APPARATUS AND METHOD FOR TRANSFERRING HEAT

Abstract

An apparatus is for transferring heat. The apparatus has a heat transfer circuit with a heat transfer medium. The heat transfer circuit has: a heat receipt path having a first heat exchanger; a heat dispatch path having a compressor device and a second heat exchanger; and an intermediate path having an ejector device and a separator. A primary first heat exchanger is arranged: a) in a primary heat receipt path in the heat receipt path and connected to the separator; or b) in the separator. A secondary heat receipt path is arranged with a secondary first heat exchanger connected to the suction inlet of the ejector device. A method is for transferring heat using the apparatus.

Claims

1. An apparatus for transferring heat, the apparatus comprising a heat transfer circuit with a heat transfer medium, wherein the heat transfer circuit comprises: a heat receipt path comprising a first heat exchanger for transferring heat to the heat transfer medium; a heat dispatch path comprising a compressor device and a second heat exchanger for transferring heat away from the heat transfer medium; and an intermediate path between the receipt path and the dispatch path, which intermediate path comprises an ejector device and a separator, wherein the ejector device comprises a main inlet connected to the dispatch path, a suction inlet, and main outlet connected to the separator, and wherein the separator is configured to receive heat transfer medium from the ejector device and to provide heat transfer medium to the heat receipt path and the heat dispatch path, wherein the first heat exchanger comprises a primary first heat exchanger and a secondary first heat exchanger, wherein a) the heat receipt path further comprises a primary heat receipt path arranged with the primary first heat exchanger and connected to the separator without passing the ejector device, or b) the primary first heat exchanger is arranged in or in direct connection to the separator, wherein for both options a) and b) the heat receipt path further comprises a secondary heat receipt path arranged with the secondary first heat exchanger connected to the suction inlet of the ejector device, wherein the secondary heat receipt path further comprises an expansion device upstream of the secondary first heat ex-changer.

2. The apparatus according to claim 1, wherein the heat transfer medium mainly comprises CO2.

3. The apparatus according to claim 1, wherein the apparatus comprises at least one sensor for identifying a physical quantity dependent on a state of the heat transfer medium and a control unit, wherein the at least one sensor is positioned downstream of the secondary first heat exchanger and upstream of the suction inlet of the ejector device, and the control unit is adapted to receive information from the at least one sensor and control the expansion device on the basis of said information so that the heat transfer medium is mainly in the gaseous state after passing the secondary first heat exchanger.

4. The apparatus according to claim 3, wherein the sensor is one of a temperature sensor, a pressure sensor and an optic sensor.

5. The apparatus according to claim 1, wherein the primary first heat exchanger is positioned lower in elevation than the separator.

6. The apparatus according to claim 1, wherein the primary heat receipt path further comprises a pump device for conducting the heat transfer medium through the primary first heat exchanger.

7. The apparatus according to claim 1, wherein the heat dispatch path comprises an internal heat exchanger for exchanging heat between the heat transfer medium flowing upstream of the compressor device and downstream of the second heat exchanger.

8. The apparatus according to claim 1, wherein the apparatus comprises an additional path connecting the heat receipt path downstream of the separator and upstream of the first heat exchanger to the heat dispatch path downstream of the separator and upstream of the compressor device, wherein the additional path comprises a flow restriction.

9. A method for transferring heat via an apparatus, the apparatus comprising a heat transfer circuit with a heat transfer medium, wherein the heat transfer circuit comprises: a heat receipt path comprising a first heat exchanger for transferring heat to the heat transfer medium; a heat dispatch path comprising a compressor device and a second heat exchanger for transferring heat away from the heat transfer medium; and an intermediate path between the receipt path and the dispatch path, which intermediate path comprises an ejector device and a separator, wherein the ejector device comprises a main inlet connected to the dispatch path, a suction inlet, and main outlet connected to the separator, and wherein the separator is configured to receive heat transfer medium from the ejector device and to provide heat transfer medium to the heat receipt path and the heat dispatch path, wherein the first heat exchanger comprises a primary first heat exchanger and a secondary first heat exchanger, wherein a) the heat receipt path further comprises a primary heat receipt path arranged with the primary first heat exchanger and connected to the separator without passing the ejector device, or b) the primary first heat exchanger is arranged in or in direct connection to the separator, wherein for both options a) and b) the heat receipt path further comprises a secondary heat receipt path arranged with the secondary first heat exchanger connected to the suction inlet of the ejector device, wherein the secondary heat receipt path further comprises an expansion device upstream of the secondary first heat ex-changer, wherein the method comprises the steps of: receiving information from at least one sensor for identifying a state of the heat transfer medium downstream of the secondary first heat exchanger and upstream of the suction inlet of the ejector device, and adjusting the flow of the heat transfer medium through the expansion device on the basis of the information from the at least one sensor so that the heat transfer medium is mainly in the gaseous state after passing the secondary first heat exchanger.

10. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0038] In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein:

[0039] FIG. 1 shows a diagram of a heat transfer circuit of an apparatus for transferring heat according to prior art;

[0040] FIG. 2 shows a diagram of a heat transfer circuit of an apparatus for transferring heat according to an embodiment of the invention;

[0041] FIG. 3 shows a diagram of a heat transfer circuit of the apparatus according to a further embodiment of the invention; and

[0042] FIG. 4 shows a diagram of a heat transfer circuit of an apparatus for transferring heat according to an even further embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] In the drawings, the reference numeral 10 indicates a heat transfer circuit comprising a heat transfer medium. Identical reference numerals indicate identical or similar features in the drawings. The drawings are presented in a simplified and schematic manner, and the features therein are not necessarily drawn to scale. The short arrows adjacent and parallel to the lines in the diagrams indicate the flow direction of the heat transfer medium in the circuit.

[0044] FIG. 1 shows a heat transfer circuit 10 comprising a heat transfer medium according to prior art. The heat transfer circuit 10 comprises a heat receipt path 11, which comprises a first heat exchanger 6 for transferring heat to the medium, and a heat dispatch path 12, which comprises a second heat exchanger 2 for transferring heat away from the medium. Furthermore, the heat transfer circuit 10 comprises an intermediate path 13 between the heat receipt path 11 and heat dispatch path 12, which intermediate path 13 comprises an ejector device 3 and a separator 4. In the heat transfer circuit 10, the compressor 1 compresses the heat transfer medium (present in a gaseous state), whereby the temperature increases. Upon entering the second heat exchanger 2, for example a condenser, the gas cools down and condenses at least partially into a liquid. The heat transfer medium continues through the main inlet 31 of the ejector device 3, thereby creating a suction pressure at the suction inlet 32, before leaving the ejector 3 through the main outlet 33 and entering the separator 4. In the separator 4, the heat transfer medium is separated into a gaseous phase 41 and a liquid 42. From the separator, the heat transfer medium in the liquid state is then passed through an expansion device 5, for example an expansion valve, wherein it expands at least partially into a vapour, and thereby cools further down. The heat transfer medium, typically present as a vapour-liquid mixture, then enters the first heat exchanger 6, wherein heat is transferred to the heat transfer medium, e.g. from a further heat transfer medium in an external circuit 14. The further heat transfer medium is for example water.

[0045] The heat transferred to the heat transfer medium may cause the remaining heat transfer medium in the liquid phase to vaporise. Thereby only vapour will continue to the suction inlet 32 of the ejector 3. Also, from the separator, the heat transfer medium in the gaseous phase is passed to the compressor 1 for the cycle to continue. This prior art circuit has the problem that at low cooling need the compressor 1 will run at low power, whereby the pressure at the main inlet 31 of the ejector 3 may be too low to cause a suction pressure at the suction inlet 32 of said ejector 3. This circuit will therefore result in unsteady cooling since the compressor 1 will have to run at high power for shorter intervals at low cooling need, which will furthermore be inefficient.

[0046] FIG. 2 shows a diagram of a heat transfer circuit 10 of an apparatus 50 for transferring heat according to an embodiment of the invention. Compared to prior art, the heat receipt path 11 comprises a primary heat receipt path 11a comprising a primary first heat exchanger 7, and a secondary heat receipt path 11b comprising a secondary first heat exchanger 6 and a controllable expansion device 5, e.g. an expansion valve. The primary heat exchange path 11a receives liquid heat transfer medium from the separator 4 and returns a mixture of liquid and gaseous heat transfer medium to the same separator 4 without passing the ejector 3. The secondary heat receipt path 11b receives liquid heat transfer medium from the separator 4 and provides gaseous heat transfer medium to the suction inlet 32 of the ejector 3.

[0047] Thus, at low cooling need when the compressor 1 runs at low capacity, the heat transfer medium will still run through the primary heat receipt path 11a, whereby heat will be transferred to the heat transfer medium through the primary first heat exchanger 7, since the primary heat receipt path 11a is not connected to the suction inlet 32 of the ejector 3. The heat transfer circuit 10 of the invention thus avoids the problems with the prior art embodiment which may arise at low cooling requirement. When the cooling requirement increases and the compressor 1 runs with higher capacity, a suction pressure at the suction inlet 32 of the ejector 3 is established, thus ensuring flow of the heat transfer medium through the secondary receipt path 11b.

[0048] Upon expansion of the heat transfer medium through the expansion device 5, the temperature of the heat transfer medium will decrease. The secondary first heat exchanger 6 will therefore be able to cool the further heat transfer medium in the external circuit 14 to a lower temperature than the primary first heat exchanger 7.

[0049] The apparatus 50 further comprises a control unit 60 and at least one sensor 62 for measuring a physical quantity dependent on a state of the heat transfer medium. The at least one sensor 62 is positioned downstream of the secondary first heat exchanger 6 and upstream of the suction inlet 32 of the ejector device 3.

[0050] The control unit 60 is connected to the at least one sensor 62 and is adapted to receive information from the at least one sensor 62. The control unit 60 comprises a logic unit 70 and a memory unit 72. The received information from the at least one sensor 62 is adapted to be stored in the memory unit 72. The logic unit 70 is configured to process the stored information from the sensor 62 and determining the state of the heat transfer medium downstream of the secondary first heat exchanger 6 and upstream of the suction inlet 32 of the ejector device 3.

[0051] The control unit 60 is connected to the expansion device 5 and comprises means for transmitting control information to the expansion device 5 for adjusting the flow of the heat transfer medium through the expansion device 5 so that the heat transfer medium is mainly in the gaseous state after passing the secondary first heat exchanger 6.

[0052] In FIG. 2 the external circuit 14 runs through the primary 7 and secondary 6 first heat exchangers in series, thus cooling the further heat transfer medium in two steps. The two first heat exchangers 6,7 may alternatively cool two separate further heat transfer mediums in parallel.

[0053] FIG. 3 shows a diagram of a heat transfer circuit 10 of the apparatus 50 according to a further embodiment of the invention. The heat transfer circuit 10 in FIG. 3 differs from the heat transfer circuit 10 in FIG. 2 in that the heat transfer circuit 10 additionally comprises an internal heat exchanger 8 in the heat dispatch path 12, and an additional path which comprises a flow restriction 9 and connects the heat receipt path 11 downstream of the separator 4 and upstream of the first heat exchangers 6,7 to the heat dispatch path 12 downstream of the separator 4 and upstream of the compressor device 1. This heat transfer circuit 10 is especially beneficial if the compressor device 1 is lubricated by lubricating oil, which may exit said compressor device 1 and enter the separator 4, where it may be mixed into the liquid part 42 of the heat transfer medium. The flow restriction 9 is included to bleed a small amount of liquid heat transfer medium including lubricating oil into the heat dispatch path 12 to return the oil to the compressor device 1. The internal heat exchanger 8 ensures that all the liquid heat transfer medium vaporises before entering the compressor device 1 and that the heat transfer medium is not too cold for optimal functioning of the compressor device 1.

[0054] FIG. 4 shows a diagram of a heat transfer circuit 10 of the apparatus 50 according to an even further embodiment of the invention. This embodiment is similar to the embodiment shown in FIG. 2, but in the embodiment shown in FIG. 4 the primary first heat exchanger 7 is arranged in the separator 4 instead of the in a primary heat receipt path 11a (as shown in FIG. 2). The arrangement shown in FIG. 4 provides a similar technical effect as the arrangement shown in FIG. 2. At low cooling need when the compressor 1 runs at low capacity, no heat transfer medium will be conducted through the secondary heat receipt path 11b, as the flow through the ejector 3 is too low to create a suction pressure at the suction inlet 32. However, as the primary first heat exchanger 7 is positioned in the separator 4, heat will still be transferred to the heat transfer medium in the separator 4. This will cause some of the heat transfer medium in the liquid phase to vaporise to the gaseous phase, which will be available for the compressor 1 via the heat dispatch path 12. The heat transfer circuit 10 of the invention therefore avoids the problems of the prior art embodiment which may arise at low cooling requirement. When the cooling requirement increases and the compressor 1 runs with higher capacity, a suction pressure at the suction inlet 32 of the ejector 3 is established, and flow of the heat transfer medium through the secondary receipt path 11b will be established.

[0055] The invention also relates to a method of controlling the apparatus 50. The method comprises an initial step of receiving information from the sensor 62 for identifying a state of the heat transfer medium downstream of the secondary first heat exchanger 6 and upstream of the suction inlet 32 of the ejector device 3.

[0056] In a subsequent step the method comprises adjusting the flow of the heat transfer medium through the expansion device 5 on the basis of the information from the sensor 62 so that the heat transfer medium is mainly in the gaseous state after passing the secondary first heat exchanger 6. Thereby, it is assured that the suction inlet of the ejector device 3 receives the heat transfer medium mainly in the gaseous state.

[0057] Preferably, the flow of the heat transfer medium is adjusted so that more than 90% of the heat transfer medium is in the gaseous state, more preferably more than 95% of the heat transfer medium.

[0058] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps which are not stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.