1. Technical Field
The disclosure generally relates to heat transfer apparatuses such as those used in electronic equipment, and more particularly to a heat pipe with high heat transfer efficiency.
2. Description of Related Art
Heat pipes are widely used in various fields for heat dissipation purposes due to their excellent heat transfer performance. One commonly used heat pipe includes a sealed tube made of thermally conductive material with a working fluid contained therein. The working fluid conveys heat from one end of the tube, typically referred to as an evaporator section, to the other end of the tube, typically referred to as a condenser section. Preferably, a wick structure is provided inside the heat pipe, lining an inner wall of the tube, and drawing the working fluid back to the evaporator section after it condenses at the condenser section.
During operation of the heat pipe in a typical application, the evaporator section of the heat pipe maintains thermal contact with a heat-generating electronic component. The working fluid at the evaporator section absorbs heat generated by the electronic component, and thereby turns to vapor. The generated vapor moves, carrying the heat with it, toward the condenser section. At the condenser section, the vapor condenses after the heat is dissipated. The condensate is then drawn back by the wick structure to the evaporator section where it is again available for evaporation. The condensate and the vapor move toward opposite directions. The vapor is prone to obstruct the movement of the condensate back to the evaporator section. Thus, a speed of the working fluid flowing back to the evaporator section decreases. Moreover, the evaporator section is then prone to becoming dry.
What is needed, therefore, is a heat pipe to overcome the above described shortcomings.
Embodiments of the present heat pipe will now be described in detail below and with reference to the drawings.
Referring to
The tube 100 is made of metal or metal alloy with a high heat conductivity coefficient, such as copper, copper-alloy, or other suitable material. The tube 100 is elongated and has an evaporator section 110, an adiabatic section 130, and a condenser section 120 defined in that order along a longitudinal direction thereof.
The wick structure 200 is formed by weaving a plurality of metal wires such as copper or stainless steel wires, or by sintering metal powder. The wick structure 200 extends longitudinally from the evaporator section 110 to the condenser section 120. An inner space 140 is longitudinally defined between inner surfaces of the wick structure 200. The wick structure 200 draws the working fluid back to the evaporator section 110 from the condenser section 120.
Referring to
In the illustrated embodiment, the evaporator section 110 of the heat pipe 10 is positioned in intimate thermal contact with a heat-generating component 400 such as an electronic component. During operation of the heat-generating component 400, the working fluid in the wick structure 200 of the evaporator section 110 absorbs heat from the heat-generating component 400 and is vaporized. Thus, the vapor generates a vapor pressure which propels the vapor to flow through the through holes 320 and move towards the condenser section 120. According to the law of conservation of mass, a mass of the vapor satisfies the condition: ρinletVinletAinlet=ρoutletVoutletAoutlet, wherein ρ represents a density of the vapor, A represents a cross-sectional area of each through hole 320, and V represents a flow velocity of the vapor. The value of ρinlet is typically approximately equal to the value of ρoutlet. Because the diameter of the through hole 320 decreases from the inlet to the outlet, the value of Ainlet is larger than the value of Aoutlet. Therefore, the value of Vinlet is less than the value of Voutlet. Thus, a flow velocity of the vapor increases along a flowing direction of the vapor. The vapor can accordingly rapidly transmit to the condenser section 120 for dissipation of the heat of the vapor. A heat dissipation efficiency of the heat pipe 10 can thus be improved.
On the other hand, because the diameter of each through hole 320 reduces along the flowing direction of the vapor from the evaporator section 110 to the condenser section 120, the vapor in the through hole 320 is compressed towards a center axis of the through hole 320. Thus a ratio of the vapor obstructing the condensate of the wick structure 200 in the adiabatic section 130 and the condenser section 120 is decreased, and the condensate in the adiabatic and condenser sections 130, 120 can flow back to the evaporator section 110 rapidly. According to the law of conservation of energy, the value of Vinlet is less than the value of Voutlet. Therefore, the kinetic energy of the vapor at the outlet is larger than that of the vapor at the inlet of the through hole 320, and the thermal energy of the vapor at the outlet is less than that of the vapor at the inlet of the through hole 320. Thus, a condensing efficiency of the vapor can be improved.
Referring to
Referring to
It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
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101118099 | May 2012 | TW | national |