Steam compressor enthalpy question. 1

[mielke]

I've seen a heat exchanger rated for a steam turbine operating at -12 PSIG. According to my tables this corresponds to an steam enthalpy of vaporization of about 1015.5 btu/lbm. yet the enthalpy is listed as 909 BTU/lbm @ turbine outlet.

I'm further confused by the heat load being given 750,000 BTU/HR. I have thought for just condensing the heat load was the mass flow rate times the enthalpy of vaporization. If this is true then the enthalpy based on the heat load is 770 BTU/lbm.

My questions are
1)what reasons would the enthalpy of a dry steam turbine be different from the tabulated value.
2)how do you calculate the heat load (if it is different than mass flow rate times the enthalpy for just condensing of dry steam condesor, or if it is this why would the heat load be different than that value)

Thank You

 

[katmar]

The exit steam is not necessarily at the dry saturated condition. Your conditions of 909 btu/lbm @ 2.7 psia imply a steam quality of about 79%, i.e. 21% of the steam has condensed.

You can download a free turbine steam requirements calculator from my web site. This program will tell you whether the exit steam is dry or not. See signature below.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[mielke]

thanks katmar,

the job was labeled as a 'dry steam condenser', I will double check with the source to make sure tho.

 

[mielke]

Katmar, off topic, i checked out your website and your software looks very helpful, but, and no offence, your site is rather dated.

I have a friend that is in college and does websites, she has done quite a few so far, if your interested i can pass on her info. She is very inexpensive and realy just wants to expand her portfolio, and you can check out her work quality.

If not no worries, i thought i'd just through that out there, and thanks again.