The question is on the imag

QUESTION 1 (10 marks)

Calculate the rate at which body heat is conducted through the clothing of a skier in a steady-state process, given the following data: the body surface area is 1.8 m2, and the clothing is 1.0 cm thick; the skin surface temperature is 33􏰓 °C and the outer surface of the clothing is at 1.0 °C; the thermal conductivity of the clothing is 0.040 W/m.K

QUESTION 2 (15 marks)

A loaf of freshly baked bread is left to cool on a cooling rack. The dimension of the loaf is as described in the Figure 1, and its surface temperature is 120 °C. The temperature of the air is 20 °C, and the convection coefficient from the loaf to air is 10 W/m2K. Emissivity of the bread is 0.76, and its conductivity is 0.121.

loafFigure1: Loaf of Bread

QUESTION 3 (10 marks)

An engine transfers 20.0 × 103 J of energy from a hot reservoir during a cycle and transfers 15.0 × 103 J as exhaust to a cold reservoir. Calculate the:

1. amount of work done in one cycle (4 marks)
2. efficiency of the engine (6 marks)

QUESTION 4 (5 marks)

Explain why the entropy of the universe increases in all real processes?

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christopher , 6 Years ago

Grade 12th pass