Cooling Cycle & Heat Transfer Principles Flashcards
7 cards from real ATP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Cooling Cycle & Heat Transfer Principles flashcards as text
On a pressure-enthalpy (P-h) diagram, the horizontal line representing the evaporation process appears as:
Answer: A horizontal line at constant pressure within the two-phase dome
Evaporation at constant pressure is represented by a horizontal line inside the saturation dome on the P-h diagram.
What is the primary purpose of a liquid-suction heat exchanger (LSHX) in a refrigeration circuit?
Answer: To subcool liquid refrigerant while superheating suction gas
An LSHX transfers heat from warm liquid refrigerant to cool suction gas, increasing subcooling and superheat simultaneously.
When ambient temperature rises significantly, what happens to a system's condensing pressure if the condensing capacity remains fixed?
Answer: Condensing pressure rises because the temperature differential decreases
Higher ambient temperature reduces the temperature differential across the condenser, requiring higher condensing pressure to maintain the same heat rejection rate.
Thermal resistance in a heat exchanger is analogous to which electrical concept?
Answer: Resistance in a resistor (Ohm's Law analogy)
Thermal resistance R = ΔT/Q mirrors Ohm's Law (R = V/I), where temperature difference drives heat flow just as voltage drives current.
Which refrigerant property is most directly responsible for determining the evaporating temperature at a given suction pressure?
Answer: Saturation temperature-pressure relationship
The saturation temperature-pressure relationship (from refrigerant tables or P-T charts) directly links suction pressure to evaporating temperature.
In natural convection, heat transfer is driven by:
Answer: Buoyancy forces caused by fluid density differences due to temperature
Natural convection relies on buoyancy: warmer, less dense fluid rises and is replaced by cooler, denser fluid, creating circulation.
A system operating with excessive suction superheat at the compressor inlet will most likely experience:
Answer: Lower volumetric efficiency and higher discharge temperature
High superheat increases suction vapor specific volume, reducing mass flow per stroke (lower volumetric efficiency) and raising discharge temperature.