WO2021069802A2

WO2021069802A2 - An arrangement

Info

Publication number: WO2021069802A2
Application number: PCT/FI2020/050667
Authority: WO
Inventors: Teemu SIHVONEN; Eemeli Tsupari; Kristian Melin
Original assignee: Teknologian Tutkimuskeskus Vtt Oy
Priority date: 2019-10-11
Filing date: 2020-10-09
Publication date: 2021-04-15
Also published as: US20240084722A1; EP4045773A2; WO2021069802A3

Abstract

A rankine cycle arrangement, the arrangement (100) comprising: an expander (1), a heat exchanger (2) connected to an inlet channel (3) of the expander (1) for heating working fluid to be fed in the expander (1), a condenser (5) connected to an outlet channel (6) of the expander (1) for cooling working fluid expanded in the expander (1), and a pump (8) connected to an outlet (9) of the condenser and to an inlet (10) of the heat exchanger for rising pressure of working fluid. The arrangement further comprises an ejector (11) comprising a high-pressure inlet (12), a low-pressure inlet (13), and an outlet channel (14). The ejector (11) is connected in parallel with the expander (1) such that a first portion of working fluid is capable to bypass the expander through said ejector (11).

Description

AN ARRANGEMENT

BACKGROUND

The invention relates to a rankine cycle arrangement. It is known methods and arrangements that utilize waste heat in producing electricity. A problem with these is that they are working in high pressures and need quite high temperature of waste heat.

BRIEF DESCRIPTION Viewed from a first aspect, there can be provided a ran kine cycle arrangement, the arrangement comprising: an ex pander for converting heat energy of working fluid into mechanical energy, a heat exchanger connected to an inlet channel of the expander for heating working fluid to be fed in the expander, the heat exchanger comprising a re ceiving channel being arranged to receive heat energy, a condenser connected to an outlet channel of the expander for cooling working fluid expanded in the expander, the condenser comprising a receiving channel being arranged to receive cooling fluid, a pump connected to an outlet of the condenser and to an inlet of the heat exchanger for rising pressure of working fluid, an ejector comprising a high-pressure inlet, a low-pressure inlet, and an outlet channel, the ejector being connected in parallel with the expander such that a first portion of working fluid is ca pable to bypass the expander through said ejector, and wherein the outlet channel of the expander is connected to the low-pressure inlet, the outlet channel of the ejector is connected to an inlet of the condenser for conducting working fluid from the ejector to the condenser, and an outlet of the heat exchanger is connected to the high- pressure inlet.

Thereby an arrangement utilizing a low temperature waste heat in converting heat energy to e.g. electrical energy by using Rankine cycle may be achieved. Furthermore, capi tal expenses of the arrangement may be radically reduced.

The arrangement is characterised by what is stated in the independent claims. Some other embodiments are character ised by what is stated in the other claims. Inventive em bodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit sub-tasks or in view of obtained benefits or benefit groups. Some of the definitions con tained in the following claims may then be unnecessary in view of the separate inventive ideas. Features of the dif ferent embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodi ments.

In one embodiment, the expander comprises a turbine. An advantage is that the thermodynamic efficiency of turbines is high.

In one embodiment, said working fluid is carbon dioxide. An advantage is that there is a substantial difference in vapor pressure between evaporation temperature and con densing temperature, and thus a high efficiency of the process may be achieved.

In one embodiment, said working fluid comprises refriger ant, ammonia, hydrocarbon, alcohol or combination thereof. An advantage is that these working fluids enable more ef ficient conversion of low temperature heat to power com pared to a water based standard steam rankine cycle. In one embodiment, the heat exchanger is a counterflow plate heat exchanger. An advantage is that the efficiency of the heat exchanger is high, and thus a more compact structure may be used.

In one embodiment, the condenser is a counterflow plate heat exchanger. An advantage is that the efficiency of the heat exchanger is high, and thus a more compact structure may be used.

In one embodiment, at least one of the pumps is a centrif ugal pump. An advantage is that the pump may have a high flow rate capabilities and relatively simple structure.

In one embodiment, at least one of the pumps is a plunger pump. An advantage is that the pump may be used at high pressures.

In one embodiment, the arrangement comprises at least two ejectors arranged in series, wherein the outlet channel of a preceding ejector is connected to the high-pressure in let of the following ejector. An advantage using multiple ejectors in series is that a lower amount of motive gas is needed to compress the sucked gas to a certain pressure. Alternatively, using multiple ejectors the sucked gas can be compressed to a higher pressure with the same amount of motive gas.

In one embodiment, the arrangement comprises a controlling means arranged to control the first portion of working fluid in relation to a second portion of working fluid be ing fed in the expander. An advantage is that input and output pressures of the expander may be controlled, for instance kept constant even if e.g. the temperature of cooling fluid fluctuates. In one embodiment, the arrangement comprises a generator for generating electricity, and arranged to be rotated by the expander. An advantage is that the heat energy of working fluid may be converted to a more versatile form of energy.

In one embodiment, the arrangement comprises a first con duit system arranged to connect in series: the outlet channel of the ejector, the condenser, the pump, the heat exchanger, and the inlet channel of the expander, the ar rangement further comprising a second conduit system ar ranged to connect with the first conduit system between said heat exchanger and said inlet channel of the expand er, the second conduit system further arranged to connect to the high-pressure inlet of the ejector. An advantage is that the structure of the system is simple and only one pump is needed.

In one embodiment, the arrangement comprises a first con duit system arranged to connect in series: the outlet channel of the ejector, the condenser, the pump, the heat exchanger, and the inlet channel of the expander, the ar rangement further comprising a third conduit system ar ranged to connect with the first conduit system between the condenser and the pump, the third conduit system com prising a second pump, a second heat exchanger, the third conduit system further arranged to connect to the high- pressure inlet of the ejector. An advantage is that it is possible to utilize a lower temperature heat energy for compressing working fluid after the expander, but prior to feeding working fluid in the condenser. Thus, a higher net power production may be achieved.

BRIEF DESCRIPTION OF FIGURES

Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which Figure 1 is a schematic view of a rankine cycle arrange ment, Figure 2 is a schematic side view of another rankine cycle arrangement, and

Figure 3 a schematic side view of a third rankine cycle arrangement.

In the figures, some embodiments are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures.

DETAILED DESCRIPTION Figure 1 is a schematic view of a Rankine cycle arrange ment. The Rankine cycle is an idealized thermodynamic cy cle of a heat engine that converts heat into mechanical work while undergoing phase change. The arrangement 100 comprises an expander 1 for converting heat energy of working fluid into mechanical energy. The expander 1 may comprise e.g. a turbine.

A heat exchanger 2 is connected to an inlet channel 3 of the expander 1 for heating working fluid that is fed in the expander 1 in such an extent that working fluid is evaporating.

In an embodiment, the heat exchanger 2 is a counterflow plate heat exchanger. However, another type of heat ex changers may also be used as the heat exchanger 2.

The heat exchanger 2 comprises a receiving channel 4 being arranged to receive heat energy H from a heat source (not shown). In an embodiment, the heat source is waste heat developed in an industrial plant, in a waste incinerator, or energy producing plant. In another embodiment, the heat is obtained from a solar heating arrangement or a geother mal heat source. The heat energy is carried by a fluid, such as liquid, gas or combination thereof.

A condenser 5 is connected to an outlet channel 6 of the expander 1 for cooling working fluid expanded in the ex pander 1. Working fluid condenses in the condenser 5 to liquid state. In an embodiment, the condenser 5 is a coun terflow plate heat exchanger. However, another type of condensers may also be used as the condenser 5.

The condenser 5 comprises a receiving channel 7 that is arranged to receive cooling fluid C from a cooling fluid source. Said cooling fluid source may be e.g. sea, lake or atmosphere, and the cooling fluid C may comprise e.g. wa ter or some another liquid, gas, such as air, or any of their combinations.

A pump 8 is connected to an outlet 9 of the condenser and to an inlet 10 of the heat exchanger. The pump 8 trans ports working fluid from the condenser 5 to the heat ex changer 2 while raises pressure thereof. In an embodiment, the pump 8 is a centrifugal pump or a plunger pump. Howev er, another type of pumps may also be used.

The arrangement 100 further comprises an ejector 11 having a high-pressure inlet 12, a low-pressure inlet 13, and an outlet channel 14. The ejector 11 is connected in parallel with the expander 1 such that a first portion of working fluid is capable to bypass the expander 1 through said ejector 11.

The low-pressure inlet 13 of the ejector is connected to the outlet channel 6 of the expander. The outlet channel 14 of the ejector is connected to an inlet 15 of the condenser and conducts working fluid from the ejector 11 to the condenser 5.

The high-pressure inlet 12 of the ejector is connected to an outlet 16 of the heat exchanger. In an embodiment, about 10 volume-% of the working fluid coming from the outlet 16 is directed to the high-pressure inlet 12 of the ejector.

Fluid received in the high-pressure inlet 12 may be gase ous fluid, liquid fluid or supercritical fluid.

In an embodiment, a by-pass channel 26 (show by dashed line) is arranged to bypass the heat exchanger 2. Portion of fluid passing the heat exchanger 2 may enter at least partly in liquid form in the ejector 11. Said liquid may condense at least part of the gas fed in the low-pressure inlet 13, i.e. the ejector may be a condensing ejector. An advantage of the condensing ejector is that a higher out let pressure can be achieved when cold motive fluid in liquid form may condense a part of gas sucked from the outlet channel 6 of the expander 1. In addition, less waste heat and a smaller heat exchanger are needed, when all the motive fluid is not vaporized.

The ejector 11 is arranged to use working fluid that is in a higher pressure and coming from the heat exchanger 2 for sucking and compressing working fluid fed from the expand er 1 and having a lower pressure and, further, discharge all the working fluid in an intermediate pressure to the condenser 5. Thus, the pressure of working fluid in the condenser 5 is higher and temperature difference (dT) in the condenser 5 may be increased. In an example, dT was raised from 5 °C to 20 °C, i.e. dT quadrupled. This, in turn, makes it possible to reduce the size of the conden- ser 5 (in said example to one fourth) and lower capital expenses of the condenser 5.

In an embodiment, the arrangement 100 comprises a first conduit system 18 that is arranged to connect in series the outlet channel 14 of the ejector, the condenser 5, the pump 8, the heat exchanger 2, and the inlet channel 3 of the expander, and further a second conduit system 19 ar ranged to connect with the first conduit system 18 between said heat exchanger 2 and said inlet channel 3 of the ex pander and further arranged to connect to the high- pressure inlet 12 of the ejector. Thus, the second conduit system 19 provides a by-pass channel to the expander 1, through which by-pass channel a first portion of heat- transfer fluid is capable to bypass the expander 1.

In an embodiment, the arrangement 100 is provided with a controlling means 17 that is arranged to control the first portion of working fluid in relation to a second portion of working fluid, i.e. the portion being fed in the ex pander 1. The controlling means 17 may comprise e.g. a three-way valve.

The arrangement 100 further comprises a power transmission 23 arranged to be used by the energy of working fluid ex panding in the expander 1. In an embodiment, the power transmission 23 comprises a rotating power transmission axle that is connected to e.g. a generator 24 that gener ates electricity, to a gas compressor, a pump or any appa ratus using rotating mechanical energy.

Figure 2 is a schematic side view of another rankine cycle arrangement. The arrangement 100 comprises the first con duit system 18 described above, thus being arranged to connect in series the outlet channel 14 of the ejector, the condenser 5, the pump 8, the heat exchanger 2, and the inlet channel 3 of the expander. In some embodiments, the arrangement 100 further comprises a third conduit system

20 that connects with the first conduit system 18 between the condenser 5 and the pump 8 and comprises a second pump

21 and a second heat exchanger 22. The third conduit sys tem 20 is further connected to the high-pressure inlet 12 of the ejector. According to an idea, the third conduit system 20, or the second heat exchanger 22 therein, is us ing heat energy H2 being in a lower temperature as the heat energy HI used in the (first) heat exchanger 2 ar ranged in the first conduit system 18. For example, the temperature of the heat energy HI fed in the (first) heat exchanger 2 may be about 80 °C or less, whereas the tem perature of the heat energy H2 fed in the second heat ex changer 22 may be about 40 °C or less. Thus, it is possi ble to utilize a lower temperature heat energy H2 for com pressing working fluid after the expander 1, but prior to feeding working fluid in the condenser 5. This way higher net power production may be achieved.

In an embodiment, the heat energy H2 fed in the second heat exchanger 22 is coming from an outlet of the heat en ergy 1 of the (first) heat exchanger 2. This embodiment is represented by a connecting conduit 25 in Figure 2.

In an embodiment, the working fluid used in the arrange ment 100 is carbon dioxide (CCy). The working fluid may also be practically any fluid used in organic rankine cy cles, such as refrigerants ammonia, hydrocarbons, alcohols etc., or any of their combinations. Preferably, the work ing fluid has a big difference in vapor pressure between evaporation temperature and condensing temperature.

Figure 3 is a schematic side view of a third rankine cycle arrangement. The arrangement 100 may comprise plurality of ejectors arranged in series such that the outlet channel 14 of a preceding ejector is connected to the high- pressure inlet 12 of the following ejector.

The embodiment shown in Figure 3 comprises two ejectors 11a, lib arranged in series.

It is to be noted, that said embodiment of plurality of ejectors arranged in series may be use also in connection with the embodiments described in description of Figure 2.

A controlling means 17, such as a three-way valve, may be arranged to the arrangement 100 for controlling the por tions of the expanded fluid in the outlet channel 6 fed in the ejectors.

The invention is not limited solely to the embodiments de scribed above, but instead many variations are possible within the scope of the inventive concept defined by the claims below. Within the scope of the inventive concept the attributes of different embodiments and applications can be used in conjunction with or replace the attributes of another embodiment or application.

The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in detail within the scope of the inventive idea de fined in the following claims.

REFERENCE SYMBOLS

1 expander 2 heat exchanger

3 inlet channel of expander

4 heat energy receiving channel of heat exchanger

5 condenser

6 outlet channel of expander 7 cooling fluid receiving channel of condenser

8 pump

9 outlet of condenser

10 inlet of heat exchanger 11 ejector 12 high-pressure inlet of ejector

13 low-pressure inlet of ejector

14 outlet channel of ejector

15 inlet of condenser

16 outlet of heat exchanger 17 controlling means

18 first conduit system

19 second conduit system

20 third conduit system 21 second pump 22 second heat exchanger

23 power transmission

24 generator

25 connecting conduit

26 by-pass channel

100 arrangement

H heat energy

C cooling fluid

Claims

1. A rankine cycle arrangement, the arrangement (100) com prising:

- an expander (1) for converting heat energy of working fluid into mechanical energy,

- a heat exchanger (2) connected to an inlet channel (3) of the expander (1) for heating working fluid to be fed in the expander (1), the heat exchanger (2) comprising a re ceiving channel (4) being arranged to receive heat energy, - a condenser (5) connected to an outlet channel (6) of the expander (1) for cooling working fluid expanded in the expander (1), the condenser (5) comprising a receiving channel (7) being arranged to receive cooling fluid,

- a pump (8) connected to an outlet (9) of the condenser and to an inlet (10) of the heat exchanger for rising pressure of working fluid,

- an ejector (11) comprising a high-pressure inlet (12), a low-pressure inlet (13), and an outlet channel (14), the ejector (11) being connected in parallel with the expander (1) such that a first portion of working fluid is capable to bypass the expander through said ejector (11), and wherein

- the outlet channel (6) of the expander is connected to the low-pressure inlet (13), - the outlet channel (14) of the ejector is connected to an inlet (15) of the condenser for conducting working flu id from the ejector (11) to the condenser (5), and

- an outlet (16) of the heat exchanger is connected to the high-pressure inlet (12).

2. The arrangement as claimed in claim 1, wherein the ex pander (1) comprises a turbine.

3. The arrangement as claimed in claim 1 or 2, wherein said working fluid is carbon dioxide (CCy).

4. The arrangement as claimed in any of the preceding claims, wherein said working fluid comprises refrigerant, ammonia, hydrocarbon, alcohol or combination thereof.

5. The arrangement as claimed in any of the preceding claims, wherein the heat exchanger () is a counterflow plate heat exchanger.

6. The arrangement as claimed in any of the preceding claims, wherein the condenser () is a counterflow plate heat exchanger.

7. The arrangement as claimed in any of the preceding claims, wherein at least one of the pumps () is a centrif ugal pump or a plunger pump.

8. The arrangement as claimed in any of the preceding claims, comprising at least two ejectors (11a, lib) ar ranged in series, wherein

- the outlet channel of a preceding ejector (11a) is con nected to the high-pressure inlet of the following ejector (lib).

9. The arrangement as claimed in any of the preceding claims, comprising a controlling means (17) arranged to control the first portion of working fluid in relation to a second portion of working fluid being fed in the expand er (1).

10. The arrangement as claimed in any of the preceding claims, comprising a generator (24) for generating elec tricity, and arranged to be rotated by the expander (1).

11. The arrangement as claimed in any of the preceding claims, comprising - a first conduit system (18) arranged to connect in se ries:

- the outlet channel (14) of the ejector,

- the condenser (5),

- the pump (8),

- the heat exchanger (2), and

- the inlet channel (3) of the expander, and further comprising

- a second conduit system (19) arranged to connect with the first conduit system (18) between said heat exchanger (2) and said inlet channel (3) of the expander, the second conduit system (19) further arranged to connect to the high-pressure inlet (12) of the ejector.

12. The arrangement as claimed in any of claims 1 - 10, comprising

- a first conduit system (18) arranged to connect in se ries:

- the outlet channel (14) of the ejector,

- the condenser (5),

- the pump (8),

- the heat exchanger (2), and

- the inlet channel (3) of the expander, and further comprising

- a third conduit system (20) arranged to connect with the first conduit system (18) between the condenser (5) and the pump (8), the third conduit system (20) comprising

- a second pump (21),

- a second heat exchanger (22),

- the third conduit system (20) further arranged to con nect to the high-pressure inlet (12) of the ejector.