Beef tallow significantly increases the thermal resistance of E. coli O157:H7, Salmonella spp., and L. monocytogenes. None of these microorganisms could survive such a long heating process at 75 °C ...in regular meat and poultry products.
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•Beef tallow protected E. coli O157:H7, Salmonella spp., and L. monocytogenes during heating.•Survival curves showed two linearly declined patterns.•Survival curves were fitted to the Weibull model using one-step analysis.
The objective of this study was to evaluate the effect of fat on thermal resistance of L. monocytogenes, E. coli O157:H7, and Salmonella spp. A 4-strain cocktail of each microorganism was inoculated to beef tallow and heated isothermally at temperatures between 55 and 80℃. All survival curves did not follow the 1st-order inactivation kinetics but conformed to a two-stage linear pattern. The first stage was markedly less heat-resistant than the second, as manifested by significantly lower D values. The z values of E. coli O157 H7 and Salmonella spp. were 11.8 °C and 12.3 °C in the first stage (z1) but increased to 23.7 °C and 20.8 °C in the second stage (z2), respectively. For L. monocytogenes, while the z values were similar for both stages (z1 = 19.6 °C and z2 = 18.5 °C), the second stage D values are 3.6–5.9 times of those in the first stage. One-step analysis was used to fit the nonlinear curves to the Weibull model, yielding < 1 exponents for the model (0.495, 0.362, and 0.282, respectively, for L. monocytogenes, E. coli O157:H7, and Salmonella spp.), suggesting gradually increased thermal resistance during heating. The experimental results showed that these microorganisms could resist heating for longer time and at higher temperatures in tallow than they do in regular meats containing lower levels of fat. The kinetic models can be used to develop thermal processes to properly inactivate pathogens contaminated in the fat portions of meat products or other high fat products.
Diffusion is generally faster at higher temperatures. Here, a counterintuitive behavior is observed in that the movement of long-chain molecules slows as the temperature increases under confinement. ...This report confirms that this anomalous diffusion is caused by the "thermal resistance effect," in which the diffusion resistance of linear-chain molecules is equivalent to that with branched-chain configurations at high temperature. It then restrains the molecular transportation in the nanoscale channels, as further confirmed by zero length column experiments. This work enriches our understanding of the anomalous diffusion family and provides fundamental insights into the mechanism inside confined systems.
This paper examines the thermal resistances of energy piles and surrounding soils. A field-scale bored energy pile was installed through stiff sandy clay and dense sand and instrumented to measure ...temperatures on the external walls of the heat exchanger pipes, at the pile-soil interface, and in the soil. The radial temperature gradients between the pipes and the pile-soil interface, and the pile-soil interface and the soil, were used to evaluate the pile and soil thermal resistances, respectively. The thermal resistances were on the same order of magnitude with values of 0.053 mK/W, 0.072 mK/W, and 0.066 mK/W for the pile, stiff sandy clay, and dense sand due to similarities in their thermal properties. The analysis suggests that pile and soil thermal resistances are influenced by the pile dimensions, number of pipes, concrete cover, soil type and duration of heating. Hence, meticulous interpretation of thermal resistances considering these parameters should be conducted to understand heat transfer processes in energy piles accurately. Estimates of the pile thermal resistance from the equivalent diameter and thermal response test methods were found to be inconsistent with each other, highlighting the significance of considering steady state in-situ radial temperature gradients in designing energy pile systems.
Aramid nanofiber (ANF) paper has shown potential applications in flexible electronics. However, its inherent low thermal conductivity coefficient (λ) values might threaten the safety of devices under ...a high-power working condition. In this work, polydopamine-functionalized boron nitride nanosheet (BNNS@PDA)/ANF thermally conductive composite papers with nacre-mimetic layered structures were prepared via highly efficient vacuum-assisted filtration followed by hot pressing. For a given BNNS loading, the surface functionalization of BNNS could further enhance the thermal conductivities and mechanical properties of BNNS@PDA/ANF composite papers. BNNS@PDA/ANF composite papers presented anisotropic thermal conductivities, and the through-plane (λ⊥) and in-plane (λ∥) values of the 50 wt % BNNS@PDA/ANF composite papers reached 0.62 and 3.94 W/mK, 181.8 and 196.2% higher than those of original ANF paper, respectively, which were also higher than those of 50 wt % BNNS/ANF composite papers (λ⊥ = 0.52 W/mK and λ∥ = 3.33 W/mK). The tensile strength of the 50 wt % BNNS@PDA/ANF composite papers reached 36.8 MPa, 30.5% higher than that of 50 wt % BNNS/ANF composite papers (28.2 MPa). In addition, the heat resistance index (T HRI) of the 50 wt % BNNS@PDA/ANF composite papers was further increased to 223.1 °C. Overall, our fabricated BNNS@PDA/ANF composite papers possess highly thermal conductivities, excellent mechanical robustness and flexibility, and outstanding thermal stabilities, showing great potential applications in the fields of intelligent wearable equipment, flexible supercapacitors, and flexible electronics.
Thermally conductive polymer composites have become a research hotspot and an important branch in the fields of thermal conduction such as 5G communication equipment, electronic packaging and energy ...transmission due to their light weight, easy processing and low manufacturing cost, etc. However, the thermal conductivity coefficients (λ) of reported thermally conductive polymer composites are far from expected, and one of the most important reasons is the inherent interfaces between phases in the polymer composites and the high interfacial thermal resistance (ITR). This review summarizes the research history and the latest progress of ITR in thermally conductive polymer composites from 4 aspects: mathematical models, computer simulations, measurement techniques and strategies to reduce ITR. Furthermore, the problems of researches on ITR in urgent need for solution as well as corresponding possible solutions are illuminated, hoping to provide some guiding suggestions for the rapid and efficient improvement on λ of thermally conductive polymer composites.
•Mathematical models, computer simulations, measurement techniques of ITR and strategies to reduce ITR are summarized.•The problems and bottlenecks of current researches on ITR in urgent need for solution are illuminated.•Possible solutions for the problems and bottlenecks in the researches on ITR are put forward.
In this paper, self-heating effects (SHEs) in three-stacked nanoplate FETs were investigated through the TCAD simulation. In order to obtain high reliability, the evaluation of SHEs was performed ...after <inline-formula> <tex-math notation="LaTeX">{I}_{D} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">{V}_{G} </tex-math></inline-formula> curve fitting based on the experimental data. First, general analysis on SHEs was conducted to confirm the influence of SHEs to electrical characteristics. The optimized nanoplate width for great electrical properties was proposed by using the figure-of-merit factor under the consideration of SHEs. In addition, difference of heat flux between FinFET and stacked nanoplate FET was analyzed. Based on the analysis, the two-step thermal resistance (<inline-formula> <tex-math notation="LaTeX">{R}_{\text {th}} </tex-math></inline-formula>) model depending on drain voltage was proposed. The two-step <inline-formula> <tex-math notation="LaTeX">{R}_{\text {th}} </tex-math></inline-formula> model in the stacked nanoplate FET matched well with the Berkeley short-channel IGFET model-common multigate model compared the other <inline-formula> <tex-math notation="LaTeX">{R}_{\text {th}} </tex-math></inline-formula> models. A seven-stage ring oscillator with the proposed <inline-formula> <tex-math notation="LaTeX">{R}_{\text {th}} </tex-math></inline-formula> model was demonstrated, and SHEs in the circuit level were confirmed.
•Crystallization fouling of mixed salt in double-pipe heat exchanger is studied.•Na2SO4 is the main fouling substance in mixed salts.•Rf is determined by Na2SO4 content and heat transfer temperature ...difference.•Crystallization fouling of mixed salt is controlled by chemical kinetics.•NaCl decreases fouling thermal resistance and fouling rate.
The fouling behavior of normal solubility pure salt (Na2SO4) and mixed salt (Na2SO4 and NaCl) in counter-current double-pipe heat exchanger was investigated. Through real-time monitoring of inlet and outlet temperatures of hot and cold fluids, the influences of various factors such as the inlet temperature, inlet velocity of hot solution and solute mass ratio on the fouling thermal resistance were determined. The results show that the fouling thermal resistance is determined by the sodium sulfate content at the experimental temperature and the change of the solubility of sodium sulfate within the temperature difference of heat transfer. With the increase of the inlet velocity of hot solution, the thermal resistance of fouling decreases gradually, indicating that the fouling process is controlled by chemical kinetics. In the fouling experiment of mixed salt solution, the main deposition material is sodium sulfate. Due to the common ion effect, sodium chloride greatly affects the saturated solubility of sodium sulfate, with the increase of the mass ratio of sodium chloride, the fouling thermal resistance and the fouling rate decreases gradually, and the time when the fouling thermal resistance reaches the asymptotic value is prolonged. The research results can provide theoretical guidance for scale inhibition of cooling surface of double-pipe heat exchanger in the treatment of wastewater containing sodium sulfate.
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With the current development of modern electronics toward miniaturization, high-degree integration and multifunctionalization, considerable heat is accumulated, which results in the thermal failure ...or even explosion of modern electronics. The thermal conductivity of materials has thus attracted much attention in modern electronics. Although polymer composites with enhanced thermal conductivity are expected to address this issue, achieving higher thermal conductivity (above 10 W m–1 K–1) at filler loadings below 50.0 wt % remains challenging. Here, we report a nanocomposite consisting of boron nitride nanotubes and cellulose nanofibers that exhibits high thermal conductivity (21.39 W m–1 K–1) at 25.0 wt % boron nitride nanotubes. Such high thermal conductivity is attributed to the high intrinsic thermal conductivity of boron nitride nanotubes and cellulose nanofibers, the one-dimensional structure of boron nitride nanotubes, and the reduced interfacial thermal resistance due to the strong interaction between the boron nitride nanotubes and cellulose nanofibers. Using the as-prepared nanocomposite as a flexible printed circuit board, we demonstrate its potential usefulness in electronic device-cooling applications. This thermally conductive nanocomposite has promising applications in thermal interface materials, printed circuit boards or organic substrates in electronics and could supplement conventional polymer-based materials.
•PCM and insulation component are used to improve thermal performance of Trombe wall.•Effects of design parameters of insulation component are studied using the validated model.•Design approach of ...heat preservation at night of a TW-PCM is proposed.•Thermal comfort is analyzed based on operative temperature and radiant temperature asymmetry.
A classical Trombe wall cannot satisfy the thermal comfort for the whole day due to the limited heat storage capacity and large heat loss at night. In present work, phase change materials and an external insulation component are used to improve thermal performance of a Trombe wall. The design approach of heat preservation at night is first obtained. An unsteady heat transfer model of a Trombe wall with phase change materials under heat preservation condition in the nighttime is established by MATLAB. The reliability of the mathematical model is validated by an experiment in Yuzhong (Gansu, China). With this model, the effects of the design parameters of the external insulation component on the thermal performance are analyzed. Finally, the indoor thermal comfort of a passive solar room is analyzed based on the experimental data. The results indicate that, it has a significant impact of the thermal conduction resistance of the insulation component and the thermal resistance of the closed air cavity. For closed air cavity, the internal surface emissivity of the insulation component plays an important role. The optimized additional thermal resistance for the external insulation component is 2 m2⋅°C⋅W−1, and the corresponding maximum thermal resistance of the closed air cavity is determined as about 0.5 m2⋅°C⋅W−1. Compared with no heat preservation at night, the operative temperature improves significantly, and the radiant temperature asymmetries of two massive walls are similar. The investigation can provide a design approach of heat preservation at night for a Trombe wall.
Materials with ultralong phosphorescence have wide-ranging application prospects in biological imaging, light-emitting devices, and anti-counterfeiting. Usually, molecular phosphorescence is ...significantly quenched with increasing temperature, rendering it difficult to achieve high-efficiency and ultralong room temperature phosphorescence. Herein, we spearhead this challenging effort to design thermal-quenching resistant phosphorescent materials based on an effective intermediate energy buffer and energy transfer route. Co-crystallized assembly of zero-dimensional metal halide organic-inorganic hybrids enables ultralong room temperature phosphorescence of (Ph
P)
Cd
Br
that maintains luminescent stability across a wide temperature range from 100 to 320 K (ΔT = 220 °C) with the room temperature phosphorescence quantum yield of 62.79% and lifetime of 37.85 ms, which exceeds those of other state-of-the-art systems. Therefore, this work not only describes a design for thermal-quenching-resistant luminescent materials with high efficiency, but also demonstrates an effective way to obtain intelligent systems with long-lasting room temperature phosphorescence for optical storage and logic compilation applications.
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