In the current study, evolution of thermophysical properties of red chilli dried in a mixed mode solar dryer that integrates sodium sulfate decahydrate (Na
2
SO
4
· 10H
2
O) and sodium chloride ...(NaCl) as thermal storage were presented. Solar drying with Na
2
SO
4
· 10H
2
O reduced the drying time by 26.7 and 39%, compared to the drying time with or without NaCl. Dimensional shrinkage was gradual with a nonlinear exponential shape for the whole drying conditions. The evolution of the bulk and particle densities decreased while the porosity of the seed increased with time. The coefficient of heat and mass transfer varied from 0.0036 − 0.035 W/m
2
K to 6.09 × 10
−9
− 6.2 × 10
−8
m/s, respectively. The thermal conductivity, specific heat capacity, and thermal diffusivity ranged from 0.0568 to 0.1093 W/m K, 1,072 to 2218.7 J/kg K, and 4.7 × 10
−5
to 5.13 × 10
−5
m
2
/s, respectively.
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•Facile synthesis of monophase nanocrystalline BiSbTe1.5Se1.5 HEA by MA and SPS.•Ultra-low thermal conductivity of 0.667 W/mK.•Nanostructured and high entropy show ZT of 0.43 at ...573 K.
The facile synthesis approach combining the mechanical alloying (5 h) and spark plasma sintering (SPS) (11 min) of BiSbTe1.5Se1.5 high entropy alloy (HEA) is reported. High entropy engineering and nanostructuring phenomena synergistically lower the lattice thermal conductivity (<0.2 W/mK) and thermal diffusivity (<0.5 mm2/s) thus results in ultralow thermal conductivity (0.667 W/mK) at 523 K. The synthesized nanostructured HEA offers good power factor (5.51 × 10−4 W/mK2) and figure of merit (ZT) of 0.43 at 523 K.
This work proposes the characterization of the temperature dependence of the thermal properties of heart and lung tissues from room temperature up to > 90 °C. The thermal diffusivity (
α
), thermal ...conductivity (
k
), and volumetric heat capacity (
C
v
) of
ex vivo
porcine hearts and deflated lungs were measured with a dual-needle sensor technique.
α
and
k
associated with heart tissue remained almost constant until ~ 70 and ~ 80 °C, accordingly. Above ~ 80 °C, a more substantial variation in these thermal properties was registered: at 94 °C,
α
and
k
respectively experienced a 2.3- and 1.5- fold increase compared to their nominal values, showing average values of 0.346 mm
2
/s and 0.828 W/(m·K), accordingly. Conversely,
C
v
was almost constant until 55 °C and decreased afterward (
e.g.
,
C
v
= 2.42 MJ/(m
3
·K) at 94 °C). Concerning the lung tissue, both its
α
and
k
were characterized by an exponential increase with temperature, showing a marked increment at supraphysiological and ablative temperatures (at 91 °C,
α
and
k
were equal to 2.120 mm
2
/s and 2.721 W/(m·K), respectively, i.e., 13.7- and 13.1-fold higher compared to their baseline values). Regression analysis was performed to attain the best-fit curves interpolating the measured data, thus providing models of the temperature dependence of the investigated properties. These models can be useful for increasing the accuracy of simulation-based preplanning frameworks of interventional thermal procedures, and the realization of tissue-mimicking materials.
The circulating non-fried roast (CNR) technology was firstly applied to roast mutton. The formation of (non)volatile compounds in the mutton roasted for 0-15 min was investigated. The samples roasted ...at varying times were discriminated using GC-O-MS and multivariate data analysis. A total of 40 volatile compounds were observed, in which 17 compounds were considered as key odorants with odor activity values (OAVs) higher than 1, such as dimethyl trisulfide and 2-ethyl-3,5-dimethylpyrazine. Composition and concentrations of volatile compounds were significantly changed during the process. The key nonvolatile compounds that contributed to flavor were 5'-inosine monophosphate (5'-IMP) and glutamic acid based on taste active values (TAVs) greater than 1. The reduced concentrations of most free amino acids and 5'-nucleotides decreased the equivalent umami concentrations (EUC). The higher thermal conductivity, lower thermal diffusivity and water activity were responsible for the formation of volatile compounds with increased roasting times. The CNR technology was an efficient tool to roast meat products.
•This paper theoretically studies for the first time the Doppler effect for thermal waves, finding an expression of the frequency shift for the two cases of moving source, and moving observer. ...Differences and analogies with the Doppler effect for electromagnetic and acoustic waves are highlighted. Thermal shock waves are also discussed in cases where the source speed is larger than the thermal wave speed. A new methodology, based on lock-in thermography, is also introduced for measuring the thermal diffusivity of samples that are moving at constant velocity, responding to requirement of in-line production in industries.•The figure below shows a comparison of the percentual frequency variation for a moving source for thermal (bluecurve), acoustic (red curve) and electromagnetic waves (black curve), as a function ofthe source velocity γS, normalized to the wave velocity when the observer is at rest. Positive velocity is for reciprocal approach. The shift is positive (blue shift) when the source approaches (γS>0),
This paper theoretically studies the Doppler effect for thermal waves, finding an expression of the frequency shift for the two cases of moving source, and moving observer. Differences and analogies with the Doppler effect for electromagnetic and acoustic waves are highlighted. Thermal shock waves are introduced and simulated numerically. An application for nondestructive evaluation and testing of materials is also discussed.
Thermal-lens spectrometry is a sensitive technique for determination of physicochemical properties and thermophysical parameters of various materials including heterogeneous systems and ...nanoparticles. In this paper, we consider the issues of the correctness (trueness) of measurements of the characteristic time of the thermal-lens effect and, thus, of the thermal diffusivity determined by dual-beam mode-mismatching thermal lensing. As sources of systematic errors, major factors-radiation sources, sample-cell and detector parameters, and general measurement parameters-are considered using several configurations of the thermal-lens setups, and their contributions are quantified or estimated. Furthermore, with aqueous ferroin and Sudan I in ethanol as inert colorants, the effects of the intermolecular distance of the absorbing substance on the correctness of finding the thermophysical parameters are considered. The recommendations for checking the operation of the thermal-lens setup to ensure the maximum accuracy are given. The results obtained help reducing the impact of each investigated factor on the value of systematic error and correctly measure the thermophysical parameters using thermal-lens spectrometry.
This paper presents a new methodology for the thermal diffusivity determination of additively manufactured jet engine blades by using active infrared thermography. The technique is combined with a ...dedicated procedure based on deep machine learning models. The investigated samples were fabricated from different metal alloy powders by using the Laser Engineered Net Shaping (LENS®) technique. The experimental data for model development were in the form of laser shot-induced temperature fields, obtained from an original, in-house developed test apparatus. The advantage of the proposed methodology is that it can be used for the non-destructive measurements of the additively manufactured jet engine blades, which distinguishes the presented approach from the traditional laser-flash technique or other well-established methods. The obtained experimental values of the thermal diffusivity are in good agreement with data measured using the ASTM standard test method. The presented non-destructive technique has significant implementation/commercialization potential when applied to quality control or diagnostic procedures of 3D-printed parts.
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•NDT technique for the thermal diffusivity assessment of the 3D-printed engine blades.•Experimental data obtained for different metal alloys.•High accuracy of the developed predictive model.•Significant implementation/commercialization potential of proposed methodology.
Shear-induced turbulence could play a significant role in mixing momentum and chemical species in stellar radiation zones, as discussed by Zahn. In this paper we analyze the results of direct ...numerical simulations of stratified plane Couette flows, in the limit of rapid thermal diffusion, to measure the turbulent viscosity and the turbulent diffusivity of a passive tracer as a function of the local shear and the local stratification. We find that the stability criterion proposed by Zahn, namely that the product of the gradient Richardson number and the Prandtl number must be smaller than a critical values for instability, adequately accounts for the transition to turbulence in the flow, with . This result recovers and confirms the prior findings of Prat et al. Zahn's model for the turbulent diffusivity and viscosity, namely that the mixing coefficient should be proportional to the ratio of the thermal diffusivity to the gradient Richardson number, does not satisfactorily match our numerical data. It fails (as expected) in the limit of large stratification where the Richardson number exceeds the aforementioned threshold for instability, but it also fails in the limit of low stratification where the turbulent eddy scale becomes limited by the computational domain size. We propose a revised model for turbulent mixing by diffusive stratified shear instabilities that properly accounts for both limits, fits our data satisfactorily, and recovers Zahn's model in the limit of large Reynolds numbers.
•The simple measurement system with precise experimental conditions is required to overcome the diversity of the process dependent heat transport properties of soft materials.•The dual lock-in method ...to measure the self-normalized temperature signal with a practical calibration procedure is proposed to determine the thermal diffusivity and thermal effusivity simultaneously during the phase transitions of liquid crystals.•The quadrupole modeling reveals the optimization of the frequency dependent effect of the contact resistance and capacitance of the sensor in temperature wave method.
The simultaneous measurement of thermal diffusivity and thermal effusivity based on the temperature wave analysis (TWA) is proposed by introducing the dual lock-in temperature sensor with a photo-thermal ac heat source. The thermal effect from each component in the multilayered experimental system is simulated by the quadrupole modeling adopted to the pure periodic heating of the temperature wave. The frequency dependency of the thermal effect from the thermal contact resistance and capacitance in the sensor were analyzed and minimized by taking the optimal frequency range of the temperature wave. The proposed method is applied to examine the nematic-isotropic phase transition of the liquid crystal 4′-(pentyloxy)-4-biphenyl carbonitrile (5OCB). The results were compared with the previous results measured with a single sensor and the advantage of the dual lock-in temperature sensor was demonstrated.
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