Thermal High Pressure Research Articles

Sizing and Selection of Pressure Relief Valves for High-Pressure Thermal–Hydraulic Systems

This study covers the critical concerns related to the sizing, selection, installation, maintenance, and testing of pressure safety valves (PSVs). The aim is to ensure the safety of pressurized systems, hydrostatic transmission systems, and hydraulic plants, including process plants, thermal power plants, and nuclear reactor systems. PSVs are devices that ensure the safety and reliability of pressurized vessels, lines, and systems during overpressure events. The task of selecting which PSV features are of greatest value for a specific purpose is complex—especially in the design of a high-pressure experimental thermal–hydraulic facility for hydrostatic and transient testing of the reactor system—when the systems are in the design and development phases and require qualification and demonstration to prove that they have reached a given level of technological readiness. The present study highlights the required steps for users to follow the associated rules, guidelines, and recommendations. As a part of this research, case studies are presented to help readers better understand the applicable strategy and standards. A discussion and a review of PSV performance degradation and failure are summarized to provide a better understanding of varied process applications and conditions, including fluid flow dynamics, boundary-layer formation and pressure drops, gas bubble formation and collapse, geometric configurations, inlet/outlet piping, abrupt pressure fluctuations, and acoustic resonance. Moreover, this study discusses the servicing and testing of PSVs in a multiphase pressurized system. Overall, it provides a basic overview of how PSVs ensure the safety of pressurized systems, supported by case studies and industrial practices.

Inactivation of Bacillus subtilis spores by a combination of high-pressure thermal treatment and potassium sorbate

Combining High-pressure Thermal Treatment (HPTT) and Potassium Sorbate (PS) may have a stronger spore inactivation effect. Spores of Bacillus subtilis were subjected to HPTT at 600 MPa-65 °C/75 °C and a combination of HPTT and PS of 0.1% and 0.2% concentrations. After these treatments, different procedures and techniques were employed to investigate the spore's inactivation. The results revealed that 4.92 ± 0.05 log spores were inactivated after treatment at 600 MPa-75 °C, while 5.97 ± 0.09 log spores were inactivated when the HPTT treatment was combined with 0.2% PS. Changes in permeability of the spore's inner membrane were characterized by OD600 value and release rates of nucleic acids, protein, and dipicolinic acid (DPA). Compared with HPTT treatment at 600 MPa-75 °C, the OD600 value of spores decreased further by about 50% after treatment with a combination of HPTT and 0.2% PS. Additionally, the combined treatments resulted in a significant increase in the OD260 and OD280 values, as well as the DPA release. The spore size analysis indicated a significant decrease in the size of spores treated with a combination of HPTT at 600 MPa-75 °C and PS of 0.2% concentration. Furthermore, the flow cytometry analysis and confocal laser scanning microscopy (CLSM) analysis indicated that the inner membrane damage of spores was higher after combined treatments than that after HPTT treatment alone. A significant reduction was also found in the Na+/K+-ATPase activity after the combined treatments. Also, the FTIR analysis revealed that the combined treatments resulted in significant adverse changes in the spores' inner membrane, cell wall, cortex, and nucleic acid. Therefore, the combination of HPTT and PS has a stronger inactivation effect and can be suggested as a promising strategy for the inactivation of Bacillus subtilis spores.

High Temperature and Pressure Synthesis, Compression Behaviors and Thermal Expansion of Novel Transition Metal Nitrides

High Temperature and Pressure Synthesis, Compression Behaviors and Thermal Expansion of Novel Transition Metal Nitrides

Effects of High Pressure Processing and Thermal Treatment on the Interaction between α-Lactalbumin and Pelargonium-3-Glucoside.

In this study, high pressure processing (HPP) and thermal treatment were comparatively evaluated by examining their impacts on the binding behavior and interaction between α-lactalbumin (α-La) and pelargonium-3-glucoside (P3G) under pH values of 6.0, 7.4, and 8.0. The methods of circular dichroism spectroscopy, fluorescence quenching, dynamic light scattering, and molecular simulation were used to characterize the effects of processing-induced changes in protein structure, size distribution, binding site conformation, and residue charges on their binding characteristics between them. The results indicated that the thermal treatments significantly increased the quenching constants of the complex at pH 7.4/8.0 and 60/80 °C, as well as the accessible fraction of protein at pH 8.0/80 °C. Both HPP and thermal treatments increased the random coil content and showed limited effects on the α-helix and β-sheet contents of α-La and caused the aggregation of the complex to varying degrees. Molecular dynamic simulation and docking analyses revealed that the binding site of the complex did not change under different processing conditions, but the solvent-accessible surface area varied under different conditions.

High Pressure Thermal Sterilization and ε-Polylysine Synergistically Inactivate Bacillus subtilis Spores by Damaging the Inner Membrane

This study was conducted to determine the sterilization effect of a combination of high pressure thermal sterilization (HPTS) and ε-polylysine (ε-PL) on Bacillus subtilis spores. The spores were treated with HPTS (550 MPa at 25, 65, and 75°C) and ε-PL at 0.1 and 0.3%. HPTS and ε-PL synergistically decreased the number of surviving spores and increased the release of the intracellular components in the spore suspension, with the maximal effects from treatment with 550 MPa at 75°C plus 0.3% ε-PL. Maximum fluidity and permeability of the cell inner membrane were observed with 550 MPa at 75°C plus 0.3% ε-PL. Changes in membrane lipids were detected from 3,000 to 2,800 cm-1 by Fourier transform infrared spectroscopy. The results provide new insights into the mechanism by which HPTS and ε-PL synergistically sterilize B. subtilis spores.

Performance Investigation of Graphene Oxide-Based Water/Oil Nanofluids for High Pressure and High Temperature Solar Thermal Technologies for Sustainable Energy Systems

Performance Investigation of Graphene Oxide-Based Water/Oil Nanofluids for High Pressure and High Temperature Solar Thermal Technologies for Sustainable Energy Systems

High Pressure Processing vs. Thermal Pasteurization of Whole Concord Grape Puree: Effect on Nutritional Value, Quality Parameters and Refrigerated Shelf Life.

High-pressure processing (HPP) is utilized for food preservation as it can ensure product safety at low temperatures, meeting consumers’ demand for fresh-like and minimally processed products. The purpose of this study was to determine the effects of HPP (600 MPa, 3 min, 5 °C) and pasteurization by heat treatment (HT, 63 °C, 3 min) on the production of a novel whole Concord grape puree product (with skin and seeds, no waste), and the shelf-life of the puree under refrigerated storage (4 °C). Microbial load, physicochemical properties, phenolic content and antioxidant activity, composition and sensorial attributes of puree samples were evaluated. HPP- and HT-treated purees were microbiologically stable for at least 4 months under refrigeration, with less microbial growth and longer shelf life for HPP samples. HPP and HT samples had similar levels of phenolic contents and antioxidant activities throughout the 4-month refrigerated storage period, even though HPP retained >75% PPO and POD enzyme activities while those of HT were less than 25%. Inclusion of seeds in the puree product significantly increased the fiber, protein, total fatty acid, and linoleic acid contents. Sensory results showed that HPP-treated puree retained more fresh-like grape attributes, had better consistency, and showed significantly higher ratings in consumer overall liking, product ranking, and purchase intent than the HT puree (p < 0.05).

Influence of Temperature and Crystal Orientation on Compressive Strength of Rock Salt Using a Newly Developed High-Pressure Thermal Cell

Influence of Temperature and Crystal Orientation on Compressive Strength of Rock Salt Using a Newly Developed High-Pressure Thermal Cell

High Pressure Thermal Conductivity Measurements of Ternary (Methane + Propane + Heptane) Mixtures with a Transient Hot-Wire Apparatus

High Pressure Thermal Conductivity Measurements of Ternary (Methane + Propane + Heptane) Mixtures with a Transient Hot-Wire Apparatus

Gentle Sterilization of Carrot-Based Purees by High-Pressure Thermal Sterilization and Ohmic Heating and Influence on Food Processing Contaminants and Quality Attributes.

Pressure-enhanced sterilization (PES) and ohmic heating (OH) are two emerging sterilization techniques, currently lacking implementation in the food industry. However, both technologies offer significant benefits in terms of spore inactivation using reduced thermal intensity in food products, as well as minimized effects on sensory and nutritional profiles. In this study, PES and OH were tested based on possible food safety process windows in comparison to thermal retorting, to optimize the food quality of carrot-based purees. The following parameters related to food quality were tested: texture, carotenoid content, color, and detectable amount of food processing contaminants (FPC) formed. Application of the innovative sterilization techniques resulted in a better retention of color, texture, and carotenoids (for PES) as well as a reduced formation of food processing contaminants. Importantly, a significant reduction in the formation of furan and its derivates was observed, compared to the retorted samples. Hence, both sterilization technologies showed promising results in the mitigation of potential toxic processing contaminants and retention of quality attributes.

Nucleation and Growth-Controlled Morphology Evolution of Cu Nanostructures During High-Pressure Thermal Evaporation

The formation of porous material structures has been widely investigated for the development of high-performance energy materials, catalysts, and chemical sensing devices. Various nanoporous structure fabrication methods are based on wet-chemical processes, which require precise control of the process parameters. Physical vapor deposition such as thermal evaporation utilizes high vacuum so that the deposition process is relatively simple, free of contamination, and easily reproduced. However, because of the long mean-free-path of the evaporated atoms in high vacuum, heterogeneous nucleation and the growth of adatoms occurs on the substrate surface, which results in the formation of dense and compact thin films. But by changing the working pressure, various morphologies of porous nanostructures can be obtained. As applied to copper, with increasing pressure the thin film evolves from a dense structure to a coral-like nanoporous structure through a porous columnar structure. All of the porous structures consist of nanoparticle aggregates, where copper nanoparticles are connected to each other, and many nano-gaps are found inside the aggregates. A surface plasmonic effect is expected. The porous copper nanostructured films demonstrated high surfaceenhanced Raman spectroscopy activity.

Immunological components and antioxidant activity in human milk processed by different high pressure-thermal treatments at low initial temperature and flash holding times

The effect of high pressure thermal (HPT) processing on the immunoglobulin (IgM, IgA and IgG), and cytokine content (IL-6, IL-8, IL-10, and TNF-α), and antioxidant activity of human milk was analyzed after the application of different treatments between 200, and 800 MPa at low initial temperatures (between −15, and 50 °C) and for 1 s (flash treatments). Low pressures intensities did not induce changes in Igs while at 800 MPa, all combinations reduced the control levels. IL-6 and IL-10 were not affected by any of the treatments applied while IL-8 and TNF-α were reduced at treatments which combined temperatures at 50 °C. In general antioxidant activity was not affected at the processing conditions chosen. The flash HPT treatment applied at 600 MPa and at 0 °C could be the best choice to preserve immunological parameters and the antioxidant activity of human milk.

Improving the Durability of Stamping Tools from Kh12MF Steel by Quenching in High-Pressure Nitrogen and Thermal Cycling

A possibility of using hardening treatment of the stamping tools in high-pressure nitrogen with thermal cycling was analyzed. A thermal field of Kh12MF steel batches under accelerated heating and cooling conditions during thermal cycling was studied. A satisfactory agreement between the experimental and prescribed temperature conditions in the central and peripheral batch regions has been established. A thermal cycling with subsequent quenching was shown to have a positive effect on the structure, hardness, and impact toughness of steel.

High-Pressure Thermal Conductivity Measurements of a (Methane + Propane) Mixture with a Transient Hot-Wire Apparatus

The transient hot-wire (THW) technique is an absolute technique for measuring the thermal conductivity of fluids. In this work, a THW apparatus was developed for measurements over the temperature range from 193 to 424 K at pressures up to 34 MPa. The apparatus was commissioned with the measurements of pure argon, methane, and propane along several isotherms at pressures up to 33 MPa. The measured values agreed with those calculated with the reference equations within the uncertainty of the equations. Thermal conductivity measurements of a binary mixture (0.9514 methane + 0.0486 propane) were then carried out in the temperature range from 195 to 424 K at pressures up to 31 MPa in a single phase and near the bubble point curve. The relative combined expanded uncertainties (k = 2) for these single-phase and bubble-point mixture measurements were estimated as 2.0 and 5.0%, respectively. The relative deviations of these measured values from those calculated with the extended corresponding state model implement...

Preference-based multi-objectivization applied to decision support for High-Pressure Thermal processes in food treatment

Food industry aims to provide healthy products that must satisfy the quality requirements of the considered legislation. To do so, food is treated by using some processing techniques, such as High-Pressure Thermal (HPT) treatments. In this work, we propose a preference-based multi-objectivization methodology to design HPT processes for food treatment. This approach is based on formulating a multi-objective optimization problem, instead of a constrained mono-objective problem, where the constraints are reformulated as separate objective functions. The multi-objective problem is then solved by using preference-based evolutionary optimization algorithms (PMOEAs). PMOEAs focus the search of a numerical solution inside a region of interest defined by the food engineer, avoiding exploring HPT designs that are out of interest. The proposed methodology is validated by considering several particular mono-objective and multi-objective optimization problems related to HPT processing. In particular, we compare the results obtained by two competitive state-of-the-art PMOEAs, called WASF-GA and R-NSGA-II, with the ones returned by a mono-objective algorithm called MLS-GA. As part of this study, the influence of the optimization algorithm parameters on the solutions, their quality and the computing time are discussed. Finally, the best solutions returned by the algorithm that shows a better performance for our problems, which is WASF-GA, are analyzed from a food engineering point of view and a sensitivity analysis regarding the impact of design parameters on the performances of those solutions is carried out.

Bulk anisotropic multiphase nanohybrid magnets fabricated from compound precursors

Abstract Bulk anisotropic RT7/α-Fe(Co)+Nd2Fe14B/α-Fe (RT7 denotes Sm(CoFeCuZr)7 phase) multiphase nanohybrid magnets have been designed and prepared by High-Pressure Thermal Compression (HPTC), using a blend of Nd9Fe85.5Cu1.5B4 amorphous and SmCo-based amorphous-nanocrytalline powders as precursors. The resulting HPTC magnet is composed of alternating RT7/α-Fe(Co) and Nd2Fe14B/α-Fe nanocomposite layers along the pressure direction. A (00l) crystallographic texture for the RT7 and Nd2Fe14B nanocrystals has been achieved in the RT7/α-Fe(Co) and Nd2Fe14B/α-Fe layers, respectively. The RT7/α-Fe(Co) layer comprises elongated RT7 nanocrystals (8–13 nm in thickness and 13–20 nm in length) and approximately equiaxed α-Fe(Co) nanograins with an average size of ∼13 nm. The Nd2Fe14B/α-Fe layer consists of lath-shaped Nd2Fe14B nanograins (15–30 nm in thickness and 30–55 nm in length) and approximately equiaxed α-Fe nanograins with an average size of ∼19 nm. The HPTC magnet exhibits a maximum energy product of 25 MGOe, with a high soft-magnetic fraction of ∼30 wt%, and a low coercivity temperature coefficient of β(RT-250 °C) = −0.28% oC−1. Our work provides an alternative approach to yielding high-performance bulk multiphase nanohybrid magnets.

Inactivation of non-proteolytic Clostridium botulinum type E in low-acid foods and phosphate buffer by heat and pressure.

The effect of high pressure thermal (HPT) treatments on the inactivation of spores of non-proteolytic type E Clostridium botulinum TMW 2.990 was investigated at high pressures (300 to 600 MPa) and elevated temperatures (80 to 100 °C) in four low-acid foods (steamed sole, green peas with ham, vegetable soup, braised veal) and imidazole phosphate buffer (IPB). In addition, corresponding conventional thermal treatments at ambient pressure were performed to expose possible synergisms of pressure and temperature on spore inactivation. In general, spore count reduction was more efficient by combining pressure and temperatures < 100 °C and the overall process duration could be shortened due to accelerated heating rates (adiabatic effect). Processing at 90 °C and 600 MPa resulted in inactivation below the detection limit after 5 min in all foods except steamed sole. Traditional thermal processing of spores at 90 °C for 10 min, on the other hand, did not result in an estimated 6-log reduction. Additional HPT treatments in steamed sole and IPB did not reveal pronounced food matrix dependent protective effects. Here, varying pressure levels did not appear to be the driving force for spore count reduction in steamed sole at any temperature. By applying a Weibull distribution on destruction kinetics of isobaric/isothermal holding times, 6D-values were calculated. Compression and decompression phase (1 s pressure holding time) had a considerable impact on spore count reduction (max. -2.9 log units) in both, foods and buffer. Hence, compression and decompression phases should directly be included into the total lethal effect of HPT treatments to avoid prolonged holding times and overprocessing.

Non-linear pressure/temperature-dependence of high pressure thermal inactivation of proteolytic Clostridium botulinum type B in foods.

The effect of high pressure thermal (HPT) processing on the inactivation of spores of proteolytic type B Clostridium botulinum TMW 2.357 in four differently composed low-acid foods (green peas with ham, steamed sole, vegetable soup, braised veal) was studied in an industrially feasible pressure range and temperatures between 100 and 120°C. Inactivation curves exhibited rapid inactivation during compression and decompression followed by strong tailing effects. The highest inactivation (approx. 6-log cycle reduction) was obtained in braised veal at 600 MPa and 110°C after 300 s pressure-holding time. In general, inactivation curves exhibited similar negative exponential shapes, but maximum achievable inactivation levels were lower in foods with higher fat contents. At high treatment temperatures, spore inactivation was more effective at lower pressure levels (300 vs. 600 MPa), which indicates a non-linear pressure/temperature-dependence of the HPT spore inactivation efficiency. A comparison of spore inactivation levels achievable using HPT treatments versus a conventional heat sterilization treatment (121.1°C, 3 min) illustrates the potential of combining high pressures and temperatures to replace conventional retorting with the possibility to reduce the process temperature or shorten the processing time. Finally, experiments using varying spore inoculation levels suggested the presence of a resistant fraction comprising approximately 0.01% of a spore population as reason for the pronounced tailing effects in survivor curves. The loss of the high resistance properties upon cultivation indicates that those differences develop during sporulation and are not linked to permanent modifications at the genetic level.

Application of innovative technologies, moderate-intensity pulsed electric fields and high-pressure thermal treatment, to preserve and/or improve the bioactive compounds content of pumpkin

Abstract The application of novel technologies such as moderate-intensity pulsed electric fields (MIPEF) and/or high pressure thermal (HPT) treatments improved the quality of processed pumpkin. MIPEF was applied to whole pumpkin in order to increase the bioactive compounds content, in contrast, HPT treatment was applied in order to preserve the purees. Traditional thermal treatment (TT) of pasteurization and sterilization was compared with equivalent HPT treatments. The effect of processing (TT vs. HPT) in purees made from pumpkin pretreated with MIPEF was evaluated. Microbiological counts, enzyme inactivation (polyphenol oxidase, PPO) and bioactive compounds content (carotenoids, phenolic compounds and antioxidant activity) were analyzed in all processed purees. Regarding the pretreatment of the pumpkin, the application of MIPEF increased the content of some bioactive compounds of interest, such as carotenoids. The HPT treatment equivalent to sterilization preserved high levels of carotene compounds and antioxidant activity of pumpkin puree although this treatment importantly modified the original color of puree. However, the HPT treatment equivalent to pasteurization did not inactivate PPO enzyme in contrast to the effect reached by the equivalent TT. The bioactive compounds levels in HPT treated puree were similar or lower than those treated by TT. Industrial relevance Pulsed electric fields and high pressure thermal processing are emerging non-thermal food processing technologies. Moderate-intensity pulsed electric fields (MIPEF) were applied to increase the generation of bioactive compounds in vegetables. This treatment enhanced the carotenoids content in pumpkin. High pressure thermal treatment (applied at conditions equivalent to sterilization) was the method that best preserved pumpkin purees. The application of MIPEF to pumpkin and HPT treatment to the resulting purees could be proposed as a strategy for producing and preserving vegetable products with high bioactive compounds content.

High-Pressure Thermal Decomposition of Tetrahydrotricyclopentadiene (THTCPD) and Binary High-Density Hydrocarbon Fuels of JP-10/THTCPD in a Tubular Flowing Reactor

High-pressure thermal decomposition of tetrahydrotricyclopentadiene (THTCPD) and binary high-density hydrocarbon fuels of JP-10/THTCPD were investigated at 500–660 °C and 4.0 MPa in an electrically heated tubular reactor. The decomposition of THTCPD under high temperature, high pressure, and low residence time was conducted to analyze their effects on the products. The experimental results of JP-10/THTCPD pyrolysis show that the THTCPD pyrolysis is greatly easier than the thermal cracking of JP-10, and the addition of JP-10 can significantly promote the THTCPD pyrolysis, which is evidenced by the fact that THTCPD conversion increases up to 80% at 660 °C when blended with 50% JP-10. It may be ascribed to possible reason about the pathway and mechanism of JP-10/THTCPD pyrolysis is that the free radicals generated by the decomposition of THTCPD help to promote the decomposition of JP-10 via H-abstraction reactions. Correspondingly, a large number of new free radicals generated from the JP-10 pyrolysis could ...