DE102010060346A1 - Refrigeration generating method for use in cooler, involves directing fluid through capillary structure, where fluid flow is accelerated - Google Patents

Abstract

The refrigeration generating method involves directing a fluid through a capillary structure (3), where the fluid flow is accelerated. A reduction of static pressure takes place by the conversion of potential energy into kinetic energy. The static pressure at a valve is reduced below the vapor pressure of the fluid. An independent claim is also included for a cooler for use in a closed loop process, and for use with a recuperator or capillary expander equipped with downstream Joule-Thompson valve.

Description

The invention relates to a method for generating cold, which can be used in a wide temperature (a few Kelvin to room temperature) and power range (μW to MW). The operating according to the method cooler can be realized without moving parts; it is particularly suitable for cooling cryogenic fuel tanks.

From the prior art are already numerous chillers / coolers, such. Joule-Thomson, Pulse-Tube, Stirling, Evaporative and Gifford-McMahon coolers.

However, all known coolers have specific disadvantages that preclude the preferred use of cooling cryogenic fuel tanks; On the one hand, they can often only be used in limited temperature and / or performance ranges. On the other hand, many coolers on wear-prone, moving parts.

So Joule-Thomson coolers (eg. DE 32 15 396 C2 ) are used only below the inversion temperature of the fluid to be cooled. Although Stirling, Pulse-Tube, and Gifford-McMahon coolers can also produce cooling capacities below 1 W (at 80 K), they can not be scaled down in this power range. As a result, at powers well below 1 W, despite the lower cooling capacity produced, practically the same drive power is required for its operation as for 1 W cooling capacities. Stirling machines are also very susceptible to wear, as they inherently have many moving parts.

In DE 101 94 530 B4 101, a multi-stage cooling system is described that includes multiple pipe sections and expansion / suction devices. The pipe sections are filled with coolant vapor. During operation of the cooling system, liquid refrigerant forms at the upstream sides of the pipe sections (with respect to the flow direction of the refrigerant). The liquid coolant is withdrawn and injected to the downstream sides of the pipe sections.

Due to the vapor pressure of the refrigerant, the refrigerant circuit is supported and, as a result, the volumetric efficiency of the compressor is improved in the overall process.

The cooling system basically includes moving parts (compressor).

The invention has for its object to find a method that can be used in a wide temperature (a few Kelvin to room temperature) and power range (μW to MW). The method should be easy to implement coolers can be realized that do without moving parts. The coolers should also be easy to integrate into cryogenic fuel tanks

The object of the invention is solved by the features of claim 1 and 4; Further advantageous embodiments and uses of the invention will become apparent from the claims 2 and 3 and 5 to 11.

In the method according to the invention (for the generation of cold), at least one fluid is passed through at least one capillary structure. The at least one fluid is accelerated so much during the passage through the capillary structure that the static pressure is reduced by the conversion of potential into kinetic energy.

If the fluids are liquids, the static pressure is lowered to a value below the vapor pressure of the respective liquid, so that it evaporates partially or completely. The enthalpy used for the evaporation process is used for cooling.

If, on the other hand, gases or substances present in the supercritical phase are used as fluids, the cooling of the fluid takes place via a work-performing expansion in which part of the internal energy is converted into kinetic energy. The gas / supercritical material does work by accelerating its inert mass. The energy used for this purpose is absorbed in the form of heat from the environment.

A cooler, which operates according to the inventive method, has at least one capillary structure with at least one inlet and at least one outlet for the at least one fluid and at least one heat transfer unit, with which the cold generated in the capillary structure to the object to be cooled or at the medium to be cooled is dispensed.

The cooler can be easily realized by using a capillary structure as a single capillary, which is wound spirally around a typically cylindrical, filled with the medium to be cooled container. The capillary is wrapped so tightly around the container that its individual turns touch each other. The outer walls of the capillary and the container are non-positively or cohesively connected. For example, they are pressed firmly against each other or welded / soldered together; As a result, there is good thermal contact between the container and the tank. The heat transfer unit of Consequently, the cooler is formed from the outer walls of the capillary structure and the container, which are in thermal contact with each other.

The capillary structure may in principle consist of one or more individual capillaries or be formed as at least one capillary bundle.

Furthermore, in order to increase the cooling capacity of the cooler, a plurality of capillary structures can be connected in parallel and / or a plurality of capillary structures in the form of a cascade can be arranged serially to extend the working temperature range. When connected in series, the individual capillary structures can also be operated with different process media.

The cooler according to the invention is preferably used in open circular processes in which the fluid flows only once through the capillary structure. However, use in a closed loop process in which the at least one fluid is conveyed by means of a compressor from the at least one outlet to the at least one inlet of the capillary structure is also possible.

The cooler can be used particularly advantageously in connection with fuel tanks in which the fuel gases (eg natural gas, biogas or hydrogen) are stored at cryogenic temperatures in at least one thin-walled tube. The capillary structure of the cooler is either integrated into the at least one thin-walled storage tube of the fuel tank or arranged helically around the storage tube. In addition, the capillary structure of the radiator can be designed so that it simultaneously assumes the function of the at least one storage tube.

For decoupling from the drive temperature level, the cooler can be used in combination with a recuperator. A performance increase of the cooler is possible by means of a coupling to a capillary expander with a downstream Joule-Thompson valve.

The cooler according to the invention has the advantage that it basically works without moving parts, since the cooling takes place exclusively using the Bernoulli effect by means of the fluidically effective capillary structure. The cooler is so compared to coolers with many moving parts, such. B. Stirling cooler, more reliable and durable.

Compared to the Joule-Thomson coolers, which can also be constructed without moving parts, since the cooling and / or evaporation of the fluid by the Bernoulli effect of the Joule-Thomson effect contributes only slightly to the cooling, the cooler according to the invention Advantage that it can also be operated with liquids that have a temperature above their inversion temperature. In addition, it can also be operated with substances present in the supercritical phase and with gases, which is inherently impossible with Joule-Thomson coolers.

The cooler can be used in a wide temperature range and can produce cooling capacities from a few μW to several MW. Since in particular the coolers operated in the open cycle process are extremely low in vibration, cooling of vibration-sensitive devices, such. As HTS sensors, microwave filters and infrared sensors, possible. It is also suitable for operating the low-vibration cryogenic vacuum pumps commonly used in the semiconductor industry.

A further advantage of the cooler according to the invention is that the longitudinal cooling capacity and temperature profile can be influenced by the course of the capillary geometry (length, diameter), as well as cooling at a constant temperature level and also cooling with a temperature profile (continuous distribution of temperature levels). is possible.

If fluids are used as fluids, then the local static vapor pressure in the evaporator can be lowered below its outlet pressure. This makes it possible to reduce the evaporation temperature up to the triple point (single working substance) or up to the eutectic point (working substance mixture).

The invention will be described below with reference to FIG 1 to 3 explains; show:

1 a storage container provided with the radiator;

2 a fuel tank constructed of storage tubes, in a schematic representation;

3 : different embodiments of the capillary structure.

1 shows a cylindrical storage container 1 whose curved outer wall 2 with a capillary 3 is wrapped spirally. The capillary is 3 wrapped so tightly around the container that their individual turns touch each other. For cooling, the capillary 3 about her 4 and outlet 5 flows through with a fluid. The resulting cold is over the part of the outer wall 6 the capillary, which is in good thermal contact with the outer wall 2 of the container 1 stands on the medium to be cooled 7 in the container 1 transfer.

The fuel tank 8th ( 2 ) consists of numerous, parallel storage tubes 9 , each one side of the tubes 9 at a collection facility 10 connected, all the pipes 9 with the fuel outlet line 11 combines. For thermal insulation is the tank 8th with a multilayer vacuum super insulation 12 and radiation screens 13 surround; the entire assembly is in a dewar 14 , When the fuel is removed, it passes through the capillary structure 3 , The resulting cold is used to cool the fuel tank 1 used.

In 2 are different embodiments of the capillary structure 3 as well as their connection to the storage pipes 9 shown.

In the first variant are the capillaries 3 coaxial inside the storage pipes 9 arranged in the second variant surrounded the capillaries 3 the storage pipes 9 helically.

In the third variant, the cross sections of the storage tubes 9 with an inner diameter of about 1 mm chosen so small that at the same time they also have the function of capillaries 3 take. The heat transfer does not take place here, as in the previous variants, over the wall of the respective capillary 3 but within the fuel used.

LIST OF REFERENCE NUMBERS

1

container

2

Outer wall of the container

3

Capillary / capillary

4

Inlet for the fluid

5

Outlet for the fluid

6

Outer wall of the capillary

7

to be cooled medium

8th

fuel tank

9

storage tube

10

collecting device

11

outlet pipe

12

Multi-layer vacuum superinsulation

13

radiation shield

14

Dewar

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3215396 C2 [0004]
• DE 10194530 B4 [0005]

Claims (11)

Method for producing cold, in which at least one fluid is passed through at least one capillary structure ( 3 ), and the at least one fluid flowing through the capillary structure ( 3 ) is accelerated so that the conversion of potential kinetic energy into a lowering of the static pressure takes place. A method according to claim 1, characterized in that as the at least one fluid used at least one liquid, the static pressure is lowered to a value below the vapor pressure of the at least one liquid, the liquid partially or completely evaporated and the spent enthalpy of evaporation is used for cooling. A method according to claim 1, characterized in that as the at least one fluid, at least one gas or a substance present in its supercritical phase is used and the fluid is subjected to a working expansion, in which part of the internal energy is converted into kinetic energy. A cooler, working according to the method according to one of claims 1 to 3, having at least one capillary structure ( 3 ) containing at least one input ( 4 ) and at least one outlet ( 5 ) for the at least one fluid, and at least one heat transfer unit ( 2 . 6 ) used for transfer in the capillary structure ( 3 ) generated cold on the object to be cooled or on the medium to be cooled ( 7 ) serves. Cooler according to claim 4, characterized in that the capillary structure ( 3 ) consists of a single capillary which has a cylindrical container (with a medium to be cooled). 1 ), the heat transfer unit being made of the outer walls ( 2 . 6 ) of the capillary structure ( 3 ) and the tank ( 1 ) is formed. Cooler according to one of claims 4 to 5, characterized in that it comprises at least two parallel-connected capillary structures ( 3 ) having. Cooler according to one of claims 4 to 6, characterized in that it comprises at least two series-connected capillary structures ( 3 ), wherein in the capillary structures ( 3 ) each different process media are used. Use of the cooler according to one of claims 4 to 7 in an open cycle for cooling one of at least one thin-walled storage tube ( 9 ) constructed cryogenic fuel tanks ( 8th ), whereby the capillary structure ( 3 ) either into the at least one thin-walled storage ear ( 9 ) of the fuel tank ( 8th ), the capillary structure ( 3 ) the storage tube ( 9 ) helically surrounds or the diameter of the at least one storage tube ( 9 ) is chosen to be so small that, in addition to the memory function, the function of the capillary structure ( 3 ) Fulfills. Use of the cooler according to one of claims 4 to 7 in a closed loop process, in which the at least one fluid is conveyed by means of a compressor from at least one outlet to at least one inlet of the capillary structure ( 3 ). Use of the cooler according to one of claims 4 to 7 in combination with a recuperator for decoupling from the drive temperature level. Use of the cooler according to one of claims 4 to 7 coupled to a capillary expander with downstream Joule-Thompson valve.

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