Plate Heat Exchanger Literature Survey: Question related to Nusselt correlations

[jupemu]

Hi.

These questions are for those, who are familiar with Nusselt number correlations and PHE research history.

Q1:

Rosenblad and Kullendorff (1) had j_D=0.273 x Re^-0.303 for the correlation in their experiment. But Manglik (2) proposed Nu=0.289 x Re^0.697 x Pr^(1/3) for the correlation according to Rosenblad and Kullendorff (1).

I don't understand why the coefficient 0.273 from the original experiment has changed to 0.289? And where did the Pr^(1/3) come from since Rosenblad and Kullendorff didn't mention it in their original experiment?

Q2:

Heavner and Kumar (3) formulated correlations for different chevron angles. For example

β_avg 22.5° j_Nu=0.278 x Re^0.683

but according to Manglik (2), the correlation is Nu=0.278 x φ^0.317 x Re^0.683. So where did the enlargement factor φ^0.317come from?

1 Rosenblad, G., Kullendorff, A. 1975. Estimating Heat Transfer Rates from Mass Transfer Studies on Plate Heat Exchanger Surfaces. Wärme- und Stoffübertragung. Vol. (8), p. 187-191. Springer-Verlag.
2 Manglik, R.M. 1996. Plate heat exchangers for process industry applications: enchanced thermal-hydraulic characteristics of chevron plates. Process, Enhanced and Multiphase Heat Transfer, p. 267-276. Begell House.
3 Heavner, R.L., Kumar, H., Wanniarachchi, A.S. 1993. Performance of an Industrial Plate Heat Exchanger: Effect of Chevron Angle. AIChE Symposium Series. Vol. 89 (295), p. 262-267.

 

[MortenA]

Jupemu, i havnt read the various articles (quite old i suspect). I would think that the various emperical constants comes from different experiments and fitting of data? The enlargement factor must depend on some other parameters (at does Re), so look into what Manglik wants to cover with this factor.

Best regards, Morten

 

[jupemu]

Yes, those equations by Rosenblad & Kullendorff and Heavner et al. are curve-fits through sparse empirical data. And they are old, indeed.