Understanding Heat Exchanger Scaling Parameters

[samv]

Good Day,

I need help understanding scaling of heat exchangers. I have the book Hesselgreaves, Compact Heat Exchangers. P.8 talks about the geometric parameters - and p.12 has other parameters.

At this time I am concerned about the geometric parameters.

Ex. Dh2=Dh1/N,
Dh2 being hydraulic diameter of the first exchanger and
Dh1 being hydraulic diameter of second exchanger and
N being the scaling factor.

Also As2=As1/N^2 and
Ac2=Ac1/N^2,
L2=L1/N and
V2=V1/N^3

My question is :

I want to compare between plate-pin surface exchangers of different geometry. For example - fig 10-80 of Kays and London Compact Heat Exchangers. It gives me values of dh, plate spacing, pin pitch and pin diameter as well as (total heat transfer area / volume between plates) and (fin area / total area).

I am having a hard time understanding how the geometric relations for scaling given above relate to plate spacing, pin pitch and pin diameter.

Your input will be greatly appreciated... please advise if more details are needed.

samv

 

[samv]

hmmm - I'm not sure if no reply means nobody understands what I mean but here are more details

I look at fig 10-80 on p.261 of Kays and London
graph of f and StPr^(2/3) as a function of Re for a pin fin plate fin surface of the following dimensions:

Pin diameter=0.065"
Pin pitch parallel to flow=0.196"
total heat transfer area/volume between plates,ratio B=96.2ft^2/ft^3
fin area/total area=0.546

Now if I want to use the data for say a plate spacing of 0.255" or a factor N of 2, is it as simple as dividing all parameters with inches and feet as unit by 2?
pin diameter=0.065/2=0.0325,
pin pitch parallel to flow=0.196/2=0.098,
Pin pitch perpendicular to flow=0.238/2=0.119
Plate spacing, b=0.51/2=0.255
4rh=dh=0.0297ft=0.01485

and then the ratios I would have to deduct a factor from their definitions ...

Any comments anyone?

Regards,
samv