Heat insulation is compressed is one kind is in what quantity of heat of the gas in reducing a process does not arise to be passed into apparently or come out to reduce a process. Inside a completely adiabatic air cylinder afore-mentioned processes can become reality. Isotherm is compressed is in reducing a process gas maintains the compression with constant temperature one kind process.

Compression ratio: ε

Compression ratio is to point to those who take angry absolutely pressure to compressor exhaust is mixed than.

Exemple: Into gas when sea level absolutely pressure is 0.1MPa, exhaust pressure is absolutely pressure 0.8MPa. Criterion compression ratio:

ε =P2/P1=0.8/0.1=8

The advantage that multistage reduces:

(1) economic compress result;

(2) drop exhaust temperature;

(3) can raise cubage coefficient;

(4) to piston compressor, lower gas the thrust to the piston. To screw compressor, as a result of its inlet pressure and compress press eventually between pressure difference is lesser, reason its bearing load and rotor are out of shape can reduce.

Compress medium:

Carbon of air, oxygen, nitrogen, carbon monoxide, 2 aerification is waited a moment.

Why should compress medium with air?

Because air is compressible, clear and transparent, and carry go to the lavatory (do not condense) , those who take is harmless sex, safe, endless.

Inert gase is a kind of gas that does not remove chemistry to the environment, standard compressor can compress inert gase euqally. Dry nitrogen and carbon dioxide all are inert gase.

Airy property:

Do air part:

Nitrogen (N2) 78.03%

Oxygen (O2) 20.93%

Carbon dioxide (CO2) 0.03%

Molecular quantity: 28.96

Specific gravity: When column of 0 ℃ , 760mmHg, γ =1.2931kg/m3

Specific heat: When atmosphere of a 25 ℃ , standard,

Cp=0.24kcal/(kg · ℃ ) =1.005kJ/(kg · K) is H in T ℃ , pressure (MmHg) when, airy proportion:

273/(273+t of γ T=1.2931 × ) the proportion of moist air of × H/760 Kg/m3, still should consider saturated vapor to divide pressure (0.378 ψ , pb) .

A few concepts:

1, pressure (call on physics ” intensity of pressure ” )

It is to show the susceptive on some unit area is perpendicular active force, if the pressure unit of 1 Newton force suffers to be 1 Pascal on 1 square metre:

Namely: 1Pa=1N/m2


1MPa=1 × 106Pa=10kg/cm2

2, absolutely pressure

Absolutely pressure is to consider with complete vacuum or absolutely 0 values are compared, the environmental air that we live has the absolutely pressure of 0.1Mpa. On sea level, the air pressure that appearance pressure increases 0.1MPa can reach absolutely pressure. Loftier air pressure jumps over height low.

3, atmosphere force

Barometer is to be used at measuring atmospheric pressure. Should add appearance pressure to go up to be able to reach absolutely pressure.

Pressure of air of + of manometric pressure of absolutely pressure =

Atmosphere force is with mercury millimeter is an unit normally, but any pressure unit can make likewise very good explanation:

0.1MPa of ≈ of =1.033kgf/cm2 of water column of =10.33 rice of mercuric column of millimeter of =760 of pressure of air of a standard.

Atmosphere is the same as the relation of height above sea level:

P=P0 × (1-H/44300)5.256Mbar

H — height above sea level, M

P0= atmosphere (0 ℃ , 1013.25 Mbar)

4, pressure unit conversion:

Unit: MPa, psi(bf/in2)



1kgf/cm2=98.0665kPa=0.0980665MPa ≈ 0.1MPa

5, temperature

A, temperature

Temperature is to point to measure some material to be in the method of sometime energy level. (or simpler say, some thing has how many heat or how many cold) .

Temperature limits is the freezing point according to water and boiling point. On the Centigrade thermometer, the freezing point of water is 0 ℃ , boiling point is 100 ℃ . On the Fahrenheit, the freezing point of water is 32F, boiling point is 212F.

From Fahrenheit changeover becomes centigrade: Fahrenheit =1.8 centigrade + 32, F

Centigrade =5/9 (Fahrenheit – 32) ℃

B, absolutely temperature

This is the temperature that explain with absolute zero as base point.

Base point zero is Fahrenheit 0 times 459.67K or centigrade 0 273.15 ℃

Absolute zero is the temperature that the temperature that shows from materially eliminate the place when all quantity of heat exists or the gas from theoretic some cubage shrink to exist to zero hour place.

Thermodynamic thermometric scale is used in international system of unit, also call off Er article mark or Kelvin, express with K, temperature value expresses with T. The centigrade that uses at the same time expresses with Celsius ℃ , temperature value expresses with T. The conversion between them concerns as follows:

T(K)=t(℃ ) + 273.15

Apparent, each degrees of centigrade (1 ℃ ) mix each in Er article thermometric scale (1K) is equal, be centigrade thermometric scale only compared Er article at 0 o’clock at 0 o’clock tower above 273.15 degrees.

C, cooling temperature is poor

Cooling temperature needs the term of the efficiency that is affirmatory condenser. Because condenser is impossible to achieve the efficiency of 100 % , we can measure the efficiency of condenser with cooling difference in temperature only. Cooling temperature difference is the difference of the cold water that enters condenser or cold air temperature and the temperature after compressing air to cool.