Wyniki wyszukiwania - BazTech

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Zagadnienia wartości prędkości dźwięku w przepływach dwufazowych czynników chłodniczych

Butrymowicz D., Miąskowska D.

Technika Chłodnicza i Klimatyzacyjna

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2006

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nr 6-7

230-234

PL

W artykule podjęto temat oceny wartości prędkości dźwięku w przepływach dwufazowych czynników chłodniczych. Omówiono sposób wyznaczenia tej prędkości w jednorodnych przepływach dwufazowych, które można traktować jako jednowymiarowe. Przeprowadzono obliczenia prędkości dźwięku dla wybranych płynów stosowanych obecnie w technice chłodniczej takich jak: R 134a, R 22, R 290 (propan), R 404A, R 407C, R 507, R 600a (izobutan), R 717 (amoniak) i R 744 (dwutlenek węgla). W ocenie autorów, w oparciu o uzyskane wyniki obliczeń można sugerować, że prędkość dźwięku tych czynników jest na tyle mała, iż należy ją brać pod uwagę przy analizie procesów wymiany ciepła podczas wrzenia oraz wymiany pędu w strumienicach cieczowo-parowych, stosowanych w urządzeniach chłodniczych.

EN

The problem of estimation of sound velocity in two-phase flows of refrigerants has been examined in the paper. The sound velocity calculation procedure has been discussed for the case of one-dimensional and homogenous two-phase flows. The sound velocity has been calculated for various refrigerants used in the modern refrigeration engineering: R 134a, R 22, R 290 (propane), R 404A, R 407C, R 507, R 600a (isobutane), R 717 (ammonia), and R 744 (carbon dioxide). On the basis of the results the authors suggested that the sound velocity may be so small that it should be considered in the analysis of boiling process as well as momentum transfer in two-phase ejectors used in refrigeration systems.

2

Modelling of temperature measuring cups in application to heat exchangers

Butrymowicz D., Miąskowska D., Karwacki J., Trela M.

Turbulence : international journal

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2005

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Vol. 11

251-258

EN

The paper deals with the problem of the appropriate geometry of the mixing cup for accurate temperature measurement at the inlet and outlet of heat exchangers. These cups ensure the uniform temperature distribution at the measuring cup outlet chamber which enables to accurately measure average temperature. This problem was solved by means of numerical modelling of three geometries of the mixing cups for various thermal and flow conditions. The geometries of the mixing cups, finite volume mesh, initial and boundary conditions were presented. On the basis of the numerical results it is possible to conclude that the outlet chamber geometry play less important role in comparison with mixing chamber geometry in all investigated cases of measuring cups.

3

Experimental investigation of performance of two-phase ejector operating with volatile fluids

Butrymowicz D., Karwacki J., Miąskowska D., Trela M.

Turbulence : international journal

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2005

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Vol. 11

225-233

EN

Two-phase liquid-vapour ejectors may be applied in refrigeration systems in order to reduce the throttling loss. However, there is a clear need for fundamental investigations of such ejectors operating with refrigerants (i.e. volatile fluids) in order to predict their performance under required operating conditions. The paper deals with experimental investigation of the performance of the two-phase ejector operating with refrigerant R-123. The testing apparatus and procedure have been described. The effect of compression ratio and entrainment ratio on the ejector efficiency have been showed on the basis of the experimental results.