1. Lesson 2 TEMPERATURE AND PRESSURE MEASUREMENTS DEFINE the thermodynamic properties temperature and pressure. DESCRIBE the Fahrenheit, Celsius, Kelvin, and Rankine temperature scales including: – Absolute zero temperature – The freezing point of water at atmospheric pressure – The boiling point of water at atmospheric pressure CONVERT temperatures between the Fahrenheit, Celsius, Kelvin, and Rankine scales. DESCRIBE the relationship between absolute pressure, gauge pressure, and vacuum. CONVERT pressures between the following units: – Pounds per square inch – Inches of water – Inches of mercury – Millimeters of mercury – Microns of mercury

2. Temperature A measure of the molecular activity of a substance The greater the movement of molecules, the higher the temperature. Can be used to predict the direction of heat transfer

3. Temperature Scales Fahrenheit (F) – 32 0 F – Water Freezing Point – 212 0 F – Water Boiling Point Celsius (C) – 0 0 C – Water Freezing Point – 100 0 C – Water Boiling Point °F = 32.0 + (9/5)°C °C = (°F - 32.0)(5/9)

4. Temperature Scales (cont) Rankine (R) – Fahrenheit plus 460 0 (absolute scale for Fahrenheit) Kelvin (K) – Celsius plus 273 0 (absolute scale for Celsius)

5. Temperature Scales (cont)

6. Pressure A measure of the force exerted per unit area on the boundaries of a substance (or system) Is uniform inside an enclosed container Is frequently measured in units of lbf/in 2 (psi).

7. Pressure Scales Absolute Pressure - Measured relative to a perfect vacuum (psia) Gauge Pressure - Measured relative to atmospheric pressure (psig) Vacuum – Any pressure that is below atmospheric pressure (14.7 psi)

8. Pressure Relationships

9. P abs = P atm + P gauge P abs = P atm - P vac

10. Pressure Conversion Factors 14.7 psia = 408 inches of water 14.7 psia = 29.9 inches of mercury 1 inch of mercury = 25.4 millimeters of mercury 1 millimeter of mercury = 103 microns of mercury