Infrared Imaging of 2-D Temperature Distribution During Cryogen Spray Cooling

2002 ◽  
Vol 124 (6) ◽  
pp. 669-675 ◽  
Author(s):  
Bernard Choi ◽  
Ashley J. Welch
Keyword(s):  
Temperature Distribution ◽  
Spray Cooling ◽  
Temperature Gradients ◽  
Measured Temperature ◽  
Back Side ◽  
Surface Cooling ◽  
Radial Temperature ◽  
Cooling Temperature ◽  
Temperature Distributions ◽  
Cryogen Spray Cooling

Cryogen spray cooling (CSC) is used in conjunction with pulsed laser irradiation for treatment of dermatologic indications. The main goal of this study was to determine the radial temperature distribution created by CSC and evaluate the importance of radial temperature gradients upon the subsequent analysis of tissue cooling throughout the skin. Since direct measurement of surface temperatures during CSC are hindered by the formation of a liquid cryogen layer, temperature distributions were estimated using a thin, black aluminum sheet. An infrared focal plane array camera was used to determine the 2-D backside temperature distribution during a cryogen spurt, which preliminary measurements have shown is a good indicator of the front-side temperature distribution. The measured temperature distribution was approximately gaussian in shape. Next, the transient temperature distributions in skin were calculated for two cases: 1) the standard 1-D solution which assumes a uniform cooling temperature distribution, and 2) a 2-D solution using a nonuniform surface cooling temperature distribution based upon the back-side infrared temperature measurements. At the end of a 100-ms cryogen spurt, calculations showed that, for the two cases, large discrepancies in temperatures at the surface and at a 60-μm depth were found at radii greater than 2.5 mm. These results suggest that it is necessary to consider radial temperature gradients during cryogen spray cooling of tissue.

Dynamic Behavior of Cryogen Spray Cooling: Effect of Spray Distance

2003 ◽  
Author(s):  
G.-X. Wang ◽  
G. Aguilar ◽  
J. S. Nelson
Keyword(s):  
Heat Transfer ◽  
Skin Surface ◽  
Spray Cooling ◽  
Heat Fluxes ◽  
Cooling Effect ◽  
Dermatologic Surgery ◽  
Measured Temperature ◽  
Surface Cooling ◽  
Spray Distance ◽  
Cryogen Spray Cooling

Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser dermatologic surgery. During CSC, skin surface is cooled by a short spurt of refrigerant R134a with boiling point of −26.2°C. Since R134a is volatile in open atmospheric conditions, the atomized liquid droplets undergo continuous evaporation as they fly in air, leading to a lost momentum and mass. Therefore, the cooling effect of CSC depends strongly on the spray distance between the nozzle and the skin surface (L). The objective of this study was, therefore, to investigate the effect of L on the dynamic heat transfer of CSC. A skin model system made of poly methyl-methacrylate resin (Plexiglass®) is used to simulate CSC during laser dermatologic surgery. A fast-response temperature measurement sensor is built using thin (20 μm) aluminum foil and placed on top of the plexiglass with a 50 μm bead diameter thermocouple positioned in between. Variation of the surface temperature is then measured under various spray distances. The surface heat flux (q) as well as the heat transfer coefficient (h) between the surface and the cryogen is estimated by solving an inverse heat conduction problem with the measured temperature data as input. The effect of L on surface cooling in CSC is then investigated systematically. Both the estimated q and h show strong dynamic characteristics and are strong functions of the L. Two distinct spray-surface interaction mechanisms are identified within the spray distances studied. For short L (< 30 mm), the spurt droplets impinge on the substrate violently, resulting in a fairly thin cryogen film deposited on the surface. Strong dynamics and high q result in this case, corresponding to a high h as well. Interestingly, h becomes strongly fluctuating and even larger after spurt termination for these cases. For long L (> 30 mm), q is lower and it steadily decreases after spurt termination. The dynamic variation of h in this case is similar to that of q. These results should help in the selection of optimal CSC parameters, which are needed to produce high heat fluxes at the skin surface and thus obtain maximal epidermal protection during various dermatologic laser therapies.

scholarly journals Calculations of Velocity and Temperature in a Polar Glacier using the Finite-Element Method

1979 ◽  
Vol 24 (90) ◽  
pp. 131-146 ◽  
Author(s):  
Roger LeB. Hooke ◽  
Charles F. Raymond ◽  
Richard L. Hotchkiss ◽  
Robert J. Gustafson
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Temperature Distribution ◽  
Differential Equations ◽  
Boundary Conditions ◽  
Velocity Distribution ◽  
Vertical Velocity ◽  
Measured Temperature ◽  
Temperature Distributions ◽  
Flow Law

AbstractNumerical methods based on quadrilateral finite elements have been developed for calculating distributions of velocity and temperature in polar ice sheets in which horizontal gradients transverse to the flow direction are negligible. The calculation of the velocity field is based on a variational principle equivalent to the differential equations governing incompressible creeping flow. Glen’s flow law relating effective strain-rateε̇ and shear stressτbyε̇ = (τ/B)nis assumed, with the flow law parameterBvarying from element to element depending on temperature and structure. As boundary conditions, stress may be specified on part of the boundary, in practice usually the upper free surface, and velocity on the rest. For calculation of the steady-state temperature distribution we use Galerkin’s method to develop an integral condition from the differential equations. The calculation includes all contributions from vertical and horizontal conduction and advection and from internal heat generation. Imposed boundary conditions are the temperature distribution on the upper surface and the heat flux elsewhereFor certain simple geometries, the flow calculation has been tested against the analytical solution of Nye (1957), and the temperature calculation against analytical solutions of Robin (1955) and Budd (1969), with excellent results.The programs have been used to calculate velocity and temperature distributions in parts of the Barnes Ice Cap where extensive surface and bore-hole surveys provide information on actual values. The predicted velocities are in good agreement with measured velocities if the flow-law parameterBis assumed to decrease down-glacier from the divide to a point about 2 km above the equilibrium line, and then remain constant nearly to the margin. These variations are consistent with observed and inferred changes in fabric from fine ice with randomc-axis orientations to coarser ice with single- or multiple-maximum fabrics. In the wedge of fine-grained deformed superimposed ice at the margin,Bincreases again.Calculated and measured temperature distributions do not agree well if measured velocities and surface temperatures are used in the model. The measured temperature profiles apparently reflect a recent climatic warming which is not incorporated into the finite-element model. These profiles also appear to be adjusted to a vertical velocity distribution which is more consistent with that required for a steady-state profile than the present vertical velocity distribution.

Fire Test on Two-Way Slab with Two Edges Clamped and Two Edges Simply Supported

2015 ◽  
Vol 744-746 ◽  
pp. 148-151
Author(s):  
Zhi Nian Yang ◽  
Yuan Zhang ◽  
Yang Lei
Keyword(s):  
Temperature Distribution ◽  
Fire Test ◽  
Temperature Gradients ◽  
Experimental Results ◽  
Support Condition ◽  
Simply Supported ◽  
Temperature Distributions ◽  
Displacement Transducers ◽  
Horizontal Displacements ◽  
Clamped Edges

This paper describes the results of a fire test conducted on two-way slab with two edges clamped and two edges simply supported. The details of support condition, arrangement of reinforcement, position of displacement transducers and thermocouple trees are described. The experimental results such as the temperature distributions within the slab, vertical deflections and horizontal displacements are presented. The experimental results show that the temperature distribution along the slab depth was nonlinear and the temperature gradients in the slab were large. Main cracks near the clamped edges occurred on the top surface of the slab. It is shown that two-way slab with two edges clamped and two edges simply supported has good fire resistance.

A Model for the Tool Temperature During Machining With a Rotary Tool

2001 ◽  
Author(s):  
Hossam A. Kishawy ◽  
Andrew G. Gerber
Keyword(s):  
Temperature Distribution ◽  
Rotational Speed ◽  
Measured Temperature ◽  
Tool Rotational Speed ◽  
Tool Temperature ◽  
Radial Temperature ◽  
Conservation Of Energy ◽  
Rotary Tool ◽  
Finite Volume Discretization ◽  
Heat Partitioning

Abstract In this paper a model is developed to analyze heat transfer and temperature distribution resulting during machining with rotary tools. The presented model is based on a finite-volume discretization approach applied to a general conservation of energy statement for the rotary tool and chip during machining. The tool rotational speed is modeled and its effect on the heat partitioning between the tool and the chip is investigated. The model is also used to examine the influence of tool speed on the radial temperature distribution on the tool rake face. A comparison between the predicted and previously measured temperature data shows good agreement. In general the results show that the tool-chip partitioning is influenced dramatically by increasing the tool rotational speed at low to moderate levels of tool speed. Also, there is an optimum tool rotational speed at which further increase in the tool rotational speed increases the average tool temperature.

Design of Mobile Temperature Monitor System for Autobrazer Baseline Calibration

1996 ◽  
Author(s):  
Emmanuel I. Agba ◽  
E. William Jones ◽  
A. Simon Penaherrera ◽  
Bruce Thrift
Keyword(s):  
Heat Exchanger ◽  
Temperature Distribution ◽  
Monitoring System ◽  
Monitor System ◽  
Measured Temperature ◽  
Optimal Distribution ◽  
Process Variables ◽  
Gas Flux ◽  
Temperature Distributions ◽  
Temperature Monitor

Abstract The production of heat exchanger coils involves the brazing of return tubes and hairpins to complete the refrigeration circuit. The knowledge of the temperature distribution within an autobrazer is essential for the control of process variables such as burner alignment, gas/flux mixture and conveyor speed. This paper presents the design of a mobile temperature monitor system to measure temperature distributions for the proces s control of an autobrazer. The physical characteristics of the monitoring system in the area of temperature transducer locations simulate closely the actual characteristics of the brazing process. By comparing a measured temperature distribution with a known optimal distribution, the process variables can be adjusted either manually or automatically to affect the process for maximum brazing efficiency. Presently, process variables are adjusted manually and often these adjustments are not repeatable, resulting in high percentage of production coil rejects and subsequent rework.

scholarly journals Calculations of Velocity and Temperature in a Polar Glacier using the Finite-Element Method

1979 ◽  
Vol 24 (90) ◽  
pp. 131-146 ◽  
Author(s):  
Roger LeB. Hooke ◽  
Charles F. Raymond ◽  
Richard L. Hotchkiss ◽  
Robert J. Gustafson
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Temperature Distribution ◽  
Differential Equations ◽  
Boundary Conditions ◽  
Velocity Distribution ◽  
Vertical Velocity ◽  
Measured Temperature ◽  
Temperature Distributions ◽  
Flow Law

AbstractNumerical methods based on quadrilateral finite elements have been developed for calculating distributions of velocity and temperature in polar ice sheets in which horizontal gradients transverse to the flow direction are negligible. The calculation of the velocity field is based on a variational principle equivalent to the differential equations governing incompressible creeping flow. Glen’s flow law relating effective strain-rate ε̇ and shear stress τ by ε̇ = (τ/B)n is assumed, with the flow law parameter B varying from element to element depending on temperature and structure. As boundary conditions, stress may be specified on part of the boundary, in practice usually the upper free surface, and velocity on the rest. For calculation of the steady-state temperature distribution we use Galerkin’s method to develop an integral condition from the differential equations. The calculation includes all contributions from vertical and horizontal conduction and advection and from internal heat generation. Imposed boundary conditions are the temperature distribution on the upper surface and the heat flux elsewhereFor certain simple geometries, the flow calculation has been tested against the analytical solution of Nye (1957), and the temperature calculation against analytical solutions of Robin (1955) and Budd (1969), with excellent results.The programs have been used to calculate velocity and temperature distributions in parts of the Barnes Ice Cap where extensive surface and bore-hole surveys provide information on actual values. The predicted velocities are in good agreement with measured velocities if the flow-law parameter B is assumed to decrease down-glacier from the divide to a point about 2 km above the equilibrium line, and then remain constant nearly to the margin. These variations are consistent with observed and inferred changes in fabric from fine ice with random c-axis orientations to coarser ice with single- or multiple-maximum fabrics. In the wedge of fine-grained deformed superimposed ice at the margin, B increases again.Calculated and measured temperature distributions do not agree well if measured velocities and surface temperatures are used in the model. The measured temperature profiles apparently reflect a recent climatic warming which is not incorporated into the finite-element model. These profiles also appear to be adjusted to a vertical velocity distribution which is more consistent with that required for a steady-state profile than the present vertical velocity distribution.

Effect of Rake Face Design on Cutting Tool Temperature Distributions

1980 ◽  
Vol 102 (2) ◽  
pp. 123-128 ◽  
Author(s):  
P. K. Wright ◽  
S. P. McCormick ◽  
T. R. Miller
Keyword(s):  
Temperature Distribution ◽  
Cutting Tool ◽  
Contact Length ◽  
Measured Temperature ◽  
Rake Face ◽  
Low Carbon ◽  
Temperature Distributions ◽  
Metallographic Method ◽  
Carbon Iron ◽  
Good Agreement

Turning experiments have been carried out on a low carbon iron using steel tools of different side rake face geometry. Temperature distributions have been determined using a recently developed metallographic method. It has been found that when using tools which have a controlled chip-tool contact length of 0.5 mm. the temperatures are ∼30 per cent lower than when using conventional, 6 deg rake tools and, as a result, tool life is longer. Theoretical equations are described which allow the calculation of the temperature distribution along the chip tool interface and the tribological conditions in this region are also considered in detail. There is good agreement between the calculated and measured temperature distributions.

Characteristics of Heat Transfer During Machining With Rotary Tools

2004 ◽  
Vol 126 (2) ◽  
pp. 404-407 ◽  
Author(s):  
H. A. Kishawy and ◽  
A. G. Gerber
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Rotational Speed ◽  
Measured Temperature ◽  
Tool Rotational Speed ◽  
Radial Temperature ◽  
Conservation Of Energy ◽  
Finite Volume Discretization ◽  
Heat Partitioning ◽  
Good Agreement

In this paper a model is developed to analyze heat transfer and temperature distribution resulting during machining with rotary tools. The presented model is based on a finite-volume discretization approach applied to a general conservation of energy statement for the rotary tool and chip during machining. The tool rotational speed is modeled and its effect on the heat partitioning between the tool and the chip is investigated. The model is also used to examine the influence of tool speed on the radial temperature distribution on the tool rake face. A comparison between the predicted and previously measured temperature data shows good agreement. In general the results show that the tool-chip partitioning is influenced dramatically by increasing the tool rotational speed at low to moderate levels of tool speed. Also, there is an optimum tool rotational speed at which further increase in the tool rotational speed increases the average tool temperature.

Temperature distributions in Nd:YAG (λ=1.32 μm) laser-irradiated cartilage grafts accompanied by cryogen spray cooling

1999 ◽  
Author(s):  
Amir M. Karamzadeh ◽  
Brian J. Wong ◽  
Thomas E. Milner ◽  
Xavier Dao ◽  
B. S. Tanenbaum ◽  
...  
Keyword(s):  
Spray Cooling ◽  
Cartilage Grafts ◽  
Temperature Distributions ◽  
Cryogen Spray Cooling
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