electromagnetic defrost heat pump?

[star882]

I have heard about a new technology that makes heat pumps more practical for very cold climates and avoid the "cold blow" problem at the same time.
Instead of switching over the heat pump for defrost, it uses a completely separate system for defrost.
In the outdoor unit, the coil has a wire embedded in it. It is insulated from the coil itself. It connects to a high power magnetron on one end and a sensor on the other. In normal heating operation, frost builds up on the coil. When a sensor detects the need to defrost, it stops the fans and compressor and starts the defroster. A high voltage transformer charges up some capacitors and feeds a little power to the magnetron. The small amount of electromagnetic radiation melts a little frost built up on the coil, causing the water to stick to the wire by surface tension. A moment later, a relay discharges the capacitors through the magnetron. The very intense burst of electromagnetic radiation is converted to heat in the water sticking to the wire, causing the water to flash to steam and blowing some frost out of the coil. This repeats several times until a sensor indicates the end of defrost in which case the defroster turns off and the compressor and fans turn back on.

I have not been able to find any more information on this. Has anyone else heard about this? I'm aware of only one unit using this technology, and that's a unit cobbled together by an amateur out of a normal heat pump, some surplus defibrillators, a surplus magnetron, and a few more parts to tie the design together.

[Brian_UK]

Hi Star, the USA patent description is here if you fancy a long read...
http://www.patentstorm.us/patents/5722245-fulltext.html

[The Viking]

A complicated solution to a simple problem me thinks.

[star882]

Hi Star, the USA patent description is here if you fancy a long read...
http://www.patentstorm.us/patents/5722245-fulltext.html

It's similar, but I don't find any mention of using capacitive discharge to create tiny "steam explosions" to blow out loose frost. I think the design I've heard of would be even more efficient since some energy used physically blows out frost instead of melting it. (It takes much less energy to move a given amount of frost a short distance than to melt it.)
I wonder if it could be used for low temperature refrigeration...

[Brian_UK]

I wonder how many extra service calls would result from that technology?

"Hello, yes there's a strange banging noise coming from the outdoor unit and a lot of sparks"

[Electrocoolman]

Is it April already?

[star882]

Now that I think of it, couldn't something similar be done with some slotted tubes in the coil that are blasted with compressed air for defrosting? Of course, the air must be perfectly dry and the tubes designed to prevent moisture infiltration or moisture will freeze inside and stop it from working. I guess it's better to use electromagnetic energy to make steam...
I have asked the person who told me about the technology and he says it had 5 32uF, 7.4kv capacitors (from surplus defibrillators) wired in parallel (about 3200J if I calculated right! However, much less than that actually goes into defrosting as the capacitors cannot be fully discharged and the magnetron is not 100% efficient.) and charged to about 6.3kv by means of a high voltage transformer (2.2kv) and voltage multiplier. A separate tap on the transformer powers the magnetron during the start of the defrost cycle. A vacuum relay then switches the magnetron to the capacitors, greatly increasing the power. At that point, the water on the wire actually becomes superheated for a moment and when it finally gets hot enough in even one spot, it violently boils, at which point the pressure and heat of the steam clears the coil of frost. This repeats several times to defrost the whole coil. (Since defrosted sections have virtually no water, they carry the electromagnetic energy though instead of transferring it to the water as they normally would. The defrosting would progress in a spiral on the coils - quite a sight to see!)

I wonder how many extra service calls would result from that technology?

"Hello, yes there's a strange banging noise coming from the outdoor unit and a lot of sparks"

According to the builder, the only noise it makes during defrost is the humming of the transformer, then the click of the relay quickly followed by a soft boom as a shower of "snow" and a little cloud of steam blow out of the machine. But there are no sparks when this happens.

Idea: install prototypes of the unit in supply houses in cold climates a few years before they are available for sale. Then add a strobe that flashes for a few minutes before the capacitors discharge and make sure it's in a visible location (like on top of a roof). Sure enough, some customers will come to the supply house when the unit defrosts, then ask about it when they see the rather dramatic defrost cycle.

[Josip]

Hi,

Now that I think of it, couldn't something similar be done with some slotted tubes in the coil that are blasted with compressed air for defrosting? Of course, the air must be perfectly dry and the tubes designed to prevent moisture infiltration or moisture will freeze inside and stop it from working. I guess it's better to use electromagnetic energy to make steam...

In the year 1984. we installed one Frigoscandia freezing tunnel with compressed air to remove ice from evaporator. That is ok for industrial use, but for domestic HP maybe too expensive

See attachment, or complete file here:
http://www.google.com/url?sa=t&ct=re...RMj2iVPc3UEZGA

Best regards, Josip

[Bones]

A complicated solution to a simple problem me thinks.

funny i was thinking the same thing until i read your post!

what brand systems use this technology if you know?