Arefrigerator using r-12 as the working fluid keeps the refrigerated space at −15℃ in an environment at 30℃. you are asked to upgrade this refrigerator by replacing r-12 with the ozone-friendly r-134a or ammonia.

a. what are the temperatures and pressures of the three refrigerants at every stage of the cycle?

b. in / what are work input and heat removal for each refrigerant?

c. what is the cop for each refrigerant? based on cop only, which one would you pick?

d. based on other engineering considerations, which refrigerant would you pick? why?

When at a point two solid phase changes to one solid phase on cooling then it is known as a) eutectoid point b) eutectic point c) peritectic point d) peritectoid point

Asingle-geared blanking press has a stroke of 200 mm and a rated capacity of 320 kn. a cam driven ram is assumed to be capable of delivering the full press load at constant force during the last 15 percent of a constant-velocity stroke. the camshaft has an average speed of 90 rev/min and is geared to the flywheel shaft at a 6: 1 ratio. the total work done is to include an allowance of 16 percent for friction a) estimate the maximum energy fluctuation b) find the rim weight for an effective diameter of 1.2 m and a coefficient of speed fluctuation of 0.10

Atmospheric air has a temperature (dry bulb) of 80° f and a wet bulb temperature of 60° f when the barometric pressure is 14.696 psia. determine the specific humidity, grains/lb dry air. a. 11.4 c. 55.8 d. 22.5 b. 44.1