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Lc_shi
23-06-2005, 02:13 AM
Below is the information from ORNL on the frostless heat pump.
Who know more about it? I can't send email to the researcher.
Any one can give comment on it? thx.


http://www.ornl.gov/sci/btc/apps/frostlesspump.htm

Frostless Heat Pump

During a substantial portion of the heating season in temperate climate regions, where most heat pumps are installed, frost will build up on a conventional heat pump s outdoor heat exchanger coil (when the ambient temperature is below about 40F). Shortly after this frost accumulation begins, the temperature of the indoor heat exchanger coil and of the air supplied by it to heat the indoor space starts to decrease. When temperature, time, or demand controls mandate defrosting of the coil, a four-way valve temporarily reverses the heat pump cycle. During the reverse-cycle defrost period, heat is taken from inside the house (from air blown across the indoor coil) and is pumped outside to raise the temperature of the outdoor coil sufficiently to melt the accumulated frost. In an attempt to compensate for this heat loss and to temper the resulting decrease in the temperature of the air supplied to the indoor space, conventional systems must energize supplemental resistance- heating elements. However, even with substantial power flowing through the heating elements, the indoor air temperature is temporarily lowered resulting in what is commonly called "cold blow," a major concern of heat pump manufacturers and consumers. The term "cold blow" in heat pumps means the indoor supply air temperature by the heat pump is usually lower than our skin temperature which gives us a "cold blow" feeling.

The characteristics of the defrosting cycle just described (a) reduces occupant thermal comfort because of the cold blow effect and (b) decreases system reliability because of the periodic cycle-reversing stresses imposed on components such as the four-way valve, the compressor, and the resistance- heating elements.

The Frostless Heat Pump addresses, in a cost-effective manner, all the concerns outlined above by drastically reducing the frequency of defrost cycling (by a factor of 5 in the Knoxville, Tennessee area) and by eliminating cold blow. The key innovation is the addition of heat to the accumulator, which increases the temperature of the refrigerant entering the outdoor coil. The innovation is based on the principle that adding heat internally into a Rankine cycle can shift the heat absorption and rejection temperatures upwards. Tests have shown that the addition of moderate amounts of heat dramatically retards frost formation over a substantial range of outdoor ambient conditions where frost is likely to form. Most of the heat added to the accumulator is delivered to the indoor coil, providing increased heating capacity and improved thermal comfort in the form of higher air temperatures entering the indoor space.

Because of its increased heating capacity, the Frostless Heat Pump is likely to meet the heating demand of a house sooner and therefore cycle off sooner, before the outdoor coil requires defrosting. If the outdoor ambient temperature is lower than about 30F, adding a moderate amount of heat to the accumulator may not retard frost formation sufficiently to avoid cycle reversing. However, when the Frostless Heat Pump does require cycle reversing, the indoor fan is shut off, thus avoiding "cold blow" draft and heat removal from the conditioned space. Heat to defrost the outdoor coil is taken from the heat provided to the accumulator.

In summary, in comparison with conventional heat pumps , the Frostless Heat Pump increases occupant thermal comfort, increases system reliability, and reduces power surges.

wambat
24-06-2005, 12:28 AM
I believe this is the process taking place when the heat pump is in the heating mode. As OSA temperatures go down, the superheat back to the compressor goes down this in turn results in a lower discharge temperature to the indoor coil so by adding heat to the accumulator it raises the superheat to the compressor which raises the discharge temperature to the indoor coil. all this raises the totat heat of the liquid to the outdoor coil which has an aparant effect on total heat of the saturation temperature. Remember the adiabatic effect of the expansion process, total heat in ..total heat out.

Rob S
05-02-2006, 08:05 PM
Are they just using an electric well immersion heater in the accumulator.. or hot gas loop in it too?

Anyone can take a 200W crankcase band heater and wrap it around the accumulator, add a stat to turn the heater on below 42F OSA, and a relay to bypass it in cooling mode.

Personally I would think it would almost make more since to add some lowvoltage (24VAC) heaters to outdoor coil. Controling them could be as simple as a PID static pressure control, temperature, etc.

slingblade
06-02-2006, 09:46 PM
Hi guys

You don't have to make it so comlicated relays and so on

Just a simple magic connect the heater element parallel to the 4 way valve coil( 90% of the 4 way valves are energised during heating) and then bingo when thesystem is in heating mode this trick will do the magic.Also I don't see a problem why not connect this heater directly to single phase no matter what mode the suction pipe entering compressor will always be suction gentlemen ain't it.(another magic trick me thinks):D :D :D :D

less complicated than that would be to install the condensing unit indoors (more specifically in the same room as the evap.) and fully remove the problem of low air temperature as the heat generated by the evaporator will give a constant helping hand to the defrost problem. more slingblade wisdom "FREE OF CHARGE"

US Iceman
07-02-2006, 01:08 AM
The key innovation is the addition of heat to the accumulator, which increases the temperature of the refrigerant entering the outdoor coil.

Key innovation??? ;)

Is this what Phd's are working on?? :rolleyes:

Why not put hamsters in a wheel and blow air over them to keep the outside coil warm??? The faster they run, the higher their metabolic rate will be. Even when they are not running, the cold will make them shiver, so they still have some heat ouput. This option may not be covered under warranty though.

Better yet, install a gas burner under the outdoor unit to keep it warm.

Granted, what they are saying will provide the effect stated. I doubt the heat pump would be frost-less though. The info LC posted looks more like marketing material than engineering.

Lc_shi
07-02-2006, 02:08 AM
I read it at ORNL website and the article title attracts me but I can't find useful material from it. Air -source heat pump defrost is a key issue for the hp perfromance.
Some manufacturer says they made air-source hp can work at -22C condition and get COP 2.2. I don't know how to get it. anybody know about the tech in this field?

thx & rgds
LC:)

US Iceman
07-02-2006, 03:44 PM
Air-source heat pumps were being sold in very large quantities many years ago. After the first full year almost everyone I knew who had one complained of cold air blowing during the winter.

I suspect one of the problems is the limited coil surface used on the outside coil. Smaller coils would require lower evaporating temperatures. The lower evaporating temperatures increase the potential for frost formation, which is dependent on the air dewpoint temperature.

If the heat pump was operating at -22C, then this is not that much different than a refrigeration system that is used for a walk-in freezer.

LC, who was the manufacturer of this heat pump?

Peter_1
07-02-2006, 09:13 PM
Air-source heat pumps were very being sold in large quantities many years ago. After the first full year almost everyone I knew who had one complained of cold air blowing during the winter.

I'm one of them.:o :o

Lc_shi
08-02-2006, 02:18 AM
As I know,Gree China is a manufacturer.

Peter_1
08-02-2006, 09:40 AM
Some manufacturer says they made air-source hp can work at -22C condition and get COP 2.2. I don't know how to get it. anybody know about the tech in this field?LC:)

Impossible LC, you can't change nature laws.
Sure, it's possible a COP of 2.2 if you condens perhaps at 0C but this will give you not that much heat anymore :D
We better speak then of a CP (Coldpump :p )

Bitzer: ambient -22C is TE of -28C, condensing at 28C with R404a gives COP of 2.2.
You can't heat a house with a condensing temperature of 28C when it's outside -22C.

KoBushi
10-02-2006, 04:14 PM
It looks like all this would do is lower the efficiency of the heatpump. As well as adversely effect superheat back to the compressor in heat mode.

As for running a heater off of the reversing valve, the reversing valve is typicaly 24v; not going to heat the accumulator very much; also the wires running to the reversing valve are small guage; not going to handle the amp draw of a heater. Better to use a relay actuated in parrallel to the reversing valve to trigger a 220 or 115 heater if your going to do it.

But you'd be better of just getting a larger heat pump. or at least just big-ass outside coil; this increases efficiency in both AC and heat modes. Also over-sizing the system helps (especially since most people under-size them to begin with :P) and be sure the duct work is designed FOR a heat pump, not for gas heat, if you retro-fit a heat pump it's not going to work very well in most cases.

KoBushi
10-02-2006, 04:14 PM
It looks like all this would do is lower the efficiency of the heatpump. As well as adversely effect superheat back to the compressor in heat mode.

As for running a heater off of the reversing valve, the reversing valve is typicaly 24v; not going to heat the accumulator very much; also the wires running to the reversing valve are small guage; not going to handle the amp draw of a heater. Better to use a relay actuated in parrallel to the reversing valve to trigger a 220 or 115 heater if your going to do it.

But you'd be better of just getting a larger heat pump. or at least just big-ass outside coil; this increases efficiency in both AC and heat modes. Also over-sizing the system helps (especially since most people under-size them to begin with :P) and be sure the duct work is designed FOR a heat pump, not for gas heat, if you retro-fit a heat pump it's not going to work very well in most cases.

frank
13-02-2006, 09:39 PM
just big-ass outside coil

I've tried to find these in our office catalogues :D

and be sure the duct work is designed FOR a heat pump, not for gas heat

Will your Ductolator allow for this Marc? :)

Beats me though what the difference is :)

US Iceman
14-02-2006, 01:14 AM
I've tried to find these in our office catalogues

Frank, they are on the shelve next to this. :p

http://bigassfans.com/downloads/images/Fanny_600X800.jpg


Sorry, I could not resist.

Josip
14-02-2006, 02:02 PM
Heat pump allows us to extract and transfer (heat pumps does not produce heat) heat from one place to another by adding work to that cycle. A/C, heat pump and refrigerator are heat engines.

Heat engines in this case heat pump helps us to use one unit of electric energy to transfer more than one unit of energy from cold place to warm place. The ratio of the energy transferred to the electric energy used in the process is called coefficient of performance CP and for heat pumps practically can be up to 4 or less for refrigerator. For this reason condensers are bigger than evaporators. Carnot cycle we can not reach due to friction loss.

Extracting one unit of energy from outside (air, water, soil, some source of waste energy from process plant, etc.) and using electric energy we can transfer 4 units of energy into our home for heating.

Very nice, until we came to situation where we can not extract any energy from cold place due to almost 0 (zero) heat exchange because our heat exchanger is frozen (insulated).

The bigger size of heat exchanger (can delay freezing, but not avoid it) and big CP cannot change anything because we still have:

Obtained energy for heating Q
Extracted outside energy Ee
Coefficient of performance CP

Q= Ee x CP = 0 x 4 = 0

Playing with defrosting cycles like Frostless heat pump for air-source heat pump is possible only where we have moderate climate conditions. To avoid "cold blow" we should install geothermal heat pumps.

Peter_1
15-02-2006, 08:02 PM
To avoid "cold blow" we should install geothermal heat pumps.
I totally agree with this.
LC mentioned this already in a threat and as said in other posts, I'm making a vertical drill for a DX heat exchanger.
I expect a boom in this market.

star882
15-02-2006, 10:06 PM
heat pumps does not produce heat
I thought that there's more heat coming out of a heat pump than what's going in.

lin
16-02-2006, 01:43 AM
lc_shi,
Could u give some more detailed infos about Gree's low temp heat pump?
I had read their adv.

Lc_shi
16-02-2006, 01:48 AM
I'm making a vertical drill for a DX heat exchanger.
I expect a boom in this market.

Hi Peter,
How much the capacity of the DX HEX you're making?
I've got a comment from a professor that he doesn't recommend any DX system. My understanding is there will be big pipe pressure loss for large system. It's only fit for small system,e.g. residetial heating.
how about your idea?

regards
LC:)

Josip
18-02-2006, 11:02 AM
I thought that there's more heat coming out of a heat pump than what's going in.

Yes, you are right star882, but heat pumps serves only as transporting conveyors. It is named "heat pump" so we pump (transfer) energy from one place to another applaying some work and get out about 3-4 times more energy than that we put into "pumping" process.

Heat pumps do not produce heat becuse we must have heat/energy source (nature, waste heat, etc) at low energy level and pump that energy to a higher energy level where we can start to use/reuse it.

One example: reversible hydro electric power plant

Water is behind dam (at high energy level) coming down to turbines and generators producing electrical energy and run out (at low energy level) as river or creek. Through day time we use a lot of electrical energy but our energy source (river, creek) is not constant (no rain). We also produce electrical energy over night time (we cannot stop generators and turbines) when demands for electric energy are small. What to do in that case. Just to use one part of produced (cheap and not needed) electric energy and pump some water ( at low energy level) back behind the dam (at high energy level) to reuse it.

Here we also have some kind of "energy pump" and that pump is not producing energy at all (we, even have to spend some energy to run electric motor of that pump :) ) just transfer it to some level where we can use/reuse it.

This is not comparable to heat pump exactly, just want to give some picture of energy transfer.

AYIBIBIO
05-02-2008, 11:29 PM
Heat pump allows us to extract and transfer (heat pumps does not produce heat) heat from one place to another by adding work to that cycle. A/C, heat pump and refrigerator are heat engines.

Heat engines in this case heat pump helps us to use one unit of electric energy to transfer more than one unit of energy from cold place to warm place. The ratio of the energy transferred to the electric energy used in the process is called coefficient of performance CP and for heat pumps practically can be up to 4 or less for refrigerator. For this reason condensers are bigger than evaporators. Carnot cycle we can not reach due to friction loss.

Extracting one unit of energy from outside (air, water, soil, some source of waste energy from process plant, etc.) and using electric energy we can transfer 4 units of energy into our home for heating.

Very nice, until we came to situation where we can not extract any energy from cold place due to almost 0 (zero) heat exchange because our heat exchanger is frozen (insulated).

The bigger size of heat exchanger (can delay freezing, but not avoid it) and big CP cannot change anything because we still have:

Obtained energy for heating Q
Extracted outside energy Ee
Coefficient of performance CP

Q= Ee x CP = 0 x 4 = 0

Playing with defrosting cycles like Frostless heat pump for air-source heat pump is possible only where we have moderate climate conditions. To avoid "cold blow" we should install geothermal heat pumps.


Hi Josip,, thank you for this good explanation and conclution. This tells me that you understands heatpump technology very well. I also feel you can't make any magic with air source heatpumps if there is no heat source (warm air). We all want to use less power that is why we all want to use the heatpump to move more energy,, but if that energy ( heat)is not there then we are just wasting power. Thank you and I wish many people will read and understan your explanation,,.

danny

Peter_1
10-02-2008, 01:20 PM
I also feel you can't make any magic with air source heatpumps if there is no heat source (warm air). We all want to use less power that is why we all want to use the heatpump to move more energy,, but if that energy ( heat)is not there then we are just wasting power.

Danny,
Warm air is relative: if the outside air has a temperature of -5C (23F) then this air is still warm compared to a fluid of -10C (14F) and there is still energy available in this air.
So the energy is always there, even if the air has a temperature of -20C (-4F)

nike123
10-02-2008, 02:05 PM
I think he is referring at fact that if we spend more energy than we could gain from moist and cool air (loss at defrosting and low EER) than, there is no point in using heat pump as heat source.

AYIBIBIO
10-02-2008, 04:01 PM
Danny,
Warm air is relative: if the outside air has a temperature of -5C (23F) then this air is still warm compared to a fluid of -10C (14F) and there is still energy available in this air.
So the energy is always there, even if the air has a temperature of -20C (-4F)

Thanks Peter for this information,, but I know there is still some energy in low temp air, but we want to move more energy with less power. I feel it doe not sound well to evaporate at low temperatures that will give you low cops. Now lets remember that low evaporating temp don,t give high cops, and the higher the cop of a heat pump the better. Pet, till the nex, it,s take care.

danny

richard1900
24-03-2008, 04:14 AM
I am in the process of producing a CO2 heat pump.
Do you know were I can find a 9Kw
compressor?

I have contacted automotive companies and they do not have CO2 units avalible for sale yet.
Thanks

Toosh
25-03-2008, 03:59 AM
I am in the process of producing a CO2 heat pump.
Do you know were I can find a 9Kw
compressor?

I have contacted automotive companies and they do not have CO2 units avalible for sale yet.
Thanks

Hi Richard have a look at this

http://www.danfoss.com/NewsAndEvents/Archive/Refrigeration+News/2006.htm?ArticleID=%7BB30CA134-E236-4A6C-9B9F-BE3FC9A21E31%7D

Regards Norm

Rob S
26-03-2008, 01:39 AM
http://www.r744.com/welcome.php
http://www.bock.de/en/home.html
http://www.youtube.com/watch?v=x-BRGuJbiKw&feature=related

What your looking for?

Peter_1
31-03-2008, 07:53 AM
I am in the process of producing a CO2 heat pump.
Do you know were I can find a 9Kw
compressor?

I have contacted automotive companies and they do not have CO2 units avalible for sale yet.
Thanks

Bitzer (Germany) has CO2 piston compressors and also Dorin (Italy)