EP3329191A1

EP3329191A1 - Apparatus and method for carrying out a cold steam process

Info

Publication number: EP3329191A1
Application number: EP16748095.3A
Authority: EP
Inventors: Joerg Nickl
Original assignee: Bitzer Kuehlmaschinenbau GmbH and Co KG
Current assignee: Bitzer Kuehlmaschinenbau GmbH and Co KG
Priority date: 2015-07-31
Filing date: 2016-07-29
Publication date: 2018-06-06
Anticipated expiration: 2036-07-29
Also published as: AU2016302538A1; EP3329191B1; US20180149391A1; AU2016302538B2; JP6998298B2; BR112018002125B1; CN107949756A; DE102015214705A1; US10254018B2; CN107949756B; WO2017021293A1; BR112018002125A2; JP2018521295A

Abstract

The present invention relates to an apparatus and to a method for carrying out a cold steam process. The apparatus has a motor-operated primary compressor (C1) which is designed to draw in a mass flow of a fluid, serving as refrigerant, at evaporator pressure and to compress this mass flow to high pressure, and a high-pressure heat exchanger (H) which is designed to cool the mass flow of the fluid at high pressure, to increase the density and to reduce a temperature of the fluid. Also provided is an expander (E) which is designed to expand to evaporator pressure, so as to perform work, the mass flow of the fluid coming from the high-pressure heat exchanger (H), and an evaporator (V) which is designed to take up heat such that the density of the fluid decreases as it passes through the evaporator and the temperature of the mass flow coming from the expander (E) at evaporator pressure, and of the fluid guided through the evaporator (V), increase. Finally, there is a sub-cooler (U), which is connected downstream of the high-pressure heat exchanger (H) and upstream of the expander (E), wherein downstream of the sub-cooler (U) and upstream of the expander (E) part of the fluid can be diverted from the mass flow and can be expanded by means of a high-pressure control valve (TH) to an intermediate pressure, such that the fluid then, at intermediate pressure, absorbs heat in counter-flow in the sub-cooler (U), and thus additionally sub-cools the mass flow which is at high pressure, and a high-pressure compressor (C2) which is mechanically directly connected to the expander (E) and is designed to compress, to high-pressure, only that part of the fluid that is diverted upstream of the expander (E) in the sub-cooler (U) and guided in counter-flow, and to mix this fluid, upstream of the high-pressure heat exchanger (H) with the mass flow coming from the motor-operated primary compressor (C1).

Description

Apparatus and method for performing a cold vapor process

The present invention relates to an apparatus and a method for performing a cold vapor process.

Cold vapor processes with carbon dioxide as a refrigerant are known and are increasingly used due to the favorable properties of carbon dioxide in terms of the greenhouse effect. To increase the coefficient of performance of such a C0 ₂ -Kaltdampfprozesses by using a work-expansion is known for example from the document EP 1 812 759 Bl. A disadvantage of this known solution, however, is that a complicated frequency control is used to influence the high pressure. In addition, a so-called hydraulic pressure booster from Quack, H .; Kraus, WE: Carbon Dioxide as a Refrigerant for Railway Refrigeration and Air Conditioning, Proceedings of the IIR Conference New Application of Natural Working Fluids in Refrigeration and Air Conditioning, Hannover, Germany 1994, pp. 489-494. The present invention is therefore based on the object of proposing a device and a method for carrying out a cold vapor process, with which a simplified control and regulation of the cold steam process is possible.

This object is achieved by a device according to claim 1 and a method according to claim 9. Advantageous embodiments and further developments are described in the dependent claims.

An apparatus for performing a cold vapor process comprises a main engine-driven compressor configured to draw a mass flow of a refrigerant fluid at evaporator pressure level and to compress this mass flow to a high pressure level. In addition, a high-pressure heat exchanger is provided to the

Mass flow of the fluid, which is at high pressure level, to cool, to increase a density thereof and to reduce a temperature of the fluid by the cooling. The coming from the high-pressure heat exchanger mass flow of the fluid is working in an expander on

Evaporator pressure level relaxed and fed to an evaporator. Of the

Evaporator is designed to absorb heat so that the density of the fluid as it passes through the evaporator decreases and the temperature of the coming of the expander mass flow, which is on

Evaporator pressure level is and passes through the evaporator rises. Finally, a downstream of the high pressure heat exchanger and the

Expander upstream subcooler provided. After the subcooler and before the expander part of the mass flow of the fluid, which is located at high pressure level, branched off and by means of a high pressure control valve at medium pressure level, so that the fluid then absorbs heat to mid-pressure level in countercurrent in the subcooler and thereby the mass flow, the at high pressure level, subcooled in subcooler. A high-pressure compressor, which is mechanically directly connected to the expander, is designed to exclusively control the mass flow of the fluid passing between the subcooler and in front of the expander and countercurrent to that of the subcooler

High-pressure level is located, guided mass flow of medium-pressure level Compress high pressure level and mix in front of the high-pressure heat exchanger to the mass flow of the fluid coming from the motor-driven main compressor. By the described device is an efficient control of the high pressure, which is typically applied to the high pressure heat exchanger, the high pressure compressor and partially to the subcooler possible. Because the high-pressure compressor additionally driven directly by the expander compresses only a separate mass flow of the fluid, the medium-pressure mass flow, the mass flow passed through the expander, which comes from the high-pressure heat exchanger, can be additionally subcooled. The exergy of the expansion is thus ultimately used for additional supercooling at high pressure or a performance of the expander serves to compress the medium-pressure mass flow in the high-pressure compressor.

After the expander (and thus before the evaporator), a collector may be arranged. This is adapted to separate a liquid phase of the fluid and a vapor phase of the fluid. The liquid phase of the fluid can be stored in the collector and can be relaxed to evaporator pressure via an injection valve arranged between the collector and the evaporator.

The vapor phase of the fluid can be relaxed via a pressure-holding valve. The expanded liquid phase can be supplied to the evaporator in the mass flow, while the expanded vapor phase after the evaporator can be mixed into the mass flow of the fluid coming from the evaporator.

It can be provided that the expander and the high-pressure compressor are arranged in a common housing and form a unit, which is also referred to as "expander-compressor unit". The arrangement in a single housing allows a space-saving design, in which the expander and the high pressure compressor are mechanically directly, in particular pressure-tight connected to each other.

A displacement ratio between the expander and the high-pressure compressor should preferably be between 0.5 and 0.75 in order to ensure an optimal course of the cold vapor process. Particularly preferably, the displacement ratio is 0.6. Basically, lower values for high he re-cooling temperatures at the outlet of Hochdruckwämreübertragres meaningful application.

Alternatively or additionally, working spaces of the expander can be controlled via a main slide and an auxiliary slide. The main slide and the auxiliary slide are in this case arranged centrally between the usually inner, ie mutually facing working spaces of the expander.

Preferably, the main slide and or or the auxiliary slide are designed as flat slide to ensure a simple and very dense operation with only a small footprint.

It can also be provided that the auxiliary slide of working piston is movable by two pins.

Typically, a piston rod which holds the working piston at a distance, releasably connected to the working piston, that is not firmly connected to these. This is manufacturing technology simple yet functional, since the internal piston rod experiences only compressive forces and thus does not have to be firmly connected to the piston or. As a result, minor misalignment of housing parts can be accepted and the production is facilitated. In the same way, a main slide unit consisting of the main slide, a slide rod and a slide piston can also be constructed. Likewise, an auxiliary slide unit consisting of the auxiliary slide and the pins can be constructed in the same way.

It can be provided to perform the expander in several stages, including in particular several successively connected expander to be understood, which perform an expansion in several stages, with an older type to DE 102 42 271 B3 offers without frequency control.

It can occur in the described device four pressure levels, which typically occupy the value ranges described below: a high pressure level between 50 bar and 100 bar, a medium pressure level between 40 bar and 65 bar, a collector pressure level between 30 bar and 35 bar and an evaporator pressure level between 25 bar and 30 bar.

A method of performing a cold vapor process comprises a step of controlling a mass flow of a fluid serving as a refrigerant, which is at an evaporator pressure level, by a motor-driven one

Main compressor is compressed to high pressure level. This mass flow of the fluid, which is at high pressure level, is cooled in a high pressure heat exchanger, increasing density and lowering a temperature of the fluid. The coming of the high-pressure heat exchanger fluid is working in an expander

Evaporator pressure level relaxed, the expander is mechanically connected directly to a high pressure compressor. The fluid coming from the expander is passed into an evaporator where it absorbs heat, so that the density of the fluid decreases and the temperature of the mass flow of the fluid coming from the expander, which increases

Evaporator pressure level is increasing. After the high pressure heat exchanger and before the expander, the fluid is passed through a subcooler, wherein between the subcooler and before the expander, a portion of the fluid from the high pressure level mass flow is diverted and expanded by means of a high pressure control valve to medium pressure level. Subsequently, the fluid is passed in countercurrent to the passed through the subcooler mass flow, which is at high pressure level, at medium pressure level through the subcooler, wherein it absorbs heat and the mass flow, which is at high pressure level, is undercooled. After passing through the subcooler, the fluid passes in the branched

Medium pressure mass flow to the high pressure compressor, which compresses only the countercurrent fluid from medium pressure level to high pressure level and admixed before the high pressure heat exchanger coming from the motor-driven main compressor mass flow.

It can be provided that the fluid is led to the expander in a collector, in which a liquid phase of the fluid is separated from a vapor phase of the fluid. The liquid phase is expanded to evaporator pressure via an injection valve. The vapor phase of the fluid is released via a pressure-holding valve and admixed downstream of the evaporator into the mass flow of the fluid coming from the evaporator. As a fluid, which is also referred to as a refrigerant in this context, carbon dioxide, C0 ₂ , can be used because carbon dioxide is not explosive and non-combustible, but thermally stable. As a refrigerant, its advantages include a low specific volume and a high heat transfer coefficient and low pressure losses in a flow through heat exchangers.

The described method can be carried out with the described device or the described device is set up to carry out the described method.

Embodiments of the invention are illustrated in the drawings and are explained below with reference to Figures 1 to 12.

Show it:

Fig. 1 is a schematic representation of a process control of a cold vapor process and

FIG. 2 is a schematic view corresponding to FIG. 1 of the process control without a collector; FIG.

Fig. 3 is a cross-sectional view of an expander-compressor unit;

4 is a side view of a piston rod including working piston.

Fig. 5 is a sectional view through one end of the expander compressor unit;

Fig. 6 is a sectional view of a central part of the expander-compressor unit shown in Fig. 3;

Fig. 7 is a side view corresponding to Figure 4 of the main slide including slide rod and piston.

8 is an enlarged view of the auxiliary slide including pins. FIG. 9 is a view corresponding to FIG. 4 of an auxiliary slide together with pins; FIG.

10 is a plan view of a sealing frame including O-rings.

11 is an enlarged view of the main spool in plan view and

Fig. 12 is a plan view of another sealing frame including O-ring.

FIG. 1 shows a schematic representation of a process control of a cold vapor process. In the lower part of Figure 1, a low pressure circuit is shown, in which coming from a collector S through an injection valve TV, a fluid, in the illustrated embodiment, carbon dioxide, passes through an evaporator V to a motor-driven main compressor Cl. The fluid compressed by the main compressor Cl mixes with a medium-pressure mass flow of the fluid compressed by a high-pressure compressor C2 in front of the high-pressure heat exchanger H, in which a higher pressure than in the collector S is maintained. From the high pressure heat exchanger H, the fluid passes through a subcooler U and the expander E back into the collector S.

In the illustrated process control, however, a separate medium-pressure mass flow is compressed by the high-pressure compressor C2 driven directly by the expander E before it enters the high-pressure heat exchanger H. The high-pressure compressor C2 compresses only this medium-pressure mass flow, so no fluid that is out of the medium-pressure mass flow. After the high-pressure heat exchanger H, which is also referred to as a gas cooler or condenser, the fluid flowing straight from the high-pressure heat exchanger H and into a subcooler U lying between the high-pressure heat exchanger H and the expander E is divided after passing through the subcooler U. A smaller part, typically between

15 percent and 30 percent are throttled in a throttle TH, also referred to as a high pressure regulator. Subsequently, the branched fluid in the subcooler U in countercurrent heat and reaches the high pressure compressor C2. As a result, the high-pressure mass flow of the fluid is additionally undercooled. The exergy of the expansion is thus an additional undercooling at high pressure. Finally, the medium pressure mass flow compressed by the high pressure compressor C2 back to high pressure before the high pressure heat exchanger H is added to the fluid coming from the main compressor C1. By the diversion of the high-pressure control valve TH directly in front of the expander E also reduces unwanted pulsations in the "liquid part" at high pressure level and has in comparison to the known branch between the high-pressure heat exchanger H and the subcooler U continues to have energy advantages in some operating points.

In this case, a pressure difference and a suction volume flow can be set freely on the high-pressure compressor C2 in accordance with an offer on the expander side. If the high-pressure control valve or throttle TH is closed, its pressure difference increases until the sketched expander compressor unit stops and no expander mass flow is no longer present. The result is an increasing high pressure. If the high-pressure control valve TH now slowly opened, the medium pressure increases again, until the expander E is running and the desired expander mass flow, high pressure and

Set expander inlet temperature. However, the high pressure should only be increased so far that a minimum temperature difference on the "hot side" of the subcooler U, d. H. high pressure compressor side, remains. That is another rule of law. The expander mass flow is thus regulated without throttling it, which would equate to exergy loss.

The collector pressure in the collector S is selected to be sufficiently high to ensure sufficient controllability of the injection valve TV and of a pressure-maintaining valve TS arranged in a line connected between a vapor space of the collector S and downstream of the evaporator V collector and upstream of the main compressor C1. At a constant

Evaporator pressure allows a constant low collector pressure, regardless of the high pressure.

With the device or a corresponding method illustrated in FIG. 1 in one exemplary embodiment, a coefficient of performance at -10 ° C. evaporation temperature and 20 ° C. ambient temperature can be reduced by approx. 15 percent compared to a simple cold steam process in which only a compressor, a high-pressure gas cooler or condenser, a throttle valve, a collector and an evaporator are used in a known manner, be increased. The high pressure remains at comparable values. To get an even bigger boost, there can be more

Exergieverluste be reduced by a two-stage compression with intermediate cooling, with a residual process or the rest of the structure remains the same. In addition, it is possible to perform the expander E multi-stage, d. H. the

Expire expansion of the fluid in multiple stages. For this example, several individual expander E can be arranged one behind the other. For this, the known construction from DE 102 42 271 B3 offers without frequency control.

FIG. 2 shows, in a view corresponding to FIG. 1, the described process control without the collector S. Recurring features are provided with identical reference symbols in this figure as well as in the following figures. The expander E thus directs the fluid directly to the evaporator V, without the fluid previously passing through the collector S. Accordingly, that too

Injector TV and the pressure maintenance valve TS obsolete.

Figure 3 shows a side view of a cross section through an expander compressor unit from the expander E and the high pressure compressor C2, which are arranged in a common housing 10 and thus the

Form the expander compressor unit. Two pistons 1 and 2 are held by a piston rod 3 at a distance and spatially separated from each other by a central part 4 of the unit. As a result, form several work spaces, of which in the example shown, however, only the workrooms 5.1 and 6.2 can be seen at maximum working space. The workspace 5.1 and the

Workspace 5.2 is in each case one of two expander workrooms, while the workspace 6.1 and 6.2 is in each case one of two compressor workrooms. The optimal stroke volume ratio of the illustrated unit has been found to be between 0.5 and 0.75.

In the illustrated embodiment, the internal Expander working spaces 5.1 and 5.2 via a arranged in the middle part 4 auxiliary slide 9 and a main slide 8 controlled. In this case, the auxiliary slide 9 is moved directly from the working piston 1 and 2 by pins 7. The auxiliary slide 9 then changes a pressurization on the main spool 8, which thereby moves and controls an inflow opening and an outflow opening for the working spaces 5.1 and 5.2 of the expander E by opening and closing. The main slide 8 and the auxiliary slide 9 are designed in an advantageous manner as a flat slide.

In the compressor workrooms 6.1 and 6.2 simple ball valves are arranged. Since the piston rod 3 undergoes only compressive forces in the illustrated embodiment, the piston rod 3 is not fixed, but releasably connected to the piston 1 and 2 by the piston 1 and 2 touch the piston rod 3 only on the face or surface. This is shown in Figure 4 in a side view, in which the working piston 1 and 2 are separated from the piston rod 3. In other embodiments, but of course there may be a fixed connection. The illustrated construction thus also allows use of O-rings on otherwise difficult to seal sites.

FIG. 5 shows a sectional view along the line B-B of FIG. 3 through an end piece of the expander-compressor unit. A compressor valve configured as a ball valve is connected to an upper connection on the high-pressure side and with its lower connection to the medium-pressure level of the subcooler U.

FIG. 6 shows a sectional view of the central part 4 of the expander / compressor unit shown in FIG. 3 along the line A-A. An upper port carries the fluid from the high pressure level of the subcooler U, while the lower port leads to the collector S. The main slide 8 is over a

Slider rod 11 connected to a spool 12, wherein this connection is detachable. This is also shown in a side view in Figure 7, in which the main spool 8, the spool rod 11 and the spool 12 are shown as separate and separate components.

The auxiliary slide 9 together with the to his operation by the working piston. 1 and 2 inserted pins 7 is shown in Figure 8 along a line DD of Figure 3. FIG. 9 shows, in a view corresponding to FIG. 4, the auxiliary slide 9 and the two pins 7 in a separate manner, by means of which the auxiliary slide 9 can be moved.

FIG. 10 shows a top view of a sealing frame 13 with two O-rings 14 and 15 for the auxiliary slide 9, which are arranged in openings in the sealing frame 13 when installed. In FIG. 11, the main slide 8 together with slide rod 11 and slide piston 12 are shown in plan view along the line C-C of FIG. In the same way as in FIG. 10, FIG. 12 shows a further sealing frame 16 with O-ring 17 for the main slide 8. The construction described just allows the use of O-rings on surfaces which are difficult to be sealed (namely around the main slide 8 and the auxiliary slide 9), so that a pocket milling is avoided by appropriate support frame.

Claims

claims

Apparatus for performing a cold vapor process with a main engine driven compressor (Cl) adapted to draw a mass flow of a refrigerant fluid at evaporator pressure level and to compress said mass flow to high pressure level, a high pressure heat exchanger (H) arranged to cool the mass flow of the fluid, which is at high pressure level, to increase a density and to reduce a temperature of the fluid, an expander (E) adapted to perform the mass flow of the fluid coming from the high pressure heat exchanger (H) to the evaporator pressure level to relax, an evaporator (V) adapted to absorb heat so that the density of the fluid as it passes through the evaporator (V) decreases and the temperature of the mass flow coming from the expander (E), which is at evaporator pressure level, and of the guided through the evaporator (V) fluid rise, a the High pressure heat exchanger (H) downstream and the expander (E) upstream subcooler (U), after the subcooler (U) and before the expander (E), a part of the mass flow of the fluid, which is at high pressure level, branched off and by means of a high pressure control valve ( TH) is depressurable to medium pressure level, so that the fluid subsequently absorbs heat at a medium pressure level in countercurrent in the subcooler (U) and in this case absorbs the mass flow, which is at high pressure level, subcooled, a high pressure compressor (C2) mechanically directly connected to the expander (E) and arranged, excluding the upstream of the expander (E) branched off and in countercurrent to the subcooler (U) passing through the mass flow of the fluid, on High-pressure level is to compacted mass flow, which is located at medium-pressure level, and to mix before the high-pressure heat exchanger (H) coming from the main engine-driven compressor (Cl) mass flow.

2. Apparatus according to claim 1, characterized in that after the expander (E) a collector (S) is arranged and adapted to separate a liquid phase of the fluid and a vapor phase of the fluid, the liquid phase storable, via an injection valve (TV) Relaxed to evaporator pressure and the vapor phase of the fluid via a pressure relief valve (TS) is relaxed, the relaxed liquid phase to the evaporator (V) can be supplied and the relaxed vapor phase after the evaporator (V) in the mass flow of the fluid coming from the evaporator can be mixed.

3. Apparatus according to claim 1 or claim 2, characterized in that the expander (E) and the high-pressure compressor (C2) are arranged in a common housing (10).

4. Device according to one of the preceding claims, characterized in that a stroke volume ratio between the expander (E) and the high pressure compressor (C2) is maintained between 0.5 and 0.75.

5. Device according to one of the preceding claims, characterized in that working spaces (5.1, 5.2) of the expander (E) via a main slide (8) and an auxiliary slide (9) are controllable, the center between the working spaces (5.1, 5.2) are.

6. Apparatus according to claim 5, characterized in that the main slide (8) and / or the auxiliary slide (9) is designed as a flat slide / are.

7. Apparatus according to claim 5 or claim 6, characterized in that the auxiliary slide (9) of working piston (1, 2) by at least two pins (7) is movable.

8. Device according to one claim 7, characterized in that a piston rod (3) is releasably connected to the working piston (1, 2).

9. A method of performing a cold vapor process in which a mass flow of a fluid serving as refrigerant, which is at evaporator pressure level, is sucked by a motor-driven main compressor (Cl) and compressed to high pressure level, the mass flow of the fluid, which is at high pressure level, in a high pressure heat exchanger (H) is cooled, wherein a density is increased and a temperature of the fluid are reduced, the fluid from the high pressure heat exchanger (H) coming in an expander (E) is working expanded to evaporator pressure level, wherein the expander (E) mechanically directly with a high-pressure compressor (C2) is connected, which is supplied by the expander (E) fluid in an evaporator (V) and absorbs heat, so that the density decreases and the temperature of the coming of the expander (E) mass flow, which is on Evaporator pressure level increases, the fluid after the high-pressure heat exchanger (H) by a subcooler (U) and between the subcooler (U) and before the expander (E) a portion of the fluid from the through the subcooler (U) guided mass flow, which is located at high pressure level, branched off and relaxed by means of a high pressure control valve (TH) to medium pressure level, is subsequently performed in the subcooler (U) in countercurrent to the mass flow flowing to high pressure level, absorbs heat and thereby the mass flow, the is at high pressure level, is undercooled, and after passing through the subcooler (U) passes through the high pressure compressor (C2), wherein only the countercurrent fluid is compressed by the high pressure compressor (C2) to high pressure level and before the high pressure heat exchanger (H) of the motor-driven main compressor (Cl) coming mass flow is added.

10. The method according to claim 9, characterized in that the fluid after the expander (E) in a collector (S) is guided, in which a liquid phase of the fluid is separated from a vapor phase of the fluid and the liquid phase via an injection valve (TV) is relaxed to evaporator pressure and the vapor phase of the fluid via a pressure-holding valve (TS) and after the evaporator (V) in the from the evaporator (V) coming mass flow of the fluid is mixed.

11. The method according to claim 9 or claim 10, characterized in that carbon dioxide is used as the fluid.