Slide valve for a waste heat recovery system

1. A slide valve ( 1 ), having a valve housing ( 4 ), wherein an inlet passage ( 5 ) and an outlet passage ( 6 ) are formed in the valve housing ( 4 ), wherein a substantially cylindrical slide ( 3 ) is guided in a longitudinally movable manner in a guide bore ( 20 ) in the valve housing ( 4 ), wherein the guide bore ( 20 ) is configured to be connected hydraulically to the inlet passage ( 5 ) and to the outlet passage ( 6 ), wherein a closing body ( 35 , 35 a ) is arranged on the slide ( 3 ), wherein a slide seat ( 75 , 75 a ) is formed between the guide bore ( 20 ) and the closing body ( 35 , 35 a ), wherein the guide bore ( 20 ) and the sliding body ( 35 , 35 a ) form a sliding pair, and wherein the sliding pair has a material combination steel-graphite, in which the guide bore is graphite and the sliding body is steel, or wherein the sliding pair has a material combination ceramic-graphite, in which the guide bore is ceramic and the sliding body is graphite, or the guide bore is graphite and the sliding body is ceramic.

2. The slide valve ( 1 ) according to claim 1 , characterized in that the sliding pair has the material combination steel-graphite.

3. The slide valve ( 1 ) according to claim 1 , characterized in that the sliding pair has the material combination steel-graphite and the steel is coated with a Ti(C,N)+MoS 2 coating.

4. The slide valve ( 1 ) according to claim 1 , characterized in that the sliding pair has the material combination ceramic-graphite and in that the ceramic is a ZrO 2 or Al 2 O 3 ceramic.

5. The slide valve ( 1 ) according to claim 1 , characterized in that the graphite is provided with metal additives.

6. The slide valve ( 1 ) according to claim 1 , characterized in that a further outlet passage ( 7 ) is formed in the valve housing ( 4 ), wherein the guide bore ( 20 ) is configured to be connected hydraulically to the further outlet passage ( 7 ), and in that a further closing body ( 35 b ) is arranged on the slide ( 3 ), wherein a further slide seat ( 75 b ) is formed between the guide bore ( 20 ) and the further closing body ( 35 b ), wherein the guide bore ( 20 ) and the further closing body ( 35 b ) form a further sliding pair, and wherein the further sliding pair has the material combination steel-graphite or the material combination ceramic-graphite.

7. The slide valve ( 1 ) as claimed in claim 1 , characterized in that a valve tube ( 2 ) is arranged in the valve housing ( 4 ) and in that the guide bore ( 20 ) is formed in the valve tube ( 20 ).

8. The slide valve ( 1 ) according to claim 7 , characterized in that the valve tube ( 2 ) is embodied as a graphite bushing.

9. A waste heat recovery system ( 100 ) comprising a bypass valve ( 1 ) including a slide valve ( 1 ) according to claim 1 , the system also comprising a circuit ( 100 a ) carrying a working medium, wherein the circuit ( 100 a ) includes, in a direction of flow of the working medium, a pump ( 102 ), an evaporator ( 103 ), the bypass valve ( 1 ), an expansion machine ( 104 ) and a condenser ( 105 ), wherein a bypass line ( 106 ) is arranged in parallel with the expansion machine ( 104 ) and wherein the bypass valve ( 1 ) controls the mass flow of the working medium to the expansion machine ( 104 ) and to the bypass line ( 106 ).

10. The waste heat recovery system ( 100 ) according to claim 9 , characterized in that the working medium contains ethanol or cyclopentane.

11. The waste heat recovery system ( 100 ) according to claim 9 , characterized in that the bypass valve is configured to be operated at a temperature of the working medium of 300° C.

12. The slide valve ( 1 ) according to claim 1 , characterized in that the sliding pair has the material combination steel-graphite and the steel is coated with a low-friction material.

13. A slide valve ( 1 ), having a valve housing ( 4 ), wherein an inlet passage ( 5 ) and an outlet passage ( 6 ) are formed in the valve housing ( 4 ), wherein a substantially cylindrical slide ( 3 ) is guided in a longitudinally movable manner in a guide bore ( 20 ) in the valve housing ( 4 ), wherein the guide bore ( 20 ) is configured to be connected hydraulically to the inlet passage ( 5 ) and to the outlet passage ( 6 ), wherein a closing body ( 35 , 35 a ) is arranged on the slide ( 3 ), wherein a slide seat ( 75 , 75 a ) is formed between the guide bore ( 20 ) and the closing body ( 35 , 35 a ), wherein the guide bore ( 20 ) and the sliding body ( 35 , 35 a ) form a sliding pair, and wherein the sliding pair has a material combination steel-graphite, in which the guide bore is graphite and the sliding body is steel.

14. The slide valve ( 1 ) according to claim 13 , characterized in that the steel is coated with a Ti(C,N)+MoS 2 coating.

15. A slide valve ( 1 ), having a valve housing ( 4 ), wherein an inlet passage ( 5 ) and an outlet passage ( 6 ) are formed in the valve housing ( 4 ), wherein a substantially cylindrical slide ( 3 ) is guided in a longitudinally movable manner in a guide bore ( 20 ) in the valve housing ( 4 ), wherein the guide bore ( 20 ) is configured to be connected hydraulically to the inlet passage ( 5 ) and to the outlet passage ( 6 ), wherein a closing body ( 35 , 35 a ) is arranged on the slide ( 3 ), wherein a slide seat ( 75 , 75 a ) is formed between the guide bore ( 20 ) and the closing body ( 35 , 35 a ), wherein the guide bore ( 20 ) and the sliding body ( 35 , 35 a ) form a sliding pair, and wherein the sliding pair has a material combination ceramic-graphite, in which the guide bore is ceramic and the sliding body is graphite, or the guide bore is graphite and the sliding body is ceramic.

16. The slide valve ( 1 ) according to claim 15 , characterized in that the sliding pair has the material combination ceramic-graphite and in that the ceramic is a ZrO 2 or Al 2 O 3 ceramic.