A) What is the relation between stress at the tension side and diameter of the fatigue test specimen?
b) What is the unit of the endurance limit?
c) How can the endurance limit for a fatigue analysis be calculated when real material
properties are not available?
d) Why some of the materials perform endurance limit, and some don’t? Give some examples
from each group of material and discuss the reason.

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.