Local evaporative heat transfer coefficient in turbulent free-falling liquid films

1988 ◽  
Vol 31 (4) ◽  
pp. 731-742 ◽  
Author(s):  
J.A. Shmerler ◽  
I. Mudawwar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Liquid Films ◽  
Evaporative Heat Transfer ◽  
Evaporative Heat Transfer Coefficient ◽  
Falling Liquid Films ◽  
Free Falling

Heat Transfer Analysis of Local Evaporative Turbulent Falling Liquid Films

1992 ◽  
Vol 114 (3) ◽  
pp. 688-694 ◽  
Author(s):  
N. M. Al-Najem ◽  
K. Y. Ezuddin ◽  
M. A. Darwish
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Homogeneous Problem ◽  
Interfacial Shear Stress ◽  
Liquid Films ◽  
Heat Transfer Analysis ◽  
Tube Length ◽  
Prandtl Numbers ◽  
Falling Liquid Films

A theoretical study has been conducted for evaporative heating of turbulent free-falling liquid films inside long vertical tubes. The methodology of the present work is based on splitting the energy equation into homogeneous and nonhomogeneous problems. Solving these simple problems yields a rapidly converging solution, which is convenient for computational purposes. The eigenvalues associated with the homogeneous problem can be computed efficiently, without missing any one of them, by the sign-count algorithm. A new correlation for the local evaporative heat transfer coefficient along the tube length is developed over wide ranges of Reynolds and Prandtl numbers. Furthermore, the average heat transfer coefficient is correlated as a function of Reynolds and Prandtl numbers as well as the interfacial shear stress. A correlation for the heat transfer coefficient in the fully developed region is also presented in terms of Reynolds and Prandtl numbers. Typical numerical results showed excellent agreement of the present approach with the available data in the literature. Moreover, a parametric study is made to illustrate the general effects of various variables on the velocity and temperature profiles.

Evaporative Heat Transfer Analysis of a Heat Pipe With Hybrid Axial Groove

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Lizhan Bai ◽  
Guiping Lin ◽  
G. P. Peterson
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Flow Resistance ◽  
Heat Pipes ◽  
Low Flow ◽  
Circular Channel ◽  
Evaporative Heat Transfer ◽  
Evaporative Heat Transfer Coefficient

Through the application of thin film evaporation theory and the fundamental operating principles of heat pipes, a hybrid axial groove has been developed that can greatly enhance the performance characteristics of conventional heat pipes. This hybrid axial groove is composed of a V-shaped channel connected with a circular channel through a very narrow longitudinal slot. During the operation, the V-shaped channel can provide high capillary pressure to drive the fluid flow and still maintain a large evaporative heat transfer coefficient. The large circular channel serves as the main path for the condensate return from the condenser to the evaporator and results in a very low flow resistance. The combination of a high evaporative heat transfer coefficient and a low flow resistance results in considerable enhancement in the heat transport capability of conventional heat pipes. In the present work, a detailed mathematical model for the evaporative heat transfer of a single groove has been established based on the conservation principles for mass, momentum and energy, and the modeling results quantitatively verify that this particular configuration has an enhanced evaporative heat transfer performance compared with that of conventional rectangular groove, due to the considerable reduction in the liquid film thickness and a corresponding increase in the evaporative heat transfer area in both the evaporating liquid film region and the meniscus region.

scholarly journals FORCED CONVECTION DRYING OF INDIAN GROUNDNUT: AN EXPERIMENTAL STUDY

2017 ◽  
Vol 15 (3) ◽  
pp. 467
Author(s):  
Ravinder Kumar Sahdev ◽  
Mahesh Kumar ◽  
Ashwani Kumar Dhingra
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Experimental Error ◽  
Linear Regression Analysis ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Evaporative Heat Transfer

In this paper, convective and evaporative heat transfer coefficients of the Indian groundnut were computed under indoor forced convection drying (IFCD) mode. The groundnuts were dried as a single thin layer with the help of a laboratory dryer till the optimum safe moisture storage level of 8 – 10%. The experimental data were used to determine the values of experimental constants C and n in the Nusselt number expression by a simple linear regression analysis and consequently, the convective heat transfer coefficient (CHTC) was determined. The values of CHTC were used to calculate the evaporative heat transfer coefficient (EHTC). The average values of CHTC and EHTC were found to be 2.48 W/m2 oC and 35.08 W/m2 oC, respectively. The experimental error in terms of percent uncertainty was also estimated. The experimental error in terms of percent uncertainty was found to be 42.55%. The error bars for convective and evaporative heat transfer coefficients are also shown for the groundnut drying under IFCD condition.

Experiments on Hydrodynamic and Thermal Behaviors of Thin Liquid Films

2003 ◽  
Author(s):  
B. Ozar ◽  
B. M. Cetegen ◽  
A. Faghri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Liquid Flow ◽  
Local Heat Transfer ◽  
Disk Surface ◽  
Local Heat ◽  
Liquid Films ◽  
Local Heat Transfer Coefficient ◽  
Flow Rates

An experimental study of heat transfer into a thin film of liquid water on a rotating disk is described. The film was introduced from a flow collar at the center of a heated, horizontal disk at a fixed initial film thickness with a uniform radial velocity. Radial distribution of the disk surface temperatures was measured using a thermocouple / slip ring arrangement. Experiments were performed for a range of liquid flow rates between 3.0 lpm and 15.0 lpm corresponding to Reynolds numbers (based on the liquid inlet gap height and velocity) between 238 and 1188. The angular speed of the disk was varied from 0 rpm to 500 rpm. The local heat transfer coefficient was determined based on the heat flux supplied to the disk and the temperature difference between the measured disk surface temperature and the entrance temperature of the liquid onto the disk. The local heat transfer coefficient was seen to increase with increasing flow rate as well as increasing angular velocity of the disk. Effect of rotation on heat transfer was largest for the lower liquid flow rates with the effect gradually decreasing with increasing liquid flow rates. Semi-empirical correlations are presented in this study for the local and average Nusselt numbers. In addition to the heat transfer characterization, the thickness of the liquid film on the disk surface was measured by an optical method, including the characteristics of the hydraulic jump and the subcritical and supercritical flow regions.

scholarly journals Analysis Effects of Average Value of Convective and Evaporative Heat Transfer Coefficient on Solar Cabinet Dryer for Reduction of Mass of Papad

2021 ◽  
Vol 9 (12) ◽  
pp. 1511-1523
Author(s):  
Goldi Mathuriya
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Linear Regression Analysis ◽  
Transfer Coefficients ◽  
Average Value ◽  
Heat Transfer Coefficients ◽  
Mass Transfer Phenomenon ◽  
Evaporative Heat Transfer

Abstract: In this research paper, the behavior of heat and mass transfer phenomenon during greenhouse papad drying under forced convection mode has been investigated. Various experiments were performed during the month of April 2020 at SRCEM Banmore, morena (26o 34’13” N 78o 10’48” E). Experimental data obtained for forced convection greenhouse drying of papad were used to determine the constants in the Nusselt number expression by using the simple linear regression analysis and, consequently, the values of convective and evaporative heat transfer coefficients were evaluated. The average values of experimental constants C and n were determined as 0.9714 and 0.0129 respectively. The average values of convective and evaporative heat transfer coefficients were determined as 0.0886 W/m2 oC and 6.7583 W/m2 oC respectively. The experimental error in terms of percentage uncertainty was also evaluated. Keywords: Papad, Papad drying, Heat transfer coefficient, Convective, Evaporative, Forced convection greenhouse

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