US20120267066A1

US20120267066A1 - Heat pipe, heat pipe system, and related method for long distance

Info

Publication number: US20120267066A1
Application number: US13/328,790
Authority: US
Inventors: Hun Chol Kim
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-03-27
Filing date: 2011-12-16
Publication date: 2012-10-25

Abstract

A heat pipe system and related method are disclosed for transporting vapor over long distances through the use of a heat pipe having no return pipe for return of the liquid condensate as traditionally associated with conventional heat pipes. The present subject matter also relates to a method involving the use of a working liquid vapor for the delivery of heat; an evaporator for the absorption of heat; an insulated partial vacuum-state conduit for delivery of the same to a condenser located a distance away, at which location the heat is utilized and the heat-laden vapor, condensed—without involving the use of a return pipe characteristic of conventional systems for the purpose of returning the working liquid condensate. Notably, elimination of the liquid condensate return pipe can help achieve increases in both the delivery speed of the heat-laden vapor and the overall distances involved with little loss in thermal efficiencies.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates and claims priority to and is a continuation-in-part of U.S. patent application Ser. No. 12/077,085, filed Oct. 2, 2008, which relates to and claims priority to Korean Certificate of Patent No. 10-0865718 issuing from Korean Application No. 2007-0029658, filed Mar. 27, 2007. The disclosures of the patent and application are both incorporated by reference herein in their entireties.

TECHNICAL FIELD

This application relates generally to heat pipes, and more particularly to heat pipes, systems and methods for long distance.

BACKGROUND

In general, a heat pipe is typically configured to transfer heat involving the use of a working liquid from one end to another, wherein there is an evaporator on one end of the pipe and a condenser on the other end of the pipe. The evaporator can cause a “phase change” in the working liquid in order to create a heat-laden vapor which includes the latent heat associated with the vaporization of said working liquid. The vapor, once it reaches the condenser, undergoes another phase change back to the liquid state due to the condensation function of the condenser, resulting in the release of energy in the form of heat, including said latent heat gained from vaporization, which gets discharged due to the internal heat differential between different phases.
In this field, a variety of methods have been employed for the return of the working liquid condensate back to the evaporator as such, in order that the process may begin anew, forming as it were, a closed-loop, fluidic heat-transferring system. A conventional heat pipe thus relies on the working liquid to undergo phase changes at both the evaporator end as well as the condenser end for the purposes of delivering the heat including the latent heat in vapor, where the working liquid is traditionally reclaimed from the condenser to be re-routed back to the evaporator, by means of a return pipe. Since the delivery speed of usable heat is dependent upon a constant supply of working liquid, such a system has inherent physical limitations. It requires the re-conveyance of said working liquid condensate back to the evaporator, so that it may, in condensed form, undergo the whole process again. Heat pipes comprising a closed system as such can deliver heat with some efficiency and speed, so long as the temperature and the internal pressure within the system matches the evaporator's thermodynamic requirements and provided the distance between the evaporator and the condenser is relatively short.
The maximum heat transport capability of the heat pipe in real use is determined by a variety of limitations, however. As mentioned, conventional heat pipes have inherent physical limitations in that there is the need constantly to return the working liquid condensate back to the evaporator from the condenser via a return pipe. There must be enough volume, speed and efficiency in order to achieve the right thermodynamic conditions, and the greater distances, the greater the challenge becomes in maintaining overall efficiency and utility. In conventional systems even heat pipes that are relatively shorter in length and smaller in diameter are known to be prone to heat pipe liquid return limitations, such as viscous or capillary limits—even when the system is assisted by power, gravity, centrifugal forces, etc. Indeed, such limitations have constituted the biggest obstacles to achieving efficient delivery of heat over long distances in substantial quantities via the use of heat pipes. Yet, conventional wisdom has assumed that a heat pipe must have a condensate return pipe if it is to achieve the transference of heat based on the use of a liquid condensate as described. Indeed, the very definition of a heat pipe is characterized by the presence of a return pipe. In conventional systems, the inherent limitations of the system are best described as “self-limiting systemic problems” for that reason, since it is the required presence of the return pipe for the system to actually work which results in a very “inefficient system.”
A need exists for a heat pipe system capable of traversing long distances without the use of a liquid condensate return pipe. The present subject matter in part solves problems associated with conventional systems by the clever and bold elimination of the use of a liquid condensate return pipe which is counterintuitive, non-obvious, and not anticipated by the prior art. By thus obviating not only the means of, but also the need for, the return of the condensate, it actually enables the transfer of far greater amounts of heat over far longer distances in the order of hundreds of meters to upwards of kilometers or more, at speeds and levels of efficiency far greater than otherwise afforded by the conventional art.
Many commercially useful applications are possible through the presently disclosed subject matter. As an example, the present subject matter can be of great use where there is an abundance of low temperature heat, e.g., condenser coolant outlets of electric power plants. Currently in a typical electric power station, only about a third of the energy produced is utilized for actual power generation, while two-thirds is wasted, as it is discharged into the atmosphere or the sea. The same is true for all instances involving electric power stations or internal combustion motors throughout the world. While there are some known instances in which steam or warm water have been employed for remnant heat transport to nearby city apartments, etc., those systems have largely proven to be quite inefficient and were rather limited in the distances they could span. Currently, there are no known instances of a heat pipe system without the means and use of a pipe for the return of the working fluid (e.g., a return pipe). The following table, Table 1, gives a simplified summary of the classification of heat transport methods to show the relative position of the present subject matter (shaded region).

TABLE 1

Classification of Heat Transport Methods

Classification	Mechanism	Special Features	Where Used	Efficiency

Conduction	By	Natural Method;	Hot Water Home	Slow Heating
(Contact &	Conductance	Easy to Use	Heating and PWR
Transport)	Warming		Primary Cooling:
			Historically Well
			Accepted
Conventional	Use Phase	Requires a	Distance and	100~1000 Times
Heat Pipe;	Change &	Working Fluid	Capacity Limited;	More Efficient
(Vapor	Latent Heat of	Return Pipe;	Satellite, Engines	Compared to
Transport &	Evaporation	Internal	and Electronics	Conduction
Contact)	of Working	Pressure set	Equipment;	Method; Maximum
	Fluid; Internal	(Fluid Return	Various Working	Transmit Speed is
	Pressure	Very Slow)	Fluids to Suit	the Sonic Speed
	Set to Phase		Temperature
	Change		Ranges



Chemical &	Chemical	High Energy	Direct Combustion	Power Conversion
Nuclear Fuel	Reactance	Density	and Engines;	Efficiency not high;
(Reactance	Conversion;		Engine, Generator	Well-
and	Electricity		& Transmission	Developed
Transport)	Generation		Line; Widely Used;	Technology
Wood, Fossil	Solar Energy	Abundant	Backbone of	Used Widely from
Fuel, etc.,	Stored over		Civilization	Aeon
(Transport	Long Time
and Burn)

** Heat Transport is Possible Only from High to Low Temperature.

SUMMARY

The present subject matter provides a heat pipe, system and method for transporting a large heat load of relatively low temperature over long distances by a novel heat pipe and method involving the use of an insulated transfer conduit to transport latent heat-laden vapor, by augmenting the novel heat pipe with a vacuum pump for maintaining the evaporated vapor state of the working liquid without any noticeable loss in heat during the transfer of the vapor via the insulated transfer conduit. It is also a general aim of the present subject matter to provide a heat pipe system that capitalizes on the higher efficiencies inherent in the heat laden vapor transfer, without the limitations of the condensate liquid return, by altogether eliminating the condensate return pipe in its entirety. The reason for eliminating the return pipe is because of the inherent limitations of the condensate return getting more and more pronounced, the longer return pipe gets and the larger the heat pipe gets in diameter. Transporting a large amount of heat over a long distance requires larger diameter pipes; unfortunately, such types of heat pipes have been shown to be limited in performance. The present subject matter, in part by eliminating the return pipe, enables not only the delivery of large amounts of heat load over far greater distances, but does so at sonic speed.

BRIEF DESCRIPTION OF THE DRAWINGS

These aspects and other advantages of the present subject matter will become readily apparent and more easily understood from the following detailed description of the presently preferred exemplary embodiments of the subject matter thereof with reference to the attached drawings, in which:

FIG. 1 is a cross-sectional view of an open-ended heat pipe delivery system, i.e., a heat pipe system with no condensate return pipe, according to one embodiment of the present subject matter; and

FIG. 2 is a schematic view of a portion of the (heat) transferring unit 20 according to one embodiment of FIG. 1 to illustrate such a long (heat) transferring unit 20 laid on a ground landscape feature.

DETAILED DESCRIPTION

The present subject matter will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The system described below is comprised of embodiments as in general heat pipe systems, but notably without a condensate return pipe whose absence only is claimed as being the new art:
FIG. 1 illustrates an embodiment of a cross-sectional view of an open-ended heat pipe delivery system 100. Heat pipe delivery system 100 can comprise an evaporating unit 10, a transferring unit 20, a condensing unit 30, and a decompression device or vacuum pump 22, and a sensor unit 60. In one aspect, decompression device or vacuum pump 22 can be physically attached to one end of the transferring unit 20, and regulated by signals from the sensor unit 60. Evaporating unit 10 can form a vapor from a working liquid, the vapor can be transported by a conduit 21. Condensing unit 30 can then discharge heat from the transferred vapor to the outside and condense the working liquid, and discharge the liquid to outside through the working liquid discharging unit 32 attached to the condenser 31. FIG. 2 is a schematic illustration showing a portion of the transferring unit 20 according to one embodiment of FIG. 1, since the transferring unit 20 may be constructed to traverse long distances of varying terrain heights; a plurality of working fluid discharging units 32 may be required. The individual system components are each described in greater detail hereinbelow.
With respect to a method for using the heat pipe delivery system 100 disclosed herein, the delivery system 100 can be used for absorbing heat from a primary steam loop by an evaporator 11 disclosed herein. Evaporation 11 can be adapted to absorb heat by absorption and latent heat of evaporation, having a separate independent system and under almost vacuum in the evaporator 11 and by having water continuously supplied or sprinkled to thereby evaporate into vapor. In one aspect, latent heat per weight is about 540 times larger for the amount of sprinkled water in the evaporator 11 compared to the amount of the ordinary cooling water. The temperature and the pressure of the primary loop/power generating turbine can be high but at the cooling end the temperature has been cooled down and the pressure is low. The quantity of heat, however, is all there. If there is a lower temperature somewhere in this case agricultural farms or apartment houses, by connecting with a well-insulated tube to a distant location, at any distance, to a similar condenser the vapor will flow and now heat will be absorbed by the condensing media in reverse, which may be used for heating, etc., and the vapor will transfer back to liquid/water. The condensed water is discarded. Thus, a large quantity of heat has been moved over a great distance. One advantage of systems and methods disclosed herein is that it is applicable to and capable of adapting to current power generating systems in place now, without changing such power generating systems.
The Sensor Unit 60: Sensor unit 60 is a name for collectively referring to any kind of sensor typically used in gathering data by sensing such items as temperature, pressure, and/or amounts of a liquid, and further, for sending out signals of information based upon such data as gathered, in accordance with an algorithm. Any changes in pressure (and temperature) within the conduit 21 as sensed by sensor unit 60 will cause the sensor to “signal” the decompression device or vacuum pump 22, meaning the sensor will, in accordance with a set algorithm, cause vacuum pump 22 to perform a decompression, thereby re-establishing the internal pressures to the level as originally established as a function of the temperatures of and at the evaporator and condenser. The liquid level at an evaporator 11 can be sensed or detected by sensor unit 60 which, in turn, activates the evaporator 11 to work on evaporating the supply of the working evaporation liquid at said evaporating unit 10. A liquid level at or in condenser 31 can also be sensed or detected by sensor 60, which in turn sends a signal to condensing unit 30 to cause it to release the working condensation liquid at said condensing unit 30. There is to be a steady level in the supply of water to said evaporator 11 by the evaporation working liquid supply unit 12, which supply of working liquid is held constant by a corresponding steady removal of water at the condenser end by the condensation working liquid discharging unit 32. The particular type of sensor employed is not necessarily material to the present subject matter (although the presence of sensor 60 is). In one aspect, sensor 60 can sense or detect one or more temperature(s), pressure(s), and/or amount(s) of liquid for the purpose of sending signals to one or more of the decompression device or vacuum pump 22, the evaporation working fluid supply unit 12, and/or the condensation working liquid discharging unit 32.
The Evaporating Unit 10: An evaporator 11 can be disposed at the evaporating unit 10 and can be equipped with an evaporation working liquid supply unit 12. The unit 12 can introduce the working liquid which is subject to a phase change in order to deliver the heat that gets released during the evaporation process. There can be a heat source disposed on or at evaporator 11 for use in heating and evaporating said working liquid in such a way that one skilled in the art can easily implement. The evaporator 11 can take on a hollow metal form optimal in absorbing heat more efficiently and whose internal surface area indicates an evaporation area where the working fluid in liquid form absorbs heat from the heat source. The evaporator 11 can allow working liquid to absorb heat from a heat source for initiating a phase change to delivering heat across long distances. The evaporator 11 should be of sufficient size commensurate with the amount of heat the system is calculated or hoped to transport.
The evaporator 11 has an evaporation working liquid supply unit 12, which can comprise and be constructed of two valves, one outer and the other inner, which work by one of the two valves being open while the other closed, which so allows for the evaporator 11 to maintain the vacuum state within which the evaporating liquid is supplied. The evaporation working liquid supply unit 12 can allow for the evaporator to be kept supplied with the evaporating liquid as the liquid is evaporated at the evaporator.
The Condensing Unit 30: The condenser 31 of the condensing unit 30 is similar in construction to the evaporator 11 of evaporating unit 10 and is placed in the vicinity of (or in contact with) a heat sink (not shown), which can be at a lower temperature than that of the heat source (thus effecting the pressure differential between the evaporating unit 10 and the condensing unit 30 in a transferring unit 20 causing the vapor to flow in the conduit 21 of the transferring unit 20). The condensing unit 31 can be spaced a long distance from the evaporating unit 10, for example, at least one kilometer and/or several kilometers apart. The condenser 31 has a condensation working liquid discharging unit 32 similar in function and construction to the evaporation working liquid supply unit 12 except that the movement of the liquid is in opposite direction, which so allows for the condenser to eliminate the liquid condensate collected as the heat is rejected at the heat sink without compromising vacuum state in the conduit. Allowing condensate at the condenser 31 to be discharged at the heat sink is novel. The condenser 31 must be sufficient in size for the amount of heat to be transported. As noted above, the liquid level at evaporator 11 can be sensed or detected by sensor unit 60 which, in turn, can activate the evaporator 11 to work on evaporating the supply of the working evaporation liquid at said evaporating unit 10. A liquid level at or in condenser 31 can also be sensed or detected by sensor unit 60, which in turn can send a signal to condensing unit 30 to cause it to release the working condensation liquid at said condensing unit 30 to the outside through the working liquid discharging unit 32 attached to the condenser 31. There should be a steady level in the supply of water to evaporator 11 by the evaporation working liquid supply unit 12, which supply of working liquid is held constant by a corresponding steady removal of water at the condenser end by condensation working liquid discharging unit 32.
As FIG. 2 illustrates, a plurality of working liquid discharge units 32 can be installed and spaced at intervals along conduit 21 to prevent conduit 21 from being blocked to formation of the condensation liquid in a low position. Such units 32 can be installed and spaced at the lowest points along conduit 21 and such units 32 can be controlled by signals from the sensor unit 60 for controllable release of condensate along conduit 21 as needed based upon one or more detections in pressure, temperature, and/or liquid levels.
The Transferring Unit 20: The conduit 21 in the heat transferring unit 20 can be made of an adiabatic material, or material insulated to be adiabatic, in order to rapidly transmit heat without losing in transfer. The conduit 21, can comprise a single tube or pipe (i.e., a single path from evaporator 11 to condenser 31 for transferring only vapor, with no liquid recovery path) for transferring latent heat laden vapor from the evaporator 11 to the condenser 31, and can generally made from common non-metallic materials and usually takes on the shape of a simple pipe, which is insulated on the exterior to create adiabatic conditions, and to transfer the heat vapor over long distance efficiently without significant heat loss. In one aspect, the single path of conduit 21 can merge with paths from other locations (i.e., where multiple evaporating units 10 are used), and the vapor from each location can merge into a single conduit 21 such that vapor in a single pipe is provided to condensing unit 30. In other aspects, a single conduit 21 can be connected to each of a plurality of evaporating units 10 so that the vapor can be combined within one place to transmit a large amount of vapor to one condensing unit 30. With sufficient temperature differences, sizes, and efficiencies of the evaporating unit 10 and the condensing unit 30, the diameter size of the conduit 21 of the transferring unit 20 and the speed of the vapor flow in the transferring unit 20 (which incidentally will not exceed the speed of sound, which is the speed of pressure propagation) will govern the amount of heat transported from the locations of the evaporating unit 10 and to the condensing unit 30. Thus, the present system is further characterized as having the form of a simple pipe of a diameter sized fairly for the efficient transfer of an amount of heat commensurate with such size. The conduit 21 should be sufficient in size for the amount of heat designed to be transported, with minimal heat loss except as to frictional loss along the wall and the bends, which is considered negligible.
The Decompression Vacuum Device or Vacuum Pump 22: The decompression vacuum device or vacuum pump 22 in the heat transfer unit 20 refers to a typical vacuum pump that when operated creates a negative air pressure to or within the system to which it is connected. Within such a system, the temperature as sensed or read at the evaporator 11 and the condenser 31 will determine what the pressure within the said system shall be, in accordance with the ideal gas law of thermodynamics: (pv=nRT, where, for an ideal gas which the evaporated vapor is approximated to be, p: the absolute pressure in kPa, v: the volume of gas in liters and is constant in the system, n: the number of moles, R: the universal gas constant=8.3145 J/mol K, and K is absolute temperature T, and it is seen that p is proportional to T in the system, and is given when T is given). Thus, the sensing or detecting of temperatures at evaporator 11 and condenser 31 makes it possible to compare between the pressure as should prevail within the system, versus that which, as measured, actually does prevail within the system. Any discrepancy between the two respective pressure levels (one as set or pre-determined, and the other, as measured) will result in a signal to the decompression vacuum device or vacuum pump 22, and activate the same. The decompression vacuum device or vacuum pump 22 can be used to maintain the evaporated vapor state of a working liquid by maintaining conduit 21 within a decompression vacuum state. The additional power required for the decompression vacuum device or vacuum pump 22 will be small once the initial setting is in place since there is no heat loss (insulated) in the conduit 21 of the transferring unit 20, nor any significant vapor losses (2-valve systems with virtually no vapor losses for both an evaporation working liquid supply unit 12 and a condensation working liquid discharging unit 32).
The subject matter herein has been described using preferred embodiments. However, it is to be understood that the scope of the subject matter is not limited to the disclosed embodiments. On the contrary, the scope of the subject matter is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims

1. A heat pipe system for long distance through which heat laden vapor can be transferred from a heat source to a heat sink without a return pipe of the liquid condensate, the system comprising:

an evaporator at an evaporating unit which is kept supplied with a working liquid from an external source via an evaporating liquid supply system, wherein the working liquid undergoes a phase change to create latent heat laden vapor by receiving heat from a heat source outside;

a conduit of a transferring unit for connecting the evaporating unit and the condensing unit, and which delivers heat laden vapor over a distance to a condenser;

the condenser at the condensing unit which discharges the heat to an external heat sink and in the process creates a liquid condensate of the working liquid and discharges the liquid condensate externally via a condensation working fluid discharging unit;

a decompression vacuum device or vacuum pump for maintaining an internal pressure of the conduit of a transferring unit; and

a sensor unit for sensing changes in at least one of a temperature, pressure, and water level in each of the evaporator, the condenser, and working liquid discharge units installed along the conduit of the transferring unit, and for sending signals to the decompression vacuum device or vacuum pump, the evaporating liquid supply unit, the condensation working fluid discharging unit and the working liquid discharge units installed at points along conduit of the transferring unit.

2. A method for using the heat pipe system according to claim 1 by:

creating latent heat laden vapor at an evaporating unit;

transporting the latent heat laden vapor over a distance spanning at least one kilometer;

receiving and condensing the vapor at the condensing unit to form a liquid condensate; and

discarding the liquid condensate.