Chapter 3 Properties of Refrigerants

All study questions from the end of Chapter 3.

What is one advantage to having evaporator pressures higher than atmospheric pressure?

{c.} Higher pressures keep air out of the system. ref (3-5)

What are two refrigerants that are blended to create a new refrigerant with its own properties called?

{b.} A zeotrope or an azeotrope. ref (3-1, 3-2)

Discharge temperature should not be so high it...

{b.} causes breakdown of the compressor lubricating oil. ref (3-6, 3-7)

What factor do you multiply the mass flow rate (lbs./min.) by to determine the vapor flow rate through the compressor?

{b.} Specific volume (cubic ft./lb.). ref (3-10, 3-11)

EQ: lb./min x ft^3/lb. = ft^3/min (CFM)

Three factors to consider when choosing a refrigerant are...

{c.} cost, availability, and safety. ref (3-4, 3-11, 3-12)

How much does the pressure of trapped ammonia liquid change?

{b.} 100 to 150 psi per degree Fahrenheit increase. ref (3-14)

What is one positive characteristic of most halocarbon refrigerants?

{b.} They are not generally flammable. ref (3-19)

A slight leak in a fitting on a HCFC-22 system causes the halide torch flame to...

{c.} turn green. ref (3-21)

If a system using reciprocating compressors has the evaporator temperature decreased, what happens to the theoretical discharge temperature? (Assume constant condensing pressure).

{a.} Discharge temperature rises. Ref (3-9)

What would the theoretical discharge temperature be for an ammonia system with an evaporator temperature of 0°F and a condensing temperature of 93°F?

{d.} 242°. ref (3-9)

TRUE/FALSE: Decreased evaporating temperature is a direct symptom of air in an ammonia system?

{d.} False. ref (2-17)

Which refrigerant was the first to be phased out by Montreal Protocol?

{b.} CFC-12. ref (3-22, 3-23)

As the ratio between the evaporator and condensing pressure increases, ...

{c.} the theoretical discharge temperature increases. ref (3-9)

Refrigerant leaks are detected using either X on ammonia or Y for CFCs and HCFCs.

{b.} a sulfur stick and an electronic leak detector. ref (3-18, 3-21)

The primary reason for concern about HCFC-22 concentration in an engine room is…

{c.) oxygen deprivation. ref (3-20, 3-21)

A cartridge type gas mask may legally be used for personal protection from ammonia exposure when…

{c.} the type of the hazard is known, and the concentration is known and is less than IDLH. ref (3-18)

The published lower explosive limit for ammonia is…

{c.} 16%. ref (3-17)

Under normal conditions, an ammonia vessel should only be filled…

{b.} to 80%full of liquid. ref (3-14)