Wärmehaushalt von Schraubenspindel-Vakuumpumpen

Rohe, Andreas

Wärmehaushalt von Schraubenspindel-Vakuumpumpen

dc.contributor.advisor	Kauder, K.	de
dc.contributor.author	Rohe, Andreas	de
dc.contributor.referee	Rautenberg, M.	de
dc.date.accepted	2005
dc.date.accessioned	2005-06-21T11:44:02Z
dc.date.available	2005-06-21T11:44:02Z
dc.date.created	2005-04-21	de
dc.date.issued	2005-06-13	de
dc.description.abstract	For dry running displacement vacuum pumps the abolition of cooling, sealing and lubricating fluids causes the problem of an increased thermal load. The thermodynamics of this process differ fundamentally from the thermodynamics of an air compressor. The former are characterised by a - usually - unadjusted pressure ratio, the oscillation of the working fluid and the periodic mixing process of the working gas (that has already been expelled) and the gas in the working chamber. This process results in adiabatic outlet temperatures that are distinctly higher than the outlet temperatures of an adjusted isentropic process. Lower suction pressure results in a discrepancy between the adiabatic model and reality, which is the reason why a calculation of the diabatic process is necessary. In support of a isothermal model the dependence of the working behaviour on both the speed and the gap height of the screw vacuum pump can be demonstrated, but it does not allow conclusions to be drawn about the thermal load of the gas and the pump. This work describes additional modules of the simulation program Kasim that has been developed as a solution to this problem. The lack of Nußelt equations for rotating systems in vacuum results in the application of heat transfer models of the overpressure range in order to calculate the heat transfer of those systems. Pressure-dependent substance properties have been based on gas cinematic models. Apart from these further models were investigated in order to determine the flow velocity and state variables of the working gas at the heat transferring areas.Initially, the simulation program was applied to a cold model machine which consisted of a srew vacuum pump with constant pitch. Compared with the steady state machine, the cold machine had the advantage of known boundary conditions. The large differences between simulation and experiment cannot be explained either by the sensitivity of the heat transfer models or the property models, or by the polytropic exponents of the expansion flow in the gap. Measurement technique appears to be the most likely explanation.That is the reason why a further investigation was carried out on the steady state machine. This included also body temperatures and an energy balance. In order to find out about body temperatures, a module was developed which allowed the surface elements of the finite element mesh of the pump to be allocated to the capacities and connections of the thermodynamic simulation system. After the boundary conditions had been defined, this assignment formed the basis for the calculation of the heat fluxes, based on a homogenous, isothermal machine whose temperature was to be re-determined by the thermal FE-calculations of its parts. This allowed a calculation of the steady state heat balance to be carried out iteratively.The verification was successful. The calculated heat flows of the machine parts were acceptably close to the experimental energy balance. Moreover, both the body temperatures and the maximum gas temperatures during the working process displayed a high degree of concordance.The present study proves that both the adaptation of heat transfer models of the overpressure range in the rotating system of a vacuum pump and the implementation of gas cinematic property models results in a good representation of the working behaviour. At the same time, it offers the possibility of further improvements. Moreover, it opens up the perspective of a completely closed simulation of rotating displacement vacuum pumps.	de
dc.format.extent	13614339 bytes
dc.format.mimetype	application/pdf
dc.identifier.uri	http://hdl.handle.net/2003/21484
dc.identifier.uri	http://dx.doi.org/10.17877/DE290R-15879
dc.language.iso	de	de
dc.publisher	Universität Dortmund	de
dc.subject	Minimum suction pressure	de
dc.subject	FEM	de
dc.subject	Housing gap	de
dc.subject	Housing temperature	de
dc.subject	Chamber model	de
dc.subject	KaSim	de
dc.subject	Knudsen flow	de
dc.subject	Continuous flow	de
dc.subject	Molecular flow	de
dc.subject	Rotor temperature	de
dc.subject	Suction speed	de
dc.subject	Screw spindle	de
dc.subject	Leakage mass flow	de
dc.subject	Gap flow	de
dc.subject	Thermal load	de
dc.subject	Thermo dynamical simulation	de
dc.subject	Dry running pump	de
dc.subject	Vacuum pump	de
dc.subject	Heat flow	de
dc.subject	Heat transfer	de
dc.subject	Enddruck	de
dc.subject	FEM	de
dc.subject	Gehäusespalt	de
dc.subject	Gehäusetemperaturen	de
dc.subject	Kammermodell	de
dc.subject	KaSim	de
dc.subject	Knudsenströmung	de
dc.subject	Kontinuumsstömung	de
dc.subject	Molekularströmung	de
dc.subject	Rotortemperaturen	de
dc.subject	Saugvermögen	de
dc.subject	Schraubenspindel	de
dc.subject	Spaltströmung	de
dc.subject	Thermische Belastung	de
dc.subject	Thermodynamische Simulation	de
dc.subject	Trocken laufend	de
dc.subject	Vakuumpumpe	de
dc.subject	Wärmströme	de
dc.subject	Wärmeübergang	de
dc.subject	Spaltmassenströme	de
dc.subject.ddc	620	de
dc.title	Wärmehaushalt von Schraubenspindel-Vakuumpumpen	de
dc.type	Text	de
dc.type.publicationtype	doctoralThesis	de
dcterms.accessRights	open access

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