Defrost efficiency

[paceinternet]

Some interesting discussion on defrosting in this thread:
http://www.refrigeration-engineer.com/forums/showthread.php?33840-Buffer-Tank-Assisted-Defrost
So I have something for Pilko and MikeHolm and mad fridgie to pass comment on.

What do you think the efficiency difference would be between that method, or other methods, and avoiding defrost altogether by raising the ambient air temperature going into the outside coil?

If you could direct some warm air towards the intake to keep the overall input air temperature at ? (whatever temperature avoids icing) in a controlled way. This energy could come from a buffer and only be introduced when a sensor indicates it is needed. Maybe easier in an air to water system, but the initial question is, would the overall efficiency be better, because when you go through a conventional defrost routine, it must discharge quite a lot of energy to ambient and be lost, whereas the concept I am describing could recover some, or all, of that energy.
Conventionaly, there must also be some drop in efficiency as ice builds up on the fins and coil which would be avoided.

I don't know if any hot gas defrost systems attempt to do anything like this, or do they just heat the coil to remove ice when it has built up?

Thanks

[mad fridgie]

It is all about energy and time. Nothing is free!
So all you need to do is a number of energy mass balances.
So when it cold outside, what heats this air up. where did this energy come from, what is the cos of this energy, how much energy do you need to store.?
So basically look at the very big picture all of the time.
Also hot gas defrost, is not the same as reverse cycle defrost (most systems are reverse cycle)

[paceinternet]

Thanks MF.

Any information on alternatives to reverse cycle defrost systems would be appreciated.