Separating and throttling calorimeter for steam

1. Mechanical Engineering/ College of Engineering/ University of Baghdad
Separating and throttling calorimeter for Steam
Saif Al-din Ali –A-
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
Abstract – In present study the Separating & Throttling Calorimeter set up is developed on Thermal x diesel fired
water tube Boiler (Three pass Reverse Flue coil type steam generator) in Thermal Power Laboratory and
experimentation is carried out to determine the quality of steam (The percentage by weight of steam in a mixture of
steam and water) passing through the steam main. The limitation of our experimentation is the wet steam. The
calorimeter results are not applicable to dry and superheated steam. The analytical analysis is also carried out using
steam table. The effect of parameters like steam temperature, steam pressure, water outlet temperature of economizer,
Fuel pressure, exhaust gas temperature, water and fuel flow rate on quality of steam is a recorded
Purpose to determine the steam dryness fraction (x)
I. Introduction
Steam is the major source for power generation in
steam engines or steam turbine. Steam is produced from
water by combustion of fuel in a boiler and employed.
The primary requirements of steam generators or boilers
are (i) Water must be contained safely. (ii)The steam must
be safely delivered in desired condition as regards its
pressure, temperature, quality and required rate. The
presence of moisture in steam causes a loss of heat from
the feed water temperature to the steam temperature. The
boiler consists of a membrane coil fitted in a shell which
in turn is enclosed by an air jacket. The coil forms the
combustion chamber (furnace). Burning fuel generates
heat which produces steam. High pressure pumps supply
water and fuel to the boiler and air is supplied by a
blower fan. Steam is generated within a few minutes after
firing the unit [1].
II. Theory
in the measurement of quality, the object is always to
bring the state of the substance from the two -phase
region to the single phase or superheated region, where
both pressure and temperature are independent, and
measured to fix the state by adiabatic throttling In the
throttling calorimeter, a sample of wit steam of mass (m)
and at pressure (P1) is taken from the steam main through
a perforated sampling tube. Fig 1
Fig.1. throttling calorimeter
Then it is throttled by the partially - opened valve
(Or orifice) to pressure (P2), measured by water
manometer, and temperature (t2) So that after throttling
the steam is in the superheated region. The process is
shown on the (T-S) diagrams in Fig 2.
Fig.2. Throttling process on T-S plot

2. Saif Al-din Ali Mechanical Engineering/ College of Engineering/ University of Baghdad
The steady flow energy equation gives the enthalpy
after throttling as equal to enthalpy before throttling The
initial and final equilibrium states2 (B) and 3(C) are
joined by a dotted line since throttling s irreversible
(adiabatic but not isentropic) the initial state (wet) is
given by (P1) and (x1) and the final state by (P2) and
(T2) superheated Now
Or
With (P2) and (T2) being known, (h2) can be found
out from the superheated steam table. The values of (hf)
and (hfg) taken from the saturated steam table
corresponding to pressure (P1). Therefore, the quality of
the wet steam (x1) can be calculated.
When the steam is very wet and the pressure after
throttling is not low enough to take the steam to the
superheated region, then a combined separating and
throttling calorimeter is used for the measure of quality.
Steam from the main is first passed through a separator
(Fig.3), where some part of the moisture separates out due
to the sudden change in direction and falls by gravity, and
the partially dry vapor is then throttled and taken to the
superheated region.
Fig.3. Separating and Throttling calorimeter
In Fig.4. Process (1-2) represents the moisture
separation from the wet sample of steam at constant
pressure (P1) and process (2-3) presents throttling to
pressure (P2). With (P2) and (t3) being measured, (h3)
can be found out from the superheated steam table
Fig.4. separating and throttling processes on h-s plot
Now
h3=h2=hfp1+x2hfgp1
Therefore, x2 the quality of steam after partial moisture
separation, can be evaluated. If (m) kg of steam is taken
through the sampling tube in (t sec), (m1) kg of it is
separated, and (m2) kg is throttled and then condensed to
water and collected, then (m=m1+m2) and at state (2), the
mass of dry vapor will be (x2m2). Therefore, the quality
of the sample of steam at state (1),(x1) is given by

3. Saif Al-din Ali Mechanical Engineering/ College of Engineering/ University of Baghdad
III. Tables
TABLE I
GEOMETRICAL DATA
Parameters Value1 Value2
P1 (bar) 2+1=3 1+1=2
m1 (ml) 1120 1000
m2 (ml) 180 240
ᴧp (mm H2O) 340 200
T3 c` 114.8 105
.
IV. Equations
Or
And
V. Calculation
Value1
Given:
State (1): P1 =300 kpa
From T (B.1.2) at P1=300 kpa
State (3):-
Now
From T (B.1.2) at
From T (B.1.3) at
By Interpolation
Value2;-
State (1): P1 =200 kpa
From T (B.1.2) at P1=300 kpa
State (3):-
Now
From T (B.1.2) at
From T (B.1.3) at
By Interpolation

4. Saif Al-din Ali Mechanical Engineering/ College of Engineering/ University of Baghdad
VI. Discussion
1. What is saturated liquid and saturated vapor?
Steam saturated
When water is present in its liquid and
gaseous state, its steam is called
saturated steam and its temperature is
boiling. In this case, the temperature of
the water and steam is constant
regardless of the amount of heat or
heat energy entered under pressure.
For example, at sea level, the boiling
point of water is 100 ° C and the water
temperature remains constant during
boiling (although heatedly supplied
from the outside) until the entire water
turns into steam, then the heat input
increases the heat of the steam. During
boiling, the water molecules store the
heat inside it as latent heat and part of
the heat gives it energy to make it
escape the liquid and become steamy.
"Which is the liquid that have enough energy to
be a saturated vapor"
Saturated vapor
"Which is the vapor that have enough energy to
be a superheated steam"
2. How much the dryness fraction for saturated
liquid.
In sat. Liquid
3. How much the dryness fraction for saturated
vapor.
4. What the dryness fraction is for sat. Liquid vapor?
5. What is the useful form calculating the dryness
fraction?
The object is always to bring the state of the
substance form the tow-phase region to the
single phase or superheated region etches
both pressure
On this temperature …
6. What is the meaning by saturated temperature
for water and what is the effect of change to
pressure on this temperature?
Which the temperature that make the water
Able to be steam the change in pressure
effect on it when the pressure get low they
sat temperature get low to and when the
pressure get high the sat temperature get
high too
7. How many Reglan that represent the transform in
phase for water plot it on diagram?

5. Saif Al-din Ali Mechanical Engineering/ College of Engineering/ University of Baghdad
8. Describe the components of the Separating
calorimeter and Throttling calorimeter
1. SAPARATING CALORIMETER
It consist of two concentric chamber,
the inner chamber, and the outer
chamber. Which communicates with
each other through an opening at the
top. As the steam discharge through
the metal baskets, which has a large
number of holes, the water partial due
to their heavier momentum get
separated from the steam and collected
in the chamber. The comparatively dry
steam in the inner chamber moves up
and through down aging through the
annular space between the two
chambers and enter the throttling
calorimeter
2. Throttling calorimeter
It consists a narrow throat (Orifice). Pressure
and temperature are measured by pressure
gauge and thermometer. The steam after
throttling process passes through the heat
exchanger and condensate is collected. Steam
Generator is also provided to supply the
saturated steam
It is a vessel with a needle valve fitted on
the inlet side. The steam is throttled
through the needle valve and exhausted
to the condenser.
9. The following procedure adopted for the
experimentation on separating and throttling
calorimeter.
1 . Start the boiler and supply steam to the
separating and throttling calorimeter unit.
2 . Start the cooling water flow through the
condenser.
3 . Open steam valve and allow the steam to flow
through the calorimeters to warm through the
steam.
4 . Open the throttle valve and adjust to give a
pressure at exhaust of about measured on the
manometer.
5 . Drain the separating calorimeter.
6 . Start the test and take readings .
7 . When a reasonable quantity of condensate is
collected measure the quantity of separated water
and the quantity of
Condensate.
10. Factors Influencing the Accuracy of Experience
1. Accuracy of taking readings
2. Dealing with units takes into account the
conversion
3. Periods between taking his readers and one
another
4. Losses caused by the device of leakage
5. Non-calibrating pressure devices and
maintaining valves
Acknowledgements
To the heat laboratory...
References
Lectures by Dr. Mohamed Abdel Raouf