Steam Flow and Steam Temperature

You should find all that you are looking for (general steam) here:

http://www.engineeringtoolbox.com/steam-condensate-properties-t_28.html

First go read the basic theory of steam & work on the steam tables.

Admittedly, I am not sure about the exact sense in which you are using the word "flow"; however, presuming that you mean something of the nature of flowing along a dimension of a conduit, then I would suppose that the mathematical relationship is defined by the coupling between the Momemtum Transfer Equation and Energy Transfer Equation. The former helps calculate the change in pressure with flow and temperature change; and the latter helps calculate the temperature change due to the pressure change. Of course, when properly written, the two equations will be coupled in ways that you will truly appreciate - which I believe is the answer to your question.

I hope that this is helpful.

sir ,

my question is that in a steam pipe line if we regulate the steam flow its temperature will increase ,decrease or remain constant

Steam tables are required to answer the question, as an expansion occurs at the regulating equipment. What are the temperatures and pressures both upstream and downstream of the regulating device?

What is the flowrate and the line size?

Alright then, there are, may be, two comments none of which you may like.

First tha basic answer to your question is that the mathematical relationship is the Universal gas Law: P = ρRT + ε(ρRT) + .. where the terms after the ρRT are cluster expansions accounting for non-ideality of the steam as gas.

Second, the change of state of the steam after the regulator will depend on the state of the steam that enters the regulator - meaning whether or not the steam is saturated.

State change of saturated steam is often calculated with steam tables, as everybody else has suggested. The actual reason is that engineers often, are not trained in Advanced Statistical and Quantum Mechanics to be able to calculate the non-ideality or cluster expansions precisely: While a super-heated steam may be calculated reasonably readily using close to neglect of the cluster expansion terms based strictly on methods of Statistical Physics, on the other hand saturated steam behaves close to dense gases and therefore requires resorting to Quantum Mechanics approaches for calcualting properties of Dense Gases.

However, you may be able to get away with using ideal gas law for super-heated steam until saturation. So to get started, get yourself a book on [Mechanical Engineering] Thermodynamics - that treats steam - and a good study of the Ideal Gas Law including the treatments of the non-ideality, and you are good to go. For saturated steam going into the regulator use Steam Tables as everybody else has advised.

I hope this is helpful - Good luck.

1 . Saturated Steam pressure is inter-related with temperature. A rise in steam pressure will give rise in steam temperature and a fall will give fall in steam temperature.

2 . Superheated steam is like Gas - it has no relation with steam pressure and is only used to drive steam turbine after which water is injected as it exists out driving the turbine blades and brought down to saturation temperature. Now go to 1.

Again, instead of wasting everbody's time why don't you first read the basic steam theory & steam tables.

Superheated steam is like Gas - it has no relation with steam pressure - Ducon

Just curious: Is it possible to have a gas that does not obey the Universal Gas Law [which shows Pressure relation] ?

Sorry you are right. Just have a habit of explaining to dum dums. What I actually ment was though it is steam but its temperature will not be corresponding to pressure and stated at a certain pressure(psi/bar) with so many degreees of super heat(F/C).It does not condense like saturated steam to give off its latent heat till its temperature reaches the saturation point.Superheated steam can be at any pressure with a higher dictated temperature of super heat based on design & engineering as per specific requirement of the operating turbine.

Saturated steam produced in a boiler is exposed to a surafe with a higher temperature, the temperature will increase above evaporatioin. The steam is then described as superheated by the number of temperature degrees through which it has been heated above saturation.Superheat cannot be imparted to the steam whilst it is still in presence of water, as any additional heat simply evaporates more water.

I think that if you do a pressure and velocity calculation upstream of the regulator and a pressure and velocity downstream, you can generally do the properties on a steam table to see what the temperature will be downstream. If you look in your thermodynamics handbook, I think that you treat the valve flow as isentropic, which is an approximation, but it allows you to calculate the temperatures from a known temperature upstream of the valve, so that the energy upstream equals the energy downstream of the valve.

I want to check my thermo book at home. Either way, a saturated vapor should maintain the same temperature. If it is a much lower downstream pressure, I suppose it could become superheated though.