scholarly journals Effects of sonication and freezing on the color, mechanical and thermophysical properties of osmo-microwave-vacuum dried cranberries

2020 ◽  
Author(s):  
Izabela Anna Staniszewska ◽  
Szymon Staszyński ◽  
Magdalena Zielińska
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Microwave Drying ◽  
Vacuum Drying ◽  
Volumetric Heat Capacity ◽  
Drying Time ◽  
Microwave Vacuum Drying

The aim of study was to determine the effects of sonication (S), convective freezing (F), convective freezing preceded by sonication (SF) as well as cryogenic freezing (N) on the osmo-microwave-vacuum drying kinetics, energy usage and properties of dried cranberries such as moisture content, moisture diffusion, water activity, density, porosity, thermal conductivity, thermal diffusivity, volumetric heat capacity, lightness, redness, yellowness, total differences in color, saturation and hue, hardness, cohesiveness, springiness, and chewiness. Osmo-microwave-vacuum drying of cranberries took from 13.5 to 16.0 min. All initial treatments increased the moisture diffusivity and thus reduced the drying time. The most energy effective method was osmo-microwave-vacuum drying preceded by sonication (S) of fruits. Osmo-microwave-drying of cranberries subjected to convective freezing preceded by sonication (SF) resulted in the highest lightness (32.5 ± 0.5), redness (33.9 ± 0.7), and yellowness (11.3 ± 0.5) of fruits, as well as the lowest cohesion (the lowest resistant to stress associated with manufacturing, packaging, storage, and delivery). The lowest hardness, i.e. 12.3 ± 0.4 N and the highest cohesiveness and springiness, i.e. 0.38 ± 0.02 and 0.74 ± 0.03 of dried fruits, were noted for berries subjected to initial cryogenic freezing (N). Cryogenic freezing (N) combined with osmo-microwave-vacuum drying resulted in the largest color changes of fruits and the highest thermal conductivity. Sonicated and convectively frozen (SF) fruits were characterized by the highest thermal diffusivity. Sonication (S), convective freezing (F) and their combination (SF) significantly reduced the volumetric heat capacity of cranberry fruits.

scholarly journals Application of sonication and freezing as initial treatments before microwave-vacuum drying of cranberries

2019 ◽  
Vol 2 (22) ◽  
pp. 151-167 ◽  
Author(s):  
Izabela Staniszewska ◽  
Szymon Staszyński ◽  
Magdalena Zielińska
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Physical Properties ◽  
Color Change ◽  
Vacuum Drying ◽  
Drying Time ◽  
Dried Fruits ◽  
Microwave Vacuum Drying ◽  
Drying Kinetic

The aim of study was to determine the influence of sonication and freezing on the kinetic of the microwave-vacuum drying, energy consumption and physical properties of whole cranberries as well as evaluate the applicability of sonication instead of freezing in order to change their physical properties and the drying kinetic of whole cranberries. Microwave-vacuum drying of whole cranberries with/without initial treatments took from 12 ± 1 to 14.5 ± 0.5 minutes. All of treatments did not significantly shorten the drying time of cranberries. However, they increased SMER values even by 31%. Despite of cryogenic freezing, all of treatments significantly increased the values of Dew. Sonication combined with drying allowed to obtain dried berries characterized by the lowest cohesiveness (0.19±0.02), springiness (0.62±0.02) and chewiness (3.4±0.8 N), while cryogenic freezing combined with drying allowed to obtain dried fruits characterized by highest springiness (0.75±0.03) and low chewiness (3.3±0.5 N). The highest lightness (32.2±0.7), redness (32.6±0.8), and yellowness (11.1±0.7) were found for fruits subjected to initial convective freezing before drying. The efficiency of sonication in color change was comparable to cryogenic freezing and much lower than convective freezing. All of initial treatments increased such thermal properties of dried cranberries as thermal conductivity and thermal diffusivity.

Effect of timeliness on the thermal properties of paraffin-based Al2O3 nanofluids

2019 ◽  
Vol 33 (05) ◽  
pp. 1950051
Author(s):  
Yangyang Wu ◽  
Baichao Wang ◽  
Dong Li ◽  
Changyu Liu
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Volume Concentration ◽  
Volume Fraction ◽  
Thermal Conversion ◽  
Volumetric Heat Capacity ◽  
Energy Storage Material ◽  
Over Time

Paraffin is an excellent photo-thermal conversion phase change energy storage material, and extensively used in the thermal storage field at the medium-low temperature. However, the low thermal conductivity of paraffin restricts its application in practice. Adding nanoparticles into paraffin is one of the effective methods to improve its thermal conductivity. Nevertheless, the thermal diffusivity, specific heat and volumetric heat capacity of paraffin as well as timeliness were affected after the addition of nanoparticles. In this paper, the influences of volume fraction of Al2O3 nanoparticle and timeliness on these thermal parameters of paraffin were investigated. The results show that the thermal conductivity of paraffin-based Al2O3 nanofluids increases first and then decreases with time, and the maximum thermal conductivity is 0.34 W/[Formula: see text] for volume fraction 1% on third day. The higher volume concentration, the lower specific heat and volumetric heat capacity, all present downtrend over time, until stable in the range of 0.3 MJ/[Formula: see text] and 0.4 MJ/[Formula: see text]. The average enhancement rate of specific heat and volumetric heat capacity are concentrates on −6% to 9%, −10% to 0%, respectively. While increasing the volume concentration, the thermal diffusivity has no obvious regularity, and presents undulatory property over time.

scholarly journals Mechanical, Hygric and Thermal Properties of Flue Gas Desulfurization Gypsum

10.14311/626 ◽  
2004 ◽  
Vol 44 (5-6) ◽  
Author(s):  
P. Tesárek ◽  
J. Drchalová ◽  
J. Kolísko ◽  
P. Rovnaníková ◽  
R. Černý
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Flue Gas ◽  
Linear Thermal Expansion Coefficient ◽  
Linear Thermal Expansion ◽  
Moisture Diffusivity ◽  
Flue Gas Desulfurization ◽  
Volumetric Heat Capacity ◽  
Reference Measurements

The reference measurements of basic mechanical, thermal and hygric parameters of hardened flue gas desulfurization gypsum are carried out. Moisture diffusivity, water vapor diffusion coefficient, thermal conductivity, volumetric heat capacity and linear thermal expansion coefficient are determined with the primary aim of comparison with data obtained for various types of modified gypsum in the future. 

Thermal Diffusivity Measurements on Elastomers

1974 ◽  
Vol 47 (4) ◽  
pp. 849-857 ◽  
Author(s):  
H. K. Frensdorff
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Measurement Method ◽  
Volumetric Heat Capacity ◽  
Raw Data ◽  
Diffusivity Measurements ◽  
Thermal Diffusivities ◽  
Heating Up ◽  
Rubber Article

Abstract Thermal diffusivity, rather than thermal conductivity, is the property which governs rates of heating up and cooling down of a rubber article in the mold. It is preferable to measure it directly, rather than to derive it from separate measurements of thermal conductivity and volumetric heat capacity. A straightforward measurement method is described together with procedures for deriving the required results from the raw data. The sources of error are discussed, and ways for minimizing them are suggested. Thermal diffusivities for gum and black EPDM and fluoroelastomer are reported for temperatures from 0° to 100° C.

Comparison of single and dual probes for measuring soil thermal properties with transient heating

Soil Research ◽  
1994 ◽  
Vol 32 (3) ◽  
pp. 447 ◽  
Author(s):  
KL Bristow ◽  
RD White ◽  
GJ Kluitenberg
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Heat Pulse ◽  
Volumetric Heat Capacity ◽  
Transient Heating ◽  
Single Probe ◽  
Soil Thermal Properties ◽  
Dual Probe

Storage and transfer of heat in soils is governed by the soil thermal properties and these properties are therefore needed in many agricultural and engineering applications. In this paper we discuss solutions of the heat flow equation applicable to single and dual probe transient heating methods, and describe measurements made on air-dry sand to show how these methods can be used to obtain soil thermal properties. Measurements show that the two methods yield similar values of thermal conductivity. When determining thermal conductivity from the single probe data, it is best to use nonlinear curve fitting and to include a correction term in the model to account for the presence of the probe. Measurements of volumetric heat capacity made by using the dual probe heat-pulse method agreed well with independent estimates obtained using the de Vries method of summing the heat capacities of the soil constituents. The advantage of using the dual probe method together with the appropriate heat-pulse theory rather than the single probe is that all three soil thermal properties, the thermal diffusivity, volumetric heat capacity, and thermal conductivity, can be determined from a single heat-pulse measurement. Instantaneous heat-pulse theory can be used with the dual probe method to determine heat capacity from short duration heat-pulse data, but it should not be used to determine the thermal diffusivity and thermal conductivity.

scholarly journals Transient method measured thermal properties of concrete with microspheres and latex based addition

2018 ◽  
Vol 196 ◽  
pp. 04037
Author(s):  
Roman Jaskulski ◽  
Wojciech Kubissa
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Fly Ash ◽  
Thermal Diffusivity ◽  
Thermal Conductivity Coefficient ◽  
Transient Method ◽  
Volumetric Heat Capacity

The goal of the performed research was to determine the influence of microspheres from fly ash and the latex based addition on the thermal properties of concrete. The tested additions were used in two different proportions each and they were combined with each other. As a reference two series of concrete were used: one without any addition and another with 0.2% of air entraining agent. The thermal properties were measured using transient method with ISOMET 2114 apparatus. No clear trends were observed in case of the results of the measurements of the thermal diffusivity and the volumetric heat capacity. While the results of the thermal conductivity coefficient show that both additions has a potential of lowering the thermal conductivity but they are not so efficient as air entraining agent.

Thermal conductivity, thermal diffusivity, and volumetric heat capacity of silicone elastomer nanocomposites

2017 ◽  
Vol 30 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Govind Sahu ◽  
VK Gaba ◽  
S Panda ◽  
B Acharya ◽  
SP Mahapatra
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Temperature Response ◽  
Silicone Elastomer ◽  
Positive Temperature ◽  
Volumetric Heat Capacity ◽  
Multiwalled Carbon

Silicone elastomer (SiR) nanocomposites were prepared using multiwalled carbon nanotubes (MWCNT) and nano-graphite (NG). The morphology of the SiR nanocomposites has been studied using scanning electron microscopy and high-resolution transmission electron microscopy techniques. Detailed analysis of the morphology reveals a uniform distribution of the MWCNT and NG filler particles in the silicone matrix. On increasing the filler loading, a continuous network structure is formed and aggregation takes place. The effect of the MWCNT and NG loadings on the thermal properties of the silicone elastomer has been investigated. The thermal properties of the SiR nanocomposites were measured by a thermal properties analyzer based on the transient hot-wire method. Studies also suggest that incorporation of nanoparticles improves the thermal conductivity of SiR nanocomposites. The thermal conductivity of SiR nanocomposites increased from 0.200 W/(m K) to 0.440 W/(m K) and to 0.310 W/(m K) for 6 wt% MWCNT and NG loadings, respectively. Because of the positive temperature coefficient and the conductive nature of the nanoparticles, the thermal conductivity of the material increased on increasing the temperature. The thermal diffusivity and the volumetric heat capacity of the SiR nanocomposites were measured. The thermal diffusivity of the SiR nanocomposites increased from 0.1194 mm2/s to 0.3209 mm2/s and to 0.2050 mm2/s for 6 wt% MWCNT and NG loadings, respectively. This indicates that the temperature response becomes faster with MWCNT and NG loadings. The volumetric heat capacity of the silicone elastomer nanocomposites decreased from 1.80 MJ/(m3K) to 1.34 MJ/(m3K) and to 1.40 MJ/(m3K) for 6 wt% MWCNT and NG loadings, respectively. Thus, MWCNT particles are more effective in increasing the thermal conductivity and diffusivity of the SiR nanocomposites, when compared to NG fillers at any loading.

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