Fluid Nitrogen Research Articles

Reaction chamber design for an organic molecular layer deposition instrument

Abstract In the molecular layer deposition (MLD) process, the reaction chamber plays a crucial role as the deposition carrier. The geometry of the reaction chamber directly affects the deposition processes of delivery, heating of reactive gases, and purging of excessive molecules. In this study, we designed an MLD instrument for the preparation of pure organic polymer layered coatings and investigated key structural parameters of its reaction chamber. By the Computational Fluid Dynamics (CFD) method, precursor delivery, nitrogen purge, vacuuming, and oil bath heating in the deposition process were modeled. The flow field distribution under different inlet and outlet heights and the temperature field distribution under different axial heights of the chamber were analyzed, and the most suitable parameters were thus determined. The results showed that when the heights of precursor inlet, nitrogen inlet, and vacuum pumping outlet were selected as 50 mm, 45 mm, and 50 mm, respectively, the chamber could serve better deposition and purge efficiency. When the axial height of the chamber is 185 mm, both the chamber and the fluoro rubber sealing ring meet the temperature requirements.

Rumen Fluid Profile, Methane Emission and Nitrogen Excretion of Young and Mature Kacang Goats Under Different Feeding Levels

Rumen Fluid Profile, Methane Emission and Nitrogen Excretion of Young and Mature Kacang Goats Under Different Feeding Levels

Nonmetal-to-metal transition in dense fluid nitrogen at high pressure

Nonmetal-to-metal transition in dense fluid nitrogen at high pressure

Biomass solar fast pyrolysis with a biomimetic mini heliostat field and thermal receiver for nitrogen heating

Biofuels may significantly influence the world's transition from hydrocarbons to renewable energies. Pyrolysis uses thermal energy in an anaerobic ambiance to crack biomass and create biofuels (bio-oil and synthesis gas). This work reports a detailed computational study of a novel system to develop fast biomass pyrolysis with concentrated solar energy. A fluidized bed reactor was coupled to a solar thermal receiver to heat the inert fluid (nitrogen) using a biomimetic mini heliostat field which provides the required thermal energy. A detailed kinetic model for the pyrolysis of lignocellulosic biomass was solved simultaneously with a set of differential equations based on mass, momentum, and energy conservation principles. An Eulerian-Eulerian approach was considered with three phases. The computational model was compared with data reported in the literature for the fluidized bed reactor and heat transfer in the solar thermal receiver with good agreement. Concentrated solar fluxes on the receiver, nitrogen outlet temperatures, temperature contours inside the reactor, concentration contours of relevant gases, and global product percentages (Tar, Char, and Gas) are reported. The products reach an almost constant composition of Gas, Tar, and Char after 6 s of reaction, indicating the annual operational stability of the solar pyrolysis plant in terms of biofuel production.

Techno-Economic Comparison of Brayton Pumped Thermal Electricity Storage (PTES) Systems Based on Solid and Liquid Sensible Heat Storage

To integrate large shares of renewable energy sources in electric grids, large-scale and long-duration (4–8+ h) electric energy storage technologies must be used. A promising storage technology of this kind is pumped thermal electricity storage based on Brayton cycles. The paper’s novel contribution is in the techno-economic comparison of two alternative configurations of such storage technology. Liquid-based and solid-based pumped thermal electricity storage were studied and compared from the techno-economic point of view. The cost impacts of the operating fluid (air, nitrogen, and argon), power rating, and nominal capacity was assessed. Air was the most suitable operating fluid for both technologies, simplifying the plant management and achieving cost reductions between 1% and 7% compared to argon, according to the considered configuration. Despite a more complex layout and expensive thermal storage materials, liquid-based systems resulted in being the cheapest, especially for large applications. This was due to the fact of their lower operating pressures, which reduce the cost of turbomachines and containers for thermal energy storage materials. The liquid-based systems achieved a cost per kWh that was 50% to 75% lower than for the solid-based systems. Instead, the cost per kW benefited the solid-based systems up to nominal power ratings of 50 MW, while, for larger power ratings, the power conversion apparatus of liquid-based systems was again cheaper. This was due to the impact of the turbomachines on the total cost. The machines can represent approximately 70% of the total cost for solid-based systems, while, for liquid-based, approximately 31%. Since the cost of turbomachines scales poorly with the size compared to other components, solid-based systems are less suitable for large applications.

Phase transition and equation of state of dense liquid nitrogen at high temperature and high pressure

Nitrogen is the main reaction and detonation product of energetic materials. Therefore, studying the equation of state and phase transition of nitrogen at high temperature and high pressure is very important in evaluating the energy characteristics of energetic materials, especially in designing a new-generation nitrogen-rich energetic materials. Using density functional molecular dynamics simulation method, we calculate the pressure, internal energy and chemical components of fluid nitrogen in a temperature range of 900–25000 K and a pressure range of 2–300 GPa. The negative changes of pressure with temperature on isochores are observed under the temperature and pressure conditions of 3000–10000 K and 20–80 GPa. As the temperature increases, the pressure drop is caused by the collapse of nitrogen molecules. This phenomenon is related to the phase transition from molecular fluid nitrogen to polymerized fluid nitrogen. The triple bond in the molecule breaks and a polymer forms, which is connected by single and double bonds with neighboring atom. We also study the equation of state along Hugoniot curve under impact loading. The obtained Hugoniot curve is in good agreement with the experimental results. It is found that the softening of the experimental curve in a range of 30–60 GPa is related to the decomposition of nitrogen molecules and the formation of polymeric nitrogen.

Performance Investigation of Cryo-treated End Mill on the Mechanical and in vitro behavior of Hybrid-lubri-coolant-milled Ti-6Al-4V alloy

Global demographic trends have signaled a growing need for biomedical implants such as artificial hips, dental implants, spine screws, coronary stents, and heart pacemakers. The reliability of a manufactured implant can be primarily ensured in terms of its surface integrity, dimensional accuracy, and biocompatibility. In the case of subtractive manufacturing of an implant, the required surface finish and complex geometrical features take the machining to a whole new level. However, the machining of mostly metallic biomaterials such as titanium and its alloys has always been challenged by their poor machinability. In this regard, the latest research has reported the outperformance of cryogenically treated non-coated and coated cutting tools and hybrid cooling environments, which resulted in a noteworthy improvement of machinability and biocompatibility of difficult-to-machine biocompatible materials. Therefore, the present research aimed to enhance the surface integrity and in vitro biocompatibility of Ti-6Al-4V alloy by using AlTiN coated solid carbide end mill in untreated and cryogenically treated condition with wet (using traditional cutting fluid as coolant), cryo (using liquid nitrogen as coolant), and hybrid-lubri-coolant (using a combination of cutting fluid and liquid nitrogen as coolant). The experimental findings were analyzed by RStudio software. The results reported that untreated end mill with cryo-lubri-coolant (C-LC) and cryo-treated end mill with hybrid-lubri-coolant (H-LC) achieved the targeted objectives of this research. However, the cryo-treated end mill with H-LC outperformed the untreated end mill with C-LC and produced better surface characteristics, confirmed by a morphological study of the H-LC-milled surface and cryo-treated end mill. The finding of the in vitro studies confirmed that the H-LC-milled surface exhibited superior biocompatibility and promoted the adhesion, growth, and proliferation of adipose-derived stem cells (ADSCs).

Effects of Boron and NaCl on Antioxidant Defence Mechanisms in Duckweeds (Spirodela polyrhiza L.).

<b>Background and Objective:</b> Boron is one of the principal elements required for plant's growth but extreme amounts of boron are toxic to humans, animals and plants. This study aimed to utilized growth rates, dry biomass and antioxidant enzyme activities to evaluate the potential of <i>Spirodela polyrhiza</i> L., in which <i>S. polyrhiza</i> produced for 120 hrs in water containing control, 10, 20, 40 and 80 mg L<sup>1</sup> of Boron and sodium chloride (NaCl) concentrations changing from 0-50 mM. <b>Materials and Methods:</b> In this study, we have done with <i>S. polyrhiza</i>, Boron and NaCl applications were continued for 120 hrs. After 120 hrs, the plants were harvested, cleaned with pure water, frozen at fluid nitrogen and stored at -80°C until further usage for enzymes activity. To determine the amount of Boron in <i>S. polyrhiza</i>, the samples were dried at 70 and then measured with Thermo ICP-MS. <b>Results:</b> The results indicated that the Boron accumulation capacity of <i>S. polyrhiza</i> diminished with accelerating salinity. <i>Spirodela polyrhiza</i> may have utilized various mechanisms to collecting Boron in high and low salt concentrations. As a conclusion of the study, it was stated that the growth rate of <i>S. polyrhiza</i> and total chlorophyll synthesis were considerably obstructed when NaCl amounts reached 50 mM. <b>Conclusion:</b> Our results indicate that CAT, APX and SOD can serve as substantial biomarkers in Boron-rich habitats. This <i>S. polyrhiza</i> is a very beneficial exemplary plant for phytoremediation advancement of contaminated wastewater with low Boron content.

Structural Markers of the Frenkel Line in the Proximity of Widom Lines.

We have performed a neutron scattering experiment on supercritical fluid nitrogen at 160 K (1.27 TC) over a wide pressure range (7.8 MPa/0.260 g/mL-125 MPa/0.805 g/mL). This has enabled us to study the process by which nitrogen changes from a fluid that exhibits gaslike behavior to one that exhibits rigid liquidlike behavior at a temperature close to, but above, the critical temperature by crossing the Widom lines followed by the Frenkel line on pressure (density) increase. We find that the Frenkel line transition is indicated by a transition to a regime of rigid liquidlike behavior in which the coordination number remains constant within error, in agreement with our previous work at 300 K. The Frenkel line transition takes place at approximately the same density at 160 and 300 K. The data do not conclusively show an additional transition at the location of the known Widom lines. We find that behavior remains gaslike until the Frenkel line is crossed and our data support the hypothesis that Widom line transitions are density increase-driven.

Case Studies in Physiology: Breath-hold diving beyond 100 meters-cardiopulmonary responses in world-champion divers.

In this case study, we evaluate the unique physiological profiles of two world-champion breath-hold divers. At close to current world-record depths, the extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure are profound. As such, these professional athletes must be capable of managing such stress, to maintain performing at the forefront human capacity. In both divers, pulmonary function before and after deep dives to 102 m and 117 m in the open sea was assessed using noninvasive pulmonary gas exchange (indexed via the O2 deficit, which is analogous to the traditional alveolar to arterial oxygen difference), ultrasound B-line scores, airway resistance, and airway reactance. Hydrostatic-induced lung compression was also quantified via spirometry. Both divers successfully performed their dives. Pulmonary gas exchange efficiency was impaired in both divers at 10 min but had mostly restored within a few hours. Mild hemoptysis was transiently evident immediately following the 117-m dive, whereas both divers experienced nitrogen narcosis. Although B-lines were only elevated in one diver postdive, reductions in airway resistance and reactance occurred in both divers, suggesting that the compressive strain on the structural characteristics of the airways can persist for up to 3.5 h. Marked echocardiographic dyssynchrony was evident in one diver after 10 m of descent, which persisted until resolving at ∼77 m during ascent. In summary, despite the enormous hydrostatic and physiological stress to diving beyond 100 m on a single breath, these data provide valuable insight into the extraordinary capacity of those at the pinnacle of apneic performance.NEW & NOTEWORTHY This study shows that world-champion breath-hold divers demonstrate incredible tolerability to extreme levels of hydrostatic-induced lung compression. Immediately following dives to >100 m, there were acute impairments in pulmonary gas exchange efficiency, mild accummulation of extravascular lung fluid, noticable intrathoracic discomfort, and evident nitrogen narcosis, however, within a few hours, these had all mostly resolved.

ROLE OF SUSTAINABLE TECHNIQUES IN MANUFACTURING PROCESS: A REVIEW

Customary mineral based liquids are as a rule broadly utilized in cooling and greases in machining activities. Nonetheless, these cutting liquids are the suitable wellspring of numerous natural and organic issues. To kill the evil impacts related with cutting liquids, it is important to move towards practical machining methods. Such sustainable machining techniques utilize minimize the amount of cutting liquid, fluid nitrogen, vegetable oil or packed air as a cooling-oil medium. The liquids utilized in economical machining strategies are viewed as absolutely biodegradable and Eco-friendly. This paper is a careful survey of the relative multitude of current environmental friendly machining methods as of now rehearsed in the metal cutting cycle. It has been likewise discovered that these economical machining strategies more often than not give better outcomes as far as improved surface nature of the machined part, upgraded apparatus life, less cutting temperatures and slicing powers when contrasted with traditional wet machining techniques. The principle motivation behind this survey work is to recognize the diverse supportable strategies and empower the utilization of such procedures in metal machining, so that, the reducing interaction turns out to be more expense powerful and climate inviting.

Effects of composition and temperature on water sorption in overmature Wufeng-Longmaxi shales

Water sorption provides a great approach to understand water-shale interaction. In this research, water sorption isotherms of fourteen Wufeng-Longmaxi shale samples collected from the eastern Sichuan Basin of China were generated and then interpreted by classical sorption models. The sorption behavior of water and its relationship with pore structure, organic/inorganic composition, and temperature (278–333 K) were explored using organic geochemistry, mineralogy, and gas physical sorption. Brunauer-Emmett-Teller theory functions well for these isotherms but generates ambiguous model parameters, suggesting that multilayer sorption concept is not suitable for water sorption. Dent model distinguishes between primary and secondary sorption, and the resulting specific surface area (ADent(H2O)) is not comparable to the nitrogen-determined specific surface area (ABET(N2)). However, ADent(H2O)/ABET(N2) linearly decreases with increasing ABET(N2), and water saturation is negatively correlated with total pore volume. These observations collectively support the surface-chemistry-controlled clustering mechanism for water sorption. Clay minerals dominate water sorption at low relative pressure because they provide more hydrophilic sorption sites for water cluster formation and growth. Nevertheless, organic matter becomes increasingly important with increasing relative pressure, primarily because a specific-sized organic pore has higher filling pressure than the same-sized clay pore resulting in more pronounced condensation in organic pores at high relative pressure. The water desorption branch shifts to higher relative pressure with increasing temperature and thus, the hysteresis loop shrinks, indicating a mechanism of capillary evaporation similar to wetting fluid nitrogen. The water adsorption branch is insensitive to temperature change, reflecting a temperature-independent clustering mechanism between 278 K and 333 K. The enthalpy of adsorption of collected shale samples is smaller than that of lower-maturity shales but close to that of condensation of bulk water. Based on this finding, we argue that higher-maturity shales have weaker interaction with water, which gives rise to lower temperature sensitivity of water sorption. Therefore, in the future, detailed investigations should revolve around water sorption behavior and its response to temperature in shales with different thermal maturities.

Average Friction Factors of Choked Gas Flow in Microtubes

A micro-tube passage is a basic and important element in the design of micro heat exchangers and for this reason during the last decade a series of investigations have been made with the aim to clarify the main scaling effects playing an important role in microtubes. In this paper, a combined analysis of numerically and experimentally obtained average friction factors in microtubes under the situation of under-expanded (choked) gas flow is presented. The working fluid (nitrogen) passes through the microtube and discharges into the atmosphere under an increasing inlet pressure. Experiments and numerical computations are performed for microtubes with 249 and 528.9 mm in diameter, by varying the aspect ratio (i.e. length/diameter) from 100 to 200. The numerical methodology to solve the governing equations is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. In order to capture the under-expansion characteristics of the flow during choking, the computational domain is extended in the downstream region beyond the microtube outlet. Both experimental and numerical results were obtained for a wide range of Mach number and Reynolds number. In the previous study, it was demonstrated how the outlet Mach number can be expressed as a function of the tube diameter under choked conditions. In this paper, a data reduction procedure for the estimation of the average friction factor between the inlet and the outlet of the microtube is proposed for choked flows in which the outlet gas temperature and pressure are obtained by using the outlet Mach number calculated numerically as a function of the microtube diameter. It is demonstrated how this data reduction method allows an accurate calculation of the average friction factors in microtubes by using a limited number of parameters which are easy to measure. The results obtained in this way are in good agreement with the numerical predictions as well as with the most common empirical correlations.

INVESTIGATION OF LOW-TEMPERATURE FLUORESCENCE AND ABSORPTION SPECTRA OF HIGHLY STABLE MERO-CYANINES DERIVATIVES OF 2, 6-DI-TERT-BUTYL-4-[R]-CYCLOHEXA-2, 5-DIENONE

This work presents the results of the investigation of the dependence of the fluorescence and absorption spectra of merocyanines, derivatives of the 2,6-di-tret-butyl-4-[R]-cyclohexa-2,5-dienone, on the nature of donor end groups (pyridinium, quinolinium, pyrilium, benzo[c,d]indolium, benzoimidindolium). Quantum-chemical calculation of the distribution was organized to electronic density and lengths of the relationships, which has shown that introduction tert-butyl groups in nucleus cyclohexa-2,5-dienone practically does not influence upon the general characteristic merocyanines in contrast with hydrogen. The stability merocyanines vastly increases when entering tert-butyl groups in cyclohexa-2,5-dienone. But such three-dementional groups vastly complicate the bands of the absorption, which become broader, have a complex oscillatory structure. So more suitable spectrums turned out to be for interpreting electronic transition to fluorescences, to measure at the temperature of the fluid nitrogen. As it is seen, spectral bands become more structuring with clearly marked by maximum of the transition. Well-defined 0`→ 0 vibronical transition was found at use of the low-temperature fluorescent spectra. Merocyanines with highly stable tert-butyl groups can be used as fluorescence probes and labels in chemistry and biology, active and passive components for tunable dye lasers, highly effective materials for non-linear optic.

Experimental study on brittle response of shale to cryogenic fluid nitrogen treatment

Cryogenic non-aqueous fracturing has attracted extensive attention due to its thermal shock and freezing effects. In this paper, a novel low temperature mechanics experiment (20 ~ −196 °C) is conducted for shales under cryogenic fluid nitrogen (CF-N2) immersion. Experimental results show that the cooling treatment will enhance the mechanical properties of shale and bring about obvious brittleness failure characteristics. A specific manifestation is that the shale stress-strain curves at low temperatures demonstrate higher peak strength, greater Young's modulus, enhanced yield modulus, faster stress drop and lower residual stress. The relationship between the uniaxial compressive strength and Young's modulus of shale and the freezing temperature is established. A more interesting finding is that elastic strengthening phenomenon instead of yield phenomenon occurs with decreasing freezing temperature. To reveal the change of shale brittleness under CF-N2 cooling, a universal brittleness evaluation model considering the pre- and post-peak deformation characteristics is developed. The evolution of shale brittleness with freezing temperature is obtained. In general, shale brittleness increases with decreasing freezing temperature. The consistency between the brittleness index and the fragmentation fractal dimension at different freezing temperatures verifies the validity of the proposed brittleness evaluation model. Research results indicate that liquid nitrogen, as a new type of cryogenic waterless fracturing fluid, has the potential to improve shale brittleness.

Analysis of supercritical free convection in Newtonian and couple stress fluids through EOS approach

Supercritical natural convection of Newtonian and couple stress fluids about an isothermal cylinder employing the equation of state (EOS) model is addressed in the current numerical investigation. At first, a suitable equation for heat expansion rate based on Redlich–Kwong EOS (RK-EOS), Soave modification EOS (Soave-EOS), Peng-Robinson EOS (PR-EOS) and Virial EOS (Virial-EOS) is obtained under the supercritical region in terms of compressibility parameter, pressure and temperature. The evaluated heat expansion rate values based on these equations of state and local NuX have been validated with practical values and found that the RK-EOS is an appropriate EOS to predict the natural convection characteristics of supercritical fluid (nitrogen) when compared to other models. The governing couple stress liquid circulation equations over a vertical cylinder are computationally solved by employing the finite difference technique. The current numerical study shows that the steady-state and transient velocity fields of a supercritical Newtonian fluid are considerably higher than couple stress fluid and these velocity profiles increase with an increase in reduced pressure and decrease with an increase in reduced temperature. Further, the thermal field is suppressed with magnifying reduced pressure and enhanced with amplifying reduced temperature. Using the present study, it can be concluded that the RK-EOS is considered to be an appropriate EOS to govern the thermal parameters of supercritical Newtonian and couple stress fluids.

Evaluation of RNA degradation in pure culture and field Microcystis samples preserved with various treatments

RNA-based molecular technique (RT-qPCR) is a promising method for microcystin monitoring in lakes and reservoirs, but great lability of RNA in cyanobacterial samples limits its application. To date, no studies have investigated how to effectively preserve RNA in cyanobacterial samples. In this study, four different treatments (−80 °C freezer, −196 °C liquid nitrogen, 4 °C or 25 °C preservation after adding RNA protective fluid) were employed to preserve RNA in pure culture and field Microcystis samples, and RNA degradation in these treatments were systematically evaluated. Results showed liquid nitrogen was the most effective treatment to preserve RNA in pure culture and field Microcystis samples. RNA preservation using RNA protective fluid was temperature dependent. Low temperature (4 °C) could effectively slow down RNA degradation within a short time (1–7 d), since decay rate of mcyH mRNA (k = 0.00094 d−1) was much lower at 4 °C than that at 25 °C (0.0549 d−1) (P < 0.05). However, for field samples, RNA degradation was much faster than pure culture samples with the same treatment. Therefore, to better preserve RNA in field samples, a practical strategy for RNA preservation combining RNA protective fluid and liquid nitrogen, was proposed. Tests of field experiments showed it was more effective than individual treatment for RNA preservation in Microcystis samples during field sampling. Thus, this strategy could be employed to preserve RNA in cyanobacterial samples during field sampling, which will contribute to the application of RT-qPCR technique for microcystin monitoring in lakes and reservoirs.

CFD analysis of the evaporating two-phase flow in the slug flow regime of a cryogenic fluid in a microchannel

Flow boiling in a microchannel is investigated in the present work using the multiphase CFD. Cryogenic fluid nitrogen is used as a working fluid for the CFD simulations. A single bubble is patched in the upstream of the microchannel and the bubble profile, velocity and temperature profile and the heat transfer performance is evaluated. Effect of parameters, like wall heat flux and inlet flow rate or Reynolds number, are studied. It is found that the passage of the bubble significantly alters the parabolic velocity. The passage of the bubble and the evaporation at the interface also significantly reduces the wall temperature due to the enhanced heat transfer. Heat flux does not seem to have any effect on the average heat transfer coefficient, while the heat transfer coefficient increases with the inlet flow rate. The numerical framework employed to perform this study is the open source CFD package OpenFOAM with the volume of fluid interface capturing method.

Prediction of Tool-Chip Interface Temperature in Cryogenic Machining of Ti–6Al–4V: Analytical Modeling and Sensitivity Analysis

Abstract The goal of this work is to predict the tool-chip interface temperature during cryogenic machining and determine the effectiveness of this cooling strategy. Knowledge of the tool-chip interface temperature is needed to conduct process planning: choosing a tool cooling geometry, cutting speed, and cryogen flow rate as well as predicting tool life and achievable material removal rate. A detailed explanation of the analytical heat transfer model is presented, which is a modified form of Loewen and Shaw's orthogonal cutting model, where a thermal resistance network is applied to represent the heat transfer mechanisms in, and out of, the cutting tool. An in-depth discussion of the temperature rise at the tool-chip interface during orthogonal machining of titanium alloy Ti–6Al–4V is presented. The effect of cutting speed, cryogen flow rate and quality, and cooling strategy are explored. The model is used to compare the effect of internal cryogenic cooling with external flood cooling using a water-based metalworking fluid or liquid nitrogen. A sensitivity analysis of the model is conducted and ranks the relative importance of various design parameters. The thermal conductivity of the cutting insert has the greatest influence on the predicted interface temperature. The low boiling temperature and phase change are what make internal cooling of a cutting insert with liquid nitrogen effective at reducing the tool-chip interface temperature. If the heat flowing into the tool, from the tool-chip interface, does not exceed the available latent heat in the cryogen, then this method is more effective than external flood cooling.

Metallization and molecular dissociation of dense fluid nitrogen

Diatomic nitrogen is an archetypal molecular system known for its exceptional stability and complex behavior at high pressures and temperatures, including rich solid polymorphism, formation of energetic states, and an insulator-to-metal transformation coupled to a change in chemical bonding. However, the thermobaric conditions of the fluid molecular–polymer phase boundary and associated metallization have not been experimentally established. Here, by applying dynamic laser heating of compressed nitrogen and using fast optical spectroscopy to study electronic properties, we observe a transformation from insulating (molecular) to conducting dense fluid nitrogen at temperatures that decrease with pressure and establish that metallization, and presumably fluid polymerization, occurs above 125 GPa at 2500 K. Our observations create a better understanding of the interplay between molecular dissociation, melting, and metallization revealing features that are common in simple molecular systems.