Effect of Cooling Water Temperature on Impinging Jet Heat Transfer on Hot Steel Plate

2011 ◽  
Author(s):  
Jungho Lee ◽  
Cheong-Hwan Yu ◽  
Kyu Hyung Do
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Water Temperature ◽  
Steel Plate ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Impinging Jet ◽  
Transfer Coefficients ◽  
Cooling Water Temperature ◽  
Jet Cooling

Water impinging jet has been widely used in a variety of engineering applications; especially in the hot steel cooling of steelmaking processes and heat treatment in hot metals. The effects of cooling water temperature on water impinging jet cooling are mainly investigated for hot steel plate cooling in this study. The heat flux are measured by a novel experimental technique that has a function of high-temperature heat flux gauge in which test block assemblies are used to measure the heat flux distributions on the hot surface. The water impinging jet is produced by a straight pipe nozzle and experiments are performed at fixed water flow rate and fixed nozzle-to-target spacing. The results show that effects of water temperature on impinging jet transfer characteristics are presented for five different water temperatures between 5 to 45°C. The heat flux curves and heat transfer coefficients are also provided to a benchmark data for the actual impinging jet cooling applications of hot steel plate.

Effect of Water Temperature on Spray Cooling Heat Transfer on Hot Steel Plate

2010 ◽  
Author(s):  
Jungho Lee ◽  
Cheong-Hwan Yu ◽  
Sang-Jin Park
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Water Temperature ◽  
Steel Plate ◽  
Cooling Water ◽  
Local Heat ◽  
Spray Cooling ◽  
Transfer Coefficients ◽  
Cooling Water Temperature ◽  
Local Heat Flux

Water spray cooling is an important technology which has been used in a variety of engineering applications for cooling of materials from high-temperature nominally up to 900°C, especially in steelmaking processes and heat treatment in hot metals. The effects of cooling water temperature on spray cooling are significant for hot steel plate cooling applications. The local heat flux measurements are introduced by a novel experimental technique in which test block assemblies with cartridge heaters and thermocouples are used to measure the heat flux distribution on the surface of hot steel plate as a function of heat flux gauge. The spray is produced from a fullcone nozzle and experiments are performed at fixed water impact density of G and fixed nozzle-to-target spacing. The results show that effects of water temperature on forced boiling heat transfer characteristics are presented for five different water temperatures between 5 to 45°C. The local heat flux curves and heat transfer coefficients are also provided to a benchmark data for the actual spray cooling of hot steel plate cooling applications.

scholarly journals Development of condenser mathematical model for research and development of ways to improve its efficiency

2020 ◽  
Vol 18 (4) ◽  
pp. 578-585
Author(s):  
Madina Shavdinova ◽  
Konstantin Aronson ◽  
Nina Borissova
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Water Temperature ◽  
Steam Turbine ◽  
Cooling Water ◽  
Laboratory Research ◽  
Thermal Engineering ◽  
Linear Regression Method ◽  
Cooling Water Temperature ◽  
The Mathematical Model

The condensing unit is one of the most important elements of the steam turbine of a combined heat and power plant. Defects in elements of the condensing unit lead to disturbances in the steam turbine operation, its failures and breakdowns, as well as efficiency losses of the plant. Therefore, the operating personnel need to know the cause of the malfunction and to correct it immediately. There are no diagnostic models of condensers in the Republic of Kazakhstan at the moment. In this regard, a mathematical model of a condenser based on the methodology of Kaluga Turbine Plant (KTP) has been developed. The mathematical model makes it possible to change the input parameters, plot dependency diagrams, and calculate the plant efficiency indicators. The mathematical model of the condenser can be used to research ways for the improvement of the condensing unit efficiency, for diagnostic purposes of the equipment condition, for the energy audit conduction of the plant, and in the training when performing virtual laboratory research. Using static data processing by linear regression method we obtain that the KTP methodology of condenser calculation is fair at cooling water temperature from 20 °C to 24 °C, but at cooling water temperature from 20 °C to 28 °C, the methodology of JSC "All-Russia Thermal Engineering Institute" (JSC "VTI") is used. One of the ways to increase the condenser efficiency has been proposed. It is the heat transfer augmentation with riffling annular grooves on tubes. This method increases the heat transfer coefficient by 2%, reduces the water subcooling of the heating steam by 0.9 °C, and decreases the cooling area by 2%.

MEMS Impinging-Jet Cooling

2000 ◽  
Author(s):  
Qiao Lin ◽  
Shuyun Wu ◽  
Yin Yuen ◽  
Yu-Chong Tai ◽  
Chin-Ming Ho
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Jet Cooling

Abstract This paper presents an experimental investigation on MEMS impinging jets as applied to micro heat exchangers. We have fabricated MEMS single and array jet nozzles using DRIE technology, as well as a MEMS quartz chip providing a simulated hot surface for jet impingement. The quartz chip, with an integrated polysilicon thin-film heater and distributed temperature sensors, offers high spatial resolution in temperature measurement due to the low thermal conductivity of quartz. From measured temperature distributions, heat transfer coefficients are computed for single and array micro impinging jets using finite element analysis. The results from this study for the first time provide extensive data on spatial distributions of micro impinging-jet heat transfer coefficients, and demonstrate the viability of MEMS heat exchangers that use micro impinging jets.

Condensation Heat Transfer and Pressure Drop of R-134a Flowing in Annular Helical Pipes at Different Orientations

2003 ◽  
Author(s):  
B. Yu ◽  
C. X. Lin ◽  
M. A. Ebadian ◽  
R. C. Prattipati
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling Water ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Cooling Water Temperature ◽  
Helical Pipe ◽  
R 134A

This paper presents an experimental investigation of condensation heat transfer and pressure drop characteristics of refrigerant R-134a flowing through an annular helicoidal passage with the hydraulic diameter of 8.5 mm. The angles of helix axis are oriented at 0, 45, 90 degrees to gravity. The overall and refrigerant-side heat transfer coefficients and pressure drops are experimentally determined at saturation temperature 35°C, refrigerant mass flux 35–180 kg/s·m2, and cooling water temperature 27°C. The results show that orientation has significant influence on the thermal and hydraulic behaviors of the helical pipe. The results can be employed for reference in the effective design of annular helicoidal heat exchangers with R-134a as the working fluid.

Forced Convection Condensation of Steam on a Small Bank of Horizontal Tubes

1992 ◽  
Vol 114 (3) ◽  
pp. 708-713 ◽  
Author(s):  
A. G. Michael ◽  
W. C. Lee ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Small Bank ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
Cooling Water Flow Rate ◽  
In Series

Heat transfer measurements are reported for condensation of steam flowing vertically downward over a small bank of staggered horizontal tubes having 10 rows with 4 and 3 tubes per row. The tubes in each row were connected in series and separately supplied with cooling water. The cooling water flow rate and temperature rise were measured individually for each row and tube-wall temperatures were measured on selected tubes. Data were obtained at slightly above atmospheric pressure and the range of steam approach velocity (based on the cross-sectional area of the duct) was 6 to 23 m/s. A general trend of decreasing heat transfer coefficient with depth in the bank was found. However, superimposed on this was a “saw-tooth” effect with the three-tube rows having higher coefficients than the rows with four tubes. The amplitude of the coefficient variation decreased down the bank and was also less pronounced at lower vapor velocities. When compared with other experimental data for condensation of steam on small staggered banks, the present data exhibit somewhat higher vapor-side, heat transfer coefficients.

Heat Transfer Characteristics of an Angled Array Impinging Jet on a Concave Duct

2012 ◽  
Author(s):  
Eui Yeop Jung ◽  
Chan Ung Park ◽  
Dong Hyun Lee ◽  
Kyung Min Kim ◽  
Ta-kwan Woo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Stagnation Points ◽  
Transfer Characteristics ◽  
Jet Cooling

This study investigated the heat transfer characteristics of an array jet cooling system on a concave surface. Two types of injection holes were used: one for impinging jets normal to the impingement surface, and the other for angled impinging jets. For the normal jets, the jet Reynolds number (Re) based on the hole diameter varied from 3,000 to 10,000, and the height-to-diameter ratio (H/d) was fixed at 1.0. There were 15 injection holes positioned in a staggered 3×5 array. For the angled jets, Re was set to 5,000 and H/d was also fixed at 1.0. Naphthalene sublimation method was used to determine the heat transfer coefficients on the targeted plates. For normal impinging jet cooling, separate peaks were observed at the stagnation regions due to the curvature effect. Since a crossflow was generated by air spent from the jet arrays, the crossflow effect increased as it moved downstream. Due to the interaction between the crossflow and impinging jets, the peak values at the stagnation points increased downstream. The heat transfer coefficient on the targeted plate increased with Re. The average Sh of the angled jets was higher than that of the normal jets, as the obliquely impinging jet increased the mass flow rate and mass interaction between the jet impingement points.

Experimental Investigation of Condensation Heat Transfer in Annular Helicoidal Pipes at Different Orientations

Volume 3 ◽  
2004 ◽  
Author(s):  
H. L. Mo ◽  
R. Prattipati ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cooling Water ◽  
Saturation Temperature ◽  
Experimental Investigations ◽  
Percentage Increase ◽  
Transfer Coefficients ◽  
Cooling Water Temperature ◽  
Heat Transfer Coefficients ◽  
Mass Flow Rates

Experimental investigations were conducted on condensation of R134a in annular helicoidal pipes with three orientations, 0°, 45° and 90°. The experimental results indicated that the refrigerant heat transfer coefficients increased with the increase of cooling water temperature, mass flow rates of refrigerant and cooling water, and decreased with the increase of saturation temperature of R134a. When the orientation increased from 0° to 90°, the refrigerant Nusselt number increased around 11% at refrigerant Reynolds number of 80, and around 16% at 200, the percentage increase of refrigerant Nusselt number from 0° to 45° accounted for more than two times of that from 45° to 90°. The performance of annular helicoidal pipe was evaluated by comparing with equivalent smooth straight pipe and identical helicoidal pipe.

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