Evaporator Systems Flashcards
7 cards from real RSES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Evaporator Systems flashcards as text
What is the primary reason a hot-gas defrost system heats evaporator coils faster than electric defrost?
Answer: Hot gas condenses inside the coil, releasing latent heat directly to the frost
When hot discharge gas condenses in the evaporator, it releases its latent heat of condensation directly to the coil, providing high heat transfer rates.
A plate evaporator used in a beverage cooler develops oil logging. What is the most effective corrective action?
Answer: Increase suction gas velocity by reducing evaporator circuits or raising suction pressure slightly
Oil logging in evaporators is corrected by increasing suction gas velocity, which carries trapped oil back to the compressor through the suction line.
During off-cycle defrost, what limits how completely frost is removed from a low-temperature evaporator?
Answer: The ambient or box temperature may not be warm enough to melt all frost before refrigeration restarts
Off-cycle defrost relies solely on warm air from the refrigerated space, which may not carry enough heat to fully defrost deeply frosted coils in sub-zero applications.
What does a 'starved evaporator' mean in refrigeration terminology?
Answer: The evaporator receives insufficient liquid refrigerant, resulting in high superheat
A starved evaporator receives too little refrigerant, so the refrigerant evaporates early and the remaining coil surface superheats vapor without contributing to cooling.
In a flooded evaporator system, refrigerant level is maintained by a:
Answer: Float valve that admits liquid to maintain a set liquid level
Flooded evaporators use a float valve (low-side or high-side float) to maintain the correct liquid refrigerant level in the evaporator vessel.
Why is it important to pitch evaporator drain pans toward the drain outlet?
Answer: To prevent water from accumulating and refreezing on the pan, causing blockages
Standing water in an improperly pitched drain pan will refreeze, eventually blocking the drain and causing water to overflow into the refrigerated space.
A secondary refrigerant (brine) evaporator system offers which advantage over a direct-expansion system in large industrial plants?
Answer: Reduced refrigerant charge in the system and easier leak detection
Secondary refrigerant systems contain refrigerant only in the central plant equipment, dramatically reducing the total system charge and limiting refrigerant leak exposure.