Marcet Boiler

TITLE

Marcet Boiler

OBJECTIVES

The purpose of this experiment is:

1.To study the relationship between the pressure and temperature of saturated steam in equilibrium with water.

2.To obtain the saturated pressure curve.

INTRODUCTION

Thermodynamic related to physics which deal with work and energy of a system. It is the study about the interchange of the heat and work between the system and its surrounding during a process and also related to the changes in the fluid properties. Since the thermodynamic substances obey the e quation of state, it can be labelled as ideal gas. However, not all real gases completely obey the ideal gas equation since there was some modification to the equation of state which allowed the application occurred in their own properties.

The state of equilibrium was depends on the pressure between the water surface and the steam. The increases energy in the water causes the molecules moves rapidly. Thus, the number of molecules that escaped from the surface until it reached equilibrium will increases. The lower the pressure, the easier the molecules to leaves the water surface and the less energy required to reach equilibrium state. The saturated pressure at equilibrium occurred at given temperature and pressure.

Marcet Boiler (Model: HE169) suitable to investigate the relationship between temperature and pressure of a saturated steam with water in equilibrium conditions which was very suitable for all pressure between atmospheric and 10 bar (abs). The measured slope (dp/dT) values can be obtained and the theoretical values can be determined by calculation using the data from the steam table. Hence, both of the data been analyzed by comparing the values that obtained.

A gas can be approximated to the ideal gas, where the relations between temperature, T, and pressure, P, can be expressed in ideal gas equation of state:

Where;

P: absolute pressure of the gas (Pa)

V: volume (m3)

n: amount of substance (moles)

R: ideal gas constant

T: absolute temperature (K)

The molecules acted vigorously due to the increases in energy in water. Therefore, the number of escape molecules from the surface until it reached equilibrium state will increases. The equilibrium state depends on the pressure between the surface of water and steam. When the pressure is lower, the molecules to leave the water surface become easier and equilibrium state can be achieve with less energy.

When the volume of the gas is constant, the temperature will proportional to the pressure. Thus, this is where the Clapeyron equation takes the form:

(1)

The condensed phase vc (liquid or solid) is greatly exceed by the specific volume for the gas phase, vg when the phase transition of the substances between gas and condensed phase and it occur at the temperature which is lower than the critical temperature of the substances.

(2)

The approximate specific volume at low temperature, will be like in equation (2). Thus, for a saturated gas, which . The Clapeyron equation can be written as:

(3)

Since . Where;

hg: enthalpy of saturated vapor

hf: enthalpy of saturated liquid

hfg: enthalphy of vaporization

vg: specific volume of saturated vapor

vf: specific volume of saturated liquid

METHODS AND MATERIALS

Figure 1: Unit Construction for Marcet Boiler (Model: HE169)

1. Pressure Transducer 6. Bourdon Tube Pressure Gauge

2. Temperature Controller/Indicator 7. Temperature Sensor

3. Pressure Indicator 8. Pressure Relief Valve

4. Control Panel 9. Water Inlet Port

5. Bench 10. Heater

RESULTS

Table 1: Tabulated Experimental Results

Pressure (bar) Temperature Measured Slope, dp/dT (kPa/K) Calculated Slope, hfg/Tvg

(kPa/K)

Increase (°C) Decrease (°C) Average (°C) Average

(K)

1.0 100.0 101.3 100.7 373.9 0.0 3.6

1.1 101.2 104.2 102.7 375.9 5.0 3.9

1.2 103.9 106.5 105.2 378.4 4.0 4.1

1.3 106.2 108.9 107.6 380.8 4.2 4.4

1.4 108.6 111.0 109.8 383.0 4.5 4.7

1.5 110.7 113.1 111.9 385.1 4.8 5.0

1.6 112.6 114.8 113.7 386.9 5.6 5.2

1.7 114.7 116.7 115.7 388.9 5.0 5.5

1.8 116.4 118.5 117.5 390.7 5.6 5.8

1.9 118.2 120.1 119.2 392.4 5.9 6.0

2.0 120.2 121.7 121.0 394.2 5.6 6.3

2.1 121.3 123.3 122.3 395.5 7.7 6.5

2.2 122.9 124.8 123.9 397.1 6.3 6.8

2.3 124.3 126.2 125.3 398.5 7.1 7.1

2.4 125.8 127.5 126.7 399.9 7.1 7.3

2.5 127.1 139.0 133.1 406.3 1.6 7.5

2.6 128.5 132.2 130.4 403.6 -3.7 7.8

2.7 129.7 131.5 130.6 403.8 50.0 8.0

2.8 131.0 132.7 131.9 405.1 7.7 8.3

2.9 132.2 133.9 133.1 406.3 8.3 8.5

3.0 133.4 135.1 133.3 406.5 50.0 8.8

3.5 138.8 140.3 139.6 412.8 7.9 9.9

4.0 143.7 145.0 144.4 417.6 10.4 11.0