Improvement of the design method of thermal networks: serial connection of heat exchangers

The mathematical model of the system is considered consisting of a series connection of three heating devices. A system of equations based on the energy conservation law is constructed, which turns out to be incomplete. It is shown that, given the known requirements for the system, expressed only in the efficiency of the system, the formalization of design often becomes insoluble. The system of equations is supplemented with expressions in accordance with the hypothesis of the proportionality of the amount of energy in an element and is presented in matrix form. The design task is reduced to determining the elements of the matrix by the value of the determinants. Analysis of the mathematical model made it possible to obtain an expression for the efficiency of the system as a function of energy exchange in its elements. This made it possible to obtain solutions for flows and their relationships in the elements of the system. In addition, the efficiency of inter-network and intra-network energy exchange has been determined, which satisfy the principles of equilibrium and minimum uncertainty in the values of the average parameters of the system. As an application, one of the main parameters, NTU, is considered, which determines the area of heat exchange with the external environment and the mass and dimensional characteristics of the heat exchange system. Models of direct and opposite switching on of flows with variations of flows and the value of the surface of devices when meeting the requirements for the efficiency of the system are considered. The results of comparing the design process with the iterative calculation method are presented and the advantages of the proposed approach are shown

Axions in Dispersive Media

In the review, based on the analysis of the results published in the works of domestic and foreign researchers, a variant of an unconventional interpretation of the photoluminescence of dispersive media in the energy range of 0.5 - 3 eV is proposed. The interpretation meets the requirements of the energy conservation law for photons and axions participating in the photoluminescence process. The participation of axions in the process is consistent with Primakov's hypothesis. The role of nonradiative relaxation at the stage of axion decay is noted. The axion lifetimes are estimated for a number of dispersive media.

Violation of the Relativistic Energy Conservation Law and Einstein’s Principle of Relativity Caused by the Generation of Mechanical Transverse Waves in a Moving Medium

We study the effect of the generation of the mechanical transverse wave (MTW) travelling in the opposite direction (OD) to a moving medium (MM) on the relativistic energy conservation law (RECL). From the viewpoint of the relativity of simultaneity (RS), the time on the coordinate coinciding with the advance end of the wave (AEW) travelling toward the rear of the MM passes faster than that on the coordinate coinciding with the wave source (WS). Then the AEW in the MM travels forward compared to that in the rest frame of reference (RFR) which is stationary relative to the medium when the time on the coordinate coinciding with the WS is same for each inertial frame of reference (IFR). Hence, the coordinate interval (CI) between the AEW and WS in the MM is observed to be larger than that between them in the RFR. We show that this difference holds true for the CI of any portion having transverse velocities mutually converted by the Lorentz transformation (LT). This difference in the CI leads to that in the rest mass (RM). We demonstrate that the RM included in wave motion (WM) in the MM is larger than one included in WM in the RFR when comparing the portions having transverse velocities mutually converted by the LT. This relation holds true for all portions in WM. Therefore, the total coordinate interval of the portion (CIP) and total RM (TRM) included in WM in the MM (WMMM) are large compared to them included in WM in the RFR. Furthermore, we compare the relativistic kinetic energy (RKE) of the MTW travelling in the OD to the MM (ODMM) with that of the MTW propagating in the direction vertical to the moving direction of the medium. We prove that the CIP and RM included in the former MTW are larger than them included in the latter MTW when comparing each portion with the same transverse velocity (TV). Moreover, the total CIP and TRM included in the former MTW are also large compared to them included in the latter MTW. The reason for these is that the latter CIP and RM are equal to them in the RFR when comparing the portions having transverse velocities mutually converted by the LT. On the other hand, the energy supplied to generate each MTW is the same. From these, we demonstrate that the RKE of the MTW travelling in the ODMM can be larger than the total relativistic energy (TRE) of the MTW propagating in the direction vertical to the moving direction of the medium. Consequently, we propose a violation of the RECL and Einstein’s principle of relativity (EPR) because the TRE is not necessarily conserved in the IFR in which the medium is moving.

Generalized Optical Theorem and Point Sources

A simple derivation of the general form of the optical theorem (GOT) is given for the case of a conservative scatterer in a homogeneous lossless medium, suitable for describing point sources and an observation region close to the scatterer. The presentation is based on the use of the operator approach and scalar wave equation in the limit of vanishingly small absorption. This approach does not require asymptotic estimates of rapidly oscillating integrals, does not use the integration of fluxes, which leads to the loss of information about the energy conservation law, and allows a natural generalization to the case of polarized radiation, as well as more complex multi-part fields. Such GOT generalizes the results known in the mathematical literature for models to the case of any conservative (real) scattering potential and arbitrary sources.

Modeling and analysis of sustained annular pressure and gas accumulation caused by tubing integrity failure in the production process of deep natural gas wells

Sustained annular pressure caused by tubing leakage seriously threatens the safe production of deep gas well. Therefore, it is necessary to fully understand the characteristics of sustained annular pressure and find potential methods to reduce risk. However, most models are about annular pressure caused by thermal expansion and cement integrity failure. Therefore, this paper establishes a model based on the energy conservation law, gas PVT properties and volume consistence law, to study sustained annular pressure caused by tubing leakage. The results indicate that the pressure and gas volume in tubing-casing annulus increase simultaneously and gradually slow down after tubing leakage happens. The decrease of bottom-hole pressure can reduce the risk of annular pressure, which can be realized by downhole choke. Other measures can also control the rising speed of annular pressure, including enhancement of production rate, increase of initial length of gas column and annular liquid with high compressibility, but the the impact of formation energy and annular gas volume should be considered. Sustained annular pressure caused by shallow leaking point has faster rising speed, longer rising period and higher pressure value. Large leaking point leads to remarkable increase of leaking rate and pressure rising speed. The integrity of upper tubing string should be strengthened.

Safe Speed Prediction Model for Heavy Trucks on Consecutive Mountain Downgrade Routes Based on Energy Conservation Law

Safe vehicle speed estimation is essential for road traffic management and traffic safety. Improper truck speed on downgrades may lead to brake fade and/or failure, resulting in severe truck accidents such as runaway or out-of-control. This paper presents a model for predicting the safe speed of trucks from the perspective of preventing brake failure. The proposed model can be used to control the speed limit or as a reference for the revision of highway geometric design standards. In addition, by considering the downgrade design speeds recommended by AASHTO, the study offers an approach to deciding the downgrades that need escape ramps, those that need different speed limits, and those that may need exclusions for trucks over a certain weight. First, we simplify the downgrade driving status of a heavy truck into three types: speed control, emergency braking, and speed recovery according to the speed change status. The prediction model of the brake drum temperature with speed variables has been established in our previous study based on Newton’s energy conservation law. Finally, the boundary conditions for brake fade and failure temperature are determined. Results of parameter analysis show that the gross truck weight is the most significant variable. Other significant variables are grade, grade length, and emergency braking time. Compared with previous research results, the advantage of this method is that the permitted speed can be derived using the brake temperature prediction model supported by theory, without the need for extensive field tests.

Towards a Theory of Electromagnetic Effects Arising in Acoustically Excited Electrolyte Solutions

The present work is an effort to explain theoretically the physics of some processes we have observed in our previous experiments. They occur under any mechanical excitation in solutions of strong electrolytes. We assume that the occurrence of the low-frequency Debye ionic vibration potential (IVP) and the deviation of the RF polarization vector are conjugated, but only in the sense that the power flux density of some physical process "X" responsible for the rotation of the polarization vector is proportional to the square of the electric potential voltage. While the independence of the RF anisotropy appearance from the applied voltage and from the Debye potential in particular has been proved experimentally. An equivalent electrical circuit that simulates the observed effects within the solution excited by an acoustic wave is proposed and tested for physical feasibility. Special attention is paid to the basic theory of the ionic vibrational potential, namely, its predictions in the low-frequency range, which contradict both experiment and the energy conservation law. Given the futility of describing the "memory" effect as a process of electrical or molecular origin, several arguments are presented in favor of the fluid-gyroscopic mechanism. It was suggested that the rotation of the polarization vector of the RF signal is due to a change in the electric moment of the liquid atoms and/or the nuclear moment of ions having an odd mass number. The applications of the research are also supplemented. The results of new experiments show that the RF anisotropy of the solution is transported by the carrier. Accordingly, it is possible to create a completely contactless unitary sensor of velocity and inhomogeneities of the liquid, moreover, the experimental setup has previously confirmed the affordability of the idea.

On Fulfillment of Energy Conservation Law in Theory of Elastic Waves V. V. Nevdakh1)

In accordance with the energy conservation law, the total energy of a closed physical system must remain constant at any moment of time. The energy of a traveling elastic wave consists of the kinetic energy in the oscillating particles of the medium and the potential energy of its elastic deformation. In the existing theory of elastic waves, it is believed that the kinetic and potential energy densities of a traveling wave without losses are the same at any moment of time and vary according to the same law. Accordingly, the total energy density of such wave is different at various moment of time, and only its time-averaged value remains constant. Thus, in the existing theory of elastic waves, the energy conservation law is not fulfilled. The purpose of this work is to give a physically correct description of these waves. A new description of a sound wave in an ideal gas has been proposed and it is based on the use of a wave equation system for perturbing the oscillation velocity of gas particles, which determines their kinetic energy, and for elastic deformation, which determines their potential energy. It has been shown that harmonic solutions describing the oscillations of the gas particles velocity perturbation and their elastic deformation, which are phase shifted by p/2, are considered as physically correct solutions of such equations system for a traveling sound wave. It has been found that the positions of the kinetic and potential energy maxima in the elastic wave, described by such solutions, alternate in space every quarter of the wavelength. It has been established that every quarter of a period in a wave without losses, the kinetic energy is completely converted to potential and vice versa, while at each spatial point of the wave its total energy density is the same at any time, which is consistent with the energy conservation law. The energy flux density of such traveling elastic wave is described by the expression for the Umov vector. It has been concluded that such traveling sound wave without losses in an ideal gas can be considered as a harmonic oscillator.

Superposition of Motions in The Space of Lagrange Variables

The technique of superposition of motions in the space of Lagrange variables is described, which allows us to obtain the equations of combined motion by replacing the Lagrange variables of superimposed (external) motion with Euler variables of nested (internal) motion. The components of velocity and acceleration in the combined motion obtained as a result of differentiating the equations of motion in time coincide with the results of vector addition of the velocities and accelerations of the particles involved in the superimposed motions at each moment of time. Examples of motion and superposition descriptions for absolutely solid and deformable bodies with equations for the main kinematic characteristics of motion, including for robot manipulators with three independent drives, pressing with torsion, bending with tension, and cross– helical rolling, are given. For example, given the fragment of calculation of forces in the kinematic pairs shown the advantages of the description of motion in Lagrangian form for the dynamic analysis of lever mechanisms, allows to determine the required external exposure when performing the energy conservation law at any time in any part of the mechanism.