JP2001255080A - Open rack vaporizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a heat transfer performance from being extremely lowered due to the heat transfer resistance of thick ice formed on the outer surface of the finned tube of an open rack vaporizer. SOLUTION: The outer surface and/or the inner surface of a heat transfer tube in a thick ice forming part in the inlet side of low temperature fluid in the tube is covered with a heat insulating material having a proper heat insulation distribution. Thus, the thick ice is prevented from being formed therein, an outer heat transfer area is effectively used, and a heat transfer performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an open rack type carburetor having a heat exchange panel formed by arranging upright heat transfer tubes in parallel, and attaching the heat transfer tubes to a fluid inlet side portion of the heat transfer tubes. The present invention relates to an open rack type vaporizer that is coated with a heat insulating material having a heat insulating performance distribution proportional to an ice thickness distribution and generates thin ice at the location to improve heat transfer performance.

[0002]

2. Description of the Related Art An open rack type vaporizer (hereinafter referred to as ORV) which is frequently used as a vaporizer for liquefied natural gas (hereinafter referred to as LNG) is, for example, a heat transfer tube (fin tube) having a pair of fins projected in a diameter direction. Arranged in the direction of the fins to form a single panel.Head tanks are provided at the upper and lower ends to form a heat exchange panel.A plurality of the panels are arranged in parallel, and LNG is introduced from the lower header tank to heat This is a structure in which heat is exchanged while the inside of the exchange panel is raised and seawater as a heat medium flows down to the heat exchange panel surface from the watering trough disposed above.

[0003] In the ORV, LNG vaporizes from a cryogenic temperature in a liquid state to a gas, and heat exchange between heat from the outside of the vaporizer and cold heat of the LNG takes place over a temperature range of 170 ° C or more until the temperature is further increased. Done. Therefore, OR using fin tubes
In order to improve the heat exchange efficiency of V itself, the basic structure as a vaporizer is how the amount of heat required from the amount of LNG introduced into the tube and how the heat exchanged heat is dissipated Need to be good.

[0004] Therefore, a so-called star fin type in which fins are enlarged in the tube is adopted to increase the efficiency of heat input and heat dissipation, and a stirring plate such as a spiral plate is inserted in the tube to make contact between the LNG and the inner wall. Methods for improving and improving the performance have been adopted. However, in the conventional ORV, the effect of improving the heat exchange efficiency by these means is also saturating, and further improvement in efficiency cannot be expected.

[0005]

That is, the conventional ORV
In the case, thick ice is generated outside the tube near the low temperature fluid inlet, and the thickness of the icing gradually decreases toward the outlet, and there is no icing after a certain height.

[0006] In the conventional ORV, fins are provided outside the tube to improve the performance of the entire length of the tube and a secondary heat transfer area is added, but thick ice is generated in about half of the low-temperature fluid inlet side. However, the heat transfer performance of the thick ice significantly deteriorates its heat transfer performance.

[0007] It is an object of the present invention to provide an ORV having a configuration capable of resolving a problem that heat transfer performance is greatly reduced due to heat transfer resistance of thick ice formed on an outer surface of a fin tube.

[0008]

SUMMARY OF THE INVENTION The present inventor has proposed that the outer surface or inner surface of a tube is mainly covered with a heat insulating material having a heat insulating performance distribution proportional to the icing thickness distribution, mainly on the inlet side of the low temperature fluid inside the tube. The present inventors have found that thin ice instead of thick ice is generated in the portion, the heat transfer area outside the tube can be effectively used, and as a result, the heat transfer performance can be improved, and the present invention has been completed.

That is, the present invention has a required heat-insulating characteristic pattern on at least one of the inner and outer surfaces of a heat transfer tube for evaporating a fluid rising or flowing down an upright heat transfer tube from a fluid inlet side toward an outlet side. This is an ORV with thermal insulation.

[0010] Further, the present invention provides an ORV having the above structure,
A structure in which the heat insulating property of the heat insulating material decreases continuously or stepwise from the fluid inlet side toward the outlet side, a structure in which the heat insulating material is arranged from the fluid inlet side of the heat transfer tube to the center, and an outer surface of the heat transfer tube. A configuration in which the provided heat insulating material has a sacrificial anode effect is proposed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The distribution of the shape of ice on a conventional fin tube will be described.
When LNG flows in from the lower side and rises inside the fin tube 1 to evaporate it, the surface temperature of the fin tube 1 on the low-temperature fluid inlet side is low. As shown in FIG. 2A, the iced 2 shape is a plate shape. In addition, when the fin tube height is 2 to 3 m, as shown in FIG. 2B, the shape of the icing 2 is cylindrical. Further, when the fin tube height is 3 to 6 m, as shown in FIG.
The shape is the same as the fin tube, or it is free of ice.

In short, conventionally, since the wall temperature of the heat transfer tube on the low temperature fluid inlet side is low, the icing shape at that portion becomes plate-like or cylindrical, and the temperature of the low-temperature fluid in the tube is increased by the heat transfer resistance of the thick ice. The rise becomes slow and the heat transfer performance deteriorates.

[0013] In the present invention, a heat insulating material having a required heat insulating characteristic pattern is arranged from the fluid inlet side to the outlet side of the fin tube. For example, the low temperature fluid inlet side of the fin tube is coated with a heat insulating material having a heat insulating performance proportional to the conventional icing thickness distribution.

[0014] By using the heat insulating material, the fin tube is cut off from the fluid inlet side to the outlet side with the heat insulating performance proportional to the conventional icing thickness distribution, and the tube wall temperature of the fin tube increases. Since the iced shape at that portion was made of thin ice almost equal to that of the non-iced portion and the heat transfer resistance of the ice could be reduced, the temperature rise of the low-temperature fluid in the tube was improved, and the heat transfer performance was improved.

[0015] That is, since the release of cold heat of LNG is restricted according to the conventional ice deposition thickness distribution, as shown in FIG. It can be used effectively and heat transfer performance can be improved.

[0016] In the present invention, any known material can be suitably used for the heat insulating material. In order to change the heat insulating property, a method of changing the coating thickness of the same material, a method of combining different heat insulating materials, and the like can be appropriately adopted.

[0017] As a heat insulating material disposed in the heat transfer tube, resin,
Inorganic materials such as ceramics and glass, metals, and mixtures thereof are preferably those that can be formed by thermal spraying or coating.

As a heat insulating material for covering the outer surface of the heat transfer tube,
It is preferable to use a material that can be formed by spraying or applying a resin, an inorganic material such as ceramics or glass, a metal, or a mixture thereof, or can be formed into a film containing bubbles. Further, it is also possible to use a metal sprayed film having a high bubble content ratio having a sacrificial anode effect.

[0019]

EXAMPLE A heat exchange panel was manufactured by adopting a configuration in which eight fins shown in FIG. 2 were protruded from a fin tube in a height direction of 6 m and the fins were lengthened in a connecting direction of the tubes. The temperature distribution of the low-temperature fluid (LNG) in the pipe and the temperature distribution of the high-temperature fluid (seawater) outside the pipe when the LNG was raised in the tube and heat exchange was performed with seawater flowing down the outer surface of the tube were measured.

FIG. 1A shows a measurement result of a conventional temperature distribution. As mentioned above, because the temperature of the heat transfer tube wall on the low temperature fluid inlet side is low,
It was confirmed that the icing shape of the portion became plate-like or cylindrical, and the heat transfer resistance of thick ice slowed the temperature rise of the low-temperature fluid in the pipe, degrading the heat transfer performance.

Next, using the same heat exchange panel as described above, FIG.
A heat insulating material made of ceramics having a heat insulating performance proportional to the iced thickness distribution corresponding to the conventional outer surface temperature of the tube wall shown in Fig. 1 was prepared and placed 2.5 m above the lower end of the fin tube.

[0022] Low-temperature fluid (LNG) in the tube when LNG is raised in each tube and heat exchange occurs with seawater flowing down the outer surface of the tube
When the temperature, the pipe wall, and the temperature distribution of the high-temperature fluid (seawater) outside the pipe were measured, the measurement results of the temperature distribution shown in FIG. 1B were obtained. As a result, the heat transfer resistance of the ice was reduced because the iced shape on the outer surface of the tube was thin ice almost equivalent to the non-iced part shown in FIG.
The temperature rise of the low-temperature fluid in the pipe was improved, and the heat transfer performance was improved.

[0023]

According to the present invention, the heat transfer performance of the heat transfer tube can be greatly improved with a simple structure in which a heat insulating material is provided inside and outside the tube at the portion where the thick ice was conventionally generated.

[Brief description of the drawings]

FIG. 1A is a graph showing a temperature distribution of a conventional low-temperature fluid in a heat transfer tube, a heat transfer tube wall, and a high-temperature fluid outside a tube, and B is a graph showing a low-temperature fluid in a heat transfer tube provided with a heat insulating material according to the present invention; It is a graph which shows the temperature distribution of a pipe wall and a high temperature fluid outside a pipe.

FIG. 2 is an explanatory view in a cross section of a heat transfer tube showing a distribution of iced shapes outside the heat transfer tube, where A is a conventional low-temperature fluid inlet side, and B is a conventional tube central position. C shows the case where the heat insulating material according to the present invention is installed.

[Explanation of symbols]

 1 Fin tube 2 Icing

Claims (4)

[Claims] Claims 1. At least one of the inner and outer surfaces of a heat transfer tube that vaporizes a fluid that rises or flows down an upright heat transfer tube,
An open rack type vaporizer in which a heat insulating material having a required heat insulating characteristic pattern is arranged from a fluid inlet side toward an outlet side. 2. The heat insulating property of the heat insulating material decreases continuously or stepwise from the fluid inlet side toward the outlet side.
2. An open rack type vaporizer according to 1. 3. The open rack type vaporizer according to claim 2, wherein the heat insulating material is arranged from a fluid inlet side of the heat transfer tube to a central portion. 4. The open rack vaporizer according to claim 1, wherein the heat insulating material provided on the outer surface of the heat transfer tube has a sacrificial anode effect.