Industrial dryers are very energy-intensive, contributing to a
large share of the thermal energy demand in industry. Most of
this energy is discharged as moist air to the environment. The
calorific content of the exhaust air is high due to the large amount
of water vapour in this waste stream. Heat pump systems can be
used to recover heat from the exhaust air, hereby raising the
energy efficiency of the dryer. Simulations have been performed
using data from an existing drying installation with conventional
heating. The increase in energy efficiency is analyzed for the
implementation of several types of absorption heat pumps in the
drying cycles. The simulation results show the influence of
different working fluid pairs and different configurations: type I,
type II and double lift cycle. The highest amount of energy
savings is achieved with type I absorption heat pumps using
water–lithium bromide as the working fluid pair. With optimized
temperature levels in the different components, the thermal
energy use of the complete dryer can be reduced with 20%. The
performance of absorption heat pumps in drying systems is
however still bounded by the temperature limit of the waterlithium
bromide working fluid pair. Searching for alternative
working fluid pairs for higher temperature applications is
therefore still essential and can increase energy savings even
more.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
