جستجوی مقالات مرتبط با کلیدواژه « جدایش انرژی » در نشریات گروه « مکانیک »

A vortex tube is a mechanical device for separating a stream of compressed air into two streams of colder and warmer air than the inlet stream at the same time. Simple design, small volume and no need for repair, caused this dual-purpose device to be considered in the industry. In the paper, using simulation and computational fluid dynamics technique, the effect of inlet air pressure on the performance of a vortex tube device has been investigated. To solve the flow field equations, the k-ε turbulence model is used and the model geometry is considered constant. The results show that each vortex pipe has an optimal working pressure that is both economically and economically justifiable. This working pressure was 4.8 bar in the current project. The simulation results show that for cooling purposes, using a mass ratio of 0.3 will cause a higher separation in the cold output and for heating purposes, it is recommended to use a cold mass ratio of about 0.8.

Ranque-Hilsch vortex tube is a simple mechanical device with no moving parts. A high pressure feed gas enters the vortex tube through the swirl nozzles causing the feed gas to split into two thermodynamically different streams. These two streams will be having not only different velocities but also distinguished temperatures that are lower and higher than the inlet feed gas temperature. This phenomenon and the associated energy separation of the feed gas through the vortex tube are strongly dependent on such parameters as geometry, position, and number of the swirl nozzles, diameter and length of the vortex tube, inlet feed gas pressure, control valves, and aperture duct size. Although the vortex tube is used for few decades across different industries, energy separation phenomenon is still neither fully explained nor agreed upon by the scientific community. This paper is an attempt at a better physical understanding of the embedded phenomenon using computational fluid dynamics via a commercial software (Fluent Software) to numerically simulate the transient flow behavior of the feed gas as well as the energy separation, resulting in distinguished gas streams in a two-dimensional and axisymmetric vortex tube. Appropriate boundary conditions are employed in the numerical simulation resembling experimental conditions from the open literature with the exception of the gas exit at the hot end which has been set to be in concert with the operation of the flow-control valve. The obtained numerical results are in good agreement with experimental data from the open literature. Further, the numerical simulation confirms the existence of free and forced vortices and indicates that the temperature of the circumferential elements towards the hot end gets hotter by receiving heat from the core flow due to the kinetic to thermal energy conversion in the presence of viscous shear stresses.

In this paper, the effect of helical nozzles morphology on the vortex tube performance is analyzed using simulations and computational fluid dynamics method. The k-epsilon turbulence model is used to solve the flow field equations, also, the model geometry is considered as a fixed structure. The main goal is to achieve the minimum cold outlet temperature and maximum rotational speed in the vortex tube. In this paper, the machine is equipped with three sets of nozzles including 3 straight nozzles, 6 straight nozzles and 3 helical nozzles. The results indicate a lower cold temperature for a vortex tube with 3 helical nozzles than the other two models. Also, this type of nozzle generates a higher rotational speed inside the vortex tube, especially in the vortex chamber.

Vortex tube or Ranque–Hilsch vortex tube is a mechanical device with a simple geometry and without any intricacy in its components, which can produce two colder and hotter streams from compressible inlet air. In this investigation, computational fluid dynamics (CFD) technique is used to study of key design parameter influence, i.e. inlet pressure on the performance of vortex tubes and energy separation phenomenon. The novelty of the present paper is the special focus on the Mach number inside vortex chamber and its changes due to the inlet pressure effect which has not been investigated in other papers yet. The governing equations have been solved by FLUENT code in 3D compressible and turbulent model using standard k-ε turbulence model. In this study on the basis of obtained results by the CFD study, different inlet pressures of vortex tube are studied. Finally in order to attain the more temperature separation in the vortex tube system, some suggestions and results is presented. This article believes that every vortex tube has an optimum pressure which is commercially optimized in heating and cooling processes. This optimum pressure was found to be 4.8 bar in the present research. The present obtained software results indicate that for cooling purpose, the cold mass fraction of about 0.3 will be recommended for higher cold temperature difference and for heating purposes in throughput of the cold mass ratio of about 0.8 is used. The obtained CFD results are validated by available experimental results. Also the inlet pressure increment reveals the increase of entropy generation and irregularity in the system.

In this article، effect of axial angle of injection nozzles on the flow field structure in a Low-Pressure vortex tube has been investigated by computational fluid dynamics (CFD) techniques. Numerical results of compressible and turbulent flows are derived by using the standard k-ε turbulence model. The dimensions of studied vortex tubes are kept the same for all models and the performance of machine is studied under 6 different axial angles (β) of nozzles. Achieving to a minimum cold exit temperature is the main goal of this numerical research. Our investigation shows that utilizing this kind of nozzle changes the energy separation and flow characteristic. Considering total pressure of cold flow، a new parameter، ξ is defined and results shows that changing the amount of ξ can affect the cold exit temperature directly. Finally، some results of the CFD models are validated by the available experimental data which show reasonable agreement.

In This paper the energy separation phenomenon in a micro-scale vortex tube was investigated by using the computational fluid dynamic. The flow is assumed as steady, turbulent, compressible ideal gas, and the shear-stress transport is used for modeling of turbulence phenomenon. The results show that 3-D CFD simulation is more accurate than 2-D axisymmetric one. Moreover, optimum cold-mass ratios to maximize the refrigeration-power and isentropic-efficiency are evaluated. The results of static temperature, velocity magnitude and pressure distributions show that the temperature-separation in the micro-scale vortex tube is a function of kinetic-energy variation and air-expansion in the radial direction.