Steady-state thermal measurement of moist granular earthen materials

2016 ◽  
Vol 41 (2) ◽  
pp. 101-119 ◽  
Author(s):  
Robin E Clarke ◽  
Andrea Pianella ◽  
Bahman Shabani ◽  
Gary Rosengarten
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Contact Resistance ◽  
Test Method ◽  
Single Specimen ◽  
Thermal Measurement ◽  
Moisture Contents ◽  
Difference Measurement ◽  
Transient Methods ◽  
Loose Fill

A technique based on the heat flow meter method is proposed for measuring the thermal conductivity of moist earthen and granular loose-fill materials. Although transient methods have become popular, this steady-state approach offers an uncertainty that can be reliably estimated and a test method that is widely accepted for building certification purposes. Variations to the standard method are proposed, including the use of a rigid holding frame with stiff base and silicone sponge buffer sheets, in conjunction with difference measurement to factor out the contributions from base, buffers and contact resistance. Using this approach, results are presented for green-roof substrates based on scoria, terracotta and furnace-ash at different moisture contents. Thermal conductivity ranged from 0.13 to 0.80 W/m K and fitted well to linear regression plots against moisture content. Further comparative measurements of a single specimen showed that direct measurement was less consistent than difference measurement and thus indicated that thermal resistance was higher by 0.023 m2 K/W, attributable to the presence of contact resistance.

A Single Specimen CTOA Test Method for Evaluating the Crack Tip Opening Angle in Gas Pipeline Steels

2004 ◽  
Author(s):  
Sayyed H. Hashemi ◽  
Ian C. Howard ◽  
John R. Yates ◽  
Robert M. Andrews ◽  
Alan M. Edwards
Keyword(s):  
Steady State ◽  
Crack Growth ◽  
Crack Tip ◽  
Gas Pipeline ◽  
Test Method ◽  
Opening Angle ◽  
Single Specimen ◽  
Data Set ◽  
Test Technique ◽  
Pipeline Steels

Failure information from recent full-scale burst experiments on modern TMCP gas pipeline steels having a yield strength level of 690MPa and higher has shown that the CTOA fracture criterion can be effectively used to predict the arrest/propagation behaviour of the pipe against possible axial ductile fractures. The use of CTOA as an alternative or an addition to the Charpy V-notch and DWTT fracture energy in pipelines is currently under review. A significant difficulty currently limiting the more extensive use of CTOA in pipeline assessment is its practical evaluation either in the real structure or in a laboratory scale test. Different combinations of experimental and finite element analyses have been proposed for the measurement of the CTOA of a material. Although most of these models are able to predict the CTOA effectively, their implementation requires extensive calibration processes using the test load-deflection data. The authors have recently developed a novel test technique for direct measurement of the steady state CTOA using a modified double cantilever beam geometry. The technique uses optical imaging to register the uniform deformation of a fine square grid scored on the sides of the specimen. The slope of the deformed gridlines near the crack tip is measured during crack growth from captured images. Its value is a representative of the material CTOA. This paper presents recent results from the implementation of the technique to determine the steady state CTOA (steady state in this work refers to regions of ductile crack growth where CTOA values are constant and independent of crack length) of API X80 and X100 grade gas pipeline steels. In each case the approach was able to produce large amounts of highly consistent CTOA data from both sides of the test sample even from a single specimen. This extensive data set allowed an evaluation of the variance of the stable CTOA as the crack grew through the microstructure. The test method generated a steady CTOA value of 11.1° for X80 and 8.5° for X100 steels tested, respectively.

scholarly journals Measurements of Thermal Conductivity of LWC Cement Composites Using Simplified Laboratory Scale Method

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1351
Author(s):  
Marzena Kurpińska ◽  
Jarosław Karwacki ◽  
Artur Maurin ◽  
Marek Kin
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Foam Glass ◽  
Conductivity Measurement ◽  
Contact Layer ◽  
Material Research ◽  
Cement Composites ◽  
Measuring Device ◽  
Suitable Material ◽  
Transient Methods

The implementation of low-energy construction includes aspects related to technological and material research regarding thermal insulation. New solutions are sought, firstly, to reduce heat losses and, secondly, to improve the environment conditions in isolated rooms. The effective heat resistance of insulating materials is inversely proportional to temperature and humidity. Cement composites filled with lightweight artificial aggregates may be a suitable material. Selecting a proper method for measuring the thermal conductivity of concrete is important to achieve accurate values for calculating the energy consumption of buildings. The steady state and transient methods are considered the two main thermal conductivity measurement approaches. Steady state is a constant heat transfer, whereby the temperature or heat flow is time independent. In the transient method, temperature changes over time. Most researchers have measured the conductivity of cement-based materials based on transient methods. The availability and cost of equipment, time for experimental measurements and measurement ability for moist specimens may be some of the reasons for using this method. However, considering the accuracy of the measurements, the steady state methods are more reliable, especially for testing dry materials. Four types of composites were investigated that differed in filler: natural aggregate, sintered fly ash filler, sintered clay and granular foam glass aggregate. The method of preparing the samples for testing is especially important for the obtained results. The samples, with a specific surface roughness, will show a lower coefficient of thermal conductivity by 20–30%; therefore, the selection of the type of contact layer between the plate of the measuring device and the sample is of particular importance.

Unsaturated flow properties of soils

Soil Research ◽  
1963 ◽  
Vol 1 (1) ◽  
pp. 1 ◽  
Author(s):  
DE Elrick
Keyword(s):  
Steady State ◽  
Diffusion Equation ◽  
Unsaturated Flow ◽  
Diffusion Theory ◽  
Coarse Sand ◽  
Flow Properties ◽  
High Moisture ◽  
Transient Behaviour ◽  
Moisture Contents ◽  
Transient Methods

Experiments to determine the unsaturated flow properties of soils are based either on the steady-state Darcy equation or on the transient diffusion equation. An apparatus has been designed to compare the steady-state and transient methods on the same sample. Results indicate that the transient outflow pattern at high moisture contents (using a coarse sand) differs considerably from that predicted by diffusion theory. The extended theory which takes into account the air as well as the water phase also does not agree with the observed transient behaviour at the high moisture contents. At low moisture contents the agreement between the two methods is considerably better. The transient outflow method was found to be inapplicable at the high moisture contents. Much of the difficulty is attributed to the inaccessibility of air to drainable pores under these conditions.

Advanced Transient Plane Source Method for the Measurement of Thermal Properties of High Pressure Metal Hydrides

2009 ◽  
Author(s):  
Scott Flueckiger ◽  
Tyler Voskuilen ◽  
Yuan Zheng ◽  
Timothe´e Pourpoint
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Effective Thermal Conductivity ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Test Method ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Metal hydrides are a promising material type for hydrogen storage in automotive applications, but thermal property data is needed to optimize the necessary heat exchangers. In the present work, the transient plane source method is integrated with a pressure vessel to measure these properties for metal hydride powder as a function of pressure during the hydrogenation process. The properties under investigation include effective thermal conductivity, thermal diffusivity, specific heat, and thermal contact resistance. The results of this work with oxidized Ti1.1CrMn powder provide effective thermal conductivity values similar to data reported in literature for other metal hydride materials. The experimental measurements are also well modeled by the Zehner-Bauer-Schlu˝nder interpretive model for packed beds as a function of gas pressure. Extending the test method and ZBS model to estimate the contact resistance provides values that were two orders of magnitude less than measurements previously reported for other hydride materials.

Thermal Conductivity for Mixture of Rice Husk Fiber and Gypsum

2016 ◽  
Vol 819 ◽  
pp. 69-73 ◽  
Author(s):  
Mohamad Nor Musa ◽  
Mohamed Fikhri Abdul Aziz
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Rice Husk ◽  
Single Specimen ◽  
Hot Plate ◽  
Plate Method ◽  
One Dimensional ◽  
State Technique ◽  
Application Potential ◽  
Flow Through

This project is conducted with aim to determine the thermal conductivity for mixture of rice husk fiber and gypsum. The thermal conductivity value for 100% gypsum is also determined in this project for comparison purpose. The experiment used the Guarded Hot Plate Method, single specimen apparatus. This method is based on one-dimensional heat flow through conduction and steady state technique. Four samples have been tested which are 100% gypsum with a mass of 1kg for sample 1, a mixture of 0.1kg of rice husk fiber and 1kg gypsum for sample 2, mixture of 0.2kg of rice husk fiber and 1kg gypsum for sample 3 and a mixture of 0.3kg of rice husk fiber and 1kg gypsum for sample 4. From the data of the experiment that have been carried out, the value of thermal conductivity is decreasing with the increasing of rice husk fiber in the sample. The value of thermal conductivity is 0.772W/mK for sample 1, 0.7574 W/mK for sample 2, 0.7469W/mK for sample 3 and 0.7368W/mK for sample 4. The rice husk fiber is a bio-waste material and the mixture of rice husk fiber and gypsum will add value to the material as gypsum are widely used in construction field such as for plaster ingredient and ceiling finishing because it is a good insulator. The mixture of rice husk fiber and gypsum improve the 100% gypsum thermal conductivity and therefore the mixing of these two materials should have bright application potential.

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