Unformatted text preview: W INDIAN INSTITUE or TECHNOLOGY Date: .. FN/AN Time: 2 hours ‘ Full Marks: .60 No. of Students: 200 ,
Spring MidSemester Examination, 2009 Mechanical Engineering Subject No.: ME22002
2"6 Year B.Tech (H) .Subject Name: Thermodynamics
Answer all the questions. Marks for the questions are shown on the margin. In situations involving air, air can‘be assumed as an ideal gas with
constant specific heats of cp=1.004 kJ/kgK and cv=0.717 kJ/kgK. 1. Air in a piston/cylinder arrangement has a linear spring, shown in
figure, and is at 200 kPa, 300 K, with a volume of 0.5 m3. If the piston is
at the stops, the volume is 1 m3 and a pressure of 400 kPa is required.
The air is'then heated from the initial state to 1500 K by a 1900 K
reservoir. Find the total irreversibility in the process, assuming
surroundings are at 20°C. [14] 2. A rigid tank of volume V contains air at pressure P and temperature
T (K). It is connected to a pistoncylinder arrangement through a valve. A
pressure of P1 (P8P) is maintained in the cylinder due to the weight of
the piston and atmospheric pressure. Initially the piston is at the bottom of the cylinder. Then
the valve is opened and the air undergoes a reversible adiabatic process. Estimate: a) Final temperature of air in the tank and cylinder. b) Work done during the process.
Consider the valve is opened from the same initial condition and the process is executed with
reversible heat transfer such that the temperature of air remains constant throughout. What will be the final volume? What is the amount of heat transfer? [8+6] 3. A 200 m3 rigid tank initially contains atmospheric air at 100 kPa
and 300 K and is to be used as a storage vessel for compressed air at T k
an 1 MPa and 300 K. Compressed air is to be supplied by a compressor .
(C) (as shown in the figure) that takes in atmospheric air at P0 = 100 a kPa and To = 300 K. Kinetic and potential energy effects may be neglected. General form of relevant governing equation and its simplified form for the situation on hand must be clearly stated. T
Clearly identify the chosen control mass/volume. .. Determine the minimum work requirement (in kJ) for this process. [15] 4. Air enters a diffuser, a steady flow device, at 100 kPa, 300 K with a velocity of 200 m/s. The flow decelerates to 20 m/s at the exit of the diffuser. The inlet crosssectional area of the
diffuser is 100 mm2 and the exit area is 860 mmz. Neglecting potential energy and heat transfer
effects, determine the pressure (in kPa) and temperature of the air (in K) at the exit. If the air undergoes an isothermal expansion process in the diffuser, find the exit pressure (in
kPa) and heat transfer during the process. [9+8] ___________________________________———————‘—— End of Paper ...
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