P07 More efficient defrost of air coil evaporators
 ispinne Projektleader Prof. Björn Palm
Research residence KTH

In all heat pumping processes where heat is extracted from the ambient air, for cooling or heating, there is a risk of frost formation on the evaporator surfaces. The frost increases the pressure drop, leading to increassed pumping power and decreased heat transfer, i.e. decreases the evaporation temperature and thereby lower energy efficiency. In this project we will investigate different methods of defrosting, or of decreasing the frost growth,
thereby increasing the energy efficiency of the process during one cycle. Particularly when using the new flat multichannel tubes, the defrosting has become a problem.
Several different methods have become interesting due to the development of new materials and as a result of higher energy prices:
*Drying of the air prior to the evaporator
*Superhydrophobic or hydrophilic surfaces
*Special structured surface
*”Smart” fin design to dry the air at the inlet
The project, done in cooperation with Electrolux aims to evaluate these methods.