High Temperature Heat Exchanger design problem

[arkusz3]

Hi,
I'm a postgraduate student and until now I was working with typical PV and HE. Management from my company wants to design flue gas cooler[water] from 800 celcius to 200 under atm. pressure and water from 25 to 45. More experienced CHE proposed S&T straight tube HE with one expansion joint and baffles. ID is 355mm and tube length 3200mm. I have concern about thermal stresses and thermal cycles. I wouldn't be concerned but he choosed wrong materials and expansion joint. Are my concerns valid? I attached concept pic
Sorry for any grammar mistakes.
Arkusz

 

[vpl]

he choosed wrong materials and expansion joint{/quote]

What did he choose and why do you believe he's wrong? After all you said he's more experienced and you're relatively new (based on saying you're a postgraduate student)? Did you ask him about his choice as a learning opportunity?

water from 25 to 45

25 to 45 what?? degrees Celcius? Still atmospheric? What flow rates? What is the expected heat transfer?

Finally is this a school assignment?

Patricia Lougheed

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[arkusz3]

celcius, still atmoshperic
water: 7800 kg/h
gas: 460 kg/h
It is not a school assignment.
The situation:
He's out of reach for two weeks and time is ticking. I've spoken with material engineer and checked the tables. No heat transfer yet.

Regards,
Arkusz

 

[arkusz3]

I forgot to mention; material for tubes was A 105

 

[cloa]

Attach the picture at least. engineering.com makes it easy.

 

[Arkusz33]

reuploaded it.

 

[SNORGY]

arkusz3:

Are you certain the material for the tubes is A-105, or did you mean A-106?

Is the gas on the shellside?

Heat transfer issues aside, I would be nervous about 800 C flue gas in contact with either the ID or the OD of the tubes, regardless of the water temperature. The graphitization threshold for carbon steel is about 427 C, and I suspect your mean wall temperature will be at least that.

Regards,

SNORGY.

 

[rmw]

A 105 is a forged piping components spec, and A 106 is a seamless pipe spec. Can you re-check your tube materials?

rmw

 

[Arkusz33]

thank you for your replies.
Gas is in the tubes side A 105 as material, that's the reason I'm worried about. At start-up temperature can reach those 800 deg and that's the temperature they want us to design it.
Arkusz

 

[srfish]

I started to estimate the metal temperatures for you but the tube side flow reflects a sp. heat of 0.565 Btu/lb F. What is this gas. The specific heat does not look like it is for the typical flue gas.