simple HX surface area question

[dextermech]

This may sound like a very stupid question, but if I have (10) one square foot aluminum plates stacked in a plate-type HX, is my total heat exchange area 10 square feet, or 20 square feet? I assume it's 10?

 

[pmover]

heat exchanger surface area is defined as that portion of surface area in which heat is transferred from one warmer fluid to another cooler fluid. the surfaces include horizontal and vertical surfaces.
think about the flow passages of the 2 different fluids in your case.
also, plate HEX's generally have smaller flow passages, hence allow for greater surface area per volume of space occupied. there are shortcomings of these type exchangers as well.

good luck!
-pmover

 

[dextermech]

So then the answer in my example above would be 10 square feet?

 

[IRstuff]

Assuming adequate fluid flow, you have 20, but there may be a decrement for the fin efficiency

TTFN

 

[dextermech]

I'm going to punch ribs into the plates to add turbulence, which will hopefully increase the "U" value...

So that's interesting, I count the surface area of BOTH sides of a single .036" thick plate...which means my HX should only be half as big and half as expensive as I thought...

 

[25362]

In heat transfer calculations both parallel surfaces of a flat thin plate, or a tube for that matter, are counted as one, perpendicular to heat flow, as explained by pmover.

 

[dextermech]

OK now there are 2 different answers here. Do we know what a plate type heat exchanger is? If I look at one plate, do I cound the surface area of ONE side or both sides?

 

[telecomguy]

I guess it depends on what you mean by "total heat exchange area". There is heat exchanged on the hot side of the plates through convection (10 sqft). There is conduction through the plates. And there is convection on the cool side of the plates (10 sqft).

If you're calculating the heat transfer, you have to look at each piece of the puzzle. If the term is some industry standard term, then we're back to what is the definition of the term.

<tg>

 

[rmw]

The way you have asked the question, the answer is 10. But in actuality you only have 8 because the top plate and bottom plate are boundary plates and heat transfer to the surroundings is ignored.

rmw

 

[dextermech]

My top and bottom boundary plates (actually made of 1018 CRS) are #11 and #12, so I wasn't counting them, but thanks for clarifying that.