QUIZ (2) First and Second Law of Thermodynamics

QUIZ (2) First and Second Law of Thermodynamics (1) Refrigerant 134a is throttled from the saturated liquid state at 800 kPa to a pressure of 140 kPa. Find changes in internal energy, temperature, enthalpy and specific volume. (2) A heat pump is used to maintain a house at a constant temperature of 240C. The heat lost through the walls and windows is 60000kJ/h whereas the heat generated in the house by all means is 4000 kJ/h .For a COP of 2.5, determine the power input to the heat pump. (3) A piston cylinder device initially contains 0.5 m3 of a gas (Cp=1.04 kJ/kg-K, R=297J/kg-K) at 400 kPa and 270C. An electric heater outside the cylinder is switched on. It passes 5A current for 5minutes from a 120V source. The gas expands at constant pressure and heat lost to the surroundings is 2800J.What is the final temperature of the gas QUIZ (2) First and Second Law of Thermodynamics

A steam power plant with a power output of 200 MW consumes coal at a rate of (1) 60000 kg/h. The heating value of the coal is 30000 kJ/kg, determine the thermal efficiency of the power plant (2) Air at 80 kPa and 127oC enters an adiabatic diffuser steadily at a rate of 6000 kg/h and leaves it at 100 kPa. The velocity of the air steam is decreased from 230 m/s to 30 m/s at it passes through the diffuser. Find the exit temperature of air and the exit area of the diffuser. (3) A piston cylinder device contains 25 grams of saturated water vapor at 300 kPa. An electrical heater is placed within the device. The heater is switched on and it draws a current of 5 Amperes from a source of 120 V for 5 minutes. A heat loss of 30 kJ occurs from the device to the surroundings. Determine the final temperature of the water.