Question

1. 0.3 kg of nitrogen gas at 100 kPa and 40°C is contained in a cylinder. The piston is moved compressing
nitrogen until the pressure becomes 1 MPa and temperature becomes 160°C. The work done during
the process is 30kJ. Calculate the heat transfer by the nitrogen to the surroundings. C of the Nitrogen
is 0.75 kJ/kg-K​

Answer 1

Answer:

3

Explanation:

Given 0.3 kg of nitrogen gas at 100 kPa and 40°C is contained in a cylinder. The piston is moved compressing

nitrogen until the pressure becomes 1 MPa and temperature becomes 160°C. The work done during

the process is 30 kJ. Calculate the heat transfer by the nitrogen to the surroundings. C of the Nitrogen

is 0.75 kJ/kg-K

Given mass of nitrogen m = 0.3 kg

Before compression temperature = 40 degree C = 40 + 273 = 313 K

After compression temperature = 160 degree C = 160 + 273 = 433 K

Now work done during compression will be W = - 30 kJ (negative because it is supplied from outside)

According to first law of thermodynamics,

Q = Δ U + W

   = (U2 – U1) + W

    = mcν (T2 – T1) + W

   = 0.3 x 0.75 (433 – 313) – 30

   = 0.3 x 0.75 x 120 – 30

= 27 – 30

= - 3 KJ

So heat transfer during the process will be 3 K J

Answer 2

Answer:

heat rejected to the surrounding is 3kj