Introduction
isothermal process is a thermogravine term, refers to a thermodynamic process of the start of the thermodynamic system, and is equal to the temperature of the environment, the temperature of the environment in the whole process.
Related rules
Temperature is a thermodynamic function function, and the change value of the status function depends only on the system's origin and finalization, independent of the intermediate change process.
Yoshihe Purchase
Balbi Purono (Boyle's Law, sometimes known as Mariotte's Law or Papa Law, "by the voters and Maryt in the case Next, the interval has been discovered): At the quantitative temperature, the content of the ideal gas is inversely proportional to the pressure of the gas. That is,
is Boyle, in 1662, according to the experimental results: "In the closed container, quantitative gas, at constant temperature, gas The pressure and volume are relative. "" Said it is a glass of hears. This is the first "law" in human history.
Carno cycle
Corino cycle includes four steps:
isothermal suction heat, the system absorbs heat from the high temperature heat source during this process;
Insaturity expansion, the system is functional on the environment in this process; the temperature is lowered;
isothermally exist, in this process, the system releases heat, volume compression in the environment;
The heat is compressed, the system restores the original state, and the system is loaded with the environment during the waiting temperature compression and insulation compression.
The Carno cycle can be imagined to be a quasi-static process between two constant temperature heat sources, and the temperature of the high temperature heat source is T1, the temperature of the low temperature heat source is T2. This concept is 1824 N.l.s. S. Carano is proposed when the maximum efficiency problem of the heat machine is proposed. Carno assumes that the working substance is only exchanged with two constant temperature heat sources, no loss of heat dissipation, air leakage, friction. In order to make the process quasi-static process, the working substance should be an isothermal expansion process from high temperature heat source should be a temperature difference. Similarly, it should be an isothermal compression process to low temperature heat source. Due to the limit of exchange of heat in exchange with the two heat sources, it can only be a heat insulating process after separating the heat source. Thermo cycle is called Carno heat.
thermodynamics
in thermodynamics, u (internal), h (), G (Gibbs function), f (free Energy) has the dimension of energy, the unit is Joule, which is often referred to as thermal learning.
Internal u - S sometimes used; Helmhow Free Energy A = U - TS is also commonly represented; enthalpy h = u + pv; Gibibls free energy g = u + PV - TS (where t = temperature, S = entropy, P = pressure, V = volume)
two of T, S, P, V are independent variables, their differential expression is :
du = TDS - PDV; DF = -SDT - PDV; DH = TDS + VDP; DG = -SDT + VDP
By requesting the above differential expression ( Differential derivatives can obtain "McGlane relationship" between four variables of T, S, P, V.
Discrimination
isometrics and constant temperature processes are often confused, and they are generally analyzed.
isothermal process: The system is starting at the end of the temperature equal, and the temperature of the environment is constant in the entire process.
Constant temperature process: The temperature is constant during the entire process, and it is always equal to the temperature of the environment.
Figure 2 is an isothermal expansion diagram, which is that the pressure is only in the internal and external pressure, and the gas in the system is slow, and there is no friction, etc., that is, the system and the environment can completely restore the original, this Note The change process is in an instant, and the internal thermostatic heat source can be heat-exchanged, and the temperature of the system is equal to the temperature of the system, which is the so-called reversible process. However, this reversible process is only an ideal process, but it is actually not available. Because a process must cause changes in the state, the state change must break the balance, that is, the temperature moment of the system is equal to the temperature of the
environment, that is, the fluctuation of temperature. Even if the isothermal process is not a constant temperature process, it is very very slow, and the speed tends to, so that there is enough time to make the pressure of the gas become uniform and uniform, while allowing the system to instantly perform the thermostatic heat source. When the heat exchange is maintained, the temperature is the same as the constant temperature process, or the constant temperature process is the same temperature reversible process. Note the difference between the removal process and the heat insulation process, that is, the temperature during the process remains unchanged, there may be heat insulating or exothermic, the heat insulation process is no radiation in the process, but the temperature may change, so the system temperature change is not The logo system has no heat loss, and the process of latency can be a constant temperature process or a non-constant temperature process.
The exact definition of the waiting process should be: the isometric process refers to the process of constant constant ambient temperature, the start state of the system is the same and the process of the terminal temperature is equal to the ambient temperature , and During the change process, the system temperature can fluctuate, and the size of temperature fluctuations is for specific problems. When the study is not physical quantity of the status function, the process temperature should be considered; for the research status function, it can not consider the change in the process temperature, that is, the fluctuation of temperature can be ignored, but only the system's origin and The final temperature is the same and is equal to the ambient temperature.
Illustration
isothermal process, for example, a gas tube in contact with the inclusion, can be slowly compressed by a piston, and the active manifestation is manifested into the temperature of the gas into the container. Keep the constant energy. The battery is slowly charged and discharged at room temperature, both of which are approximately a temperature. Another example is 101.325KPa, 273.15k, melting into water, water is a removable phase change process of the same temperature and constant voltage. Features of a temperature-reversible process for a certain quality ideal gas is that the product of gas pressure P and volume V is constant, PV = constant amount. The internal energy of the ideal gas is only a function of temperature, so it can be unchanged during the process.
The ideal gas is the isothermal process from state I ( P 1 , v 1 ) To state II ( P 2 , v 2 ) system, the system is made
V is the number of gas, T is the thermodynamic temperature of the gas (see thermodynamic temperature label), R is a molar gas constant. The ideal gas is only a function of the temperature, so the energy changes in the same temperature process are zero. It is derived from thermodynamics, and the energy conversion of ideal gases in the same temperature is q = a , that is, the heat of the system absorbed is equal to the work made by the system .
isothermal process is an important process in thermodynamics. The Carno cycle is composed of two isothermal processes and two insulation processes. The reversible transformation of the substance trimist is also carried out under the isothermal conditions.