Asingle-square threaded 35-mm power screw is 35 mm in diameter with a pitch of 5 mm. a vertical load on the screw reaches a maximum of 5 kn. the coefficients of friction are 0.06 for the collar and 0.09 for the threads. the frictional diameter of the collar is 45 mm. find the overall efficiency and the torque to "raise" and "lower" the load. repeat this problem if acme screw is used in this design.

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.