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Description:
The heat is then recycledback through the dryer by heating the air entering the dryer. Theheat pump
drying system is a combination of two sub-systems: a heat pump anda
dryer.
The heat pump operates according to a basic air
conditioning cycle involving four main components: the evaporator,the
compressor, the condenser and the expansion valve.
The working fluid (refrigerant) at low pressure is
vaporized in the evaporator by heat drawn from the dryer exhaustair. The
compressor raises the enthalpy of the working fluid of the heatpump and
discharges it as superheated vapor at high-pressure. Heat isremoved from the
working fluid and returned to the process air at the condenser. Theworking
fluid is then throttled to the low-pressure line (using anexpansion valve) and
enters the evaporator to complete the cycle.
In the dryer system, hot and dry air at the exit of
condenser is allowed to pass through the drying chamber where itgains latent
heat from the material. The humid air at dryer exit then passesthrough the
evaporator where condensation of moisture occurs as the air goesbelow dew point
temperature.
A performance study of a heat pump dryer system is
required to fully understand its operating characteristics based ondifferent
materials to be dried. To accomplish this objective, the projectwas divided
into three tasks (steps). Task A is concerned with the design andconstruction
of a prototype heat pump dryer system. Task B involvesfield-testing of a
prototype system using specialty crops or material with similarcharacteristics.
Finally, task C is to develop a comprehensive computer model usingthe
fundamentals of thermodynamics for a heat pump dryer system and todetermine its
accuracy compared to experimental results.
