Diffusion pump to supply heat from a condenser to a heating element

Abstract

A diffusion pump is provided that includes a housing and a boiling chamber connected to the housing. The boiling chamber has a heating element. The housing has a nozzle that is connected to the boiling chamber. The housing also has a condenser is arranged at an internal surface, where the condenser has a cooling system. The boiling chamber is thermally isolated from the condenser by an isolator. The cooling system is at least partially a water cooling system and is connected to the heating element via a heat pump such that heat from the condenser is supplied to the heating element.

Claims

1. A diffusion pump, comprising a housing, a boiling chamber connected to said housing, a heating element arranged in said boiling chamber, a nozzle arranged in said housing and connected to said boiling chamber, a condenser arranged in said housing in an area of said nozzle, and a cooling system configured for cooling said condenser and arranged in an area of said condenser, wherein said cooling system of said condenser is connected to said heating element via a heat pump such that heat from said condenser is supplied to said heating element.

2. The diffusion pump according to claim 1, further comprising an isolator that thermally isolates said boiling chamber from said condenser, wherein the isolator comprises PEEK, PTFE, another plastic material or a ceramic material.

3. The diffusion pump according to claim 1, wherein the boiling chamber is thermally insulated.

4. The diffusion pump according to claim 1, further comprising a vapor barrier axially spaced apart from the nozzle, wherein said vapor barrier comprises a vapor barrier cooling system independent of the cooling system of the condenser.

5. The diffusion pump according to claim 1, further comprising a forevacuum branch arranged between the nozzle and the boiling chamber, wherein said forevacuum branch comprises a cooling system.

6. The diffusion pump according to claim 5, wherein the cooling system of the forevacuum branch is independent of the cooling system of the condenser.

7. The diffusion pump according to claim 5, wherein the cooling system of the forevacuum branch is at least partially a water cooling system.

8. The diffusion pump according to claim 1, further comprising a regulator that regulates said cooling system of said condenser, wherein the regulator comprises a thermostat valve.

9. The diffusion pump according to claim 8, wherein the regulator further comprises a bypass of the thermostat valve that ensures minimum cooling of the condenser.

10. The diffusion pump according to claim 1, wherein the heat pump comprises an evaporator and a second condenser, the evaporator is connected to the cooling system of the condenser and the second condenser is connected to the heating element.

11. The diffusion pump according to claim 1, wherein the heat pump is configured as a compression heat pump or an absorption heat pump.

12. The diffusion pump according to claim 1, wherein the cooling system of the condenser is realized both by a water cooling system and the heat pump.

13. The diffusion pump according to claim 1, wherein the condenser comprises a high-vacuum-side area having a water cooling system and the area of said condenser adjacent, in a direction of the heating element, is connected to the heat pump.

14. The diffusion pump according to claim 1, wherein the heat pump is of a multistage configuration.

15. A method for controlling a diffusion pump, comprising: a housing, a boiling chamber connected to said housing, a heating element arranged in said boiling chamber, a nozzle arranged in said housing and connected to said boiling chamber, a condenser arranged in said housing in an area of said nozzle, and a cooling system configured for cooling said condenser and arranged in an area of said condenser, wherein the condenser temperature is measured and said cooling system of said condenser is controlled by a regulator depending on the condenser temperature, and wherein said cooling system of said condenser is connected to said heating element via a heat pump such that heat from said condenser is supplied to said heating element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereunder the disclosure is explained in greater detail on the basis of preferred embodiments with reference to the appended drawings in which:

(2) FIG. 1 shows a diagrammatic illustration of a first embodiment of the diffusion pump according to the disclosure,

(3) FIG. 2 shows a diagrammatic illustration of the pumping process on the basis of pump-specific variables,

(4) FIG. 3 shows a diagrammatic illustration of a second embodiment of the diffusion pump according to the disclosure, and

(5) FIG. 4 shows a diagrammatic illustration of a third embodiment of the diffusion pump according to the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(6) The diffusion pump according to the disclosure comprises a housing 10 including at its high-vacuum-side end a flange 12 with the aid of which the housing 10 can be connected to a vacuum chamber not shown. The housing 10 is connected to a boiling chamber 14 which comprises a heating element 16. Via the heating element 16 a propellant 18 is evaporated, said propellant rising in the diffusion pump and escaping into the housing via the two nozzles 20, 22. Existing gas particles are entrained by the propellant vapor. The propellant vapor travels to a condenser 24 which is arranged in the area of the nozzles 20, 22 at the housing 10. The condenser 24 comprises a cooling system 26. In the illustrated embodiment, the cooling system 26 is a water cooling system having a supply line 27 and a discharge line 25.

(7) The propellant vapor condenses at the condenser 24 and travels back to the boiling chamber 14.

(8) Between the condenser 24 and the boiling chamber 14 a forevacuum branch 28 is arranged which is adapted to be connected to a forevacuum pump not shown. Gas transported by the propellant vapor is sucked off by the forevacuum pump via the forevacuum branch 28. The forevacuum branch 28 comprises a cooling system 26-1. Preferably, the cooling system 26-1 of the forevacuum branch 28 is independent of the cooling system 26 of the condenser 24.

(9) To prevent loss of the heat of the heating element 16, the boiling chamber 14 is completely surrounded by an insulation 30. Hence heat is prevented from being dissipated from the boiling chamber 14 to the surroundings. Thus the required heat output of the heating element 16 is reduced.

(10) The heating element 16 has connected thereto a heating element regulator 32 with the aid of which the heat output of the heating element can be adjusted to the respective pumping situation.

(11) In the area of the condenser 24 a temperature measuring device 34 is arranged which measures the condenser temperature T.sub.c. Here, the condenser temperature T.sub.c is measured at the condenser surface. The temperature T.sub.c of the condenser 24 can also be measured via the temperature of the cooling water of the discharge line 25. The temperature measuring device is connected to a condenser cooling system regulator which is configured as a thermostat valve 36. Via the thermostat valve 36 the cooling water flow V through the cooling system 26 of the condenser 24 can be adjusted depending on the measured surface temperature T.sub.c of the condenser 24.

(12) To ensure that always minimum cooling of the condenser 24 is effected, the condenser cooling system regulator comprises an emergency means which is provided as a bypass 38 to the thermostat valve 36. When the condenser cooling system regulator fails, cooling water continues to be supplied through the bypass 38 to the cooling system 26 of the condenser 24 such that the propellant vapor continues to evaporate. The emergency means is in particular required in the case of power failure or sudden shutdown of the diffusion pump and ensures that due to minimum cooling of the condenser 24 the diffusion pump can be properly shut down without the propellant vapor entering the vacuum chamber.

(13) The pumping process is explained in detail with reference to FIG. 2, wherein this is a diagrammatic illustration which does not show any exact values. In particular, the disclosure is not exclusively limited to the illustrated process flow of the pumping process since an exemplary pumping process is shown. In FIG. 2 the pressure p 60, the coolant flow V 62, the heating element temperature T 64, the vapor pressure of the propellant 66 as well as the condenser temperature T.sub.c 67 are illustrated for the different pumping situations. The left vertical axis of the graph describes the pressure for the line 60 and the line 66, whereas the right vertical axis depicts the temperature for the lines 64 and 67 as well as the coolant flow for the line 62. On the horizontal axis of the graph of FIG. 2 the different pumping situations are plotted.

(14) In the area 68 there is only a small pumping effect or no pumping effect at all. In the vacuum chamber a pressure p.sub.0 prevails. This situation is encountered between two pumping processes and in particular during standby operation.

(15) In the second area 70 a pressure reduction from an initial pressure p.sub.0 to an operating pressure p.sub.1 is effected by a pumping-out process. When the vacuum chamber is pumped out 70 the heat output and correspondingly the temperature T of the heating element 16 are increased to the maximum value T.sub.max to increase the suction capacity of the diffusion pump. For compensating the increased heat input by the heating element 16 the amount of cooling water V for cooling the condenser 24 is increased. Here, it is not necessary that the condenser temperature T.sub.c in the area 70 reaches a minimum T.sub.c,min. The coolant flow V through the condenser 24 may be controlled such that the condenser temperature T.sub.c continuously decreases from its initial value T.sub.c,0 to the operating value T.sub.c,1.

(16) When the operating pressure p.sub.1 has been reached in the vacuum chamber, the heating element regulator adjusts the temperature T of the heating element 16 to the upper value of the boiling range of the propellant used. Here, the temperature T of the heating element 16 is reduced from its maximum value T.sub.max, which is required for rapidly reaching the operating pressure p.sub.1 in the area 70, to the value T.sub.1. Hence a pumping effect continues to be ensured since in particular T.sub.1 is larger than T.sub.0 such that an unnecessary heat input is prevented. The reduction of the heat output of the heating element 16 from T.sub.max to T.sub.1 at the same time results in the amount of cooling water V being reduced by the condenser cooling system regulator in the form of the thermostat valve 36 from V.sub.max to V.sub.1. Hence the surface temperature of the condenser 24 increases to T.sub.c,1 and/or the condenser end temperature T.sub.c,1 is reached. An increase of the surface temperature T.sub.c of the condenser is, however, intended only when, at the increased temperature, the vapor pressure 66 of the propellant continues to be below the operating pressure p.sub.1 of the vacuum chamber, as shown in FIG. 2

(17) Between two pumping processes 68 the temperature T of the heating element 16 is reduced to below the lower value of the boiling range of the propellant used. Hence no or only a very small amount of propellant 18 is evaporated. A pumping effect is neither required nor attained at a reduced heat output of the heating element 16. Simultaneously with the reduction of the temperature T of the heating element 16 to T.sub.0 between two pumping processes the coolant flow V of the cooling system 26 of the condenser 24 is reduced to V.sub.0 by the thermostat valve 36.

(18) FIG. 3 shows a second embodiment of the disclosure. Identical parts are designated by identical reference numerals. Although this is an alternative embodiment, for the purpose of saving energy required for a diffusion pump it is nevertheless possible to combine the individual features of the first embodiment with those of the second embodiment, unless such features are mutually exclusive.

(19) According to the second embodiment, the cooling system 26 is connected to a heat pump 40 which comprises a condenser 41 and an evaporator 39. Cooling water travels from the cooling system 26 at the housing 10 of the diffusion pump to a reservoir 42. From the reservoir 42 the still warm cooling water travels to the heat pump 40 which extracts heat from the cooling water. Hence the temperature of the cooling water is reduced. The cooling water cooled in this manner is fed to the cooling system 26 via a feed pump 44 through the thermostat valve 36 or the bypass 38. The heat energy extracted from the cooling water by the heat pump is fed to the heating element 16 via a heating circuit. Thus heat extracted by the cooling system 26 is used to heat the propellant 18 via the heating element 16. The heat extracted by the cooling system 26 has no dissipation loss, and at the same time the required energy which has to be fed to the heating element 16 from outside, for instance in the form of electric energy, can be reduced. Here, the heat pump 40 is in particular configured as a compression heat pump. In particular, it may be preferable to reverse the flow direction such that the cooling water first dissipates its heat energy in the heat pump 40 and then travels to the reservoir 42. From there, the cooling water is fed to the cooling system 26 with the aid of the feed pump 44.

(20) In FIG. 4 a third embodiment is illustrated, wherein identical parts are designated by identical reference numerals. Features of the preceding embodiments can be combined with those of the third embodiment for reducing the energy demand of the diffusion pump as long as the features are not mutually exclusive.

(21) According to the third embodiment, the high-vacuum-side area 46 is configured as a water cooling system 26. Further, a vapor barrier 48 is provided which comprises a water cooling system. The area 50 of the condenser 24 adjacent in the direction of the heating element 16 is connected to a heat pump 40 such that heat from the area 50 is fed to the heating element 16 via the heat pump 40 thus heating the propellant 18. In addition, a controllable thermostat valve may be arranged in the circuit of the heat exchanger, which thermostat valve is in particular adapted to be controlled by means of the temperature measuring device 34 or an additional temperature measuring device arranged in the area 50.

(22) In particular, the boiling chamber 14 is thermally isolated from the housing 10 by an isolator 52. The isolator 52 causes the heat generated by the heating element 16 not to travel to the housing 10 and thus the heat need not be dissipated via the cooling system 26 or the heat pump 40. Thus the energy consumption of the diffusion pump is further reduced. The isolator 52 has a low heat conductivity.