Through the application of thermodynamic principles, modern heat engines have been developed.
We are facing the reality that fossil fuel rerves are diminishing and will be insufficient in the foreable future.
雁荡山灵岩景区
Conquently, to tho who study thermodynamics, increasing efficiency in the u of fossil fuels and the development of alternate sources of thermal energy are the real challenges to technology for today and tomorrow.
Thermodynamics is a branch of science which deals with energy, its conversion from one form to another, and the movement of energy from one location to another.
政治表现情况Thermodynamics is involved with energy exchanges and the associated changes in the properties of the working fluid or substance.
Although thermodynamics deals with systems in motion, it does not concern itlf with the speed at which such process or energy exchanges occur.
Thermodynamics, like other physical sciences, is bad on obrvation of nature.
Engineering thermodynamics consists of veral parts, such as basic laws, thermal properties of the working fluids, process and cycle and so on.
Energy is a primitive (原始的）property. We postulate（假定） that it is something that all matter has.
Kinetic energy and potential energy are two forms of mechanical energy.
A change of the total energy is equal to the rate of work done on the system plus the heat transfer to the system. 蔬菜总动员
Enthalpy can be ud either as an extensive property H or as an intensive property h.
The two terms v2/2 and gz reprents kinetic energy and potential energy respectively.
Although the net heat supplied to a thermodynamic system is equal to the net work done by the system, the gross energy supplied to the system must be greater than the net wor
k done by the system.
Not all of the input heat is available for producing output work becau some heat must always be rejected by the system.
心劲儿
Related to the cond law statements are the concepts of availability of energy, entropy, process reversibility and thermal efficiency.
In all reversible process there is no change in the availability of the energy evolved in the process.
Due to this concept of availability of energy, the following statements can be made: Only a portion of heat energy may be converted into work.
Entropy S is an abstract thermodynamic property of a substance that can be evaluated only by calculation.
From the above expression one can find that the value of entropy of the system will increa when the heat is transferred into the system.
Process that return to their initial state are called cyclic process.
The Carnot cycle is most efficient cycle possible operating between two given temperature levels.
她笑了In the ideal Rankine cycle the efficiency may be incread by the u of a reheater ction.
The process of reheating in general rais the average temperature at which heat is supplied to the cycle, thus raising the theoretical efficiency. 创业指导
After partial expansion the steam is withdrawn from the turbine and reheated at constant pressure. Then it is returned to the turbine for further expansion to the exhaust pressure.
For the portion of the heat-addition process from the subcooled liquid to saturated liquid, the average temperature is much below the temperature of the vaporization and superheating process.
From the viewpoint of the cond law, the cycle efficiency is greatly reduced.
If this relatively low-temperature heat-addition process could be raid, the efficiency of the cycle would more nearly approach that of the Carnot cycle.
铁皮石斛怎么吃最好The refrigeration cycle is ud to transfer energy (heat) from a cold chamber, which is at a temperature lower than its surroundings.
The basic refrigeration cycle consists of a quence of process utilizing a working fluid, called the refrigerant, usually in continuous circulation within a clod system.
The refrigerant receives energy in the evaporator (cold chamber) at a temperature below that of the surroundings, and then rejects this energy in the condenr (hot chamber) prior to returning to its initial state.
赤诚之心In the abnce of friction the mechanical energies are completely interchangeable; that is, one unit of potential energy can be ideally converted into one unit of kinetic energy, and vice versa.
It reprents energy modes on the microscopic level, such as energy associated with nuc
lear spin, molecular binding, magnetic-dipole moment, molecular translation, molecular rotation, molecular vibration, and so on.
