scholarly journals Thermal characteristics of dihydroxylammonium 5,5’-bistetrazole-1,1’-diolate in contact with nitrocellulose/nitroglycerine under continuous heat flow

2021 ◽  
pp. 103466
Author(s):  
You Fu ◽  
Xijin Wang ◽  
Yao Zhu ◽  
Bin Xu ◽  
Zhitao Liu ◽  
...  
Keyword(s):  
Heat Flow ◽  
Thermal Characteristics ◽  
Continuous Heat

scholarly journals Experimental investigation of specific cutting forces and estimation of the heat partitioning under increasing tool wear in machining nickel-based super alloy IN 718

2020 ◽  
Vol 14 (4) ◽  
pp. 491-498
Author(s):  
Thorsten Augspurger ◽  
Daniel Schraknepper ◽  
Thomas Bergs
Keyword(s):  
Heat Flow ◽  
Tool Wear ◽  
Cutting Forces ◽  
Chip Thickness ◽  
Milling Process ◽  
Measuring System ◽  
Heat Partitioning ◽  
Wear Monitoring ◽  
Continuous Heat ◽  
Super Alloy

Abstract Presented are an experimental setup and affiliated methodology to measure the specific cutting forces in the milling process with proceeding tool wear at simplified orthogonal milling kinematics. The cutting forces, cutter rotation angle and chip temperature are acquired by a time sensitive measuring system consisting of a synchronized dynamometer, ratio pyrometer and spindle encoder. The approach allows the accurate acquisition of cutting forces under defined engagement conditions and thus constitutes a valuable basis for cutting force modelling and tool wear monitoring approaches. The results show uniformly and linearly increasing forces over the entire range of undeformed chip thickness due to wear. Besides a mechanical view on the cutting process, also the thermal domain was included into the analysis. Therefore, a ratio pyrometer was used as part of the synchronized measurement system tracking the chips backside temperature in order to estimate a virtually continuous heat flow into the chip. This heat flow increased with wear and process power, which indicates that the chip’s temperature can be used as process monitoring variable for tool wear.

scholarly journals ALTERNATIVE METHOD FOR ON SITE EVALUATION OF THERMAL TRANSMITTANCE

2017 ◽  
Vol 15 (2) ◽  
pp. 341 ◽  
Author(s):  
Aleksandar Janković ◽  
Biljana Antunović ◽  
Ljubiša Preradović
Keyword(s):  
Heat Flow ◽  
Thermal Characteristics ◽  
Building Envelope ◽  
Heat Losses ◽  
Flow Meter ◽  
Simple Method ◽  
Building Element ◽  
Thermal Transmittance ◽  
Heat Flow Meter

Thermal transmittance or U-value is an indicator of the building envelope thermal properties and a key parameter for evaluation of heat losses through the building elements due to heat transmission. It can be determined by calculation based on thermal characteristics of the building element layers. However, this value does not take into account the effects of irregularities and degradation of certain elements of the envelope caused by aging, which may lead to errors in calculation of the heat losses. An effective and simple method for determination of thermal transmittance is in situ measurement, which is governed by the ISO 9869-1:2014 that defines heat flow meter method. This relatively expensive method leaves marks and damages surface of the building element. Furthermore, the final result is not always reliable, in particular when the building element is light or when the weather conditions are not suitable. In order to avoid the above mentioned problems and to estimate the real thermal transmittance value an alternative experimental method, here referred as the natural convection and radiation method, is proposed in this paper. For determination of thermal transmittance, this method requires only temperatures of inside and outside air, as well as the inner wall surface temperature. A detailed statistical analysis, performed by the software package SPSS ver. 20, shows several more advantages of this method comparing to the standard heat flow meter one, besides economic and non-destructive benefits.

Minimizing the Wick Thickness in a Planar Microscale Loop Heat Pipe Using Efficient Thermodynamic Design

2011 ◽  
Author(s):  
Navdeep S. Dhillon ◽  
Jim C. Cheng ◽  
Albert P. Pisano
Keyword(s):  
Heat Flow ◽  
Heat Pipe ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Loop Heat Pipes ◽  
Evaporator Section ◽  
Compensation Chamber

Theoretical and numerical thermodynamic analysis of the evaporator section of a planar microscale loop heat pipe is presented, to minimize the permissible wick thickness in such a device. In conventional cylindrical loop heat pipes, a minimum wick thickness is required in order to reduce parasitic heat flow, and prevent vapor leakage, into the compensation chamber. By taking advantage of the possibilities allowed by microfabrication techniques, a planar evaporator/compensation chamber design topology is proposed to overcome this limitation, which will enable wafer-based loop heat pipes with device thicknesses on the order of a millimeter or less. Thermodynamic principles governing two-phase flow of the working fluid in a loop heat pipe are analyzed to elucidate the fundamental requirements that would characterize the startup and steady state operation of a planar phase-change device. A three dimensional finite element thermal-fluid solver is implemented to study the thermal characteristics of the evaporator section and compensation chamber regions of a planar vertically wicking micro-columnated loop heat pipe. The use of in-plane thermal conduction barriers to reduce parasitic heat flow into the compensation chamber is demonstrated.

scholarly journals Thermal Characteristics of the Permafrost within an Active Rock Glacier (Murtèl/Corvatsch, Grisons, Swiss Alps)

1990 ◽  
Vol 36 (123) ◽  
pp. 151-158 ◽  
Author(s):  
Daniel Vonder Mühll ◽  
Wilfried Haeberli
Keyword(s):  
Heat Flow ◽  
Thermal Characteristics ◽  
Thermal Conditions ◽  
Swiss Alps ◽  
Mean Annual Temperature ◽  
Seasonal Temperature ◽  
Rock Glacier ◽  
Vertical Heat ◽  
Glacial Time

AbstractTemperatures from a bore hole through an active rock glacier in the eastern Swiss Alps are presented and thermal conditions within the slowly creeping permafrost are analyzed. Present mean annual temperature in the uppermost part of the permafrost is −3°C. Permafrost is 52 m thick and reaches heavily fissured bedrock. Thermal conductivity as determined in situ from seasonal temperature variations and measured in a cold laboratory using frozen samples is close to 2.5–3.0 W m−1 °C−1. Vertical heat flow is anomalously high (around 150 mW m-2), probably due to heat advection from circulating ground water or air within the fissured bedrock zone. Beneath this zone, which could in fact represent a non-frozen intra-permafrost layer or “talik”, relic permafrost from past centuries may possibly exist as indicated by a corresponding heat-flow inversion. Given the current temperature condition at the surface of the rock glacier and the fact that the twentieth century is among the warmest in post-glacial time, permafrost conditions may be assumed to have existed during the whole of the Holocene and, hence, during the entire time of rock-glacier formation.

scholarly journals Heat Dissipation and Ripple Current Rating in Electrolytic Capacitors

1975 ◽  
Vol 2 (2) ◽  
pp. 109-114 ◽  
Author(s):  
F. G. Hayatee
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Temperature Rise ◽  
Mathematical Analysis ◽  
Heat Dissipation ◽  
Thermal Characteristics ◽  
Electrolytic Capacitors ◽  
Allowable Temperature

The ripple current rating in electrolytic capacitors is limited by the maximum allowable temperature rise inside the capacitor. The temperature rise is determined by the I2R losses inside the capacitor and the efficiency of heat flow from the interior to the surrounding. The ripple current rating can be extended by either reducing the tanδof the capacitor or by increasing the efficiency of heat flow to ambient.The heat flow is determined by the thermal characteristics of the capacitor surface and thermal conductivity of the medium separating the capacitor winding from the surrounding.In this article a mathematical analysis for the heat flow in capacitors is given. The effects of various parameters are examined and methods of extending the ripple current rating are discussed.

Qualitative Geometric Reasoning for Thermal Design Evaluation of Die Casting

2000 ◽  
Author(s):  
Yuming Ma ◽  
Adham Ragab ◽  
Khalil Kabiri ◽  
R. Allen Miller
Keyword(s):  
Heat Flow ◽  
Thermal Characteristics ◽  
Main Idea ◽  
Volume Visualization ◽  
Thermal Control ◽  
Thermal Design ◽  
Geometric Reasoning ◽  
Design Stage ◽  
Prototype System ◽  
Voxel Model

Abstract This paper discusses a qualitative geometric reasoning method which approximately evaluates the equilibrium thermal characteristics of die-castings and dies at the conceptual design stage. The main idea is to apply circuit analog of heat flow on a voxel model and build the heat flow network for the die. An approximate temperature distribution on the die is then obtained by geometric reasoning and thermal resistance computation on voxel model. The resulting temperature field of the die is visualized using volume visualization techniques, and heat converging regions (hot spots) can be identified from the pattern. Thermal control features can then be placed according to the location of the heat converging regions and part thickness. A prototype system has been implemented on Microsoft Windows-NT platform.

scholarly journals Thermal Characteristics of the Permafrost within an Active Rock Glacier (Murtèl/Corvatsch, Grisons, Swiss Alps)

1990 ◽  
Vol 36 (123) ◽  
pp. 151-158 ◽  
Author(s):  
Daniel Vonder Mühll ◽  
Wilfried Haeberli
Keyword(s):  
Heat Flow ◽  
Thermal Characteristics ◽  
Thermal Conditions ◽  
Swiss Alps ◽  
Mean Annual Temperature ◽  
Seasonal Temperature ◽  
Rock Glacier ◽  
Vertical Heat ◽  
Glacial Time

AbstractTemperatures from a bore hole through an active rock glacier in the eastern Swiss Alps are presented and thermal conditions within the slowly creeping permafrost are analyzed. Present mean annual temperature in the uppermost part of the permafrost is −3°C. Permafrost is 52 m thick and reaches heavily fissured bedrock. Thermal conductivity as determinedin situfrom seasonal temperature variations and measured in a cold laboratory using frozen samples is close to 2.5–3.0 W m−1°C−1. Vertical heat flow is anomalously high (around 150 mW m-2), probably due to heat advection from circulating ground water or air within the fissured bedrock zone. Beneath this zone, which could in fact represent a non-frozen intra-permafrost layer or “talik”, relic permafrost from past centuries may possibly exist as indicated by a corresponding heat-flow inversion. Given the current temperature condition at the surface of the rock glacier and the fact that the twentieth century is among the warmest in post-glacial time, permafrost conditions may be assumed to have existed during the whole of the Holocene and, hence, during the entire time of rock-glacier formation.

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