Experimentation and modeling of convective heat transfer coefficient for evaporation of liquid foods in a pilot plant double effect

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Reyes Carlos Macedo y Ramírez ◽  
Jorge Fernando Vélez Ruiz
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Process Design ◽  
Food Industry ◽  
Convective Heat Transfer Coefficient ◽  
Double Effect ◽  
Sugar Solution ◽  
Convective Coefficient ◽  
Common Process ◽  
Predicted Values

Abstract Even though the evaporation is a common process in the food industry, there is scarce information about the convective coefficient evaluation as an important parameter for equipment and process design. A research on evaporation of sugar solution in a double effect was carried out. The experimental results obtained in this equipment, from the heat transfer and concentration processes are presented, a range of 2658–6091 W of heat flow was quantified implying computed values of 1431–3763 W/m2K for the convective coefficients and 1020–1815 W/m2K for the overall coefficient. The quantification of the convective coefficient, the fitting methodology and modeling were developed in order, to obtain the correspondent correlations. Then, from a set of several equations, two general relationships are proposed. Both correlations were applied to experimental and supposed data, finding a difference lower than 30% between the experimental and predicted values of the Nusselt number, that was considered as satisfactory.

Computer Modelling of Temperature Distribution in Brake Drums for Fade Assessment

1988 ◽  
Vol 202 (4) ◽  
pp. 257-264 ◽  
Author(s):  
V T V S Ramachandra Rao ◽  
H Ramasubramanian ◽  
K N Seetharamu
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Temperature Distribution ◽  
Present Model ◽  
Computer Modelling ◽  
Convective Heat Transfer Coefficient ◽  
The Finite Element Method ◽  
Data Logging ◽  
Brake Drum ◽  
Predicted Values

Simulation of the temperature distribution in a brake drum of a commercial truck is carried out using the finite element method. Verification of the predicted values is done using an inertia dynamometer with a data logging system. The effect of variable convective heat-transfer coefficient and the effect of contact area are also studied. From the investigation it is concluded that the present model can be used for the simulation of temperature distribution in rigid brake drums during a fade test.

Convective Heat Transfer Coefficient and Pressure Drop of Al2O3-Water Nanofluid in a Single-Phase Microchannel for Cooling of High Heat Output Devices

2008 ◽  
Author(s):  
Guillermo E. Valencia ◽  
Miguel A. Ramos ◽  
Antono J. Bula
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Heat Output ◽  
Flux Boundary Condition

The paper describes an experimental procedure performed to obtain the convective heat transfer coefficient of Al2O3 nanofluid working as cooling fluid under turbulent regimen through arrays of aluminum microchannel heat sink having a diameter of 1.2 mm. Experimental Nusselt number correlation as a function of the volume fractions, Reynolds, Peclet and Prandtl numbers for a constant heat flux boundary condition is presented. The correlation for Nusselt number has a good agreement with experimental data and can be used to predict heat transfer coefficient for this specific nanofluid, water/Al2O3. Furthermore, the pressure drop is also analyzed considering the different nanoparticles concentration.

On the Teaching of Condensation Heat Transfer

2004 ◽  
Author(s):  
A. O¨zer Arnas ◽  
Daisie D. Boettner ◽  
Michael J. Benson ◽  
Bret P. Van Poppel
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Convective Heat Transfer Coefficient ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Condensate Film ◽  
Vapor Interface ◽  
Simplifying Assumptions ◽  
Thermo Physical Properties ◽  
Vapor Temperature

The topic of condensation heat transfer is usually included in a chapter on Boiling and Condensation in most Heat Transfer textbooks. The assumptions made are those of laminar liquid film with constant thermo-physical properties, uniform vapor temperature equal to the saturation temperature of the vapor, negligible shear at the liquid-vapor interface, and negligible momentum and energy transfer by advection in the condensate film. The results presented are normally for the film thickness, the local convective heat transfer coefficient, and the Nusselt number. However, no means are presented to the student to determine if all of these simplifying assumptions are actually satisfied for a given problem. This investigation clarifies these points to improve teaching of the material and understanding by the student at the undergraduate and graduate level.

Heat Transfer of Polymer Particles in Gas-Phase Polymerization Reactors

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Yaghoub Behjat ◽  
Mohammad Ali Dehnavi ◽  
Shahrokh Shahhosseini ◽  
Seyed Hassan Hashemabadi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Phase ◽  
Transfer Rate ◽  
Fluid Dynamic ◽  
Convective Heat Transfer Coefficient ◽  
Particle Surface ◽  
Cfd Modeling ◽  
Polymerization Reactor ◽  
Gas Phase Polymerization

In this paper the effects of particles configuration and particles distance on the heat transfer rate in a gas phase olefin polymerization reactor have been studied using the computational fluid dynamic (CFD) modeling approach. The goal was to determine the causes of particle overheating in this reactor. It has been shown that classic correlations such as Ranz-Marshall are sufficiently adequate when far away particles with no interactions are to be modeled. However, when particles are sufficiently close to having interactions, these correlations fail to satisfactorily predict the convective heat transfer coefficient. The results indicate an increase in particle distance leads to an increase in the Nusselt number on the particle surface. Therefore, for particles with a large distance and triangular or rotated square configurations, the local Nusselt number is closer to the Nusselt number for a single particle.

scholarly journals Determination of Heat Transfer Coefficients Over Ribbed Surfaces With Infrared Thermography

1997 ◽  
Author(s):  
Francisco P. Brójo ◽  
Luís C. Gonçalves ◽  
Pedro D. Silva
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Stanton Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The scope of the present work is to characterize the heat transfer between a ribbed surface and an air flow. The convective heat transfer coefficients, the Stanton number and the Nusselt number were calculated in the Reynolds number range, 5.13 × 105 to 1.02 × 106. The tests were performed inside a turbulent wind tunnel with one roughness height (e/Dh = 0.07). The ribs had triangular section with an attack angle of 60°. The surface temperatures were measured using an infrared (IR) thermographic equipment, which allows the measurement of the temperature with a good spatial definition (10.24 × 10−6 m2) and a resolution of 0.1°C. The experimental measures allowed the calculation of the convective heat transfer coefficient, the Stanton number and the Nusselt number. The results obtained suggested a flow pattern that includes both reattachment and recirculation. Low values of the dimensionless Stanton number, i.e. Stx*, are obtained at the recirculation zones and very high values of Stx* at the zones of reattachment. The reattachment is located at a dimensionless distance of 0.38 from the top of the rib. That distance seems to be independent of the Reynolds number. The local dimensionless Stanton number remains constant as the Reynolds number varies. The convective heat transfer coefficient presents an uncertainty in the range of 3 to 6%.

A Correlation for Nusselt Number Under Turbulent Mixed Convection Using Transient Heat Transfer Experiments

2010 ◽  
Author(s):  
N. Gnanasekaran ◽  
C. Balaji
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
A Priori ◽  
Convective Heat Transfer Coefficient ◽  
Time History ◽  
Vertical Channel ◽  
The Difference ◽  
Nusselt Number Correlation ◽  
Temperature Time

This paper reports the results of an experimental investigation of transient, turbulent mixed convection in a vertical channel in which one of the walls is heated and the other is adiabatic. The goal is to simultaneously estimate the constants in a Nusselt number correlation whose form is assumed a priori by synergistically marrying the experimental results with repeated numerical calculations that assume guess values of the constants. The convective heat transfer coefficient “h” is replaced by the Nusselt number (Nu) which is then assumed to have a form Nu = a (1+RiD) b ReDc where a, b and c are the constants to be evaluated. From the experimentally obtained temperature time history and the simulated temperature time history, based on some guess values of a, b, and c, one can define the objective function or the residue as the sum of the square of the difference between experimentally obtained and simulated temperatures. Using Bayesian inference driven by the Markov chain Monte Carlo method, one, more or all of the constants a, b and c are retrieved together with the uncertainty involved in these estimates. Additionally, the estimated parameters are compared with experimental benchmarks.

scholarly journals Determination of the Reference Temperature for a Convective Heat Transfer Coefficient in a Heated Tube Bank

2021 ◽  
Vol 11 (22) ◽  
pp. 10564
Author(s):  
Stanislav Kotšmíd ◽  
Zuzana Brodnianská
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbulent Flows ◽  
Convective Heat Transfer Coefficient ◽  
Reference Temperature ◽  
Tube Bank ◽  
Heated Tube ◽  
Tube Banks

The paper presents a theoretical analysis of heat transfer in a heated tube bank, based on the Nusselt number computation as one of the basic dimensionless criteria. To compute the Nusselt number based on the heat transfer coefficient, the reference temperature must be determined. Despite the value significance, the quantity has several different formulations, which leads to discrepancies in results. This paper investigates the heat transfer of the inline and staggered tube banks, made up of 20 rows, at a constant tube diameter and longitudinal and transverse pitch. Both laminar and turbulent flows up to Re = 10,000 are considered, and the effect of gravity is included as well. Several locations for the reference temperature are taken into consideration on the basis of the heretofore published research, and the results in terms of the overall Nusselt number are compared with those obtained by the experimental correlations. This paper provides the most suitable variant for a unique reference temperature, in terms of a constant value for all tube angles, and the Reynolds number ranges of 100–1000 and 1000–10,000 which are in good agreement with the most frequently used correlating equations.

Investigation of Heat Transfer Efficiency of Improved Intermig Impellers in a Stirred Tank Equipped with Vertical Tubes

2020 ◽  
Vol 18 (3) ◽  
Author(s):  
Leizhi Wang ◽  
Yongjun Zhou ◽  
Zhaobo Chen
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Heat Exchange ◽  
Convective Heat Transfer Coefficient ◽  
Simulation Software ◽  
Related Factors ◽  
Temperature Boundary Layer ◽  
Temperature Boundary ◽  
Vertical Tubes

AbstractThe heat transfer of a reactor with improved Intermig impellers was numerically investigated by the finite element method (FEM) simulation software Fluent (V.19). A turbulence model utilized the standard k-ε model, and the turbulent flows in two large vortexes between vertical tubes were collided to form a strong convection. The influence of heat and mass transfer developing from the impeller diameters, the distance between the two impellers (C1), the rotational speed and the installation height of the bottom impeller (C2) were studied. The reactor was equipped with special structure vertical tubes to increase the heat exchange areas. The rate of heat transfer, including criteria such as the convective heat transfer coefficient, the Nusselt number of outside vertical tubes, and the temperature boundary layer thickness, assured the accurate control of the heat exchange mixing state. The experimental testing platform was designed to validate the simulated results, which revealed the influence order of related factors. The Nusselt number Nu was affected by various related factors, resulting in the rotation and diameter of impellers extending far beyond the distance between the two impellers (C1) and the installation height of the impeller (C2). The average temperature boundary layer thicknesses of the symmetrical and middle sections were 3.24 mm and 3.48 mm, respectively. Adjusting the appropriate parameters can accurately control the heat exchange process in such a reactor, and the conclusions provide a significant reference for engineering applications.

CFD Heat Transfer Investigation Into the Convective Coefficient of a Perforated Plate

2005 ◽  
Author(s):  
Andrew M. Hayes ◽  
Jamil A. Khan ◽  
Ian G. Spearing ◽  
Aly Shaaban
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Perforated Plate ◽  
Upstream Face ◽  
Cfd Model ◽  
Plate Temperature ◽  
Convective Coefficient ◽  
Perforated Sheet ◽  
Exit Temperature ◽  
Computational Fluid Dynamics Cfd

A computational fluid dynamics (CFD) model investigating the heat transfer convective coefficient of the upstream face, the upstream face and the tube face, and the upstream face, tube face, and leeward face of a perforated sheet was developed. This model was based on the hexagonally shaped flow pattern that exists around each of the holes in a perforated sheet of a certain pitch to diameter ratio. The CFD model used in the investigation of the convective heat transfer coefficient involved a single hole in a thin hexagonally shaped sheet with appropriate boundary conditions. Through a series of models varying the inlet velocity, hole diameter, and the plate temperature and then solving for the exit temperature the convective coefficient could be obtained. After obtaining the convective coefficient, the Nusselt number was calculated. These values were then plotted against the Reynolds number and an equation for the line was obtained of the form: Nu=C1·ReC2(1)

Sign in / Sign up

Export Citation Format

Share Document