Growth and translation of a liquid-vapour compound drop in a second liquid. Part 2. Heat transfer

1989 ◽  
Vol 209 ◽  
pp. 639-660 ◽  
Author(s):  
S. T. Vuong ◽  
S. S. Sadhal
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Finite Difference Methods ◽  
Time History ◽  
Immiscible Liquid ◽  
Transport Processes ◽  
Contact Heat ◽  
Contact Heat Exchange ◽  
History Of ◽  
Single Compound

The present work is a comprehensive theoretical study of the heat transfer associated with a 3-singlet compound drop that is growing because of change of phase. The geometry is the same as in Part 1, i.e. a vapour bubble partially surrounded by its own liquid in another immiscible liquid. The attempt here is to gain fundamental understanding of the transport processes that take place in connection with direct-contact heat exchange. The fluid dynamics associated with its growth and translation is treated in Part 1. Here, that flow field solution is used to obtain the temperature field and hence the evaporation rate. The energy equation for the system consisting of a single compound drop is solved numerically by finite-difference methods. The results give the complete time history of evaporation of the drop. In addition, useful quantities such as the Nusselt number are given and compared with existing experimental data. Most of the results have good agreement with experimental data.

Comparison of Time-Resolved Turbine Rotor Blade Heat Transfer Measurements and Numerical Calculations

1991 ◽  
Author(s):  
R. S. Abhari ◽  
G. R. Guenette ◽  
A. H. Epstein ◽  
M. B. Giles
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Time History ◽  
Turbine Rotor ◽  
Numerical Calculations ◽  
Test Facility ◽  
Time Resolved ◽  
Turbine Rotor Blade ◽  
History Of

Time-resolved turbine rotor blade heat transfer data are compared with ab initio numerical calculations. The data was taken on a transonic, 4-to-1 pressure ratio, uncooled, single-stage turbine in a short duration turbine test facility. The data consists of the time history of the heat transfer distribution about the rotor chord at midspan. The numerical calculation is a time accurate, 2-D, thin shear layer, multiblade row code known as UNSFLO. UNSFLO uses Ni’s Lax-Wendroff algorithm, conservative boundary conditions, and a time tilting algorithm to facilitate the calculation of the flow in multiple blade rows of arbitrary pitch ratio with relatively little computer time. The version used for this work had a simple algebraic Baldwin-Lomax turbulence model. The code is shown to do a good job of predicting the quantitative time history of the heat flux distribution. The wake/boundary layer and transonic interaction regions for suction and pressure surfaces are identified and the shortcomings of the current algebraic turbulence modelling in the code are discussed. The influence of hardware manufacturing tolerance on rotor heat transfer variation is discussed. A physical reasoning explaining the discrepancies between the unsteady measurement and the calculations for both the suction and pressure surfaces are given, which may be of use in improving future calculations and design procedures.

Characteristics of a Simple Energy Absorption Transducer

1986 ◽  
Vol 108 (3) ◽  
pp. 676-683 ◽  
Author(s):  
B. T. Beck ◽  
G. L. Wedekind
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Laser Radiation ◽  
Steel Substrate ◽  
Time History ◽  
Radiation Absorption ◽  
Flux Analysis ◽  
Manganese Phosphate ◽  
History Of ◽  
Arbitrary Location

This paper presents the results of an investigation into a simple technique developed primarily for evaluating surface coating effectiveness for the absorption of a nonuniform laser radiation heat flux. Analysis suggests that if the transducer sensor is designed appropriately, and the experimental data analyzed in a particular manner, the temperature–time history of the transducer need be measured at only a single arbitrary location. These conclusions are also supported by experimental measurements of laser radiation absorption at a wavelength of 10.6 μm for polished copper, polished steel, and for a manganese–phosphate coating on a steel substrate. The absorptivities measured for the polished copper and steel agree well with other experimental data in the literature. Limitations of the measurement technique, resulting from the temperature dependence of the transducer material properties, radiation absorptivity, and combined convective and radiative heat flux, are also investigated theoretically and experimentally.

Electrically Induced Shape Oscillation of Drops as a Means of Direct-Contact Heat Transfer Enhancement: Part 1—Drop Dynamics

1988 ◽  
Vol 110 (3) ◽  
pp. 695-699 ◽  
Author(s):  
N. Kaji ◽  
Y. H. Mori ◽  
Y. Tochitani
Keyword(s):  
Direct Contact ◽  
Low Frequency ◽  
Immiscible Liquid ◽  
Contact Heat ◽  
Resonant Oscillation ◽  
Liquid Drops ◽  
Contact Heat Exchange ◽  
Second Mode ◽  
Shape Oscillation ◽  
Sinusoidal Waveform

The shape oscillation of liquid drops passing through an immiscible liquid medium subject to a low-frequency (1 ∼ 16 Hz) alternating electric field having a sinusoidal waveform has been studied experimentally with the intention of investigating the enhancement of the direct-contact heat exchange between the two liquids. We have found that the field can induce, depending on its frequency, not only the resonant oscillation of the second mode of the drops, but also another peculiar oscillation that is related to the resonant oscillation of the third mode superposed on the second-mode oscillation.

A Numerical Study to Predict the Effects of Structured Roughness Elements on Pressure Drop and Heat Transfer Enhancement in Minichannels and Microchannels

2011 ◽  
Author(s):  
V. V. Dharaiya ◽  
S. G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Transport Processes ◽  
Transfer Enhancement ◽  
Flow Modification ◽  
Roughness Elements ◽  
Channel Separation

Better understanding of laminar flow at microscale level is gaining importance with recent interest in microfluidics devices. The surface roughness has been acknowledged to affect the laminar flow, and this feature is the focus of the current work to evaluate its potential in heat transfer enhancement. A numerical model is developed to analyze the thermal and hydrodynamic characteristics of minichannels and microchannels in presence of roughness elements. Structured roughness elements following a sinusoidal pattern are generated on two opposed rectangular channel walls with a variable gap. A detailed study is performed to check the effects of roughness height, roughness pitch, and channel separation on pressure drop and heat transfer coefficient in the presence of structured roughness elements. As expected, the structured roughness elements on channel walls result in an increase in pressure drop and heat transfer enhancement as compared to smooth channels due to the combined effects of area enhancement and flow modification. This is due to the fact that the roughness element as a small obstruction in the flow passage of narrow channels which introduces flow modifications in the flow and increases the energy transport. The improvement in global heat transfer enhancement is observed in rough channels due to velocity fluctuations. At the same time, it also causes pressure drop to increase as compared to smooth channels. The fully developed friction factor and Nusselt number results obtained from CFD simulations for smooth and rough channels are compared with the experimental data carried out in the same laboratory. The current numerical scheme is validated with the experimental data and can be used for design and estimation of transport processes in the presence of different roughness features.

Comparison of Time-Resolved Turbine Rotor Blade Heat Transfer Measurements and Numerical Calculations

1992 ◽  
Vol 114 (4) ◽  
pp. 818-827 ◽  
Author(s):  
R. S. Abhari ◽  
G. R. Guenette ◽  
A. H. Epstein ◽  
M. B. Giles
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Time History ◽  
Turbine Rotor ◽  
Numerical Calculations ◽  
Test Facility ◽  
Time Resolved ◽  
Turbine Rotor Blade ◽  
History Of

Time-resolved turbine rotor blade heat transfer data are compared with ab initio numerical calculations. The data were taken on a transonic, 4-to-1 pressure ratio, uncooled, single-stage turbine in a short-duration turbine test facility. The data consist of the time history of the heat transfer distribution about the rotor chord at midspan. The numerical calculation is a time accurate, two-dimensional, thin shear layer, multiblade row code known as UNSFLO. UNSFLO uses Ni’s Lax-Wendroff algorithm, conservative boundary conditions, and a time tilting algorithm to facilitate the calculation of the flow in multiple blade rows of arbitrary pitch ratio with relatively little computer time. The version used for this work had a simple algebraic Baldwin-Lomax turbulence model. The code is shown to do a good job of predicting the quantitative time history of the heat flux distribution. The wake/boundary layer and transonic interaction regions for suction and pressure surfaces are identified and the shortcomings of the current algebraic turbulence modeling in the code are discussed. The influence of hardware manufacturing tolerance on rotor heat transfer variation is discussed. A physical reasoning explaining the discrepancies between the unsteady measurement and the calculations for both the suction and pressure surfaces are given, which may be of use in improving future calculations and design procedures.

Modeling of Advanced Combat Helmet Under Ballistic Impact

2015 ◽  
Vol 82 (11) ◽  
Author(s):  
Y. Q. Li ◽  
X. G. Li ◽  
X.-L. Gao
Keyword(s):  
Experimental Data ◽  
Time History ◽  
Ballistic Impact ◽  
Medium Size ◽  
Lateral Impact ◽  
Ballistic Performance ◽  
Ballistic Impacts ◽  
Large Size ◽  
History Of ◽  
Head Form

The use of combat helmets has greatly reduced penetrating injuries and saved lives of many soldiers. However, behind helmet blunt trauma (BHBT) has emerged as a serious injury type experienced by soldiers in battlefields. BHBT results from nonpenetrating ballistic impacts and is often associated with helmet back face deformation (BFD). In the current study, a finite element-based computational model is developed for simulating the ballistic performance of the Advanced Combat Helmet (ACH), which is validated against the experimental data obtained at the Army Research Laboratory. Both the maximum value and time history of the BFD are considered, unlike existing studies focusing on the maximum BFD only. The simulation results show that the maximum BFD, the time history of the BFD, and the shape and size of the effective area of the helmet shell agree fairly well with the experimental findings. In addition, it is found that ballistic impacts on the helmet at different locations and in different directions result in different BFD values. The largest BFD value is obtained for a frontal impact, which is followed by that for a crown impact and then by that for a lateral impact. Also, the BFD value is seen to decrease as the oblique impact angle decreases. Furthermore, helmets of four different sizes—extra large, large, medium, and small—are simulated and compared. It is shown that at the same bullet impact velocity the small-size helmet has the largest BFD, which is followed by the medium-size helmet, then by the large-size helmet, and finally by the extra large-size helmet. Moreover, ballistic impact simulations are performed for an ACH placed on a ballistic dummy head form embedded with clay as specified in the current ACH testing standard by using the validated helmet model. It is observed that the BFD values as recorded by the clay in the head form are in good agreement with the experimental data.

Direct Contact Heat Exchange Interfacial Phenomena for Liquid Metal Reactors: Part II — Void Fraction

2002 ◽  
Author(s):  
S. Abdulla ◽  
X. Liu ◽  
M. H. Anderson ◽  
R. Bonazza ◽  
M. L. Corradini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Liquid Metal ◽  
Void Fraction ◽  
Direct Contact ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Test Facility ◽  
Contact Heat ◽  
Contact Heat Exchange

One concept being considered for steam generation in innovative nuclear reactor applications, involves water coming into direct contact with a circulating molten metal. The vigorous agitation of the two fluids, the direct liquid-liquid contact and the consequent large interfacial area can give rise to large heat transfer coefficients and rapid steam generation. For an optimum design of such direct contact heat exchange and vaporization systems, detailed knowledge is necessary of the various flow regimes, interfacial transport phenomena, heat transfer and operational stability. In order to investigate the interfacial transport phenomena, heat transfer and operational stability of direct liquid-liquid contact, a series of experiments are being performed in a 1-d test facility at Argonne National Laboratory and a 2-d experimental facility at UW-Madison. Each of the experimental facilities primarily consist of a liquid-metal melt chamber, heated test section (10cm diameter tube for 1-d facility and 10cm × 50cm rectangle for 2-d facility), water injection system and steam suppression tank. This paper is part II which, primarily addresses results and analysis of a set of preliminary experiments and void fraction measurements conducted in the 2-d facility at UW-Madison, part I deals with the heat transfer in the 1-d test facility at Argonne National Laboratory. A real-time high energy X-ray imaging system was developed and utilized to visualize the multiphase flow and measure line-average local void fractions, time-dependent void fraction distribution as well as estimates of the vapor bubble sizes and velocities. These measurements allowed us to determine the volumetric heat transfer coefficient and gain insight into the local heat transfer mechanisms. In this study, the images were captured at frame rates of 100 fps with spatial resolution of about 7mm with a full-field view of a 15cm square and five different positions along the test section height. The full-field average void fraction increases rapidly to about 15% in these preliminary tests, with the apparent boiling length of less than 20cm. The volumetric heat transfer coefficient between the liquid metal and water are compared to the CRIEPI data, the only prior data for direct contact heat exchange for these liquid metal/water systems.

Contact heat exchange in conjunction with metal surfaces which have deviations in form or waviness

2015 ◽  
Vol 5 (4) ◽  
pp. 234-241
Author(s):  
Ерин ◽  
Oleg Erin ◽  
Кондратенко ◽  
Irina Kondratenko ◽  
Попов ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Metal Surfaces ◽  
Calculated Data ◽  
Contact Thermal Resistance ◽  
Contact Heat ◽  
Mechanical Loads ◽  
Physical Experiments ◽  
Contact Heat Exchange ◽  
Constituent Elements

In the design of thermally stressed units in the sectors of mechanical engineering, aviation, aerospace, energetics it is often necessary to have information about the formation of the contact thermal resistance resulting from the discrete nature of parts metal surfaces contacting. While passing through the section zones of heat flows the temperature gradient increases, thus reducing the heat transfer capability of the contact junction and leads to thermal expansion of the constituent elements of the systems, relative shifts and warpages. The process of heat transfer through the zone of contact between metal surfaces having deviation of shapes in the form of nonflatness or waviness under conditions suitable to small mechanical loads is considered. The model of formation of the contact thermal resistance (CTR), in case of double contraction of the heat flow of channel and contact mаcrospots, caused by nonflatness or waviness, and then to microspots caused by roughness. Subject to the provisions of the theory of mechanical contacting of solids theoretical curves is derived describing the contact thermal resistance for compounds with surfaces having microdeviation or waviness operating in the regime of small mechanical loads. The results of physical experiments give satisfactory agreement with the calculated data. It was established that the presence of nonflatness or waviness on the contact surfaces increases CTR significantly as compared with rough surfaces. Increase of CTR is explained by the increase of wave height or equivalent nonflatness

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