vertical steam condenser performance

[pastyl]

I have design a vertical beu heat exchanger. Steam is condensates at the outlet tubes area. Please let me know if I have right for the below:

1)At maximum load condensations will take place in a area A in the condenser tubes, normally a little bit smaller than the total tubes area Atot. It valids: Maximum load= mCpDT=UAMTD and (UAtotMTD-mCpDT)/UAtotMTD=overdesign at maximum load
In other words I have installed larger tubes (and area) for ensure condensation at maximum load
2) At minimum load the same is valid. Condensation is done in a smaller area lets say A1 and it valids minimum load= m1CpDT=UA1MTD and (UAtotMTD-m1CpDT)/UAtotMTD=overdesign at minimum load.
In any case steam will leaving as a condensate at near the saturation state and at the inlet pressure

I try to explain to client consultancy firm that in case of condensation and with no subcooling not all the area of the HEX is useful at all the loads but it is good to have it in order to ensure condensation at maximum load. I try also to explain that no subcooling you will have with no subcooling pool and in any case steam will leaving as a condensate at near the saturation state and at the inlet pressure. I think I have right

But since I am HEX manufacturer and not University and since to me the main problem is the construction and not the study, I wonder first If I am wrong, so any comment will be grateful, and ,second, if I am right why I am obligate to explain to our client consultancy firm things that normally you learn in University

 

[rmw]

All condenser designs have some margin for future fouling so that when the tubes are fouled to the extent of the margin there will still be 100% Area for condensation. Your comment "larger tubes" needs more explaining. Do you literally mean tubes that are larger or tubes whose total area is larger than the required area? Or does larger mean longer?

When you put a lot of extra area in the condenser, you enhance the tendency for subcooling. All that excess area will act to cool the condensate as it drips down toward the outlet resulting in subcooling.

What type of air removal zone do you have in this condenser?

rmw

 

[pastyl]

With larger tubes I mean longer. In vertical condensation lenght is plays role in heat transfer coef. of shell side. Finally you will have and larger area. Safety margin acc. me is not only to ensure that with fouling you will have 100% duty covered but because heat transfer equations used for find shell side heat transfer coefficient (thin film assumption) are simplified and valid only for one vertical tube. I want to cover any computational error for by bundle of tubes.Anyway I do not think that the sub cooling created from the contact of liquefied droplets with the cold tubes will be so dramatic.
Also do not forget that in anyway you cannot avoid sub cooling, as condensate extraction nozzle is higher than tube sheet and below it a pool will be created (vertical beu type)