WO1996024808A1

WO1996024808A1 - Cooling system

Info

Publication number: WO1996024808A1
Application number: PCT/DE1996/000194
Authority: WO
Inventors: Jürgen KELLER
Original assignee: Keller Juergen
Priority date: 1995-02-07
Filing date: 1996-02-07
Publication date: 1996-08-15
Also published as: DE19680069D2; DE19605241A1

Abstract

The system comprises a heat exchanger (WT), a pressure-relief valve (D), a separator (S) and a cooling vortex tube (KWR), i.e. a Ranque and Hilsch vortex tube supplemented by a separate hot flow cooler (WK) and a hot flow return line (WR) with a regulating valve (RV2). These components are arranged relative to one another such that a flow of compressed fluid, i.e. liquid, mixed liquid-vaporized or vaporized, working medium which arrives at ambient temperature is expanded exothermically, i.e. releasing heat into its environment, forming a liquid-vapour mixture or a vapour. The working medium can be a pure substance or a mixture of substances.

Description

Cooling system

Description

Technical field

The invention relates to a cooling system in which a flow of working fluid is subjected to an exothermic expansion process.

State of the art

In general, refrigeration machines and heat pumps are known which work with compression, absorption or adsorption technology. In these refrigeration machines or heat pumps, expansion elements such as throttles or expansion valves are used. This is necessary in order to lower the temperature of a working substance which is generally present as a liquid (also referred to as working medium) below a certain level, which is generally predetermined by the environment.

Details of the known processes are explained in detail in the following basic literature:

R. Plank, Handbook of Refrigeration Technology,

Springer, Berlin, 1936 ff.

H.L. von Cube, ed., Textbook of refrigeration technology,

2 vols, C.F. Müller, Karlsruhe, 1981.

Bäckström, Emblik, refrigeration technology,

Verlag G. Braun, Karlsruhe, 3rd edition, 1974.

H.L. by Cube, F. Steimle, heat pumps

VDI publishing house, Düsseldorf, 1978.

W. Niebergall, Sorption Chillers, Handbook of Refrigeration Technology, R. Plank (Ed.), Vol. 7

Springer, Berlin, 1959. G. Alefeld, R. Radermacher, Heat Conversion Systems, CRC Press, Boca Raton etc., 1994.

Reference is expressly made to this state of the art with regard to all terms that are not explained in more detail here.

The relaxation process of the working fluid in the throttle is adiabatic, isenthalpic and with loss of energy or with the production of entropy. The working fluid vaporizes partially, ie after the relaxation in the cooled state it is no longer completely available, but is only partially available as a liquid for generating cold or for absorbing heat.

This circumstance is one of the main causes for the fact that the performance figures of the refrigeration machine or heat pump processes are fundamentally much smaller than their theoretically maximum possible values described by the car emergency barriers. To reduce the proportion of steam generated during throttling, it is advantageous to pre-cool the working fluid. In general, however, this is only very limited, or only possible up to the ambient temperature without additional effort.

Presentation of the invention

The invention is based on the object of increasing the performance figures of refrigeration machines and heat pumps by further developing the expansion process of the fluid working medium in the throttle in such a way that the proportion of liquid increases after expansion, the proportion of vapor decreases, ie the enthalpy ¬ pie of the working fluid compared to their value in the entry state before the throttle reduced and thus the exergy losses during relaxation are reduced.

An inventive solution to this problem is specified in claim 1. Advantageous further developments are the subject of claims 2 to 10. Claims 11 and 12 relate to advantageous uses of the system designed according to the invention.

According to the invention, a thermal separation effect is used in a further developed vortex tube according to Ranque and Hilsch: a compressed, fluid, i.e. in particular a liquid, a liquid-vaporous or a vaporous working medium stream with ambient temperature using the thermal separation effect according to Ranque and Hilsch exothermic, i.e. releasing heat to the environment, relaxed and cooled.

According to the invention, a vortex tube according to Ranque and Hilsch is supplemented by a separate hot-flow cooler and a hot-current return with regulating valve and provided with further process engineering elements, namely heat exchanger, expansion valve, separator and regulating valve, in such a way that a generally liquid one is used in the plant according to the invention , a stream of working fluid containing one or more substances, which is compressed and is present at ambient temperature, can be relaxed exothermally, that is to say by releasing heat to the environment, so that the proportion of liquid in the resulting wet steam is greater than in the case of direct expansion in an adiabatic one Throttle. In heat pump systems, the heat given off can at least partially be used as useful heat. In refrigeration systems, the cooling capacity of the process is increased by reducing the steam content of the expanded working fluid.

The thermal separation effect during the expansion of compressed gases and vapors in Ranque and Hilsch vortex tubes has been known for many years. With this effect, a steam or gas stream under pressure drop is divided into a warm gas stream and a cold gas stream, the temperatures of which are respectively above and below the temperature of the input stream. The following basic literature is pointed out:

G.J. Ranclue, "Experiences sur la detende girtoire avec production simultanes d'un echappe- ment d'air chaud et dlun echappement d'air froid", Journal de physique et le radium, 4 (1933), No.7;

R. Hilsch, "The expansion of gases in the centrifugal field as a cooling process", Z.f, Naturfor¬ research, 1 (1946), 208-214.

An interesting technical application for cooling or drying moist gases such as moist air is in

R.v. Linde, device for cooling a compressed gas stream, DE-PS 926 729

described.

In principle, this effect also occurs in liquids, but is usually so small that it has practically no meaning. If you want the effect of cooling a liquid flow or a liquid use containing fluid flow, pure working steam must first be generated. This can be done by partially expanding and evaporating the fluid stream to be expanded, which is assumed to have ambient temperature at first.

The invention makes it possible to relax any fluid and compressed working materials in energy and process engineering exothermally, that is to say by releasing heat. This makes it possible, for example, to obtain additional heat in heat pump processes or to increase the cooling capacity of the working fluid by the heat given off in cooling processes. Both effects lead to increases in the energetic performance figures of the processes, which are typically 5%, in special cases, such as cyclic processes with carbon dioxide (C0 ₂ ) as a working medium, but can also be 10% - 15% (see JU Keller, AI Climate, Cold, Heating, 21 (1993), 300-304.)

Brief description of the drawing

The invention is described below by way of example without limitation of the general inventive concept by means of exemplary embodiments with reference to the drawing, to which reference is expressly made with regard to the disclosure of all details according to the invention not explained in detail in the text. Show it:

1 is a flow diagram of a thermal choke system,

2 shows a flow diagram of the thermal choke system according to FIG. 1 with process data,

3 shows a cold diagram of the thermal throttling process (P, h).

4 shows an enthalpy current / temperature diagram of the thermal choke process (H = hm, T).

5 shows a cold diagram of the thermal throttling process with R22 as the working medium,

6 shows a longitudinal section through a cooling vortex tube,

Fig. 7 is a flow diagram of a thermal reactor with additional evaporation, and

8 and 9 the circuit of an executed test system,

Representation of exemplary embodiments

1 shows a flow diagram of a thermal throttle system constructed in accordance with the invention. The reference symbols used have the following meaning:

WT heat exchanger

D expansion valve or throttle

S phase separator

RV1, RV2, RV3 regulating valves

KWR cooling vortex tube

WK hot current cooler

WR hot flow return working fluid flow (kg / s)

ΠI _D steam flow (kg / s)

Π. _L mass flow of boiling liquids (kg, s) m (L, V) wet steam flow (kg / s) heat output (watts)

H enthalpy current With regard to the connection of the individual elements, reference is expressly made to the illustration in FIG. 1.

The working fluid flow m is conducted into the throttle D via the heat exchanger WT. The steam generated during expansion in the throttle D is always colder than the supplied fluid, i.e. the original liquid. If the steam were released directly in a vortex tube, the temperature of the hot gas flow would only be slightly above the temperature of the original liquid flow, i.e. e.g. Ambient temperature! Therefore, the working steam in the vortex tube could give off practically no heat to the environment.

According to the invention, therefore, the vapor stream ΠI _D separated from the residual liquid in the separator S is reheated as much as possible in a suitably designed heat exchanger WT by the heat of the incoming liquid stream m, ie to a few degrees below ambient temperature! If the preheated steam stream is expanded in the cooling vortex tube KWR, the temperature of the hot gas stream in forming near the wall of the vortex tube is. Experience has shown that _{H is} clear, ie around 30-40 ° C above the ambient temperature. The hot gas stream can thus be cooled in a separate cooler WK, which is usually designed as a coil. The heat is emitted via cooling fins of the hot-flow cooler WK to a cooling medium, for example water, or to the ambient air. After cooling, the hot gas flow Π. _{H combined} with the cold flow m _{c also} generated in the vortex tube by the warm current return with regulating valve RV2, in order to work with the liquid expanded in a further regulating valve RV3. current in. to be combined to form the wet steam flow m (L, V).

FIG. 2 shows the system shown in FIG. 1, process data being entered at positions 3 to 9 as an example.

The data given relate from top to bottom - as can also be seen from the box in FIG. 2 - in each case on the temperature, the pressure, the mass flow, the specific enthalpy and the vapor content of the working medium in the individual states.

The working fluid has a steam content of approx. 28% (mass fraction) when it leaves the system.

In the case of isenthalpic relaxation in a throttle of a conventional type, the steam content would be approximately 31-32%, as can be seen in FIG. 5. This figure shows the cold diagram of an implemented thermal throttling process with the refrigerant R22. The state numbers relate to the states or digits indicated in FIGS. 2-4.

The enthalpy flow H of the fluid is reduced in the system from H = 1500 W by giving off the heat output Q = 60 W to H - Q = 1440 W.

Process data are given for the following places:

3 "state of entry of the working fluid,

4 outlet state of the fluid after cooling in the heat exchanger WT, 5 outlet state of the working fluid after throttle D,

5 'state of the boiling liquid in separator D,

5 "state of saturated steam in the separator,

6 "state of the working steam after heating or overheating in the heat exchanger WT,

7 state of the working steam after expansion and cooling in the cooling vortex tube,

8 state of relaxation of the boiling liquid after throttling to the final pressure,

9 Condition of the wet steam after combining the cooled working steam (7) and the relaxed working liquid (8).

The values given are based on the following process conditions:

Working substance: R22,

Mass flow (L): 12 g / s,

Heat output: 60 W.

Also explicitly referred to the values that can be gathered from FIG. 2 as a disclosure of the invention.

7 shows an advantageous development of the thermal reactor. The flow diagram of a thermal throttling system with additional cooling of the hot current emerging from the hot-flow cooler WK is shown in the separator / steamer (S, V) of the system. The original circuit according to FIG. 1 is also entered in broken lines.

The difference from the flow diagram shown in FIG. 1 is that the hot gas flow Π. _H after leaving the hot-flow cooler WK is not directly combined with the cold flow m _c . Rather, the union takes place only after the hot gas flow has passed a heat exchanger built into the separator S. There, the hot current ΠI _H gives off heat to the partially relaxed and pre-cooled liquid working fluid which, since it is in a vapor-liquid equilibrium state, does not heat up but also evaporates. This increases the steam flow mo compared to that of the circuit shown in FIG. 1. This also increases the warm gas flow IU _H and the heat Q ~ ΠI _H given off in the heat exchanger WK!

This circuit, in which the separator S acts as an evaporator (V) at the same time, is particularly suitable for fluids and expansion processes that occur close to their critical state, i.e. with low values of the enthalpy of vaporization, such as with carbon dioxide (C0 ₂ ), since the increase in steam flow o due to the additional evaporation in the separator / evaporator can be particularly large.

3 and 4 is the exothermic relaxation process taking place in the thermal reactor according to FIG. 1 of a working medium assumed to be liquid in the refrigeration program according to Cv Linde (p, h or ln (p / p ₀ ), h) and in the enthalpy flow -Temperature diagram according to Linhoff (T, H = hm) shown. The status numbers refer to the digits shown in Figure 2. The boiling and dew lines of the working fluid are highlighted in bold in FIG. 3. The dashed lines indicate the heat exchanger WT of the system. 4 qualitatively shows the thermal separation which initially takes place in the cooling vortex tube, described by the hot steam state H and the cold steam state C (cf. also FIG. 6), and the heat output Q released to the environment by cooling the hot steam in the warm steam cooler WK registered.

Fig. 6 shows a longitudinal section through a cooling vortex tube (KWR), (see also published application DE 43 45 137 AI from 06/29/1995).

The cooling vortex tube is a vortex tube according to Ranque and Hilsch (RHWR), which is provided with a hot-flow cooler (WK) provided with cooling fins (10), a warm-current return line (WR) and a regulating valve RV2. The vaporous working material enters through an inlet channel (11) tangentially to the circular cross section of the vortex tube and is formed into a warm flow (12), state (H) and a cold flow (13), state (C), forming a swirl flow. , separated. The hot current (12) is cooled in the hot-current cooler (WK) and gives off the heat output Q to a cooling medium or to the environment. Thereafter, the cooled hot flow is recombined with the cold flow 13 via a warm flow return WR and a regulating valve RV2 and emerges from the cooling vortex tube as cooled steam or wet steam.

8 shows the flowchart of a process performed at the Institute for Fluid and Thermodynamics at the University of Siegen. planned, designed and built thermal throttle system. As an experimental system, it is provided with numerous measuring devices and can be operated with the refrigerant R22, for example, in a refrigeration system. 8 shows the entire system with the feed and discharge lines of the working fluid located in the center on the right in the figure. The usual symbols for the individual components are used so that a complete description is dispensed with and reference is instead made to the illustration in FIG. 8.

FIG. 9 shows a section of the system shown in FIG. 8, namely the connection of the cooling vortex tube KWR, the warm current cooler WK and the regulating valve RV2.

The invention has been described above with reference to exemplary embodiments without restricting the general concept of the invention. Within this general concept of the invention, based on the above description, thermal chokes, i.e. Cooling systems without moving parts for exothermic, i.e. heat-releasing relaxation of compressed fluid working materials in energy and process engineering can be realized.

The system generally consists of a heat exchanger, an expansion valve, a separator and a cooling vortex tube, ie a vortex tube supplemented by a separate hot-flow cooler and a hot-current return with regulating valve, in particular according to Ranque and Hilsch. These elements are interconnected so that a Incoming stream of a compressed fluid, ie liquid, liquid-vapor mixed or vaporous working medium exothermic, ie with heat released to its environment, with the formation of a liquid-vapor mixture or a vapor is expanded. The working medium can be a pure substance or a mixture of substances.

The Ther o-throttle can basically be used in all processes of energy and process engineering instead of conventional, adiabatically operating throttle or relief valves. In heat pump and refrigeration cycle processes, it leads to energy savings, i.e. to not inconsiderable increases in performance figures.

Claims

Patent claims

1. Cooling system in which a flow of working fluid (m) is subjected to an exothermic relaxation process, that is to say, with a heat output (Q) being transferred into a wet steam stream (m (L, V)), with a heat exchanger (WT) into which a working fluid flow (m), usually containing liquid, containing one or more substances, a throttle (D) into which the working fluid flow exiting the heat exchanger enters, a separator (S) connected downstream of the throttle, which separates the working fluid flow into a steam flow (ΠI _D ) and a stream (IΓIL) of boiling liquid separated, a vortex tube (KWR) in particular according to Ranque and Hilsch, into which the steam flow enters after passing through the heat exchanger (WT), and which the steam flow into a warm flow (12) and one Cold flow (13) divides, a hot flow cooler (WK), and a hot flow return (WR) with regulating valve (RV2), which combines the cooled warm flow with the cold flow, so that in the resulting wet steam f the liquid fraction is greater than when relaxing directly in an adiabatic throttle.

2. Cooling system according to claim 1, characterized in that the inflowing fluid, one or more substances containing Arbeitsmittel¬ stream (working fluid stream) is in a compressed liquid state or a boiling state, a wet steam state, a saturated steam state or a superheated steam state.

3. Cooling system according to claim 1 or 2, characterized in that the working fluid stream is first cooled isobarically in the heat exchanger (WT) and is partially relaxed in the throttle D, so that it is converted into a liquid-steam mixture.

4. Cooling system according to claim 3, characterized in that the liquid-steam mixture is separated under the influence of gravity in the Sepa¬ rator S in the steam flow mo and the flow of boiling liquid AL.

5. Cooling system according to one of claims 1 to 4, characterized in that the initially cold steam flow (mo) after passing through the heat exchanger (WT) and the resulting heating occurs through a regulating valve RVl in the cooling vortex tube (KWR) , in which it is further expanded to form a swirl flow and cooled in the hot-flow cooler WK by the heat given off by the hot gas stream formed in the vortex tube, and

«That the flow of boiling liquid Π.L is expanded via a regulating valve RV3 and, after combining with the cooled steam flow mo, leaves the system as a wet steam flow m (L, V).

6. Cooling system according to one of claims 1 to 5, characterized in that the ratio of the pressure drop occurring in the throttle D po to the pressure drop p occurring in the cooling vortex tube or in the regulating valve (RV3) is between 1 and 30.

7. Cooling system according to one of claims 1 to 6, characterized in that the mass ratio of the steam flow mo to the liquid flow ΠIL is between 5% and 50%.

8. Cooling system according to one of claims 1 to 7, characterized in that the entry speed of the steam flow into the cooling vortex tube (KWR) is at least 50% and at most 100% of the speed of sound in the entry state.

9. Cooling system according to one of claims 1 to 8, characterized in that the speed of the swirl flow of the steam stream expanding on the walls of the cooling vortex tube (KWR) in the direction of the vertical tube axis at least 10% and at most 60% of the speed of sound of the steam in the entry state.

10. Cooling system according to one of claims 1 to 9, characterized in that the hot gas stream m ^H emerging from the hot-flow cooler (WK) is additionally passed through a heat exchanger built into the separator (S) and only then with the out the cold flow m _c emerging from the cooling vortex tube is combined via the regulating valve (RV2) and is then fed to the liquid flow ΠIL which is relaxed by the valve (RV3) (FIG. 7).

11. Use of a cooling system or a cascade circuit of such systems in parallel or serial manner according to one of claims 1 to 10 in heat pumps and refrigeration machines with compression technology, absorption technology, adsorption technology or a combination of these techniques in one-stage or multi-stage construction for mono- or multivalent operation by replacing the adiabatic expansion valve or the adiabatic expansion nozzle by the cooling system (1).

12. Use of a cooling system or a Kaskaden¬ circuit of such systems in a parallel or serial manner according to one of claims 1 to 10 in systems of energy and process engineering for exothermic Ent¬ relaxation or cooling of industrial brines and similar working fluids as a replacement for one or more adiabatic Relief valves.