Air at 10°c enters a 12-cm-diameter and 5-m-long pipe at a rate of 0.065 kg/s. the inner surface of the pipe has a roughness of 0.22 mm, and the pipe is nearly isothermal at 50°c. determine the rate of heat transfer to air using the nusselt number relation given by (a) eq. 8–66 and (b) eq. 8–71. evaluate air properties at a bulk mean temperature of 20°c. is this a good assumption?

Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 mpa and -10°c at a rate of 0.05 ka/s and leaves at 0.8 mpa and 50°c. the refrigerant is cooied in the condenser to 0.72 mpa and 26'c. it is then throttled to 0.15 mpa. sketch the t-s diagram for the system and evaluate: 6) the rate of heat removai from the refrigerated space (kw), it) the power input to the compressor (kw), ii) the isentropic efficiency of the compressor (%), and iv) the cop of the refrigerator.