Difficulty: Easy
Correct Answer: 1.25
Explanation:
Introduction / Context:
The heat rejection factor (HRF) relates the condenser heat load to the net refrigeration effect (evaporator load). It helps size condensers and cooling towers from known refrigeration capacities.
Given Data / Assumptions:
Concept / Approach:
By definition HRF = Q_H / Q_L = 1 + W/Q_L. For many standard conditions with R-12 or R-22, the compressor work fraction W/Q_L is around 0.2–0.3, giving HRF ≈ 1.2–1.3. Thus, a commonly cited design value near these temperatures is about 1.25.
Step-by-Step Solution:
Verification / Alternative check:
Manufacturer data for similar conditions often show condenser loads ≈ 1.2–1.35 times the evaporator load, supporting 1.25 as a round design figure.
Why Other Options Are Wrong:
2.15 and 5.12 are far too high for these conditions, implying unrealistically large compressor work.1.00 would mean zero compressor work, impossible.1.60 is above typical range at these temperatures.
Common Pitfalls:
Confusing HRF with compressor heat ratio or using kW/ton multipliers incorrectly. Always compute HRF from energy balance.
Final Answer:
1.25
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