I was very confused about the condensate temperature from the high pressure steam. For example, if the condensate is from a high pressure steam of 125psig, is it going to be 353F or is it going to be 212F same as the 0psig condensate?

Remember saturation temps, subcooling and superheat?

Look at a steam table to find the "saturation temp" associated with the fluid (water) pressure. Then if the actual water temperature is above the sat'd temp (for that P) you have "superheated" condensate: [Tsh = Tact-Tsat]

If the Tact is below the Tsat, then you have subcooled condensate: [Tsat-Tact = Tsc]

Why is this important? Ideally you want to minimize heat input @ boiler to change the condensate back to steam; so you shouldn't subcool the water ... it should be sat's so the entire Hfg is not needed to change phase (1,000BTU/lb-F).

This mixed condensate [part sat'd, part superheated and maybe part subcooled (a really small par; hopefully)]has a certain "quality" depending on the % of the total mass that is fully sat'd. Fully sat'd condensate requires the least amount of heat to change back to the steam phase. Let's say that 50% "quality" requires only 500 BTUH/lb-F...... See what I mean???

Any "Steam Experts" out there are welcome to comment as well.

Buddha's advice 2,500 yrs ago (I'm Christian!!???!!): "After deep, careful observation/analysis; and it agrees with reason, is conducive to the common good: accept it and live up to it."

The differential pressure across the orifice in the trap will determine the flow. If there no temperature control valve that will throttle the upstream steam pressure, then the only time you'll have pressure lower than 125 is on a start up. If your trap discharges directly to a vented receiver, then the downstream pressure is "0". If it discharges to a condensate header with traps from other points also feeding into it, the pressure across the trap in question can (and likely will) vary.

Select the trap size based on the operational requirements. However, make sure the BODY of the trap you select is rated for the safety valve setting, which is very likely 150 PSIG. There are a huge number of systems like this (operating at 125 PSIG) that are just full of under-rated components like valve, strainer & trap bodies.

As far as steam is concerned 125 psi is not high pressure and is called medium pressure. (pardon me from being irrelevant at this moment) When heat transfer takes from steam to some other mass, latent heat is being transfered to the mass and x deg.C steam becomes x deg.C water(condensate).

Some traps (thermostatic)restrict condensate flow to a certain offset so that you can utilise high sensible heat also. As long as your condensate flows in a pipeline you can consider it's pressure equal to that of steam pressure (unless you didn't install a pressure gauge) and the temperature is saturated temperature. The moment condensate enters atmosphere part of condensate flashes because of the pressure drop by taking heat from the remaining condensate. So remaining condensate temperature drops down.

As for Goorah I disagree with superheated condensate as that case is hypothetical only. There will be a mix of condensate and steam but not superheated condensate.

One Kg of water at 100 deg.C takes 550Kcal/Kg of heat to evaporate. You require only 1 Kcal/Kg of heat to heat up water by 1deg.C. That is why Saturation and total heat capacity are not directly proportional by multiples.

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