A reflection on the laws of thermodynamics a little harder .

Question 1: Huh. Obviously, you have only studied engineering thermodynamics and are not very familiar with air conditioning, so let's use thermodynamics knowledge to help you answer.

In the simplest heat pump cycle, for example, the system should consist of four parts: an evaporator, a compressor, a condenser, and an expansion valve. The evaporator of the air conditioner (and dispersion unit) should be placed outdoors, so the heat medium in the system is vaporized and absorbed outdoors, and returned to the room to liquefy and release heat in the condenser, thereby increasing the indoor heat energy.

The consumption of 1kJ of electricity you see is only the electricity consumed by the compressor. The total energy still satisfies the first law of thermodynamics.

Question 2: Of course, it is not a single heat source (the sea) that absorbs heat energy and converts all of it into work (output electrical energy) without causing other changes (system stability), which does not violate the second law of thermodynamics. Because there is electrical energy consumed in this system, that is, the work done by the outside world to the system.

With external work, of course, it is possible to do work from a certain heat source to the outside world. The second law of thermodynamics is true in the absence of external influences.

It's a brilliant explanation, but it feels like it's against our common sense, but I think it's right.

If you can really use the internal energy in seawater in this way, it is really promising.

I think it's important to think about it from a process, and every process doesn't violate the law. If you think about it in general, it is not a single heat source.

does not violate the laws of thermodynamics, the so-called"The system is stable"It is not that the surface does not cause other changes, the heat dissipation of the heat engine itself is"Other changes".

The first law of thermodynamics reflects that all heat-related phenomena in nature have a certain directionality and are not impossible.

There are three laws of thermodynamics, and these three laws are inevitable for people studying science and engineering, so they must be understood, as follows:

1.The First Law (Law of Conservation of Energy).

Contents: Energy can neither be created or disappear out of thin air, it can only be transformed from one form to another, or from one object to another, and in the process of transfer and transformation, the total amount of energy remains the same. Since Joule proved that the conversion between mechanical, electrical, and internal energy satisfies the conservation relationship with precise experimental results, people have believed that the law of conservation of energy is a universal basic law of nature.

Internal energy transformation mode: The internal energy increment of a thermodynamic system is equal to the sum of the heat transferred to it by the outside world and the work done to it by the outside world.

There are two ways to change internal energy:1Do work (eg:

Frictional heat generation) 2.Heat transfer (e.g.: baking a fire in winter) negates the first type of perpetual motion machine.

e.g.: Let the horses run, and let the horses not eat grass). The first type of perpetual motion machine:

A substance returns to its initial state in one week, and does not absorb heat but releases heat or does work, which is called "the first type of perpetual motion machine". From the law of conservation of energy, energy is not created in a vacuum. It is impossible for this kind of machine to do work without consuming any energy, but to do a steady stream of external work.

2.The second law (the law of entropy increase).

Clausius formulates that heat can be spontaneously transferred from a hotter object to a colder object, but it is not possible to spontaneously transfer heat from a cooler object to a hotter object (except with human intervention). (e.g.: refrigerator).

Summary: Although energy is conserved, the energy transformation in nature is directional and irreversible.

What is entropy: Entropy in an isolated system never decreases over time. (eg1: A pot of boiling water will be cold when left unplaced; eg2: A leaf falls and does not return to the tree), negating the second type of perpetual motion machine (energy conversion is directional).

The second type of perpetual motion machine: After the first law of thermodynamics came out, people realized that energy could not be created out of thin air, so some people proposed to design a kind of device to absorb heat energy from the ocean, atmosphere and even the universe, and use these heat energy as the source of driving the rotation and work output of the perpetual motion machine, which is the second type of perpetual motion machine. A heat engine that absorbs heat from a single heat source and completely transforms it into useful work without other effects is called a type II perpetual motion machine.

3.The Third Law (Absolute Zero).

The third law of thermodynamics is usually expressed as having zero entropy at absolute zero, perfect crystals of all pure matter. It is also called absolute zero (t=0k. Absolute zero is practically unattainable and is only a theoretical value. (t=temperature).

The coldest place: Chilean astronomers have discovered the coldest place in the universe, which is called the "Pullback Bar Nebula", with a temperature of minus 272 degrees Celsius, which is the coldest place in nature known so far, called the "cosmic ice box".

Absolute zero is 0k (about or.

There are three major laws of thermodynamics, the first, second, and third.

The first law of thermodynamics is the law of conservation of energy. The second law of thermodynamics is formulated in several ways: Clausius states that heat can be spontaneously transferred from a hot object to a low temperature object, but it is not possible to spontaneously transfer from a low temperature object to a high temperature object.

Kelvin Planck stated that it was impossible to draw heat from a single heat source and completely convert that heat into work without other effects. and the entropy increase formulation: the entropy of an isolated system never decreases.

The third law of thermodynamics is usually stated that at absolute zero, the entropy of perfect crystals of all pure matter is zero, or absolute zero is unattainable.

Significance of Conservation of Energy:

1. The transformation and conservation of energy is an extremely important method to analyze and solve problems, and it is more common than the law of conservation of mechanical energy. For example, when an object falls through the air and is subjected to drag, the mechanical energy of the object is not conserved, but the total energy including the internal energy is conserved.

2. The law of conservation of energy is one of the three major discoveries in natural science in the 19th century, and it also solemnly announces the complete destruction of the illusion of the first type of perpetual motion machine.

3. The law of conservation of energy is a powerful way to understand and transform nature, and this law connects a wide range of natural science and technology fields.

The first type of perpetual motion machine is a machine that does not consume any energy but continuously does external work. It cannot exist because it violates the law of conservation of energy.

1. The formula of the first law of thermodynamics that I remember should be: q= u+w, which means that a closed system absorbs a certain amount of heat q, and part of this heat is converted into external work of the system, and the rest is converted into the thermodynamic energy of the system. The symbolic conventions in the formula are as follows:

q: The heat absorption of the system is positive (+) and the heat release is negative (—).

w: The external work of the system is positive (+) and the external work of the system is negative (—).

u=u2—u1, the thermodynamic energy increment, depends on the amount of change before and after.

2. W=Fs, F is the net force, F=(P-PO) A, where P is the absolute pressure of the system, Po is the external air pressure, A is the area of force F, and S is the distance traveled.

f is the difference between the internal pressure and the external pressure of the system. The pressure inside the system is mainly composed of the gravitational pull of the gas molecules and the kinetic energy (impact) of the molecules.

3. In thermodynamics, the above formula should not be used for the calculation of work, that is, w=fs is not suitable for the application of thermodynamics. However, by derivation, thermodynamics uses the formula of work w as follows: w=p v, where v is the change in the volume of the system, i.e., v=v2-v1,.

Therefore, according to the convention of the w sign, when w is positive, v 0 is due to p 0, i.e., the volume of the system expands, and conversely, when v 0, w is negative. Therefore, when the volume of the system expands, it is the work done by the system on the outside world (w is positive). Conversely, when the system is compressed, it is the outside world that does work on the system (w is negative).

The positive or negative of w can be determined by the change in volume, the decrease in volume (compressed gas) is positive, otherwise it is negative.

If we use w=fs, f refers to the pressure of the gas through the piston.

We know that the gas has pressure on the piston due to the pressure, and vice versa, the piston also has the pressure to react to the gas, which is this f.

The establishment of the first law of thermodynamics solves the practical problem of conservation of energy and explains the reason why the first type of perpetual motion machine cannot be realized.

The establishment of the first law of thermodynamics solves the problem of heat engine conversion efficiency, 100% heat conversion into mechanical energy can never be, and the second type of perpetual motion machine is impossible.

The establishment of the first law of thermodynamics solves that the limit of the lowest temperature is 0k

The first law of thermodynamics: also known as the principle of indestructibility of energy, which is the law of conservation of energy.

The simple explanation is as follows:

u = q+ w

or δu=q-w (these two expressions are commonly used at present, and the former one is used more).

Definition: Energy is neither created nor destroyed out of thin air, it can only be transformed from one form to another, or transferred from one object to another, and in the process of transformation or transfer, the total amount of energy remains the same.

Basic content: heat can be converted into work, and work can also be converted into heat; Consuming a certain amount of work will produce a certain amount of heat, and when a certain amount of heat disappears, a certain amount of work will also be produced.

The concrete manifestation of the universal law of energy conversion and conservation in all macroscopic processes involving thermal phenomena. One of the fundamental laws of thermodynamics.

The first law of thermodynamics is a formulation of the law of conservation and transformation of energy. The first law of thermodynamics states that heat energy can be transferred from one object to another and can also be converted to and from mechanical energy or other energy, and the total value of the energy does not change during the transfer and conversion.

It is the internal energy that characterizes the energy of a thermodynamic system. Through work and heat transfer, the system exchanges energy with the outside world, causing some changes in internal energy. According to the universal law of conservation of energy, after the system reaches the final state through any process from the initial state, the increment of the internal energy δu should be equal to the difference between the heat q transferred by the outside world to the system and the work a of the system to the outside world in this process, that is, u u δu q w or q δu w This is the expression of the first law of thermodynamics.

If, in addition to work and heat transfer, there is also energy z brought in by matter entering the system from the outside world, then it should be δu q w z. Of course, the above δu, w, q, and z can all be positive or negative (making the increase in system energy positive and the decrease in energy negative). For infinitesimal processes, the differential expression of the first law of thermodynamics is .

q du δw is a state function and du is a full differentiation [1]; q and w are process quantities, and δq and δw only indicate that the smallest quantities are not fully differential, and the symbols are δ to show the difference. In addition, because δu or du only involves the initial and final states, only the initial and final states of the system are required to be equilibrium, regardless of whether the intermediate state is equilibrium or not.

Another formulation of the first law of thermodynamics is that the first type of perpetual motion machine is impossible. This is a machine that many people fantasize about building that can work continuously without any fuel or power, and that can create something out of nothing and provide a steady stream of energy.

Obviously, the first type of perpetual motion machine violates the law of conservation of energy.