Which of the following does NOT constitute a desirable characteristic for a working refrigerant_________________?
Show answer Hide answer
Answer: C. good electrical conductor
Explanation
A good working refrigerant must be a poor electrical conductor to prevent electrical short circuits. Hermetic compressors submerge motor windings directly in the refrigerant and oil mixture. Conductive refrigerants would cause electrical arcing and burn out the compressor motor insulation. Desirable refrigerant properties include low boiling point, chemical stability, and non-toxicity. High dielectric strength is essential for refrigerants used in modern hermetically sealed compressor units. Safety standards strictly regulate flammability, toxicity, and electrical properties of working fluids.
Selecting the correct refrigerant ensures safe long-term operation of domestic refrigerators and air conditioners. Electrical safety standards protect technicians and consumers from potential motor burnout hazards. Engineers evaluate dielectric properties before approving new synthetic or natural refrigerants for use. High miscibility with oil helps circulate lubricating oil back to the compressor effectively. Low boiling point ensures the fluid can evaporate at cold temperatures inside the cooling coils. Large latent heat allows the refrigerant to absorb significant heat per unit mass circulated.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. The saturation vapor pressure characteristics of a suitable refrigerant should be_________________?
Show answer Hide answer
Answer: B. higher than atmospheric pressure
A suitable refrigerant should have a saturation vapor pressure higher than atmospheric pressure to prevent air leakage into the system. Operating above atmospheric pressure ensures that any minor flange or valve leak exp...
Q2. Relative coefficient of performance is defined as the ratio of_____________________?
Show answer Hide answer
Answer: A. actual COP/fheoretical COP
Relative coefficient of performance is defined as the ratio of the actual COP to the theoretical Carnot or cycle COP. Comparing actual operating performance against ideal theoretical cycles yields the relative coefficien...
Q3. The coefficient of performance of a domestic household refrigerator typically ranges___________________?
Show answer Hide answer
Answer: B. is more than 1
The coefficient of performance of a domestic household refrigerator is always greater than 1. This means the cooling effect delivered exceeds the electrical energy consumed by the compressor. Thermodynamic efficiency rat...
Q4. Incorporating under-cooling (sub-cooling) into a refrigeration cycle leads to_________________?
Show answer Hide answer
Answer: A. increases COP
Sub-cooling the liquid refrigerant increases the net refrigeration effect without increasing the compression work, thereby increasing the COP. By lowering the liquid enthalpy entering the expansion valve, each kilogram o...
Q5. Vertical lines plotted on a pressure-enthalpy property chart represent constant values of_______________?
Show answer Hide answer
Answer: C. total heat lines
Vertical lines on a pressure-enthalpy property chart represent lines of constant enthalpy or total heat. Property charts plot enthalpy on the horizontal axis and pressure on the vertical axis, making constant enthalpy li...
Q6. At what point in a vapor compression cycle does the minimum temperature happen ?
Show answer Hide answer
Answer: B. evaporator
The minimum temperature in a vapor compression cycle occurs inside the evaporator. Refrigerant absorbs heat at low pressure in the evaporator, maintaining the lowest temperature. Expansion valves drop liquid pressure, in...