by Ron Walker
As refrigerant absorbs heat it increases in pressure inside the EVAPORATOR:
The high pressure refrigerant goes through the orifice(flow control device), vaporizes and rises is pressure again. The system is designed to keep that pressure just right, though, so that the temperature of the vaporizing (boiling) refrigerant will remain above 32°F and somewhere below 55°F. That is "cold" enough to absorb a lot of heat from an 80°F room air flowing over the evaporator. If it were below 32°F, then any moisture that it causes to condense on the tubing would freeze on the tube and that would be bad. A lot of it would even restrict the air flow through the evaporator and actually insulate the tubing so that it slowed the boiling of the refrigerant on the inside of the tube. So the equipment manufacturer designs it to be above 32°F and blows just enough air over it, with just enough cooling coil surface, with just the right size of flow restrictor (orifice) to drop the temperature of the air going past it about 20°F. If an 80°F room air passes through the evaporator, then it comes out the supply grills at about 60°F.
It is designed so well that a lot of "cooling effect" is still left in the refrigerant as it returns back into the compressor and this cools off the hot motor windings and mechanical parts just before it gets compressed again to start the new cycle though the system. But, it is designed so well that no liquid is left to dump into the compressor, because liquid will not compress and it would break the valves inside the compressor. You see, now, that the pieces all have to fit together just like the manufacturer planned it.
Too much refrigerant or too little would prevent that "just right combination" from happening. Thus, the refrigerant "charge" must be right, the parts must be working and they must be kept clean to do the job.
As refrigerant absorbs heat it increases in pressure inside the EVAPORATOR:
The high pressure refrigerant goes through the orifice(flow control device), vaporizes and rises is pressure again. The system is designed to keep that pressure just right, though, so that the temperature of the vaporizing (boiling) refrigerant will remain above 32°F and somewhere below 55°F. That is "cold" enough to absorb a lot of heat from an 80°F room air flowing over the evaporator. If it were below 32°F, then any moisture that it causes to condense on the tubing would freeze on the tube and that would be bad. A lot of it would even restrict the air flow through the evaporator and actually insulate the tubing so that it slowed the boiling of the refrigerant on the inside of the tube. So the equipment manufacturer designs it to be above 32°F and blows just enough air over it, with just enough cooling coil surface, with just the right size of flow restrictor (orifice) to drop the temperature of the air going past it about 20°F. If an 80°F room air passes through the evaporator, then it comes out the supply grills at about 60°F.
It is designed so well that a lot of "cooling effect" is still left in the refrigerant as it returns back into the compressor and this cools off the hot motor windings and mechanical parts just before it gets compressed again to start the new cycle though the system. But, it is designed so well that no liquid is left to dump into the compressor, because liquid will not compress and it would break the valves inside the compressor. You see, now, that the pieces all have to fit together just like the manufacturer planned it.
Too much refrigerant or too little would prevent that "just right combination" from happening. Thus, the refrigerant "charge" must be right, the parts must be working and they must be kept clean to do the job.