Heat Transfer. February ; 2 : Dryout in a heat pipe evaporator is caused by insufficient condensate supply through the wick structure. Dryout is generally considered a failure of the heat pipe operation. This article investigates the dryout phenomenon in carbon nanotube CNT based biwick structure. The incipience and expansion of the dryout zone on the CNT biwick structure are visualized.
Variation of the evaporator temperatures at various heat fluxes is measured to characterize the temperature responses on the biwick dryout. Results based on both visualization and measurement show that dryout of CNT biwick structures is affected by vapor flow induced droplet splash and vapor occupation of liquid transport passages, which reduces the liquid supply to the hottest region and creates a local dry zone.
On the curves of heat flux versus the evaporator temperature, dryout can be defined as the appearance of the inflexion point during the heating period, and associated with the existence of a large temperature hysteresis in a heating and cooling cycle.
Liquid splash and interactions between vapor and liquid flows also increase the pressure drop weight in the evaporator over the system loop and result in more notable heating area effect on biwick structures when compared with traditional monowick structures. Sign In or Create an Account. This oxidation is most apparent by the color of the wick.
The brighter the copper, the fresher the wick. Oxidized copper will darken like a dirty penny. The more oxidized the copper, the slower the wicking action. We generally recommend replacing wick after 2-years, but that can be longer or shorter depending on storage conditions.
Keep the wick bag or can sealed for maximum product life. The outside of the spool of wick becomes oxidized first. Be the first to receive email alerts on special offers, new products, and more delivered right to your in-box.
While most modern candles do not smoke when burning, even the cleanest candles tend to produce significant quantities of smoke when the flame is blown out. The smoke that is produced when a candle is blown out occurs as a result of the incomplete combustion of the wax that remains in the wick being poorly combusted by the embers remaining within the wick.
The smoking usually continues to occur until the embers finally go out also. The smoking candle also produces a malodor from the incompletely burned wax. This smoking is unpleasant, especially when the primary purpose of a fragranced candle is to produce a pleasant odor in the air. The malodor produced from the blown out candle is perceived as a real negative by the user.
Devices have been designed to prevent a candle from smoking when it is extinguished. Metal smokeless candle snuffers have been invented that bend the lighted candle wick into the candle wax, thereby putting out the flame without allowing a burning ember in the wick to produce incomplete combustion of the wax remaining in the wick. After putting out the flame the wick must then be straightened in order to be lit again the next time the user wishes to light the candle.
The candle snuffer is not easy to use and requires that it be cleaned after each use using a tissue or paper towel. Additionally, the snuffer has to be stored in a convenient location for future use. A candle snuffer is an inconvenience for someone who does not wish to have to store and clean a device to prevent their candle from smoking when extinguished. Additionally, convenience would require a separate snuffer in proximity of every candle, which in many households is an undue expense and storage problem.
Flame retardant materials have been included in candles previously U. The flame retardants have been incorporated into the fuel portion of the candle to produce self extinguishing candles.
The incorporation of a flame retardant into the fuel does not prevent the candle from smoking when blown out. Flame retardants have also been used in the wick holder U. The incorporation of the flame retardant into the wick support helps to extinguish the flame when it reaches the bottom of the candle.
This is done as a safety feature to prevent the consumption of all of the candle fuel causing the bottom of the candle to become dangerously hot.
This use of flame retardant does not reduce the smoking of a candle when it is blown out. Flame retardants have been used in a wick to automatically extinguish the flame U. The flame retardant is contained only in the lower portion of the wick. As the candle burns and consumes itself, the lower portion of the wick that contains the flame retardant comes into the flame and automatically extinguishes the flame. The flame retardant is not present at a consistent level but rather is concentrated in lower sections of the candle to promote the self-extinguishment of the candle.
The present invention solves the problem of a smoking wick after the candle is blown out without the requirement of additional snuffing devices. By introducing a substantially uniform amount of flame retardant into the wick structure of a candle, smoking of the wick can be minimized when the flame is blown out. The present invention includes systems and methods for reducing smoke and malodor production by incorporating a flame retardant into at least a portion of a wick. The flame retardant is preferably included at a concentration that will not extinguish the flame but rather that will reduce the smoking and malodor resulting when the flame is extinguished.
In one embodiment the present invention is comprised of a solid wicking material in intimate proximity to a flame retardant. The flame retardant is present at a substantially uniform level throughout the wick such that when a flame is extinguished the wick exhibits reduced smoking as compared to normal untreated wicks.
In one embodiment the flame retardant is present in the fuel at a level that will not extinguish the flame but will reduce smoking and malodors when the flame is extinguished. A wick that has been treated with the flame retardant may be incorporated into a candle, an oil lamp, or any other wick-burning device. The wick of the present invention may be constructed from any wick material that can sustain a flame. Numerous wick materials are currently used in commerce.
These include materials comprised of cellulose, cotton, paper, fiberglass, polymer, ceramic, and fabric. Wicks that are cored may be used also including paper-cored, cotton-cored, and metal-cored wicks.
The preferred properties of the wick used in the present invention are its ability to transfer a liquid fuel from a reservoir to the flame and the ability to be associated with a flame retardant at a level that allows the flame to propagate but prevents a burning ember from allowing smoking after the flame has been extinguished. Lyons, Wiley-Interscience are suitable for use in the present invention.
The flame retardants described in this book are incorporated by reference herein in its entirety. Suitable flame retardants for use with the present invention are those that can be incorporated into a wick. A preferred flame retardant is incorporated into the wick and does not substantially migrate from the wick into the fuel either during storage or during the burning process.
These may be inorganic, organic, or organometalic compounds. For microscopical use, the wicks, as normally supplied, are much too large. As smaller wicks do not seem to be commercially supplied with these lamps, the average lamp needs to be modified. Inserting a short length of narrow metal tubing with an inside diameter about the size of cotton wrapping string is a common expedient, if not the most pleasing aesthetically; such a modification is shown in the case of the alcohol lamp on the left in Figure 1.
Both of the lamps in Figure 1 lack a vent for pressure equalization. Figure 1 illustrates two alcohol lamps found in a typical industrial laboratory; they are both glass-stoppered, and employ a cork surmounted by a metal disc and wick support—both show evidence of having burned around the cork, following flooding; notice also the buildup of soot in the ground-glass cap on the left, and the general corrosion of the metal parts.
Both lack a vent. Figure 2 illustrates, on the left, an almost new version of the same kind of glass-stoppered alcohol lamps as in Figure 1, but with a cork that fits lower in the neck. On the right of Figure 2 is an example of an alcohol lamp with a threaded neck, and an aluminum screw-threaded cap, with integral wick support, and a loose-fitting aluminum hood.
Neither lamp has a vent hole. Figure 3 illustrates a Balsam bottle that has been converted into an alcohol lamp; the hood, with ground-glass base, is missing—perhaps that is why someone converted this container. The hole in the cork has not been bored straight, and the wick does not protrude enough.
There is no vent hole. On the right, in Figure 3, is illustrated a replacement cap and wick assembly for an alcohol lamp with a threaded neck. It features a captive wick cover, and the wick end has been bound to prevent fraying. Figure 4 illustrates two examples of faceted fuel reservoirs. The faceted feature is not merely decorative; it is an old design purposely made so as to be able to tip the lamp while it is in use, as illustrated by the lamp on the right.
The reason for tilting the lamp while in use is so that when soldering, or using the blowpipe, or when performing borax bead and microcosmic salt tests, or sharpening tungsten needles with molten sodium nitrite, drippings will not fall on to the wick, extinguishing the flame. Neither lamp has a vent hole, which would be a marked improvement. Figure 5 illustrates several designs of wicks and their feed-through supports. The brass feed-through on the left is paired with a woven glass fiber wick; this fitting replaces a cork.
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