Mixing Process (Steady Flow)
When two streams of air with different properties and flow rates are mixed, the properties of the resulting mixture (enthalpy, dry bulb temperature and saturation ratio) can be determined by…
Adiabatic Processes
The term 'Adiabatic' simply means without energy loss or gain. This refers mainly to the processes of evaporative cooling and desiccant dehumidification. Evaporative cooling occurs when warm air passes near…
Evaporative Cooling
Evaporative cooling is an adiabatic process, that is, there is no net heat loss or gain. When hot air stream is made to pass through wet spray, the sensible heat…
Heating and Dehumidification (Chemical Dehydration)
Heating and Dehumidification, also referred to as “chemical dehydration” is seeing increasing use in modern air-conditioning particularly in industrial environment. When air is brought into contact with a desiccant or…
Cooling and Dehumidifying
When air is cooled below the dew point temperature, Tdewpoint, condensation occurs and moisture is removed from the air stream. The exiting air stream is at a lower temperature and…
Governing Equation for Heating and Humidification
If the condition of the air is changing from state 1 to state 2, consider that the intersection of a horizontal line through state 1 and a vertical line through…
Humidification (Heating or Cooling)
This is the process of introducing moisture into the airstream. In winter, humidification frequently is required because the cold outside air, infiltrating into a heated space or intentionally brought in…
Governing Equation for Sensible Heating and Cooling
Example Calculate the amount of sensible heat that must be added to 100lb of air at 85°F dry bulb and 75°F wet bulb to raise the temperature of air to…
Sensible Heating
In HVAC systems, air is typically heated by passing it over a heating coil or use of electrical strip heaters. A schematic of a cooling coil is shown below. The…
Sensible Cooling
Air dew point temperature Tdewpoint is the temperature when air is 100% saturated and water begins to condense out of the air. When warm wet air is cooled as it passes…
