Graphical Representation of Data

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LECTURE 7

GRAPHICAL REPRESENTATION OF DATA

1. Pressure versus temperature (P-T)

2. Pressure vs. volume (P-v)

3. Temperature vs. volume (T-v)

4. Temperature vs. entropy (T-s)

5. Enthalpy vs. entropy (h-s)

6. Pressure vs. enthalpy (P-h)

The term saturation temperature designates the temperature at which vaporization takes place.

For water at 99.6 C the saturation pressure is 0.1 M Pa, and for water at 0.1 Mpa, the saturation temperature is 99.6 C.

If a substance exists as liquid at the saturation temperature and pressure it is called saturated liquid.

If the temperature is of the liquid is lower than saturation temperature at the existing pressure it is called sub-cooled liquid or compressed liquid.

1. When a substance exists as part liquid and part vapor at the saturation temperature, its quality is defined as the ratio of the mass of vapor to the total mass. 2. If a substance exists as vapor at the saturation temperature, it is called a saturated vapor. 3. When the vapor is at a temperature greater than the saturation temperature, it is said to exist as superheated vapor. 4. At the critical point, the saturated liquid and saturated vapor state are identical. 5. At supercritical pressures, the substance is simply termed fluid rather than liquid or vapor. 6. If the initial pressure at –200C is 0.260 kPa, heat transfer results in increase of temperature to –100C. Ice passes directly from the solid phase to vapor phase. 7. At the triple point (0.6113 kPa) and a temperature of –200C, let heat transfer increase the temperature until it reaches 0.010C. At this point, further heat transfer may cause some ice to become vapor and some to become liquid. The three phases may be present simultaneously in equilibrium.

Tables of Thermodynamic Properties

Tables of thermodynamic properties of many substances are available, and in general, all these...
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