Air-Conditioning Processes
Presented by: Nichole Whisman April 26, 2001
• Review – Basic air-conditioning processes • Refrigerant based air-conditioners • Evaporative cooling • Cooling with dehumidification – Example • Video – Importance and applications of humidification
TERMS YOU NEED TO KNOW
Specific Humidity –
The amount of water vapor in the air.
Relative Humidity –
The amount of water vapor in the air relative to the amount of water the air can hold.
Four Basic Air-Conditioning Processes
Simple Heating
Just raising the temperature!
Relative humidity
DECREASES with simple heating
( since the moisture capacity of air INCREASES with temperature)
Simple Cooling
Lowering the temperature!
Relative humidity
INCREASES with simple cooling
(since the moisture capacity of air DECREASES with temperature).
Humidifying
Simply adding moisture!
Dehumidifying
Removing moisture!
(Low relative humidities combined with high temperatures.)
A. Compressor B. Fans C. Expansion valve D. Hot air to outside E. Cold air to inside
HOW CAN YOU SAVE 60%-90% ON YOUR COOLING BILL AND HELP THE ENVIRONMENT?
EVAPORATIVE COOLING!!
• Work well in dry climates. • Don’t use CFC’s or other ozone depleting compounds. • Operate on a basic principle: As water evaporates, the latent heat of vaporization is absorbed from the water and the surrounding air. Both the water and the air are cooled in the process.
Examples of Evaporative Cooling
• Waterfalls • Sprinklers on a hot day • Dogs - panting
Evaporative Coolers
• Large fan draws fresh outside air through wetted pads. • Some water evaporates – specific humidity is increases. • Air is cooled 10-30 degrees F.
TEMPERATURE DELIVERED BY EVAPORATIVE COOLER
COOLING WITH DEHUMIDIFICATION
•In humid climates is is desirable to cool the air and remove some of the moisture. •In order for condensation (and removal of moisture) to occur the air must be cooled below comfortable room temperature. •The air is then passed over heating coils to raise the temperature to a comfortable level. Cooling section Heating section
T1 φ1
1 w
T2
2 3
T3 φ3
Heat Pipe Technology Inc.
Gainsville, Fl
HEAT PIPES
A run-down on how they work
A. Heat is absorbed from hot, humid air in the evaporating section. B. Fluid boils to vapor form and rises. C. Heat is released from the upper part of cylinder to the over-cooled air. Vapor condenses back to liquid phase. D. Liquid returns by gravity to the lower part of cylinder (evaporating section).
HEAT PIPES
CUT POWER REQUIREMENT BY
20%-50%
• ELIMINATE the heating coils •LESSEN the load in the cooling section.