Re: Steam Quality

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Posted by Tony Garcia on January 26, 2000 at 23:17:40:

In Reply to: Steam Quality posted by Kyle Sexton on January 24, 2000 at 05:28:11:

: Hi,

: I'm a so-op student working at a moulding plant. We buy our steam from somewhere else, and I was curious if there's any quick and easy way to measure steam quality at various parts of the plant. (ie some sort of instrument you could insert into a pipe or something along that line) Thanks

I'm guessing that you mean you're a co-op student because I haven't a clue what a so-op student is. If so, then I hope you're an engineering student because this should be first year thermos' class. You must apply the state principle here for a closed system. You need two intensive properties in order to fix the state of the system.
You know Temperature (T1) and Pressure (P1) of the system and so I guess you would have a saturated system (assuming). Problem is your quality (x) is probably between liquid sat. conditions and vapor sat. conditions. In other words, you will need to determine enthalpy (h) through your steam tables by measuring T2 and P2 under another state. This should work since
x = (h2 - hf)/(hg - hf). Trick here is to use superheat as state 2 so that you won't have to worry about hf & hg in state 2. Find h2 from your superheat tables by actually measuring T2 & P2. hf and hg come from sat. steam tables for state 1.
I believe that this can be accomplished through the use of a throttling caliometric (sp?) device. The device should be installed in a vertical section, fully insulated, pressure reduced to atmospheric and then measure your T2 temperature. Use your superheat tables with T2 and P2 to find h2. The throttling should be an isoenthalpic condition and result in a superheat condition. This allows for h of water/vapor mixture of your system to equal h of the superheat vapor in your measurment device.
I know this may sound like alot, but this is why you're doing a co-op. If you can purchase such a device and there are presently good locations for use then, yes there is a quick and easy way to this. For my own curiosity, are you trying to determine the cost analysis of each maufacturing process?
As always, please double check this reasoning .

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