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.

High Resolution Heat Transfer Measurements on the Stator Endwall of an Axial Turbine

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari ◽  
Michael E. Crawford ◽  
Ewald Lutum
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Resolution ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Wall Temperature ◽  
Adiabatic Wall ◽  
Axial Turbine ◽  
The Heat Transfer Coefficient

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular, understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a three-dimensional (3D) airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed Reynolds-Averaged Navier–Stokes (RANS) solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane (NGV) row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by varying the mass flow through the turbine: measurements at the design point (ReCax=7.2×105) and at a reduced mass flow rate (ReCax=5.2×105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage.

Shell-Side Condensation Characteristics of R410A on Horizontal Enhanced Tubes

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Weiyu Tang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Diffusion Resistance ◽  
Outer Diameter ◽  
Vapor Quality ◽  
Enhanced Tubes ◽  
The Heat Transfer Coefficient

Abstract An experimental investigation into heat transfer characteristics during condensation on two horizontal enhanced tubes (EHTs) was conducted. All the tested EHTs s have similar geometries with an outer diameter of 12.7 mm, and a plain tube was also tested for comparison. Investigated enhanced surfaces consist of dimples, protrusions, and grooves, which may produce more flow turbulence and enhanced the liquid drainage effect. The effects of mass fluxes and vapor quality were compared and analyzed. Test conditions were as follows: saturation temperature fixed at 45 °C, mass flux varying from 100 to 200 kg m−2 s−1, and vapor quality ranging from 0.3 to 0.8. The heat transfer coefficient was presented, and the results show that the proposed enhanced surfaces seem to have worse performance than the conventional tubes when the mass flux is less than 150 kg m−2 s−1, while one of the enhanced tubes (2EHT-1) produce an enhanced ratio of 1.03–1.14 when G = 200 kg m−2 s−1. Besides, it was found that the heat transfer coefficient increases with increasing vapor quality, which can be attributed to the increasing diffusion resistance. Mass flux seems to have little effect on the heat transfer performance of smooth tubes, while that of 1EHT increases obviously with increasing mass flux, especially for high vapor qualities.

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.

hADIABATIC and u’MAX

2003 ◽  
Author(s):  
Robert J. Moffat
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Electronics Cooling ◽  
Adiabatic Temperature ◽  
Preliminary Design ◽  
Mean Temperature ◽  
Mixed Mean ◽  
The Heat Transfer Coefficient

In all electronics cooling situations, and many other practical situations, the surface temperature varies in the stream-wise direction. In these cases, defining the heat transfer coefficient using the adiabatic temperature of the surface instead of the mixed mean temperature of the coolant result in significant benefits. The resulting definition is hadiabatic. The theoretical and practical bases for hadiabatic are presented. Examples of its use in electronics cooling are described to show the operational advantages this approach offers. Turbulence strongly affects heat transfer. A simple, turbulence-based correlation is presented that yields an estimate of the heat transfer coefficient good enough for preliminary design estimates and often as accurate as can be relied upon from CFD calculations using present codes.

scholarly journals Heat Transfer Determined by the Temperature Sensitive Paint Method

2018 ◽  
Vol 2018 (4) ◽  
pp. 45-57
Author(s):  
Łukasz Jeziorek ◽  
Krzysztof Szafran ◽  
Paweł Skalski
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Thermal Power ◽  
Test Method ◽  
Temperature Sensitive ◽  
Complex Objects ◽  
Temperature Sensitive Paint ◽  
The Heat Transfer Coefficient

Abstract The paper presents practical aspects of determining the amount of heat flow by measuring the distribution of surface temperature using the Temperature Sensitive Paint (TSP) method. The quantity measured directly with TSP is the intensity of the excited radiation, which is then converted to surface temperature. The article briefly presents three different methods for determining the heat transfer coefficient. Each of these methods is based on a separate set of assumptions and significantly influences the construction of the measuring station. The advantages of each of the presented methods are their individual properties, allowing to improve accuracy, reduce the cost of testing or the possibility of using them in tests of highly complex objects. For each method a mathematical model used to calculate the heat transfer coefficient is presented. For the steady state heat transfer test method that uses a heater of constant and known thermal power, examples of the results of our own research are presented, together with a comparison of the results with available data and a discussion of the accuracy of the results obtained.

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.

Comparison of Surface Heat-Transfer Coefficient of GCr15 Steel Quenched by Clear Water and Nitrogen-Spray Water

2013 ◽  
Vol 444-445 ◽  
pp. 1290-1294
Author(s):  
Li Jun Hou ◽  
He Ming Cheng ◽  
Jian Yun Li ◽  
Bao Dong Shao ◽  
Jie Hou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Thermal Stresses ◽  
Surface Heat ◽  
Water Quenching ◽  
Surface Heat Transfer ◽  
Surface Heat Transfer Coefficient ◽  
The Heat Transfer Coefficient

In order to simulate the thermal stresses, thermal strains and residual stresses of steel during quenching by numerical means, it is necessary to obtain an accurate boundary condition of temperature field. The explicit finite difference method, nonlinear estimate method and the experimental relation between temperature and time during water and nitrogen-spray water quenching have been used to solve the inverse problem of heat conduction. The relations between surface heat-transfer coefficient in water and nitrogen-spray water quenching and surface temperature of cylinder have been given. In numerical calculation, the thermal physical properties of material were treated as the function of temperature. The results show that the relations between surface heat-transfer coefficient and surface temperature are non-linear during water and nitrogen-spray water quenching, the heat-transfer coefficient is bigger when water quenching than when nitrogen-spray water before 580°C, the heat-transfer coefficient is smaller when water quenching than when nitrogen-spray water after 400°C. The results of calculation coincided with the results of experiment. This method can effectively determine the surface heat-transfer coefficient during water and nitrogen-spray water quenching.

High Resolution Heat Transfer Measurements on the Stator Endwall of an Axial Turbine

2014 ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari ◽  
Michael E. Crawford ◽  
Ewald Lutum
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Resolution ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Wall Temperature ◽  
Adiabatic Wall ◽  
Axial Turbine ◽  
The Heat Transfer Coefficient

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a 3D airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed RANS solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot-arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by varying the mass flow through the turbine: measurements at the design point (ReCax = 7,2.105) and at a reduced mass flow rate (ReCax = 5,2.105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage.

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.

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