The air circuit consisted of an air duct, an electric heater,
an evaporator, a condenser, an air blower and a dryer. The
air duct was made of iron sheet with 2 mm thickness. Two
dampers were mounted to control the air flow rate. A centrifugal
air blower of 370 W was used to draw the air from
the evaporator and bypass path into the condenser where
an electric heater of 800 W was used to control the air temperature
at the entrance of the evaporator if needed.