Lab manual mechanical engineering, Lab Reports of Mechanical Engineering

Download Lab manual mechanical engineering and more Lab Reports Mechanical Engineering in PDF only on Docsity!

LABORATORY MANUAL

THERMODYNAMICS-I

(ME-203)

DEPARTMENT OF MECHANICAL ENGINEERING

MGM’S

JAWAHARLAL NEHRU ENGINEERING COLLEGE

N-6, CIDCO, AURANGABAD-

Mission and vision of the Department

Vision of Mechanical Department To establish the state of the art learning center in Mechanical Engineering which will impart global competence, enterprising skills, professional attitude and human values in the student. Mission of Mechanical Department

1. To impart quality technical education to the students.
2. To develop comprehensive competence in the students through various modes of learning.
3. To enable students for higher studies and competitive examinations.
4. To facilitate students and industry professionals for continuous improvement and innovation.

Program Educational Objectives:

[1] Use core competence acquired in various areas of Mechanical Engineering to solve techno-managerial issues for creating innovative products that lead to better livelihoods & economy of resources. [2] To establish themselves as effective collaborators and innovators to address technical, managerial and social challenges. [3]To equip students for their professional development through lifelong learning and career advancement along with organizational growth. [4] Serve as a driving force for proactive change in industry, society and nation.

PROGRAM SPECIFIC OUTCOMES Student should have

1. An ability to work professionally in mechanical systems including design, analysis, production, measurement and quality control.

2. An ability to work on diverse disciplinary tasks including manufacturing, materials, thermal, automobile, robotics, mechatronics, engineering software tools, automation and computational fluid dynamics.

EXPERIMENT NO. 1

Study of determination of Calorific Value of Fuels by using different calorimeters

Aim: - A. To study determination of Calorific Value of Fuels by using Bomb calorimeter.

Apparatus: - Bomb Calorimeter

Theory:- The “calorific value or heating value” of the fuel is defined as the energy liberated by the complete oxidation of a unit mass or volume of a fuel. It is expressed in kJ/kg for solid and liquid fuels and kJ/m^3 for gases. The higher heating value, HHV, is obtained when the water formed by combustion is completely condensed. The lower heating value, LHV, is obtained when the water formed by combustion exists completely in the vapour phase. Bomb calorimeter: The calorific value of solid and liquid fuels is determined in the laboratory by ‘Bomb calorimeter’. It is so named because its shape resembles that of a bomb. Fig. 1 shows the schematic sketch of a bomb calorimeter. The calorimeter is made of austenitic steel which provides considerable resistance to corrosion and enables it to withstand high pressure. In the calorimeter is a strong cylindrical bomb in which combustion occurs. The bomb has two valves at the top. One supplies oxygen to the bomb and other releases the exhaust gases. A crucible in which a weighted quantity of fuel sample is burnt is arranged between the two electrodes as shown in Fig. 1. The calorimeter is fitted with water jacket which surrounds the bomb. To reduce the losses due to radiation, calorimeter is further provided with a jacket of water and air. A stirrer for keeping the temperature of water uniform and a thermometer to measure the temperature up to an accuracy of 0.001°C are fitted through the lid of the calorimeter.

Figure 1: Bomb calorimeter.

Procedure: To start with, about 1 gm of fuel sample is accurately weighed into the crucible and a fuse wire (whose weight is known) is stretched between the electrodes. It should be ensured that wire is in close contact with the fuel. To absorb the combustion products of sulphur and nitrogen 2 ml of water is poured in the bomb. Bomb is then supplied with pure oxygen through the valve to an amount of 25 atmosphere. The bomb is then placed in the weighed quantity of water, in the calorimeter. The stirring is started after making necessary electrical connections, and when the thermometer indicates a steady temperature fuel is fired and temperature readings are recorded after 1/2 minute intervals

hydrogen will, therefore, be condensed. The procedure of determining calorific values of liquid fuels is similar to that described above. However, if the liquid fuel sample is volatile, it is weighed in a glass bulb and broken in a tray just before the bomb is closed. In this way the loss of volatile constituents of fuels during weighing operation is prevented.

Aim: - B. To study determination of Calorific Value of Fuels by using Boys Gas calorimeter.

Apparatus: - Boys Gas Calorimeter

Theory:- This calorimeter is suitable for determination of calorific value of gaseous fuels. Figure 2 shows the components of the Boys gas calorimeter. It consists of a gas burner B with arrangement to measure flow quantity and pressure of the gas supplied to the burner. A gas pressure regulator is used in the gas supply line to damp down any pressure fluctuations which would affect the results adversely. The fuel supplied burns within a cylindrical container which is surrounded by a cooling coil from a constant head tank. The flue gas moves up in the cylindrical container and then it flows down from the top of the container as shows in the figure. The steam formed due to the combustion of hydrogen in the fuel and carried with the gases condenses around the cooling coil and drips down into the trap below as shown in the figure. The overflow of the condensate is taken out in a glass beaker as shown in the figure.

Figure 2: Boys gas calorimeter The outer casing of the calorimeter is provided with heavy insulation to prevent any heat loss to the surrounding: The following readings are taken during the test:

1. Time of run
2. Pressure and temperature of the gas supply

The equation (2) gives the H.C.V. of the fuel as the H 2 O vapour formed due to the burning of H 2 in fuel is condensed and collected. For finding L.C.V. the heat carried by H 2 O should be deducted from the H.C.V.

EXPERIMENT NO. 2

Determinations of exhaust gas analysis by using Orsat Apparatus

Aim: - Determination of exhaust gas analysis by using Orsat apparatus. Apparatus: - Orsat apparatus Theory:- The combustion products are mainly gaseous. When a sample is taken for analysis it is usually cooled down to a temperature which is below the saturation temperature of the steam present. The steam content is therefore not included in the analysis, which is then quoted as the analysis of the dry products. Since the products are gaseous, it is usual to quote the analysis by volume. An analysis which includes the steam in the exhaust is called a wet analysis. Practical analysis of combustion products: The most common means of analysis of the combustion products is the Orsat apparatus which is described below: Construction: An Orsat’s apparatus consists of the following: (i) A burette (ii) A gas cleaner (iii) Four absorption pipettes 1, 2, 3, 4. The pipettes are interconnected by means of a manifold fitted with cocks S1, S2, S3 and S4 and contain different chemicals to absorb carbon dioxide (CO 2 ), carbon monoxide (CO) and oxygen (O 2 ). Each pipette is also fitted with a number of small glass tubes which provide a greater amount of surface. These tubes are wetted by the absorbing agents and are exposed to the gas under analysis. The measuring burrette is surrounded by a water jacket to prevent, changes in temperature and density of the gas. The pipettes 1, 2, 3, 4 contain the following chemicals: Pipette 1: Contains ‘KOH’ (caustic soda) to absorb CO 2 (carbon dioxide) Pipette 2: Contains an alkaline solution of ‘pyrogallic acid’ to absorb O 2 (oxygen) Pipette 3, 4 : Contain an acid solution of ‘cuprous chloride’ to absorb CO (carbon monoxide) Furthermore the apparatus has a levelling bottle and a three way cock to connect the apparatus either to gases or to atmosphere.

The amount of nitrogen in the sample can be determined by subtracting from total volume of gas the sum of CO 2 , CO and O 2 contents. Orsat apparatus gives an analysis of the dry products of combustion. Steps may have been taken to remove the steam from the sample by condensing, but as the sample is collected over water it becomes saturated with water. The resulting analysis is nevertheless a true analysis of the dry products. This is because the volume readings are taken at a constant temperature and pressure, and the partial pressure of the vapour is constant. This means that the sum of the partial pressures of the remaining constituents is constant. The vapour then occupies the same proportion of the total volume at each measurement. Hence the vapour does not affect the result of the analysis.

RESULT: Hence we studied the Orsat apparatus for analysis of flue gases.

Note: Quantitatively the dry product analysis can be used to calculate A/F ratio. This method of obtaining the A/F ratio is not so reliable as direct measurement of air consumption and fuel consumption of the engine. More caution is required when analysing the products of consumption of a solid fuel since some of the products do not appear in the flue gases (e.g. ash and unburnt carbon). The residual solid must be analysed as well in order to determine the carbon content, if any. With an engine using petrol or diesel fuel the exhaust may include unburnt particles of carbon and this quantity will not appear in the analysis. The exhaust from internal combustion engines may contain also some CH 4 and H 2 due to incomplete combustion. Another piece of equipment called the Heldane apparatus measures the CH 4 content as well as CO 2 , O 2 and CO.

EXPERIMENT NO. 3

Determination of Dryness fraction by using different Calorimeters

Aim: - To determine dryness fraction of steam by using Separating throttling calorimeter

OBJECTIVE: The objective of this experiment is to study the determination of the dryness fraction of wet steam by using

1. Tank Calorimeter
2. Separating Calorimeter
3. Throttling Calorimeter
4. Separating and Throttling Calorimeter

THEORY : 1 Tank Calorimeter:

The dryness fraction of steam can be found with the help of tank calorimeter. A known mass of steam is passed through a known mass of water and steam is completely condensed. The heat lost by steam is equal to heat gained by the water.

Figure 1: Tank Calorimeter

NOTE:- As the losses due to convection and radiation are not taken into account, the dryness fraction determined involves some inaccuracy. The calculated value of dryness fraction neglecting losses is always less than the actual value of the dryness.

2 Separating Calorimeter This calorimeter is used to measure the probable value of dryness fraction of steam when the steam is very wet. The arrangement of the calorimeter is shown in figure. The steam is passed through a sample tube as shown in the figure. The moisture is separated mechanically from the steam. The steam is passed through perforated trays and water partials are separated due to inertia of the droplets. The outgoing steam is condensed in the bucket calorimeter.

Figure 2: Separating Calorimeter mw= mass of water separated from the steam ms= mass of steam condensed in the bucket calorimeter which can be calculated by the difference in mass of the bucket calorimeter before and after mixing the steam. X= dryness fraction of steam. Therefore,

∴ s

s w

m x m m

=

In calculating the dryness fraction of steam by this method it is assumed that all the water partials are removed in the separating section and the steam entering in the bucket calorimeter is completely dry. NOTE:- In practice, it is not possible to remove all the water particles from the steam by this mechanical process and, therefore, the dryness fraction obtained by this calorimeter will not be very accurate. The dryness fraction calculated by this method is always greater than the actual. The only advantage of this method is the quick determination of the dryness fraction of a very wet steam.

3 Throttling Calorimeter

The arrangement of this calorimeter is shown in figure. The steam whose dryness fraction is to be determined is taken into the calorimeter through a sample tube and passed through a throttle valve as shown in figure. The steam is allowed to throttle down to a lower pressure until it comes out in the superheated condition. The pressure and temperature of steam coming out of the throttling valve are measured with the help of manometer and a thermometer.

Figure 3: Throttling calorimeter

4 Separating and Throttling Calorimeter

The dryness fraction measured with the help of separating calorimeter is always higher than the actual. This is because of incomplete separation of moisture by mechanical means. If the steam is highly wet (0.6 to 0.9), then its dryness fraction cannot be measured, by throttling calorimeter as it will not become superheated after throttling. Therefore the dryness fraction of highly wet steam is measured accurately by combining in series separating and throttling calorimeter. The arrangement of a separating and throttling calorimeter is shown in figure, where these calorimeters are placed in series. The steam from the sample tube is first passed through the separating calorimeter where major part of the water particles is removed and then it is passed on to throttling calorimeter.

Figure 4: Schematic diagram for the separating and throttling Calorimeters

The steam leaving the throttling valve comes out as superheated steam. The steam coming out of throttling calorimeter is condensed in a condenser and mass of the condensate is recorded. The mass of the water separated in separating calorimeter and the pressure and temperature of the steam leaving the throttle valve are recorded with the help of water manometer and mercury in glass thermometer.

ms= mass of steam condensed and collected from condenser. mw= mass of water collected from separating calorimeter. X= actual dryness fraction of steam in main pipe. X 1 = apparent dryness fraction of steam measured by separating calorimeter assuming that the steam coming out of separating calorimeter is completely dry. X 2 = actual dryness fraction of steam entering in to the throttling calorimeter. The apparent dryness fraction is given by

1

s s w

x m m m

=

• ---

Amount of water carried by the steam before entering into the calorimeter

= (^1 −^ x^ )^ (^ ms^ +^ mw ) -----------------------

Amount of water separated in separating calorimeter

= (^1 −^ x 1^ )(^ ms^ +^ mw ) ----------------

And amount of carried by the steam in in to the throttling calorimeter

= (^) ( 1 − x (^) 2 ) ms ----------------

The mass of water in the steam given by the equation (2) must be equal to the quantities of water given by equations (3) and (4).

(^1 −^ x^ )( ms^ +^ mw^ ) =^ ( 1 −^ x 1^ )( ms^ +^ m^ w ) +^ ( 1 − x 2^ ) ms

(^1) ( 1 1 ) ( 1 2 ) s s w

x x x m

− = − + − m + m But 1

s s w

m (^) x m + m =

Substituting the value in the above equation

1 − x = (^) ( 1 − x 1 (^) ) + (^) ( 1 − x 2 (^) )× x 1 (^) = 1 − x 1 (^) + x 1 (^) − x x 1 2

∴ x^ = x^ 1 x 2

This calorimeter gives very accurate value of the dryness fraction of the steam when it is considerably wet and which cannot be measured accurately by any other method. RESULT: Hence we studied different calorimeters for determination of dryness fraction of steam.