Evaluation of the radiation contribution in short-duration measurements of thermal conductivity by a nonstationary method of hot filament

2000 ◽  
Vol 73 (2) ◽  
pp. 396-402
Author(s):  
G. G. Spirin ◽  
E. A. Strekalova ◽  
D. V. Vasilevskii
Keyword(s):  
Thermal Conductivity ◽  
Short Duration ◽  
Nonstationary Method ◽  
Hot Filament

P1861Influence of thermal conductivity on esophageal protection with a cooling device during high-power short-duration radiofrequency ablation

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
E Kulstad ◽  
M Mercado-Montoya ◽  
S Shah
Keyword(s):  
Thermal Conductivity ◽  
Short Duration ◽  
High Power ◽  
Operating Conditions ◽  
Whole Body ◽  
Esophageal Injury ◽  
Cooling Power ◽  
Protective Effects ◽  
Rf Ablation ◽  
Cooling Device

Abstract Introduction Recent clinical data show that high-power, short-duration (HPSD) radiofrequency (RF) ablation can result in a similar esophageal injury rate as traditional low-power, long-duration (LPLD) ablation. Existing methods to prevent esophageal injury have yielded mixed results and can result in prolonged procedure time, potentially increasing the incidence of post-operative cognitive dysfunction. A new esophageal cooling device currently available for whole-body temperature modulation is being studied for the prevention of esophageal injury during LPLD RF ablation and cryoablation. We sought to develop a mathematical model of HPSD ablation in order to quantify the capability of this new esophageal cooling device to protect from esophageal injury under high-power conditions. Methods Using a model we developed of HPSD RF ablation in the left atrium, we measured the change in esophageal lesion formation and the depth of lesions (measured as percent transmurality) with the esophageal cooling device in place and operating at a temperature from 5°C to 37°C. Tissue parameters, including thermal conductivity, were set to average values obtained from existing literature, and energy settings were evaluated at 50W for between 5 and 10 seconds, and at 90W for a duration of 4 seconds. Results Esophageal injury as measured by percent transmurality was considerably higher at 50W and 10s duration than at 90W of power with 4s duration, although both settings showed potential for esophageal injury. The protective effect of the esophageal cooling device was evident for both cases, with a greater effect when using 50W for 10s (Figure 1). At the coldest device settings, using a 5 min pre-cooling period also reduced the transmurality of the intended atrial lesions. Esophageal protection in HPSD ablation Conclusions Esophageal cooling with a new patient temperature management device shows protective effects against thermal injury during RF ablation across a range of tissue thermal conductivity, using a variety of high-power settings, including 90W applied for 4 seconds. Adjusting the cooling power by adjusting the circulating water temperature in the device allows for a tailoring of the protective effects to operating conditions. Acknowledgement/Funding Attune Medical

Self-Supporting Nanocrystalline Diamond Foils – A New Concept for Crystalline Diamond on any Technical Surface

2010 ◽  
Vol 438 ◽  
pp. 163-169 ◽  
Author(s):  
Matthias A. Lodes ◽  
Stefan M. Rosiwal ◽  
Robert F. Singer
Keyword(s):  
Thermal Conductivity ◽  
Friction And Wear ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
High Hardness ◽  
Nanocrystalline Diamond ◽  
Temperature Sensitive ◽  
Light Metals ◽  
Temperature Application ◽  
Hot Filament

The manufacturing and application of self-supporting nanocrystalline diamond foils is introduced. The high temperature manufacturing of nanocrystalline diamond foils by hot-filament chemical vapour deposition (HFCVD) is separated from the low temperature application, allowing the coating of temperature sensitive materials, which cannot be coated by HFCVD conventionally. By coating appropriate template materials and stripping-off after the CVD-process, self-supporting, flexible nanocrystalline diamond foils with high hardness (> 70 GPa) and very low thermal conductivity (< 1 W/mK) with thicknesses of up to 100 µm can be produced. Lasercutting is an appropriate method for machining any desired geometry. Thus the possibility to use the extreme properties of diamond for protection against friction and wear on new substrate materials, e.g. steels, light metals and polymers, is generated.

Improvement on the Cutting Performance of CVD Diamond Coated Drills in Drilling CFRP

2012 ◽  
Vol 499 ◽  
pp. 366-371 ◽  
Author(s):  
Jian Guo Zhang ◽  
Ben Wang ◽  
Fang Hong Sun ◽  
Hang Gao
Keyword(s):  
Thermal Conductivity ◽  
Wear Resistance ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Cutting Performance ◽  
Reinforced Plastics ◽  
Coated Tool ◽  
Hot Filament

Carbon fiber reinforced plastics (CFRP) is difficult to machine because of the extremely abrasive nature of the carbon fibers and its low thermal conductivity. CVD diamond films have many excellent properties such as wonderful wear resistance, high thermal conductivity and low friction coefficient, therefore depositing diamond films on the surface of drills is thought to be an effective way to elongate the lifetime of drills and improve the cutting performance. In this study, diamond films are deposited on the WC-Co drill using hot filament chemical vapor deposition (HFCVD) method. The results of characterization by the scanning electron microscope (SEM) and Raman spectrum indicate that the fabricated CVD diamond coated drill is covered with a layer of uniform and high-purity diamond films. The cutting performance of as-fabricated CVD diamond coated drill is evaluated in dry drilling CFRP, comparing with the uncoated WC-Co drill. The results demonstrate that the CVD diamond coated drill exhibits much stronger wear resistance. Its flank wear is about 50μm after drilling 30 holes, about one-third of that of WC-Co drill. Machining quality of the exit and internal wall of drilled holes shows better surface finish obtained by coated drill, which suggests that CVD diamond coated tool has great advantages in drilling CFRP.

scholarly journals Evaluation of Physical Characteristics and Sorption of Cement Mortars with Recycled Ceramic Aggregate

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7852
Author(s):  
Agata Stolarska ◽  
Teresa Rucińska
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Thermal Conductivity Coefficient ◽  
Sorption Isotherms ◽  
Sorption Kinetics ◽  
Fine Aggregate ◽  
Air Content ◽  
Nonstationary Method ◽  
Moisture Conditions

The subjects of this study were mortars with varying amounts of recycled ceramic aggregate (RCA). As part of the fine aggregate, the RCA volume share is 10%, 20%, 30%, 50% and 100%. First, fresh mixture parameters were evaluated, such as consistency and air content measurement by pressure method. Next, specimens were molded for compressive strength and flexural strength tests after 7, 28 and 56 days of curing. The thermo-humidity parameters of the composites, i.e., coefficient of capillary action and thermal conductivity coefficient were also investigated using nonstationary method. Sorption kinetics of the mortars at different moisture conditions at 20 °C were also evaluated. Sorption tests were carried out using two methods: TM and DVS. The sorption isotherms were plotted on the basis of equilibrium moisture content for the materials tested. The isotherms obtained by the two methods were evaluated. The results allowed us to draw conclusions on the physical and mechanical parameters of the composites with different amounts of RCA and to evaluate the ability to absorb moisture from the environment by these types of materials. A clear decrease in the compressive strength after 28 days of curing compared to the reference mortar was recorded after using 30% to 100% of RCA (approx. 26% to approx. 39%). Changes in flexural strength were significantly smaller, reaching no more than approx. 7.5%. It was shown that the amount of RCA translates into the ability to sorb moisture, which may affect the application of this type of composites. The amount of RCA translates also into the thermal conductivity coefficient, which decreased with increasing amount of RCA.

Thermal conductivity measurement of liquid materials by a hot-disk method in short-duration microgravity environments

2000 ◽  
Vol 276 (1-2) ◽  
pp. 117-123 ◽  
Author(s):  
Hideaki Nagai ◽  
Fabrice Rossignol ◽  
Yoshinori Nakata ◽  
Takashi Tsurue ◽  
Masaaki Suzuki ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Short Duration ◽  
Conductivity Measurement ◽  
Thermal Conductivity Measurement ◽  
Hot Disk ◽  
Disk Method

scholarly journals Comparison of the Thermal Properties of Geopolymer and Modified Gypsum

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1220
Author(s):  
Karol Prałat ◽  
Justyna Ciemnicka ◽  
Artur Koper ◽  
Katarzyna Ewa Buczkowska ◽  
Piotr Łoś
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Heat Conductivity ◽  
Reference Sample ◽  
Simultaneous Increase ◽  
Heat Conductivity Coefficient ◽  
Nonstationary Method ◽  
Experimental Values ◽  
Physical Quantities

The paper presents the results of research concerning the influence of micromaterials on the heat conductivity coefficient λ, specifically heat Cp and thermal diffusivity a of modified gypsum and geopolymer. Microspheres, hydroxyethyl methylcellulose (HEMC) polymer, and aerogel were used as the gypsum’s modifying materials. The study also investigated an alkali potassium-activated methakaolin-based geopolymer with the addition of aluminium dust. During the measurements of thermal parameters, the nonstationary method was chosen, and an Isomet device—which recorded the required physical quantities—was used. When compared to the reference sample, a decrease in the thermal conductivity and diffusivity of the hardened gypsum— and a simultaneous increase in specific heat—was observed with the addition of micromaterials. The geopolymer sample was characterized by the lowest value of thermal conductivity, equal to 0.1141 W/(m·K). It was over 62% lower than the reference sample containing only gypsum. The experimental values of the thermal conductivity of the gypsum samples with the addition of HEMC, aerogel and microspheres were, respectively, over 23%, 6%, and 8% lower than those of the unmodified gypsum samples. The lowest values of thermal conductivity were observed in the case of the gypsum samples modified with polymer; this resulted from the fact that the polymer caused the greatest change in the structure of the gypsum’s composite, which were expressed by the lowest density and highest porosity.

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