Exp 4 - Separating and Throttling Calorimeter

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FACULTY : ENGINEERING TECHNOLOGY

EDITION:

LABORATORY: THERMODYNAMICS LABORATORY

REVISION NO:

EXPERIMENT: SEPARATING AND THROTTLING CALORIMETER

EFFECTIVE DATE:

AMENDMENT DATE:

FACULTY OF ENGINEERING TECHNOLOGYDEPARTMENT OF CHEMICAL ENGINEERING TECHNOLOGY

CHEMICAL ENGINEERING THERMODYNAMICS LABORATORY

LABORATORY INSTRUCTION SHEETS

COURSE CODE BNQ 20104

EXPERIMENT NO. EXPERIMENT 4

EXPERIMENT TITLE SEPARATING AND THROTTLING CALORIMETER

DATE

GROUP NO.

LECTURER/ INSTRUCTOR/ TUTOR

1) DR. NADIRUL HASRAF BIN MAT NAYAN

2) PUAN AZIAH BT ABU SAMAH

DATE OF REPORT SUBMISSION

DISTRIBUTION OF MARKS FOR LABORATORY REPORT

ATTENDANCE/PARTICIPATION/DISPLINE /5%

INTRODUCTION: /5%

PROCEDURE: /5%

RESULTS & CALCULATIONS /15%

ANALYSIS /15%

DISCUSSIONS: /20%

ADDITIONAL QUESTIONS: /15%

CONCLUSION: /10%

SUGGESTION & RECOMENDATIONS /5%

REFERENCES: /5%

TOTAL: /100%

EXAMINER COMMENTS: RECEIVED DATE AND STAMP

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STUDENT CODE OF ETHICS

DEPARTMENT OF CHEMICAL ENGINEERING TECHNOLOGY

FACULTY OF ENGINEERING TECHNOLOGY

I hereby declare that I have prepared this report with my own efforts. I also admit

to not accept or provide any assistance in preparing this report and anything that

is in it is true.

1) Group Leader __________________________________________(Signature)Name : _____Yeu Ho Kiet__________________Matrix No. : _____AN140177___________________

2) Group Member 1 __________________________________________(Signature)Name : ____Kogulan a/l Subramaniam_____Matrix No : ____DN140115_____________________

3) Group Member 2 __________________________________________(Signature)Name : _____Jaayshini a/p Murugiah_____Matrix No. : _____AN140023___________________

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1.0 OBJECTIVES

a) To determine the dryness fraction of steam.

2.0 LEARNING OUTCOMES

At the end of this experiment students are able to:

a) Understand the concepts of dryness fraction.

b) Implement and analyse the required data collectively within member of

group.

c) Produce good technical report according to the required standard.

3.0 INTRODUCTION

3.1 Dryness Fraction

The dryness fraction is defined as the quantity of dry vapour present in any

wet vapour mixture.

3.2 Separating Calorimeter

This is mechanical process where the incoming steam to the calorimeter is

made through a series of obtuse angle the inertia of the water droplets

causes them to separate from steam flow. If

Wi = quantity of dry steam discharged from calorimeter

Ws = quantity of water separated in the calorimeter in the same time

interval;

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then the dryness fraction as measured by the separating calorimeter (Xs)

3.3 Throttling calorimeter

Consider a fluid flowing through a throttling orifice from higher pressure P1

to a lower pressure P2. From the steady flow energy equation, it can be

shown that adiabatic throttling is a constant enthalpy process. The wet

steam before the throttling will become superheated steam at the lower

pressure after throttling.

Enthalpy of wet steam P1 before throttling;

Where, = specific enthalpy of saturated liquid (sensible heat)

corresponding to pressure P1

= dryness fraction of steam measured by throttling calorimeter

= specific enthalpy of vaporisation (latent heat) corresponding to

pressure P1

Enthalpy of superheated steam at P2 after throttling

Where, = specific enthalpy of saturated vapour corresponding to

pressure P2

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= specific heat at constant pressure

= steam temperature at throttling calorimeter

= saturated steam temperature corresponding to pressure P2

Since H1 = H2,

3.4 Combined Separating and Throttling

If w = quantity of water in steam leaving the separating calorimeter and

entering the throttling calorimeter, then by definition of dryness fraction

But the separating calorimeter has already removed WS water, therefore

total quantity of water is (WS + w) in wet steam (WS + Wt)

Applying this to the definition of dryness fraction

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But w = Wt (1 – Xt)

From equation (1),

Therefore:

True dryness fraction,

X = XS x Xt (3)

4.0 INSTRUMENTS /APPARATUS

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Figure 1: Cusson P7660 Separating and throttling calorimeter

Figure 2: The equipment panel mounted on a freestanding framework

5.0 PROCEDURE

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1. Cooling water flow through condenser is started.

2. Condensate collecting vessel is placed under the condenser

outlet.

3. Small valve on throttling calorimeter is closed to isolate the

manometer.

4. The steam valve is opened and the steam is allowed to flow

through the condenser is sufficient to condense all the steam.

5. When condition have stabilised, the valve to the manometer

is opened.

6. The separated condensate level is allowed to build up in the

separating calorimeter until liquid can been in the calorimeter condensate

level tube.

7. The condensate-collecting vessel is drained.

8. The main condensate-collecting vessel is refitted under the

condenser outlet.

9. Measure and record;

a) Initial value of fluid level in the separating calorimeter.

b) Initial value of condense level in the main condensate-collecting vessel.

c) The steam pressure in the steam main.

d) The steam pressure after throttling.

e) Steam main steam temperature.

f) Temperature in the throttling calorimeter.

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g) Barometric pressure.

The value from (c) to (f) parameter values should be checked about six

times during the course of measurement.

10. The apparatus is allowed to cool and the condenser cooling

water is turned off.

11. The separating calorimeter is drained.

12. The condensate-collecting vessel is emptied.

6.0 RESULTS & CALCULATIONS

6.1 Results.

Table 5.1 Observed readings

Parameters 1 2 3 AverageBarometric pressure, bar.abs

1.013 1.013 1.013 1.013

Separator: Steam 3.513 4.513 5.013 4.346

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pressure, bar.absThrottle: Steam pressure, mm.Hg, bar abs

1.0197

1.01971.018

31.019

Trottle: Difference in mercury level due to water, mm.Hg

5 5 4 4.667

Separator: Steam temperature, oC

144 152 154 150

Throttle: Steam temperature, oC

108 114 110 110.67

Separator: Amount of collected water, mL

10 20 20 16.67

Throttle : Amount of condensed water, mL

225 200 225 216.67

Table 5.2: Derived results

Parameters Average

Throttle: Specific heat at constant pressure, kJ/kgK 1.907

Separator: Steam pressure, bar.abs 4.346

Throttle: Steam pressure, bar.abs 1.0192

Separator: Saturated liquid enthalpy, kJ/kg 617.45

Separator: Latent heat, kJ/kg 2124.33

Throttle: Vapour Enthalpy, kJ/kg 2675.83

Throttle: Saturated steam temperature, oC 100.12

Separator: Dryness fraction of steam, XS 0.9286

Throttle: Dryness fraction of steam, Xt 0.9784

Steam Line: Dryness fraction, X 0.9085

Sample calculation:Average barometric pressure = 1.013 x 3/3

= 1.013 bar abs

Separator: Average steam pressure = (3.513+ 4.513+ 5.013) / 3

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= 4.346 bar abs = 434.6 kPa

Average steam temperature = (144+152+154)/3 = 150 ˚C

Average amount of collected water, Ws = (10+ 20+ 20)/3 = 16.67 mL

From property table, using interpolation, P= 434.6 kPa:

Saturated liquid enthalpy = (623.14-604.66)(434.6-400)/(450-400) + 604.66 = 617.45 kJ/kg

Latent heat = (2120.3- 2133.4) (434.6-400)/ (450-400) + 2133.4 = 2124.33 kJ/kg

Xs = 216.67/ (216.67+16.67) = 0.9286

Throttle:Average difference in mercury level due to water = (5+5+4)/3

= 4.667 mm Hg

Average steam pressure = (4.667x 10-3) x 13.6 x 9.81 = 0.6227 kPa = 0.006227 bar + 1.013 bar = 1.019 bar abs = 101.9 kPa

Average steam temperature = (108+114+110)/3 = 110.67 ˚C +273.15 = 383.82 K

Average amount of condensed water, Wt = (225+200+225)/3 = 216.67 mL

From property table, using interpolation, P= 101.9 kPa, T = 383.82K:

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Specific heat at constant pressure = 32.24+ (0.1923 x 10-2 x 383.82)+(1.055 x 10-5 x 383.822)+

(-3.595 x 10-9 x 383.823) = 32.24+0.73809+1.5542-0.20327

= 34.33017 kJ/kmolK= 34.33017 kJ/kmolK 18 kg/kmol= 1.907 kJ/kgK

Vapour enthalpy = (2684.9-2675.6)(101.9-101.325)/(125-101.325) + 2675.6 = 2675.83 kJ/kg

Saturated steam temperature = (105.97-99.97)(101.9-101.325)/(125-101.325) +

99.97 = 100.12 ˚C

= [2675.83+ 1.907(110.67-100.12) – 617.45]/2124.33= 0.9784

X = Xs x Xt

= 0.9286 x 0.9784 = 0.9085

7.0 ANALYSIS

Based on the experiment conducted, we obtained the average value of

Barometric pressure; bar.abs is 4.013, the average value of separator: steam

pressure, bar.abs is 4.346, the average value of throttle: steam pressure, bar.abs is

1.019, the average value of throttle: difference in mercury level due to water,

mm.Hg is 4.667, the average value of separator: steam temperature, ˚C is 150, the

average value of of throttle: steam temperature, ˚C is 110.67, the average value of

separator: amount of collected water, mL is 16.67 and the average value of throttle:

amount of collected water, mL is 216.67.

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Based on the results obtained, the average values of throttle: specific heat at

constant pressure, 1.907 kJ/kgK, separator: steam pressure, 4.346 bar.abs, throttle:

steam pressure 1.019 bar.abs, separator: saturated liquid enthalpy, 617.46 kJ/kgK,

separator: latent heat, 2124.33 kJ/kgK, throttle: vapor enthalpy, 2675.83 kJ/kgK,

throttle: saturated steam temperature, 100.12 ˚C, separator: dryness fraction of

steam, Xs, 0.9286, throttle: dryness fraction of steam, Xf 0.9784 and steam line:

dryness fraction, X 0.9085 were calculated.

From the experiment, we can see that the dryness fraction for separating

calorimeter is lower than throttling calorimeter because in separating calorimeter

the steam is wetter. Temperature of in throttling calorimeter is higher than its

saturated steam temperature because it is already in superheated state.

8.0 DISCUSSIONS

Using the readings that were recorded in the lab the dryness fraction of the steam

could be found, using the theoretical equations. From the results obtained the

dryness fraction is 0.9286 at xs and 0.9784 at xt. The combined separating and

throttling calorimeter was found by using equation 7 where both xs and xt were

multiplied to get 0.9085. Based on the results of the readings we obtained when

conducting the experiment in the lab, it can be said that using the readings that

were recorded in the lab, the dryness fraction of the steam could be found in

regards with the use of the theoretical equations from the thermodynamics

textbook. From the results obtained, the dryness fraction is 0.9286 at xs this

showed us that at that point in time the steam is 93% dry and 7% wet. We got

0.9784 at x1 so that showed us that the steam is near to superheated because it’s

value near to 1 at that point so the combined separating and throttling

calorimeter’s dryness faction was found by using the equation where both xs and xt

were multiplied to get the value of 0.9085. This shows that the state of the steam is

still wet because the value of the dryness fraction of steam is less than 1. If the

steam whose dryness fraction is to be determined is very wet then throttling to

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atmospheric pressure is not sufficient to ensure superheated steam at exit. In this

case it is necessary to dry the steam partially, before throttling. This is done by

passing the part of steam from the steam main through separating calorimeter as

shown in figure. The steam is made to change direction suddenly, and the water,

being denser than the dry steam is separated out is measured at the separator, the

steam remaining, which now has dryness fraction, is passed through the throttling

calorimeter.

With the combined separating and throttling calorimeter it is necessary to condense

the steam after throttling and measure the amount of condensate (Ms).

It was observed that with increasing the boiler steam pressure there is increase in

steam temperature and when the part of the steam enters into the separating

calorimeter steam pressure before throttling is higher than steam pressure after

throttling. It is also observed that steam pressure decreases after throttling.

Corresponds to the steam pressure after throttling, from steam table it was noted

that steam temperature measured is greater than the saturation temperature.

Therefore the steam becomes superheated steam. From the measured values the

various parameters like dryness fraction of steam, enthalpy of superheated steam,

equivalent evaporation and factor of evaporation and boiler efficiency calculated.

Steam calorimeters are commonly used in process industries, power plants and

other industries to determine the quality of steam. Steam quality is a very critical

parameter in steam applications as the performance of steam processes depends

on it. Conventionally, separating or throttling or combined separating and throttling

calorimeters are being used for this purpose. An electrical calorimeter is a concept

not well covered in literature, though it has wide range of application and scope

with accuracy and this may offset the limitations of the conventionally used

calorimeters. It is found that the proposed concept can be applied conveniently to

find the dryness fraction and can be validated experimentally. In the present

experimental work, therefore, electrical energy is used to find dryness fraction of

steam. The design of the system is based on fundamental principles of

thermodynamics. Mainly, steady flow energy equation has been applied to derive

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the desired results. As per the requirements, specifications of various components

like steam generator, super heater, etc., have been decided. In the process,

electrical energy is used to make dry saturate from the wet steam in a controlled

manner, and steam parameters are recorded along with the heat supplied to the

wet steam. The key feature of the system is easiness of use without compromising

the accuracy. It is also found that this system can be used for a wide range of the

dryness fraction unlike conventional methods, which give results in a narrow range.

9.0 ADDITIONAL QUESTIONS

1. What is the steam dryness fraction?

Wet steam consists of dry saturated steam and water particles in

suspension. The dryness fraction of steam is defined as the ratio of

mass of dry saturated steam to the total mass of wet steam containing

it. It is represented by ‘x’. Dryness fraction, x = mass of dry steam/ total

mass of wet steam.

2. One kilogram of steam at 1400 kPa has a total enthalpy

content of 2202.09 kJ. Determine the dryness fraction of the

steam.

From steam table, P=1400 kPa

hf = 829.96 kJ/kg

hfg = 1958.9 kJ/kg

X = dryness fraction

Actual total enthalpy =hf + hfg (X)

2202.09 kJ = 829.96 kJ/kg+1958.9 kJ/kg (X)

X = 0.70046

3. A calorimeter with heat capacity equivalent to having 13.3

moles of water is used to measure the heat of combustion

from 0.303 g of sugar (C12H22O11). The temperature

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increase was found to be 5.0 K. Calculate the heat released,

the amount of heat released by 1.0 g, and 1.0 mole of sugar.

Heat capacity of the calorimeter, C = 75.2 J/K∙mol

Heat released under constant volume, qv

qv = C x dT,

= 13.3 mol x 75.2 J/(K ∙mol) x 5.0 K

= 5000 J

The amount of heat released by 1.0 g

= 5000 J/0.303 g = 16.5 kJ / g

Since the molecular weight of sugar is 342.3 g/mol,

The amount of heat released by 1.0 mole

= 16.5 kJ / g x 342.3 g/mol = 5648 kJ/mol.

10.0CONCLUSION

It can be concluded that the experiment was successful and the dryness

fraction of the steam was found using the readings found to be 0.9085 which

then showed us that the steam state is considered wet and the experiment

also showed that the theory is proven on counting the dryness fraction of the

steam. Performance analysis on separating & throttling calorimeter was

carried out. The following parameters were measured: Steam Temperature,

Steam Pressure, Exhaust Gas Temperature, Fuel Pressure, and Water

Temperature after Economizer at various conditions. Dryness fraction of steam

was calculated. The following conclusions were drawn under various

parameters like boiler steam temperature; boiler steam pressure; steam

pressure before throttling; Steam pressure after throttling; steam temperature

after throttling; steam flow rate measured. Water particles from wet steam can

fully seperated , thus resulting in precise value. The actual Dryness fraction of

steam calculated.Boiler efficiency improved by 10 %.

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11.0SUGGESTIONS AND RECOMMENDATIONS

The equipment in the lab should be either replaced or maintained in order to

get more accurate readings. The students should be given the opportunity to

record more than one value per reading so a mean can be obtained or so that

there can be more certainty for each reading.

Maintenance in the laboratory apparatus for the dryness fraction lab

conduction should be done before students are allowed to go and do the

experiments. This is due to varying data or reading that student get when

conducting the labs as that would make lecturers to mark the laboratory work

easier. That could also constitute to the improvement on the efficiency of the

set of apparatus as seen above calibration.

12.0REFERENCE

1. Separating and Throttling Calorimeter. Retrieved from sakshat virtual lab:

http://iitg.vlab.co.in/?sub=58&brch=160&sim=1603&cnt=1

(Assessed on 28/11/2014).

2. Lab manual thermodynamics. Retrieved from: http://jnec.org/Lab-

manuals/MECh/SE/SE-ET%20Lab%20Manual1.pdf.

(Assessed on 28/11/2014).

3. J.M. Smith. Introduction to Chemical Engineering Thermodynamic seventh

edition. Mc Graw Hill Companies Inc. ISBN 0-07-310445-0. (2005).

4. Kevin Dahm, Donald Visco. Fundamentals of Chemical Engineering

Thermodynamics SI Edition. Cengage Learning. ISBN

9781305178168. (2014).

5. Onkar Singh. Applied Thermodynamics Third Edition. New Age International

(P) Ltd. Publishers. ISBN 9788122429169. (2009).

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Prepared by/Disediakan oleh :

Signature/Tandatangan : Name/Nama : DR. NADIRUL HASRAF BIN MAT

NAYAN

Date/Tarikh :

Name/Nama : PROF. MADYA DR. ANGZZAS SARI BINTI MOHD KASSIM

Date/ Tarikh :

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Documents

Exp 4 - Separating and Throttling Calorimeter