Steam Surface Condensers

[Patrick3862]

I realize that the performance of a steam surface condenser declines as the inlet temp increases. My question is this: is there a critical point that the vacuum suddenly drops relatively quickly. Is there an equation showing a general vacuum curve relative to inlet temp?

Thanks in advance!

 

[Ahmedv]

Hello Patrick
When you say that the inlet temperature increases, please advise exactly which temp you are referring to, ie is it the inlet water temp or the inlet steam temperature.
Ahmed Vawda
Process Engineer
Al Khaleej Sugar - Dubai
avawda@aksugar.co.ae

 

[Patrick3862]

The inlet water temp

 

[Ahmedv]

Hi
With the flow constant, the vacuum condenser can be imagined as a water heater removing x KW of heat.
An increase in inlet water temp results in a reduction in the KW removed and subsequent reduction of vacuum. The relationship is purely thermodynamic and is steady, I dont expect dramatic drop in vacuum, unless there is a dramatic increase in inlet water pressure.

Contact me for an excel spreadsheet that may be of some help. Ahmed Vawda
Process Engineer
Al Khaleej Sugar - Dubai
avawda@aksugar.co.ae

 

[poetix99]

Refer to thread 391-21572.

A condenser is a heat exchanger. Develop, for your better understanding of condensers, a generic understanding of heat exchangers: area, LMDT, fouling factor,...

The functional relationship between cooling water temp. and exhaust pressure (all other things being constant) is monotonic, and does not have a "critical point".

As you move further from the condenser's design point, the exhaust pressure will increase faster, but it will be a smooth curve.

If you are observing a "sudden change in exhaust pressure", this is because something else is changing at the same time (perhaps the amount of dissolved gases (air) in your cooling water).

If you are HOPING to attain such a critical point of "sudden decrease of exhaust pressure" with your system, stop hoping.

 

[Ahmedv]

Hi
Sorry, I made a typo on my last posting
"I dont expect dramatic drop in vacuum, unless there is a dramatic CHANGE in inlet water pressure."

I agree with Poetix99's assessment of the possible cause.
More information is required in order to diagnose the real cause.

In our vacuum condenser, the vacuum fluctuates when there is a sudden increase in vapour load, or when there is a sudden ingress of air due to the evacuation of a batch evaporator. Ahmed Vawda
Process Engineer
Al Khaleej Sugar - Dubai
avawda@aksugar.co.ae