A technician takes the following readings on an R-404A refrigeration system: Head pressure =205 psig Suction pressure = 30 psig Condenser outlet temperature 5 80°F Evaporator outlet temperature = 10°F Using the pressure/temperature chart in Figure 10.25, find the condenser subcooling and evaporator superheat amounts.
The correct answer and explanation is:
To determine the condenser subcooling and evaporator superheat for the R-404A refrigeration system, follow these steps:
- Convert pressures to temperatures using the R-404A pressure-temperature (P-T) chart:
- Head pressure: 205 psig
- According to the R-404A P-T chart, 205 psig corresponds to a saturation temperature of approximately 90°F.
- Suction pressure: 30 psig
- According to the R-404A P-T chart, 30 psig corresponds to a saturation temperature of approximately -5°F.
- Head pressure: 205 psig
- Calculate condenser subcooling:
- Formula: Subcooling = Saturation temperature (from P-T chart) – Actual condenser outlet temperature
- Calculation:
- Saturation temperature: 90°F
- Condenser outlet temperature: 80°F
- Subcooling = 90°F – 80°F = 10°F
- Calculate evaporator superheat:
- Formula: Superheat = Actual evaporator outlet temperature – Saturation temperature (from P-T chart)
- Calculation:
- Evaporator outlet temperature: 10°F
- Saturation temperature: -5°F
- Superheat = 10°F – (-5°F) = 15°F
Summary:
- Condenser subcooling: 10°F
- Evaporator superheat: 15°F
These calculations are essential for assessing the performance and efficiency of the refrigeration system. Proper subcooling and superheat values indicate that the system is operating within its designed parameters.
*Note: The pressure-temperature values are based on standard R-404A refrigerant properties. For precise measurements, refer to the specific P-T chart provided by the refrigerant manufacturer.*