scholarly journals Thermal behaviour of Norway spruce and European beech in and between the principal anatomical directions

Holzforschung ◽  
2011 ◽  
Vol 65 (3) ◽  
Author(s):  
Walter Sonderegger ◽  
Stefan Hering ◽  
Peter Niemz
Keyword(s):  
Differential Equation ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Norway Spruce ◽  
European Beech ◽  
Hot Plate ◽  
Principal Directions ◽  
Clear Increase ◽  
Plate Apparatus

Abstract Thermal conductivity (ThCond), thermal diffusivity and heat capacity of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) have been determined for all principal directions – radial (R), tangential (T) and longitudinal (L) – depending on the moisture content (MC) and ThCond was additionally measured in 15° steps between these directions. The ThCond was determined in a guarded hot plate apparatus. For determining thermal diffusivity and heat capacity, the same apparatus was supplemented with thermocouples and the temperature evolution was evaluated numerically by a partial differential equation. The results show expectedly that ThCond increases with increasing MC, whereby the highest increment was observed in T and the lowest in L direction. ThCond is higher for beech than for spruce in all anatomical directions and the conductivity for both species is more than twice as high in L direction than perpendicular to grain. The highest ThCond is found for beech at a grain angle of approximately 15°. The lowest ThCond shows spruce at an angle of approximately 60° between T and R direction. Thermal diffusivity is similar for both species and decreases with increasing MC. Its differences with regard to the anatomical directions correlate with those of the ThCond values. Heat capacity is lower for beech than for spruce and shows a clear increase with increasing MC.

Improvements to the Guarded Hot Plate Apparatus to Determine Thermal Conductivity

2017 ◽  
Author(s):  
Gabriel Souza ◽  
Luís Felipe dos Santos Carollo ◽  
Sandro Metrevelle Marcondes de Lima e Silva
Keyword(s):  
Thermal Conductivity ◽  
Hot Plate ◽  
Guarded Hot Plate ◽  
Plate Apparatus

scholarly journals Comparative study of thermal transport in Zea mays straw and Zea mays heartwood (cork) boards

2010 ◽  
Vol 14 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Sunday Etuk ◽  
Louis Akpabio ◽  
Ita Akpan
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Zea Mays ◽  
Thermal Diffusivity ◽  
Comparative Study ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Transport ◽  
Insulation Material ◽  
Thermal Absorptivity

Thermal conductivity values at the temperature of 301-303K have been measured for Zea mays straw board as well as Zea mays heartwood (cork) board. Comparative study of the thermal conductivity values of the boards reveal that Zea mays heartwood board has a lower thermal conductivity value to that of the straw board. The study also shows that the straw board is denser than the heartwood board. Specific heat capacity value is less in value for the heartwood board than the straw board. These parameters also affect the thermal diffusivity as well as thermal absorptivity values for the two types of boards. The result favours the two boards as thermal insulators for thermal envelop but with heartwood board as a preferred insulation material than the straw board.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

Study of the Thermophysical Characteristics of Steel Fiber Reinforced Concrete

2020 ◽  
Vol 992 ◽  
pp. 41-47
Author(s):  
I.L. Shubin ◽  
V.A. Dorf ◽  
R.O. Krasnovskij ◽  
D.E. Kapustin ◽  
P.S. Sultygova
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Reinforced Concrete ◽  
Thermal Diffusivity ◽  
Fire Resistance ◽  
Steel Fiber ◽  
Fiber Reinforced Concrete ◽  
Steel Fiber Reinforced Concrete ◽  
Thermophysical Characteristics ◽  
Volumetric Content

The number of researches on steel fiber reinforced concrete (SFRC) fire resistance is insignificant. For the calculation of building structures for fire resistance, it is necessary to use the thermophysical characteristics of concrete: thermal conductivity, heat capacity and thermal diffusivity. The physicomechanical characteristics of SFRC depend on the volumetric content of the fiber in it. This paper presents the results of studies of thermophysical properties of SFRC. The studied SFRC had a high-strength self-compacting cement-sand matrix and a different percentage of fiber content (from 0 to 6%). The experiments were carried out for SFRC with steel wavy fiber 15 mm long and 0.3 mm in diameter. As a result of experimental studies, it was discovered that with an increase in the volumetric content of the fiber, a decrease in the values of heat flow, thermal conductivity and thermal diffusivity coefficients, specific heat capacity is observed and the thermal resistance of SFRC increases.

scholarly journals Applying the EDPS Method to the Research into Thermophysical Properties of Solid Wood of Coniferous Trees

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Ľuboš Krišťák ◽  
Rastislav Igaz ◽  
Ivan Ružiak
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Thermophysical Properties ◽  
Solid Wood ◽  
Plane Source ◽  
Coniferous Trees ◽  
Extended Dynamic ◽  
Dynamic Plane

The results of using the EDPS (extended dynamic plane source) method to determine thermophysical properties of solid wood of coniferous trees growing in Slovakia with 0% and 12% equilibrium moisture content are presented in the paper. Solid wood of two different tree species: Norway spruce (Picea abies L.) and Scots pine (Pinus sylvestris L.) was used in the research. The research was carried out independently in three anatomical planes. Coefficients of thermal conductivity, thermal diffusivity, and specific heat capacity were determined following the research. Comparing the research results to the values determined by other authors and already published models to calculate individual parameters, the fact that the data gathered using the EDPS method can be accepted in case of all studied thermophysical properties can be stated.

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