Technical Transactions iss. 6. Mechanics iss. 1-M

Technical Transactions iss. 6. Mechanics iss. 1-M

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Collection items (12)


Investigations of liquid flow velocity in a vibromixer using stereo PIV anemometry

Wójtowicz, Ryszard, Paszkowska, Sara
Article
2015
This paper presents the results of investigations of liquid flow in a vibromixer with a single, reciprocating disc. Measurements were conducted using Particle Image Velocimetry (Stereo PIV). Liquid circulation was analysed for two cases: in a whole mixing vessel; in selected zones of intensive flow, e.g. in a gap between the disc and the tank wall. Results of measurements are presented as vector and contour maps of flow velocity distribution. Also, curves illustrating changes of flow for various instantaneous disc positions are shown. Results presented in this work can be used in practice during designing and design optimization of vibromixers applied in the production of multiphase systems and also for the creation of theoretical foundations for the dispersing of phases using mixing equipment of this kind.

Heat transfer of ice slurry flowing in rectangular and slit chanels

Niezgoda-Żelasko, Beata, Żelasko, Jerzy
Article
2015
This paper presents the results of experimental investigations into heat transfer between the wall and ice slurry during its flow through channels of rectangular and slit cross-sections. Ice slurry flow is treated as a generalized flow of a non-Newtonian fluid. The influence of solid particles, the flow character, as well as the cross-section of the channel on the heat transfer coefficient are discussed. As the final result, the dimensionless dependences for the calculation of the Nusselt number value in the range of laminar and turbulent flows are presented.

Free convection on the outer surface of vertical longitudinally finned tubes

Niezgoda-Żelasko, Beata, Żelasko, Jerzy
Article
2015
The paper presents methods of determination and the results of experimental studies of heat transfer coefficients on the outer surface of longitudinally finned tubes under free convection conditions.

Local pressure loss coefficient during the flow of slurry ice trough sudden pipe expansions

Mika, Łukasz, Zalewski, Wojciech
Article
2015
The paper presents the results of experimental studies on ice slurry flow resistance in sudden pipe expansions. In the experimental studies, the mass fraction of solid particles in the slurry ranged from 5 to 30%. The pressure loss coefficients identified as a result of the experimental studies of the turbulent flow of the ice slurry are the same as the coefficients calculated for Newtonian liquids.

Flow modelling of slurry ice in a control valve

Mika, Łukasz, Górski, Bogusław, Kantor, Ryszard
Article
2015
The paper presents the results of simulations of the flow of slurry ice through a control valve. The study focused on a HERZ Strömax-M DN20 control valve. The mass share of ice crystals in the studied slurry ice ranged from 5% to 20%. The results of experimental studies confirmed that the simulations were correct.

Comparative analysis of drag reduction flow efficiency through the use of surfactants and high molecular polymer additives

Matras, Zbigniew, Kopiczak, Bartosz
Article
2015
A comparative analysis of drag reduction efficiency through the use of surfactants and high molecular polymer additives has been performed. Results document that for polymer micellar solutions, the stable transitional zone between the laminar flow and the turbulent flow becomes extended towards higher Reynolds number values. The existence of a third extended drag reduction zone in the turbulent range of flow is also observed. It follows that the analysed polymer-micellar solutions combine and intensify positive features of their purely polymer and micellar analogues providing a more efficient drag reduction effect in wider range of flow.

Friction curves transformation of non-Newtonian fluids in coils

Matras, Zbigniew
Article
2015
The transformation of pseudo-Newtonian dimensionless numbers: Re and fs, describing flow of power-law non-Newtonian fluids in circularly curved tubes, has been done. It has been shown that the multi-parameter friction curves of power-law non-Newtonian fluid can be described, in new dimensionless coordinate system, with the help of single curve in the laminar as well as turbulent flow region. Moreover, the criterion of transition from laminar to turbulent region was clearly determined.

Influence of refrigerant R1234yf as a substitute for R134a on a perfect refrigeration cycle and exchanger efficiency

Kopeć, Piotr
Article
2015
This paper analyses the R1234yf refrigerant as a substitute of R134a with respect to its thermodynamic properties. For the assumed calculation parameters, identical evaporation and condensation temperature, ideal refrigeration cycles with R1234yf and R134a were compared. Moreover, for an actual car evaporator, thermal calculations were performed for the exchanger and the theoretical efficiency parameters of both refrigerants were provided.

Nozzle suppressed pulsating flow CFD simulation issues

Cyklis, Piotr, Młynarczyk, Przemysław
Article
2015
Pressure pulsations in volumetric compressor manifolds are one of the most important problems in compressor operation. These problems occur not only in huge compressor systems such as those used in natural gas piping in gas mines or national transport systems, but also in small refrigeration compressors found in domestic applications. Nowadays, systems require a new approach since in all applications, variable revolution speed compressors are introduced. Mufflers designed in a conventional way on the basis of the Helmholtz theory only have good pressure pulsation damping action within the designed frequency range. In the case of revolution speed change, the reaction of the damper designed according to the Helmholtz theory may be insufficient. Therefore, any innovative ideas for pressure attenuation is welcomed by the compressor industry. One of the possibilities to attenuate pressure pulsations over a wide range of frequencies is the introduction of specially shaped nozzles in the gas duct flow directly after the compressor outlet chamber. It is obvious that the nozzle attenuates pressure and flow pulsations due to energy dissipation, but at the same time, it also raises the requirement for the pumping power of the compressor. The estimation of nozzle pulsation attenuation may be assessed using CFD simulation. In the paper, the influence of the time step and viscous models choices have been shown. The differences between viscous and inviscid gas models have been shown.

The hybrid sorption-compression refrigeration cycle control system

Cyklis, Piotr, Duda, Roman
Article
2015
The requirements for environmentally friendly refrigerants promote the application of both CO2 and water as working fluids. Both solutions have disadvantages resulting from the high temperature limit for CO2 and the low temperature limit for water. This can be avoided by the application of the hybrid adsorption-compression system, where water is the working fluid in the adsorption cycle which is used to cool down the CO2 compression cycle condenser. The adsorption process is powered with a low-temperature renewable heat source such as solar collectors or waste heat sources. This solution has been developed by the authors of this paper and has not been reported in any other literature source. The different ambient conditions over the course of the year require specially designed control procedures and the automation system. The algorithm has to control positive and negative heat sources operation, valve actions, pumps, fans and compressor operation. In the control algorithm, the ambient temperature and solar conditions or other waste heat sources have to be introduced as control parameters, optimised to achieve maximum efficiency of the whole system. The refrigeration effect as a parameter has to be considered both for the refrigeration capacity as well as the CO2 evaporation temperature.