Heat Transfer Fundamentals
Conduction- molecule to molecule
Convection- movement of heat in a liquid
Radiation- heat that travels through space and only changes the temp. of the objects it strikes
Material Classification
Thermal Conductors- gold, silver, copper and aluminum
Thermal insulators- foam, fiberglass, cork
Thermal Ratings
• U factor- overall co-efficient of heat transfer Btu/hr/cubed ft/F +d
• K factor- thermal conductivity rating- per inch thickness
• C factor- thermal conductance rating- for a given thickness
• R factor- thermal resistance- reciprocal of the U factor
Pressure
• is defined as Force per Unit of Area, such as Pounds per Square Inch (PSI), the pound is the force, the unit Area is square inch
Pressure Scales Used
- PSIG lb per square inch gauge
- PSIA lb per square inch absolute
- “Hg vac inch of mercury vacuum
- Microns
- “ Hg
Instruments used to Measure Pressure
• barometer
• U-tube Nanometer- reads in inches of water column
• Electronic Micron gauge
• Compound Gauge (bourdon tube(link and set of springs))
• High Pressure Gauge (bourbon tube)
Atmospheric Pressure
• atmospheric pressure is the pressure or weight of the atmosphere pushing down on the earth
• atmospheric pressure will support a column of
• mercury 29.92 inch high
• water 33.4 ft high
• water 406.8 inch high
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