6. A refrigeration cycle is a reversed heat engine. Which of the following has the maximum value of the co-efficient of performance (COP) for a given refrigeration effect?
Options
A. Vapor compression cycle using expansion valve.
B. Air refrigeration cycle.
C. Vapor compression cycle using expansion engine.
7. The accentric factor of a materical, '?', is defined as ? = -log10(Prsat)Tr-1 = 0.7, where, Prsat = reduced vapor pressure, Tr = reduced temperature. The value of accentric factor is always