Posted by Pete C on December 11, 2005, 3:11 pm
Usually the heat pump goes into a defrost cycle to get rid of the ice.
I wonder if water would be a good way of defrosting it, the water only
needs to be 1 or 2C, this could be achieved by pumping it through a
ground loop, pond or low grade solar panel and storing it in a tank.
Assuming water at 0C is not too good for defrosting, anyone know how
much ice can be thawed by a cubic metre of water at 3C?
Posted by nicksanspam on December 11, 2005, 3:38 pm
... 300%? :-)
Running the outdoor fan without the heaters might be more efficient.
Sounds messier and more complicated.
... 144 Btu can melt a pound of ice, so a pound of water cooling 5.4 F
(3 C) can melt 0.0375 pounds of ice, ie 27.7 times less. Then again,
the average annual UK air temp (close to the water temp) is 9.5 C.
Posted by ivan on December 10, 2005, 1:22 am
The navitron website is www.navitron.org.uk
Air source heat pumps are not very efficient. In theory they ought to
be, but the problem lies in the rate of heat transfer from the air heat
exchanger. This bottleneck causes condensation and then ice to form on
the heatexchanger. The ice acts as an insulator, causing the heatpump
to work harder, causing more ice etc. The COP (coefficient of
performance) in practice is much lower than with a ground source heat
pump for this reason. COPs indicate the amount of heat produced from a
given amount of electricity input. Typically GSHPs provide COPs of 4-6,
whereas air source is probably nearer 2-3 depending on weather