Fundamentals of Vacuum Technology (1248463), страница 67
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The conductance C found in this manner must bemultiplied by the clausing factor γ = 0.963 (intersection ofconnecting line with the γ scale) to obtain the trueconductance Cm in the molecular flow region:Cm á γ = 17 á 0.963 = 16.37 l/s.In a tube with a length of 1 m and an internal diameter of 5 cma molecular flow prevails if the mean pressure p in the tube is< 2.7 á 10-3 mbar.To determine the conductance C* at higher pressures than2.7 á 10-3 mbar, at 8 á 10-2 mbar (= 6 á 10-2 torr), for example,the corresponding point on the p scale is connected with thepoint d = 5 cm on the ÒdÓ scale.
This connecting line intersectsthe ÒαÒ scale at the point α = 5.5. The conductance C* atp = 8 á 10-2 mbar is: C* = Cm á α = 16.37 á 5.5 = 90 l/s.Nomogram for determination of conductance of tubes (air, 20 ¡C) in the entire pressure range.164HomePump-down time t [min]Volume V [min3][m3 á hÐ1] Pumping speedTables, Formulas, DiagramsExample 2ple 1Gas evolution [mbar á l á sÐ1 á mÐ2]ExamweaknormalstrongArea F [m2]The nomogram indicates the relationship between the nominalpumping speed of the pump, the chamber volume, size andnature of the inner surface as well as the time required toreduce the pressure from 10 mbar to 10-3 mbar.Example 1: A given chamber has a volume of 70 m3 and aninner surface area of 100 m2; a substantial gas evolution of2 á 10-3 mbar á l á s-1 á m-2 is assumed.
The first question is todecide whether a pump with a nominal pumping speed of1300 m3/h is generally suitable in this case. The coordinatesfor the surface area concerned of 100 m2 and a gas evolutionof 2 á 10-3 mbar á l á s-1 á m-2 result in an intersection point A,which is joined to point B by an upward sloping line and thenconnected via a vertical line to the curve that is based on thepumping speed of the pump of 1300 m3/h (D). If the projectionto the curve is within the marked curve area (F), the pumpingspeed of the pump is adequate for gas evolution. The relevantpump-down time (reduction of pressure from 10 mbar to10-3 mbar) is then given as 30 min on the basis of the lineconnecting the point 1300 m3/h on the pumping speed scaleto the point 70 m3 (C) on the volume scale: the extensionresults in the intersection point at 30 min (E) on the time scale.8 á 10-5 mbar á l á s-1 á m-2 is to be evacuated from 10 mbar to10-3 mbar within a time of 10 min.
The nomogram shows thatin this case a pump with a nominal pumping speed of150 m3/h is appropriate.In example 2 one has to determine what pumping speed thepump must have if the vessel (volume = approx. 3 m3) with asurface area of 16 m2 and a low gas evolution ofFig.
9.10: Determination of pump-down time in the medium vacuum range taking into account the outgasing from the walls165HomeTables, Formulas, Diagrams10001,00E+03Mercury100Vapor pressure [mbar]1,00E+02Halocarbon 11Halocarbon 121,00E+01Halocarbon 131,00E+0010Halocarbon 221Santovac 5(similar to Ultralen)10-1Vapor pressure (mbar)1,00E-01TrichorethyleneAcetoneAziepon 20110-21,00E-0210-31,00E-03DC 704Diffelen ultr a10-41,00E-0410-51,00E-05DC 7051,00E-06 -6101,00E-07-710Temperature [¡C]1,00E-08-810DiffelenlightDiffelennormal1,00E-09-910Fig.
9.11: Saturation vapor pressure of various substances-101,00E-101010-111,00E-1110-121,00E-120255075100150200250Temperature (°C)Temperature [¡C]Temperature [K]Fig. 9.12: Saturation vapor pressure of pump fluids for oil and mercury fluid entrainment pumpsVapor pressureFig. 9.13: Saturation vapor pressure of major metals used in vacuum technology166HomeVapor pressure [mbar]Tables, Formulas, Diagramsp critical pointP melting pointTemperature [¡C]1 NBR (Perbunan)2 Silicone rubber3 TeflonFig. 9.14: Vapor pressure of nonmetallic sealing materials (the vapor pressure curve for fluororubber lies between the curves for silicone rubber and Teflon).Ultrahigh vacuum<10Ð7 mbar<10Ð5 PaFig. 9.15: Saturation vapor pressure ps of various substances relevant for cryogenic technology ina temperaturerange of T = 2 Ð 80 K.High vacuum10Ð7 to 10Ð3 mbar10Ð5 to 10Ð1 PaMedium vacuum10Ð3 to 1 mbar10Ð1 to 102 PaRough vacuum1 to approx.
103 mbar210 to approx. 105 PaPiston vacuum pumpDiaphragm vacuum pumpLiquid-ring vacuum pumpSliding-vane rotary vacuum pumpMultiple-vane rotary vacuum pumpTrochoide vacuum pumpRotary plunger vacuum pumpRoots vacuum pumpTurbine vacuum pumpGaseous-ring vacuum pumpTurbomolecular pumpLiquid jet vacuum pumpVapor jet vacuum pumpDiffusion pumpDiffusion ejector pumpAdsorption pumpsubmilation pumpSputter-ion pumpCryopump10Ð1410Ð1310Ð1210Ð1110Ð1010Ð910Ð8Working range for special model or special operating data10Ð710Ð610Ð510Ð410Ð3p in mbar →10Ð210Ð1100101102103Normal working rangeFig. 9.16: Common working ranges of vacuum pumps167HomeTables, Formulas, DiagramsHigh vacuum10Ð7 to 10Ð3 mbar10Ð5 to 10Ð1 PaUltrahigh vacuum<10Ð7 mbar<10Ð5 PaMedium vacuum10Ð3 to 1 mbar10Ð1 to 102 PaRough vacuum1 to approx.
103 mbar210 to approx. 105 PaPressure balanceSpring element vacuum gaugeBourdon vacuum gaugeDiaphragm vacuum gaugeCapacitance diaphragm vacuum gaugePiezoelectric vacuum gaugeLiquid level vacuum gaugeU-tube vacuum gaugeCompression vacuum gauge(McLeod vacuum gauge)Decrement vacuum gaugeThermal conductivity vacuum gaugePirani vacuum gaugeThermocouple vacuum gaugeBimetallic vacuum gaugeThermistor vacuum gaugeCold-cathode ionization vacuum gaugePenning ionization vacuum gaugeMagnetron gaugeHot-cathode ionization vacuum gaugeTriode ionization vacuum gauge for medium vacuumTriode ionization vacuum gauge for high vacuumBayard-Alpert ionization vacuum gaugeBayard-Alpert ionization vacuum gauge with modulatorExtractor vacuum gaugePartial pressure vacuum gauge10Ð1410Ð1310Ð1210Ð1110Ð1010Ð910Ð810Ð710Ð610Ð510Ð410Ð3p in mbar →10Ð210Ð1100101102103The customary limits are indicated in the diagram.Working range for special models or special operating dataFig.
9.16a: Measurement ranges of common vacuum gauges168HomeTables, Formulas, DiagramsSaturated vaporFig. 9.17: Specific volume Vsp of saturated water vapor in m3/kg within a range of 0.013 to 133 mbar.Fig. 9.18: Breakdown voltage U between parallel electrodes in a homogeneous electrical field asa function of gas pressure p distance between electrodes d (in mm) (Paschen curve),for air.169HomeTables, Formulas, DiagramsSOLIDLIQUIDEvaporationMeltingWater vapor pressure [mbar]Triple point(0.01¡C, 6.09 mbar)SublimationGASEOUSTemperature [¡C]Fig. 9.19: Phase diagram of water170HomeStatutory units10.
The statutory unitsused in vacuumtechnology10.1 IntroductionTwo federal German laws and the related implementing provisions stipulatewhich units must be used for measurements today (generally since January1, 1978) in business and official documents and communications. Theprovisions resulted in a number of fundamental changes that also have tobe taken into account in vacuum technology. Many of the units commonlyused in the past, such as torr, gauss, standard cubic meter, atmosphere,poise, kilocalorie, kilogram-force, etc., are no longer permissible.
Instead,other units are to be used, some of which are new while others werepreviously used in other fields. The alphabetical list in Section 10.2 containsthe major variables relevant for vacuum technology along with their symbolsand the units now to be used, including the SI units (see below) and legallypermissible units derived from them. The list is followed by a number ofremarks in Section 10.3. The purpose of the remarks is, on the one hand,to establish a connection with previous practice wherever this is necessaryand, on the other hand, to provide explanations on practical use of thecontent of the alphabetical list.Statutory units are:a) the basic SI units (Table 10.4.1)b) units derived from the basic SI units, in some cases with special namesand unit symbols (Tables 10.4.2 and 10.4.4)c) units used in atomic physics (Table 10.4.3)d) decimal multiples and decimal parts of units, some with special namesExamples:105 N ( m-2 = 1 bar)1 dm3 = 1 l (liter)103 kg = 1 t (ton)Detailed descriptions are provided in publications by W.
Haeder and E.GŠrtner (DIN), by IUPAP 1987 and by S. German, P. Draht (PTB). Theseshould always be referred to if the present summary tailored to vacuumtechnology leaves any questions open.The statutory units for measurements are based on the seven basic SI unitsof the Syst•me International (SI).10.2 Alphabetical list1 of variables, symbols and units frequently used invacuum technology and its applications (see also DIN 28 402)1 Thelist is based on work done by Prof. Dr.
I. LŸckert, for which we would like to express our gratitude.No. VariableSymbolSIunitPreferred statutoryunitsNo. of remarkin Section 10.31234567891011121314151617AsÐ1 (Bq)sÐ13/1ÐWmuNAakϑ (theta)pvtρ (ro)ε (epsilon)DLMn, fpJkgmolÐ1m á sÐ2J á KÐ1ÐN á mÐ2, Paskg á mÐ3F á mÐ1m2 á sÐ1NásámNámsÐ1N á mÐ2, PaJ, kJ, kWh, Wskg, µgmolÐ1m á sÐ2, cm á sÐ2j á KÐ1, mbar á l á KÐ1¡Cmbar, bars, min, hkg á mÐ3, g á cmÐ3F á mÐ1, As á VÐ1 á mÐ1m2 á sÐ1, cm2 á sÐ1NásámN á m, kN á msÐ1, minÐ1bar, mbarActivity (of a radioactive substance)(General gas constant)WorkAtomic massAvogadro constantAccelerationBoltzmann constantCelsius temperatureVapor pressureTimeDensity (gas density)Dielectric constantDiffusion coefficientMoment of momentumTorqueRotational speed, rotational frequencyPressure in fluidsNotessee no.
73see Table V in Sect. 9see Table V in Sect. 93/23/3Pa = Pascalsee Table 10.4.43/6F = Farad3/3Pa = Pascal171HomeStatutory unitsNo. VariableSymbolSIunitPreferred statutoryunitsNo. of remarkin Section 10.31819202122232425262728293031323334353637383940Pressure as mechanical stressDiameterDynamic viscosityEffective pressureElectric field strengthElectrical capacitanceElectrical conductivityElectrical conductanceElectrical voltageElectric current densityElectric current intensityElectrical resistanceQuantity of electricity (electric charge)Electron rest massElementary chargeUltimate pressureEnergyEnergy doseAcceleration of free fallAreaArea-related impingement rateFrequencyGas permeabilitypdη (eta)peECσ (sigma)GUSIRQmeepultEDgAZAfQpermN á mÐ2, PamPa á sN á mÐ2, PaV á mÐ1FS á mÐ1SVA á mÐ2AΩ (ohm)CkgCN á mÐ2, PaJJ á kÐ1m á sÐ2m2mÐ2 á sÐ1Hzm3 (NTP)ÐÐÐÐÐÐÐÐÐÐm2 á s á PaN á mmÐ2cm, mmmPa á smbarV á mÐ1F, µF, pFS á mÐ1SV, mV, kVa á mÐ2, A á cmÐ2A, mA, µAΩ, kΩ, MΩC, Askg, gC, AsmbarJ, kJ, kWh, eV3/441424344454647484950515253545556575859Gas constantVelocityWeight (mass)Weight (force)HeightLiftIon dosePulseInductanceIsentropic exponentIsobaric molar heat capacityIsobaric specific heat capacityIsochore molar heat capacityIsochore specific heat capacityKinematic viscosityKinetic energyForceLengthLinear expansion coefficientRvmGhsJ^p (b)Lκ (kappa)CmpcpCmvcvν (nŸ)EKFlα (alpha)m á sÐ1, mm á sÐ1, km á hÐ1kg, g, mgN, kNm, cm, mmcmc á kgÐ1, C á gÐ1NásH, mHÐJ á molÐ1 á KÐ1J á kgÐ1 á KÐ160 Leak rateQLm á sÐ1kgNmmC á kgÐ1NásHÐJ á molÐ1 á KÐ1J á kgÐ1 á KÐ1J á molÐ1 á KÐ1J á kgÐ1 á KÐ1m2 á sÐ1JNmmÐÐÐÐÐmáKN á m á sÐ161626364656667PHBΦ (phi)BmqmWA á mÐ1TWb, V á sTkgkg á sÐ1PowerMagnetic field strengthMagnetic flux densityMagnetic fluxMagnetic inductionMassMass flow rate3/53/3Notessee also no.
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