scholarly journals DETERMINATION OF THERMAL PROPERTIES OF COFFEE BEANS AT DIFFERENT DEGREES OF ROASTING

2018 ◽  
Vol 13 (4) ◽  
pp. 498
Author(s):  
Danilo Barbosa Cardoso ◽  
Ednilton Tavares de Andrade ◽  
Renso Alfredo Aragón Calderón ◽  
Mariane Helena Sanches Rabelo ◽  
Camila De Almeida Dias ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Infinite Cylinder ◽  
Element Analysis ◽  
Heating Source ◽  
Mixing Method ◽  
Cylinder Method

<p>The aim of this study was to determine the main thermal properties of the granular mass of coffee (specific heat, thermal conductivity, and thermal diffusivity) for different degrees of roasting, as well as to model and simulate thermal conductivity at different degrees of roasting. For determination of specific heat, the mixing method was used, and for thermal conductivity, the theoretically infinite cylinder method with a central heating source. Thermal diffusivity was simulated algebraically using the results of the properties cited above and of the apparent specific mass of the product. Thermal conductivity was also simulated and optimized through finite element analysis software. At darker roasting, there was an increase in specific heat and a reduction in thermal conductivity and thermal diffusivity. Comparing thermal conductivity determined in relation to simulated and optimized conductivity, the mean relative error was 1.02%, on average.</p>

scholarly journals Determination of Some Selected Thermal Properties of Pumpkin Seeds (Cucurbita pepo)

2021 ◽  
Vol 25 (4) ◽  
pp. 599-604
Author(s):  
M.O. Sunmonu ◽  
M.M. Odewole ◽  
O.A. Adeyinka ◽  
M.S. Sanusi ◽  
S.O. Musa
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Specific Heat ◽  
Average Moisture Content ◽  
Pumpkin Seed ◽  
C Value ◽  
Pumpkin Seeds

In this study, some selected thermal properties (specific heat, thermal conductivity and thermal diffusivity) in the moisture content range of 5.0-5.6% or green and 4.80 – 5.20% for white varieties of pumpkin seeds were determined. The specific heat was measured using mixture method while the thermal conductivity was measured by transient technique using the heat line source. The green pumpkin seed has average moisture content of 5.2% higher than moisture content of white pumpkin seed of average 4.8%. The average specific heat values of green pumpkin seed are 6.171kJ/kgK and white pumpkin seed 4.327kJ/kgK. The thermal conductivity values for white pumpkin seed ranged from 0.074 to 0.288 W/m°C while that for green pumpkin seed ranged from 0.079 to 0.433 W/m°C. The thermal diffusivity values for green pumpkin ranged from 0.0011 to 0.06 m2/s while that for white pumpkin seed ranged from 0.01 to 0.06 m2/s. It was concluded that the higher the moisture content (5.2%) the higher the value of specific heat of seed (6.171kJ/kgK). It can also be concluded that the thermal conductivity (0.079 to 0.433 W/m°C) value is higher with high moisture content (5.2%).

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

Experimental Study on Thermal Properties of Hollow Sphere Structures

2021 ◽  
Vol 407 ◽  
pp. 185-191
Author(s):  
Josef Tomas ◽  
Andreas Öchsner ◽  
Markus Merkel
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Hollow Sphere ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

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%.

Thermal Properties of Thin Metallic Layer Deposited on Insulators: Effect of the Interface on the Independent Determination of the Thermal Diffusivity and Conductivity of the Layer

2008 ◽  
Author(s):  
Danie`le Fournier ◽  
Jean Paul Roger ◽  
Christian Fretigny
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Thermal Resistance ◽  
Thermal Contact ◽  
Heat Diffusion ◽  
Metallic Layer ◽  
Good Thermal Contact ◽  
Lateral Heat

Lateral heat diffusion thermoreflectance is a very powerful tool for determining directly the thermal diffusivity of layered structures. To do that, experimental data are fitted with the help of a heat diffusion model in which the ratio between the thermal conductivity k and the thermal diffusivity D of each layer is fixed, and the thermal properties of the substrate are known. We have shown in a previous work that it is possible to determine independently the thermal diffusivity and the thermal conductivity of a metallic layer deposited on an insulator, by taking into consideration all the data obtained at different modulation frequencies. Moreover, it is well known that to prevent a lack of adhesion of a gold film deposited on substrates like silica, an intermediate very thin (Cr or Ti) layer is deposited to assure a good thermal contact. We extend our previous work: the asymptotic behaviour determination of the surface temperature wave at large distances from the modulated point heat source for one layer deposited on the substrate to the two layers model. In this case (very thin adhesion coating whose thermal properties and thickness are known), it can be establish that the thermal diffusivity and the thermal conductivity of the top layer can still be determined independently. It is interesting to underline that the calculus can also be extended to the case of a thermal contact resistance which has often to be taken into account between two solids. We call thermal resistance a very thin layer exhibiting a very low thermal conductivity. In this case, the three parameters we have to determine are the thermal conductivity and the thermal diffusivity of the layer and the thermal resistance. We will show that, in this case, the thermal conductivity of the layer is always obtained independently of a bound of the couple thermal resistance – thermal diffusivity, the thermal diffusivity being under bounded and the thermal resistance lower bounded. Experimental results on thin gold layers deposited on silica with and without adhesion layers are presented to illustrate the method. Discussions on the accuracy will also be presented.

scholarly journals Effect of moisture content on the thermal properties of Horse-Eye Bean seeds relevant to its processing

2020 ◽  
Vol 45 (4) ◽  
pp. 71-80
Author(s):  
Ide Ejike ◽  
Ike Oluka ◽  
Eze Chukwuka
Keyword(s):  
Thermal Conductivity ◽  
Regression Analysis ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Specific Heat ◽  
Bulk Density ◽  
Food Processing ◽  
Positive Relationship ◽  
Measured Specific Heat

The specific heat, thermal conductivity and thermal diffusivity of the Horse-Eye bean (Mucuna sloanei) were determined as a function of moisture content using the method reported by A.O.A.C (2000). The sample varieties used were the Big Sized and the Small Sized Horse-Eye bean. The specific heat and the thermal conductivity were measured using a Bomb Calorimeter. The thermal diffusivity was calculated from the measured specific heat, thermal conductivity and bulk density of the samples. Within the moisture range of 10.5% to 16.87% (b.b), the specific heat, thermal conductivity and thermal diffusivity varied with the moisture content. Results showed that the specific heat, thermal conductivity and thermal diffusivity of the Horse-Eye bean seeds ranged from 116.76 to 203.29 kJ/kgK; 21.07 to 32.23 W/moC; and 3.12 x 10-7 to 9.19 x 10-7 m 2 /s, for the Big Sized varieties, and 112.06 to 194.61 kJ/kgK; 19.85 to 24.08 W/moC; and 3.05 x 10-7 to 6.71 x 10-7 m 2 /s, for the Small Sized varieties as the moisture content increases from 10.5% to 16.87%. Regression analysis were also carried out on the thermal properties of the Horse-Eye bean varieties and moisture content, and there was positive relationship between the parameters. There were significant effects of moisture content (p < 0.05) on all the parameters conducted. The findings and the data generated will create an impact in the food processing industries for Horse-Eye bean.

The Simultaneous Measurement of Thermal Conductivity, Thermal Diffusivity, and Perfusion in Small Volumes of Tissue

1984 ◽  
Vol 106 (3) ◽  
pp. 192-197 ◽  
Author(s):  
J. W. Valvano ◽  
J. T. Allen ◽  
H. F. Bowman
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Tissue Perfusion ◽  
Effective Thermal Diffusivity ◽  
Liver Preparation ◽  
Improved Technique ◽  
Power Response

An improved technique is presented for the “in-vivo” determination of thermal conductivity, thermal diffusivity, and perfusion using a self-heated spherical thermistor probe. In the presence of flow, solution of the time-dependent, probe-tissue coupled thermal model allows the measurement of “effective” thermal conductivity and “effective” thermal diffusivity, which represent the thermal properties of the perfused tissue. Perfusion can be quantified from both “effective” thermal properties. In the presence of flow, it has been shown that the transient power response does not follow t−1/2 as has been previously assumed. An isolated rat liver preparation has been developed to validate the measurement technique. Radioactive microspheres are used to determine the true perfusion from the total collected hepatic vein flow. Experimental data demonstrates the ability to quantify perfusion in small volumes of tissue.

Thermal Properties of Carbon and Graphite Foams

2012 ◽  
Author(s):  
Melanie Patrick ◽  
Amber Vital ◽  
Darian Bridges ◽  
Messiha Saad
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Flash Method ◽  
Petroleum Pitch ◽  
Energy Storage Devices ◽  
Carbon And Graphite ◽  
Temperature Levels

Thermal properties such as specific heat, thermal diffusivity, and thermal conductivity of carbon and graphite foams are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells. Thermal conductivity is the property that determines the working temperature levels of the material; it plays a critical role in the performance of materials in high temperature applications and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this paper is to develop a thermal properties data base for carbon and graphite foams. Carbon foams are commercially produced from urethane, petroleum pitch-based and coal-based processes, and they typically have large pores (> 350 μm) and low density (< 1.0 g/cm3). Petroleum pitch-base and coal-base carbon/graphite foams can be tailored to be thermally conductive or thermally insulating. The thermophysical properties of carbon and graphite foams have been investigated using experimental methods. The flash method was used to measure the thermal diffusivity of the foams; this method is based on America Society for Testing and Materials standard (ASTM E1461). In addition, the Differential Scanning Calorimeter was used in accordance with the ASTM E1269 standard to measure the specific heat. The measured thermal diffusivity, specific heat, and density data were used to compute the thermal conductivity of the foams.

Sign in / Sign up

Export Citation Format

Share Document