Molecular Physics | Thermodynamics Answers

4. A fluid system undergoes a non-flow frictionless process from 4.5 ft 3 to a final volume 1.5 ft 3 in

accordance with the defining relation P= 60/V + 30 psi, where volume in ft 3 . During the process the

system reject 30 BTU of heat. Determine the change in enthalpy and internal energy.

3. During the execution of a reversible non-flow process the work is -156.2 KJ if V 1 =0.845 and the

pressure varies as P=-730 V +690 KPa, where volume V is in m 3 . Find the final volume.

2. The work done by substance in a reversible non-flow manner in accordance with V=700/P where V is

volume in m 3 , P is absolute pressure in Kpaa. Evaluate the work done on or by the substance as the

pressure increases from 85 to 810 KPa

1. Air flow steadily at the rate of 0.95 kg/s through air compressor, entering at 7.5 m/s speed, 95 Kpaa

pressure and 0.95 m 3 /kg specific volume and leaving 20 m/s, 725 kpaa and 0.19 m 3 /kg. the internal

energy of the air leaving is 100 KJ/kg greater than that of the air entering. Cooling water in the

compressor jacket absorbs heat from the air at the rate of 60 kJ/s. compute the steady flow work in kW.

The pressure leads from Pitot-static tube mounted on an aircraft were

connected to a pressure gauge in the cockpit. The dial of the pressure gauge is calibrated to read

the aircraft speed in m/s. The calibration is done on the ground by applying a known pressure

across the gauge and calculating the equivalent velocity using incompressible Bernoulli’s equa￾tion and assuming that the density is 1.224 kg/m3.

The gauge having been calibrated in this way the aircraft is flown at 9200 m, where the

density is 0.454 kg/m3 and ambient pressure is 30 kN/m2. The gauge indicates a velocity of

152 m/s. What is the true speed of the aircraft ?

A 10 pole, 50 Hz, Y connection 3-phase induction motor having a rating of 60 kW and 415V.

The slip of the motor is 5% at 0.6 power factor lagging. If the full load efficiency is 90%,

calculate:

(i) Input power

(ii) Line current and phase current

(iii) Speed of the rotor (rpm)

(iv) Frequency of the rotor

(v) Torque developed by the motor (if friction and windage losses is 0)

An ideal gas has 𝑛 moles and is monatomic with 𝛾 = 5/3. It is contained in a piston cylinder and undergoes a Carnot engine cycle between isotherms at 𝑇𝐿 and 𝑇𝐻, between states labelled 𝑎 to 𝑑 as shown on the PV diagram. The values shown on the axes are an example. During the process bcd (from b to c and then c to d) the gas does work 𝑊𝑏𝑐𝑑. The internal energy in state b is 𝑈.Derive an expression for the ratio 𝑊𝑏𝑐𝑑/𝑈𝑏 in terms of 𝑇𝐿 , 𝑇𝐻, 𝑉𝑎, and 𝑉.

. A rigid tank contains air at 500 kPa and 150 degree C. As a result of heat transfer to the surroundings, the temperature and pressure inside the tank drop to 65 degree C and 400 kPa respectively. Determine the boundary work done during the process