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-   -   Improving cooling efficiency? (https://ecorenovator.org/forum/showthread.php?t=7315)

Acuario 06-29-20 06:14 AM

Improving cooling efficiency?
 
I was thinking the other day, in the summer I'm obviously running my heatpump in cooling mode. The compressor is still just doing it's job and compressing gas so generating a lot of heat that then has to be disposed of.

Generally the compressor is wrapped in a nice snug blanket and encased in a small area along with all the rest of the pipework etc. This space gets pretty warm.

My thinking was; what if this space had a fan (like for example a computer PSU fan) and a grill to the outside world so some of the generated heat could be thrown out, hence cooling the area and helping everything run just a bit cooler.

Would this improve efficiency?

Anyone got any thoughts on the subject?

NiHaoMike 06-29-20 09:33 PM

The insulation is there to make sure the oil doesn't cool off too much when it's not running. Some also have crankcase heaters.

jeff5may 06-30-20 02:05 AM

Yes, ventilation will help carry away waste heat. Not a huge amount, but yes it will be helpful.

The most effective thing you can do to increase cooling is to mist the outdoor unit heat exchanger. Any way you slice it, the mist helps. I used to be a skeptic, but not anymore. It seems the dumber and lower seer rating your system is, the more it helps. The variable speed inverter units get a boost, but not as much as an older single speed, cap tube metered unit.

I haven't hooked a mister up yet this year. Where I am (Kentucky USA by fort Knox), the savings don't really stack up until the daily highs rise above body temperature. What I have is a kiddie pool reservoir in the shade, that feeds from the air conditioner drain. If you have soft tap water (I don't, Kentucky tap water is full of lime), you can use that. I have a little submersible fountain pump hooked up to some fine spray nozzles. The pump runs off a wind vane switch mounted on the discharge from the outdoor unit. When the unit turns on its fan, the pump starts misting.

You can read this and read that about it, or just do it and see if it works for you. I noticed the misting in action, and experimented with it, a dozen or more years ago, with window shakers. The outdoor fan on about every one has a ring around it that slings condensate on the outdoor HX. I noticed that the hotter it gets outside, the better the water slinger works to drive down supply air temperature indoors. I saw that in the absence of the drain water, the compressor power draw was 20 to 30 percent higher than with the drain water. Inside, the discharge air really depended on the outside temperature. On a hot day, the difference between water and no water cooling was 10 to 15 degF.

The house I'm in now has a 13 seer trane heat pump in it, single speed with txv metering. It does a pretty good job until it gets hot and muggy outside. We're just getting into that time of year now, so I might be setting up the misting rig soon. I'll probably need to find a reservoir, as the one I was using is now a big dog water bowl/bath.

Keeping the outdoor unit in the shade helps, too.

WyrTwister 07-10-20 01:24 AM

The " blanket " around the compressor may also be for sound deadening ?

God bless
Wyr

u3b3rg33k 07-14-20 02:09 AM

if you have a hermetic compressor, it's cooled by the refrigerant. cooling the shell serves no purpose.

WyrTwister 07-14-20 09:44 AM

May not help , but I can not see it hurts ? Always figured they were painted black to help dissipate heat ?

God bless
Wyr

AirConditioner 07-14-20 03:54 PM

Quote:

Originally Posted by WyrTwister (Post 62819)
May not help , but I can not see it hurts ? Always figured they were painted black to help dissipate heat ?

God bless
Wyr

Why did you "figure" that? Black paint doesn't make things "dissipate heat".

As noted all hermetic compressors are cooled by the refrigerant. Any cooling of the small steel case of the compressor will make little to no difference. If this needed cooling then they would come from the factory wrapped in heatsinks, not blankets.

WyrTwister 07-14-20 06:16 PM

Now that I have thought about it a little more , I suppose they are painted for corrosion protection ? After all , they are outside & get wet when it rains .

But everything I have ever read indicates that black radiates heat better than any other color .

True , it might dissipate heat better if it had no paint . But no protection .

God bless
Wyr

u3b3rg33k 07-15-20 02:19 PM

Quote:

Originally Posted by WyrTwister (Post 62826)
Now that I have thought about it a little more , I suppose they are painted for corrosion protection ? After all , they are outside & get wet when it rains .

But everything I have ever read indicates that black radiates heat better than any other color .

True , it might dissipate heat better if it had no paint . But no protection .

God bless
Wyr

Generally black does, and that matters if the primary method of cooling is radiation, and it's in the dark. plenty of compressors are blue/red too. either way the primary method of cooling a hermetic compressor is internal to the shell. otherwise any unit with a factory blanket would die an early death, and that just doesn't happen.

color goes both ways, black will radiate heat faster, AND it will absorb heat faster. plus some colors (pigments) are less resistant to corrosion, or are more toxic.

nokiasixteth 07-16-20 09:00 PM

Quote:

Originally Posted by jeff5may (Post 62772)
Yes, ventilation will help carry away waste heat. Not a huge amount, but yes it will be helpful.

The most effective thing you can do to increase cooling is to mist the outdoor unit heat exchanger. Any way you slice it, the mist helps. I used to be a skeptic, but not anymore. It seems the dumber and lower seer rating your system is, the more it helps. The variable speed inverter units get a boost, but not as much as an older single speed, cap tube metered unit.

I haven't hooked a mister up yet this year. Where I am (Kentucky USA by fort Knox), the savings don't really stack up until the daily highs rise above body temperature. What I have is a kiddie pool reservoir in the shade, that feeds from the air conditioner drain. If you have soft tap water (I don't, Kentucky tap water is full of lime), you can use that. I have a little submersible fountain pump hooked up to some fine spray nozzles. The pump runs off a wind vane switch mounted on the discharge from the outdoor unit. When the unit turns on its fan, the pump starts misting.

You can read this and read that about it, or just do it and see if it works for you. I noticed the misting in action, and experimented with it, a dozen or more years ago, with window shakers. The outdoor fan on about every one has a ring around it that slings condensate on the outdoor HX. I noticed that the hotter it gets outside, the better the water slinger works to drive down supply air temperature indoors. I saw that in the absence of the drain water, the compressor power draw was 20 to 30 percent higher than with the drain water. Inside, the discharge air really depended on the outside temperature. On a hot day, the difference between water and no water cooling was 10 to 15 degF.

The house I'm in now has a 13 seer trane heat pump in it, single speed with txv metering. It does a pretty good job until it gets hot and muggy outside. We're just getting into that time of year now, so I might be setting up the misting rig soon. I'll probably need to find a reservoir, as the one I was using is now a big dog water bowl/bath.

Keeping the outdoor unit in the shade helps, too.

I have a rig and 100ft of pipe. I have been told here geothermal is 250ft per ton. I wonder if i could dig 3 holes each 100 ft deep. Put some hdpe pipe in each hole with a controller that sensed when water changed temps it would flow after exchanging heat. A radiator big enough for adequate air flow intake for the mini split . Basically the air would be pre cooled before going into the mini split . Being i dont have the tools or anything to make a full blown geothermal air conditioner. Wonder if it would be worth the investment or just a waist of time.


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