New methods of forecasting flow regimes for boiling refrigerant in macro- and minichannels

DOI: 10.21047/1606-4313-2016-15-2-67-70
UDC 621.56

New methods of forecasting flow regimes for boiling refrigerant in macro- and minichannels

Malyshev A.A., Kisser K.V., Filatov A.S.


Abstract
Nowadays there are a number of mapsfor boiling regimes of two-phase refrigerant flows, but they based on expenditure parameters that have a limited physical sense. The fact does not allow to extend the scope of the mapapplication and does not allow combing the data on boiling in macro- and minichannels. This article presents a modified map of two-phase flow boiling regimes based onthe true parameters of the phases which summarizes the data for the boiling of R134a, R12, R22, and R717refrigerant, water, as well as adiabatic hydrogen-air mixtures in the channels with an internal diameter d0> 5mm, and the data by D. Khovalyg when R134a refrigerant boilsin macro and minihannels with hydraulic diameter = 538 μmm. Fr/We ratio for the balance of gravity forces and surface tensionis consideredwhich takes into account to the maximum extent mode transfer ofthe flow in the channels of small equivalent diameters. A modified formula for calculating true void fraction duringboilingin the macro- and minichannelsis obtainedwith the ratio.

Keywords: two-phase flow, refrigerant flow conditions, flow regime map, phase slip, mixture speed, true rate of steam and fluid,regime transition border.


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