Development of heat transfer coefficient and friction factor correlations for offset fins using CFD

Abstract

Purpose -In aerospace applications, due to the severe limitations on the weight and space envelope, it is mandatory to use high performance compact heat exchangers (CHEs) for enhancing the heat transfer rate. The most popularly used ones in CHEs are the plain fins, offset strip fins (OSFs), louvered fins and wavy fins. Amongst these fin types, wavy and offset fins assume a lot of importance due to their enhanced thermo-hydraulic performance. The purpose of this paper is to investigate the influence of geometrical fin parameters, in addition to Reynolds number, on the thermo-hydraulic performance of OSFs. Design/methodology/approach -A computational fluid dynamics approach is used to conduct a number of numerical experiments for determination of thermo-hydraulic performance of OSFs considering the various geometrical parameters, which are generally used in the aerospace industry. These investigations include the study of flow pattern for laminar, transition and turbulent regions. Studies are conducted with different fin geometries and comparisons are made with available data in open literature. Finally, the generalized correlations are developed for OSFs taking all geometrical parameters into account for the entire range of operations of the aerospace industry covering laminar, transition and turbulent regions. In addition, the effects of various geometrical parameters are presented as parametric studies. Findings -Thermo-hydraulic design of CHEs is strongly dependent upon the predicted/measured dimensionless performance (Colburn factor "j" and Fanning friction "f" vs Reynolds number Re) of heat transfer surfaces. Several types of OSFs used in the compact plate-fin heat exchangers are analyzed numerically.Research limitations/implications -The present numerical analysis is carried out for "air" media and hence these results may not be accurate for other fluids with large variations of Prandtl numbers. Practical implications -In open literature, these fins are generally evaluated as a function of Reynolds number experimentally, which are expensive. However, their performance will also depend to some extent on geometrical parameters such as fin thickness, fin spacing, offset fin length and fin height. Originality/value -This numerical estimation can reduce the number of tests/experiments to a minimum for similar applications.

Numerical analysis of compact plate-fin heat exchangers for aerospace applications

“…Finally, the f and j values are generated using CFD technique for different types of offset strip fins and wavy fins. The complete results can be seen in earlier papers (Ranganayakulu et al , 2008; Sheik Ismail et al , 2009; Chennu and Paturu, 2011; Chennu, 2016; Rao et al , 2013, 2016, 2015; Ramana Murthy et al , 2015; Muppala et al , 2015). However, the correlations generated using CFD are listed below for various types of fins in Table II for ready reference.…”

Forced convection heat transfer within a moderately‐stenosed, patient‐specific carotid bifurcation

“…Although forced convection heat transfer is not a new topic (Mauro et al, 2010;Al-Amri and El-Shaarawi, 2010;Codina et al, 2010;Rainieri et al, 2011;Chennu and Paturu, 2011;Drikakis and Asproulis, 2010;Jaluria, 2010;Lai et al, 2011;Manca et al, 2011;Samadiani and Joshi, 2010;Sunden, 2010), application to a patient-specific carotid geometry is new in the present study. A numerical method that has been proven to be both robust and accurate is the characteristic based split (CBS) scheme (Nithiarasu, 2003;Nithiarasu et al, , 2012Bevan et al, 2012).…”

“…It is clear from the bioheat transfer studies reported that heat transfer patterns in carotid arteries are important and thus in the present study a patient‐specific carotid geometry is employed to investigate forced convection heat transfer. Although forced convection heat transfer is not a new topic (Mauro et al , 2010; Al‐Amri and El‐Shaarawi, 2010; Codina et al , 2010; Rainieri et al , 2011; Chennu and Paturu, 2011; Drikakis and Asproulis, 2010; Jaluria, 2010; Lai et al , 2011; Manca et al , 2011; Samadiani and Joshi, 2010; Sunden, 2010), application to a patient‐specific carotid geometry is new in the present study. A numerical method that has been proven to be both robust and accurate is the characteristic based split (CBS) scheme (Nithiarasu, 2003; Nithiarasu et al , 2006, 2012; Bevan et al , 2012).…”

modeFRONTIER for Virtual Design and Optimization of Compact Heat Exchangers

“…Many authors in literature [7] consider, for the CFD determination of heat transfer and friction factor correlations of heat exchangers, the assumption of periodically developed flow and heat transfer. In fact, except for the development length, the flow regime is fully developed inside the liquid or air channels; therefore it is needed to specify periodic conditions at the boundaries of the HECE.…”