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In this work, we prove the local well‐posedness of local strong solutions to an isentropic compressible Ginzburg–Landau–Navier–Stokes system with vacuum in a bounded domain Ω⊂R3.

Present work investigates the performance of a combined solar photovoltaic (PV) and Pumped-Hydro and Compressed-Air energy storage system to overcome the challenges of using solar energy systems. This energy system, which is one of the newest hybrid systems, is able to generate electricity and store energy. To examine the solar PV performance the climatic conditions of Shiraz (in Iran) and Abu Dhabi (in UAE) are considered. The results revealed that, the required pump work, which must be supplied by PV system, is equal to 2.85 and 2.62 MJ/m3 for isothermal and isentropic processes, respectively. Furthermore, the total system efficiency is equal to 76.5%. In addition, the total exergy destruction of hybrid system for isentropic process is 8.91% less than that isothermal process. In addition, instead of the solar PV system, a phosphoric acid fuel cell is coupled to the storage system and the results are compared with the main system.

The energy required for industrial drying processes consumed by a conventional dryers are essentially thrown away without the ability to recover the latent heat of water vapor in the air, significant reductions in dryer energy usage cannot be made. In an attempt to recover the latent heat of the water vapor, a closed drying cycle is proposed, which uses a nozzle as the means to recover this energy from moist-saturated air. This nozzle condensation drying cycle (NCDC) is composed of the following components: dryer, nozzle, diffuser, air water separator, heat exchanger and compressor. Analysis of this drying cycle shows that ideally this cycle requires lower energy compared with an ideal open cycle heated dryer or a heat pump dehumidification cycle. However, which equipment isentropic efficiencies are included, the energy costs are approximately a third of the cost of the ideal open cycle healed dryer. The cycle can be operated at varying conditions, allowing for a single design to be utilized for various ap plications. Other advantages are in applications that require drying of hazardous liquids from a product.

In this paper, inspired by the study of the energy flux in local energy inequality of the 3D incompressible Navier–Stokes equations, we improve almost all the blow-up criteria involving temperature to allow the temperature in its scaling invariant space for the 3D full compressible Navier–Stokes equations. Enlightening regular criteria via pressure $$\Pi =\frac{\text{ divdiv }}{-\Delta }(u_{i}u_{j})$$ of the 3D incompressible Navier–Stokes equations on bounded domain, we generalize Beirao da Veiga’s result in (Chin Ann Math Ser B 16:407–412, 1995) from the incompressible Navier–Stokes equations to the isentropic compressible Navier–Stokes system in the case away from vacuum.

We investigate the sharp time decay rates of the solution \begin{document}$ U $\end{document} for the compressible Navier-Stokes system (1.1) in \begin{document}$ {\mathop{\mathbb R\kern 0pt}\nolimits}^3 $\end{document} to the constant equilibrium \begin{document}$ (\bar\rho>0, 0) $\end{document} when the initial data is a small smooth perturbation of \begin{document}$ (\bar\rho,0) $\end{document} . Let \begin{document}$ \widetilde U $\end{document} be the solution to the corresponding linearized equations with the same initial data. Under a mild non-degenerate condition on initial perturbations, we show that \begin{document}$ \|U-\widetilde U\|_{L^2} $\end{document} decays at least at the rate of \begin{document}$ (1+t)^{-\frac54} $\end{document} , which is faster than the rate \begin{document}$ (1+t)^{-\frac34} $\end{document} for the \begin{document}$ \widetilde U $\end{document} to its equilibrium \begin{document}$ (\bar\rho ,0) $\end{document} . Our method is based on a combination of the linear sharp decay rate obtained from the spectral analysis and the energy estimates.

The organic Rankine cycle is widely used in industrial waste heat, engine waste heat and other waste heat recovery applications, and as a key component of the system, it affects the efficiency and output power of the system. In this paper, a centripetal turbine is designed for the organic Rankine cycle, using vehicle exhaust gas as the heat source. Numerical simulations are performed to analyze the effect of the ratio of the number of guide vane blades to the number of impeller blades (vane number ratio) on the turbine performance and flow field. The results show that the effect of the number of impeller blades on the turbine entropy efficiency, the average exit velocity and the temperature of the guiding grate becomes less and less as the ratio of the number of blades increases. The optimum turbine performance is obtained when the number of impeller blades and the ratio of the number of blades are 17 and 1.5882, respectively, and the expansion performance of the guide impeller is improved and the isentropic efficiency of the turbine is improved by 3.84% compared with the preliminary number of blades.

A new and intuitive method for evaluating the efficiency of the compression process in a supersonic air intake is proposed. The method is based on a comparison of the geometric compression ratio of the flow tube in the air intake under consideration with the maximum possible isentropic compression. It is shown that a higher value of the geometric compression ratio in the air intake allows obtaining higher thrust characteristics, with other conditions being identical.

The isentropic expansion of shock-compressed porous metals (Cu, W, Nb) are experimentally studied, and the experimental results are used to determine their thermodynamic parameters and electrical conductivity. These results allow us to conclude that some porous metals after shock compression and expansion have a two-phase structure. The presence of an additional phase at the isentropic expansion of these metals significantly changes the character of evaporation and the critical point parameters of the liquid–vapor phase transition that are estimated using experiments on the isentropic expansion of shock-compressed porous metals. In addition, the formation of the two-phase structure explains the large difference between the critical point parameters estimated by different methods for a large group of metals (U, W, V, Co, Mo, Ta, etc.).

Ignition within gas burner ejectors can lead to off design conditions and has significant influence on the burner behavior. Thus ignition in the ejector should be prevented. In the present study the influence of combustion reactions on the performance of gas burner injectors is investigated. To investigate if ignition is possible, simulated ignition delay times, using a detailed reaction mechanism, are compared to predicted mean residence times of the gas in the ejector. Gas burner ejectors are designed using one dimensional analytic equations, based on energy and momentum conservation equations and conventional isentropic equations. 1D results are compared to 2D computational fluid dynamics (CFD) simulations, to take into account non-ideal mixing effects along the ejector. Results are validated with experiments with air at room temperature. 1D results show very good agreement not only with CFD simulations for the case of non-reactive flows, but also with performed experiments. It is shown that the assumption of ideal mixing along the ejector and thus the comparison of the ignition delay time to the gas mean residence time, to predict ignition in the ejector, is not valid. Ignition in the ejector is possible, even if the ignition delay time is more than thirty times higher than the mean residence time. In addition to that, it is shown, that ignition and the choice of reaction mechanism have significant influence on the predicted gas burner ejector performance. Thus, the accurate prediction of ignition delay time and the use of a detailed reaction kinetic are mandatory to correctly predict the burner ejector behavior.

The densities and speed of sound for liquid mixtures containing vitamin B3 (niacin) at 0.01, 0.03, and 0.05 mol·kg-1 concentrations in aqueous propylene glycol and hexylene glycol at the variation of temperatures from 293.15 to 308.15 K have been measured using an Anton Paar DSA 5000 M. From volumetric experimental data, apparent molar volume (V ϕ), partial molar volume (V ϕ 0), and partial molar volume of transfer (ΔV ϕ 0) are calculated along with the apparent molar isentropic compression (K ϕ, S ), partial molar isentropic compression (K ϕ, S 0), and partial molar isentropic compression of transfer (ΔK ϕ 0) using experimental acoustic data. The positive volumetric data (i.e., apparent molar volume and partial molar volume) indicates strong solute-solvent interactions inside the mixture. Along with these values, the empirical constants a, b, and c with the pair and triplet coefficients (V AB, V ABB, K AB, K ABB) are also calculated.

In this paper, we consider the Cauchy problem for three-dimensional isentropic compressible radiation hydrodynamic equations with density-dependent viscosity coefficients. When the viscosity coefficients are given as power of density ($\rho^\delta$ with $\delta>1$), we establish the local-in-time existence of classical solutions containing a vacuum for large initial data. Here, we point out that the initial layer compatibility conditions are not necessary.

In this paper, we establish the local existence of weak solutions with higher regularity of the three-dimensional half-space compressible isentropic Navier-Stokes equations with the adiabatic exponent γ > 1 in the presence of vacuum. Here we do not need any smallness of the initial data.

The interlinkage of ethylene glycol, diethylene glycol and triethylene glycol with d-mannitol at different values of temperature has been analysed by the combination of volumetric and acoustic process. Different values of speed of sound and the density of EG, DEG and TEG in the molalities of (0.01, 0.03 and 0.05) mol kg−1 in aqueous solutions of d-mannitol at T = (293.15, 298.15, 303.15 and 308.15) K have been considered. From the values of speed of sound, the partial molar isentropic compression (Kϕ,s) and the partial molar isentropic compression of transfer $$(\Delta {\rm K}_{{\phi ,{\text{s}}}}^{0}$$ ), have been determined. The pair and triplet interaction coefficient have also been estimated. From the density data, the apparent molar volume $$(V_{\phi }^{0}$$ ) and standard partial molar volume of transfer $$(\Delta V_{\phi }^{0} )$$ for EG, DEG and TEG in aqueous d-mannitol solutions have been examined. Using the values of partial molar volume and partial molar isentropic compression of transfer, the pair and triplet coefficients are determined. These noteworthy parameters are helpful to examine the interactions between sugar alcohol + glycols + water solutions.

A three-dimensional initial-boundary value problem for the isentropic equations of the dynamics of a viscous gas is considered. The concentration phenomenon is that, for adiabatic exponent values $$\gamma \leqslant 3{\text{/}}2$$ , the finite energy can be concentrated on arbitrarily small sets. It is proved that, in the critical case γ = 3/2, the norm of the density of kinetic energy in the logarithmic Orlicz space is bounded by a constant that depends only on the initial and boundary data. This eliminates the possibility of the concentration phenomenon.

The global-in-time solutions with discontinuous initial data, when the density has no regularity, are constructed in [10] , [11] , [12] for the isentropic compressible Navier-Stokes equations in multi-dimensional spaces. The time decay rates of these solutions with low regularity still remain unsolved. In this paper we establish the decay rates of solutions in [10] , [11] , [12] in L r -norm with 2 ≤ r ≤ ∞ and the decay rate of the first order derivative of the velocity in L 2 -norm when the initial data are bounded in L 1 . The optimal decay rates are also obtained. These decay rates are the same as rates for classical solutions in [18] , [20] .

The nonlinear stability and local existence of compressible vortex sheets for the two-dimensional isentropic elastic fluid are established in the usual Sobolev spaces. The problem has a characteristic free boundary, and the Kreiss–Lopatinskiĭ condition is satisfied only in a weak form. This paper completes the previous works [6] , [7] of the first three authors where the weakly linear stability of the rectilinear vortex sheets is proved by means of an upper triangularization technique. Our proof is based on certain higher-order energy estimates and an appropriate modification of the Nash–Moser iteration. In particular, the estimate for the normal derivatives of the characteristic variables can be recovered from that for the linearized divergences and vorticities.

We study here the Cauchy problem associated with the isentropic and compressible Euler equations for Chaplygin gases. Based on the new formulation of the compressible Euler equations in J. Luk and J. Speck [The hidden null structure of the compressible Euler equations and a prelude to applications, J. Hyperbolic Differ. Equ. 17 (2020) 1–60] we show that the wave system satisfied by the modified density and the velocity for Chaplygin gases satisfies the weak null condition. We then prove the global existence of smooth solutions to the irrotational and isentropic Chaplygin gases without introducing a potential function, when the initial data are small perturbations to a constant state.

Three-dimensional ideal gas flows behind a detached bow shock wave near the nonsymmetrical nose part of a bluff body in a uniform supersonic flow are investigated. The vector lines of the vector product of the velocity and entropy gradient are considered on isentropic surfaces, which are stream surfaces starting on closed lines located on the shock wave and covering the leading point of the shock wave. It is shown that if these vector lines encircle the isentropic surface they are closed. This means that an orthogonal curvilinear coordinate system in which the coordinate lines coincide with the streamlines may be constructed on each isentropic surface.

A thermomechanical consistent model for cyclotetramethylene tetranitramine (HMX) is developed, which considers material anisotropy, nonlinear thermoelasticity, dislocation-based plasticity, shear cracking induced damage and physical-based phase transformation. The proposed model is employed to investigate the mechanical-thermal-phase transformation response of oriented HMX single crystals under isentropic compression ramp loading at pressures up to ~50GPa for the first time. The proposed model could well reproduce the anisotropic three-wave structure profiles for loading on (0 1 0) and (0 1 1) orientations, including the isentropic elastic limit and stress relaxation after phase transformation. The incorporated inelastic deformation mechanism (plasticity, damage) and phase transformation are responsible for the calculated anisotropic thermomechanical response. Specifically, damage outstands for loads on (0 1 0) orientation while plasticity is more prominent for loads on (0 1 1) orientation. Pressure-temperature-relative volume relation is directly obtained, which agrees well with experimental result from Hooks et al. (2006). Phase transformation response and its effect on thermomechanical behavior are quantified.

Ceteris paribus, the efficiency of heat pumps is higher in the systems with moderate temperature levels for heat consumers. The selection of a scroll compressor for a low-temperature heat pump is defined by its operating characteristics which include isentropic efficiency, feed coefficient and compression ratio. To demonstrate the manufacturer’s specifications for low-temperature scroll compressors, the authors investigated the compressors of three manufacturers: Copeland, Danfoss and Invotech. The study of low-temperature compressors was carried out in the range of refrigerant boiling temperatures from 0 to minus 40°С (in increments of 5°С). The obtained data were used to plot diagrams of respective dependences for various compressor models.

Thermophysical properties of some binary mixtures of novel choline chloride-based deep eutectic solvents and two aromatics (benzene and thiophene) were measured to evaluate the nature of solute–solvent interactions at T = (283.15–303.15) K and atmospheric pressure. Choline chloride was selected as hydrogen bond donor and (mono-, di- and tri-) ethylene glycols or (mono-, di- and tri-) ethanolamines were used as hydrogen bond donors. The density (d), speed of sound (u), viscosity (η) and refractive index (nD) data were measured for binary mixtures of benzene or thiophene with the selected DESs at T = (283.15–303.15) K. The apparent molar volume (Vφ), standard partial molar volume (Vφ0 ), partial molar isentropic compression (κφ0 ), excess molar volume (VE), viscosity B-coefficient and molar refraction (RD) values, were obtained for the binary mixtures at dilute region of aromatics. These quantities are used for interpreting of the studied DESs and benzene or thiophene molecular interactions. Also, the scaled particle theory (SPT) was used for calculation of interaction volume (Vint), and cavity volume (Vcav). The obtained results indicate that DESs with amine functional groups interact more effectively with benzene or thiophene rather than ethylene glycolic-based DESs.

This work reports on the experimentally measured densities, viscosities, speeds of sound, surface tensions, and flash points, and calculated bulk moduli of mixtures of 2,2,4,6,6-pentamethylheptane ...

The present work performs the isentropic analysis and numerical simulation of high-pressure hydrogen jets to study the hydrogen leakage. The exit parameters and the flow characteristics are studied with the ideal gas assumption and real gas effects. The jet exit parameters calculated by the real gas thermodynamic model are different from the results obtained by the ideal gas assumption at high initial pressure based on the isentropic analysis. The ideal gas and the real gas equation of state results in the differences of Mach disk parameters at high initial pressures. The ideal gas assumption underestimates the Mach disk distance by 8% and overestimates the Mach disk diameter by 15% at the initial pressure of 50 MPa. The exit mass flow rates computed from the isentropic expansion assumption agree well with the numerical simulations. The results show that it is reasonable to evaluate mass flow rates of high-pressure hydrogen jets by the isentropic expansion assumption.

A dispersion relation for magnetoacoustic waves in partially ionized heat-releasing plasma in an external magnetic field is derived in a compact form. The increments of slow and fast modified magnetoacoustic waves are calculated in the case of isentropic instability; their strong dependence on the degree of ionization and frequency of ion—neutral collisions is showed.

The compressor is one of the key components in the closed supercritical carbon dioxide (S-CO2) Brayton cycle, but its design method is far from mature. It is naturally expected that the well-established design method of the air compressor can provide favorable guidelines, on the basis of further understanding the effects of the physical property on the compressor flow field. Considering that isentropic compression is one of the core physical processes in the compressor, the physical property effects on this process were mainly investigated in this work. Similarity criterion was considered, and the change rate discrepancy of the main variables in this process between S-CO2 and the ideal air was fully analyzed. Results show that S-CO2 is compressed faster than the ideal air in most cases, along with generating smaller Mach number and larger pressure rise ratio. It is noted the important parameter of the static pressure coefficient distribution with S-CO2 in the compression process is almost the same as that with the ideal air at low Mach number, which is conductive to the extension of the air compressor research experience, but it is quite different at high Mach number. The simulation cases about compressor cascade are further applied and prove the suitability of the revealed physical property effects in the compressor passage. Understanding these effects on the compression process is helpful to improve the design method of the S-CO2 compressor.

In the present paper, it is shown that the large amplitude viscous shock wave is nonlinearly stable for isentropic Navier-Stokes equations, in which the pressure could be general and includes $\gamma$-law, and the viscosity coefficient is a smooth function of density. The strength of shock wave could be arbitrarily large. The proof is given by introducing a new variable, which can formulate the original system into a new one, and the elementary energy method introduced in Matsumura-Nishihara [On the stability of travelling wave solutions of a one-dimensional model system for compressible viscous gas. Japan J. Appl. Math. 2 (1985), no. 1, 17-25.]., Comment: 14pages

Gas engine heat pump (GEHP) is attracting increasing interests owing to the high heating efficiency. However, the refrigerants used in existing GEHPs present high global warming potential (GWP) values, facing the challenge to be phased out. In this work, the heating performances of a water-source GEHP using R134a and low-GWP refrigerant R152a were investigated and compared. The influences of engine speed and evaporator inlet temperature on the refrigerant operating parameters, heating performances, and compressor efficiencies were evaluated. The results indicated that the GEHP using R152a showed higher heating efficiencies, higher compressor efficiencies, lower discharge pressures, and lower natural gas consumption as compared to R134a. As the gas engine speed increases from 1200 rpm to 1600 rpm, the primary energy ratio, isentropic efficiency and volumetric efficiency using R152a have an improvement of 2.6–10.4%, 3.5–10.7% and 5.8–7.3%, respectively, compared to R134a. The comparisons of experimental results indicate that the GEHP can achieve higher heating performance by using low-GWP refrigerant R152a as the drop-in alternative for R134a.

The fluid flows in a variable cross-section duct are nonconservative because of the source term. Recently, the Riemann problem and the interactions of the elementary waves for the compressible isentropic gas in a variable cross-section duct were studied. In this paper, the Riemann problem for Chaplygin gas flow in a duct with discontinuous cross-section is studied. The elementary waves include rarefaction waves, shock waves, delta waves and stationary waves.

The solutions of the Riemann problem for the isentropic relativistic Euler equations with the extended Chaplygin gas are constructed completely for all the possible cases. The asymptotic limits of solutions to the Riemann problem for the relativistic Euler equations are captured in detail when the equation of state of extended Chaplygin gas becomes the one of Chaplygin gas. It is shown that the formations of delta shock wave solution and two-contact-discontinuity solution are derived and analyzed rigorously during the limiting process.

We study the global existence and asymptotic behavior of the solutions for two-fluid compressible isentropic Euler–Maxwell equations by the Fourier transform and energy method. We discuss the case when the pressure for two fluids is not identical, and we also add friction between the two fluids. In addition, we discuss the rates of decay of Lp−Lq norms for a linear system. Moreover, we use the result for Lp−Lq estimates to prove the decay rates for the nonlinear systems.

The atmospheric circulation during the South Asian summer monsoon season is analyzed in moist isentropic coordinates. The horizontal mass transport is sorted in terms of its equivalent potential temperature and is separated into the upper- and lower-tropospheric contributions. This technique makes it possible to trace the transport of air parcels over long distances, identify regions of convective motion in the tropics, and assess the impacts of diabatic processes. The goal here is to assess the thermodynamic characteristics of the atmospheric overturning associated with the South Asian monsoon and to connect this thermodynamic structure to horizontal transport. The monsoon is associated with a low-level inflow of warm and moist air, compensated by an upper-tropospheric outflow at high potential temperature. The South Asian monsoon differs, however, from other monsoonal systems in two important ways. First, the ascending air exhibits an unusually high equivalent potential temperature, which results in global lifting of the tropopause during the boreal summer. Second, on a seasonal basis the main monsoon regions appear to be shielded from dry air intrusion from the extratropical regions.

In this paper, we study the existence of global entropy solutions for the Cauchy problem of the extended river flow system with a friction α(x) depending on the space variable x. First, under the boundedness of , we apply the viscosity-flux approximation method coupled with the maximum principle to obtain the a priori L ∞ estimates for the approximation solutions. Second, we prove the pointwise convergence of the approximation solutions by using the compactness framework from the compensated compactness theory. Finally, as a by-product, we obtain the existence of global solutions for isentropic gas flow in the Laval nozzle with friction.

The initial-boundary value problem for the three-dimensional Euler–Boltzmann equations of a polytropic, ideal and isentropic fluid in radiation hydrodynamics is considered outside a unit ball. It is proved that some $$C^{1}$$ solution will develop singularities in a finite time provided that a weighed functional associated with the initial momentum and the initial intensity of radiation is large.

Ultrasonic velocities and densities of alkyl substituted ammonium perchlorates-RNH3ClO4, where R is methyl (Me), ethyl (Et),n-propyl (Pr),n-butyl (Bu),n-hexyl (Hx) and n-octyl (Oc), have been measured in the concentration range 0.03–0.28 mol·kg−1 in binary mixtures of acetonitrile (AN) and N,N-dimethylacetamide (DMA) containing 0, 20, 40, 60, 80 and 100 mol% DMA at temperatures 298–328 K in 10 K intervals, using an Anton Paar density and sound velocity meter (DSA 5000 M). The experimental data of ultrasonic velocities and densities have been used for calculating isentropic compressibilities ( $$K_{{S}}$$ ) and apparent molal isentropic compressibilities ( $$K_{{{S,}\phi }}$$ ). Limiting apparent molal isentropic compressibilities ( $$K_{{{S,}\phi }}^{{\text{o}}}$$ ) for all the electrolytes have been evaluated from $$K_{{{S,}\phi }}$$ against m1/2 plots and split into contributions of individual ion ( $$K_{{{S,}\phi , \pm }}^{{\text{o}}}$$ ). The variation of $$K_{{{S,}\phi , \pm }}^{{\text{o}}}$$ values with solvent composition shows preferential solvation of alkylammonium ( $${\text{RNH}}_{3}^{ + }$$ ) ions by DMA in the AN rich region and by AN in the DMA rich region. The extent of solvation of the alkylammonium ions, at all studied temperatures, was found to increase with decreasing alkyl chain length; that is $${\text{OcNH}}_{3}^{ + }$$ < $${\text{HxNH}}_{3}^{ + }$$

Herein, we proposed a cascade refrigerant system with R1270 and carbon dioxide refrigerants. The natural refrigerant R1270 was adopted in the high-temperature circuit to replace NH3 and R290. A prototype cascade refrigerant system with two semi-hermetic piston compressors was manufactured, and its performance was investigated experimentally. The results establish R1270 as a good alternative in the high-temperature circuit of the cascade refrigerant system. Moreover, with a constant condensation and evaporation temperature of cascade system, as the R1270 evaporation temperature was decreased (from −7 °C to −19 °C), the coefficient of performance (COP) of the cascade system increased. The isentropic efficiency of R1270 compressor decreased from 78.5% to 74.7% when the R1270 evaporation temperature increased from −19 °C to −7 °C.

Density and speed of sound data for dilute aqueous solutions of two poly(ethylene glycol) monoalkyl ethers, H–(CH2)n–(O–CH2–CH2)m–OH for n = 4, m = 2 and n = 1, m = 3, were measured using the Anton...

Shown the possibility of increasing the effectiveness of the rotary wave cryogenerator by partially changing the operating mode; experimental data were obtained confirming an increase in isentropic efficiency. The achieved efficiency values are in the range of 0.7–0.8 with a degree of expansion of 2.5–1.5. Found a mechanism to improve the efficiency of this device. The results obtained are confirmed by solving the equations of the wave process of energy transfer by the method of Godunov.

This article is a continuation of the preceding article and focuses on the performance evaluation of an oil-free linear compressor prototype. The article introduces performance analysis parameters for a linear compressor along with their analytical attributes. Initially, the kinetic and kinematic analysis at resonance excitation frequency is performed with the help of a specially designed experimental setup. Furthermore, the frequency response functions of output to input parameters is presented to particularly monitor the shift in resonance frequency in the presence of refrigerant. Four different gases are used to quantify the shift and relating them with the physical properties of the refrigerant. Additionally, the pressure-volume curves for all these gases are presented and analysed. In the end, the motor and overall isentropic efficiencies of the prototype are measured at different input parameters. Additionally, the connection between the pressure output and volumetric efficiency is also discussed.

In this paper, we consider the boundary value problem for the one-dimensional non-isentropic Euler-Poisson system. The physical subsonic inflow and outflow conditions are prescribed at boundaries. We prove the existence of multi-transonic solutions, i.e., the existence of subsonic-sonic-supersonic-shock-subsonic flows in fact nozzles. Furthermore, the monotonicity between the location of the transonic shock and the density at the exit of the nozzle will be elucidated.

With increasing need for energy efficient vapor-compression cycles (VCCs), researchers have investigated different aspects of such systems to increase performance. The goal of this research is to experimentally investigate the design and control of a turbomachine expander to recover work and control the VCC. An R-410A split-system heat pump experimental setup has been utilized to compare the performance and control capabilities of a variable nozzle and a fixed nozzle with phase separation combined with evaporator bypass flow metering. A theoretical analysis on the benefit of the expander in heat pumps motivated heat pump operation in cooling mode. The variable nozzle experiments yielded a significant decrease in expander isentropic efficiency, and the evaporator bypass control led to an increase in system coefficient of performance (COP) of 2.3% with an expander overall isentropic efficiency of 18.8%. Compressor suction superheat control was achieved with the evaporator bypass over a range of ambient conditions.

Reflected shock tunnels have been widely used for ground testing of hypersonic airbreathing engines. These facilities are able to replicate the total enthalpy and pressures experienced along hypers...

An isentropic equation of state (Isen-Eos) in a high-density polyethylene (HDPE) consists of four variables of PS, VS, TS and entropy S where the VS, PS and TS are variables satisfying the isentrop...