mee3223 - assignment 2
DESCRIPTION
Q1. A water-cooled compressor consumes 150 kW of power when compressing refrigerant-134a from an inlet state of 140 kPa, 10C to an outlet state of 1000 kPa, 40C, as shown in Figure Q1. A heat loss amounting to 40 kW occurs during this process. What is the mass flow rate (in kg/s) of the refrigerant through the compressor? Figure Q12. A turbine is operated at part load by throttling a 1.5 kg/s steam supply at 2 MPa, 300°C down to 1.2 MPa before it enters the turbine, and then exits the turbine at 10 kPa. If the turbine produces 1 MW of power, find the quality and temperature of the steam at the turbine exit. Figure Q23. (a) A steam power plant consumes coal at a rate of 80000 kg/h while producing 200 MW of power output. Determine the overall efficiency of this plant if the heating value of the coal is 30,000 kJ/kg.(b) An automobile engine consumes fuel with a heating value of 44,000 kJ/kg and a density of 0.8 kg/L. If it consumes this fuel at a rate of 30 L/h while delivering 65 kW of power to the wheels of the automobile, determine the efficiency of this engine.4. Refrigerant-134a enters the condenser of a residential heat pump at 800 kPa and 35°C and leaves at 800 kPa as a saturated liquid as shown in Figure Q4. If the at mass flow rate of the refrigerant is 0.02 kg/s while the compressor consumes 1.3 kW of power. Obtain(a) the COP of the heat pump and, (b) the rate of heat absorption from the outside air.TRANSCRIPT
MEE3223: THERMODYNAMICS 2
January 2016 Semester
Assignment 2
Name: _________________________________
Student ID: _____________________________
Questions Marks
Q1
Q2
Q3
Q4
Total
MEE3223: THERMODYNAMICS 2
DUE DATE: 22/04/2016ANSWER ALL QUESTIONS
Q1 A rigid tank is divided into two compartments by a partition. One compartment contains 3 kmol of N2 at 600 kPa and the other compartment contains 7 kmol of CO2 at 200 kPa. Now the partition is removed, and the two gases form a homogeneous mixture at 300 kPa. What is the partial pressure of N2 in the mixture?
Q2 A rigid tank contains 2 kmol of N2 and 6 kmol of CH4 gases at 200 K and 12 MPa. Estimate the volume of the tank, using (a) the ideal-gas equation of state, and (b) Kay’s rule.
Note: Tcr,N2 = 126.2 K, Tcr,CH4 = 191.1 K, Pcr,N2 = 3.39 MPa, Pcr,CH4 = 4.64 MPa
Q3 (a) The air in a room has a dry-bulb temperature of 22°C and a wet-bulb temperature of 16°C. Assuming a pressure of 100 kPa, determine (a) the specific humidity, (b) the relative humidity, and (c) the dew-point temperature.
Note: Use the appropriate equations to solve the above. Do not use the psychrometric chart.
(b) Air enters a window air conditioner at 1 atm, 30°C, and 85 percent relative humidity at a rate of 12 m3/min, and it leaves as saturated air at 15°C. Part of the moisture in the air that condenses during the process is also removed at 15°C. Determine the rates of heat and moisture removal from the air.
Q4 (a) One kilogram of butane (C4H10) is burned with 25 kg of air that is at 30°C and 90 kPa. Assuming that the combustion is complete and the pressure of the products is 90 kPa, determine (a) the percentage of theoretical air used and (b) the dew-point temperature of the products.
(b) Methane (CH4) is burned with dry air. The volumetric analysis of the products on a dry basis is 5.20 percent CO2, 0.33 percent CO, 11.24 percent O2, and 83.23 percent N2. Determine (a) the air–fuel ratio and (b) the percentage of theoretical air used.