Shaping high-speed Marangoni flow in liquid films by microscale perturbations in surface temperature

2007 ◽  
Vol 90 (3) ◽  
pp. 034102 ◽  
Author(s):  
Amar S. Basu ◽  
Yogesh B. Gianchandani
Keyword(s):  
Surface Temperature ◽  
High Speed ◽  
Liquid Films ◽  
Marangoni Flow

scholarly journals Operating temperatures of oil-lubricated medium-speed gears: Numerical models and experimental results

2003 ◽  
Vol 217 (2) ◽  
pp. 87-106 ◽  
Author(s):  
H Long ◽  
A A Lord ◽  
D T Gethin ◽  
B J Roylance
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Rotational Speed ◽  
High Speed ◽  
Applied Load ◽  
Frictional Heat ◽  
Transfer Coefficients ◽  
Gear Teeth ◽  
Heat Transfer Coefficients

This paper investigates the effects of gear geometry, rotational speed and applied load, as well as lubrication conditions on surface temperature of high-speed gear teeth. The analytical approach and procedure for estimating frictional heat flux and heat transfer coefficients of gear teeth in high-speed operational conditions was developed and accounts for the effect of oil mist as a cooling medium. Numerical simulations of tooth temperature based on finite element analysis were established to investigate temperature distributions and variations over a range of applied load and rotational speed, which compared well with experimental measurements. A sensitivity analysis of surface temperature to gear configuration, frictional heat flux, heat transfer coefficients, and oil and ambient temperatures was conducted and the major parameters influencing surface temperature were evaluated.

Study of the Fluid Dynamics of Thin Liquid Films Flowing Down a Vertical String With Counterflow of Gas

2015 ◽  
Author(s):  
Zezhi Zeng ◽  
Gopinath Warrier ◽  
Y. Sungtaek Ju
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Film Thickness ◽  
Liquid Film ◽  
Direct Contact ◽  
High Speed ◽  
Small Diameter ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Liquid Coolant

Direct-contact heat transfer between a falling liquid film and a gas stream yield high heat transfer rates and as such it is routinely used in several industrial applications. This concept has been incorporated by us into the proposed design of a novel heat exchanger for indirect cooling of steam in power plants. The DILSHE (Direct-contact Liquid-on-String Heat Exchangers) module consists of an array of small diameter (∼ 1 mm) vertical strings with hot liquid coolant flowing down them due to gravity. A low- or near-zero vapor pressure liquid coolant is essential to minimize/eliminate coolant loss. Consequently, liquids such as Ionic Liquids and Silicone oils are ideal candidates for the coolant. The liquid film thickness is of the order of 1 mm. Gas (ambient air) flowing upwards cools the hot liquid coolant. Onset of fluid instabilities (Rayleigh-Plateau and/or Kapitza instabilities) result in the formation of a liquid beads, which enhance heat transfer due to additional mixing. The key to successfully designing and operating DILSHE is understanding the fundamentals of the liquid film fluid dynamics and heat transfer and developing an operational performance map. As a first step towards achieving these goals, we have undertaken a parametric experimental and numerical study to investigate the fluid dynamics of thin liquid films flowing down small diameter strings. Silicone oil and air are the working fluids in the experiments. The experiments were performed with a single nylon sting (fishing line) of diameter = 0.61 mm and height = 1.6 m. The inlet temperature of both liquid and air were constant (∼ 20 °C). In the present set of experiments the variables that were parametrically varied were: (i) liquid mass flow rate (0.05 to 0.23 g/s) and (ii) average air velocity (0 to 2.7 m/s). Visualization of the liquid flow was performed using a high-speed camera. Parameters such as base liquid film thickness, liquid bead shape and size, velocity (and hence frequency) of beads were measured from the high-speed video recordings. The effect of gas velocity on the dynamics of the liquid beads was compared to data available in the open literature. Within the range of gas velocities used in the experiments, the occurrence of liquid hold up and/or liquid blow over, if any, were also identified. Numerical simulations of the two-phase flow are currently being performed. The experimental results will be invaluable in validation/refinement of the numerical simulations and development of the operational map.

scholarly journals Propellant Combustion Wave Studies by Embedded Thermocouple and Imaging Method at Ambient Pressure

2020 ◽  
Author(s):  
Rakesh Kumar Kalal ◽  
Himanshu Shekhar ◽  
Prashant Sudhir Alegaonkar ◽  
Shrikant Pande
Keyword(s):  
Surface Temperature ◽  
High Speed ◽  
Ambient Pressure ◽  
Combustion Mechanism ◽  
Imaging Method ◽  
Flame Zone ◽  
Sem Images ◽  
Propellant Combustion ◽  
Double Base ◽  
Zone Temperature

This paper discusses the method for propellant combustion studies with embedded thermocouple and imaging method at ambient pressure. In this study, three different propellant compositions are experimentally evaluated for surface temperature, flame zone temperature with embedded thermocouple, and reaction zone thickness with high-speed imaging of propellant during combustion at ambient pressure. Preheat zone and flame zone temperature profiles are recorded with time and surface temperature is determined with available models. Observation of these experiments gives the difference between combustion mechanism of double-base propellant with diethylene glycol dinitrate (DEGDN) and 2,4-dinitrotoluene (DNT), composite propellant (CP) and CP with energetic binder. Scanning electron microscope (SEM) images analysis for pristine and quenched sample is also presented.

A comparative study on the breakup of Newtonian and viscoelastic liquid films

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840032
Author(s):  
Lijuan Qian ◽  
Shaobo Song ◽  
Lisha Jiang ◽  
Xiaolu Li ◽  
Jianzhong Lin
Keyword(s):  
Liquid Film ◽  
High Speed ◽  
Liquid Films ◽  
Viscoelastic Liquid ◽  
Ligament Length ◽  
Time Resolved ◽  
Liquid Bubble ◽  
Mean Size ◽  
The Difference ◽  
The Stability

The breakup of viscoelastic liquid films are investigated experimentally and analytically. The breakup phenomena of viscoelastic liquid film are recorded by the time resolved high speed camera. Video images reveal the difference behavior of liquid bubble breakup for Newtonian and viscoelastic liquid. For the Newtonian liquid, cylindrical ligaments are stretched into droplets with large distributions of drop size. For the viscoelastic liquid, the pinch-off point is located on the liquid connections to the nozzle and finally the main part of the ligament no longer elongates. Furthermore, a dispersion relation based on the stability analysis is involved to predict the ligament length and drop mean size after breakup for liquid film. The calculated ligament length is validated by the measured drop mean size at higher air-to-liquid mass flow ratio.

Experiments on High-Speed Liquid Films Over Downward-Facing Wetting and Nonwetting Surfaces

2003 ◽  
Vol 44 (1) ◽  
pp. 132-137 ◽  
Author(s):  
J. K. Anderson ◽  
M. Yoda ◽  
S. I. Abdel-Khalik ◽  
D. L. Sadowski ◽  
Keyword(s):  
High Speed ◽  
Liquid Films

Investigations of Transient Machined Workpiece Surface Temperature in High Speed Peripheral Milling Using Inverse Method

2012 ◽  
Vol 723 ◽  
pp. 14-19 ◽  
Author(s):  
Zhan Qiang Liu ◽  
Fan Zhang ◽  
Fu Lin Jiang
Keyword(s):  
Heat Source ◽  
Surface Temperature ◽  
High Speed ◽  
Inverse Method ◽  
Moving Heat Source ◽  
Peripheral Milling ◽  
Machined Surface ◽  
Workpiece Temperature ◽  
Surface Temperatures ◽  
1045 Steel

In high speed machining, temperature distribution in workpiece is the main factor which directly affects the surface integrity and dimensional accuracy of machined workpiece. In this paper, the machined workpiece temperature in high speed peripheral milling is analyzed through using moving heat source method and inverse method. Firstly, the workpiece to be machined is considered as a semi-infinite solid to model the transient surface temperature using arc-shaped moving heat source. Inverse method is then applied for the calculating of heat flux. Peripheral milling experiments of 1045 steel is performed with coated carbide insert The machined surface temperatures were measured during experiments. The measured results were found to be in agreement with the predicted ones by transient models for machined surface temperatures. These results confirm the conclusion that the transient workpiece temperature will decline when the cutting speed increases to a critical value.

Thermal imaging of a shattering freezing water droplet

2020 ◽  
Author(s):  
Judith Kleinheins ◽  
Alexei Kiselev ◽  
Alice Keinert ◽  
Thomas Leisner
Keyword(s):  
Surface Temperature ◽  
High Speed ◽  
Water Drop ◽  
Liquid Core ◽  
Video Camera ◽  
Mixed Phase ◽  
Freezing Process ◽  
Underlying Mechanisms ◽  
Ice Production ◽  
Water Saturated

<p>The freezing of a supercooled water drop freely falling through a mixed-phase cloud is an ubiquitous natural process fundamental for the formation of precipitation in clouds. The freezing is known to proceed in two stages: first, a network of ice dendrites spreads across the volume of a supercooled droplet resulting in ultrafast release of latent heat and warming of the droplet up to the melting point of ice; during the second stage a solid ice shell grows from the outside into the droplet, leading to a pressure increase inside the liquid core. Once the pressure gets too high, either the shell cracks open or the droplet explodes. The resulting secondary ice fragments start growing in the water-saturated environment or cause the freezing of neighbouring droplets. This secondary ice production mechanism is important for the rapid glaciation of mixed-phase clouds, however, the details of the underlying mechanisms are poorly understood. To quantify this process of ice multiplication, the evolution of the droplet’s surface temperature during the second freezing stage was investigated with a high-resolution infrared thermography system (INFRATEC). Drops of about 300 µm diameter were levitated in an electrodynamic trap under controlled conditions with respect to temperature, humidity and ventilation. The surface temperature of the droplet was measured with the IR system while the freezing process and shattering of the freezing droplet was recorded by a high-speed video camera. Combining experimental results and comprehensive process modelling, we explore the thermodynamic conditions beneficial for secondary ice production upon freezing of freely falling drizzle droplets.</p>

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