Based on thermal design theory, a novel rotary heat exchanger
uses a short inexpensive plastic honeycomb. Based on dimensionless
groups, the predicted temperature efficiency of the heat
exchanger is 89% for a flow rate 8 L/s, but this excludes leakages.
After accounting for modelled bypass leakages, the predicted temperature
efficiency lower to 84%. This shows good agreement with
measured efficiencies of 83–84%% for 7.8 L/s from two experimental
methods. The available measurement standards did not suit this
application, so the performed experiments combine thermal measurements
and heat balance equations to determine temperature
efficiencies and pressure leakages. Pressure leakage reduces ventilation
and increases recirculated air, and bypass leakage reduces
temperature efficiencies. The measured pressure leakage is 18%, so
fan flow rates must be increased accordingly to meet ventilation
requirements. Despite significant leakage, the single-room ventilation
unit meets the development criteria and achieves greater than
80% temperature efficiency for a balanced nominal ventilation rate
of 8 L/s. Additionally, lower rotational speeds decrease heat recovery
in order to modulate supply and exhaust temperatures, and the
compact and inexpensive heat exchanger fits appropriately into a
cylindrical tube.