discs/drums are 4.0 kg steel. Fürther assuthe Dotrmasses ctu temperature increas

Question

discs/drums are 4.0 kg steel. Fürther assuthe Dotrmasses ctu temperature increase in the brake assembly if no heat is lost to the environm ent. Two kg water at 120°C with a quality of 25% has its temperature raised 20°C in a constant volume process. What are the heat transfer and work in the process? S. A piston/óylinder contains 0.1 kg water at 500 C, 1000 kPa. The piston has a stop at half the original volume. The water now cools to room temperature 25'C Sketch the possible water states in a P-v diagram. b. Find the final pressure and volume c. Find the heat transfer and work in the process a. Nitrogen at 300 K, 3 MPa is heated to 500 K. Find the change in enth

Explanation / Answer

Ans 4

Steam quality x = 0.25

At initial conditions

Temperature T = 120 °C (saturated steam)

Specific volume v1 = vf + x*(vg - vf)

= 0.001060 + 0.25*(0.891860 - 0.001060)

= 0.223760 m3/kg

Specific internal energy u1 = uf + x*(ug - uf)

= 503.480 + 0.25*(2529.24 - 503.480)

= 1009.920 kJ/kg

At final conditions T2 = 120 + 20 = 140 °C

For constant volume process

v1 = v2

New steam quality

x2 = ( v2 - vf2) / (vg2 - vf2)

= ( 0.223760 - 0.001080) / (0.50885 - 0.001080)

= 0.4386

New internal energy

u2 = uf2 + x2*(ug2 - uf2)

= 588.72 + 0.4386*(2550.02 - 588.72)

= 1448.95 kJ/kg

From the first law of thermodynamics

du = dQ + dW

For constant volume process

dW = - PdV = 0

du = dQ

m x (u2 - u1) = Q

Q = 2 kg x (1448.95 - 1009.920) kJ/kg

= 878.06 kJ

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