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Heat pipe

a technology of heat pipe and pipe body, which is applied in the field of heat pipe, can solve the problems of heat conductivity inferior to water, pipe burst, and heat pipe breakage, and achieve the effect of preventing the damage of the pipe body due to the freezing of the working fluid in cold climates

Inactive Publication Date: 2006-03-23
THE FUJIKURA CABLE WORKS LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] A main object of the present invention is to provide a heat pipe in which the frost damage of the pipe body due to freezing of the working fluid in cold climates is prevented.
[0011] Still another object of the present invention is to provide a heat pipe excellent in heat conductivity.

Problems solved by technology

However, in a cold condition, water freezes into ice and its volume expands to cause breakage of the heat pipe.
In case the heat pipe comprising water as the working fluid is used in cold climates, for example, the internal working fluid freezes and expands, and the expanding pressure may burst the pipe.
The bursting of the pipe can be avoided if Hydrochlorofluorocarbon such as alcohol, hydroflorocarbon or hydrofluoroether is used in place of water; however, heat conductivity of the alternatives to chlorofluorocarbon is inferior to that of water.
However, if a large amount of ethylene glycol and / or propylene glycol is mixed into water, the boiling point rises and the viscosity of the working fluid increases to degrade its heat conductivity.
As a result of this, the performance of the heat pipe is deteriorated.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

Test for Heat Conductivity

[0026] A device as illustrated in FIG. 1 was used for the tests of heat conductivity. A pipe having a diameter of 16 mm and a length of 1100 mm is provided with double-pipe condensers over 500 mm of an upper portion, and 500 mm of a lower portion is heated by a heater. As the working fluid, an aqueous solution containing 1% weight concentration of ethylene glycol was used and 51 cm3 (i.e., 40% of capacity of the heating portion) thereof was encapsulated in the pipe. The air was adequately removed from the system. FIG. 2 shows a table of overall heat transfer coefficients kw / (m2K) when a heat gauge, which is arranged on a pipe wall at 550 mm from the bottom of the pipe (i.e., a heat insulating portion), indicates 40 degrees C. and 80 degrees C. after 10 kw / m2 and 50 kw / m2 of heat is supplied to the heating portion 4 of the heat pipe.

example 2

[0027] In example 1, an aqueous solution containing 2% weight concentration of ethylene glycol was used for the working fluid instead of the aqueous solution containing 1% weight concentration of ethylene glycol. No alteration was made in the rest of the conditions of example 1. Results are shown in FIG. 2.

example 3

Test for Congelation and Solidification

[0029] Glass test pipes having a diameter of 16 mm, a length of 150 mm and a thickness of 1 mm are used for the test for congelation and solidification. The aqueous solution containing 1% weight concentration of ethylene glycol was filled in each test pipe in the amount of 44 cm3, and stored for 20 hours in a freezer kept at minus 20 degree C. It was found that the aqueous solution of 1% weight concentration of ethylene glycol froze into sherbet-like ice, and the test pipe did not burst.

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Abstract

A heat pipe which can prevent frost damage of the pipe body due to freezing of the typical working fluid in cold climates by encapsulating an aqueous solution containing about 0.5 to about 10 wt % glycols as a working fluid, and which has a working performance almost comparable to that of the heat pipe in which water is used as the working fluid.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a heat pipe, and especially to a heat pipe which is improved in solving the problem of frost damage in cold climates. [0002] The present invention relates to the subject matter contained in Japanese Patent Application No. 2003-173467, filed on Jun. 18, 2003, which is expressly incorporated herein by reference. BACKGROUND OF THE INVENTION [0003] In the prior art, a heat pipe, in which a working fluid such as water is encapsulated in a metal pipe excellent in heat conductivity such as a copper pipe, and which utilizes latent heat generated by a phase change of the working fluid in the system from a liquid phase to a gas phase, as well as from the gas phase to the liquid phase, is used for the purpose of removing the heat from equipments, or of heating. For example, those heat pipes are widely employed for heat exchange in electronic equipments such as a personal computer, and for local heating of train stations, roadways, ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): F28D15/00
CPCC09K5/10F28F19/006F28D15/02
Inventor IMURA, HIDEAKIKOITO, YASUSHI
Owner THE FUJIKURA CABLE WORKS LTD
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