Wpływ niestabilności hydrodynamicznych na efektywność wymiany ciepła podczas skraplania czynnika chłodniczego R404A w minikanałach rurowych

• Autorzy: Kuczyński W. , Charun H.

Warianty tytułu

EN

Influence of hydrodynamic instability on the efficiency of heat transfer during the condensation of R404A refrigerant in pipe mini-channels

• Języki publikacji: PL

Abstrakty

PL

W pracy przedstawiono wyniki badań eksperymentalnych dotyczących określenia wpływu niestabilności hydrodynamicznych na intensywność wymiany ciepła podczas skraplania czynnika chłodniczego R404A w minikanałach rurowych. Miara efektywności procesu skraplania jest wartość współczynnika przejmowania ciepła alfa. Szczególnie ważne jest określenie wartości tego współczynnika w dwufazowej strefie skraplania w skraplaczu kompaktowym. W pozostałych strefach, tzn.: schłodzenia pary przegrzanej i dochłodzenia skroplin efektywność cieplna jest znacznie mniejsza. Niestabilności hydrodynamiczne o charakterze periodycznym wpływają na zmiany wielkości tych stref. Zmniejszenie wartości współczynnika przejmowania ciepła a w strefie dwufazowej prowadzi do obniżenia intensywności procesu odbioru ciepła w całym skraplaczu. Badania eksperymentalne wykonano w warunkach skraplania czynnika chłodniczego R404A w poziomych minikanałach rurowych o średnicy wewnętrznej d = 0,64; 0,90; 1,40; 1,44; 1,92; 2,30 i 3,30 mm. Zakłócenia procesu skraplania wywoływano okresowym (periodycznym) zatrzymaniem i ponownym włączeniem przepływu czynnika. W zakresie częstotliwości / = 0,2+5 Hz generowanych periodycznie zakłóceń stwierdzono wyraźny, niekorzystny ich wpływ na intensywność wymiany ciepła podczas procesu skraplania w minikanałach rurowych. Zmniejszenie intensywności wymiany ciepła podczas procesu skraplania wywołane niestabilnościami hydrodynamicznymi zostało przedstawione w postaci zależności współczynnika przejmowania ciepła a od stopnia suchości x oraz częstotliwości/występujących zakłóceń. Określono wpływ właściwości czynnika chłodniczego, średnicy minikanałów i częstotliwości/na zjawisko "tłumienia" zakłóceń periodycznych w minikanale rurowym.

EN

The paper present the results of experimental investigations concerning the determination of the influence of hydrodynamic instabilities on the heat transfer intensity during the condensation of R404A refrigerant in pipe minichannels. The value of the heat transfer coefficient alfa constitutes the measure of the effectiveness of the condensation process. It is particularly important to determine the value of the coefficient in the two-phase condensation area in a compact con-denser. In the remaining areas, i.e. precooling of superheated vapor and subcooling of the condensate, the heat efficiency is substantially smaller. Hydrodynamic instabilities of a periodic nature have an influence on the changes of the sizes of these areas. A decrease of the heat transfer coefficient " in the two-phase area results in a decrease of the intensity of the heat removal process in the whole condenser. The experimental investigations were conducted in the conditions of the condensation of R404A refrigerant in horizontal pipe minichannels with internal diameters d = 0.64; 0.90; 1.40; 1.44; 1.92; 2.30 and 3.30 mm. Disturbances of the condensation process were induced with a periodical stop and a repetition of the flow of the refrigerant. In the range of frequencies f= 0.2*5 Hz of periodically generated disturbances, their evident and unfavorable influence was established on the intensity of the heat transfer during the condensation process in pipe minichannels. The reduction of the intensity of the heat transfer during the condensation process which was induced with hydrodynamic instabilities was presented in the form of the dependence of heat transfer coefficient a from the vapor quality x and the freąuencies of the disturbances occurring. The influence was determined of the refrigerant, the diameter of the minichannels and frequencies on the "damping" phenomenon of periodical disturbances in a pipe minichannel.

Słowa kluczowe

PL

niestabilność hydrodynamiczna; wymiana ciepła; R 404A

EN

hydrodynamic instability; R404A; heat transfer

• Wydawca: Wydawnictwo SIGMA-NOT
• Czasopismo: Chłodnictwo : organ Naczelnej Organizacji Technicznej
• Rocznik: 2011
• Tom: R. 46, nr 6
• Strony: 4--10
• Opis fizyczny: Bibliogr. 43 poz., rys.

Twórcy

autor

Kuczyński W.

autor

Charun H.

• Katedra Techniki Cieplnej i Chłodnictwa Politechnika Koszalińska

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