Total Heat:
Sensible Heat: Heat causing a temperature change without changing the state of a substance.
Latent Heat: Heat required or released to change the state of a substance without changing its temperature.
Psychometric Chart:
Used to plot air conditions (dry bulb temperature, wet bulb temperature, and relative humidity) to determine enthalpy.
Enthalpy represents the total energy in the air (both internal energy and the energy required for expansion/compression).
Delta H (Change in Heat):
Calculated by subtracting the enthalpy values found on the chart.
Example:
Incoming air: 90°F at 40% humidity = 34.9 BTUs.
Outgoing air: 55°F at 100% humidity = 23.2 BTUs.
Delta H: 34.9 BTUs - 23.2 BTUs = 11.7 BTUs.
Total Heat Formula:
Formula: Total Heat = CFM × 4.5 × Delta H.
4.5: Weight of air (0.075 pounds per cubic foot) × 60 minutes per hour.
Example:
CFM = 1200 (from previous lessons).
Multiply 1200 by 4.5 = 5400.
Multiply 5400 by Delta H (11.7) = 63,180 BTUs.
Importance of Total Heat Calculation:
Crucial for system design, efficiency, and performance in HVAC.
Helps HVAC technicians design, install, maintain, and optimize systems.
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