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CFD for prediction of k ‐factors of duct fittings
Author(s) -
Shao L.,
Riffat S. B.
Publication year - 1995
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.4440190110
Subject(s) - ashrae 90.1 , computational fluid dynamics , duct (anatomy) , hvac , mechanics , reynolds number , simulation , computer science , engineering , mechanical engineering , turbulence , physics , meteorology , medicine , pathology , air conditioning
The k ‐factors of duct fittings provided by CIBSE and ASHRAE are used extensively by HVAC system designers. Existing guides published by the two institutions do not include many of the duct fittings used in HVAC systems and they neglect to consider parameters, such as Reynolds numbers, which affect k ‐factors. More importantly, there are large errors in some of the data. This paper presents a study in which the computational fluid dynamics or CFD was applied to predict k ‐factors. Flow fields in duct fittings have been simulated by solving three‐dimensional Navier‐Stokes equations with the standard k ‐ε model. The finite volume approach was adopted and the SIMPLE algorithm has been used. It was found that the accuracy of k ‐factors is sensitively dependent on the presure sampling position, which may vary with many variables such as duct dimensions, type of fitting and flow speed. The predicted k ‐factors were compared with the CIBSE and ASHRAE data and although some close agreement were encountered for individual cases, in general there is no consistent agreement with either the CIBSE or the ASHRAE data set. It was shown that the knowledge of detailed flow patterns in individual duct fittings is crucial for accurate measurements of k ‐factors and should be acquired before the test is set up and carried out. Such an approach is important both for improving k ‐factor data accuracy and for providing a reliable basis for the development of CFD application.