2 replies to this topic

[ayan_dg]

I need to heat a tank by steam coil. The steam available is saturated steam at 3 barg. The heat duty is known to me. I want to find kg/hr of steam required.
I am not able to fix the exit condition of steam

Should I take saturated water at exit or subcooled water ?

What is the pressure drop that I may consider in the steam coil (general values will do )

[Art Montemayor]

You are wrong. You certainly can fix the exit condition of the steam; you do this with a pressure control valve (controlling the pressure in the steam coil), regulator, or a manual valve (together with a pressure gauge). What I am trying to point out to you is that you have omitted thinking about the practical side of engineering: it is not enough to be able to memorize and apply the latent heat transfer equation. As an engineer, you must think practically as to what the problem involves – in its totality. You should be able to resolve the entire problem – not just the heat transfer portion.

By learning how to manipulate and control the flow of fluids you will fully understand the largest segment of this problem. Every heat transfer application at steady state has to have some version of fluid control in order to ensure steady state. It just doesn’t happen by itself.

By determining or fixing the pressure in the steam coil you are now in a position to determine the amount of steam required because you now know: the conditions and enthalpy of the inlet steam into the coil. You must retain this steam condition within the coil, so you use a steam trap – or even better, a level trap with an automatic condensate drain valve that will drain the formed saturated condensate as fast as it is formed in the coil. Since you now have ensured that the steam will condense at a constant pressure (that you fix) and you have the automatic ability of draining the formed saturated condensate, you have solved the problem. Study well what I have described and you will start to form a mental picture of what is occurring in your heating coil problem and fully understand all the parameters and engineering principles applied.

Depending on the steam velocity, the size of the coil, and the steam load, you should expect a pressure drop of 1 to 3 psi across the coil.

I hope this explanation helps you out.

[Qalander (Chem)]

Dear I fail to understand/appreciate that,
If Heat duty is known to you thereby

the temperature in/out must be predictable

considering knowledge about the contents of being heated tank

State of water is fairly easily estimated,I believe.

However just a minor comment in such circumstance;

Most usually considered heat energy resource is steam's 'Latent Heat'i.e. a total condensation of steam should be considered as a usual customary.

Hope this should pave the way forward indeed!