Heat rejection factor (HRF) for R-12/R-22 at 40°C condenser and 5°C evaporator In typical comfort-cooling applications with R-12 or R-22 and operating conditions Tc ≈ 40°C and Te ≈ 5°C, the heat rejection factor (ratio of condenser heat rejected to net refrigeration effect) is approximately:

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:

• Refrigerants: R-12 or R-22 in legacy/typical textbook examples.
• Operating conditions: condenser about 40°C, evaporator about 5°C.
• Steady vapor-compression cycle with moderate superheat/subcooling.

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