MEASURING THE PRE-HEATING TEMPERATURE OF THE PLATES SURFACE WITH IMPACT GAS IN THE WELDING GAP DURING EXPLOSION WELDING

A technique for measuring the heat flux from the shock-compressed gas in front of the point of contact to the surface of the colliding plates has been developed. The experimental values of the heat flux are obtained, which are in satisfactory agreement with theoretical calculations. For the first time experimentally proved a significant effect of preheating of plates before collision for various materials. The effect consists in heating the surface of the plates, depending on their dimensions and properties, up to 1000 ° C and above.

Penicillins’ Solubility in Supercritical Carbon Dioxide: Modeling by Cubic Equations of States Revisited

Development of processes using green solvents as supercritical fluids (SCFs) depends on the accuracy of modeling and predicting phase equilibrium which is of considerable importance to exploit the use of SCF process at the level of pharmaceutical industries. Solid-Fluid equilibrium modeling is associated to many drawbacks when compressed gas-based models as cubic equations of states (cEoSs) are used. The unavailability of experimental values of solute’s sublimation pressure presents one of the major obstacles to the solubility modeling with this type of models, and thus, its estimation is essential and inevitable. This work is an attempt to address a question regarding “accurate estimated value” of sublimation pressure of two antibiotics Penicillin G (benzyl penicillin) and Penicillin V (phenoxymethyl penicillin). Toward that, first, cEoSs are provided as the thermodynamics modeling framework and fundamental approach. Second, a discussion and a review of some literature results are given. Third, results are invoked to present a criticism analysis that comes from the use of modified form of Peng-Robinson (PR) equation of states. Finally, considerable improvement of modeling results by using a new sublimation pressure is shown.

OPTIMIZATION OF PARAMETERS OF FAN UNITS OF AIR COOLING DEVICES

Purpose of the study. Optimization of the parameters of high speed fan units of air coolers, the combination of which achieves the highest economic efficiency of fan units and, accordingly, the most rational range of specific speed values for the modes of maximum efficiency of fan units in combination with the relative diameter of the sleeve. Development of a mathematical model for determining the local values of the parameters of the efficiency of highspeed fan installations. Sustainable development of territories with active subsoil use is closely related to solving the problems of improving industrial safety and the efficiency of cooling the compressed gas at compressor stations of main gas pipelines, which actualizes the problem of mathematical modeling of energy conversion processes in the impellers of fan units of gas air coolers (AVO) to increase the competitiveness of the oil and gas complex RF in the context of globalization. Research methods. To optimize and determine the limiting combination of calculated parameters, the mathematical method of searching for the area of local maxima of a multiparameter problem in this part was performed in two stages: a mathematical model was built for determining the local values of the parameters that ensure the highest efficiency of fan installations with high speed; the most rational limiting combination of design parameters was determined, at which the highest economic efficiency of fan installations is achieved. Research results. The possibility of increasing the economic efficiency of axial fan units of high speed, made according to aerodynamic schemes with one impeller for gas air cooling devices, has been established. Using the mathematical analysis of the basic laws of axial turbomachines, equations for the efficiency of a fan unit and a fan are obtained, depending on the specific speed. Formulas are obtained for the maximum values of the efficiency of the fan and the fan unit of various specific speed depending on the coefficient of the consumpconsumption speed and on the relative diameter of the impeller sleeve. A method is proposed for constructing aerodynamic schemes of axial fan units for air-cooled gas coolers of the "K" type with maximum maximum values of efficiency for given values of specific speed, relative diameter of the impeller sleeve, aerodynamic quality of the impeller profiles, coefficient of aerodynamic resistance of the flow path of the coefficient of flow velocity. The possibility of creating a fan installation with a speed of ny ≥ 400 with an efficiency of at least ηy=0,86. Application area. Enterprises of the oil and gas complex of the Russian Federation for cooling compressed gas using AVO compressor stations of main gas pipelines.

Liquid Hydrogen: A Review on Liquefaction, Storage, Transportation, and Safety

Decarbonization plays an important role in future energy systems for reducing greenhouse gas emissions and establishing a zero-carbon society. Hydrogen is believed to be a promising secondary energy source (energy carrier) that can be converted, stored, and utilized efficiently, leading to a broad range of possibilities for future applications. Moreover, hydrogen and electricity are mutually converted, creating high energy security and broad economic opportunities toward high energy resilience. Hydrogen can be stored in various forms, including compressed gas, liquid hydrogen, hydrides, adsorbed hydrogen, and reformed fuels. Among these, liquid hydrogen has advantages, including high gravimetric and volumetric hydrogen densities and hydrogen purity. However, liquid hydrogen is garnering increasing attention owing to the demand for long storage periods, long transportation distances, and economic performance. This paper reviews the characteristics of liquid hydrogen, liquefaction technology, storage and transportation methods, and safety standards to handle liquid hydrogen. The main challenges in utilizing liquid hydrogen are its extremely low temperature and ortho- to para-hydrogen conversion. These two characteristics have led to the urgent development of hydrogen liquefaction, storage, and transportation. In addition, safety standards for handling liquid hydrogen must be updated regularly, especially to facilitate massive and large-scale hydrogen liquefaction, storage, and transportation.

Effect of Multi-Walled Carbon Nanotubes-Based Nanofluids on Marine Gas Turbine Intercooler Performance

Coolants play a major role in the performance of heat exchanging systems. In a marine gas turbine engine, an intercooler is used to reduce the compressed gas temperature between the compressor stages. The thermophysical properties of the coolant running within the intercooler directly influence the level of enhancement in the performance of the unit. Therefore, employing working fluids of exceptional thermal properties is beneficial for improving performance in such applications, compared to conventional fluids. This paper investigates the effect of utilizing nanofluids for enhancing the performance of a marine gas turbine intercooler. Multi-walled carbon nanotubes (MWCNTs)-water with nanofluids at 0.01–0.10 vol % concentration were produced using a two-step controlled-temperature approach ranging from 10 °C to 50 °C. Next, the thermophysical properties of the as-prepared suspensions, such as density, thermal conductivity, specific heat capacity, and viscosity, were characterized. The intercooler performance was then determined by employing the measured data of the MWCNTs-based nanofluids thermophysical properties in theoretical formulae. This includes determining the intercooler effectiveness, heat transfer rate, gas outlet temperature, coolant outlet temperature, and pumping power. Finally, a comparison between a copper-based nanofluid from the literature with the as-prepared MWCNTs-based nanofluid was performed to determine the influence of each of these suspensions on the intercooler performance.

A COMPARISON OF THE EFFECTS OF SODIUM BOROHYDRIDE-BASED HYDROGEN STORAGE SYSTEM AND COMPRESSED HYDROGEN STORAGE TANK ON THE FUEL CELL VEHICLE PERFORMANCE

Thanks to its features such as being harmless to the environment, not creating noise pollution, and reducing oil dependence, many countries have started promoting the use of fuel cell vehicles (FCVs) and making plans on enhancing their hydrogen infrastructure. One of the main challenges with the FCVs is the selection of an effective hydrogen storage unit. Compressed gas tanks are mostly used as the hydrogen storage in the FCVs produced to date. However, the high amount of energy spent on the compression process and the manufacturing cost of high-safety composite tanks are the main problems to be overcome. Among different storage alternatives, boron compounds, which can be easily hydrolyzed at ambient temperature and pressure to produce hydrogen, are promising hydrogen storage materials. In this study, a 700-bar compressed gas tank and a sodium borohydride (NaBH4)-based hydrogen storage system are compared for a passenger fuel cell vehicle in terms of the range of the vehicle. The energy storage and production system of the FCV were modeled in MATLAB Simulink® environment coupling the modeling equations of each component after finding the power requirement of the vehicle through vehicle dynamics. Then, the simulations were performed using the speed profile of the New European Drive Cycle (NEDC) and the acceleration requirements. According to the simulation results, the NaBH4-based hydrogen storage system provided a 4.42% more range than the compressed gas tank.

Research on the method of repairing gas lift pipeline from FPSO Ruby - II to Pearl wellhead platform

Some offshore oilfields of Vietnam such as Bach Ho, Rong, Dai Hung, Ruby,… are at this moment in the secondary recovery stage. Gas lift production is one of the suitable methods in this period. Gas lift has proved itself as a more advantageous method in comparisons with other mechanical methods applied at Ruby oilfield. On the Pearl wellhead platform located in Ruby field, a gas lift system is installed to serve for the extraction of petroleum. The system is provided with compressed gas supplied from the FPSO Ruby II through a subsea 6 inches pipeline gas lift. For the sake of effective producing activity, it is a vital task to ensure the safety of this pipeline system during operations. In the case of failures, reparation should be applied immediately to minimize shutdown time and reduce the cost of troubleshooting. This article presents the “smart flange” technique to repair the gas lift pipeline system from the FPSO Ruby - II to the Pearl wellhead platform. Results of the work provide realistic knowledge to propose practical solutions to the maintenance and reparation of this system and thus, improve its operation.

POWER SHELL ELEMENTS: DYNAMIC MATHEMATICAL MODELS, POWER SYSTEMS (OVERVIEW) Continuation

This article is a review devoted to the theory and practice of the application of power shell elements (PSE) in pneumatic drives (PD). She makes acquaint the reader with the main provisions of the theory of PD, performed on the PSE. The review briefly presents materials on the development of dynamic mathematical models (DMM) of power units (PU) of shell PDs (SPD), based on the use of static characteristics of SPD, an assessment of the advantages and disadvantages of PU based on traditional pneumatic cylinders (PC) and PSE is given. The main attention in the review is paid to the solution of the problem of creating PU on PSE with the required quality indicators at the design stage, when it is necessary to take into account the properties of compressed gas. For this, an original methodology for the development of nonlinear DMMs for various typical variants of the midrange is proposed, the basis of which is a number of provisions of the theory of gas dynamics. Without invoking this theory, it is impossible to take into account the properties of compressed gas (compressibility of the working medium, dependence on temperature and gas flow rate in the shell, the nature of the gas expansion processes), and, therefore, to reliably describe the state of unsteady gas processes inside the shell and develop a DMM of the PU, to a sufficient taking into account the mentioned properties. Since the topic of this review is intended mainly for engineers who develop SPD (theoreticians and practitioners), the review also contains materials on the linearization of the found nonlinear DMMs. As a result of linearization, nonlinear DMMs are transformed into transfer functions for displacement of the output coordinate and effort. The correctness of the linearization carried out is confirmed by the results of experiments. The review briefly discusses several options for pneumatic supply systems for SPD. Here, of particular interest for a specialist is the material on imparting invariance properties to SPDs to air intake from the atmosphere and discharge of exhaust air into the atmosphere, which significantly expands the scope of SPDs and reduce their cost.