AVERAGE HEAT TRANSFER OF TUBES IN DOWNWARD FOAM FLOW

The model of heat exchanger was investigated experimentally. This model consists of three vertical lines of horizontal tubes with five tubes in each. Tubes were arranged in a staggered order. Heat transfer of staggered bundle of tubes to downward static stable foam flow was investigated experimentally. Heat transfer dependence on specific gas and liquid velocity was determined. Dependence of volumetric void fraction of foam on heat transfer was investigated also. Heat transfer rate dependence on tube position in the line of tube bundle was investigated experimentally. It was established that heat transfer rate highly depends on tube position in the line. Influence of tube position on heat transfer from tube bundle in upward foam flow was compared. Heat transfer dependence on tube position in the bundle was investigated experimentally also. Influence of wall of foam generator on heat transfer to sideline of tubes was established. Experimental results of heat transfer of bundle of tubes to downward static stable foam flow were generalized using dependence between Nusselt and Reynolds numbers.

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Heat Transmission Reinforcers Induced by MHD Hybrid Nanoparticles for Water/Water-EG Flowing over a Cylinder

Coatings ◽

10.3390/coatings11060623 ◽

2021 ◽

Vol 11 (6) ◽

pp. 623

Author(s):

Firas A. Alwawi ◽

Mohammed Z. Swalmeh ◽

Amjad S. Qazaq ◽

Ruwaidiah Idris

Keyword(s):

Heat Transfer ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Volume Fraction ◽

Liquid Velocity ◽

Flow Characteristics ◽

Hybrid Nanoparticles ◽

Critical Parameters ◽

Heat Transmission ◽

Constant Wall Temperature

The assumptions that form our focus in this study are water or water-ethylene glycol flowing around a horizontal cylinder, containing hybrid nanoparticles, affected by a magnetic force, and under a constant wall temperature, in addition to considering free convection. The Tiwari–Das model is employed to highlight the influence of the nanoparticles volume fraction on the flow characteristics. A numerical approximate technique called the Keller box method is implemented to obtain a solution to the physical model. The effects of some critical parameters related to heat transmission are also graphically examined and analyzed. The increase in the nanoparticle volume fraction increases the heat transfer rate and liquid velocity; the strength of the magnetic field has an adverse effect on liquid velocity, heat transfer, and skin friction. We find that cobalt nanoparticles provide more efficient support for the heat transfer rate of aluminum oxide than aluminum nanoparticles.

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Different Type Tube Bundle Heat Transfer to Vertical Foam Flow

ASME 5th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2007-30070 ◽

2007 ◽

Author(s):

Jonas Gylys ◽

Stasys Sinkunas ◽

Tadas Zdankus ◽

Vidmantas Giedraitis

Keyword(s):

Heat Transfer ◽

Experimental Investigation ◽

Flow Velocity ◽

Void Fraction ◽

Tube Bundle ◽

Auxiliary Equipment ◽

Foam Flow ◽

Flow Parameters ◽

Tube Bundles ◽

Foam Generator

Gas-liquid foam due to especially large inter-phase contact surface can be used as a coolant. An experimental investigation of the staggered and in-line tube bundles’ heat transfer to the vertically upward and downward laminar foam flow was performed. The experimental setup consisted of the foam generator, vertical experimental channel, tube bundles, measurement instrumentation and auxiliary equipment. It was determined dependency of heat transfer intensity on flow parameters: flow velocity, direction of flow, volumetric void fraction of foam and liquid drainage from foam. Apart of this, influence of tube position in the bundle to heat transfer was investigated. Foam flow structure, distribution of the foam’s local void fraction and flow velocity in cross-section of the channel were the main factors which influenced on heat transfer intensity of the different tubes. Experimental investigation showed that the heat transfer intensity of the frontal and further tubes of the bundles to vertical foam flow is different in comparison with one-phase fluid flow. The results of the experimental investigation are presented in this paper.

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The Performance of a Scaled-Down Fluidized Loop Seal

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-051 ◽

2003 ◽

Cited By ~ 1

Author(s):

Andreas Johansson ◽

Filip Johnsson ◽

Bengt-A˚ke Andersson

Keyword(s):

Heat Transfer ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Scaling Laws ◽

Tube Bundle ◽

Flow Behavior ◽

Cross Flow ◽

Operating Conditions ◽

Cfb Boiler ◽

Super Heater

This work investigates the solids cross flow in a super-heater tube bundle immersed in the loop seal of a cold CFB unit. The loop seal and the tube bundle are scaled to a 1/3rd of the size of a loop seal and a super-heater located in a 30 MWth CFB boiler. The simplified scaling laws proposed by Glicksman et al. [1] are applied to the flow in the seal. The loop seal was built into an existing CFB unit with riser dimensions 0.7 m × 0.12 m × 8.5 m. The riser is not scaled but the pressure distribution in the CFB loop is similar to that in the boiler. The solids flow through the tube bundle was studied by means of visual observations, pressure drop and tube-temperatures, corresponding to the overall heat transfer rate to each tube. The loop seal was operated under various conditions, including those typical for the boiler. Thus, the recirculation flux of solids through the loop seal, as well as the fluidization velocity in the seal, were varied. In addition, the fraction of the bottom area that is fluidized was varied. The overall flow behavior of the CFB loop with the scaled loop seal was found to be similar to that of the boiler. The temperature measurements showed that the heat transfer rate to the tubes in the bundle differed depending on operating conditions and on the position of the tube, both laterally and vertically. The recirculation flux could be maintained with a substantial decrease of the fluidization flow in the seal compared to the conditions corresponding to full load in the boiler. In addition, it was possible to significantly decrease the fraction of the bottom of the seal that was fluidized. However, if the area beneath the tube bundle is not fluidized, the heat transfer rate to the tubes decreased.

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ANALYSIS OF TUBE BUNDLE HEAT TRANSFER TO VERTICAL FOAM FLOW

Revista de Engenharia Térmica ◽

10.5380/ret.v4i2.5038 ◽

2005 ◽

Vol 4 (2) ◽

Author(s):

J. Gylys ◽

S. Sinkunas ◽

T. Zdankus

Keyword(s):

Heat Transfer ◽

Tube Bundle ◽

Vertical Channel ◽

Horizontal Tube ◽

Heat Transfer Process ◽

Two Phase ◽

Stable Foam ◽

Foam Flow ◽

Experimental Heat ◽

Structure Changes

Phenomena of foam flow and associated heat transfer are rather complex. Foam is a twophase flow, which structure changes while it passes an obstacle: bubbles divide into smaller bubbles and liquid drains down from flow. Due to these peculiarities, an application of analytical methods for their study is a complex subject. Thus experimental method of investigation was selected in our work. The investigation apparatus consisted of foam generator, vertical channel and staggered bank of horizontal tubes. The cross section of the channel had square profile with side dimension 140 mm. Tubes in the bank were located in three vertical rows with five tubes in each of them. Experiments were performed within Reynolds number diapason for gas from 190 to 450 and foam void volumetric fraction from 0.996 to 0.998. Direction of foam motion in vertical channels also influences heat transfer intensity. Investigations of heat transfer process of upward and downward moving statically stable foam flow from horizontal tube bank were performed. Experimental heat transfer results of tube bundle in vertical cross foam flow were summarized by criterion equations, which enable determination of heat transfer intensity of the entire bundle or of a separate tube of the bundle for different values of void volumetric fractions and regime parameters of statically stable foam flow.

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ANALYSIS OF TUBE BUNDLE HEAT TRANSFER TO VERTICAL FOAM FLOW

Revista de Engenharia Térmica ◽

10.5380/reterm.v4i2.5038 ◽

2005 ◽

Vol 4 (2) ◽

pp. 91 ◽

Cited By ~ 2

Author(s):

J. Gylys ◽

S. Sinkunas ◽

T. Zdankus

Keyword(s):

Heat Transfer ◽

Tube Bundle ◽

Vertical Channel ◽

Horizontal Tube ◽

Heat Transfer Process ◽

Two Phase ◽

Stable Foam ◽

Foam Flow ◽

Experimental Heat ◽

Structure Changes

Phenomena of foam flow and associated heat transfer are rather complex. Foam is a twophase flow, which structure changes while it passes an obstacle: bubbles divide into smaller bubbles and liquid drains down from flow. Due to these peculiarities, an application of analytical methods for their study is a complex subject. Thus experimental method of investigation was selected in our work. The investigation apparatus consisted of foam generator, vertical channel and staggered bank of horizontal tubes. The cross section of the channel had square profile with side dimension 140 mm. Tubes in the bank were located in three vertical rows with five tubes in each of them. Experiments were performed within Reynolds number diapason for gas from 190 to 450 and foam void volumetric fraction from 0.996 to 0.998. Direction of foam motion in vertical channels also influences heat transfer intensity. Investigations of heat transfer process of upward and downward moving statically stable foam flow from horizontal tube bank were performed. Experimental heat transfer results of tube bundle in vertical cross foam flow were summarized by criterion equations, which enable determination of heat transfer intensity of the entire bundle or of a separate tube of the bundle for different values of void volumetric fractions and regime parameters of statically stable foam flow.

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