JPS58165816A - Method of heating food and preserving warmth thereof and heating and warmth preserving container used therein - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Concerning heating and heat-insulating containers used for implementation.

As shown in Figures 1 and 2, fluid at a predetermined pressure or higher between the container walls 3 is automatically supplied to a sealed double-walled container made by fixing the upper part of the outer container 1 and the upper part of the inner container 2. A working fluid 5 is put between the container walls 3 of the heat insulating container, and the working fluid 5 is heated from the bottom of the outer container 1 to secondarily heat the object to be heated, such as food stored in the inner container 2. A method of heating the object 6 and, after heating is completed, keeping the object 6 warm by using the working fluid 5, which has risen in temperature in the same way as the object 6, as a heat radiation prevention wall or a heat storage material, is well known. However, in this heating and heat retention method, as shown in Figure 1, when the working fluid 5 is poured into the inner container 2 until the wall is heated, the temperature of the heated object 6 rises smoothly, but for some reason during the heat retention, the heated object 6 is heated. If the working fluid 5 cools down earlier, heat will flow back from the object to be heated 6 to the working fluid 5, making it impossible to maintain heat efficiently even though the purpose is to keep it warm. In addition, as shown in Fig. 2, if the working fluid 5 is heated to such an extent that the inner container 2 is not submerged, the temperature of the heated object 6 will rise steadily in this case as well, but the temperature of the working fluid 5 will rise during the heat retention after heating is completed. The temperature of the object to be heated 6 is lower than the boiling point (in this specification, the boiling point refers to the temperature at which boiling occurs under 1 atm pressure) and the temperature of the object to be heated 6 is lower than that of the working fluid 5 due to the infiltration of cold air into the inner container 2. When the temperature drops further below the temperature, even though the working fluid 5 still stores a large amount of heat, the heat cannot be transported to the heated object 6 and used effectively for heat retention.

The method of the present invention and the heating/insulating container used in its implementation solve these problems. When the temperature of the working fluid is lower than the boiling point and the temperature of the object to be heated is lower than that of the working fluid, the heat stored in the working fluid is transferred to the object to be heated, and the heat is transported to the object. It was devised for the purpose of maintaining the capacity at a high level and working effectively for heat retention.

One embodiment of the method of the present invention will be described with reference to FIG. 3, which shows a cross-section of a heating and insulating container utilized in carrying out the method. The outer container 1 and the inner container 2, which are made of non-metallic materials such as glass, stainless steel, or other metals, have their upper parts fixed together to form a sealed double-walled container. The distance 3 between the container walls of this sealed double-walled container is one space. When the pressure between the container walls 3 reaches a predetermined level or higher, the fluid automatically flows out to the outside due to the pressure, but in order to prevent the external air from flowing back into the container wall 3, a valve, which is one of the components, is installed. The check valve 8, whose body 8-1 is also one of the components and which is slightly recessed by its own weight into the valve seat 8-2 made of a heat-resistant elastic material such as silicone rubber, is placed in a sealed two-way position. The equipment is installed in a heavy-duty container. The lid 7 is detachably attached to the inner container 2. An object to be heated 6 such as food is stored in the inner container 2 . In order to heat and keep the object to be heated 6 warm using the heating and heat-insulating container configured as described above, first a working fluid 5 such as water is injected between the container walls 3, but the amount of injection depends on the content. It is preferable to set the amount so that the wall of the container 2 does not get submerged. The working fluid 5 can be injected from the opening of the valve seat 8-2 by removing the valve body 8-1. After injecting the working fluid 5, the valve body 8-1 is returned to its original position. If the bottom surface of the outer container 1 is heated in this state, the working fluid 5 will eventually reach its boiling point and a portion of it will become steam. The steam moves toward the upper part between the container walls 3 under the pressure, condenses on the container wall, releases heat of condensation, and heats the object to be heated 6. The condensed working fluid 5 returns to the bottom between the walls of the container 3 due to the action of gravity. This cycle is repeated to heat the heated object 6.
As the temperature rises, the pressure between the container walls 3 gradually increases, and when it reaches a predetermined pressure or higher, the check valve 8 opens and the air flows out into the atmosphere together with the steam. If the air and steam continue to flow out into the atmosphere while heating continues, the air between the walls 3 of the container will substantially disappear. Even if heating is continued at this point, the temperature of the heated object 6 will hardly rise any further, but the amount of working fluid 5 injected is too large and the wall of the inner container 2 is still in the liquid phase of the working fluid 5. If it is submerged, continue heating while releasing steam. When the wall of the inner container 2 is no longer immersed in the working fluid 5, heating is finished. When the heating is finished, the check valve automatically closes to prevent outside air from flowing back into the gap between the container walls 3. If the working fluid 5 cools down before the object to be heated 6 while keeping it warm after heating, the wall of the inner container 2 will not be immersed in the liquid phase of the working fluid 5 and the steam will not be refluxed as it would be during heating. Heat does not flow back from the heated object 6 to the working fluid 5. When the temperature of the working fluid 5 becomes lower than the boiling point and the temperature of the heated object 6 becomes lower than that for some reason, the following will happen. The backflow of air is prevented by the check valve 8, and the steam condenses and the volume is greatly reduced, so the space between the container walls 3
becomes a negative pressure state containing substantially no air. FIG. 4 shows a saturated vapor pressure curve of water, which shows that the lower the pressure between the container walls 3, the lower the temperature of water that can evaporate. As can be seen from this, if the pressure between the container walls 3 becomes negative, even the working fluid 5, which has become lower than the boiling point, will be heated in the same way as during heating until the pressure between the container walls 3 reaches the saturated vapor pressure corresponding to the temperature of the working fluid 5. By repeating evaporation and condensation on the wall of the inner container 2, the heat stored in the working fluid 5 itself is transferred to the heated object 6.
Transport to. If there is a back flow type of air between the container walls 3, even if the steam condenses and the volume decreases greatly, the space between the container walls 3
Since the pressure does not become negative, it is difficult for the working fluid 5 whose temperature is lower than the boiling point to evaporate. Therefore, the heat stored in the working fluid 5, which is lower than the boiling point, cannot be transferred to the object to be heated 6 which is lower than the boiling point, and therefore cannot be used effectively for heat retention. Fifth
In the figure, the partial pressure of air between the container walls 3 is 0.80.160 respectively.
The results of an experiment on how the amount of heat transport by the steam flow per unit area perpendicular to the heat transport direction changes when t(7) orr are shown. This figure shows that the smaller the partial pressure of air, the more heat can be transported even at low temperatures. In order to use the heat stored in the working fluid 5 to raise the temperature of the heated object 6, which has become even colder than the working fluid 5 for some reason during the heat retention, as quickly as possible, it is more advantageous to have a smaller amount of air between the container walls 3. I understand things too. As described above, during heat retention, the amount of air between the container walls 3 is greatly related to the temperature limit at which the working fluid 5 can be evaporated and the amount of heat transport of the working fluid 5 at a certain temperature. These things are the same for working fluids other than water.

In the gap 3 between the container walls, a chemical reaction occurs between the working fluid 5 and the material of the container, or a substance dissolved in the working fluid 5 is liberated, and gas is generated. These gases contain non-condensable gases that are too hot to condense during heating or keeping warm. If the space between the container walls 3 is kept sealed for a long time, non-condensable gas will accumulate. This region filled with non-condensable gas obstructs the steam flow, resulting in a decrease in heat transport (8) ability from the heat source to the heated object 6. However, in the method of the present invention, a check valve is activated each time heating is performed, as described above. Since the gas from these valves also flows out together with the steam, the heat transport capacity between the container walls 3 can be maintained at a high level.

Conventional heating and insulation containers do not incorporate the technical idea of the present invention, that is,
By preventing air from flowing backwards, the area between the walls of the container 3 is brought into a negative pressure state with virtually no air, and the heat stored in the working fluid 5, which has dropped below its boiling point, is transferred to the object to be heated whose temperature is lower than that of the working fluid 5. There is no technical concept of effectively using it to keep the heated object 6 warm by transporting it to the container 6, and therefore there is no need to prevent the backflow of air through the safety valve 4 and create a negative pressure between the container walls 3. Ta. Furthermore, safety valves of the type used in conventional heating and insulating containers 4, in which the valve body operates perpendicularly to the valve seat, particularly improve the accuracy of the valve body and valve seat, and We take measures to prevent deformation caused by the valve, select more appropriate materials that match the usage conditions, and take measures to prevent damage to the valve body and increased leakage due to rough handling during actual use. Air and steam leakage cannot be completely prevented unless the pressure of the valve body against the valve seat is sufficiently increased and the structure of the valve itself is carefully considered. Even small valves with a nominal diameter of 25 mm or less, whose valve body operates perpendicular to the valve seat and which have not been specially designed in this way, can withstand a test pressure of 5 to 6 kg/c7J using air. It is normal for there to be a leak rate of 25 to 50 ku per minute, converted to atmospheric pressure.

Conventional heating and insulation containers were able to sufficiently achieve their purpose even with this level of leakage, and safety valves with this kind of leakage were installed because they were easy to manufacture. In view of the technical concept of the present invention, it cannot be said that the conventional safety valve 4 substantially opens and closes the container wall to the outside. On the other hand, in the check valve 8 installed in the heated/insulated container of this embodiment, even if the valve body operates perpendicularly to the valve seat, the valve seat 8-2 is made of heat-resistant material like silicone rubber. By using a material with good elasticity and elasticity, air leakage is minimized to ensure a negative pressure state with virtually no air between the container walls 3 during heat retention, thereby achieving the object of the present invention. Therefore, the configuration is basically different from the conventional one. The fact that conventional heating and insulation containers are equipped with safety valves that allow air to leak to the extent mentioned above means that any prior art literature regarding safety valves used in sealed double-walled heating and insulation containers shows that there is no air leakage. There is no mention of consideration for leakage, and it is clear from the fact that there was no need for it as mentioned above.

Next, an embodiment using another heating/insulating container of the present invention will be described. Figure 6 shows the heating and heat-insulating container used in this embodiment, which differs from the heating and heat-insulating container used in the first embodiment in that the outer container 1 covers only the bottom of the inner container 2, making it double-tight. It forms a structural container, and the opening/closing means installed in the sealed double structure container is a cock 9 instead of a check valve 8. This heating and heating of foodstuffs etc. using the heat insulating container 6
To heat and keep warm, a working fluid 5 such as water is put between the walls 3 of the container and the bottom of the outer container 1 is heated, as in the previous embodiment. Leave cock 9 open while heating. The working fluid 5 rises in temperature and turns into steam. The steam moves to the upper part of the container wall space 3 and condenses on the inner container 2 wall. The heat of condensation heats the object 6, and the condensed working fluid 5 is heated by gravity. Returning to the bottom is similar to the first embodiment. If heating continues, the pressure between the walls 3 of the container will eventually become higher than atmospheric pressure, and steam will begin to flow out through the cock 9 along with air. When the outflow of air due to steam pressure is substantially completed and the temperature of the object to be heated 6 is sufficiently raised, the heating is finished and the cock 9 is closed. At this point, no non-condensable gas is present between the walls of the container 3. If the cock 9 is kept closed and kept warm, the airtightness of the cock is far superior to that of the safety valve 4, and as in the first embodiment, the space between the container walls 3 becomes a negative pressure state that does not substantially contain air. Since the wall of the inner container 2 is not immersed in the liquid phase of the working fluid 5, the heat of the working fluid 5 can be transported to the object to be heated 6 by its evaporation and condensation, and conversely, the heat can be transferred from the object to be heated 6 to the working fluid 5. There is no backflow.

Next, an embodiment using another heating/insulating container of the present invention will be described with reference to FIGS. 7 and 8. FIG. 7 is a sectional view of a heating and heat-insulating container used in this implementation. Similar to the one used in the second embodiment, the outer container 1 covers only the bottom surface of the inner container 2 to form a sealed double-walled container. This sealed double-walled container has a normally open type solenoid valve 10 that opens and closes the space between the container walls 3 and a white side that opens when the pressure between the walls 3 of the container reaches a predetermined level or higher.
A temperature sensor 12 which is set to N is also included in the device. Further, the outer container 1 has an injection port 13 for injecting the working fluid 5, and a removable cap 14 and a gasket 15 for sealing the injection port 13 are provided. A heat insulating layer 16 made of glass wool or the like covers the outer container 1 and the inner container 2, and the heat insulating layer 16 covers the outer skin 17.
covered with. Solenoid valve 10 Electric heater 11 Temperature detector 12
As shown in FIG. 8, the electric circuit includes a solenoid valve 10 and a temperature detector 12 connected in series, and the series connected circuit and an electric heater 11 connected in parallel. A power switch is connected in series with this combined circuit. To carry out the method of the present invention using the heating and insulating container shown in FIGS. 7 and 8, the object to be heated such as food 6 is placed in the inner container 2, and the working fluid 5 is supplied from the injection port 13. After inserting it, tighten the cap 14 firmly and turn on the power switch. Electric heater 11
The temperature of the working fluid 5 rises and becomes steam due to the heat, and the steam moves to the upper part of the container wall space 3 and condenses on the inner container 2 wall, heating the object to be heated 6 with the heat of condensation and the condensed working fluid. 5
It is the same as in the above-mentioned example that it returns to the bottom by gravity. If heating continues, the temperature between the container walls 3 will rise, and when it reaches a predetermined temperature, the temperature sensor 12 will turn ON.
0 opens. When the electromagnetic valve 10 is opened, the air between the container walls 3 flows out together with the steam. When air has finished flowing out due to steam and the object to be heated 6 has been sufficiently heated, the power switch is turned off. Then, the solenoid valve 10 closes and the electric heater 11 stops generating heat. In this state, the object to be heated, 6, is kept warm. Then, as in the two embodiments described above, the space between the walls 3 of the container becomes in a negative pressure state containing no air, so that the same effect as in the two embodiments described above is achieved. The heat insulating layer 16 prevents heat from escaping to the outside even during heating and keeping warm.

The heating and heat-insulating containers used in carrying out the method of the present invention are not limited to the three embodiments described above, but can be modified in various ways without departing from the technical idea of the present invention.

As described above, the method of the present invention and the heating/insulating container used for carrying out the method prevent heat from flowing back from the object to be heated 6 to the working fluid 5 during insulation, and the temperature of the working fluid 5 becomes lower than the boiling point. When the object 6 becomes even colder than that, the heat stored in the working fluid 5 can be transferred to the object 6 to be heated and used effectively to keep it warm.Moreover, its heat transport ability can be used to transfer heat to the object 6 each time it is heated. This is a very useful method that can effectively maintain heat by maintaining it at a high level by flowing out of the sealed double-walled container, and a heating and heat-retaining container used for carrying out the method.

[Brief explanation of the drawing]

FIGS. 1 and 2; Conventional heating; sectional view of a heat-insulating container; FIG. 3; sectional view of an embodiment of heating and heat-insulating container used in carrying out the method of the present invention; FIG. 4; saturated steam of water. FIG. 5 is a diagram showing the pressure curve; FIG. 6 is a diagram showing the relationship between the temperature of water, the partial pressure of air, and the amount of heat transport; FIG. 7 and 8, sectional views and electrical circuit diagrams showing other heating and heat-insulating containers used in carrying out the method of the present invention 1, outer container, 2. Inner container, 3. Between container walls, 4 safety valves,
5. Working fluid; 6. Object to be heated, 7. Lid, 8. check valve,
8-1 valve body, 8-2. Valve seat, 9. Cook, 10. Solenoid valve, 11 electric heater, 12 temperature detector, 13. Inlet, 14° cap, 15 packing, 16 heat insulation layer, 17. Outer skin patent applicant Keika Sa'uchi *1 Figure 2 Temperature °C 155 Figure 6

Claims (1)

[Claims] 1. A method of heating and keeping foods, etc., following the steps A, B, and C below. A1 An airtight double-structured container constituted by an inner container and an outer container that covers at least the bottom of the inner container, the container walls of the airtight double-layered structure can be substantially opened and closed from the outside of the airtight double-structured container. Food products, etc. are placed in the inner container of a heating and heat-insulating container equipped with an opening/closing means for heating, and a working fluid that evaporates and condenses during heating and keeping warm is placed between the walls of the container. The bottom of the outer container is heated with a heating device until all of the 81st-order abcd terms are satisfied. a. Creating vapor of the working fluid. b1 The steam condenses on the wall of the inner container and releases heat of condensation to heat the foodstuffs, etc. c1 The pressure of the steam causes the air between the walls of the inner container to flow out by opening the opening/closing means. d1 Opening the opening/closing means to allow the vapor to flow out until the liquid phase of the working fluid no longer contacts the wall of the inner container. C1 Close the opening/closing means to prevent air from flowing back into the space between the walls of the inner container to finish heating and keep the food, etc. warm. -2 A sealed double-structured container constituted by an inner container and an outer container that covers at least the bottom of the inner container, with the wall surfaces of the sealed double-structured container being substantially openable and closed to the outside of the sealed double-structured container. A heating and heat-insulating container for use in carrying out the method for heating and keeping foods, etc., as set forth in claim 1, characterized in that the container is equipped with a means for opening and closing freely.