Cooling Temperature and Heat Transfer Coefficients in Cylindrical Heat Exchangers

The parameters behavior that characterize the process was carried out through an experimental investigation to obtain the cooling temperature, heat transfer coefficients and the heat flow in mineral coolers. The values of water temperature, water flow and mineral temperature were recorded at the inlet and outlet of the cylindrical cooler. Experiments were carried out with five values of the mass flow, keeping the cylinder revolutions constant. The calculation procedure for the system was obtained, in the mineral coolers the heat transfer by conduction, convection and evaporation predominates as a function of the cooling zone. A reduction in temperature is shown with increasing length, the lowest temperature values were obtained for a mass flow of 8 kg/s. The mineral outlet temperature should not exceed 200 oC, therefore it is recommended to work with the mass flow less than 10 kg/s that guarantees the cooling process.

Spectral Analysis of Translation-Invariant Mechanical Systems with Application to Structural Vibrations and Stability

The paper considers the problems and the methods of spectral analysis of elastic structural systems. The presented consideration focuses on the translation-invariant spectral formulations. Some periodic representations and the spectral decomposition are derived. In the context of general analysis of translation-invariant systems, the particular problems of structural vibration and stability are solved in analytical form.

Application of Two-dimensional Finite Volume Method to Protoplanetary Disks

Many fascinating astrophysical phenomena can be simulated insufficiently by standard numerical schemes for the compressible hydrodynamics equations. In the present work, a high performant 2D hydrodynamical code has been developed. The model is designed for the planetary formation that consists of momentum, continuity and energy equations. Since the two-phase model seems to be hardly executed, we will show in a simplified form, the implementation of this model in one-phase. It is applied to the Solar System that such stars can form planets. The finite volume method (FVM) is used in this model. We aim to develop a first-order well-balanced scheme for the Euler equations in the the radial direction, combined with second-order centered ux following the radial direction. This conception is devoted to balance the uxes, and guarantee hydrostatic equilibrium preserving. Then the model is used on simplified examples in order to show its ca- pability to maintain steady-state solutions with a good precision. Additionally, we demonstrate the performance of the numerical code through simulations. In particularly, the time evolution of gas orbited around the star, and some proper- ties of the Rossby wave instability are analyzed. The resulting scheme shows consequently that this model is robust and simple enough to be easily implemented.

A Review on the Application of Multiphase Twin Screw Pump as a Downhole Wet Gas Compressor to Improve Gas Wells Recovery Factor

By introducing a multiphase twin screw pump as an artificial lifting device inside the well tubing (downhole) for wet gas compression application; i.e. gas volume fraction (GVF) higher than 95%, the unproductive or commercially unattractive gas wells can be revived and made commercially productive once again. Above strategy provides energy industry with an invaluable option to significantly reduce greenhouse gas emissions by reviving gas production from already existing infrastructure thereby reducing new exploratory and development efforts. At the same time above strategy enables energy industry to meet society’s demand for affordable energy throughout the critical energy transition from predominantly fossil fuels based resources to hybrid energy system of renewables and gas. This paper summarizes the research activities related to the applications involving multiphase twin screw pump for gas volume fraction (GVF) higher than 95% and outlines the opportunity that this new frontier of multiphase fluid research provides. By developing an understanding and quantifying the factors that influence volumetric efficiency of the multiphase twin screw pump, the novel concept of productivity improvement by a downhole wet gas compression using above technology can be made practicable and commercially more attractive than other production improvement strategies available today. Review and evaluation of the results of mathematical and experimental models for multiphase twin screw pump for applications with GVF of more than 95% has provided valuable insights in to multiphase physics in the gap leakage domains of pump and this increases confidence that novel theoretical concept of downhole wet gas compression using multiphase twin screw pump that is described in this paper, is practically achievable through further research and improvements.

Closed Loop Performance Analysis of Classical PID and Robust H-infinity Controller for VTOL Unmanned Quad Tiltrotor Aerial Vehicle

Unmanned Aerial Vehicles (UAVs) guidance, control and navigation have directed the attention of many researchers in both aerospace engineering as well as control theory. Due to the unique rotor structure of Tiltrotor hybrid UAVs, they exhibit special application value. Quad Tiltrotor UAVs set up a distinctive platform that satisfies the needs of the varying mission requirements by combining the conventional features of high-speed cruise capabilities of an aircraft and hovering capabilities of a helicopter and by tilting its four rotors. The aim of this research article is to control the attitude and altitude of the UAV in the presence of uncertainty using two different control techniques. This paper addresses the comparative analysis of the robust H-infinity controller with classical PID control designs for the transition manoeuvre of a hybrid UAV: the VTOL Tiltrotor UAV. The proposed controllers achieve hover to cruise mode transition and vice-versa. The main idea behind the design of controller is to model and analyze the UAV’s position and attitude dynamics. The desired flight trajectory and the transition manoeuvre is achieved by controlling the tilt angle in 15° intervals from 90° to 0° and vice-versa. Performance index subjected to IAE is estimated and compared for both the controllers in the presence of noise, disturbances and uncertainties. The results of simulation illustrate that the robust H-infinity controller achieves better transition, good adaptability, robust performance and robust stability for the whole flight envelope when compared with the PID controller.

Investigation of Physical Properties of Fe(III) Containing Metal-Organic Polymers

n this work, we studied the properties of a specially synthesized organometallic coordination polymer - a porous coordination polymer with biocompatible structural elements based on oxoclusters of iron muconate (III). The samples were investigated by scanning electron microscopy, thermogravimetric analysis combined with differential scanning calorimetry, and the study of low-temperature nitrogen adsorption of a sample obtained by a modified solvothermal technique. It is shown that most of the pores of the sample have an average radius of 18,8 Å ~ 1,88 nm. Also, as a result of the study, it is necessary to conclude that the synthesized material has a developed surface area - it is 512,1 m2/g and the pore volume is ~ 0,48 cm3/g. It should be concluded that such materials are promising as components for a new generation of various kinds of functional materials with improved or unique characteristics. It is obvious that further research in this area is important from both fundamental and applied points of view.

Tribological Properties of Polymer Composite with Impregnated Quasicrystal Nanoparticles

In this work, a study is carried out on the introduction of quasicrystal particles into a thermoplastic polymer and it is shown that this leads to changes in the structure of polyethylene. The introduction of quasicrystal particles into a thermoplastic polymer leads to changes in the structure of polyethylene: the degree of crystallinity decreases from 42% (PE) to 27% (10AlCuFe/PE) with increasing concentration of the filler, the ratio of bands corresponding to amorphous and crystalline regions in the IR spectra changes, which indicates on the amorphization of the PE structure. The specimens have improved wear resistance (the wear rate decreased by 96% compared to the original PE), but the friction coefficient remained practically unchanged. It is shown that the addition of quasicrystal nanoparticles in a small amount (up to 10 wt.%) leads to an increase in hardness, but does not have a noticeable effect on the surface roughness. The results obtained indicate that quasicrystals can serve as effective fillers for promising polymeric materials in products for aerospace, instrument making, and other industries.

Numerical and Analytical Modeling of Permanent Deformations in Panels Made of Nanomodified Carbon Fiber Reinforced Plastic with Asymmetric Packing

In this paper, a mathematical model of a multilayer panel made of nanomodified carbon fiber reinforced plastic with asymmetric packing is proposed. The introduction of nanosized particles into the composition of the composite or its components (fiber or binder) allows not only to increase its physical and mechanical properties, but also to improve the picture of the residual stress-strain state. The paper investigates the effect of nanomodification of carbon fiber reinforced plastic on the residual stress-strain state after molding using numerical and analytical methods. Numerous results of computational experiments have been obtained. The results of numerical and analytical modeling are compared with experimental data. Conclusions are drawn about the possibility of reducing the residual stress-strain state in structures with asymmetric reinforcement schemes when using a matrix containing carbon nanoparticles. A mathematical model of a multilayer panel made of nano-modified carbon fiber with asymmetric packing has been built. Investigation of the residual stress-strain state of structural elements made of carbon fiber reinforced plastic made it possible to reveal the possibility of reducing the residual stress-strain state and leash in structures with asymmetric reinforcement schemes when using a matrix containing carbon nanoparticles.

Mathematical Modeling of Heat and Mass Transfer in Heat Pipes in a One-Dimensional Formulation when Cooling Active Phased Antenna Arrays

The work proposes test one-dimensional models of heat and mass transfer in heat pipes during cooling of active phased antenna arrays, which can be used in processing the test results of flat heat pipes in order to determine their performance characteristics and identify the parameters required for modeling in a more complex setting (for example, in flat and taking into account the presence of several localized sources of heat supply). To take into account the influence of the heat release power on the equilibrium temperature inside the heat pipe, the model has been added to take into account the dependence of the steam saturation temperature on the pressure, which is realized inside the steam pipeline when the heat pipe is heated. Numerous calculations carried out made it possible to refine the mathematical model. In particular, a significant effect on the temperature distribution along the heat pipe is shown, taking into account the dependence of the steam saturation temperature on the pressure in the parawire. It is shown that the introduction of standard functions for the characteristics of the coolant (water) in the liquid and vapor state, as well as taking into account the capillary pressure on temperature, makes it possible to refine the resulting solution.

Investigation of Mechanical Properties of Low-Density Polyethylene with Copper Nanoparticles

In this work, it is shown that the method of the in situ preparation of Cu/LLDPE by combining the formation of a composite and a nanodispersed phase in the viscous-flow state of a polymer makes it possible to achieve a uniform distribution of nanoparticles in the matrix and effectively regulate their mechanical and functional properties. The optimal concentration of Cu nanofiller was found to be 2-5%, allowing to achieve the best mechanical properties. Comparative analysis of the physical and mechanical properties of Cu/LLDPE nanocomposites obtained by various methods shows that the deformation and strength characteristics of the 3CuLLDPE nanocomposite obtained by the in situ method are improved in comparison with the properties of the 3CuLLDPE nanocomposite, prepared by ex situ method. The relationship between the filler content and the modulus of elasticity/tensile strength has been determined. With an increase in the filler content, the elastic modulus increases by 10-20%, and the tensile strength decreases by 30%. Elongation at break for samples with nanofiller content up to 3 wt. % higher than unfilled polymer