Mass And Energy Balances Over Oil Fired Boiler Engineering Essay

In technology industry, boilers play an of import function. They are widely used to bring forth steam with a force per unit area above the atmospheric force per unit area ; the steam produced is used in assorted procedures, largely in heating applications such as a heat beginning in heat money changers. There are many different types of boilers which are used in different applications. One type of boilers is the Oil-fired steam boilers, by and large known as steam generators, are the most common vaporisers. These boilers use natural oil as the fuel ; fire it and utilize the heat to boil the H2O. The merchandise is steam at high force per unit area and flue gases.

This experiment involves the usage of an oil-fired boiler in the Mechanical Engineering Department in order to bring forth about 1.4 MW of heating steam when 200 l/hr of oil is combusted. A vacuity capacitor is used to distill the produced steam to H2O at temperatures about 10A°C above ambient.

Measurements of temperatures, force per unit areas and other relevant parametric quantities were recorded and averaged in the Appendix Section AIII ( Recorded Data ) . Mass and energy balance was performed utilizing those informations. When making the computations in this experiment, the uncertainness for a scope of information was obtained by the assurance the 95 % assurance bound. When ciphering mistakes, the mistake extension regulations were used. The manner uncertainnesss were calculated in this experiment is explained in more item in the Appendix.

Purpose:

The chief aim of this experiment is to execute mass and energy balances over the oil-fired boiler and vacuity capacitor. In add-on, the thermic efficiency of the boiler when operating at steady province was to be obtained. This experiment involves a big sum of informations ; hence, the experience gained when managing and pull strings such big sum of information is sought.

Premises

Several premises had to be made in order to carry on the experiment.

The oil fired boiler, the vacuity capacitor, the ouster and all the constituents in the works are assumed to be at steady province. This means that all temperatures, flow rates and force per unit areas are changeless with clip.

The ideal gas jurisprudence applies to the fluke gas. This premise seems sensible because the fluke gas has moderately high temperatures and a partial force per unit area of less than one ambiance, the premise is right to more than 1 % mistake.

For the burning stoichiometry, it is assumed that complete burning occurs for the oil in the air.

In the flue gases analysis on dry footing the Micro GC setup was used which can non analyze for the water-vapour nowadays, merely O2 and CO2 is detected and the staying volume is assumed to be N2.

The air come ining the boiler is assumed to be 20.93 % O2, 70.94 % N2, and 0.03 % CO2.

The steam that comes out of the boiler at the boiler gage force per unit area is dry and saturated ( all vapor, non partly condensed ) .

The air around the boiler, the vacuity capacitor and the pipe works is assumed to be dead.

The given values for the heat transportation coefficient have an uncertainness of up to 20 % .

All values of invariables ( i.e. specific heat capacity, GCV ) given correspond to the conditions during the twenty-four hours of the experiment.

Theory

The theory is adapted from the Boiler Heat and Mass Balance press release ( ENCH 271 home page ) .

Mass Balance

( Footing: 1 second )

Steam side

Boiler

From the preservation of mass expression of a procedure, it is clear that the mass of H2O fed into the boiler is peers to the mass of H2O out as a condensate.

General balance expression for the boiler:

Accumulation = In-Out+Generation-Consumption

Mass of H2O into boiler = mass of H2O out as condensate

The sum of condensate collected can be compared with the feed H2O rate and the disagreement noted.

Steam Ouster

A certain sum of steam is drawn off before the capacitor to provide the ouster with watercourse. This is to bring forth vacuity for the capacitor. This sum is calculated to be found:

M=0.017A±0.001 kg/s

Combustion side

Flue Gas Flowrate

Following the premise that burning gasses act as ideal gases, the ideal gas jurisprudence of perfect gas jurisprudence can be used. Because the fluke gas is at comparatively high temperature and partial force per unit area less than one ambiance, the premise is right to more than 1 % mistake. Mass of the fluke gas is calculated from its composing and mass flow rate of the oil burned.

Overall Balance

For the overall mass balance on the burning side, the sum of air come ining the boiler needs to be calculated from the fluke gas analysis and the oil provender rate.

mass of wet air in + mass of oil in = mass of wet fluke gas out

The disagreement is noted between the two values as good, utilizing the fluke gas flow rate obtained from the fluke gas analysis.

Water content of Flue Gas

The H2O in the fluke gas arises from two beginnings: H2O vapor in the recess air, and H2O formed during the burning of H2 in the oil.

Water in the recess air can be calculated from the absolute humidness:

Yg, the absolute humidness, can be read off the Grosvoner chart ( Page 16 f the briefing sheet ) .

Therefore,

mass of wet air in = ( 1 + Yg ) x mass of dry air

Water coming from the burning of H2 can be calculated from stoichiometry.

Conversion of Gas Analysis to Weight Basis

The followers can be obtained from the burning stoichiometry and the weight of oil used footing:

The weights of C, H, and sulfur into the system.

The minimal kmol of dry air needed to fire the C, H and sulfur into CO2, H2O and SO2.

The kmol of dry air in surplus of stoichiometric which were used in the burning procedure.

From above, the weights of CO2, H2O, SO2, N2, and O2 in the fluke gas can be calculated. In add-on, if the gas fuel analyses are right, the ratio of CO2 and O2 in the fluke gas measured should match to the 1 calculated by stoichiometry.

Condenser and Ejector Cooling Water Flow

The force per unit area bead across the opening home base was measured utilizing a differential force per unit area gage and the flow rate was so calculated from the orifice equation:

where:

W = flow rate of H2O [ kg/s ]

Cadmium = discharge coefficient ( = 0.6 )

So = country of opening [ M2 ]

rw = H2O denseness [ kg/m3 ]

rHg = quicksilver denseness [ kg/m3 ]

g = acceleration due to gravitation [ m/s2 ]

H = tallness of quicksilver in manometer [ m ]

Make = opening diameter ( = 0.0402 m )

D = pipe diameter ( = 0.078 m )

Energy Balances ( Footing: 1 second )

Reference Basis for Heat Flows

For heat flows on the burning side, it is convenient to take the air inlet temperature as the mention footing.

Heat Supplied to the Boiler

Heat supplied to the boiler:

Heat supplied = weight of oil in x gross calorific value of oil

The undermentioned corrections must be applied:

2455kJ/kg must be subtracted from the CV value. This is because the CV value is measured at 25°C at changeless volume. All H2O formed during the burning is condensed ; therefore the heat used to vaporize the H2O produced at the mention temperature must be subtracted.

Qcorrection1 = mwater, burning ten 2455

A rectification for non-combustion of CO is calculated from the heat content of reaction of CO to organize CO2 at the mention temperature.

Qcorrection2 = mCO x I”H

There is an added measure of heat put into the boiler because the recess oil temperature is above the mention temperature:

Qcorrection3 = moil x Cp, oil ( Toil, in – Treference )

where:

Cp, oil = 1.95 kJ/kg K. This value is added to the heat of burning.

Heat Balance over the Boiler

The heat of provender H2O to bring forth steam is given by the undermentioned equation

The heat content informations can be obtained from steam tabular arraies.

The heat lost in the flue gasses is given by:

where:

M = mass of wet fluke gas [ kg/s ]

= leaden norm specific heat of the fluke gas =1.07 kJ/kg K

Tgas = fluke gas temperature at the dorsum of the boiler [ K ] .

Heat is lost up the fluke because the gases are considerable hotter than the mention recess temperature.

The losingss from the boiler surface are calculated from:

Where H = hc + hour = combined heat transportation coefficient for the convection and the radiation losingss from the surface. For the platework take H = 15 W/m2 K and for a lagged surface take H = 12 W/m2 K. Assume H is right within A± 20 % .

The overall energy balance for the boiler is performed, and disagreement noted.

Losingss from Pipework to Condenser

The heat loss through organ pipe between the boiler and capacitor is given by:

where:

A: is the surface country of the pipe [ M2 ]

H: is the combined heat transportation for convection and the radiation losingss from the surface, which is hc + H r= 12 W/m2 K.

Condition of Steam at Engine Room Header

Enthalpy of steam can be calculated from

where:

Hg, boiler is the heat content of steam as it leaves the boiler [ kJ/kg ] .

Ql is the entire losingss in the pipe work, boiler and engine room heading [ kJ/kg ] .

The status of the steam can be determined utilizing the heat content and force per unit area of the steam:

If Hg & gt ; ( Hg, sat at P ) so the steam is superheated. Amount of superheat can be determined from steam tabular arraies.

If Hg = ( Hg, sat at P ) so the steam is dry and saturated and the waterlessness fraction x=1

If Hg & lt ; ( Hg, sat at P ) so the steam is wet.

The waterlessness fraction ten can be calculated from

where:

Hafnium: is the heat content of concentrated liquid at force per unit area P [ kJ/kg ] .

hence:

where:

Hf, g is the latent heat of vaporization at force per unit area P [ kJ/kg ] .

Energy Balance for Vacuum Condenser and Steam Ejector

Heat loss from the piping between the engine room heading and the capacitor can be calculated. Enthalpy of recess steam to condenser ( Hg ) can so be obtained.

Heat removed from the steam to organize H2O at the distilling force per unit area from the capacitor and so subcool the H2O is:

where:

m = steam flow rate to the capacitor [ kg/s ]

Hf = heat content of the condensate [ kJ/kg ]

Hg= heat content of the recess steam to the capacitor [ kJ/kg ] .

A similar expression is used to cipher the heat removed from the steam due to ejector provender pipe surface losingss. However, the Hg value for this steam will be different from that come ining the vacuity capacitor.

The heat removed in the cooling H2O of the capacitor and ouster is given by:

where:

mw = chilling H2O flow rate [ kg/s ]

Cp = specific heat of H2O = 4.183 kJ/kg K

Tout and Tinlet are given by readings off dial gages [ K ]

The heat lost from the outside shell of the capacitor can be calculated as for the boiler surfaces.

The Overall balance for capacitor and ouster is calculated and disagreement noted:

Overall Energy Balance on Water and Steam

The heat out in the condensate based on the provender H2O temperature as the mention is given as:

where:

megahertz = condensate flow [ kg/s ]

Cp = specific heat of condensate = 4.187 kJ/kg K

The overall balance is performed, and the disagreement is noted:

Overall Steam-Raising Efficiency

The efficiency of the boiler can be obtained utilizing:

3.0 Experimental Procedures

Adapted from Boiler Heat and Mass Balance Lab Manual Pages 1 & A ; 12-16

Plant and Apparatus

The works consists of two major points. The first and chief portion of the works is a boiler that is capable of bring forthing 1.4MW of heat in the signifier of steam and devouring 200L/hr of oil. The 2nd portion is a vacuity capacitor which is used to distill the steam produced by the boiler to H2O at temperatures 10°C above the ambient ( or environing temperature ) . The agreement of the Plant is shown in the figure below.

The boiler is an oil-fired steam boiler which has three base on ballss on the burning side. It consists of a spinning cup oil provender to spray oil into the burning chamber, the ignition system which lights up the provender oil and the re- circulation H2O system. Figure 3.2 shows it ‘s three base on ballss:

The vacuity capacitor is merely a multi-pass heat exchanged runing under vacuity. The steam is condensed on the exterior of the tubings and the chilling H2O has six “ base on ballss ” on the tube side. The vacuity is maintained by a steam ouster restricting steam from about 11 bars to 1 saloon. The ouster is a two diverging-converging noses in a series and requires about a flow rate of 60kg/hr of steam to keep vacuity. The figure bellows shows the vacuity capacitor:

The works operates one time fuel and H2O are fed to the boiler. The fuel is burned with air in a burning chamber or “ fire tubing ” . The hot burning gases exchange heat with the H2O along the “ boiler base on ballss ” and are taken to atmosphere through the “ stack ” or chimney. The steam formed base on ballss along the steam lines to the capacitor where it exchanges heat with the cold H2O in the “ cold H2O base on ballss ” of the capacitor. The country and temperature of theses base on ballss is sufficient to chill the steam to approach ambient and the steam ouster prevents the accretion of any lasting gases in the system. Figure 3.4 below shows a representation of the works operation.

Measurements

The system was started up by the demonstrators and put up to keep a steady province every bit much as possible. There were seven measuring Stationss where those measurings were taken by nine groups of pupils who circulated around these Stationss. Each group took the same measurings and the values were recorded and averaged as shown in the Appendix Section ( A.III ) . Recorded Data. The measurings made in each Stationss were tabulated and are shown in the Appendix subdivision ( A.I ) .

3.2.1 Flow rate measurings

Boiler provender H2O flow rate

It was noted that the flow of feed H2O to the boiler is cyclic. During one period, the pump is refilling the H2O degree in the boiler while at the same clip the H2O is boiled away to organize steam. The pump is off in the other period.

The pump is activated by a degree detector. The flow of feed H2O to the boiler was timed over a complete rhythm which included both periods.

The two feed H2O armored combat vehicles were calibrated in gallons which was converted to S.I units by cognizing the denseness of H2O at recess temperature. Initial reading of the armored combat vehicle was recorded and merely as the pump started whizzing, stop watch was started every bit good. After the pump finished providing provender H2O, the concluding degree of the H2O was recorded. The stop watch was non stopped until the pump started once more since that is the clip needed for a complete rhythm. The clip was noted down in order to obtain the flow rate.

Oil flow rate

Barrel of oil was weighed utilizing a platform balance. Puting a weight of 4.5 kilograms on the counter balance and the clip needed for the graduated table to imbalanced, i.e. tipped, was recorded. This was the clip needed for ingestion of 4.5 kilogram of oil.

Condensate flow rate

The condensate was collected in a pail for one minute. The pail was so weighed on an electronic balance.

Flue Gas flow rate

The flow gas flow rate is determined from the fluke gas analysis and the oil provender rate as these two sets of informations are determined accurately.

Steam ouster flow rate

Previous trials were done prior to the experiment by the Mechanical Engineering Department and it was shown that the flow rate needed to keep a full vacuity in the capacitor was 0.017A±0.001 kg/s.

Condenser and Ejector chilling H2O flow rate

An opening home base was used to mensurate the entire chilling H2O flow rate. The force per unit area bead across the opening home base was measured utilizing a differential force per unit area gage and the flow rate can be calculated utilizing the orifice equation ( mention to Theory subdivision for the expression ) .

3.2.2 Temperature Measurements

Feed H2O

Temperature of H2O was measured in the provender armored combat vehicle by a quicksilver thermometer. Temperature measurings were done right after clip for a rhythm was recorded.

Air

The air temperature in forepart of the boiler was measured and the humidness of air was estimated utilizing a gyration hygrometer.

The hygrometer consists of a dry bulb and moisture bulb thermometer. First, the hygrometer was twirled in forepart ( or near to ) the boiler for about one minute to let the solution in the moisture bulb to vaporize. Then, the temperatures of both bulbs were recorded. The humidness was obtained from a Grosvener chart 17 of the briefing sheet [ 3 ]

Oil

The oil temperature was obtained by reading the temperature gage on the oil provender system after the flow rate measurings was completed.

Boiler surfaces

The temperatures of the boiler surfaces were measured utilizing a copper-constantan thermocouple at countries indicated in the figure below.

Front of the boiler Back and side of the boiler

Figure 3.6: Boiler surface temperature measurings

Note that ambient temperature around each surface was taken was good.

Shrieking Surface and Condenser Surface

For the piping system temperatures at the surfaces of the boiler mercantile establishment, boiler room heading, engine room heading, engine room provender, condensate and ouster provender, condenser provender, ouster provender and condensate line were recorded utilizing the same copper-constantan thermocouple. The temperature at the surface of the vacuity condensate was taken every bit good. Note that ambient temperature around each surface was taken was good.

Flue Gas

The temperature of the fluke gas was measured utilizing the quicksilver thermometer at the dorsum of the boiler.

Condenser Cooling Water

The recess and mercantile establishment temperatures of the capacitor chilling H2O were read off the gages on the control panel of the capacitor. The temperature of the combined flow of the ouster and capacitor chilling H2O was measured with a thermometer downstream of the opening home base.

3.2.3 Composition Measurements

Oil Composition

Analysis of the fuel prior to the experiment shows that the composing is

Carbon 85.9 %

Hydrogen 12.5 % Sulphur 1.6 %

Incombustibles ( Inert ) –

( All measurings in weight per centums )

Oil Calorific Value

Previous measurings show that the gross calorific value for the fuel oil is 43.6MJ/kg at 25°C.

Flue Gas

The sum of CO2, CO and O2 in the fluke gas was measured utilizing Micro GC setup on a dry footing. It was noted that the staying volume analysed is to be assumed to be all N2. The SO2 and SO3 content was measured utilizing a Drager tubing. The sum of H2O can be worked out utilizing flue gas stoichiometry. Checks were made on the CO content utilizing the Drager tubing.

Steam

The steam was assumed to be dry and saturated at the boiler gage force per unit area as it leaves the boiler. To guarantee that the premise holds throughout the experiment, cheques were done by look intoing the gages on the boiler, the boiler room heading and the Engine Room heading. The recess steam force per unit area to the steam ouster was besides noted down.

Equipment

The undermentioned instruments were used by the groups when taking measurings of temperature, force per unit area, mass and clip in the works:

Ear protection muffs.

Stop ticker with declaration of 0.01s.

Platform balance with a declaration of 0.005g.

Electronic mass balance with declaration of 0.01Kg for mensurating the mass of condensate over period of clip.

Orifice home base to mensurate the entire chilling H2O flow.

Mercury thermometer.

Twirling hygrometer for gauging the humidness of air ( utilizing a crossover chart ) .

Copper Eureka thermocouple with declaration of 0.1A°C.

Boiler force per unit area gages.

Micro GC setup for fuel gas analysis.

Drager tubings for sensing of CO content volume analysis.

Consequences

The uncertainnesss values are obtained utilizing the 95 % assurance bound method for more than 5 informations points. On the other manus, half scope method was used for less than 5 informations points. Further elaborate computations and uncertainness analysis are done in the Appendix.

Mass Balance

Steam Side

Performing a mass balance over the boiler, the boiler provender H2O and the condensate flow rates are calculated. The disagreement is found to be:

Boiler H2O provender rate

=

0.24

0.03

kg/s

condensate flow rate

=

0.25

0.01

Kg/s

Discrepancy

=

3

%

Combustion Side

Flue Gas Rate

The fluke gas is calculated from its composing and the mass-flowrate of the oil burned by using perfect gas Torahs and the followers is found:

Flue Gas flow rate from Flue Gas Analysis = 0.4 A± 0.01 kg/s

Overall Balance

Table ( 1 ) : Overall mass balance

Mass of wet air

0.372

0.0084

kg/s

kg/s

kg/s

Mass of

moisture fluke

gas out

0.4

0.01

Mass of Oil in

0.0208

0.0007

Entire mass in

0.419

0.04

Discrepancy between Inputs and Outputs

0.06

%

Water Content of Flue Gas

Water in the Inlet Air

Absolute Humidity of Air = 0.007 A±0.0004 kg/kg

Mass flow of Dry Air = 0.36 A± 0.008 kg/s

Mass flow of Wet Air = 0.37A± 0.008 kg/s

Therefore,

Water in Inlet Air = 0.003 A± 0.0006 kg/s

Conversion of Gas Analysis to Weight Basis and excess Air analysis

The weights of Carbon, Hydrogen and Sulphur given to the boiler by the provender oil were calculated and the consequences are shown in the Appendix subdivision ( B ) . The needed air is calculated from the stoichiometry utilizing the composing and flow rate of the oil. The extra air is calculated from the stoichiometry utilizing the composing of CO2 in the fluke gas from Micro GC analysis. The surplus is besides calculated as the difference between the O required and the O provided harmonizing to the mass balance and the per centum of extra air found to be 20 % . All the informations obtained in order predating the composing of fluke gas composing are found in the Appendix subdivision ( B )

Table ( 2 ) : Flue gas Composition.

Composition

Amount moisture

A

Mass moisture

A

A

kmol

Uncertainty

kilogram

Uncertainty

O2

0.0005

0.0001

0.02

0.0041

N2

0.0101

0.0003

0.28

0.0080

Carbon dioxide

0.0015

0.0001

0.07

0.0023

Water

0.0014

0.0001

0.03

0.0017

SO2

0.000010

0.0000004

0.0007

0.00002

Entire

0.0136

0.0003

0.4

0.01

To look into if the fuel analysis was right, the ratio of CO2 to O2 in the fluke gas measured was compared to the 1 calculated by stoichiometry as shown in the tabular array below:

Table ( 3 ) : Comparsion between CO2/O2ratio

A

Micro GC

Stochiometry

Carbon dioxide

12.36

2.00

12.30

0.42

O2

5.26

2.00

4.34

1.06

Ratio ( CO2/O2 )

2.35

0.97

2.84

0.70

Discrepancy

A

20.8

%

A

A

A

Energy Balance

All elaborate computations are shown in the Appendix Section ( C ) .

Reference Basis for Heat Flows

Reference footing for heat flow is the air inlet temperature = 17.6 A± 0.7 A°C

Heat Supplied to the Boiler

The heat supplied to the boiler is the heat that is produced by the burning of fuel ( burning heat ) . As stated in the theory subdivision, this value needed to be corrected. The corrected value found is:

Qcombustion = 849 A± 10 kilowatt

Heat Balance over the Boiler

The energy balance around the burning side of the boiler uses the energy available from burning, the energy required to bring forth the ascertained steam flow, the energy lost in the fluke gas and the energy lost from the boiler surfaces. These values are listed in Table ( 4 ) every bit good as the disagreement in the energy balance.

Variables

Valuess

Uncertainties

A

Unit of measurements

Qcorrected

849

10

kilowatt

Qsteam

656

79

kilowatt

Qflue gas

93

8

kilowatt

Qboiler surface

29

6

kilowatt

Discrepancy

8.4

%

A

A

Table ( 4 ) : Energy balance around the burning side

Losingss from Pipework to Condenser

The deliberate heat loss from the organ pipe surfaces to the ambiance

Qpipe work = 7A± 1 kilowatt

Condition of Steam at Engine Room Header

The heat content lost from the pipe work up to the engine room is found to be:

Hg, sat at the force per unit area =

2782

kJ/kg

Hg, engine room =

2766

kJ/kg

Since Hg, engine room & lt ; Hg, sat at steam force per unit area, so the steam is wet. By comparing the ensuing steam heat content to heat contents of concentrated steam and H2O at this point it is determined that the steam becomes wet during conveyance. Furthermore, the fraction of the waterlessness of steam is found 0.993A±0.2 dry.

Energy Balance for Vacuum Condenser and Steam Ejector

The energy balance around the capacitor and ouster was calculated utilizing the energy lost from the piping between the engine room heading and the capacitor, the heat removed from the steam and the heat removed due to ejector provender Catholic Pope surfaces losingss. These values are listed in the tabular array below every bit good as the disagreement in the energy balance.

Table ( 5 ) : Heat lost from shrieking between engine room heading and capacitor:

Variables

Valuess

Uncertainties

Unit of measurements

Q

598

24.1

kilowatt

Qejector

44.4

8.7

kilowatt

Qloss

1.87

0.38

kilowatt

LSH

644.2

25.66

kilowatt

Qw

492.88

0.4

kilowatt

Qshell

5.4

0.4

kilowatt

Rhesus factor

498.3

0.6

kilowatt

Discrepancy for overall balance

22.6

A

%

Overall Energy Balance on Water and Steam

Heat out in condensate, Qc= 1.4 A± 0.2 kilowatt

Overall Balance for H2O and steam:

LHS = Total heat supplied to the H2O to bring forth steam,

= Qfeed H2O = 656 A± 12kW

RHS = Heat out in condensate + Total heat lost form pipwork + Total energy lost in capacitor + Energy lost in steam ouster

= Qc + Qpipe work + Qs + Qejector = 651 A± 26kW

Therefore, the Discrepancy found to be = 2 %

Overall Steam-Raisin Efficiency

Table ( 7 ) : Overall steam-Raising Efficiency

Variables

Valuess

Uncertainties

A

Unit of measurements

A

A

Qcombustion

849

10

kilowatt

1

%

Qfeed H2O

656

12

kilowatt

2

%

I-

77

3

kilowatt

2.2

%

Discussion

Expected Consequences

The values obtained in this experiment were moderately accurate with comparatively low uncertainnesss in general. That is because there were 9 sets of measurings taken, one for each group, in each measuring station. The uncertainnesss values were obtained by the 95 % assurance bound and half scope methods, so the mistakes reduced due to the more measurings made.

The Overall Steam Raising Efficiency is expected to be about 80 % harmonizing to the Briefing Sheet… However, this value is given when the flow rate of provender H2O to the boiler is about 0.3 kg/s. If the values calculated for this experiment for the flows were different, it is expected to acquire a different efficiency. Hence, we would anticipate the efficiency of the boiler to be moderately different than 80 % .

Mass Balance

It is clearly seen in Results Section 4.2. that the mass balance on the steam side was non achieved. The sum of provender H2O into the boiler was measured to be 0.240 A± 0.003 kg/s ( less than the expected 0.3 k/g ) while the condensate flow was measured to be 0.257 A± 0.01 kg/s. The two values showed a disagreement value of 3 % . The deliberate disagreement value found to be little and autumn within the experimental uncertainnesss of the two flow rates.

However, several factors can be attributed to the beginning of mistake occurred between the difference values obtained of each flow. One possibility is that the provender H2O to the boiler was non measured really accurately as desired since the flat index of the armored combat vehicle was fluctuating all the clip. This was due to feedback of H2O to the armored combat vehicle during the experiment since H2O furuncles and expands in the boiler. Therefore, the existent H2O degree in the provender armored combat vehicle had to be estimated. In add-on, parallax mistake when reading H2O degree has besides contributed to the disagreement.

The overall balance on the combustion-side showed really undistinguished disagreement of approximately 0.06 % . This disagreement was calculated utilizing the moisture fluke gas flow rate obtained from the fluke gas analysis. The low disagreement indicates that the premise that the fluke gas was considered to act as an ideal gas was valid as the experiment was conducted at comparatively high temperatures and partial force per unit areas less than one ambiance. It besides showed that the sum of wet air in the boiler calculated utilizing the burning stoichiometry and composing of air ( 20.93 % Oxygen, 79.04 % Nitrogen and 0.03 % Carbon Dioxide ) was moderately accurate.

Composition of flue gases was obtained and analysed in the experiment by utilizing Micro GC setup. Despite that, a fluke gas analysis utilizing burning stoichiometry was done as shown in Table 4.2 as a cross cheque for the gas and fuel analyses. Furthermore, by comparing the composings from each method, the ratio of CO2/O2 measured by the gas-fuel analyses agreed to the ratio obtained from stiochiometry within experimental uncertainnesss as shown in Table 4.3. This shows that the fuel- gas analysis was right and the oil composing given [ 3 ] was accurate. Most of the composings calculated besides agree within uncertainnesss values with those measured one ( see appendix ) with the exclusions of SO2 and CO. Therefore, presuming negligible sums of CO and SO2 in the fluke gas was valid premise since their measures detected by Micro GC analysis were really little ( in parts per million ) . The general understanding supports the cogency of the mass balance.

Furthermore, the premise that the system was at steady province was non valid in this experiment. This can be related to the fact that the flow rate of condensate or boiler provender H2O was fluctuating and was non changeless over clip. If more accurate consequences are to be obtained in this experiment, it would be suggested to hold the boiler running for long plenty until it becomes near to steady province in order to avoid any part of disagreements values of the steam side mass balance to the overall efficiency value of the system.

Energy Balance

The entire heat supplied to the boiler was 849 A± 10 kilowatt. This heat was corrected to account for energy that was already contained within the oil, energy lost in the vaporization of H2O produced in the burning and energy that was lost by uncomplete burning ( due to Carbon Monoxide, CO ) . Significantly, the energy that was lost by uncomplete burning could hold been assumed to be negligible as the mistake of the reply was less than the part that this energy loss had to the concluding corrected value.

The entire heat end products from the boiler gave a sum of 778 A± 79 kilowatt. This value included the heat required to bring forth steam, heat lost in flue gases and losingss from the boiler surfaces. The disagreement in the energy balance around the boiler was found to be 9 % . The disagreement was considered to be moderately high, and the input and end product values are wholly out of the scope of each other even within the experimental uncertainness.

There are a figure of possible grounds for the big disagreement value over the boiler balance. One possibility is that there must be some unaccounted heat loss from the boiler surface that was non considered in computations. The unaccounted energy is non likely to be from the heat loss in the surfaces of the boiler since the heat loss from the boiler surfaces gave merely a little part to the entire heat end product. It is possible that the unaccounted heat be due to some systematic mistakes when temperatures of the boiler surfaces were taken.

Another possibility was concluded to be comparative to the temperature measurings. Temperatures were taken utilizing copper-constantan thermocouples ; some of the temperatures could hold been recorded in a Fahrenheit alternatively of Celsius. The surface of the thermocouple was hard to keep level against some surfaces which caused a batch of fluctuation to the temperature being recorded and increased the disagreement. This was besides attributed to the fact that temperatures were measured merely 6 countries of the boiler, for a boiler of this size it is really impractical to take measurings in merely 6 countries. The unaccounted heat loss could be from some undetected heat losingss in other countries of the boiler. For illustration heat loss in the ticker door of the boiler, as it might hold non been as tightly closed as expected, or heat loss from the spread in the door.

On the other manus, it is possible to hold accounted for all the heat losingss from the boiler surfaces and so the lone account for the imbalance of energy around the boiler could be attributed to heat accretion within the boiler. This is really feasible since the boiler was non precisely in a steady province status.

The ascertained fluctuation between the two force per unit area gages in both boiler room and the engine room heading was found to be comparatively little at merely 2 % disagreement as shown in Appendix ( Table ( C.12 ) ) . The heat loss over the organ pipe from the boiler to the engine room contributed to most of the force per unit area bead. The alteration in heat content has besides contributed for this force per unit area bead. In add-on, harmonizing to Bernoulli ‘s equation, the pipe adjustments ( such as cubituss T ‘s ) alter the force per unit area inside the pipes.

By ciphering the heat content lost from the organ pipe up to the engine room and comparing the ensuing steam heat content to heat contents of concentrated steam and H2O at this point it was determined that the steam that comes out of the boiler was found to be partly wet with a dryness fraction of about 0.992A±0.2. Therefore, the premise made earlier that the steam from the boiler was wholly dry is incorrect as it was found to be approximately 2 % moisture. This could impact the heat contents used in farther computations and therefore affected the heat balances.

The energy balance for vacuity capacitor and steam ouster was performed and the disagreement was found to be 22 % . This value of disagreement is comparatively unreasonable ; as the disagreement likely arises from the heat loss by the steam where the steam was assumed to be wholly dry although it was 2 % moisture. The other major part to the beginning of mistake of this value was attributed one time once more to the uncertainness values involved when taking the temperature measurings utilizing the thermocouple.

Performing the overall energy balance on H2O and steam for the whole system gave a disagreement of 2 % A±0.5 % between input and end product values. The end product heat of the system, which is heat out in the condensate, heat lost from organ pipe, entire energy lost in capacitor and energy lost in steam ouster, was 651A± 26 kilowatt while the heat that was supplied to the system ( heat from feed H2O ) was 656A± 12 kilowatt. This shows that a comparatively little sum less energy was used to bring forth the steam than it was calculated in the surpassing energy flows. The low disagreement makes the deliberate efficiency more dependable. The mistake on the disagreement was reasonably big and the major subscribers are one time once more related to the fact that the system was non at steady province when the measurings were conducted or that there were some unaccounted heat losingss.

Finally the overall steam-raisin efficiency of the boiler was calculated and found to be 77 % with an uncertainness value of A±2.2 % . This is about within the expected value of 80 % that is indicated in the lab briefing sheet. The uncertainness on the steam raising efficiency is low plenty to do it a good estimation. The boiler had less uptake of provender H2O than expected earlier on and this can impact the efficiency. This can besides be related to the status of the boiler in the Mechanical Engineering Department since it has been runing since 1960s. In add-on, the lower efficiency might be resulted by the disagreements in the heat balances performed earlier and the system non being in steady province.

Dependability and Premises

Of the premise made, the premise that the system was at steady province was shown to be invalid one time once more when executing energy balances for different parts in the works. Energy balances were non achieved and the mensural temperatures varied over clip. The premise of holding the changeless values matching to the conditions of the twenty-four hours was comparatively invalid every bit good. The premise of ideal gases appears valid within the truths of the experiment. The premise that N is inert appears right as does the premise of no accretion and merely water/steam in the water/steam system. Furthermore, there is nevertheless grounds that the premise that the steam is saturated when it leaves the boiler is invalid and farther probe is required to look into.

In order to obtain better consequences following clip, it would be advised to guarantee the right constellation of the thermocouples before utilizing them. Besides it would be extremely recommended that temperatures be measured for more than 6 surfaces of the boiler to give a better estimation of heat losingss from the boiler. The demand belongingss for the experiment should be really looked up at the conditions of the twenty-four hours that the experiment is conducted. Furthermore, the major parts to the beginning of mistake related to the overall steam-raising efficiency value are traced back to the condensate and oil mass flow rates. A more accurate efficiency will be given if the flow rates of condensate and oil are determined with less uncertainness.

Decisions

Throughout the experiment, the boiler was defined as a device that is used to bring forth steam with a force per unit area above the atmospheric force per unit area. This experiment was performed to find the overall steam-raising efficiency of the boiler in the Mechanical Engineering Department utilizing mass and energy balances. The experiment has besides investigated the influence of the premises made comparatively to the consequences obtained. These consequences illustrated several decisions which can be summarized by the followers

The sum of condensate collected was compared with the provender H2O and the disagreement found to be 3 % . The sum of provender H2O into the boiler was measured to be 0.240 A± 0.003 kg/s ( less than the expected 0.3 k/g ) while the condensate flow was measured to be 0.257 A± 0.01 kg/s.The disagreement in the mass balance was largely due to the inaccurate measuring of the provender H2O flow.

The fluke gas flow rate was measured from the fluke gas analysis and the oil provender rate, as these two sets of informations are determined accurately.

Mass balance on the combustion-side was achieved with an undistinguished disagreement of 0.06 % . The jurisprudence disagreement proved the premise that the fluke gas behaves as an ideal gas during the experiment to be valid.

The fluke gas analysis obtained from Micro GC analysis agreed with the one obtained from the burning stoichiometry. This was crossed checked by comparing the ratio of CO2/O2 from each method.

The disagreement ( 9 % ) for the energy balance around the boiler was rather high which was attributed to either an unaccounted heat loss in the boiler surface or an accretion of energy within the system.

The energy balance on the capacitor and ouster gave a disagreement of 22.6 % A± 3 % . The overall steam and H2O side energy balance gave a disagreement of 2 % which shows that a comparatively little sum less energy was used to bring forth the steam than it was calculated in the surpassing energy flows.

The energy balance around the capacitor and ouster and over the whole system was achieved with sensible disagreements.

By ciphering the heat content lost from the pipe workup to the engine room and comparing the ensuing steam heat content to heat contents of concentrated steam and H2O at this point it was determined that the steam become moisture during conveyance. A dryness factor of 0.992 A± 0.2 was found for steam at the engine room heading.

The system that was conducted for the experiment was non at steady province.

The efficiency of the boiler was found to be 77 % with an uncertainness of A± 3 % . This was lower than the expected value due to many grounds affecting the status of the boiler and factors in the experiment itself. However, The uncertainness on the steam raising efficiency was low plenty to do it a good estimation

Overall the experiment was really successful in accomplishing the needed aims and purposes. The overall steam-raising efficiency of an oil-fired boiler was obtained. The information collected in the experiment was successfully used to execute heat and mass balances over the oil-fired boiler and vacuity capacitor. Some of the balances performed had rather a big disagreement which was attributed to the premise of steady province status non keeping for the experiment.

Recommendations:

Furthermore, several suggestions were reached from the old observations and computations to better the design of the boiler experiment. The undermentioned points can sum up these suggestions:

A better method should be used to mensurate the sum of H2O fed to the boiler.

The thermocouples used to mensurate boiler surface temperatures should be calibrated and checked before each measuring.

The truth of temperature measurings could be improved by taking more measurings. To avoid any accounted heat losingss from the boiler surfaces more measurings should be taken of the boiler surface temperatures.

The demand belongingss for the experiment should be really looked up at the conditions of the twenty-four hours that the experiment is conducted.

An insularity bed for the boiler and pipe-working surfaces can be used to cut down the sum of countless heat losingss.