A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -30 ℃ by rejecting its waste heat to cooling water that enters the condenser at 18 ℃ at a rate of 0.25 kg/s and leaves at 26 ℃. The refrigerant enters the condenser at 1.2 MPa and 65 ℃ and leaves at 42 ℃. The inlet state of the compressor is 60 kPa and -34 ℃ and the compressor is estimated to gain a net heat of 450 W from the surroundings. Determine the quality of the refrigerant at evaporator inlet.

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]

Consider airflow over a flat plate of length l = 1.5 m under conditions for which transition occurs at le = 0.9 m based on the critical reynolds number, re, e = 5 x 10. evaluating the thermophysical properties of air at 400 k, determine the air velocity. (hint: use the tables to find the properties of air)