How does a scroll compressor compress refrigerant vapor?
- Two scrolls spin in opposite directions, throwing gas to the outside
- A piston moves the gas past reed valves on each stroke of the crank
- A vane rotor sweeps gas around the inside of a round cylinder
- One scroll orbits against a fixed scroll, squeezing gas inward
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D. One scroll orbits against a fixed scroll, squeezing gas inward
A scroll set has one stationary and one orbiting spiral. Pockets of gas are trapped at the outer edge and pushed inward to the center discharge port as their volume shrinks. Neither scroll spins like an impeller.
Reference: Scroll compressor operation
What is meant by the temperature split (TD) of an air-cooled condenser?
- Leaving air temperature minus entering air temperature
- Discharge line temperature minus liquid line temperature
- Condensing temperature minus liquid line temperature
- Condensing temperature minus entering air temperature
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D. Condensing temperature minus entering air temperature
Condenser split compares the saturated condensing temperature, taken from head pressure, with the air entering the coil. Condensing temperature minus liquid line temperature is subcooling, a different measurement.
Reference: Air-cooled condensers; condenser split
Why is the refrigerant charge on a capillary tube reach-in weighed in to the nameplate amount?
- The receiver must be filled to exactly half its volume
- There is no receiver, so the charge is critical
- The capillary tube closes if the charge is too small
- The compressor has no way to tolerate any subcooling
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B. There is no receiver, so the charge is critical
A cap tube system has no receiver to hold surplus liquid and no valve to regulate flow, so a few ounces too much or too little changes pressures and superheat noticeably. The charge is therefore weighed in.
Reference: Capillary tube systems; critical charge