工程热力学与传热学(双语) 第3章 习题PPT
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习题课
理想气体状态方程的应用
2. 某活塞式压气机向容积为9.5m3的储气箱中 充入空气。压气机每分钟从压力为p0=750mmHg, 温度为t0=15℃的大气中吸入0.2m3的空气。 若充气前储气箱压力表读数为0.5 bar, 温度为t1=17℃。 问经过多少分钟后压气机才能使储气箱内气体的 压力提高到p2=7bar，温度升为t2=50℃。
习题课
理想气体状态方程的应用
11. A cylinder with a capacity of 2.0m3 contained oxygen gas at a pressure of 500KPa and 25℃ initially. Then a leak developed and was not discovered until the pressure dropped to 300KPa while the temperature stayed the same. Assuming ideal-gas behavior. Determine how much oxygen had leaked out of the cylinder by the time the leak was discovered.
Carbon Monoxide 2kg, 77º C 0.7bar Carbon Monoxide
valve
8kg, 27º C 1.2bar
Tank 1
Tank 2
习题课
理想气体的性质和计算
17. A gas has a density of 1.875kg/m3 at a pressure of 1 bar and with a temperature of 15º C. A mass of 0.9kg of the gas requires a heat transfer of 175kJ to raise its temperature from 15º C to 250º C while the pressure of the gas remains constant. Determine (1) the characteristic gas constant of the gas, (2) the specific heat capacity of the gas at constant pressure, (3) the specific heat capacity of the gas at constant volume, (4) the change of internal energy, (5) the work transfer.
习题课
理想气体的性质
14. The electric heating system used in many houses consist of a simple duct with resistance wires. Air is heated as it flows over resistance wires. Consider a 15KW electric system. Air enters the heating section at 100KPa and 17º C with a volume flow rate of 150m3/min. If heat is lost from the air in the duct to the surroundings at a rate of 200W. T2 ? Q=200W determine the exit temperature of air. cP=1.005 kJ/(kg· K)。
习题课
理想气体的热力过程
10. 有一汽缸和活塞组成的系统，汽缸壁和活塞均由绝热 材料制成，活塞可在汽缸中无摩擦地自由移动。初始时 活塞位于汽缸中间，A,B两侧各有1kg空气, 压力均为 0.45MPa，温度同为900K。现对A侧冷却水管通水冷 却，A侧压力逐渐降低。求： （1）压力降低到0.3MPa时， Q A B A，B两侧的体积是多少？ （2）冷却水从系统带走的热量是多少？ （3）整个气体组成的系统熵变是多少？ （4）在p-v 图、T-s 图上大致表示两侧气体进行的过程。 设定值比热容计算。且k=1.4, cv=0.717 k]/(kg· K) 。
习题课
理想气体的性质
13. Five grams of argon gas undergoes a change of state at constant internal energy. Initial pressure and temperature are 6.0 atm and 300K, respectively. The final volume occupied by the gas is three times that occupied initially. Assuming ideal-gas behavior, determine (a) the final temperature of the gas. (b) the final pressure of the gas. (c) the entropy change of the gas due to the change of state.
习题课
理想气体的性质和计算
16. Two tanks are connected by a valve. One tank contains 2kg of carbon monoxide gas at 77º C and 0.7 bar. The other tank holds 8kg of the same gas at 27º C and 1.2bar. The valve is opened and the gases are allowed to mix while receiving energy by heat transfer from the surrounding. The final equilibrium temperature is 42º C. Using the ideal gas model. Determine (a) the final equilibrium pressure, in bar; (b) the heat transfer for the process, in kJ.
6. 在一个承受一定重量的活塞下有27℃的空气 0.4kg，占据容积0.25m3。试问 （1）当加入25kJ热量后,其温度上升到多少? 并作了多少功? （2）若活塞到达最后位置后予以固定，此后 再继续加入25kJ热量, 则其压力上至多少?
习题课
理想气体的热力过程
7. 空气以qm=0.012kg/s的流量流过散热良好的压缩 机，入口参数P1=0.102MPa，T1=305K，可逆压 缩到出口压力P2=0.51MPa，然后进入储气罐。 求1kg空气的焓变量Δh和熵变量Δs，以及压缩机 消耗的功率P和每小时的散热量Qτ。 （1）设空气按定温压缩； （2）设空气按可逆绝热压缩； （3）设空气按n=1.28的多变过程压缩。 比热容取定值。
p1 100kPa T1 17C V1 150m 3 / min
We,in=15kW
习题课
理想气体的性质
15. A piston-cylinder device initially contains 0.5 m3 of nitrogen gas at 400 kPa and 27℃.An electric heater within the device is turned on and is allowed to pass a current of 2 A for 5 min from a 120-V source. Nitrogen expands at constant pressure, and a heat loss of 2800 J occurs during the process. Determine the final temperature of nitrogen.
习题课
理想气体的性质和计算
18. A rigid tank which acts as a perfect heat insulator is divided into two unequal parts A and B by a partition. Different amounts of the same ideal gas are contained in the two parts of the tank. The initial conditions of temperature T, pressure p, and total volume V are known for both parts of the tank. Find expressions for the equilibrium temperature T and pressure P reached after removal of the partition. Calculate the entropy change for A and B and the total entropy change of the tank. Assume that Cv,m is constant,
工程热力学与传热学
工程热力学
第三章 理想气体的性质和热力过程 习 题 课
习题课
理想气体状态方程的应用
1. 启动柴油机用的空气瓶, 体积V=0.3m3, 装有p1=8MPa，Tl=303K 的压缩空气。 启动后, 瓶中空气压力降低为p2=4.6MPa, 这时T2=303K。 求用去空气的量 (mol) 及相当的质量 (kg)。
习题课
理想气体的性质和计算
5. 某绝热的刚性容器，若用一隔板将其分为A和 B两个不相等的部分，其内各装有不同数量的 同一种理想气体，如图所示。气体状态参数初 始值是已知的。试推导隔板抽出后气体的平衡 温度和平衡压力表达式。Leabharlann 绝热A PATAVA
