Calculation and Analysis on Condensation Heat Transfer for Pressurized Oxy-Coal Combustion Flue Gas

2013 ◽  
Vol 325-326 ◽  
pp. 346-352
Author(s):  
Jing Lan Dong ◽  
Wei Ping Yan ◽  
Xue Hong He
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Water Vapor ◽  
Film Thickness ◽  
Flue Gas ◽  
Coal Combustion ◽  
Vertical Tube ◽  
Condensation Heat Transfer ◽  
Condensation Rate ◽  
Set Up

For the convective condensation heat transfer of flue gas with a few water vapors produced by pressurized oxy-coal combustion in vertical tube, investigation and calculation were carried out by theoretical analyzing method. Heat transfer mathematical model was set up by modified film model and Nusselt's condensation theory. Calculations were performed for condensation heat transfer at different wall temperatures, Reynolds numbers and water vapor fractions. Results show that with the increase of wall temperature, the condensation rate of flue gas, heat flux and condensation film thickness decrease. And with the increase of Reynolds number of the mixture gas, the condensation rate of flue gas and heat flux increase too, while the condensation film thickness decrease. With the decrease of water vapor fraction, the condensation rate of flue gas and heat flux decrease too, while the decrease of condensation film thickness is not obvious.

Analysis of Stagnant Non Condensable Gases Effects on Condensation Heat Transfer in a Vertical Tube

2011 ◽  
Vol 148-149 ◽  
pp. 491-495
Author(s):  
Jun Xia Zhang ◽  
Zeng Sheng Li ◽  
Bin Yao Gong ◽  
Hong Xing Zhao ◽  
Yu Huai Zhao
Keyword(s):  
Heat Transfer ◽  
Mass Fraction ◽  
Volume Fraction ◽  
Vertical Tube ◽  
Condensation Heat Transfer ◽  
Condenser Tube ◽  
Condensation Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Velocity Pressure

In a vertical condenser tube installed at the cold end of a non-vacuum separate type heat pipe, non condensable (NC) gases in the system is pushed by continuous vapor flowing from the hot end into the condenser tube at the cold end, gathering above condensate at the outlet of the condenser tube. Therefore, condensation heat transfer of vapor with the stagnant NC gases occurs in the condenser tube. It is necessary to comprehend the effects of stagnant NC gases on condensation heat transfer. A VOF method was adopted to analyze how stagnant NC gases affect condensation heat transfer, a mass fraction equation of NC gases was used to solve diffusion between NC gases and vapor, a Hertz-Knudsen-Schrage model was applied to deal with condensation rate of vapor on the surface of liquid film. Parameters, including volume fraction, velocity, pressure, mass fraction of NC gases and condensation heat transfer coefficients (HTC), were obtained. Results show that a lot of NC gases deposits in the condenser tube rear, leading a lot of vapor to condense at the condenser tube front. NC gases slightly affect condensation HTC of the tube front, and severely degrade condensation HTC of the tube rear. Furthermore, an increase in mass of NC gases causes a rise in pressure and velocity, improving condensation heat transfer.

Analytical Modeling for Vapor Condensation in the Presence of Noncondensable Gas and Experimental Validation

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Wei Zhang ◽  
Suilin Wang ◽  
Mu Lianbo
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Latent Heat ◽  
Flue Gas ◽  
Vertical Surface ◽  
Vapor Condensation ◽  
Condensation Heat Transfer ◽  
Wall Area ◽  
Cooling Surface ◽  
Applicable Range

Abstract The sensible and latent heat transfer are two essential considerations in investigating vapor condensation in the presence of noncondensable gases. In this paper, a new model for filmwise condensation heat transfer was developed using similarity-based solution. The expression of gas–liquid interfacial temperature, film thickness, and heat transfer coefficient were derived and calculated, respectively. The analytical results showed that the temperature difference between gas–liquid interfacial and cooling surface is decreased as there is an increase in cooling surface temperature. In addition, the forced-convective condensation heat transfer and film thickness on the vertical surface were experimentally carried out. The proportion of latent heat is 62–67% and relatively larger than sensible heat in the range of wall temperature (17–32.5 °C). The experimental film thickness is less than analytical film thickness by 2–10%. It is because that the liquid film may evaporate back to water vapor in the neighboring wall area due to high temperature of flue gas. Further, a new nondimensional correlation of condensation heat transfer of flue gas is fitted with Nu = 0.62Re0.5Ja0.67 and applicable range is Re = 1000–2500, Ja = 1.7–4.4. The fitting shows a good agreement between experimental and correlated values except some points in the low Nu number. The model proposed is applicable to predict the temperature and velocity distribution for condensation heat and mass transfer of multicomponent gases.

scholarly journals An Experimental Investigation of Water Vapor Condensation from Biofuel Flue Gas in a Model of Condenser, (1) Base Case: Local Heat Transfer without Water Injection

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 844
Author(s):  
Robertas Poškas ◽  
Arūnas Sirvydas ◽  
Vladislavas Kulkovas ◽  
Povilas Poškas
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Flue Gas ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Water Injection ◽  
Vapor Condensation ◽  
Base Case ◽  
Water Vapor Condensation ◽  
Condensing Heat Exchanger

Waste heat recovery from flue gas based on water vapor condensation is an important issue as the waste heat recovery significantly increases the efficiency of the thermal power units. General principles for designing of this type of heat exchangers are known rather well; however, investigations of the local characteristics necessary for the optimization of those heat exchangers are very limited. Investigations of water vapor condensation from biofuel flue gas in the model of a vertical condensing heat exchanger were performed without and with water injection into a calorimetric tube. During the base-case investigations, no water was injected into the calorimetric tube. The results showed that the humidity and the temperature of inlet flue gas have a significant effect on the local and average heat transfer. For some regimes, the initial part of the condensing heat exchanger was not effective in terms of heat transfer because there the flue gas was cooled by convection until its temperature reached the dew point temperature. The results also showed that, at higher Reynolds numbers, there was an increase in the length of the convection prevailing region. After that region, a sudden increase was observed in heat transfer due to water vapor condensation.

A Heat Transfer Model of Dropwise Condensation Underneath a Horizontal Substrate

2011 ◽  
Vol 199-200 ◽  
pp. 1604-1608
Author(s):  
Yun Fu Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Fractal Model ◽  
Condensation Heat Transfer ◽  
Droplet Growth ◽  
Transfer Model ◽  
Dropwise Condensation ◽  
Small Contact Angle ◽  
Horizontal Substrate

For finding influence of the condensing surface to dropwise condensation heat transfer, a fractal model for dropwise condensation heat transfer has been established based on the self-similarity characteristics of droplet growth at various magnifications on condensing surfaces with considering influence of contact angle to heat transfer. It has been shown based on the proposed fractal model that the area fraction of drops decreases with contact angle increase under the same sub-cooled temperature; Varying the contact angle changes the drop distribution; higher the contact angle, lower the departing droplet size and large number density of small droplets; dropwise condensation translates easily to the filmwise condensation at the small contact angle ;the heat flux increases with the sub-cooled temperature increases, and the greater of contact angle, the more heat flux increases slowly.

Condensation heat transfer on tubes in actual flue gas (Parametric study for condensation behavior)

2003 ◽  
Vol 32 (2) ◽  
pp. 153-166 ◽  
Author(s):  
Masahiro Osakabe ◽  
Kiyoyuki Yagi ◽  
Tsugue Itoh ◽  
Kunimitsu Ohmasa
Keyword(s):  
Heat Transfer ◽  
Flue Gas ◽  
Parametric Study ◽  
Condensation Heat Transfer ◽  
Actual Flue Gas

scholarly journals Thermal analysis in thin-film fluid regions of rectangular microgroove

2018 ◽  
Vol 22 (2) ◽  
pp. 899-897
Author(s):  
Xiaohong Gui ◽  
Xiange Song ◽  
Baisheng Nie
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Film Thickness ◽  
Flux Distribution ◽  
Total Heat ◽  
Heat Flux Distribution ◽  
Total Heat Transfer ◽  
Thin Film Thickness

The effects of contact angle and superheat on thin-film thickness and heat flux distribution occurring in a rectangle microgroove are numerically simulated. Accordingly, physical, and mathematical models are built in detail. Numerical results indicate that meniscus radius and thin-film thickness increase with the improvement of contact angle. The heat flux distribution in the thin-film region increases non-linearly as the contact angle decreases. The total heat transfer through the thin-film region increases with the improvement of superheat, and decreases as the contact angle increases. When the contact angle is equal to zero, the heat transfer in the thin-film region accounts for more than 80% of the total heat transfer. Intensive evaporation in the thin-film region plays a key role in heat transfer for the rectangle capillary microgroove. The liquid with higher wetting performance is more capable of playing the advantages of higher intensity heat transfer in thin- film region. The current investigation will result in a better understanding of thin- -film evaporation and its effect on the effective thermal conductivity in the rectangle microgroove.

scholarly journals Characteristics of Flow Boiling Heat Transfer and Critical Heat Flux in a Vertical Tube with a Wire Coil.

2001 ◽  
Vol 67 (653) ◽  
pp. 128-134
Author(s):  
Keishi TAKESHIMA ◽  
Terushige FUJII ◽  
Nobuyuki tAKENAKA ◽  
Hitoshi ASANO ◽  
Takamitsu KONDO
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Flow Boiling Heat Transfer ◽  
Wire Coil
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