Light emitting device with heat conducting fluid

1. A light emitting device, comprising at least one light source and a closed container, the closed container comprising a first area and a second area that is arranged opposite to the first area, the closed container including a cavity being filled with a heat conducting fluid that is thermally coupled to an inside surface of the closed container, wherein the at least one light source is arranged on an outside surface of the first area of the closed container that is outside of said cavity and thermally coupled to the inside surface of the closed container, wherein:

the container comprises a first tubular vessel as the first area and a second tubular vessel as the second area, the second tubular vessel surrounding the first tubular vessel at a distance larger than zero mm, and wherein the space between the first tubular vessel and the second tubular vessel is filled with the heat conducting fluid, or

an optical refractive index of the heat conducting fluid is greater than an optical refractive index of at least one of the first area or the second area; and

wherein the heat conducting fluid has a Grashof number in the range between 5·10 8 -3·10 10 .

2. The light emitting device according to claim 1 , wherein the heat conducting fluid is light transmissive, and wherein at least a part of the first area and the second area are light transmissive.

3. The light emitting device according to claim 1 , wherein the distance is in the range of 1-10 mm.

4. The light emitting device according to claim 1 , wherein the heat conducting fluid and/or at least a part of the container comprises at least one of scattering particles or inorganic luminescent particles.

5. The light emitting device according to claim 1 , wherein at least a part of the container is made of at least one of a light transmissive organic material, a glass material, a light transmissive ceramic material or a silicone material.

6. The light emitting device according to claim 1 , wherein the container comprises one or more optical elements for directing the light emitted during operation of the device in a predetermined direction.

7. The light emitting device according to claim 1 , wherein the light source comprises at least one array of light emitting diodes positioned substantially parallel to a longitudinal axis of the first tubular vessel and wherein the distance between two neighboring light emitting diodes is in the range of 5-15 mm.

8. The light emitting device according to claim 7 , comprising at least three arrays of light emitting diodes positioned substantially parallel to a longitudinal axis of the first tubular vessel, and wherein the three arrays are positioned in a non-symmetrical distribution along the radius of the first tubular vessel.

9. A lamp comprising at least one light emitting device according to claim 1 .

10. A luminaire comprising at least one light emitting device according to claim 1 .

11. The light emitting device according to claim 1 , wherein the container comprises the first tubular vessel as the first area and the second tubular vessel as the second area, the second tubular vessel surrounding the first tubular vessel at a distance larger than zero mm, and wherein the space between the first tubular vessel and the second tubular vessel is filled with the heat conducting fluid.

12. The light emitting device according to claim 1 , wherein the optical refractive index of the heat conducting fluid is greater than the optical refractive index of at least one of the first area or the second area.

13. A light emitting device, comprising at least one light source and a closed container, the closed container comprising a first area and a second area that is arranged opposite to the first area, the closed container being filled with a heat conducting fluid that is thermally coupled to an inside surface of the closed container, wherein the at least one light source is arranged on an outside surface of the first area of the closed container and thermally coupled to the inside surface of the closed container, wherein the heat conducting fluid has a Grashof number in the range between 5·10 8 -3·10 10 .

14. A heat sink for a light emitting device, comprising a closed container, the closed container comprising a first area and a second area that is arranged opposite to the first area, the closed container including a cavity being filled with a heat conducting and optically transparent fluid that is thermally coupled to an inside surface of the closed container, wherein at least one light source of the light emitting device is arranged on an outside surface of the first area of the closed container that is outside of said cavity, wherein:

the container comprises a first tubular vessel as the first area and a second tubular vessel as the second area, the second tubular vessel surrounding the first tubular vessel at a distance larger than zero mm, and wherein the space between the first tubular vessel and the second tubular vessel is filled with the heat conducting fluid, or:

an optical refractive index of the heat conducting fluid is greater than an optical refractive index of at least one of the first area or the second area; and

wherein the heat conducting fluid has a Grashof number in the range between 5·10 8 -3·10 10 .

15. The heat sink according to claim 14 , wherein the container comprises the first tubular vessel as the first area and the second tubular vessel as the second area, the second tubular vessel surrounding the first tubular vessel at a distance larger than zero mm, and wherein the space between the first tubular vessel and the second tubular vessel is filled with the heat conducting fluid.

16. The heat sink according to claim 14 , wherein the optical refractive index of the heat conducting fluid is greater than the optical refractive index of at least one of the first area or the second area.