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Old 04-12-15, 09:14 PM   #1
philb
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Default Super heating the AC refrigerant returns 40-60% better efficiency

By "Super Heating" the refrigerant with the aid of the Solar Collector, we are able to increase the temperature difference between the condenser coil and the ambient temperature. By creating this difference, Sedna Aire is able to utilize the entire coil face at the condenser which allows for a better heat exchange throughout the entire system.

How is this possible? I don't know much about AC, but I was under the impression the condenser should be kept as cold as possible.

Sedna Aire International > Products > Solar Cool > How it Works

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Old 04-14-15, 09:12 AM   #2
gtojohn
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Doesn't make sense to me. Any heat added has to be rejected by the condenser coils. Extra heat not rejected would then be reduced sub cooling as well as capacity. If you want to add more super heat run your blower on high or turbo.
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Old 04-16-15, 06:10 PM   #3
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This system is a gimmick. The claim is that by raising the subcooling of the liquid refrigerant in the high side of the system, gobs and loads of energy is saved. While the claim is somewhat true, the collector's added heat is only useful in certain conditions. Let me explain.

The system without the collector acts like this outdoors in heating mode: the compressor sucks in low pressure, low temperature gaseous refrigerant from the outdoor heat exchanger. It pumps this gas indoors, in a highly superheated state. This hi-temp, hi-pressure gas gives its heat up to the indoor hx, and in the process condenses into a high pressure liquid. This liquid then travels slowly outdoors through the liquid line, where it cools and subcools below its condensation temperature. It then spews through a metering device, where it immediately boils and evaporates in the outdoor hx. This low-temp, low-pressure fog turns to all gas at a constant low temperature until it is all gaseous again. This cold gas gathers heat from outdoors, and superheats above its boiling point. It travels rather quickly to the compressor, completing the cycle. In aircon mode, the heat exchangers swap sides, from indoor condenser and outdoor evaporator to indoor evaporator to outdoor condenser.



The gimmick in the system is this:

1. With the collector in the system, the system cannot help at all in heating mode, unless it is running hotter than the discharge temperature of the compressor. This temperature must be well above indoor temperature to force any heat indoors. So if it is down around freezing outdoors, the collector has to be operating above 95 degrees F or 35 degrees C to help. Otherwise, it would be absorbing hot discharge gas heat from the compressor, robbing energy. On a cool, sunny day, this is possible. Now, if the collector was plumbed in after the outdoor evaporator, it could superheat the cold gas to above outdoor temperature before it was sucked into the compressor. The added superheat would definitely help heat the house, but on a cool, sunny day, the enormous amount of superheat at the discharge of the compressor could fry eggs, valves, and motor windings.... or maybe just heat the house better. Gas travels fast.

2. In aircon mode (as shown), when the collector operates, it super-duperheats the hot discharge compressor gas, which forces a pressure increase in the outdoor side of the circuit. This increase in pressure moves the temperature of condensation higher. On a 95F (35C) degree day, the compressor may be belting out 150 degree gas. The condensation temperature without the collector would normally be around 105-110F with a decent amount of subcooling, maybe 10 degF. With the collector adding heat, the pressure would increase from normally 400-425 psi upwards towards 600 psi! Upon reaching the heat exchanger, this super-hot, super-pressure gas would immediately dump all its extra heat into the outdoor air, and condense at a higher temperature. Yes, by the time it slowly made its way through the heat exchanger, it would be ultra subcooled, being the same (or maybe greater than) 100 degF. With 500 psi of pressure, the liquid would have 35 degF of subcooling. If it all made its way to the evaporator, it would be begging to vaporize.

These two examples are worst-case scenarios. During swing seasons, the collector could make the unit operate at higher efficiency while the sun was shining. Typically, these are not energy-hog days for the unit. With an intelligent microcomputer controlling everything, a measurable amount of energy might be saved. But under the conditions of the second example, there is a high possibility of system failure due to extremely high pressure outdoors.

This is exactly what has been happening to owners of these systems. The units work fine until that heat wave hits around the 4th of July. On that 102 degree day, the unit runs away into shutdown and the "service me now" codes start appearing on the display. Depending on what burned up, the tech may repair or replace the victim....

Seeing as how these systems are not taking over the market, I imagine most of them are being replaced when they burn up or pop.
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Old 04-17-15, 01:41 AM   #4
NiHaoMike
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Maybe the intent is better efficiency in heating mode?
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To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...
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Old 04-17-15, 08:39 AM   #5
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Heating mode would be the only mode this could work. it would be more efficient if the collector were after the condenser coil. The coils at low temp can already absorb heat from the air some what efficiently. The solar could then still add more before the metering device. What their site claims is using it for cooling. But they don't state any efficiency ratings. They don't say it but I think they are using the solar heat as a compressor, heating the refrigerant and there by raising the pressures. Works if you're using ammonia or propane refrigerator technology. Im pretty sure you can't use ammonia in residential a/c.
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Old 04-19-15, 05:37 AM   #6
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What happens when the sun is not warming the collector ? ( Night or cloudy days . )

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