KR100363446B1 - Rib Type Heat Pipe Cookwares - Google Patents

Abstract

The present invention is a heat pipe cooker having a characteristic of improving food cooking by heating while maintaining a constant temperature in all parts of the cooker, capillary suction required for normal operation by shortening the circulation length of the working liquid to determine the performance of the cooker The pressure difference is reduced, and a variety of operating fluids, which are heat transfer mediums, are selected to configure a cooker having a wide range of temperature characteristics, and the manufacturing cost can be reduced.

The principle of the heat pipe cooker is as follows. In the middle of the cooker there is a fully enclosed space filled with the working fluid and its vapor, inside and outside the metal containers. The inner container and the outer container are partly strongly bonded to each other. At the bottom of the sealed space, a metal screen is fixed by spot welding or the like. The liquid is moistened in this part, and the upper space is filled with steam. During cooking, heat enters the bottom of the outer container, which causes the working fluid to evaporate. The vaporized vapor transfers heat to the bottom and side of the inner container and condenses. The condensate liquid is evenly wetted back to the bottom of the enclosed space due to gravity or the capillary forces of the screen wick (wick). Due to this principle, the inside of the cooker is maintained at a constant temperature, thus allowing cooking at an even temperature.

By the way, since the liquid passages of the screen and the ceiling surface are all connected smoothly, the circulation loop of liquid was formed as one in a sealed space (refer FIG. 3). As a result, the liquid condensed from the ceiling flows to the center of the ceiling and drops to the bottom of the droplet. At the bottom, the liquid soaks to the outermost part of the floor and receives heat from an external high temperature heat source, and the liquid evaporates. Accordingly, the flow length of the liquid is very long, the whole liquid circulates in one loop, and the pressure loss increases, so even if only a little heating, the liquid does not get wet on the outer edge of the floor, but it dries up early and overheats, thereby limiting the maximum heat transfer amount. . In addition, the side wall of the cooker does not reach the liquid is only overheating, there was a problem that does not heat the contents. However, in the present invention, a circulation loop of liquid by installing ribs or dams in which liquid can no longer flow on the floor, ceiling and sidewalls so that the liquid does not cross the ribs or dams at this point and falls to the bottom and sidewalls of the droplets. Made several. This reduces the circulation length and circulation amount of the liquid per loop in inverse proportion to the number of loops. In heat pipes, the larger the required amount of circulation of the working fluid and the longer the circulation distance, the smaller the maximum heat transfer in inverse proportion to each, so that the maximum possible heating amount of the heat pipe cooker increases in proportion to the square of the number of loops, enabling rapid heating. Will be done. Furthermore, liquid flows down from the sidewall of the cooker to increase the amount of liquid evaporation, thereby increasing thermal efficiency and preventing overheating of the sidewall.

The reason why such a device is required is that cooking temperature and heating rate are different according to the type of food, and thus, an optimal working fluid must be selected, and the surface tension and latent heat of evaporation are often small. This will increase the total circulation demand of the working fluid, but not enough suction due to capillary forces, resulting in poor fluid flow and rapid heat transfer and a partial overheating of the vessel. Therefore, it is necessary to reduce the circulation demand per loop by dividing the circulation loop of the working fluid into several, and also to reduce the circulation length, to facilitate smooth flow and to enable rapid heating.

Description

Rib or Dam Heat Pipe Cookers {Rib Type Heat Pipe Cookwares}

The present invention is a heat pipe cooker having a characteristic of improving the cooking of food by heating while maintaining a constant temperature in all parts of the cooker, by dramatically improving the structure of the wick to determine the performance of the cooker, the operating fluid as a heat transfer medium It aims to lower the production cost by simplifying the structure by selecting a wide range of temperature characteristics.

It is very important for cooking to maintain a constant temperature of the wall and bottom surface in a typical cooker. This is because food can be heated evenly to improve the taste and thermal efficiency can be improved. For example, it is based on this principle to cook rice in a cauldron, or to cook steamed rice in a pot with a wire-like structure. It is for this reason that when making stainless cookers with low thermal conductivity coefficients, a multi-layered structure bonded with aluminum with good thermal conductivity in between is produced. However, aluminum having excellent thermal conductivity does not have an infinitely large thermal conductivity, so it is impossible to make an ideal cookware. In other words, it is impossible to realize an ideal cooking utensil by relying only on thermal conductivity.

Overcoming these limitations, the heat pipe cooker, or thermosyphon cooker, has been proposed in a way that can theoretically be cooked at full isothermal temperature. The heat pipe cooker is an application of the heat pipe technology developed to maintain the surface temperature of the satellite uniformly. The heat pipe cooker is made of a double hermetic container in the internal structure of a cooking utensil such as a frying pan, a pan and a rice cooker. The working liquid in this confined space is evaporated and condensed at a constant temperature to maintain a constant temperature in any part of the cooker, which is as effective as making a cookware from an ideal material with an infinite thermal conductivity. do. That is, even if somewhat uneven or locally heated by a flame or heating wire from outside the cooker, since all parts are cooked evenly while maintaining the inside surface of the cooker at a uniform temperature, the cooking effect is good. Moreover, the internal structure of the cooker contains only a very small amount of working fluid, so the overall heat capacity is very small, making the temperature control of the cooker very fast and the risk of overheating extremely low. The advantage of this mechanism is that the temperature at all locations in the confined space is constant as the saturation temperature of the working liquid. In other words, a certain temperature is maintained at every location, even if one part is more cooling than the other or the heating is not uniform. In addition, since the saturation temperature of the sealed liquid and vapor mixture can be continuously changed, for example, when the steam is used as the working fluid, the temperature of the inner cylinder is uniform at not only 100 degrees Celsius but also much lower or much higher temperature. It is possible to heat the contents inside while maintaining the temperature. Patent 200332 is an example of applying this principle to a rice cooker, and Publication No. 10-1998-068910 is an example of applying this principle to a general cooking appliance.

However, these inventions have a structure in which a metal screen is directly mounted on the bottom surface by a spot welding method, etc. 1) There is a disadvantage in that capillary suction is not sufficiently rapid for a small surface tension and high viscosity working fluid. In order to solve the problem of productivity, the proposed perforated plate heat pipe cooker of Application No. 10-1999-0009069, which solves some of the problems of productivity but does not solve the rapid heating mentioned above. The present invention seeks to overcome this drawback.

1 is a cross-sectional view and a plan view of a heat pipe cooker equipped with a wick and ribs,

2 is a half sectional view of the enclosed space.

3 shows the circulation of the working fluid in a conventional heat pipe cooker,

4 is a conceptual diagram of a dam installed in place of ribs.

* Explanation of symbols for main parts of the drawings

1: outer cylinder, 2: confined space, 3: inner cylinder, 4: rib 5: wick 6: close spring 7: ceiling dam 8: floor dam

In Figure 1 shows a cross-sectional view of the cooker. The cooker has a metal outer cylinder (1) of aluminum, copper or stainless steel (1) having a thickness of about 1 to 3 millimeters, and has an airtight space of 10 millimeters or less (2), and an inner cylinder (3) containing food therein. have. Conventionally, the metal screen was closely attached to the bottom surface of the outer cylinder side of the sealed space by spot welding or the like. (This metal screen serves as a kind of wick to move the working fluid in the enclosed space to quickly spread throughout the floor through capillary action.) Since the liquid passages were all connected smoothly (see FIG. 3), a circulation loop of liquid was formed as one in the sealed space. As a result, the liquid condensed from the ceiling flows to the center of the ceiling and drops to the bottom of the droplet. At the bottom, the liquid soaks to the outermost part of the floor and receives heat from an external high temperature heat source, and the liquid evaporates. Accordingly, the flow length of the liquid is very long, the entire liquid circulates in one loop, and the pressure loss increases, so even if only a little heating, the liquid does not get wet on the outer edge of the bottom, but it dries up early and overheats, thereby limiting the maximum heat transfer amount. . In addition, the side wall of the cooker does not reach the liquid, but only overheating, there is a problem that does not heat the contents. However, in the present invention by installing a rib or a dam in which the liquid can no longer flow on the floor, ceiling and side walls Multiple liquid circulation loops were made by allowing the liquid to fall to the bottom and sidewalls of the droplets without passing over the rib or dam at this point (see Figure 2). This reduces the circulation length and circulation amount of the liquid per loop in inverse proportion to the number of loops. In heat pipes, the larger the required amount of circulation of the working fluid and the longer the circulation distance, the smaller the maximum heat transfer in inverse proportion to each, so that the maximum possible heating amount of the heat pipe cooker increases in proportion to the square of the number of loops, enabling rapid heating. Will be done. Furthermore, liquid flows down from the sidewall of the cooker to increase the amount of liquid evaporation, thereby increasing thermal efficiency and preventing overheating of the sidewall.

The principle of operation of a cooker with this structure is now described in detail (see Figure 3). First, a conventional heat pipe cooker equipped with a flat wick on the bottom of a confined space and without ribs or dams is as follows. The outer cylinder at the bottom of the confined space transfers the heat transferred from the outside to the working fluid soaked in the wick. The working liquid evaporates and spreads through the vapor passage in the confined space to all the places in the confined space. Since the inner side of the steam passage is cold, steam condenses at this side to give up the heat of condensation, which is transferred to the food in the inner tube for cooking. The condensed working fluid drops into the wick on the bottom by gravity, and once the working fluid falls, the entire bottom surface is evenly wet again due to the capillary suction of the wick. The wick helps prevent overheating of the cylinder and keeps the temperature uniform.

In the sealed space of the above cooker, the temperature of the outer cylinder surface is only 0.1 degree to 1 degree higher than the inner cylinder surface and can maintain almost constant temperature in all parts. This is due to the thermodynamic equilibrium of the vapor filling the confined space at almost completely constant pressure and hence its evaporation and condensation temperatures constant at any site. The slight temperature difference is caused by the heat conduction characteristics of the liquid, the inner cylinder and the outer cylinder, such a temperature difference is very small, in particular, the cooker inner cylinder operates by maintaining a temperature difference of only about 0.1 degrees. Therefore, it can be considered that the theoretical ideal cooker, that is, a cooker having an infinite thermal conductivity of a material, is implemented.

On the other hand, the working fluid can be used as long as it is a pure material in theory, but in practical applications, it is required to have a high surface tension and a low viscosity to smooth the flow in order to maintain a large capillary force. In addition, since the heat transfer amount is the product of the circulation amount of the working liquid and the latent heat of evaporation, the latent heat of evaporation needs to be large to increase the heat transfer amount. In addition, if the internal pressure of the enclosed space is too high, it is dangerous to have a vapor pressure of 1 atm or less at around 100 degrees Celsius, and even if it is heated without food, the steam pressure may be increased so that there is no danger of explosion even if it is overheated at about 200 degrees Celsius. It would be more desirable if it remained below. In addition, in order to prevent the risk of accidents in case of leakage, conditions such as no combustibility, no toxicity to the human body, and environmental friendliness are required.

However, there are not many working fluids that satisfy these demanding conditions. Often for fluids with boiling points above 100 degrees Celsius, the surface tension of the fluid may be so small that it may not flow smoothly. In ordinary liquids, the lower the latent heat of evaporation, the lower the surface tension. The structure of the conventional heat pipe cooker with a long circulation length of the working liquid as shown in FIG. 3 is suitable for a working liquid such as distilled water having a latent latent heat and a high surface tension, but is not suitable for other kinds of working liquid having a small latent latent heat and a surface tension. . In other words, when the latent heat of evaporation of the working fluid is small, the circulation demand of the working fluid to satisfy the required heating amount increases in inverse proportion to the latent heat of evaporation, thereby increasing the pressure loss of the liquid, whereas when the surface tension decreases, the capillary suction pressure is increased. Decreases, making circulation of the working fluid more difficult. One way to overcome this drawback is to divide the cooker into several smaller heat pipes, conceptually. That is, as shown in FIG. 3, a conventional heat pipe type cooker has only one liquid circulation loop, and thus operates as one heat pipe as a whole. However, when the ribs are set in the middle, as shown in FIG. 1, the liquid flows down the droplets along the ribs as shown in FIG. That is, as shown in Figure 2, the condensed liquid flowing along the ceiling descends along the ribs and is evaporated again while wetting only a close distance of the loop interval at the bottom. As a result, the liquid circulation distance per loop is shortened in inverse proportion to the number of loops, thereby reducing the input loss amount. However, the capillary attraction per loop is inversely proportional to the capillary diameter of the wick and is constant regardless of the number of loops. Therefore, the maximum amount of liquid circulation per loop increases in proportion to the number of loops. Since the heat transfer amount is equal to the circulation rate of the entire liquid multiplied by the latent heat of vaporization of the liquid, when N loops are set, the heat transfer amount per loop is N times higher than that of one loop, and since there are N such loops in total, the total heat transfer amount is It increases in proportion to the square of N. In addition, when the rib is installed on the side wall as shown in FIG. 2, the condensed liquid flows to the food and flows down to the outer side wall when the ribs are heated on the inner side wall of the closed space. Is heating, so it evaporates before reaching the bottom to form another short liquid circulation loop. This improves thermal efficiency and prevents overheating of the sidewalls.

The inner and outer cylinders of the cooker are often manufactured to have a slight inclination. In this case, the ribs must be installed perpendicularly to the inclined direction of the barrel to make a proper circulation circuit. The rib may also be replaced with a dam that cuts off the flow path from the ceiling and shortly cuts off the flow path by gravity at the bottom (see Figure 4). Even when the cooker is flat, it is often used in a slightly inclined state in actual use.In this case, in order to work properly, the inner and outer cylinders of triangles, squares, hexagons, etc. are completely enclosed or partially open shapes. By installing a flow barrier, it is possible to ensure more reliable operation. The dam can be made mechanically when the inner and outer cylinders are machined, or a metal wire can be cut and pasted. In addition, it can be installed by filling the paint or epoxy, plastic, etc. at appropriate intervals on the screen or perforated plate forming the passage of the liquid on the floor. It is also possible to bend the steel plate or steel wire into an appropriate shape so that it is held while applying a pushing force between the inner and outer cylinders. In this case, the steel plate or the steel wire may also serve as a tool for bringing the screen or the porous plate into close contact with the bottom surface.

.

Claims (1)

Using a closed cycle of evaporation and condensation of the working fluid in the closed space, a wick is mounted on the bottom of the closed space filled with only the working fluid and the working fluid vapor between the inner and outer cylinders, and the working fluid is injected as much as the wick. In a cooker equipped with a heat pipe where evaporation occurs on the surface of the wick and the liquid circulates due to capillary force of the wick, the heat having a rib or a dam inside the sealed space for the purpose of reducing the circulation length of the working liquid. Pipe cooker.