Refrigeration – Storage of solidified or liquified gas – Liquified gas transferred as liquid
Reexamination Certificate
2000-06-09
2001-07-24
Capossela, Ronald (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Liquified gas transferred as liquid
C165S009100
Reexamination Certificate
active
06263678
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and an evaporator device for evaporating a low temperature liquid medium such as hydrogen, using an evaporator operating as a heat exchanger between a hot medium that gives off its heat and the liquid medium that is to be evaporated.
BACKGROUND INFORMATION
Evaporators of the above mentioned general type are typically embodied as plate-type or tubular heat exchangers. Such heat exchangers are typically used in applications in which a medium is stored in liquid form at a low or super-cold temperature in a storage tank, but is to be provided for use in a gaseous physical phase. An example of such an application is the use of cryogenic liquids, such as liquid hydrogen or liquid natural gas, as a fuel or energy carrying medium for aircraft propulsion engines, and especially turbine engines.
A particular feature relating to such evaporator devices is that the liquid medium to be evaporated is delivered to the evaporator with a very low inlet temperature of only about 20 K (−253° C.). On the other hand, a relatively hot medium, such as the surrounding atmospheric air, or the exhaust gas of an engine for example, or some other heated medium, is provided to the evaporator as a heat source for evaporating and in some cases superheating the cryogenic liquid medium. Thus, the hot medium comes into contact with extremely cold surfaces of the evaporator, which are cooled by the cryogenic medium that is to be evaporated. As a result there is a danger that the hot medium will be cooled to below its respective dew point temperature or freezing point temperature so that it at least partially condenses or forms ice on the surfaces of the evaporator. Such condensation or ice build-up obstructs the flow passages for the hot medium, interferes with the operation of the evaporator, and can present a serious danger, especially if the evaporator is part of a fuel preparation system for an aircraft engine.
Typically, this danger of freezing or condensing of the hot medium is avoided or counter-acted by reducing the heat transfer between the hot medium and the cryogenic medium that is to be evaporated. In this manner, higher surface temperatures can be achieved at the heat inlet side of the evaporator. However, this in turn necessitates a larger and heavier structure of such an evaporator in order to achieve the same total or overall heat transfer and evaporation of the cryogenic medium, which is especially undesirable in the application of such evaporators in aircraft and spacecraft.
OBJECTS OF THE INVENTION
In view of the above it is the aim of the invention achieve the following objects singly or in combination:
to provide a method and an evaporator device for evaporating a low temperature liquid medium in such a manner so as to reliably avoid the condensation or ice formation of the hot medium such as air or exhaust gases that are provided to the evaporator;
to provide such an evaporator device with a particularly compact and lightweight structure while still achieving an efficient heat transfer and avoiding the formation of condensate or ice; and
to provide a construction of an evaporator device that can conveniently be incorporated or integrated into a hot gas duct or even a combustion chamber of an engine such as a turbine engine.
SUMMARY OF THE INVENTION
The above objects have been achieved in a method of evaporating a liquid medium such as hydrogen in an evaporator operating as a heat exchanger, according to the invention, wherein the hydrogen first flows through a first portion of a flow channel where it is evaporated and superheated to a certain extent, and then flows back through a second portion of the flow channel where it is further heated. The hydrogen in the second channel portion also acts as an intermediary or buffer for heat transfer from the hot medium through the hydrogen in the second channel portion and to the hydrogen in the first channel portion. The net direction of flow of the hydrogen in the second channel portion is substantially opposite the direction of flow of the hydrogen in the first channel portion.
The above objects are further achieved in the evaporator device according to the invention, having a flow channel for the medium to be evaporated and a passage for the heat-providing medium. The channel is arranged outwardly around the passage and comprises an initial or first portion and a second portion with a return flow in the opposite direction from that of the first portion. To achieve this, the second channel portion is connected in series flow communication with a downstream end of the first channel portion. More particularly, the first portion and the second portion of the flow channel for the medium to be evaporated are substantially cylindrical channels arranged concentrically outside of and around the passage through which the heat-providing medium flows.
Preferably, at least a part of the second return-flow portion of the first channel is arranged radially inwardly from the first initial portion of the channel, so that the second return flow portion is between the first portion of the channel and the hot medium passage. The hot medium passage and the second channel portion thereby share a common boundary wall therebetween, i.e. the hot medium is on one side of this common boundary wall while the colder medium is on the other side of this common boundary wall. Similarly, the first and second channel portions share an internal boundary wall therebetween, while the first channel portion is further bounded by an outer boundary wall opposite the internal boundary wall, whereby this outer boundary wall may form the outer wall of the overall apparatus. The hot medium does not flow anywhere directly along the outer boundary wall. In this manner, the surfaces of the evaporator adjacent or bounding the hot medium passage are not directly exposed to the extreme low temperature liquid medium entering the evaporator at the inlet thereof, but instead are only exposed to the medium in the return flow channel portion where the medium has already been evaporated and partially superheated.
According to further details of the invention, the first forward flow portion and the second return flow portion of the channel for the medium to be evaporated can have a spiral or helical flow channel shape, wherein the spiral rotation direction can be the same or different in the two flow channel portions. In a further embodiment, at least either the forward flowing channel portion or the return flowing channel portion can comprise a helical or spiral coiled tube arranged within a cylindrical space. In such an embodiment, the net flow direction of the medium refers to a substantially axial direction to the right or to the left, while the incremental or local flow direction at any point in the helical flow channels includes a substantial circular or circumferential component.
REFERENCES:
patent: 231013 (1880-08-01), Crutchett
patent: 2621477 (1952-12-01), Powter et al.
patent: 2730337 (1956-01-01), Roswell
patent: 3151673 (1964-10-01), Strache
patent: 3181590 (1965-05-01), Dupler
patent: 3189018 (1965-06-01), Sass et al.
patent: 3237400 (1966-03-01), Kuhrt
patent: 3504994 (1970-04-01), Desty et al.
patent: 3617224 (1971-11-01), Brun-Tsekhovoi
patent: 3712070 (1973-01-01), Arenson
patent: 3859040 (1975-01-01), Shefsiek et al.
patent: 3870459 (1975-03-01), Desty et al.
patent: 3907028 (1975-09-01), Lawson
patent: 4047490 (1977-09-01), Galluzzo
patent: 4100733 (1978-07-01), Striebel et al.
patent: 4113009 (1978-09-01), Meyer et al.
patent: 4213501 (1980-07-01), Pfeiffer
patent: 4331129 (1982-05-01), Hong et al.
patent: 5215144 (1993-06-01), May et al.
patent: 1104211 (1955-11-01), None
patent: 1246126 (1971-09-01), None
patent: 63-259387 (1988-10-01), None
patent: 7802258 (1979-09-01), None
John B. Heywood et al. Parameters Controlling Nitric Oxide Emissions From Gas Turbine Combustors, Agard-CP-125, Neuilly sur Seine, France, Apr. 1973, pp. 21-1 to 21-16.
Ziemann et al. Low-NoxCombustors for Hydrogen Fueled Aero Engine, World Hy
Capossela Ronald
DaimlerChrysler Aerospace Airbus GmbH
Fasse W. F.
Fasse W. G.
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