Experimental Theory Polytropic process.docx

FACULTY OF MECHANICAL AND MANUFACTURING ENGINEERING ENGINEERING LABORATORY IV GROUP 6B

PROPOSAL OF POLYTROPIC PROCESS FOR IDEAL GAS IN ISOTHERMAL CONDITION

COURSE CODE

: BDA 27501

SECTION

:6

LECTURER

: ENCIK HANIS BIN ZAKARIA

STUDENT NA NAMES : 1.

MUHA MUHAMM MMAD AD SYA SYAHM HMIL IL FITR FITRII OTHM OTHMAN AN

2.

MUHAMMAD AKMAL BIN KOSNAN

3.

MUHAMMAD AMINUDDIN BIN ZAIDI

4.

MUHAMMAD FAEZ BIN NOR AZMAN

5.

MUHAMMAD FAUZI BIN ABD GANI

Objective ●

To prove the equation, P1V1 = P2V2 by comparing actual data to calculated data

●

To draw P-V diagram and compare with theoretical diagram

●

To understand the relationship between pressure and volume under isothermal condition.

Experimental Theory

1. Polytropic Process The relationship between the pressure and volume during compression or expansion of an ideal gas can be described analytically. One form of this relationship is given by the equation:  P V n = constant  

A thermodynamic process described by the above equation is called a Polytropic process where the ‘n’ is the polytropic index.

2. Isothermal Condition Isothermal condition refers to a process in which a system changes be it the pressure, volume or contents without the temperature changing. From the point of view of the first law of  thermodynamics, this means that the internal energy of the system is unchanged. For a  polytrophic process under isothermal condition, the polytrophic index is given by n=1.

3. Boyle-Mariotte’s Law A gas thermometer is used to confirm this law. Gas will be trapped by mercury at a certain quantity. The initial quantity’s height is recorded. This initial volume is related to the initial  pressure which consist of the atmospheric pressure and the pressure exerted by the mercury itself. Thus the pressure exerted on gas, P.  P i = P  = P atm + P hg 

By using an air pump, air is pumped out of the thermometer. This create a vacuum that will  be negative in value and reduces the pressure inside the thermometer and by the law, the gas trapped by the mercury seal should expand and increase in height. The vacuum pressure is indicated at the gauge and referred as the gauge pressure. Thus the pressure exerted on gas, P:  P  = P  gauge + P atm + P hg  The volume V of the enclosed air column is determined by the pressure p. V can be calculated from the height h of the air column and the cross- section of the capillary where h is the height of mercury seal from the bottom and d is 2.7mm: V  =

πd2 h 4

Procedure

1.

Turn on the temperature sensor.

2.

Invert the gas thermometer and pump until the maximum gauge pressure.

3.

Make sure all mercury collected at the bulge.

4.

Turn the gas thermometer slowly to the original position.

5. Open the air valve to let air at atmospheric pressure push the mercury into the tube. Must  be done slowly to avoid mercury breaking and gas escaping. 6.

Record the initial height of mercury from the bottom of the thermometer.

7.

Pump the hand pump to the desired pressure with increment of 50 mbar.

8.

Record height for each pressure increment into table.

9.

Complete the table.

RESULTS:

 P  gauge (mbar ) 0 -50 -100 -150 -200 -250 -300 -350 -400 -450 -500 -550

Height (mm)

P (kPa)

Volume ( m3 )

1/ P (kP a−1 )