Heat exchange – With first fluid holder or collector open to second fluid
Patent
1990-04-27
1993-06-29
Flanigan, Allen J.
Heat exchange
With first fluid holder or collector open to second fluid
165111, 165166, F25J 304
Patent
active
052225496
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a condenser-evaporator which executes heat exchange with a liquid in a first fluid chamber and a fluid in a second fluid chamber to vaporize the liquid in the first fluid chamber.
2. Description of the Related Art
a. Conventional Condenser/Evaporator
Many condenser-evaporators for use in double column rectifier of a cryogenic air separation plant, as disclosed in the Published Unexamined Japanese Patent Application No. 56-56592, are so-called plate fin type heat exchangers each employing many parallel partitions vertically separating the condenser-evaporator into two types of chambers, namely oxygen chambers each as the first fluid chamber and nitrogen chambers each as the second fluid chamber, which are alternately provided adjoining one another.
In each oxygen chamber of such a plate fin type condenser-evaporator, many vertical evaporation passages are formed by vertically providing heat exchanger plates, each evaporation passage having top and bottom ends open, with the bottom opening serving as an inlet to introduce, liquid oxygen and the top opening serving as an outlet to flow out a mixture of an oxygen gas and liquid oxygen. As the overall condenser-evaporator is immersed in liquid oxygen retained in the sump bottom space of the low pressure (LP) column of a double column rectifier, each oxygen chamber is filled with liquid oxygen and the liquid oxygen in this oxygen chamber is subjected to heat exchange with nitrogen gas in the adjoining nitrogen chamber, and the part of the liquid oxygen is vaporized into oxygen gas bubbles and rises in the evaporation passage. The liquid oxygen circulates from the inside to outside of a condenser-evaporator because of developed head pressure due to the density difference between the mixture of the vaporized gas and liquid in the oxygen chamber and the liquid around the condenser-evaporator in the sump.
The nitrogens chamber is enclosed chamber in which vertical heat exchanger plates are provided as in the oxygen chamber to form many vertical condensing passages, and it is connected to the high pressure (HP) column of the double column rectifier via headers provided at the upstream and downstream ends of the connecting passages. The nitrogen gas drawn out from the upper portion of the HP column is introduced to the condensing passages through the upper header to be subjected to heat exchange with the liquid oxygen in the adjoining evaporation passage, and the condensed liquid nitrogen is led out from the condenser evaporator through the lower header.
b. Disadvantages of A conventional Condenser-Evaporator
As mentioned above conventional condenser-evaporator is immersed in the sump of liquid oxygen at the bottom space of the LP column, and is well known as a material property that the higher the liquid pressure becomes, the higher the boiling point of the same liquid rises. The head pressure of liquid oxygen in oxygen passage is higher at a lower position than at a higher position of an oxygen passage depending on the depth of liquid oxygen. Therefore, the boiling point of liquid oxygen in the passage is higher at the lower position than at the higher position of the oxygen passage. This phenomenon is generally called the "rise of the boiling point". In liquid oxygen the rise of the boiling point is about 1.degree. C. per one meter of liquid depth. The condenser-evaporator is heat exchanged by the difference between the boiling temperature of oxygen and the condensation temperature of nitrogen according to the following equation of heat transfer. -177.5C. at 4.8 kgf/cm.sup.2 G) is higher than the boiling point of oxygen in the LP column (one example: -179.5C. at 0.6 kgf/cm.sup.2 G). Therefore the temperature difference between both passages decreases with the rise of the boiling point of liquid oxygen which corresponds to the liquid oxygen head pressure. This means that the head pressure of liquid oxygen reduces the heat amount to be exchanged with the condenser-evaporator.
In o
REFERENCES:
patent: 4153501 (1979-05-01), Fink et al.
patent: 4372764 (1983-02-01), Theobald
patent: 4715433 (1987-12-01), Schwarz et al.
Fujita Ikuo
Ishii Hiroshi
Kaneko Teruji
Kura Tomio
Matsuoka Takashi
Flanigan Allen J.
Japan Oxygen Co., Ltd.
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