Mechanical EngineeringSchool of Engineering and Physical Sciences

LABORATORY REPORT

TITLE: The Boys’ Gas Calorimeter

OBJECTIVE: Work out the HCV and the LCV of natural gas

MODULE No: B5.8EE

MODULE TITLE: Mechanical Engineering 5

Lecturer: Dr Baixin Chen

Year: 2 Term: 1 Session: 2008/2009

Grade: Name: Paul Graham Miller

Registration Number: 074575749

Marker’s Initials: Term Address: 64 Colinton Mains RoadEdinburghEH13 9AW

Email: Pgm3@hw.ac.uk

Submission Date: 9/12/2008

Group/Group Members:(If applicable)

Group I

The Boys Gas Calorimeter

Introduction............................................................................................................3Objective................................................................................................................4Method...................................................................................................................4Theory....................................................................................................................5Results....................................................................................................................6Discussion..............................................................................................................7Conclusion..............................................................................................................7

Introduction

The Boys gas calorimeter is a simple and effective means of measuring gases calorific

values. The Boys gas Calorimeter is named after an English physicist called Sir

Charles Boys (1855-1944). It is the standard piece of equipment used to calculate the

Higher Calorific (HCV) and the Lower Calorific (LCV) of gases.

Calorimetry is the name given to the measurement of heat. When a fuel is burnt at

constant pressure the energy transferred as heat to the surroundings per unit quantity

of fuel is called the calorific value. The products of combustion will be at the same

temperature as the fuel and air (reactants). If condensation occurs in the water on the

products side then the Higher Calorific value is determined, However if the water

remains in the vapour phase then the Lower Calorific value is sought.

Objective

To determine the higher and lower calorific values of natural gas. (HCV and LCV). Sometimes referred to as the gross calorific value and the net calorific value.

Method

The most important part of this experiment was to measure all constant values before

we started. This involved recording the gauge pressure, volume of gas, inlet

temperature, exhaust temperature, the temperature in and out of the cooling water and

the time which in the case of this experiment would be 60 seconds.

The experiment was repeated four times, the first two times the experiment was set up

so that the higher calorific value of the natural gas could be determined. The reason it

was done twice was to try to ensure accuracy of results. For the second part of the

experiment we set the apparatus up so that the lower calorific value could be

determined. The way this was done was to reduce the volume of gas in the cylinder.

Figure 1a: The Boys’ Gas Calorimeter

When the experiment is ready to start a beaker is placed under the tap that allows the

cooling water out and the pipe that that carries the condensate is moved from a

position of waste to that of being collected into a separate beaker. The time for the

experiment was recorded using a normal stopwatch; in this case we decided to do the

experiment for 60 seconds.

Theory

Results

Parameter Test No. 1 Test No. 2 Test No. 3 Test No. 4GasVolume Of gas (l) 1.52 1.56 0.56 0.54Gauge Pressure (Pa) 39240 39240 9810 9810Absolute Pressure (Pa) 139240 139240 109810 109810Inlet Temperature (K) 292.15 292.15 292.15 292.15Outlet Temperature (K) 296.15 296.15 292.15 296.15Elapsed Time (Sec) 60 60 60 60Corrected Volume (288.15K 1bar)

1.54 1.58 0.56 0.55

Volume flow/sec (15˚C 1bar)

0.026 0.026 9.3 x 10-3 9.16 x 10-3

Cooling WaterVolume of coolant(ml) 400 400 400 380Elapsed time(sec) 60 60 60 60Mass collected(g) 400 400 400 380Mass flow/sec(g/sec) 6.68 6.68 6.68 6.3Temp. in(K) 285.15 285.15 285.15 285.15Temp. out(K) 320.15 320.15 297.15 320.15Specific heat capacity (J kg–1 K–1)

4184 4184 4184 4184

CondensateVolume collected(ml) 2.5 3 2.5 2.2Elapsed time(sec) 60 60 60 60Mass collected(g) 2.5 3 2.5 2.2Mass collected/sec(g/sec)

0.04 0.05 0.04 0.037

Latent heat 5.645 6.774 5.645 4.97

HCV 38537 37549 34070 103050LCV 34820 33203 23981 93843

Discussion

It appears from published values of natural gas’ higher calorific values and lower

calorific that we were not to far away with our values. Having said that there does

appear to quite a large error margin for our last attempt with a value of 103050 for the

HCV appearing to be extremely high. The most apparent error here seems to be the

rise in temperature of the water. The rise in temperature was concurrent with the first

two parts of the experiment i.e. 35K however in my opinion the rise in temperature of

the water should have been considerably less. The reason for this error could be

explained away by human error, not reading the thermometer correctly or there could

have been a more serious flaw in that there may have been an equipment malfunction.

Another possible source of error may have been to do with a rise in the ambient

temperature.

It does appear that for the main our values were quite accurate and consistent with

know data for HCV and LCV of natural gas

Conclusion

The Boys Gas Calorimeter is a very useful way of measuring out experimentally the

HCV and LCV of different gases. American power plants prefer to use the higher

calorific values (gross calorific value) to measure the thermal efficiency of their

power plants, whereas the Europeans prefer to us the lower calorific value (net

calorific value).