Heat pumps for wood drying – New developments and preliminary results
This paper succinctly presents new developments, preliminary statements and a number of energy results in the area of high-temperature heat pump technology for wood drying in a Canadian economic environment. A hybrid (electricity/fossil), high-temperature technology has been investigated and then field tested over the last two years. Several technical developments were achieved at the level of fluid selection, refrigerant flow control and system stability, variable dehumidifying capacity and appropriate drying schedules. The present study demonstrates that the thermodynamic efficiency and specific energy performance of the developed high-temperature drying heat pumps have generally reached the initial designed targets. Refinements of the integrated control methods involving variable speed and electronic devices are currently being undertaken in order to avoid undesired operating conditions that could cause mechanical failures or inefficient dehumidifying processes. The current research program aims at diversifying the applicable thermodynamic cycles, testing new environmentally friendly refrigerants and advanced components, and developing more advanced drying control strategies.