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**1, Boyle's law**

Volume V, pressure strength P, P · V= constant

A certain mass of gas, when the temperature is constant, the pressure of the gas is inversely proportional to the volume of the gas.

approach P_{1}/P_{2}＝V_{2}/V_{1}

**2. Guy Lusac's Law**

When the pressure P is constant, the volume V of a gas of a certain mass is proportional to the * temperature of T:

V_{1}/V_{2}＝T_{1}/T_{2}= constant

When the pressure is unchanged, the temperature of a certain mass of gas increases 1℃ (or P decreases), then its volume increases (or decreases 1 /) 273.

**3. Charlie's Law**

When the volume V of the gas remains unchanged, the pressure P is proportional to the temperature T, namely:

P_{1}/P_{2}＝T_{1}/T_{2}

In a certain volume, a certain mass of gas, each temperature increases (or decreases) 1℃, its pressure increases (or decreases) 1 / 273.

**4. Average free path: λ = (510**^{-3})/P (cm)

**5. Draw speed: S=d**_{v}/d_{t}(L / sec) or S=Q / P

Q= Flow (lift · l / s) P= Pressure (lift) V= volume (l) t= time (seconds)

6. Guide: C=Q / (P_{2}-P_{1}) (L / s)

7. Vacuum extraction time: for the extraction time from atmospheric pressure to 1 pressure:

t=8V / S (empirical formula)

V is the volume and S is the pumping rate, and t is usually chosen within 5 to 10 min.

**8. Maintenance pump selection: S**_{tie up}＝S_{front}/10

**9. Estimation of the diffusion pump pumping rate: S=3D**^{2}(D= diameter cm)

**10. Front pumping speed of Roots pump: S= (0.1~0.2) S**_{a net for catching birds}(l/s)

**11. Leak rate: Q**_{leak}＝V(P_{2}-P_{1})/(t_{2}-t_{1})

Q_{leak}-System leakage rate (mmHg · l / s)

V-System Volume (l)

P_{1}-System medium pressure (mmHg) at vacuum pump stops

P_{2}-Pressure achieved in the vacuum chamber after time t (mmHg)

The t-pressure from P_{1}Up to P_{2}Exapsed Time (s)

**12. Selection of crude pump pumping speed: S=Q**_{1}/P_{in advance}(l/s) S=2.3V·lg(P_{a}/P_{in advance})/t

S-Effective pumping rate of the mechanical pump

Q_{1}-Air leakage rate of vacuum system (liter / s)

P_{in advance}-Pre-vacuum to be achieved (support)

V-Vacuum system volume (L)

t-achieve P_{in advance}The time required

P_{a}-Atmospheric pressure value (support)

**13. Front-stage pump pumping speed selection:**

The transmission pump with exhaust port pressure lower than one atmospheric pressure, such as diffusion pump, oil booster pump, Roots pump, turbine molecular pump, etc., requires the front pump to maintain its front pressure below the critical value. The selected front pump must be able to discharge the * * gas volume of the main pump. According to the pipeline, the constant flow principle of each section is as follows:

P_{n}S_{g}≥P_{g}S perhaps

S_{g}≥P_{gs}/P_{n}

S_{g}-Effective pumping rate of the front-stage pump (l / s)

P_{n}-Main pump critical front pressure (* * exhaust pressure) (l / s)

P_{g}-Vacuum chamber * high working pressure (support)

The S-Main pump is working at the P_{g}Effective pumping speed at.(l/s)

**14. Calculation formula of diffusion pump pumping speed:** S=Q / P= (K · n) / (P · t) (l / s)

Where: S-The extraction rate of the tested pump (l / s)

N-Upgrade on the oil column (grid)

Time (seconds)

P-Pressure measured near pump port (support)

K-Dropper coefficient (· l / s)

K＝V_{0}·(L/n)·(Υ_{0}/Υ_{m})+P_{a}△V_{t}

among V_{0}-Original volume of dropper and vacuum hose (l)

L-Length of the dropper scale section (mm)

Number of cells of the n-dropper scale part (cells)

Υ_{0}-Specific gravity of the oil (g / cm^{3})

Υ_{m}-The specific gravity of mercury (g / cm^{3})

P_{a}-Local atmospheric pressure (support)

△V_{t}-Corresponding volume on the scale of the dropper (l / case)

**15. The geometric extraction speed calculation formula of rotary wafer vacuum pump: S= π ZnLK**_{v}(D^{2}-d^{2})/(24×10^{4}) (l/s)

Where Z is the number of wafers, n is the speed (rpm), L is the pump chamber length, D is the pump chamber diameter, d is the rotor diameter (cm), K_{v}Is the volume utilization coefficient (generally take 95%).

**16, O-type rubber groove depth of B=0.7D**

D is the rubber diameter, groove width C=1.6B

**17, square rubber groove depth of B=0.8A**

A is the square rubber side length, and the groove width is C=1.67B

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