat/Mass Transfer Characteristics on a Rotating Blade With Flat Tip in a Low-Speed Annular Cascade—Part II: Tip and Shroud

2005 ◽  
Vol 128 (1) ◽  
pp. 110-119 ◽  
Author(s):  
Dong-Ho Rhee ◽  
Hyung Hee Cho
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Flow Velocity ◽  
Rotational Speed ◽  
Heat Mass Transfer ◽  
Local Heat ◽  
Incoming Flow ◽  
Transfer Coefficients ◽  
Low Speed ◽  
Annular Cascade

The local heat/mass transfer characteristics on the tip and shroud were investigated using a low speed rotating turbine annular cascade. Time-averaged mass transfer coefficients on the tip and shroud were measured using a naphthalene sublimation technique. A low speed wind tunnel with a single stage turbine annular cascade was used. The turbine stage is composed of sixteen guide plates and blades. The chord length of blade is 150 mm and the mean tip clearance is about 2.5% of the blade chord. The tested Reynolds number based on inlet flow velocity and blade chord is 1.5×105 and the rotational speed of the blade is 255.8 rpm at design condition. The results were compared with the results for a stationary blade and the effects of incidence angle of incoming flow were examined for incidence angles ranging from −15 to +7deg. The off-design test conditions are obtained by changing the rotational speed with a fixed incoming flow velocity. Flow reattachment on the tip near the pressure side edge dominates the heat transfer on the tip surface. Consequently, the heat/mass transfer coefficients on the blade tip are about 1.7 times as high as those on the blade surface and the shroud. However, the heat transfer on the tip is about 10% lower than that for the stationary case due to reduced leakage flow with the relative motion. The peak regions due to the flow reattachment are reduced and shifted toward the trailing edge and additional peaks are formed near the leading edge region with decreasing incidence angles. But, quite uniform and high values are observed on the tip with positive incidence angles. The time-averaged heat/mass transfer on the shroud surface has a level similar to that of the stationary cases.

Heat and Mass Transfer Analogy of Steam Condensation With Air Over Vertical External Surface

2016 ◽  
Author(s):  
Jiqiang Su ◽  
Yuxiang Wu ◽  
Shuliang Huang ◽  
Huiqiang Xu ◽  
Yanmin Zhou
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
External Surface ◽  
Vertical Tube ◽  
External Diameter ◽  
Thermodynamic Process ◽  
Layer Model ◽  
Steam Condensation ◽  
Predicted Values

During the steam condensation, the presence of non-condensable gases is an important issue affecting the efficiency of the whole thermodynamic process. For this reason, many researchers investigated it by theoretical or experimental methods. A heat and mass transfer analogy model on steam condensation in presence of air over the vertical external surface based on the diffusion layer model is modified in the present paper. Based on previous authors’ experience, the suction effect at the gas-liquid interface and other analogy drawbacks are identified and overcome by supplementing it with more detailed analysis as well as targeted experiments. The experimental data obtained for condensation, outside vertical tube with an external diameter of 38 mm, of air/steam and helium/air/steam mixture, have been used to verify the present heat and mass transfer analogy formulation. By comparing against different available experimental data and previous formulations, the heat and mass transfer analogy formulation is demonstrated to be a accurate enough theoretical approximation. The deviation between predicted values of the new model and experiment results of this paper is less than 15% which has relative higher precision.

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.

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