Measuring method of three thermophysical parameters of solids by a thermal probe with instantaneous point contact: Discussion about applicability and measuring conditions

It is difficult to measuring conical bore edge sizes (especially big-end)because of its special structure , so the paper put forward a measuring method and a measuring tool based on imaginary crossing point which measure by transforming the point-contact between foot rulers measuring plane and conical bore end plane into imaginary crossing point and installed digital display device . It can measure the conical bore edge sizes directly in field-working and read the value with digital display device directly and used convenience .Its structure is simple and has certain practical value.

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Effects of temperature, test duration and heat flux in thermal conductivity measurements under transient conditions in dry and fully saturated states

E3S Web of Conferences ◽

10.1051/e3sconf/202019504007 ◽

2020 ◽

Vol 195 ◽

pp. 04007

Author(s):

K. Aljundi ◽

A. Vieira ◽

J. Maranha ◽

J. Lapa ◽

R. Cardoso

Keyword(s):

Thermal Conductivity ◽

Measuring Method ◽

Heating Time ◽

Primary Circuit ◽

Test Duration ◽

Conductivity Measurements ◽

Thermal Probe ◽

Transient Conditions ◽

Ambient Temperatures ◽

Shallow Geothermal Energy

In shallow geothermal energy systems (SGES) thermal conduction can be considered the dominant process in the heat transfer between the primary circuit (borehole heat exchanger or thermoactive geostructure) and the surrounding ground. Thus, a proper characterization of soil thermal properties, namely of its thermal conductivity, is mandatory for evaluating this energy exchange. There are difficulties associated to the assessment of soil thermal conductivity by laboratory methods related, among other factors, to the samples’ quality and to the measuring method itself. The purpose of this work is to analyse the effect of changing test control parameters in thermal conductivity measurements in transient conditions by means of a high accuracy thermal probe in both dry and fully saturated states. In order to eliminate potential measurements’ deviations and errors due to sample variability the same reconstituted samples were used several times. In each condition the sand samples were systematically tested under different ambient temperatures (10ºC, 20ºC, and 40ºC) controlled by means of a climatic chamber. The effects of changing the tests heating time and imposed thermal fluxes were also analysed.

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Thermophysical Properties of Baled Switchgrass

Applied Engineering in Agriculture ◽

10.13031/aea.14566 ◽

2021 ◽

Vol 37 (6) ◽

pp. 1107-1114

Author(s):

Drew F Schiavone ◽

Michael D Montross

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Thermal Diffusivity ◽

Specific Heat ◽

Multiple Regression ◽

Thermophysical Properties ◽

Material Properties ◽

Thermal Probe ◽

Transfer Rates ◽

Thermophysical Parameters

HighlightsThermal conductivity and thermal diffusivity of baled switchgrass were measured with a dual thermal probe.Specific heat of baled switchgrass was estimated based on other thermophysical parameters.Thermophysical parameters were modeled as functions of the material properties using multiple regression.Anisotropism was observed with different heat transfer rates occurring in each directional orientation.Abstract.Although the thermophysical properties of baled biomass play a critical role in developing postharvest quality models, these parameters have not been investigated for many bulk agricultural feedstocks including switchgrass. In this study, a dual thermal probe, consisting of a thermal conductivity probe and separate thermal diffusivity probe, was used to determine the thermal conductivity, thermal diffusivity, and specific heat of lab-scale rectangular bales of switchgrass (~10.16 × 10.16 × 30.48 cm). Thermal conductivity, thermal diffusivity, and specific heat ranged from 1.04E-2 to 6.10E-2 W m-1 °C-1, 0.863E-7 to 2.284E-7 m2 s-1, and 0.40 to 2.51 kJ kg-1 °C-1, respectively, depending on temperature (20.3°C, 30.2°C, and 40.1°C), moisture content (11.4%, 20.8%, 29.0%, and 42.3% on a wet basis), bulk density (157.2, 172.4, 197.2, and 230.1 kg m-3) and directional orientation (lateral or transverse). The results of this study promote a practical understanding of heat transfer within baled switchgrass while defining the dynamic relationship to material properties through multiple regression analysis. Anisotropism between the lateral and transverse bale orientations was observed with different heat transfer rates observed in both directional orientations. This anisotropism was attributed to the unique physical composition of the bulk material in the axial direction of bale compression (i.e., variation in porosity, discontinuous porous cavities, and material heterogeneity) compared to the composition of continuous stem material forming a layered flake of the rectangular bale. Keywords: Biomass, Bioprocessing, High solids, Thermal conductivity, Thermal diffusivity.

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