Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 7
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

The paper presents equations of a mathematical model to calculate flow parameters in characteristic cross-sections in the steam-water injector. In the model, component parts of the injector (steam nozzle, water nozzle, mixing chamber, condensation wave region, diffuser) are treated as a series of connected control volumes. At first, equations for the steam nozzle and water nozzle are written and solved for known flow parameters at the injector inlet. Next, the flow properties in two-phase flow comprising mixing chamber and condensation wave region are determined from mass, momentum and energy balance equations. Then, water compression in diffuser is taken into account to evaluate the flow parameters at the injector outlet. Irreversible losses due to friction, condensation and shock wave formation are taken into account for the flow in the steam nozzle. In two-phase flow domain, thermal and mechanical nonequilibrium between vapour and liquid is modelled. For diffuser, frictional pressure loss is considered. Comparison of the model predictions with experimental data shows good agreement, with an error not exceeding 15% for discharge (outlet) pressure and 1 K for outlet temperature.

Go to article

Authors and Affiliations

Roman Kwidziński
Download PDF Download RIS Download Bibtex

Abstract

The paper presents an efficiency analysis of two transcritical CO2 power cycles with regenerative heaters. For the proposed cycles, calculations of thermal efficiency are given for selected values of operating parameters. It was assumed that the highest working temperature and pressure are in the range from 600 to 700 °C and 40 to 50 MPa, respectively. The purpose of the calculations was optimization of the pressure and mass flows in the regenerative heaters to achieve maximum cycle efficiency. It follows that for the assumed upper CO2 parameters, efficiency of 51-54% can be reached, which is comparable to the efficiency of a supercritical advanced power cycle considered by Dostal.

Go to article

Authors and Affiliations

Roman Kwidziński
Marian Trela
Dariusz Butrymowicz
Download PDF Download RIS Download Bibtex

Abstract

In the paper, a method for determination of the near-critical region boundary is proposed. The boundary is evaluated with respect to variations of specific heat capacity along isobars. It is assumed that the value of specific heat capacity inside the near-critical region exceeds by more than 50% the practically constant value typical for fluids under normal conditions. It appears that large variations of heat capacity are also present for high-pressure subcritical states sufficiently close to the critical point. Therefore, such defined near-critical region is located not only in supercritical fluid domain but also extends into subcritical fluid. As an example, the boundaries of the near-critical region were evaluated for water, carbon dioxide and R143a.

Go to article

Authors and Affiliations

Roman Kwidziński
Marian Trela
Dariusz Butrymowicz
Download PDF Download RIS Download Bibtex

Abstract

This paper concerns analytical considerations on a complex phenomenon which is diffusive-inertial droplet separation from the twophase vapour-liquid flow which occurs in many devices in the power industry (e.g. heat pumps, steam turbines, organic Rankine cycles, etc.). The new mathematical model is mostly devoted to the analysis of the mechanisms of diffusion and inertia influencing the distance at which a droplet separates from the two-phase flow and falls on a channel wall. The analytical model was validated based on experimental data. The results obtained through the analytical computations stay in a satisfactory agreement with available literature data.
Go to article

Bibliography

[1] Sedler B., Mikielewicz J.: A simplified analytical flow-boiling crisis mode. Trans. Inst. Fluid-Flow Mach. 76(1978), 3–10 (in Polish).
[2] Walley P., Hutchinson P., Hewitt G.F.: The calculation of critical heat flux in forced convection boiling. In: Proc. 5th Int. Heat Transfer Conf., Vol. II, Tokyo 1974.
[3] Kubski P., Mikielewicz J.: Approximated analysis of the drag force of the droplet evaporating within the fluid flow. Trans. Inst. Fluid-Flow Mach. 81(1981), 53–66 (in Polish).
[4] Mikielewicz J.: A simplified analysis of Magnus lift force impact on a small droplets separation from the two-phase flow. Trans. Inst. Fluid-Flow Mach. 75(1978), 63–71 (in Polish).
[5] Ranhiainen P.O., Stachiewicz J.W.: On the deposition of small particles from turbulent streams. J. Heat Transfer. 92(1970), 1, 169–177.
[6] Dolna O., Mikielewicz J.: Separation of droplets in the field of a boundary layer. J. Eng. Phys. Thermophys. 92(2019), 5, 1202–1206.
[7] Pourhashem H., Owen M.P., Castro N.D., Rostami A.A.: Eulerian modeling of aerosol transport and deposition in respiratory tract under thermodynamic equilibrium condition. J. Aerosol Sci. 141(2020), 105501.
[8] Worth Longest P., Xi J.: Computational investigation of particle inertia effects on submicron aerosol deposition in the respiratory tract. J. Aerosol Sci. 38(2007), l, 111–130.
[9] Wang Y., Yu Y., Hu D., Xu D., Yi L., Zhang Y., Zhang S.: Improvement of drainage structure and numerical investigation of droplets trajectories and separation efficiency for supersonic separators. Chem. Eng. Process. – Process Intensific. 151(2020), 107844.
[10] Ganic E.N., Rohsenow W.M.: Dispersed flow heat transfer. Int. J. Heat Mass Tran. 20(1977), 8, 855-866.
[11] Beek W.J., Muttzal K.M.: Transport Phenomena. Wiley 1975.
[12] Hutchinson P., Hewitt G.F., Ducler A.E.: Deposition of liquid or solid dispersions from turbulent gas stream: a stochastic model. Chem. Eng. Sci. 26(1971), 3, 419–439.
[13] Farmer R.A., Griffith P., Rohsenow W.M.: Liquid droplet deposition in twophase flow. J. Heat Transfer 92(1970), 4, 587–594.
[14] Forney L.J., Spielman L.A.: Deposition of coarse aerosols from turbulent flow. J. Aerosol Sci. 5(1974), 3, 257–271.
[15] Friedlander S.K., Johnstone H.F.: Deposition of suspended particles from turbulent gas streams. Ind. Eng. Chem. 49(1957), 7, 1151–1156.
[16] Ilori T.A.: Turbulent deposition of particles inside pipes. PhD thesis, Univ. Minnesota, Minneapolis – Saint Paul 1971.
[17] Sehmel G.A.: Aerosol deposition from turbulent airstreams in vertical conduits. Pacific Northwest Lab. Tech. Rep. BNWL-578, Richland 1968.
[18] McCoy D.D., Hanratty T.J.: Rate of deposition of droplets in annular two-phase flow. Int. J. Multiphas. Flow 3(1977), 4, 319–331.
Go to article

Authors and Affiliations

Jarosław Mikielewicz
1
Oktawia Dolna
1
Roman Kwidziński
1

  1. Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdansk, Poland
Download PDF Download RIS Download Bibtex

Abstract

The paper presents a theoretical analysis of thermal energy storage filled with phase change material (PCM) that is aimed at optimization of an adsorption chiller performance in an air-conditioning system. The equations describing a lumped parameter model were used to analyze internal heat transfer in the cooling installation. Those equations result from the energy balances of the chiller, PCM thermal storage unit and heat load. The influence of the control of the heat transfer fluid flow rate and heat capacity of the system components on the whole system operation was investigated. The model was used to validate the selection of Rubitherm RT62HC as a PCM for thermal storage. It also allowed us to assess the temperature levels that are likely to appear during the operation of the system before it will be constructed.
Go to article

Authors and Affiliations

Jarosław Karwacki
1
Roman Kwidziński
1
Piotr Leputa
1 2

  1. The Szewalski Institute of Fluid Flow Machinery, Polish Academy of Sciences, Heat Transfer Department, Fiszera 14, 80-231 Gdansk, Poland
  2. ENERGA Ciepło Ostrołeka Sp. z o.o., Celna 13, 07-410 Ostrołeka, Poland
Download PDF Download RIS Download Bibtex

Abstract

The paper presents results of experimental investigation of microchannel boiling flow which was controlled by dielectrophoretic (DEP) restrictor. The DEP restrictor was connected to the microchannel liquid supply tube. Operation of DEP restrictor influenced the flow rate at the microchannel inlet. Resulting changes in flow structures and vapour content along the microchannel were observed and analysed with a high-speed video camera. Video recordings were synchronised with measurements of differential pressure between the channel inlet and outlet. It was found that it is possible to change average void fraction in the microchannel by switching on and off the voltage applied to the restrictor electrodes. However, to achieve significant variation of the void fraction, applied voltage should be of the order of 2000 Vpp. The voltage switching also generates oscillations of the differential pressure. The amplitude of these oscillations is proportional to the voltage magnitude, reaching 35 Pa for 2400 Vpp.

Go to article

Authors and Affiliations

Tomasz Przybyliński
Marcin Lackowski
Roman Kwidziński
Jarosław Karwacki
Download PDF Download RIS Download Bibtex

Abstract

The theoretical basis for the indirect measurement approach of mean heat transfer coefficient for the packed bed based on the modified single blow technique was presented and discussed in the paper. The methodology of this measurement approach dedicated to the matrix of the rotating regenerative gas heater was discussed in detail. The testing stand consisted of a dedicated experimental tunnel with auxiliary equipment and a measurement system are presented. Selected experimental results are presented and discussed for selected types of matrices of regenerative air preheaters for the wide range of Reynolds number of gas. The agreement between the theoretically predicted and measured temperature profiles was demonstrated. The exemplary dimensionless relationships between Colburn heat transfer factor, Darcy flow resistance factor and Reynolds number were presented for the investigated matrices of the regenerative gas heater.

Go to article

Authors and Affiliations

Dariusz Butrymowicz
Jarosław Karwacki
Roman Kwidziński
Kamil Śmierciew
Jerzy Gagan
Tomasz Przybyliński
Teodor Skiepko
Marek Łapin

This page uses 'cookies'. Learn more