Device for condensing and circulating fluid in system

Abstract

A device for condensing and circulating a fluid in a system comprises a condenser (2) arranged to condense a working fluid from a gas phase to a liquid phase; a fluid pump (5) arranged to pump a liquid working fluid from the condenser; and a piping system (6) connecting the condenser and the fluid pump, where the condenser has a height (H), a longitudinal length (L) and a transverse width (W) and comprises two outlet ports (21a, 21b) for the working fluid arranged on opposite sides of the condenser and in fluid communication with each other via a through conduit (21) extending along the longitudinal length of the condenser, and where the two outlet ports (21a, 21b) are in fluid communication with each other via a through conduit (21) extending along the longitudinal length of the condenser. The fluid pump comprises an inlet (5a) and an outlet (5b). An inlet of the fluid pump is arranged in fluid communication with each of the outlet ports of the condenser through the piping system, and the fluid pump is arranged such that the inlet of the fluid pump is substantially centered between the outlet ports along a longitudinal length of the condenser.

Description

Technical Field

[0001] The present invention relates to an apparatus for condensing and circulating a fluid of a system, and a system incorporating such an apparatus for operating a thermodynamic cycle for converting heat into electrical energy. Background Art

[0002] From WO 2012 / 128715 A1 and WO 2013 / 045021 A2, systems for converting waste heat into electricity using thermodynamic cycles (e.g., organic Rankine cycle (ORC), Kalina cycle, carbon carrier cycle, and / or Carnot cycle) are known. The thermodynamic cycle comprises a liquid working fluid that is heated by the waste heat until it is converted into a gas, which then enters a turbine to perform work (e.g., generate electricity). The working fluid is then condensed into liquid form before being pumped back to exchange heat with a heat source. These solutions provide an efficient method for recovering waste heat from industrial processes that would otherwise be dissipated to the surroundings.

[0003] In recent years, offshore vessels have been identified as an appropriate application for recycling waste heat to reduce their environmental impact. However, the marine environment presents additional challenges for power generation through waste heat conversion compared to land-based solutions. Ocean-going vessels must endure the harsh conditions at sea and experience many ship motions due to incoming waves, including both rotations (roll, pitch, yaw) and translations (roll, pitch, heave). These ship motions affect the performance of onboard systems, especially fluid systems including pumps (e.g., power generation modules). For example, when the ship experiences roll and / or pitch motions that cause the power generation modules to tilt, the liquid level in the system may change dramatically, which may cause cavitation of the fluid pumps, leading to damage and / or failure. Another challenge is the limited space available on board, which in turn places additional space constraints on the power generation modules and their components, which also affects performance.

[0004] Cavitation is a phenomenon that can occur in liquids and involves the formation of vapor bubbles within the liquid in low-pressure areas. These low-pressure areas occur where the liquid has been accelerated to high speeds (such as during the operation of pumps, turbines, and propellers). Cavitation is undesirable because it causes extensive erosion of the rotating blades, the resulting detonation and vibrations create additional noise, and it leads to a significant reduction in efficiency because it disrupts the flow pattern. Cavities form when the pressure of the liquid has dropped to its vapor pressure; as the pressure decreases further with flow, the cavities expand and suddenly collapse when they reach a higher pressure region. The sudden growth and collapse of these vapor cavities results in extreme pressures that dent metal surfaces exposed to the cavitating liquid.

[0005] WO 2011 / 057724 A2 discloses a thermodynamic machine comprising a circulation system, a heat exchanger, an expander, a condenser, and a fluid pump. In the circulation system, a working fluid (particularly a low-boiling-point working fluid) circulates alternately between a gas phase and a liquid phase. To prevent cavitation in the liquid working fluid, a non-condensable auxiliary gas is added to the flow line upstream of the fluid pump, thereby applying partial pressure to the liquid working fluid, which increases the system pressure. However, this solution requires monitoring and controlling the auxiliary gas concentration, and the presence of the non-condensable gas may affect the efficiency of the condenser and expander.

[0006] Furthermore, improved solutions are needed to overcome the disadvantages associated with known thermodynamic systems. Summary of the Invention

[0007] The object of the present invention is to provide an improved device for overcoming all or some of the disadvantages and problems described above in connection with the prior art.

[0008] This object is achieved by the present invention, wherein in a first aspect, there is provided an apparatus for condensing and circulating a fluid in a system, the apparatus comprising: a condenser arranged to condense a working fluid from a vapor phase to a liquid phase; a fluid pump arranged to pump the liquid working fluid from the condenser; and a piping system connecting the condenser and the fluid pump, wherein the condenser has a height, a longitudinal length, and a transverse width, and comprises two outlet ports for the working fluid, the outlet ports being arranged on opposite sides of the condenser and in fluid communication with each other via a through conduit extending along the longitudinal length of the condenser, and wherein the fluid pump comprises an inlet and an outlet. The inlet of the fluid pump is arranged to be in fluid communication with each of the outlet ports of the condenser via the piping system, and the fluid pump is arranged so that the inlet of the fluid pump is substantially centered between the outlet ports along the longitudinal length of the condenser.

[0009] By providing two outlet ports for the working fluid in the condenser, the system of the present disclosure becomes more robust to handle changes in orientation because the working fluid can continue to flow from the condenser with sufficient pressure head above the fluid pump to prevent cavitation. Another advantage of this configuration is that the vertical distance between the fluid pump and the condenser can be reduced because sufficient pump pressure head can always be achieved. The reduced height facilitates the integration of the system in locations with spatial constraints. The relative arrangement of the outlet ports provides an optimal geometry to ensure that the working fluid flows through at least one of the outlet ports regardless of the tilt of the condenser. The central arrangement of the inlet of the fluid pump along the longitudinal length of the condenser reduces or even eliminates the effect of tilt on the fluid level in the piping system, ensuring sufficient pressure head above the fluid pump and preventing cavitation. Furthermore, using this arrangement, a system with a fluid pump and a condenser can be operated under conditions of system tilt while minimizing the impact on pump performance. One such example is a marine vessel.

[0010] In one embodiment, two outlets for the working fluid are arranged at the lower end of the condenser.The arrangement of the outlet ports at the lower end of the condenser ensures that the working fluid can flow through at least one of the outlet ports regardless of the tilt condition of the condenser.

[0011] In one embodiment, the piping system includes a first pipe section and a second pipe section, each pipe section being connected to one of the outlet ports for the working fluid and being connected to the inlet of the fluid pump. Preferably, the first pipe section and the second pipe section are connected to each other upstream of the inlet of the fluid pump. The piping system is configured to minimize the flow losses due to friction in the pipeline by selecting a suitable length and diameter. The upstream connection helps to guide the flow into the fluid pump, thereby ensuring that no matter where the working fluid flows out, it has substantially the same flow conditions at the inlet.

[0012] In one embodiment, the fluid pump inlet is arranged vertically below the condenser and substantially centered along the width of the condenser. The central placement of the fluid pump inlet along the width of the condenser further reduces the effects of tilting in a direction perpendicular to the length. When used on a marine vessel, the apparatus according to this embodiment can minimize the effects of both pitch / trim (rotation about the vessel's longitudinal axis) and roll / heel (rotation about the vessel's transverse axis).

[0013] In a second aspect of the present disclosure, there is provided a system for operating a thermodynamic cycle to convert heat into electrical energy, the system comprising: an evaporator arranged to evaporate a working fluid from a liquid phase to a gas phase; a turbine arranged to be rotated by the working fluid in the gas phase; a generator arranged to convert the turbine rotation into electrical energy; and an apparatus according to the first aspect.

[0014] In one embodiment, a fluid pump is disposed downstream of the condenser and is configured to circulate the working fluid in the system to maintain the liquid level in the condenser during use of the system.

[0015] In one embodiment, the inlet of the fluid pump is arranged at a height below the condenser. Preferably, this height is selected so that the head pressure loss in the piping system during use of the system is less than the vertical distance from the inlet of the fluid pump to the liquid level in the condenser. Thus, an optimal size of the system is achieved that balances the requirements of reducing size and maintaining sufficient suction head pressure.

[0016] In one embodiment, the components are mounted on a frame to form a power generation module having a substantially rectangular parallelepiped shape. The modular construction of the system facilitates installation and connection of the system in pre-existing structures and industrial applications (e.g., for converting waste heat in marine vessels).

[0017] In a third aspect of the present disclosure, there is provided a use of the thermodynamic cycle system according to the second aspect to convert heat from a marine vessel engine into electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0019] Figure 1 shows a schematic diagram of a system for operating a thermodynamic cycle according to the present disclosure;

[0020] Figure 2a and Figure 2b A schematic diagram of an apparatus for condensing and circulating a fluid in a system according to one embodiment of the present disclosure is shown;

[0021] Figure 3a and Figure 3b A schematic diagram illustrating an apparatus for condensing and circulating a fluid in a system according to one embodiment of the present disclosure; and

[0022] Figure 4a and Figure 4b A schematic diagram of an alternative arrangement is shown. DETAILED DESCRIPTION

[0023] Hereinafter, a detailed description of a thermodynamic system according to the present disclosure is presented. In the accompanying drawings, similar reference numerals represent identical or corresponding elements in several drawings. It will be understood that these drawings are for illustration only and do not limit the scope of the present invention in any way.

[0024] refer to Figure 1, schematically illustrates an exemplary system for operating a thermodynamic cycle to convert heat into electrical energy according to the present disclosure. The cycle can be an organic Rankine cycle (ORC), a Kalina cycle, a carbon carrier cycle, and / or a Carnot cycle. System 10 includes an evaporator 1, a condenser 2, a turbine 3, a generator 4, and a fluid pump 5. The fluid pump 5 is arranged downstream of the condenser 2 and is configured to circulate the working fluid in the system 10. After leaving the condenser 2, the working fluid in liquid form is directed to the evaporator 1, where it undergoes a phase change to a gaseous form under high pressure under the influence of heat from an external heat source HS. The gaseous working fluid is then directed to the turbine 3 to cause it to rotate, which is transferred to the generator 4 to be converted into electrical energy. After passing through the turbine 3, the working fluid returns to the condenser 2, where it undergoes a phase change back to liquid form by cooling provided by an external cold source CS.

[0025] like Figure 1 As shown, the condenser 2 comprises two outlet ports 21a, 21b for the working fluid, preferably arranged at the lower end of the condenser 2. The inlet of the fluid pump 5 is arranged to be in fluid communication with each of the outlet ports 21a, 21b via a pipe system 6. The pipe system 6 comprises a first pipe section 6a connected to the first outlet port 2a and a second pipe section 6b connected to the second outlet port 2b. Both pipe sections 6a, 6b are connected to the inlet of the fluid pump 5 to ensure fluid communication, or as Figure 1 They are shown as being connected separately or in a common configuration in which the line sections 6 a , 6 b are connected to one another upstream of the inlet of the fluid pump 5 .

[0026] Now refer to Figure 2a and 2b , respectively, shows a side view and an end view for a system (e.g., Figure 1 The condenser has a height H, a length L in the longitudinal direction, and a width W in the transverse direction. As shown by the arrow, a through conduit 23 is formed at the upper end of the condenser 2, which is arranged to receive the working fluid in the gas phase. On the contrary, a through conduit 21 (also shown as Figure 3a to Figure 3b and Figures 4a to 4b ), which has outlet ports 21a, 21b arranged at opposite ends for allowing the condensed working fluid to exit the condenser in the liquid phase, as indicated by the double-headed arrows. The liquid working fluid is guided toward the inlet 5a of the fluid pump 5 through the respective first and second pipe sections 6a, 6b before exiting the fluid pump 5 through the outlet 5b.

[0027] The fluid pump 5 is arranged at a height h below the condenser 2 so that the inlet 5a of the fluid pump 5 is substantially centered along the length L of the condenser 2 in the longitudinal direction, i.e., at a distance of approximately L / 2±20%, more preferably L / 2±10%, and most preferably L / 2±5% from each end. The central arrangement of the fluid pump 5 provides a symmetrical configuration that serves to further reduce the effect of tilt on the liquid level of the working fluid in the condenser 2, thereby providing substantially equal performance regardless of the direction of tilt along the longitudinal direction.

[0028] like Figure 2b As shown, in addition to conduits 21 and 23, the condenser further includes corresponding through-conduits 22 and 24 located at the lower and upper ends of the condenser 2, respectively. Conduits 22 and 24 are arranged to guide a cooling fluid from an external cold source CS through the condenser 2. The cooling fluid is arranged to cool the working fluid in gaseous form entering conduit 23, and the working fluid changes phase to become liquid and is collected in conduit 21 and the bottom of the condenser 2, up to a liquid level FL. Figure 2b The arrows in FIG. 2 indicate a generally downward flow direction of the working fluid from the upper portion (conduit 23) toward the lower portion (conduit 21) of the condenser 2, and a generally upward flow direction of the cooling fluid from the lower portion (conduit 22) toward the upper portion (conduit 24). However, it is contemplated that the cooling fluid may be directed to flow through the condenser 2 in the opposite (downward) direction.

[0029] Furthermore, the fluid pump 5 is arranged below the condenser 2 such that the inlet 5a of the fluid pump 5 is substantially centered along the width W of the condenser 2 in the transverse direction, i.e., at a distance of approximately W / 2±20%, more preferably W / 2±10%, and most preferably W / 2±5% from each side. To this end, the first and second conduit sections 6a, 6b may be curved (as shown by bends 25a, 25b) to connect with the inlet 5a. The central arrangement of the fluid pump 5 provides a symmetrical configuration, which serves to further reduce the effect of tilt on the liquid level of the working fluid in the condenser 2, thereby providing substantially equal performance regardless of the direction of tilt in the transverse direction.

[0030] Now refer to Figure 3a and Figure 3b , shows a schematic diagram of a condenser 2 and a fluid pump 5 in a horizontal orientation and an inclined orientation, respectively, according to another embodiment of the present disclosure. The condenser 2 can be configured as a plate heat exchanger having a plurality of plates (not shown) stacked together as known in the art. Each plate includes a plurality of openings that are aligned with each other when the plates are stacked to form corresponding through-ducts or channels 21. Thus, the ducts 21 extend in the longitudinal direction of the plate heat exchanger. As shown in FIG. Figure 3a and Figure 3bAs shown, the outlets 21 a , 21 b are arranged on opposite sides of the condenser 2 and are in fluid communication with each other via a conduit 21 .

[0031] During operation of the system 10, a certain amount of working fluid will be present in the condenser 2. Figure 3a and Figure 3b This is shown by the line FL indicating the liquid level in the condenser 2. In equilibrium conditions of the system 10, the amount of working fluid in the condenser 2, and therefore the liquid level FL, will be substantially constant.

[0032] Now refer to Figure 3a , the condenser 2 is shown in a horizontal orientation with a vertical distance between the inlet of the fluid pump 5 and the liquid level FL during operation. Under these operating conditions, the flow rate of the liquid working fluid through each of the pipe sections 6a, 6b is substantially equal, i.e., approximately half Q / 2 of the total flow rate Q entering the fluid pump 5.

[0033] exist Figure 3b In FIG, the condenser 2 is shown in an inclined or slanted orientation at an angle α to the horizontal during operation, for example, this situation corresponds to a marine vessel subjected to ship motion at sea. Depending on the angle α, this inclination affects the amount of flow of the working fluid through the respective pipe sections 6a, 6b. If α becomes significant (about 15-20° or more), the working fluid is exclusively discharged from the lower outlet port ( Figure 3b 21b) flows, thereby generating a total flow rate Q through pipe section 6b. At the same time, due to the inclination, the vertical distance between the inlet of fluid pump 5 and liquid level FL is reduced compared to the vertical distance in the horizontal direction. The reduced vertical distance can be calculated using the following trigonometric relationship:

[0034] Δz=f(α)=Δz0cosα, and

[0035] Δz=Δz0-δz incl

[0036] Where Δz0 is the vertical distance when horizontally oriented (i.e. when α=0), δz incl is the vertical displacement of the inlet of the fluid pump 5 due to the tilt. Combining the two expressions, the vertical displacement δz caused by the tilt incl The definition is as follows:

[0037] δz incl =Δz0(1-cosα),

[0038] Now refer to Figure 4a and Figure 4b , showing schematic diagrams of the condenser 2 and the fluid pump 5 in a horizontal orientation and an inclined orientation, respectively. Figure 3a and Figure 3bSimilarly, the condenser 2 can also be configured as a plate heat exchanger. However, in this example, the fluid pump 5 is offset from the center of the condenser 2 by a distance d in the longitudinal direction. In this case, the vertical displacement of the fluid pump 5 will have two components, the first component δz due to the tilt incl and the second component δz due to the deviation from the center off .

[0039] The reduced vertical distance can then be calculated using the following trigonometric relationship:

[0040] Δz=f(α,d)=Δz0-δz incl -δz off ,

[0041] δz incl =Δz0(1-cosα), and

[0042] δz off =d sin α

[0043] The liquid level FL and the vertical distance Δz between the inlet of the fluid pump 5 and the liquid level FL play an important role in ensuring that cavitation is avoided. Suction cavitation occurs when the pump suction side is subject to low pressure / high vacuum conditions, and the liquid turns into vapor at the eye of the pump impeller. This vapor is carried to the discharge side of the pump, where it is no longer under vacuum and is compressed back into liquid by the discharge pressure. This implosion occurs violently and attacks the surface of the impeller.

[0044] One quantity used to analyze cavitation conditions in hydraulic circuits is the Net Positive Suction Head (NPSH) margin, which must be positive to prevent cavitation in the pump. The NPSH margin is the absolute pressure at the suction port (inlet) of the pump (called the Net Positive Suction Head Available (NPSH)). A )) and the minimum pressure required at the suction port to prevent pump cavitation (called the required net positive suction head (NPSH) R )).

[0045] NPSH at the pump inlet located below the surface of the fluid being pumped A It consists of three components, the head due to the static pressure of the fluid, the displacement head (vertical distance) due to the weight of the fluid, and the friction head (head loss) due to friction acting to resist the motion of the fluid, and is defined as:

[0046] NPSH A =h vap +Δz-h L ,

[0047] Among them, the pressure head can be rewritten as:

[0048]

[0049] Where p0 is the absolute pressure at the liquid surface of the pumped fluid, p v is the vapor pressure of the fluid, ρ is the fluid density, g is the acceleration due to gravity, Δz is the vertical distance between the pump inlet and the liquid surface, and h L The head loss is caused by the friction experienced by the fluid as it flows through the pipe to the pump and is a function of the fluid flow rate Q and the pipe size. It can be seen that both the head and the vertical distance Δz have an effect on NPSH due to the pressure and gravity acting on the fluid. A makes a positive contribution, while the head loss due to friction makes a negative contribution. NPSH R Usually determined empirically as a function of flow rate and pump characteristics and provided by the manufacturer.

[0050] The NPSH margin is required to be positive, that is, NPSH A Should be greater than NPSH R :

[0051] NPSH A >NPSH R →h L <h vap +Δz-NPSH R

[0052] And it is sufficient to supply from one outlet port at a time:

[0053] h L (Q,D)<Δz

[0054] It is possible to determine which head loss is required to overcome the friction head for a given diameter and length of pipe under given operating conditions. In other words, the spacing or height h between the fluid pump 5 and the condenser 2 is selected to ensure that the head loss h L During use of the system 10, the vertical distance Δz from the inlet of the fluid pump 5 to the liquid level FL in the condenser 2 is always less than in the piping system 6. Therefore, the required NPSH A At the same time, the distance h between the fluid pump 5 and the condenser 2 is minimized so that the overall height of the system 10 is reduced.

[0055] In one embodiment, the components of system 10 are mounted on a frame to form a power generation module having a substantially rectangular parallelepiped shape. This power generation module provides a structure that can be easily integrated into existing structures or industrial applications to convert waste heat into electricity.

[0056] A preferred embodiment of the thermodynamic system has been disclosed above. However, a person skilled in the art realizes that this may be varied within the scope of the appended claims without departing from the spirit of the invention.

[0057] Without departing from the spirit of the present invention, all the alternative embodiments or parts of the embodiments described above may be freely combined with one another or used separately as long as the combination is not contradictory.

Claims

1. A device for condensing and circulating a fluid in a system, the device comprising a condenser (2), a fluid pump (5) and a piping system (6), the condenser (2) being arranged to condense a working fluid from a gas phase to a liquid phase, the fluid pump (5) being arranged to pump the working fluid in liquid phase from the condenser (2), the piping system (6) connecting the condenser (2) and the fluid pump (5), wherein the condenser (2) has a height (H), a longitudinal length (L) and a transverse width (W), and the condenser (2) comprises two outlet ports (21a, 21b) for the working fluid, the two outlet ports (21a, 21b) being arranged on opposite sides of the condenser (2) and being in fluid communication with each other via a through conduit (21) extending along the longitudinal length (L) of the condenser (2), and wherein the fluid pump (5) comprises an inlet (5a) and an outlet (5b), characterized in that The inlet (5a) of the fluid pump (5) is arranged to be in fluid communication with each of the outlet ports (21a, 21b) of the condenser (2) through the pipe system (6), and the fluid pump (5) is arranged so that the inlet (5a) of the fluid pump (5) is substantially centered between the outlet ports (21a, 21b) along the longitudinal length (L) of the condenser (2).

2. The device according to claim 1, wherein two outlets (21a, 21b) for the working fluid are arranged at the lower end of the condenser (2).

3. An apparatus according to claim 1 or 2, wherein the pipe system (6) comprises a first pipe section (6a) and a second pipe section (6b), each pipe section being connected to one of the outlet ports (21a, 21b) for the working fluid and to an inlet (5a) of the fluid pump (5).

4. The device according to claim 3, wherein the first conduit section (6a) and the second conduit section (6b) are connected to each other upstream of the inlet (5a) of the fluid pump (5).

5. The device according to any of the preceding claims, wherein the inlet (5a) of the fluid pump (5) is arranged vertically below the condenser (2) and substantially centered along the width (W) of the condenser (2).

6. A system (10) for operating a thermodynamic cycle to convert heat into electrical energy, the system comprising an evaporator (1), a turbine (3), a generator (4), and an apparatus according to any one of the preceding claims, wherein the evaporator (1) is arranged to evaporate a working fluid from a liquid phase into a gas phase, the turbine (3) is arranged to be rotated by the generated gas phase working fluid, and the generator (4) is arranged to convert the turbine rotation into electrical energy.

7. The thermodynamic cycle system (10) according to claim 6, wherein the fluid pump (5) is arranged downstream of the condenser (2) and is configured to circulate the working fluid in the system (10) to maintain the liquid level (FL) in the condenser (2) during use of the system (10).

8. The thermodynamic cycle system (10) according to claim 6 or 7, wherein the inlet (5a) of the fluid pump (5) is arranged at a height (h) below the condenser (2).

9. Thermodynamic cycle system (10) according to claim 8, wherein the height (h) is selected so that the head loss (h L ) is smaller than the vertical distance (Δz) from the inlet (5a) of the fluid pump (5) to the liquid level (FL) in the condenser (2).

10. The thermodynamic cycle system (10) according to any one of claims 6 to 9, wherein all components are mounted on a frame to form a power generation module having a substantially rectangular parallelepiped shape.

11. Use of a thermodynamic cycle system (10) according to any one of claims 6 to 10 for converting heat from a marine vessel engine into electrical energy.

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