Analysis of flow boiling of ammonia and R-114 in a matrix heat exchanger

Conference · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5968464

Panchal, C B

An analysis is carried out for flow boiling in a vertical matrix aluminum heat exchanger. The prediction model, developed for thin film evaporation in a previous study, is extended to include heat transfer in the slug-flow regime that exists at low mass qualities. Appropriate criteria is used to switch from slug-flow to thin-film annular-flow analysis. The two-phase-flow convective heat transfer enhancement for the slug-flow is correlated with inclusion of fluid Reynolds and Prandtl numbers in addition to commonly used Martinelli parameter. This approach reflects transient nature of heat transfer in the slug-flow regime. The thin-film annular-flow analysis developed in the previous study is refined with inclusion of a reliable two-phase friction factor correlation. The experimentally measured pressure drop is used to validate the friction factor correlation. The resulting prediction method is used to predict exit mass qualities for ammonia and R-114. The experimental analysis includes flow boiling of ammonia and R-114 in a vertical brazed-aluminum matrix heat exchanger. The test unit has straight perforated fins on the fluid side and extruded rectangular channels on the single-phase (water) heating-media side. Only two parameters are adjusted to validate the analytical prediction method, the constant in the friction factor correlation, and the constant in the slug-flow heat transfer correlation. The results show that the combination of slug-flow and thin-film annular-flow model gives better prediction of the overall performance of the matrix heat exchanger than a single model applied for the whole range of mass qualities. 36 refs., 8 figs., 1 tab.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5968464
• Report Number(s): CONF-890819-15; ON: DE89012427
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420400* -- Engineering-- Heat Transfer & Fluid Flow
AMMONIA
BOILING
ENERGY TRANSFER
EQUATIONS
FLUID FLOW
FREONS
HALOGENATED ALIPHATIC HYDROCARBONS
HEAT EXCHANGERS
HEAT FLUX
HEAT TRANSFER
HYDRIDES
HYDROGEN COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PHASE TRANSFORMATIONS
PRANDTL NUMBER
REYNOLDS NUMBER
TWO-PHASE FLOW