Heat exchange of dynamic powder beds with a heat-transfer surface. I. A helical screw conveyer and a horizontal rotating cylinder

1999 ◽  
Vol 72 (1) ◽  
pp. 1-6
Author(s):  
D. S. Pashkevich ◽  
Yu. I. Alekseev ◽  
A. A. Moiseenko ◽  
S. M. Radchenko
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Rotating Cylinder ◽  
Heat Transfer Surface ◽  
Screw Conveyer

Heat exchange of dynamic powder beds with a heat-transfer surface. II. A dust-laden gas flow

1999 ◽  
Vol 72 (1) ◽  
pp. 7-10
Author(s):  
D. S. Pashkevich ◽  
V. N. Krasnokutskii ◽  
V. B. Petrov ◽  
V. L. Korolev
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Gas Flow ◽  
Heat Transfer Surface

Mechanisms of Heat Transfer Enhancement of Gas–Solid Fluidized Bed: Estimation of Direct Contact Heat Exchange From Heat Transfer Surface to Fluidized Particles Using an Optical Visualization Technique

1995 ◽  
Vol 117 (1) ◽  
pp. 104-112 ◽  
Author(s):  
Y. Kurosaki ◽  
I. Satoh ◽  
T. Ishize
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Direct Contact ◽  
Heat Transfer Surface ◽  
Heat Transfer Tube ◽  
Transfer Tube ◽  
Contact Frequency ◽  
Fluidized Particles

This paper deals with mechanisms of heat transfer in a gas–solid fluidized bed. Heat transfer due to heat exchange by direct contact from a heat transfer tube immersed in the bed to fluidized particles was studied by means of visualization of contact of the fluidized particles to the heat transfer surface. The results show that the duration of contact of fluidized particles was almost uniform over the tube circumference and was hardly affected by the flow rate of fluidizing gas. On the other hand, the contact frequency between the particles and heat transfer tube was evidently influenced by the gas flow rate and particles diameter, as well as the location on the tube circumference. Using the visualized results, the amount of heat conducted to fluidized particles during the contact was estimated. This result showed that unsteady heat conduction to the fluidized particles plays an important role in the heat transfer, especially at the condition of incipient fluidization.

scholarly journals INTENSIFICATION OF HEAT EXCHANGE IN DIABATIC RECTIFICATION COLUMNS

2020 ◽  
pp. 511-518
Author(s):  
Nikolay Aleksandrovich Voinov ◽  
Denis Andreyevich Zemtsov ◽  
Anastasiya Viktorovna Bogatkova ◽  
Nina Vladimirovna Deryagina
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Film Flow ◽  
Heat Removal ◽  
Heat Transfer Surface ◽  
Water Mixture ◽  
Gravitational Flow ◽  
Intensification Of Heat Exchange ◽  
The Cost ◽  
Intensify Heat Transfer

The heat exchange in a diabatic column was investigated during the rectification of an ethanol-water mixture, in which partial condensation of rising vapors on the surface of vertical heat exchange tubes installed vertically along the height of the installation was carried out, as well as the evaporation of intermediate condensate on the surface of horizontal plates. Based on the review of diabatic columns, it is shown that they can reduce the cost of conducting the rectification process. Heat-exchange devices placed on trays of rectification units are considered and ways to intensify heat transfer in them are proposed. It has been established that the most efficient heat removal in heat exchangers of diabatic columns is achieved when using a film flow of a coolant on a heat transfer surface. Heat transfer in a diabatic column is investigated during gravitational flow of surfaces of heat exchange tubes, as well as when organizing an ascending and descending co-current film flow, both in the case of heating and boiling of the coolant. To intensify heat transfer in the coolant film, a helical artificial roughness was installed on the surface of the pipes, made in the form of a wire spiral tightly mounted on the heat transfer surface. The geometric parameters of the helical roughness, such as the distance between the turns of the spiral and the height of the wire, which have the greatest influence on the intensity of heat transfer, have been established. Dependences for determining the value of the heat transfer coefficient are presented and an estimate of the value of the specific heat flux in the diabatic column is given.

scholarly journals Heat Exchange Between Air and a Liquid Film Flowing Down Along a Profiled Surface

2020 ◽  
Vol 38 (3) ◽  
pp. 622-628
Author(s):  
Vitaly V. Dubrovsky ◽  
Aleksandr A. Shraiber
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Liquid Film ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Heat Transfer Surface ◽  
Optimal Conditions ◽  
Counter Flow ◽  
Surface Profiling ◽  
Exchange Intensity

The laws of heat exchange between air and a liquid film flowing down along a solid surface with spherical dimples were investigated experimentally. Three cases of heat transfer were considered: quiescent air, air – liquid counter flow, or their cross flow. In all cases, a significant growth of the heat exchange intensity, especially at air – liquid cross flow, was observed. This is caused by the substantial turbulization of flow and mixing of liquid layers in the film. As a result, it was established that surface profiling (manufacture of dimples) under the optimal conditions leads to an increase in heat exchange intensity by an unexpended factor of 2.5 – 2.8 as compared with a smooth surface, other conditions being equal. The obtained experimental data were generalized in the form of dimensionless dependences Nu vs. Re. The best heat transfer surface can be recommended for use in different heat exchangers.

A Computer Code Using Exergy for Optimizing Thermal Plants

1991 ◽  
Vol 113 (1) ◽  
pp. 145-150 ◽  
Author(s):  
G. Bidini ◽  
S. S. Stecco
Keyword(s):  
Heat Transfer ◽  
Energy Consumption ◽  
Heat Exchange ◽  
Temperature Difference ◽  
Computer Code ◽  
Heat Transfer Surface ◽  
Exergetic Efficiency ◽  
Industrial Plants ◽  
Exergetic Analysis ◽  
Reducing Energy

This paper presents an exergetic approach to reducing energy consumption in industrial plants. The minimum pinchpoint temperature difference is determined for several cases of heat exchange between hot and cold fluid streams with reduced thermal losses. The proposed method, designated TEXAS (Thermal and economic EXergetic Analysis of Systems), derives families of characteristic curves showing economic parameters versus exergetic efficiency in relation to factors such as heat transfer, surface, and scaling. As the method is highly affected by the economic parameter assumptions, the sensitivity of the variations in the parameters is also analyzed.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

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