Starting Torque Requirement for Compressors and Refrigerants

Starting torque requirement is an important consideration when selecting a suitable compressor for a refrigeration system. The starting torque of a compressor determines its ability to start and operate smoothly under different operating conditions. In the given question, we need to determine which refrigerant has the least starting torque requirement for an appropriate sized compressor to produce the same refrigerating effect.

1. R134a:
- R134a is a commonly used refrigerant in many applications, including automotive air conditioning systems.
- It has a medium to high starting torque requirement due to its operating characteristics.
- The compressor for R134a needs to be adequately sized to handle the starting torque requirements.

2. R152a:
- R152a is a hydrofluorocarbon (HFC) refrigerant used as a replacement for chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).
- It has a lower starting torque requirement compared to R134a.
- The appropriate-sized compressor for R152a can have a lower starting torque requirement.

3. R600a:
- R600a, also known as isobutane, is a hydrocarbon refrigerant commonly used in household refrigerators and freezers.
- It has a relatively low starting torque requirement due to its properties.
- The appropriate-sized compressor for R600a can have a lower starting torque requirement compared to R134a and R152a.

4. R12:
- R12, also known as dichlorodifluoromethane, was a widely used refrigerant in the past but has been phased out due to its ozone depletion potential.
- It had a moderate starting torque requirement.
- The appropriate-sized compressor for R12 had a starting torque requirement higher than R600a but lower than R134a.

Conclusion:
Among the given options, R12 has the least starting torque requirement for an appropriate sized compressor to produce the same refrigerating effect. R600a also has a relatively low starting torque requirement, followed by R152a and R134a. It is important to choose the right refrigerant and compressor combination to ensure efficient and reliable operation of the refrigeration system.