Type II — High-Pressure第 130 / 240 题
A technician is charging an R-410A system that uses a near-azeotropic blend. To keep the blend's composition correct, how should refrigerant be removed from the cylinder during charging?
a.As vapor only, from the top of an upright cylinder
b.By venting a little first to purge the cylinder
c.As vapor into the high side while running
d.As liquid (cylinder inverted or using the liquid port), often metered to avoid slugging the compressor
解析
Zeotropic and near-azeotropic blends like R-410A must be charged as liquid so all components leave the cylinder in the correct proportion; removing vapor would fractionate the blend. Liquid is typically drawn from an inverted cylinder or a liquid valve and metered or flashed to vapor before it reaches the compressor to prevent slugging. Charging vapor from the top can change the blend's composition.
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