Measurement of Tissue Thermal Conductivity With Variable Thermal Dose During an Electrosurgical Joining Process

2017 ◽  
Author(s):  
Che-Hao Yang ◽  
Samantha Kaonis ◽  
Roland K. Chen ◽  
Wei Li
Keyword(s):  
Thermal Conductivity ◽  
Elevated Temperature ◽  
Heat Transfer Analysis ◽  
Thermal Dose ◽  
Tissue Samples ◽  
Tissue Properties ◽  
Inverse Heat Transfer ◽  
Degree Burn ◽  
Thermal Spread ◽  
Joining Process

Electrosurgical vessel joining is commonly performed in surgical procedures to maintain hemostasis. This process requires elevated temperature to denature the tissue and while compression is applied, the tissue can be joined together. The elevated temperature can cause thermal damages to the surrounding tissues. In order to minimize these damages, it is critical to understand how the tissue properties change and how that affects the thermal spread. This study used porcine aorta arterial tissue to investigate tissue thermal conductivity with variable thermal dose. Seven joining times (0, 0.5, 1, 1.5, 2, 4, and 6 seconds) were used to create different amounts of thermal dose. A hybrid method that uses both experimental measurement and inverse heat transfer analysis was conducted to determine the thermal conductivity of thin tissue samples. In general, the tissue thermal conductivity decreases when thermal dose increases. Accordingly, 36% decrease in tissue thermal conductivity was found when the thermal dose reaches the threshold for second-degree burn (with 2-second joining time). When thermal dose is beyond the threshold of third-degree burn, the tissue thermal conductivity does not decrease significantly. A regression model was also developed and can be used to predict tissue thermal conductivity based on the thermal dose.

Characterization of Tissue Thermal Conductivity During a Tissue Joining Process

2016 ◽  
Author(s):  
Che-Hao Yang ◽  
Yang Liu ◽  
Wei Li ◽  
Roland K. Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Tissue Sample ◽  
Heat Transfer Analysis ◽  
Vessel Sealing ◽  
Inverse Heat Transfer ◽  
Thermal Spread ◽  
Higher Temperature ◽  
Postoperative Problems ◽  
Joining Process

Electrosurgical vessel sealing, a tissue joining process, has been widely used in surgical procedures, such as prostatectomies for bleeding control. The heat generated during the process may cause thermal damages to the surrounding tissues which can lead to detrimental postoperative problems. Having better understanding about the thermal spread helps to minimize these undesired thermal damages. The purpose of this study is to investigate the changes of tissue thermal conductivity during the joining process. We propose a hybrid method combining experimental measurement with inverse heat transfer analysis to determine thermal conductivity of thin tissue sample. Instead of self-heating the tissue by the thermistor, we apply an external cold boundary on the other side of the tissue sample to stimulate a higher temperature gradient without denaturing the tissue in comparison to the heated method. The inverse heat transfer technique was then applied to determine the tissue thermal conductivity. Tissue thermal conductivity at different levels (0%, 25%, 50%, 75%, and 100%) of the joining process was measured. The results show a decreasing trend in tissue thermal conductivity with increasing joining level. When the tissue is fully joined, an average of 60% reduction in tissue thermal conductivity was found.

Thermal Conductivity and Specific Heat Evaluation of Tissue Using Laser

2020 ◽  
Vol 1002 ◽  
pp. 303-310
Author(s):  
Sudad Issam Younis ◽  
Haqi I. Qatta ◽  
Mohammed Jalal Abdul Razzaq ◽  
Khalid S. Shibib
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Specific Heat ◽  
Iterative Procedure ◽  
Input Data ◽  
Maximum Error ◽  
Heat Transfer Analysis ◽  
Long Wavelength ◽  
Inverse Heat Transfer

In this work, an inverse heat transfer analysis was used to determine thermal conductivity and specific heat of tissue using special iteration. A laser with a long wavelength was utilized to impose heat to the tissue. The heat that induced in the sample causes an increase in the temperature of a tissue which is measured by a thermocouple. The readings were used together with that analytically obtained from the solution of the heat equation in an iterative procedure to obtain the thermal properties of tissue. By using this method, accurate thermal conductivity and specific heat of tissue could be obtained. It was found that the maximum error in output result and the error in input data were in the same order and that there was a linear relationship between output and input errors.

Estimation of Effective Thermal Conductivity of Porous Media Utilizing Inverse Heat Transfer Analysis on Cylindrical Configuration

2017 ◽  
Author(s):  
Oscar Fabela ◽  
Sandeep Patil ◽  
Siddarth Chintamani ◽  
Brian H. Dennis
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Media ◽  
Material Properties ◽  
Numerical Optimization ◽  
Optimization Method ◽  
Temperature Measurements ◽  
Heat Transfer Analysis ◽  
Inverse Heat Transfer ◽  
Method Show

This paper describes the application of inverse analysis to estimate the thermal conductivity of a porous material using temperature measurements at the surfaces. Finite volume analysis code is utilized to solve the steady state axisymmetric heat transfer governing energy equation. The analysis code is coupled with a numerical optimization method and is utilized to predict thermal conductivity constant using the measurements. An experimental setup was developed to test a porous media composed of a mixture of small pellets and air. Semi Analytic Complex Variable Method (SACVM) is used to determine the sensitivity of the predicted material properties on the error in temperature measurements. Temperature obtained from experiments, is used as input to inverse method. The objective function is minimization of least squares error between measured experimental and predicted temperatures. Conjugate Gradient Method (CGM) is used to solve the resulting problem. Accurate sensitivities for the CGM were computed by SACVM. Material properties predicted from this method show close agreement with literature.

Effects of Mo and Ni on the thermal conductivity of compacted graphite iron at elevated temperature

2019 ◽  
Vol 32 (5-6) ◽  
pp. 243-251 ◽  
Author(s):  
Dongmei Xu ◽  
Guiquan Wang ◽  
Xiang Chen ◽  
Yanxiang Li ◽  
Yuan Liu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Elevated Temperature ◽  
Compacted Graphite Iron ◽  
Compacted Graphite

scholarly journals Analysis of the energetic/environmental performances of gas turbine plant: Effect of thermal barrier coatings and mass of cooling air

2009 ◽  
Vol 13 (1) ◽  
pp. 147-164 ◽  
Author(s):  
Ion Ion ◽  
Anibal Portinha ◽  
Jorge Martins ◽  
Vasco Teixeira ◽  
Joaquim Carneiro
Keyword(s):  
Thermal Conductivity ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Turbine Blades ◽  
Heat Transfer Analysis ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Barrier Coatings ◽  
Cooling Air Flow ◽  
Cooling Air

Zirconia stabilized with 8 wt.% Y2O3 is the most common material to be applied in thermal barrier coatings owing to its excellent properties: low thermal conductivity, high toughness and thermal expansion coefficient as ceramic material. Calculation has been made to evaluate the gains of thermal barrier coatings applied on gas turbine blades. The study considers a top ceramic coating Zirconia stabilized with 8 wt.% Y2O3 on a NiCoCrAlY bond coat and Inconel 738LC as substrate. For different thickness and different cooling air flow rates, a thermodynamic analysis has been performed and pollutants emissions (CO, NOx) have been estimated to analyze the effect of rising the gas inlet temperature. The effect of thickness and thermal conductivity of top coating and the mass flow rate of cooling air have been analyzed. The model for heat transfer analysis gives the temperature reduction through the wall blade for the considered conditions and the results presented in this contribution are restricted to a two considered limits: (1) maximum allowable temperature for top layer (1200?C) and (2) for blade material (1000?C). The model can be used to analyze other materials that support higher temperatures helping in the development of new materials for thermal barrier coatings.

scholarly journals The Kirchhoff Transformation for Convective-radiative Thermal Problemsin Fins

2021 ◽  
Vol 15 ◽  
pp. 12-21
Author(s):  
Jonatas Motta Quirino ◽  
Eduardo Dias Correa ◽  
Rodolfo do Lago Sobral
Keyword(s):  
Thermal Conductivity ◽  
Boundary Conditions ◽  
Thermal Radiation ◽  
Heat Dissipation ◽  
Variable Thermal Conductivity ◽  
Dirichlet Boundary Conditions ◽  
Heat Transfer Analysis ◽  
Temperature Function ◽  
Kirchhoff Transformation ◽  
Comparison Of The Results

- The present work describes the thermal profile of a single dissipation fin, where their surfaces reject heat to the environment. The problem happens in steady state, which is, all the analysis occurs after the thermal distribution reach heat balance considering that the fin dissipates heat by conduction, convection and thermal radiation. Neumann and Dirichlet boundary conditions are established, characterizing that heat dissipation occurs only on the fin faces, in addition to predicting that the ambient temperature is homogeneous. Heat transfer analysis is performed by computational simulations using appropriate numerical methods. The most of solutions in the literature consider some simplifications as constant thermal conductivity and linear boundary conditions, this work addresses this subject. The method applied is the Kirchhoff Transformation, that uses the thermal conductivity variation to define the temperatures values, once the thermal conductivity variate as a temperature function. For the real situation approximation, this work appropriated the silicon as the fin material to consider the temperature function at each point, which makes the equation that governs the non-linear problem. Finally, the comparison of the results obtained with typical results proves that the assumptions of variable thermal conductivity and heat dissipation by thermal radiation are crucial to obtain results that are closer to reality.

Histopathological Changes of Organs (Lungs, Liver, Kidney, and Brain) After Using Two Types of AgiCoat and Acticoat Nanosilver Dressings on Deep Second-Degree Burn in Rat

2019 ◽  
Vol 41 (1) ◽  
pp. 141-150 ◽  
Author(s):  
Hamid Karimi ◽  
Noor-Ahmad Latifi ◽  
Ali Zare Mehrjerdi ◽  
Babak Jafarnejad ◽  
Ali-Mohammad Karimi
Keyword(s):  
Wound Healing ◽  
Silver Ions ◽  
The Body ◽  
Male Rats ◽  
Histopathological Changes ◽  
Sprague Dawley ◽  
Tissue Samples ◽  
Degree Burn ◽  
Significant Difference ◽  
Second Degree

Abstract Prevention of infections is a very important issue in treating the burn wounds. The nanosilver dressings have many promising advantages, but absorption of silver ions and its adverse effects to the body were always a question. The aim of this study was to compare Silver serum levels and acute toxic effects of nanosilver on histopathology of organs (lungs, liver, kidney, spleen, and brain) in two types of AgiCoat and Acticoat (nanosilver) dressings on second-degree deep burn in rat. This is an experimental study conducted in our animal laboratory. We divided 24 Sprague–Dawley male rats weighing 300 to 350 randomly into two groups. After anesthesia, a second deep-degree burn was made over dorsal skins of rats by standard method. For group A, Agicoat and, for group B, Acticoat dressings were used. The dressings were changed every 3 days with AgiCoat and Acticoat, respectively. After 14 days, we got blood samples and tissue samples taken from heart, liver, kidneys, spleen, lungs, and brain and a sample from dorsal skin of the rat for histopathological examinations. The results showed that the levels of serum silver in both groups were significantly higher than the standard level (1.22 part per million (PM); AgiCoat, P = .017; Acticoat, P = .000), but there was no significant difference between the groups (P = .551). Examination of the relationship between the level of serum silver and histopathological changes in liver showed that hepatotoxicity of AgiCoat was higher compared with Acticoat and the difference was significant (P = .002). There were no pathological changes in brain, kidneys, spleen, heart, and lungs. Wound healing was faster in Acticoat group. The nanosilver dressings can cause toxicity in liver but not in kidney, brain, spleen, heart, and lungs. Liver pathology and hepatotoxicity were more prominent in AgiCoat group. Wound healing was faster in Acticoat group.

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