Spray Cooling Unit for Heat Treatment of Stainless Steel Sheets

2014 ◽  
Vol 936 ◽  
pp. 1720-1724
Author(s):  
Milan Hnizdil ◽  
Martin Chabicovsky ◽  
Miroslav Raudenský ◽  
Eric Magadoux ◽  
Florent Code
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Spray Cooling ◽  
Laboratory Measurements ◽  
Steel Sheets ◽  
Cooling Unit ◽  
Cooling Intensity ◽  
The Heat Transfer Coefficient

Stainless steel sheets are successively heated to a temperature of 1150°C and cooled until ambient temperature during the production process. Requirements for high cooling rates of stainless steel sheets producers lead to use water as a cooling medium. The information about cooling intensity (heat transfer coefficient) of different nozzles configurations is necessary for designing cooling sections. Although many researchers deal with water spray cooling, actually a general correlation for predicting heat transfer coefficient for wide range of nozzles configurations does not exists. That is the reason why heat transfer coefficient for different nozzles configurations can be only obtained by laboratory measurements. Heat transfer coefficient is mostly influenced by water impingement density and impact velocity. However other factors e.g. water temperature and velocity of the sheet can influence the heat transfer coefficient. Optimized design of the cooling unit with high cooling intensity and low water consumption was achieved by appropriate choice of these parameters. The moving experimental sheet was cooled from a temperature of 900°C to a temperature of 50°C with various configurations of nozzles. The tests shown that heat transfer coefficient was increasing with water impingement density and impact velocity. Increasing water temperature from 20 °C to 80 °C caused a decrease of the heat transfer coefficient and Leidenfrost temperature. The effect of velocity is negligible when velocities are between 25 and 100 m/min. The cooling unit was designed according to laboratory measurements to fulfill the stainless steel producer's requirements. The measurements which were done in an industrial plant confirmed the accuracy of heat transfer coefficient obtained in the laboratory. The maximum difference between laboratory and plant measurements was 15%.

Heat Transfer and Fouling Performance During Falling Film Evaporation in Vertical Porous Tubes

2020 ◽  
Author(s):  
Lei Wang ◽  
Weiyu Tang ◽  
Limin Zhao ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Falling Film ◽  
Film Evaporation ◽  
Falling Film Evaporation ◽  
The Heat Transfer Coefficient

Abstract An experimental investigation was conducted on falling film evaporation along two porous tubes, which were sintered by stainless-steel powder with a diameter of 0.45 and 1 um, respectively. The test section is a 2 m long sintered tube with an outer diameter of 25 mm and a wall thickness of 2 mm. During the experiment, the pressure inside the tube was maintained at 1 atm, the inlet temperature was 373 K, and mass flux ranged from 0.51 to 1.36 kg/ (m s). Conditions of the steam outside the pipe, which was the heat source, were fixed, while the fouling tests were carried out at a constant mass flow of 0.74 kg/ (m s) using high-concentration brine as work fluid. The overall heat transfer coefficient under different working conditions was tested and compared with the stainless steel smooth tube of the same dimensions. The heat transfer coefficient of the two porous stainless tubes are about 35% and 20% lower than that of the smooth one, showing an inferior effect because the steam in the pores of the pipe wall during the infiltration process will reduce the heat conductivity. The heat transfer coefficient of the smooth tube deteriorated severely due to the deposition of calcium carbonate, which had little effect on the sintered tubes. Besides, the fouling weight of porous tubes is 2.01 g and 0 g compared with 5.52 g of the smooth tube.

Experimental Study on CaCO3 Fouling Characteristics during Falling Film Evaporation

2021 ◽  
pp. 1-27
Author(s):  
Zhikou Ding ◽  
Wei Li ◽  
Lei Wang ◽  
Limin Zhao ◽  
S.A. Sherif ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Falling Film ◽  
Steel Tubes ◽  
Film Evaporation ◽  
Falling Film Evaporation ◽  
Teflon Coating ◽  
The Heat Transfer Coefficient

Abstract Falling film evaporation is widely used in solar desalination systems. Fouling is an important problem to be addressed in many applications involving heat transfer including processes involving the utilization of solar energy in desalination applications. In the research upon which this paper partly reports, an experimental investigation was carried out on a vertical tube in falling film evaporation to determine the effects of temperature, velocity, the use of a porous-sintered tube, and the use of Teflon coating on calcium carbonate deposition characteristics. During the fouling experiments, the pressure inside the test tubes was maintained constant at 101.3kPa, and the inlet temperature was maintained at 373K, while allowing the water mass velocity to vary from 0.42-1.05kg m−1s−1. Results show that the fouling in the test tube becomes more serious as the temperature increases and the flow rate decreases. Compared with stainless steel tubes, porous-sintered tubes can significantly reduce fouling resistance, but at the same time they bring about a decrease in the heat transfer coefficient. The Teflon coating also has anti-fouling performance, but does not affect the heat transfer coefficient in stainless steel tubes. Through the weighing of local fouling deposits, it has been found that the mass of the fouling deposits in the lower part of the tested tubes is greater than that in the upper part.

scholarly journals Spray Cooling Heat Transfer above Leidenfrost Temperature

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1270
Author(s):  
Martin Chabicovsky ◽  
Petr Kotrbacek ◽  
Hana Bellerova ◽  
Jan Kominek ◽  
Miroslav Raudensky
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Correlation Functions ◽  
Spray Cooling ◽  
Impact Pressure ◽  
Good Prediction ◽  
Spray Parameters ◽  
Cooling Intensity ◽  
Leidenfrost Temperature

This study considers spray cooling starting at surface temperatures of about 1200 °C and finishing at the Leidenfrost temperature. Cooling is in the film boiling regime. The paper uses experimental techniques for the study of which spray parameters are necessary for good prediction of spray cooling intensity. The research is based on experiments with water and air-mist nozzles. The following spray parameters were measured together with a heat transfer coefficient: water flowrate, water impingement density, impact pressure, droplet size and velocity. Derived parameters as droplet kinetic energy, droplet momentum and droplet Reynolds number are used in the tested correlations as well. Ten combinations of spray parameters used for correlation functions for the heat transfer coefficient (HTC) are studied and discussed. Correlation functions for prediction of HTC are presented and it is shown which spray parameters are necessary for reliable computation of HTC. The best results were obtained when the parameters impact pressure and water impingement density were used together. It was proven that the correlations based only on water impingement density, which are the most frequent in literature, can not provide reliable results.

Experimental investigation into spray cooling heat transfer performance of Al2O3-water nanofluid with different subcooling degrees

2021 ◽  
pp. 095440892110378
Author(s):  
Tong-Bou Chang ◽  
Tsung-Han Lin ◽  
Jhong-Wei Huang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Gradual Increase ◽  
Heated Surface ◽  
Operating Time ◽  
Spray Cooling ◽  
Transfer Performance ◽  
The Heat Transfer Coefficient

This study investigated the spray cooling heat transfer performance of Al2O3-water nanofluid given four different subcooling degrees (0 °C, 10 °C, 20 °C, and 30 °C). The results showed that the subcooled nanofluids were ranked in order of a reducing spray cooling heat transfer performance as follows: 20 °C, 10 °C, 0 °C, and 30 °C. On average, the heat transfer coefficient obtained using the nanofluid with 20 °C subcooling was around 8.3%, 8.6%, and 15.6% higher than that obtained with 10 °C, 0 °C, and 30 °C subcooling, respectively. However, the heat transfer performance decreased with an increasing spray operating time. The scanning electron microscopy observations showed that the reduction in the heat transfer coefficient was the result of a gradual increase in the thickness of the nano-adsorption layer on the heated surface as the spray operating time increased.

High-Cycle Thermal Fatigue in Mixing Zones: Investigations on Heat Transfer Coefficient and Temperature Fields in PWR Mixing Configurations

2010 ◽  
Author(s):  
Jean-Philippe Fontes ◽  
Olivier Braillard ◽  
Olivier Cartier ◽  
Sylvain Dupraz
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Fatigue ◽  
Experimental Program ◽  
Fluid Temperature ◽  
Mixing Zone ◽  
High Cycle Thermal Fatigue ◽  
The Heat Transfer Coefficient

Piping systems of nuclear power plants include connections of branches conveying fluids at different temperatures. Thermal-hydraulic fluctuations arising from the turbulent mixing of the flows can affect the inner wall of the pipes and lead to fatigue damage. In order to assess the high-cycle thermal fatigue damages risks of the NPP mixing zones, knowledge of the temperature fluctuations and heat transfer from fluid to structure is necessary. In order to have a better knowledge of the thermal loadings in the several kinds of mixing zones of a NPP, a multi-annual R&D program has been initiated by EDF, AREVA and CEA. The experimental program uses two kinds of representative small-scale mock-ups which are called “Skin of Fluid” and “Stainless Steel FATHERINO”, for different mixing configurations. “Skin of Fluid” mock-ups are very thin ones, made of brass material, allowing visualization with an infrared camera of the fluid temperature field in the mixing zone, with minimized thermal attenuation. As a consequence, “Skin of Fluid” mock-ups allow detecting areas of interest in the mixing zone. “Stainless Steel FATHERINO” mock-ups are then used to evaluate quantitatively the thermal fluctuations and the heat transfer coefficient in the mixing zone. “Stainless Steel FATHERINO” mock-ups are made of 304L stainless steel and are 9.5mm thick. The mock-ups are instrumented with specific sensors named “Coefh”. These sensors allow measuring simultaneously the fluid and structure temperature time-histories and thus determining the heat transfer coefficient. This paper describes the experimental program and the approach used to evaluate the thermal load in the mixing zones. As an example, the application of this approach to an equal T-junction is presented hereafter.

Evaporation of lignin-lean black liquor

TAPPI Journal ◽  
2015 ◽  
Vol 14 (7) ◽  
pp. 441-450
Author(s):  
HENRIK WALLMO, ◽  
ULF ANDERSSON ◽  
MATHIAS GOURDON ◽  
MARTIN WIMBY
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Black Liquor ◽  
Salt Content ◽  
Solubility Limit ◽  
Lignin Removal ◽  
Kraft Black Liquor ◽  
Black Liquors ◽  
The Heat Transfer Coefficient

Many of the pulp mill biorefinery concepts recently presented include removal of lignin from black liquor. In this work, the aim was to study how the change in liquor chemistry affected the evaporation of kraft black liquor when lignin was removed using the LignoBoost process. Lignin was removed from a softwood kraft black liquor and four different black liquors were studied: one reference black liquor (with no lignin extracted); two ligninlean black liquors with a lignin removal rate of 5.5% and 21%, respectively; and one liquor with maximum lignin removal of 60%. Evaporation tests were carried out at the research evaporator in Chalmers University of Technology. Studied parameters were liquor viscosity, boiling point rise, heat transfer coefficient, scaling propensity, changes in liquor chemical composition, and tube incrustation. It was found that the solubility limit for incrustation changed towards lower dry solids for the lignin-lean black liquors due to an increased salt content. The scaling obtained on the tubes was easily cleaned with thin liquor at 105°C. It was also shown that the liquor viscosity decreased exponentially with increased lignin outtake and hence, the heat transfer coefficient increased with increased lignin outtake. Long term tests, operated about 6 percentage dry solids units above the solubility limit for incrustation for all liquors, showed that the heat transfer coefficient increased from 650 W/m2K for the reference liquor to 1500 W/m2K for the liquor with highest lignin separation degree, 60%.

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