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04Chapter18 second law of Thermodynamics2(公开课)

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热力学第二定律(英文)

热力学第二定律(英文)

∙ Quasistatic processes are reversible processes ∙ Any curve in pV diagram is reversible process ∙ Reversible processes can be approached arbitrarily closely by carrying out truly processes infinitely slowly.
3.4 Entropy and the second law of thermodynamics
The principle of maximum entropy ∙ The entropy of an isolated system never decreases. ∙ It either stays constant (for reversible processes) or increases (for irreversible process).
Second Law of Thermodynamics
( Chapter 18 ) 热力学第二定律
contents
1
Second Law of Thermodynamics
2
Reversible and Irreversible Processes
3
Entropy and The Principle of Maximum Entropy
Definition We define entropy S as ∫︁ b dQ Sb − Sa = for any finite reversible process T a dQ dS = for any infinitesimal reversible process T

环境工程专业英语翻译

环境工程专业英语翻译

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FIRST AND SECOND LAW 歌词 翻译

FIRST AND SECOND LAW 歌词 翻译

FIRST AND SECOND LAW热力学第一和第二定律Flanders & Swann法兰德斯&斯旺The first law of thermodynamics热力学第一定律，Heat is work and work is heat (x 2)（就是）热可以转化为功，功可以转化为热。

Very good很好！The second law of thermodynamics热力学第二定律，Heat cannot of itself pass from one body to a hotter body (x 2) （就是）热本身不能自发转移到更高温物体，Heat won't pass from a cooler to a hotter (x 2)（即）热不能主动由低温物体转移到高温物体。

You can try it if you like but you far better notter (x 2)如果喜欢你可以试试，但我奉劝你一百万句还是算了，'Cause the cold in the cooler will be hotter as a ruler (x 2)定律决定（这样做）只会造成低温的物体更热，Because the hotter body's heat will pass through the cooler因为高温物体的热量会自动转移到低温物体。

Heat is work and work is heat热可以转化为功，功可以转化为热，And work is heat and heat is work功可以转化为热，热也可以转化为功。

Heat will pass by conduction (x 2)热可以通过传导转移，And heat will pass by convection (x 2)热也可以通过对流转移，And heat will pass by radiation (x 2)热还可以通过辐射转移，And that's a physical law这是物理定律。

24. The Second Law of Thermodynamics (cont.) and Entropy.SMI

24. The Second Law of Thermodynamics (cont.) and Entropy.SMI
00:03:39 the gases come back to where it is.
00:03:41 That's very important, if you want to make an engine,
00:03:44 it's not enough to convert; the whole purpose of heat engines
00:05:01 the furnace temperature and the ambient atmospheric temperature,
00:05:05 you can calculate the efficiency for this engine by actually calculating
00:03:24 some heat was rejected downstairs and the difference between
00:03:27 the two is the work.
00:03:33 Now, we call this a cyclic process because at the end of the day,
00:03:11 - Q2.
00:03:16 Do you understand that?
00:03:18 The work done by the gas equal to that.
00:03:20 And who paid for it?
00:03:22 It is the reservoir, upper reservoir furnished the heat,
00:02:27 So, it will reject heat into this heat bath.

第4章 热力学第二定律

第4章 热力学第二定律
p
1
T
q1
2
T1
q= 0 T2
3
1
2
q= 0
4
4
3
q2
0
v
0
Δs
s
3. The Efficiency of a Carnot Engine（卡诺热效率）
For any heat engine wnet q 1q 2 q2 t 1 q1 q1 q1 For a Carnot engine Method 1: From T-s diagram
T
a 2 1
q1-q2=wnet
b
0
p
1
4
3s
q w
qnet q1 q2 wnet
a
wnet
b 2
Q W
Qnet Q1 Q2 Wnet
0
4
3 v
（3）The coefficient of performance（工作系数） The COP of a refrigerator
（2）p-v and T-s diagrams
p-v diagram
p
1 a
counterclockwise direction • 1-b-2: expansion • 2-a-1: compression
0
4
wnet
b 2
3 v
T-s diagram counterclockwise direction • 1-b-2: absorb heat • 2-a-1: reject heat Cycle
（4）Mixing（混合过程）
Gas
evacuated
Gas A

Second Law of Thermodynamics

Second Law of Thermodynamics

The Second Law: Kelvin‐Planck Statement
It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce a net amount of work. In other words, no heat engine can have a thermal efficiency of 100%. Source (TH)
Refrigerators and Heat Pumps
In nature, heat flows from high‐temperature regions to low‐temperature ones. The reverse process, however, cannot occur by itself. The transfer of heat from a low‐ temperature region to a high‐temperature one requires special devices called refrigerators. Refrigerators are cyclic devices, and the working fluids used in the cycles are called refrigerant. Heat pumps transfer heat from a low‐temperature medium to a high‐temperature one. Refrigerators and heat pumps are essentially the same devices; they differ in their objectives only. Refrigerator is to maintain the refrigerated space at a low temperature. On the other hand, a heat pump absorbs heat from a low‐temperature source and supplies the heat to a warmer medium.

工程热力学与传热学chapter4The Second Law of Thermodynamics


The use of the second law of thermodynamics is not limited to identifying the direction of processes, however. The second law also asserts that energy has quality as well as quantity. The first law is concerned with the quantity of energy and the transformations of energy from one form to another with no regard to its quality. Preserving the quality of energy is a major concern to engineers, and the second law provides the necessary means to determine the quality as well as the degree of degradation of energy during a process. As discussed later in this chapter, more of high-temperature energy can be converted to work, and thus it has a higher quality than the same amount of energy at a lower temperature.
4-1 Irreversible process
热功转换模 拟图
１)热—功转换的方向性
4-1 Irreversible process

热工基础第四章

• A spontaneous process is the time-evolution of a system in which it releases free energy(most often as heat) and moves to a lower, more thermodynamically stable, energy state.自发过程：不需要任何外界作用而自动进行的过程。

3QQ'?When Q’≤Q，heat transfer from B to A meets5重物下落，水温升高水温下降，重物升高？只要重物位能增加小于等于水降内能减少，不违反第一定律。

摩擦过程是不可逆的电流通过电阻，产生热量对电阻加热，电阻内产生反向电流？只要电能不大于加入热能，不违反第一定律。

work →heatz Heat transfer under temperature differencez Heat of frictionz Liquid flow from high level to low levelz Electric current from high potential to low potential Notes：for spontaneous process1）Direction2）Irreversibility6总结：1）自发过程有方向性；2）自发过程不可逆;3）自发过程的反方向过程并非不可进行，而是要有附加条件：自发的补偿过程；4）并非所有不违反第一定律的过程均可进行。

7•能量是有‘质’的差别的，机械能属高质能，热能属低质能，热能所处温度越接近环境温度，其能质也越低。

•能质高的能量可以全部转换成能质低的能量，而能质低的不能全部转换成能质高的，而且必须有补偿条件。

•能量的传递过程总是朝着清除势差的方向进行的，在传递过程中，能量在数量上虽然保持守恒，但在能质上却降低了。

chapter03 The Second Law of Thermodynamics


A reversible heat engine is an idealization of real heat engines.
12
Physical Chemistry ENTROPY
Chapter 3
dq qC qH 0 (3.16) T TC TH For any closed system that undergoes a Carnot cycle, Eq. dqrev (3.16) shows that integral of around the cycle is zero. T
(3.9) (3.10)
(Sec. 1.8)
Physical Chemistry
T1 C (T ) T1 C (T ) dT T3 CV (T ) V dT dT V dT 0 CV (T ) T T T T T T T
1 3 1
9
P
Physical Chemistry
(a)
V Fig. 3.5
c s r d
(b)
V
14
Physical Chemistry
Chapter 3
Since these areas give the negative of the reversible work w done on the system in each process, wamnb = wab,
P
V
13
Chapter 3 Physical Chemistry (a) An arbitrary cyclic process. (b) Draw dashed adiabats (dashed lines) that divided the cycle into adjacent strips. Consider one such a strip, bounded by curve ab and cd at the top and bottom. Draw the reversible isotherm mn so that the area under the zigzag curve amnb equals the area under the smooth curve ab. P P m b a n

The laws of thermodynamics热力学定律


Second law 第二定律（熵律entropy law）
Second law: In any energy transfer, some energy is lost in the form of heat. 第二定律（熵律entropy law）能量的傳導過程，無法達 到百分之百的效率，必定有部份的能量以熱的形式 散失掉了。 △ H=△G+T△S △ G: The net change in the Gibbs free energy of the system. T: Temperature △S: The change in the entropy, or disorder, of the system.
primary production初級生產量
Photosynthesis: 6CO2 + 6H2O ! C6H12O6 + 6O2 Respiration: C6H12O6 + 6O2 ! 6CO2 + 6H2O Net primary production 淨初級生產量(NP) 可被用於植物生長和生殖的能量 Gross primary production 總初級生產量(GP) NP加上植物呼吸消耗的能量（R） GP = NP + R
Trophic structure營養結構
Food Chains 食物鏈： The pathway of energy transfer. A succession of organisms in an ecosystem that are linked by an energy flow and the order of who eats whom. Trophic levels 營養階層
能量金字塔
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卡诺循环是由两个准静 态等温过程和两个准静态绝 热过程组成 .
p3
D
o V1 V4
Qcd T2
V2
C
V
V3
理想气体的卡诺循环
Chapter 18 Second Law of Thermodynamics
2 Efficiency of Carnot Engine (p433-435)
p p1
p2 p4
e 25 %
柴油机 e 37 % 蒸汽机 e 8%
Chapter 18 Second Law of Thermodynamics
The efficiency e of any engine is defined by the ratio of the work it does to the heat input at the high temperature. (p432)
p3
T2
V2
o V1 V4
V
V3
at temperature T2.
D--A compress adiabatically
Chapter 18 Second Law of Thermodynamics 1) ab, isothermal process T1 , feature is DU = 0.
Questions:
Is it possible to reduce Q2 to zero? If not, why?
It
violate
the
second
law
of
thermaldynamics: It is impossible for a device whose sole effect is transferred completely into
W S AdBc
Chapter 18 Second Law of Thermodynamics 热力学第一定律
DQ W
净功
W Q1 Q2 Q
即：工质以传热的方式从高温热库得到能量，有一部 分仍以传热的方式放给低温热库，二者的差额等于工 质对外做的净功。
The working substances absorb heat from high temperature resource; one part of energy becomes work, and the other part release to the low temperature resource. The difference of them is the net work done by the working substances.
Chapter 18 Second Law of Thermodynamics
Chapter 18 Second Law of Thermodynamics
1 热机发展简介
历史上热力学理论最初是在研究热机工作过程的基 础上发展起来的。热机是利用热来做功的机器。1698
年萨维利和1705年纽可门先后发明了蒸汽机，当时蒸
汽机的效率极低. 1765年瓦特进行了重大改进 ，大大
提高了效率. 人们一直在为提高热机的效率而努力，从
work.
Chapter 18 Second Law of Thermodynamics
§18-3 Carnot Engine and Its Efficiency P433-436
French scientist and engineer N. L. Sadi Carnot(萨迪.卡诺) first proposed the ideal
A
c
d
VA
B
VB V
Chapter 18 Second Law of Thermodynamics
2) Important features of cyclic process (循环过程
的特点) •经过一个循环，内能不变。 DU = 0 •循环曲线为闭合曲线。
p
A
•循环曲线所包围的面积为
系统做的净功。
VB V
Chapter 18 Second Law of Thermodynamics
5 Efficiency of a Engine P432
对于正循环，其效率是在一次循环过程中工质对
外做的净功占它从高温热库吸收的热量的比率。其是
热机效能的一个重要标志。
各种热机的效率 液体燃料火箭 e 48 % 汽油机
engine’s concept in 1824.
1824 年法国的年青工程师卡诺提出一个工作 在两热源之间的理想循环—卡诺循环. 给出了热机 效率的理论极限值; 他还提出了著名的卡诺定理.
Chapter 18 Second Law of Thermodynamics
萨迪.卡诺是法国青年工程师、热力学的 创始人之一，是第一个把热和动力联系起来的 人。 他出色地、创造性地用“理想实验”的 思维方法，提出了最简单，但有重要理论意义 的热机循环——卡诺循环，并假定该循环在准 静态条件下是可逆的，与工质无关，创造了一 部理想的热机（卡诺热机）。 卡诺的目标是揭示热产生动力的真正的、 独立的过程和普遍的规律。1824年卡诺提出了 对热机设计具有普遍指导意义的卡诺定理，指 出了提高热机效率的有效途径，揭示了热力学 的不可逆性，被后人认为是热力学第二定律的 先驱。
Chapter 18 Second Law of Thermodynamics
Example:(page425:20) An ideal gas expands at
a constant pressure of 5.0 atm from 0.4L to 0.7L
at constant volume, and the pressure and temperature are allowed to drop until the temperature reaches its original value. Calculate (a) the total work done by the gas in the process, and (b) the total heat flow into the gas.
Chapter 18 Second Law of Thermodynamics
isobaric process isochoric process
Chapter 18 Second Law of Thermodynamics
Chapter 18 Second Law of Thermodynamics
A
Isothermal
T1 T2
Adiabatic C
A--B expand isothermally
at temperature T1. B--C expand adiabatically,
T1
D
B
no heat is exchanged.
C--D compress isothermally,
绝 热 方 程
V T 常量 pV 常量
p T
1

1
常量
Chapter 18 Second Law of Thermodynamics
1 Carnot Engine (p433) Carnot engine is ideal engine, all processes are reversible and no wasteful energy transfers occur due to friction. p T1 T2 Carnot cycle consists p1 A Qab of two isothermal T1 processes and two p B 2 adiabatic processes. W p4
The working substances ( 工作物质或工质：热机中 被利用来吸收热量并对外做功的物质 ) absorb heat from high temperature 高温热源T1 resource; one part of energy becomes work, Q吸 and the other part 热机 release to the low W temperature resource. After a cycle, the Q放 working substances resume their original 低温热源T2 state.
| transforme work | | W | d e . | absorbed heat | | Q1 |
高温热源
Q1
热机
e
W Q吸
W
Q2
低温热源
Chapter 18 Second Law of Thermodynamics
Using Ther.-I-law to the whole cyclic process,
c
W
d
B
o
VA
VB V
Chapter 18 Second Law of Thermodynamics
从状态A经状态c达到状态B，系统对外界做功W1，
W1 SVA AcBVB
从状态A经状态d达到状态B， 外界对系统做功W2，
p
A
c
W
d
B
W2 SVA AdBVB
o
VA
VB V
系统对外做净功的数值为W=W1-W2
W pdV
V1
V2
dV nRT 1 V1 V V2 nRT ln 1 V1
V2
p p1
p2 p4
A
T1 T2
Qab
W
D
Isothermal B C
T1
V2 Q1 W nRT ln 1 V1