Apower cycle operating at steady state receives energy by heat transfer at a rate q_h at t_h = 1800 k and rejects energy by heat transfer to a cold reservoir at a rate q_c at t_c = 600 k. for each of the following cases, determine whether the cycle operates reversibly, operates irreversibly, or is impossible.
a. q._h = 500 kw, q._c = 100 kw
b. q._h = 500 kw, w._cycle = 250 kw, q._c = 200 kw
c. w_cycle = 350 kw, q._c = 150 kw
d. q._h = 500 kw, q._c = 200 kw

Abrake has a normal braking torque of 2.8 kip in and heat-dissipating cast-iron surfaces whose mass is 40 lbm. suppose a load is brought to rest in 8.0 s from an initial angular speed of 1600 rev/min using the normal braking torque; estimate the temperature rise of the heat dissipating surfaces.

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

The higher the astm grain size number, the finer the gran is. a)-true b)-false