scholarly journals Reforming the Exhaust Passage of Low-pressure Cylinder for 330MW Steam Turbine

2018 ◽  
Vol 38 ◽  
pp. 04015
Author(s):  
Tao Yan ◽  
Wen Cai ◽  
Wen Chen ◽  
Jin Lu ◽  
Yang Hong-yan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Velocity Distribution ◽  
Transfer Coefficient ◽  
Mathematical Simulation ◽  
Steam Turbine ◽  
Temperature Difference ◽  
Performance Test ◽  
Pressure Cylinder ◽  
The Heat Transfer Coefficient

In concern of the velocity distribution of the exhaust passage of 330MW turbine is not uniform, which results in higher the upper temperature difference of the condenser and higher exhaust pressure. It is introduced in this article that based on mathematical simulation, steam-equalizing equipment is augmented at the exhaust area of the condenser which makes the decrease in the steam resistance, much more uniform velocity distribution, and the increase of the heat transfer coefficient. By comparison of the condenser performance test before the amending and after, the result shows that after the amending, the upper temperature difference of the condenser and the exhaust pressure decreases dramatically.

Study on the Effect of the Evaporator Area on the Heat Transfer Performance in the Gravity Feed Liquid Refrigeration System

2013 ◽  
Vol 441 ◽  
pp. 112-115 ◽  
Author(s):  
Qing Jiang Liu ◽  
Fang Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Heat Transfer Performance ◽  
System Optimization ◽  
Transfer Performance ◽  
Refrigeration System ◽  
Original Design ◽  
The Heat Transfer Coefficient

In order to study the effect on heat transfer performance of evaporator in the gravity feed liquid refrigeration system the different evaporator area, the simulation procedure is worked out. The procedure uses the visual basic language. The procedure can figure out the heat transfer coefficient and the temperature difference in different evaporator area and evaporating temperature with the required refrigerating capacity. Through simulation calculation, when the area is 80% of the original design area of evaporator, the evaporator of the heat transfer coefficient and heat transfer temperature difference is the most reasonable and the evaporator of the refrigerating capacity can meet the requirements of cold storage. The program provides the reliable data for the gravity feed liquid cooling system optimization.

Heat Transfer With Insulated Combustion Chamber Walls and Its Influence on the Performance of Diesel Engines

1988 ◽  
Vol 110 (3) ◽  
pp. 482-488 ◽  
Author(s):  
G. Woschni ◽  
W. Spindler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Combustion Chamber ◽  
Fuel Consumption ◽  
Temperature Difference ◽  
Wall Temperature ◽  
Cooling Water ◽  
Great Expectations ◽  
The Heat Transfer Coefficient

Recently great expectations were put into the insulation of combustion chamber walls. A considerable reduction in fuel consumption, a marked reduction of the heat flow to the cooling water, and a significant increase of exhaust gas energy were predicted. In the meantime there exists an increasing number of publications reporting on significant increase of fuel consumption with total or partial insulation of the combustion chamber walls. In [1] a physical explanation of this effect is given: Simultaneously with the decrease of the temperature difference between gas and wall as a result of insulation, the heat transfer coefficient between gas and wall increases rapidly due to increasing wall temperature, thus overcompensating for the decrease in temperature difference between gas and wall. Hence a modified equation for calculation of the heat transfer coefficient was presented [1]. In the paper to be presented here, recent experimental results are reported that confirm the effects demonstrated in [1], including the influence of the heat transfer coefficient, which depends on the wall temperature, on the performance of naturally aspirated and turbocharged engines.

The Experimental Study on the Enhanced Evaporating Property of the Pineapple Juice by Ultrasound

2014 ◽  
Vol 494-495 ◽  
pp. 285-288
Author(s):  
Ji Tian Song ◽  
Xiao Fei Xu ◽  
Wei Tian ◽  
Jian Bo Liu ◽  
Zheng Zhao
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Feed Rate ◽  
Pineapple Juice ◽  
The Heat Transfer Coefficient

In this paper, the heat transfer of pineapple juice was investigated on a new evaporator with ultrasound. The effects of various factors on the heat transfer coefficient were analyzed, including feed rate, evaporating temperature, temperature difference of heat transfer, and juice concentration. The proposals of design and operation for this new evaporation were also discussed.

Numerical Simulation about Heat Transfer Coefficient for the Double Pipe Heat Exchangers

2011 ◽  
Vol 71-78 ◽  
pp. 2577-2580 ◽  
Author(s):  
Hui Fan Zheng ◽  
Jing Bai ◽  
Jing Wei ◽  
Lan Yu Huang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Total Heat Transfer ◽  
Double Pipe ◽  
Heat Exchanges ◽  
The Heat Transfer Coefficient ◽  
Pipe Heat

Based on the EES software, a heat transfer coefficient calculation program about double pipe heat exchanges is established. Some experimental data are compared to the simulation data for proving that the program can predict the heat transfer coefficient of the double pipe heat exchangers, and then the change of heat transfer coefficient is calculated and analyzed with relevant parameters. The results show that the heat transfer coefficient of heat exchanger are increasing with the flow of the shell side, the tube side and the logarithmic mean temperature difference, and when the temperature difference equals to 12°C, the total heat transfer coefficient can up to 2400W/m2.K or so.

Effects of Vapor Velocity and Pressure on Marangoni Condensation of Steam-Ethanol Mixtures on a Horizontal Tube

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Hassan Ali ◽  
Hua Sheng Wang ◽  
Adrian Briggs ◽  
John W. Rose
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Atmospheric Pressure ◽  
Optimum Composition ◽  
Diffusion Resistance ◽  
Vapor Velocity ◽  
The Heat Transfer Coefficient

Careful heat-transfer measurements have been conducted for condensation of steam-ethanol mixtures flowing vertically downward over a horizontal, water-cooled tube at pressures ranging from around atmospheric down to 14 kPa. Care was taken to avoid error due to the presence of air in the vapor. The surface temperature was accurately measured by embedded thermocouples. The maximum vapor velocity obtainable was limited by the maximum electrical power input to the boiler. At atmospheric pressure this was 7.5 m/s while at the lowest pressure a velocity of 15.0 m/s could be achieved. Concentrations of ethanol by mass in the boiler when cold prior to start up were 0.025%, 0.05%, 0.1%, 0.5%, and 1.0%. Tests were conducted for a range of coolant flow rates. Enhancement of the heat-transfer coefficient over pure steam values was found by a factor up to around 5, showing that the decrease in thermal resistance of the condensate due to Marangoni condensation outweighed diffusion resistance in the vapor. The best performing compositions (in the liquid when cold) depended on vapor velocity but were in the range 0.025–0.1% ethanol in all cases. For the atmospheric pressure tests the heat-transfer coefficient for optimum composition, and at a vapor-to-surface temperature difference of around 15 K, increased from around 55 kW/m2 K to around 110 kW/m2 K as the vapor velocity increased from around 0.8 to 7.5 m/s. For a pressure of 14 kPa the heat-transfer coefficient for optimum composition, and at a vapor-to-surface temperature difference of around 9 K, increased from around 70 kW/m2 K to around 90 kW/m2 K as the vapor velocity increased from around 5.0 to 15.0 m/s. Photographs showing the appearance of Marangoni condensation on the tube surface under different conditions are included in the paper.

Simulation and Experimental Study of the Preheating Mould Temperature Distribution in Semi-Solid Diecasting

2021 ◽  
Vol 1035 ◽  
pp. 833-839
Author(s):  
Chao Gao ◽  
Min Luo ◽  
Da Quan Li ◽  
Song Chen ◽  
Jian Feng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Great Influence ◽  
Experimental Result ◽  
Mould Temperature ◽  
Semi Solid ◽  
The Heat Transfer Coefficient

The mould temperature distribution has a great influence on the semi-solid diecasting. In the present study the temperature distribution of a plane-shaped mould was investigated by using the method of numerical simulation and experiment. The results showed that the preheating mould temperature field was affected by three important simulation parameters, the heat transfer coefficient hoil between the heat transfer oil and the mould, the heat transfer coefficient hair between the mould and the air, and the heat transfer coefficient hcontact between the mould core and the mould frame. The simulation results showed that (1) with the increase of hoil, the overall mould temperature imcreased; (2) with the increase of hair, the overall mould temperature decreased, while the surface temperature gradient of mould frame grad T-f and the temperature difference between the mould core and the mould frame ∆T increased; (3) With the increase of hcontact, ∆T decreased and the temperature of mould frame increased. When the heat oil temperature Toil=290°C, the heat transfer coefficients were optimized as hoil=500Wm-2K-1, hair=7Wm-2K-1, and hcontact=1000Wm-2K-1 according to the experimental results. The average temperature difference between the simulation result and the experimental result was 3.45°C, and the average relative error was 1.73%.

Enhancement of Heat Transfer Performance Using Ultrasonic Evaporation

2019 ◽  
Vol 15 (5-6) ◽  
Author(s):  
Jitian Song ◽  
Yongxia Feng ◽  
Wei Tian ◽  
Jianbo Liu ◽  
Yening Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Heat Transfer Performance ◽  
Tap Water ◽  
Ultrasonic Power ◽  
Transfer Performance ◽  
Ultrasonic Technology ◽  
The Heat Transfer Coefficient

AbstractThe ultrasonic evaporator is a new type of evaporation equipment which uses ultrasonic technology to assist evaporation of liquid materials. Due to the lack of mechanism of ultrasonic technology to enhance the heat transfer in evaporation process, there are few reports on the use of ultrasonic evaporator in industrial production. The tap water was selected as experimental material and the heat transfer performance of ultrasonic evaporator was studied. It could be obtained from the single factor analysis that the heat transfer coefficient increased first and then decreased with the increase of ultrasonic power density. The increase of heat transfer due to the increase of temperature difference is basically stable at 20 %. When the ultrasonic wave acts on evaporator, the heat transfer coefficient would increase about 17.06 %–29.85 %. According to the orthogonal test and analysis of variance, it can be obtained that the influence of temperature difference on heat transfer coefficient is the largest, the second is feed flow rate, and evaporation time has the least influence.

Characteristics of Heat Transfer in Rotating Cavities

1998 ◽  
Author(s):  
Anders Jerhamre ◽  
Lars-Erik Eriksson
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Wall Temperature ◽  
Stokes Equations ◽  
Bulk Temperature ◽  
Inlet Temperature ◽  
The Heat Transfer Coefficient

In rotating cavities the driving temperature difference for heat transfer is not easy to define or estimate. Traditionally, some reference temperature, here called bulk temperature, is used. This bulk temperature is closely connected to the heat transfer coefficient. In order to determine these characteristics, the assumption that the wall heat flux is linearly proportional to the temperature difference between wall and inlet air, is used. The slope is equal to the heat transfer coefficient and the x-intercept gives the difference between bulk temperature and inlet temperature. The validity of this assumption is thoroughly investigated by solving the Reynolds averaged Navier-Stokes equations for compressible, axisymmetric flow with a low Reynolds number k-ϵ-model. Rotational and buoyancy effects, which may introduce a non-linear relationship and also affect the local bulk temperature, are all taken into account in the CFD model. Three different cases were investigated: one simple corotating disk cavity; one simple rotor-stator cavity, and finally one real engine application cavity. The rotational Reynolds numbers, mass flow rates and temperature differences were varied. Results indicate that the Linear assumption is valid for a range of wall temperatures but not for regions where the local wall temperature affects the flow field, e.g. in corners. Furthermore, when the flow field undergoes a drastic change, new heat transfer characteristics must be determined, or be used with care. Since the heat transfer coefficient and bulk temperature are uniquely determined by the flow field, and not by the local wall temperature, it is not necessary to make a coupled, continuous calculation of the flow field and thermal distribution in the structure.

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