Exp 4 - Separating and Throttling Calorimeter
FACULTY OF ENGINEERING TECHNOLOGY DEPARTMENT OF CHEMICAL ENGINEERING TECHNOLOGY
CHEMICAL ENGINEERING THERMODYNAMICS LABORATORY LABORATORY INSTRUCTION SHEETS COURSE CODE
SEPARATING AND THROTTLING CALORIMETER
DATE GROUP NO. 1) DR. NADIRUL HASRAF BIN MAT NAYAN LECTURER/ INSTRUCTOR/ TUTOR
2) PUAN AZIAH BT ABU SAMAH
DATE OF REPORT SUBMISSION
DISTRIBUTION OF MARKS FOR LABORATORY REPORT
RESULTS & CALCULATIONS
ANALYSIS DISCUSSIONS: ADDITIONAL QUESTIONS: CONCLUSION:
/15% /20% /15% /10%
SUGGESTION & RECOMENDATIONS
RECEIVED DATE AND STAMP
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 Name : Matrix No. :
__________________________________________(Signature) _____Yeu Ho Kiet__________________ _____AN140177___________________
2) Group Member 1 Name : Matrix No :
__________________________________________(Signature) ____Kogulan a/l Subramaniam_____ ____DN140115_____________________
3) Group Member 2 Name : Matrix No. :
__________________________________________(Signature) _____Jaayshini a/p Murugiah_____ _____AN140023___________________
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.
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;
then the dryness fraction as measured by the separating calorimeter (X s)
Throttling calorimeter Consider a fluid flowing through a throttling orifice from higher pressure P 1 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;
= 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
= specific enthalpy of saturated vapour corresponding to pressure P2 = specific heat at constant pressure
= steam temperature at throttling calorimeter = saturated steam temperature corresponding to pressure P 2
Since H1 = H2,
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
But w = Wt (1 – Xt)
From equation (1), Therefore: True dryness fraction, X = XS x Xt
Figure 1: Cusson P7660 Separating and throttling calorimeter
Figure 2: The equipment panel mounted on a freestanding framework
5.0 PROCEDURE 1. 2.
Cooling water flow through condenser is started. Condensate collecting vessel is placed under the condenser
Small valve on throttling calorimeter is closed to isolate the manometer.
The steam valve is opened and the steam is allowed to flow through the condenser is sufficient to condense all the steam.
When condition have stabilised, the valve to the manometer is opened.
The separated condensate level is allowed to build up in the separating calorimeter until liquid can been in the calorimeter condensate level tube.
The condensate-collecting vessel is drained.
The main condensate-collecting vessel is refitted under the condenser outlet.
a) b) c) d) e) f) g)
Measure and record; Initial value of fluid level in the separating calorimeter. Initial value of condense level in the main condensate-collecting vessel. The steam pressure in the steam main. The steam pressure after throttling. Steam main steam temperature. Temperature in the throttling calorimeter. 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.
The separating calorimeter is drained.
The condensate-collecting vessel is emptied.
6.0 RESULTS & CALCULATIONS
Results. Table 5.1 Observed readings
Parameters Barometric pressure, bar.abs Separator: Steam pressure, bar.abs
Throttle: Steam pressure, mm.Hg, bar abs Trottle: Difference in mercury level due to water, mm.Hg Separator: Steam temperature, oC
Throttle: Steam temperature, oC Separator: Amount of collected water, mL Throttle : Amount of condensed water, mL
Table 5.2: Derived results
Parameters Throttle: Specific heat at constant pressure, kJ/kgK Separator: Steam pressure, bar.abs Throttle: Steam pressure, bar.abs Separator: Saturated liquid enthalpy, kJ/kg Separator: Latent heat, kJ/kg Throttle: Vapour Enthalpy, kJ/kg Throttle: Saturated steam temperature, oC Separator: Dryness fraction of steam, XS
Average 1.907 4.346 1.0192 617.45 2124.33 2675.83 100.12 0.9286
Throttle: Dryness fraction of steam, Xt Steam Line: Dryness fraction, X 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 = 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: 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
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.
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.
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 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 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 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. 10.0 CONCLUSION 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 %.
11.0 SUGGESTIONS 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. 12.0 REFERENCE 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). manual thermodynamics. Retrieved from: http://jnec.org/Labmanuals/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).
Prepared by/Disediakan oleh :
Approved by/Disahkan oleh :
Signature/Tandatangan : Name/Nama : DR. NADIRUL HASRAF BIN MAT NAYAN
Signature/Tandatangan : Name/Nama : PROF. MADYA DR. ANGZZAS SARI BINTI MOHD KASSIM
Date/ Tarikh :