Modelowanie skraplania czynników chłodniczych w obszarze pary przegrzanej

• Autorzy: Florianowicz M. , Bohdal Ł.

Warianty tytułu

EN

Modeling of the refrigerants condensationin the superheated vapor area

• Języki publikacji: PL

Abstrakty

EN

A simple calculation model that was proposed to determine the value of the heat transfer coefficient during of refrigerant condensation in channel in the area of superheated vapour. The model used a two thermal effects, in example the chilling effect of superheated vapour and further is condensed her near the wall. The assumption was introduced that the heat transfer coefficient recognized a total termal efficiency of both these effects. In the single-phase area of superheated vapour was assumed that the intensity of heat transfer resulted directly from the forced movement of refrigerant in the channel and the traffic associated with the replacement of heat mass due to start of the local condensation in a channel on the wall. The additional movement of superheated vapour this causes from the flow core towards the sublayer boundary, which located at the cooled wall of the channel. The additionally intensifies the forced convection in the channel. The total value of the heat transfer coefficient during the refrigerant's condensation in the superheated vapour is the sum of two products. The first product recorded value of the heat transfer coefficient in the single-phase superheated vapour and its relative overheating in the flow core, the second heat transfer coefficient during the vapour condensation and the relative undercooling on the channel wall. It was proved that the heat transfer coefficient during forced convection in a channel of superheated vapour can be determined according to generally known dimensionless reported in the literature. This also applies to the calculation of the heat transfer coefficient for refrigerant's condensation in the flow. Also developed their own experimental correlations which described the increase the heat transfer due to the locally condensation of the start on the channel wall. It results from the additional movement of superheated vapour in the toward the boundary sublayer from the flow core, which located at the cooled channel wall. The value of the total heat transfer coefficient alpha(c) obtained from the calculation, compared with the results of the experimental investigations for R134a and R404A refrigerants, concerning a channel with diameter d = 0,98-13 mm. It was said that in the range +/- 25% occurs with the results of the experimental investigations compatibility the calculation results for the 75% points. Despite considerable simplifications proposed the calculation model can be recommended to conducted the calculations the value of heat transfer coefficient during the refrigerant's condensation in the superheated vapour in the channel. Because it takes into account the relative superheating vapour in the flow core and the relative undercooling refrigerant on the wall in a channel. This allows to lead calculations of local condensation in the whole range since its inception, the proper condensation to obtain, when the vapour temperature reaches the saturation temperature T-s in the flow core.

Słowa kluczowe

PL

para przegrzana; skraplanie; czynnik chłodniczy

• Wydawca: Politechnika Koszalińska
• Czasopismo: Rocznik Ochrona Środowiska
• Rocznik: 2012
• Tom: Tom 14
• Strony: 393--406
• Opis fizyczny: Bibliogr. 12 poz., rys.

Twórcy

autor

Florianowicz M.

• Politechnika Koszalińska

autor

Bohdal Ł.

• Politechnika Koszalińska

Bibliografia

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