clean tube temperature factor

[book110]

Hi
I have looked through the catalogs of several manufacturers of shell and tube heat exchanger. All of them offer just the suitable model and the heating surface.
I want select one steam - water HX from e.g. Bell&Gossett , so I had two questions about that:
First, what is the CLEAN TUBE TEMPERATURE FACTOR in the Table A and Capacity in the lasts Table in Bell & Gossett catalog?(Attached) ?
Second, how to obtain the U and, accordingly, the required steam flow rate?
tanks

 

[TinnedFishEnthusiast]

Table A: The clean tube temperature factor appears to be their own internal product selection convention, done for the sake of the customer. Taking into consideration required water flow rate, water temp in, water temp out, and steam pressure.

The 2nd table gives the overall pressure drop (in red, units of ft) for a given temperature factor above.

The equation below can be used to find U for the unit.

What is your available steam pressure? You can't size your exchanger or calculate U until you have that information.

 

[book110]

Table A: The clean tube temperature factor appears to be their own internal product selection convention, done for the sake of the customer. Taking into consideration required water flow rate, water temp in, water temp out, and steam pressure.

The 2nd table gives the overall pressure drop (in red, units of ft) for a given temperature factor above.

The equation below can be used to find U for the unit.

What is your available steam pressure? You can't size your exchanger or calculate U until you have that information.

Thank you for your answer, you know better than me that to calculate U from the equation you said, a lot of information is required, which usually the manufacturers do not present. they only show the heating surface related to model suggested.

so can it said ??U.A.(LMTD) ≥ m.c. (∆T=tube out -tube in)

so, U≥ m.c. (∆T=tube out -tube in) / A. (LMTD)

and LMTD= (tube out -tube in T)/ {ln (Ts- tube in)/ (Ts- tube out)}

 

[TinnedFishEnthusiast]

Watch the direction of your inequality signs, but even still, you aren't going to get much useful information out of this equation. Important heat transfer properties of the exchanger and both flows are not considered.

U is used to find q, not the other way around.

 

[book110]

Tank you for reply but I can’t understand you mean!

As far as I know, for calculating the amount of heat transfer from HX we must know U so that we can calculate the rate of steam by above equation. On the other hand for preventing the stall we must can calculate the partial load’s rate of heat transfer but I can’t find U from manufacture’s catalogue!

May you help me?

Watch the direction of your inequality signs, but even still, you aren't going to get much useful information out of this equation. Important heat transfer properties of the exchanger and both flows are not considered.

U is used to find q, not the other way around.

 

[TinnedFishEnthusiast]

Tank you for reply but I can’t understand you mean!

As far as I know, for calculating the amount of heat transfer from HX we must know U so that we can calculate the rate of steam by above equation. On the other hand for preventing the stall we must can calculate the partial load’s rate of heat transfer but I can’t find U from manufacture’s catalogue!

May you help me?

The clean tube temperature factor is the manufacturer's version of U. Given the inlet flow conditions and the desired output, they provide you a number to select the product you need. They probably just don't want to reveal more information about the construction of their products than what is necessary. Still, you need to find information about your steam supply