第一章 热力学基本概念

第一章 热力学基本概念

英文习题

1. Expressing temperature rise in different units

During a heating process, the temperature of a system rises by 10℃. Express this rise in temperature in K, ℉ and R.

2. Absolute pressure of a vacuum chamber

A vacuum gage connected to a chamber reads 5.8 psi at location where the atmosphere pressure is 14.5 psi. Determine the absolute

pressure in the chamber.

3. Measuring pressure with a manometer

A manometer is used to measure the pressure in a tank. The fluid used has a specific gravity of 0.85, and the manometer column height is 55 cm, as shown in Fig.1-1. If the local atmospheric pressure is 96

kPa,

determine the absolute pressure within the tank.

4. Measuring pressure with a multi-fluid manometer

The water in a tank is pressurized by air, and the pressure is

measured by a multi-fluid manometer as shown in Fig. 1-2. The tank

is located on a mountain at an altitude of 1400 m where the atmospheric pressure is 85.6 kPa. Determine the air pressure in the tank if h 1=0.1 m, h 2=0.2 m, and h 3=0.35 m. Take the densities of water, oil, and mercury to be 1000 kg/m 3

, 850 kg/m 3

, and 13

600 kg/m 3

respectively.

5. Effect of piston weight on pressure in a cylinder

The piston of a vertical piston-cylinder device containing a gas has a mass of 60 kg and a cross-sectional area of 0.04 m 2

, as shown in

Fig.1-3. The local atmosphere pressure is 0.97 bar, and the gravitational acceleration is 9.81 m/s 2

. (a) Determine the pressure inside the cylinder. (b) If some heat is transferred to the gas and

its volume is doubled, do you expect the pressure inside the

cylinder to change?

6. Burning off lunch calories

A 90-kg man had two hamburgers, a regular serving of French fries, and a 200-ml Coke for lunch. Determine how long it will take for him to burn the lunch calories off (a) by watching TV and (b) by fast swimming. What would your answers be for a 45-kg man?

7. Burning of a candle in an insulated room

A candle is burning in a well-insulated room. Taking the room (the air plus the candle) as the system, determine (a) if there is any heat transfer

during

this

FIGURE 1-1

FIGURE 1-2

FIGURE 1-3

FIGURE 1-4

burning process and (b) if there is any change in the internal energy of the system.

8. Boundary work during a constant-volume process

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

9. Isothermal compression of an ideal gas

A piston-cylinder device initially contains 0.4 m 3

of air at 100 kPa and 80℃. The air is now compressed to 0.1 m 3

in such a way that the temperature inside the cylinder remains constant. Determine the work done during this process.

10. Heat transfer from a person

Consider a person standing in a breezy room at 20℃. Determine the total rate of heat transfer from this person if the exposed surface area and the average outer surface temperature of the person are 1.6 m 2

and 29℃, respectively, and the convection heat transfer

coefficient is 6 W/m 2

.℃ (Fig.1-7)

工程热力学与传热学

第一章 基本概念 习题

Expressing temperature rise in different units

During a heating process, the temperature of a system rises by 10℃. Express this rise in temperature in K, ℉ and R.

2. Absolute pressure of a vacuum chamber

A vacuum gage connected to a chamber reads 5.8 psi at location where the atmosphere pressure is 14.5 psi. Determine the

absolute

习 题

FIGURE 1-1

FIGURE 1-5

FIGURE 1-6

FIGURE 1-7