In an air conditioning system with given return and supply air temperatures, which statement is most correct regarding the evaporator coil?

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Multiple Choice

In an air conditioning system with given return and supply air temperatures, which statement is most correct regarding the evaporator coil?

As the air passes over the evaporator coil, it encounters a very cold surface—the coil is cooled by the refrigerant. If the coil surface is below the air’s dew point, moisture in the air condenses on the coil and is drained away. This removes moisture from the air, so the air leaving the coil (the supply air) is both cooler and drier than the air entering it (the return air). That means its relative humidity is lower after passing through the evaporator. The other statements can’t be reliably determined from the given temperatures: the refrigerant type isn’t fixed by temperatures alone, suction pressure is typically lower than discharge pressure, and the supply air is generally cooler (and thus has a lower dry-bulb temperature) than the return air.

As the air passes over the evaporator coil, it encounters a very cold surface—the coil is cooled by the refrigerant. If the coil surface is below the air’s dew point, moisture in the air condenses on the coil and is drained away. This removes moisture from the air, so the air leaving the coil (the supply air) is both cooler and drier than the air entering it (the return air). That means its relative humidity is lower after passing through the evaporator. The other statements can’t be reliably determined from the given temperatures: the refrigerant type isn’t fixed by temperatures alone, suction pressure is typically lower than discharge pressure, and the supply air is generally cooler (and thus has a lower dry-bulb temperature) than the return air.

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