Scrapped Surface Heat Exchanger

[JoeChem]

Greetings,

I need to specify a scrapped surface heat exchanger for a food process. I have no experience with this type of exchanger and am searching for some information on typical overall heat transfer coefficients generated. I realize values will be material dependent and I am just looking for a typical range one can expect. If anyone knows of a good literature reference it would be very helpful as well.

Thanks in advance.

JoeChem

 

[25362]

This type of equipment is widely used in lube dewaxing by wax crystallization, for oleomargarine and shortening, and for sulphonation reactions. There are various suppliers of equipment with expertise in North America and Europe.

As for HTC, it is generally recognized that the bigger HT resistance is on the scraped surface.

Chem. Eng. Sci. 7, 166-175 (1958) brings an article by A.H.P. Skelland: Correlation of scaped-film heat transfer in the votator, proposing the following equation for the convection HTC on the inner scraped wall side:

Nu = 4.9 (Re)^0.57(Pr)^0.47(D/L)^0.37(Dn/V)^0.17​

Where

Nu: Nusselt number
Re: Reynolds number
Pr: Prandtl number

D: inner tube or pipe diameter, m
V: axial velocity of the liquid or slurry, m/s
n: revolutions of the scraper, 1/s
L: scraped length of tube or pipe, m

Ludwig's Vol. 3, suggests

for heating: 20-40 Btu/(h.ft².^oF)
for cooling: 10-30 Btu/(h.ft².^oF)

data representing tests on corn syrup, red oil, and golden oil (API = 19.7 @ 60^oF).