Heat sterilization device and heat sterilization method

Abstract

The heating sterilization apparatus of the present invention comprises: a sterilization tank having an internal receiving space for accommodating an object to be sterilized by heating with a high-temperature fluid, and receiving a supply of a high-temperature fluid for heating and sterilizing the object and a supply of cooling water for cooling the object after heating and sterilization with the high-temperature fluid; and a control unit that, before cooling the object by cooling with the cooling water, uses medium-temperature water, which has a temperature higher than that of the high-temperature fluid but lower than that of the high-temperature fluid, to perform medium-temperature water heat recovery control for recovering heat from the sterilization tank after heating and sterilization.

Description

Heat sterilization device, sterilization object, and heat sterilization method The present invention relates to a heat sterilization device, a sterilization object and a heat sterilization method. Conventionally, there is known a heat sterilization device for heat sterilizing an object to be sterilized. For example, such a heat sterilization device is known from Japanese Patent Application Laid-Open No. 2000-69948. Japanese Patent Application Laid-Open No. 2000-69948 discloses a conditioning sterilization apparatus (heat sterilization apparatus) for heat sterilizing an object to be sterilized (object to be sterilized). The conditioning and sterilization device disclosed in Japanese Patent Publication No. 2000-69948 is equipped with a sterilization tank, a warm water tank, a cold water tank, a water supply tank, a spray nozzle, a heat exchanger, and a control device (control unit). The sterilization tank contains the sterilized objects inside. The warm water tank is a tank for storing warm water to be sprayed from the spray nozzle. The spray nozzle sprays the warm water supplied from the warm water tank, which has been heated to the heating and sterilization temperature, into the sterilization tank as jet water (high-temperature fluid) to heat and sterilize the sterilized objects contained in the sterilization tank. Here, the conditioning and sterilization device, after heating and sterilizing with the high-temperature jet water, cools the warm water by heat exchange with the water supplied from the water supply tank in the heat exchanger, so that the temperature of the warm water supplied from the warm water tank drops to a predetermined temperature. Furthermore, the conditioning and sterilization device recovers the warm water that has dropped to the predetermined temperature into the warm water tank. Then, the conditioning sterilizer sprays cooling water supplied from the cold water tank as jet water into the sterilization tank in order to cool the heated sterilized objects and the sterilization tank. However, in the conditioning and sterilization device disclosed in Japanese Patent Application Laid-Open No. 2000-69948, the temperature of the hot water, which has been heated to the sterilization temperature, decreases due to heat exchange with the cold water in the heat exchanger before being recovered into the warm water tank. Therefore, the conditioning and sterilization device disclosed in Japanese Patent Application Laid-Open No. 2000-69948 has a problem in that the time required to heat the hot water (high-temperature fluid) to the sterilization temperature increases when the hot water is sterilized again after heat recovery. The present invention is completed to solve the above-mentioned problems. One purpose of the present invention is to provide a heat sterilization device, a sterilization object and a heat sterilization method, which can suppress the time required to heat the high-temperature fluid to the heat sterilization temperature from being prolonged during the next heat sterilization after heat recovery. The heating sterilization device of the first aspect of the present invention comprises: a sterilization tank having an accommodation space inside which an object to be sterilized is accommodated by a high-temperature fluid, and receiving a supply of the high-temperature fluid for heating and sterilizing the object to be sterilized and cooling water for cooling the object to be sterilized after being heated and sterilized by the high-temperature fluid; and a control unit for performing heat recovery control of the medium-temperature water to recover heat from the sterilization tank after heating and sterilization, using medium-temperature water generated separately from the high-temperature fluid and having a temperature higher than the cooling water but lower than the high-temperature fluid before cooling the object to be sterilized by the cooling water. As described above, the heat sterilization apparatus according to the first aspect of the present invention includes a control unit that controls heat recovery of the medium-temperature water from the sterilization tank after heat sterilization, using medium-temperature water, generated separately from the high-temperature fluid, at a temperature higher than the cooling water but lower than the high-temperature fluid, before cooling the sterilization objects with cooling water. This allows heat recovery from the sterilization tank after heat sterilization using medium-temperature water, generated separately from the high-temperature fluid, to be prevented from decreasing in temperature. This prevents the time required to raise the high-temperature fluid to the sterilization temperature during the next heat sterilization after heat recovery. Furthermore, since the sterilization tank after heat sterilization is cooled with medium-temperature water, which has a higher temperature than the cooling water, before cooling the sterilization objects with cooling water, rapid temperature changes (sudden temperature drops) in the sterilization tank after heat sterilization are suppressed. Consequently, unlike in the case of repeated large expansion and contraction, the extent of expansion and contraction of the sterilization tank is reduced, thereby suppressing metal fatigue caused by thermal stress and reducing the durability (lifespan) of the sterilization tank. In the heat sterilization device of the first aspect, the control unit is preferably configured to perform medium-temperature water heat recovery control while the sterilization tank is discharging the high-temperature fluid after heat sterilization. This configuration allows heat recovery from the high-temperature fluid simply by discharging the high-temperature fluid. This eliminates the need for a dedicated heat exchanger or water supply tank for heat recovery from the high-temperature fluid, thus minimizing the need for larger devices that would otherwise require heat recovery from the high-temperature fluid. In the heat sterilization apparatus of the first aspect described above, it is preferred that the apparatus further include a medium-temperature water tank for storing medium-temperature water, and that the control unit be configured to use the medium-temperature water supplied from the medium-temperature water tank to perform medium-temperature water heat recovery control to recover heat from the sterilization tank after heat sterilization before cooling the sterilization object with cooling water, and that the medium-temperature water used for the medium-temperature water heat recovery control be stored in the medium-temperature water tank. With this configuration, storing the medium-temperature water in the medium-temperature water tank facilitates supplying the medium-temperature water to the sterilization tank after heat sterilization during heat recovery, and that the heat recovered by heat recovery be easily reused when the medium-temperature water used for heat recovery is stored in the medium-temperature water tank without being discharged. In this case, it is preferable that the control unit is configured to perform preheating control to preheat the sterilization tank using the medium-temperature water heated and stored in the medium-temperature water tank during the medium-temperature water heat recovery control before heating the sterilization object by the high-temperature fluid. With this configuration, the sterilization tank is preheated using the heated medium-temperature water used in the heat recovery, thereby increasing the initial temperature of the sterilization tank at the beginning of heat sterilization. Compared with the case where no preheating is performed, the amount of heat to be supplied to the high-temperature fluid when raising the temperature to the temperature for heat sterilization can be reduced. That is, by using medium-temperature water, the heat recovered by heat recovery can be effectively used for preheating. As a result, when preheating is performed, the thermal energy required in the heat sterilization device can be reduced, and accordingly, the amount of (high-temperature) steam used for heating the high-temperature water can be reduced. In a heat sterilization device configured to preheat the sterilization tank using medium-temperature water, the device preferably further includes a first connection path interconnecting the sterilization tank and the medium-temperature water tank. The control unit preferably controls the recovery of heat from the sterilization tank via the first connection path and its storage in the medium-temperature water tank, and controls the supply of medium-temperature water to the sterilization tank via the first connection path during preheating. This configuration facilitates the storage of heat-recovered medium-temperature water in the medium-temperature water tank using the first connection path and the supply of medium-temperature water from the medium-temperature water tank to the sterilization tank during preheating. In a heat sterilization device using medium-temperature water for preheating control of the sterilization tank, the control unit is preferably configured to control the discharge of medium-temperature water supplied from the medium-temperature water tank toward the sterilization target during preheating and heat recovery of the sterilization tank. With this configuration, during preheating of the sterilization tank, the discharged medium-temperature water contacts the sterilization target, causing the temperature of the medium-temperature water to decrease. This lowered medium-temperature water can be supplied to the sterilization tank, thereby suppressing abrupt temperature changes in the sterilization tank, which is at a low temperature during preheating. Furthermore, during heat recovery of the sterilization tank, the discharged medium-temperature water contacts the sterilization target, causing the temperature of the medium-temperature water to increase. This higher-temperature water can be supplied to the sterilization tank, thereby suppressing abrupt temperature changes in the sterilization tank, which is at a high temperature during heat recovery. This prevents a reduction in the durability of the sterilization tank caused by increased thermal stress resulting from rapid temperature changes during preheating and heat recovery of the sterilization tank. The heat sterilization device according to the first aspect is preferably further equipped with: a high-temperature water tank for recovering and storing high-temperature water, the high-temperature fluid stored in the sterilization tank after heat sterilization; and a second connecting path connecting the sterilization tank and the high-temperature water tank; and a control unit configured to control heat recovery of the medium-temperature water in the sterilization tank after heat sterilization of the sterilization object is completed and the high-temperature water discharged from the sterilization tank is recovered into the high-temperature water tank via the second connecting path. With this configuration, the high-temperature water in the sterilization tank is recovered via the dedicated second connecting path connecting the sterilization tank and the high-temperature water tank, thereby preventing heat from being lost from the high-temperature water after heat sterilization control, thereby suppressing a decrease in the temperature of the high-temperature water recovered in the high-temperature water tank. The heat sterilization device having the above-mentioned medium-temperature water tank preferably further comprises: a heat transfer fluid supply unit for supplying heat transfer fluid heated by medium-temperature water; and a heat exchanger for performing heat exchange between the medium-temperature water stored in the medium-temperature water tank and the heat transfer fluid supplied by the heat transfer fluid supply unit; and a control unit configured to control the supply of the heat transfer fluid, which has been heated by heat exchange with the medium-temperature water in the heat exchanger, to the sterilization tank during preheating of the sterilization tank, and to control the supply of the heat transfer fluid, which has been heated by heat exchange with the medium-temperature water in the heat exchanger, to the sterilization tank during heat recovery of the sterilization tank. With this configuration, the preheating temperature of the sterilization tank can be lowered compared to a case where medium-temperature water is directly supplied to the sterilization tank, thereby suppressing rapid temperature changes in the sterilization tank. The heat sterilization device according to the first aspect described above preferably further includes a circulation path comprising a circulation pump that discharges cooling water, high-temperature fluid, and medium-temperature water discharged from the sterilization tank and circulates them within the sterilization tank. The control unit is configured to utilize the circulation pump to circulate the medium-temperature water within the sterilization tank via the circulation path, thereby performing heat recovery control for the medium-temperature water. This configuration allows the circulation path used for both heat sterilization and cooling control to be commonly utilized for heat recovery control, thereby reducing the structural complexity and size of the heat sterilization device caused by an increase in the path length. The second aspect of the present invention is that the sterilization object is heat-sterilized by a heat sterilization device, and the heat sterilization device comprises: a sterilization tank having an accommodation space inside which accommodates the sterilization object to be heat-sterilized by a high-temperature fluid, and receiving a supply of the high-temperature fluid to heat-sterilize the sterilization object and cooling water to cool the sterilization object after heat sterilization by the high-temperature fluid; and a control unit for performing heat recovery control of the medium-temperature water to recover the heat of the sterilization tank after heat sterilization using medium-temperature water generated separately from the high-temperature fluid, the temperature of which is higher than the cooling water but lower than the high-temperature fluid, before cooling the sterilization object by the cooling water. In the second aspect of the present invention, as described above, the sterilization object is heat-sterilized by a heat sterilization apparatus equipped with a control unit. The control unit controls heat recovery by using intermediate-temperature water, which is higher than the cooling water but lower than the high-temperature fluid, to recover heat from the sterilization tank following heat sterilization, before cooling the sterilization object with cooling water. This allows the sterilization object to be heat-sterilized by the heat sterilization apparatus. Since the heat sterilization apparatus uses intermediate-temperature water, which is generated separately from the high-temperature fluid, to recover heat from the sterilization tank following heat sterilization, the temperature of the high-temperature fluid is prevented from decreasing. This prevents an increase in the time required to heat the high-temperature fluid to the sterilization temperature during the next heat sterilization after heat recovery. Furthermore, a decrease in the durability of the sterilization tank due to increased thermal stress caused by rapid temperature changes can be suppressed. The heat sterilization method of the third aspect of the present invention includes: a step of supplying a high-temperature fluid to a sterilization tank to be heat sterilized by the high-temperature fluid to heat sterilize the sterilization object in the sterilization tank; a step of recovering the heat of the sterilization tank after heat sterilization using medium-temperature water generated separately from the high-temperature fluid and having a temperature higher than the cooling water but lower than the high-temperature fluid before cooling the sterilization object by cooling water; and a step of cooling the sterilization object after heat sterilization by cooling water after heat recovery in the sterilization tank. As described above, the heat sterilization method according to the third aspect of the present invention includes a step of recovering heat from the sterilization tank after heat sterilization using intermediate-temperature water, which is hotter than the cooling water but cooler than the high-temperature fluid, before cooling the sterilization object with cooling water. This method, by using intermediate-temperature water generated separately from the high-temperature fluid to recover heat from the sterilization tank after heat sterilization, prevents the temperature of the high-temperature fluid from decreasing. Consequently, the provided heat sterilization method can prevent the time required to heat the high-temperature fluid to the sterilization temperature from being prolonged during the next heat sterilization after heat recovery. Furthermore, it can prevent a decrease in the durability of the sterilization tank caused by increased thermal stress due to rapid temperature changes. The heat sterilization method of the third aspect described above preferably further includes a step of preheating the sterilization tank using medium-temperature water heated during heat recovery in the sterilization tank before supplying the high-temperature fluid to the sterilization object to the sterilization tank. This configuration uses the heated medium-temperature water used in heat recovery to preheat the sterilization tank, thereby raising the initial temperature of the sterilization tank at the start of heat sterilization. This reduces the amount of heat required to raise the high-temperature fluid to the sterilization temperature compared to a situation where no preheating is performed. In other words, the use of medium-temperature water allows the heat recovered by heat recovery to be effectively utilized for preheating. As a result, the increase in thermal energy required by the heat sterilization device can be suppressed during preheating. 1: Sterilization tank 1a: Door for moving in and out 1b: Temperature sensor 1c: Water level sensor 1d: Containment Space 1e: Storage space 2: Spreading nozzle 2a: Injection port 3: High temperature water tank 3a: Temperature sensor 3b: Water level sensor 4:Medium temperature water tank 4a: Temperature sensor 4b: Water level sensor 5: Circular Path 5a: discharge pipe 5b: discharge pipe 5c: Upstream pipeline 5d: Downstream pipeline 5e: Temperature sensor 5f: Circulation pump 5g: Flow path switching valve 6: Supply path 6a: Shared pipeline 6b: Branch pipeline 6c: branch line 6d: Flow path switching valve 6e: Flow path switching valve 7: Discharge path 7a: Connecting pipes 7b: Flow path switching valve 8: Discharge path 8a: Connecting pipes 8b: Flow path switching valve 9: Supply Path 9a: Shared pipeline 9b: Connecting pipes 9c: Flow path switching valve 9d: Flow path switching valve 10: discharge path 10a: Shared pipeline 10b: Connecting pipes 10c: Flow path switching valve 10d: Flow path switching valve 10e: Steam dehumidifier 11: Heat exchanger 12: Control Department 100,500,600,700:Heating sterilization device 200: Cooling water source 301: Steam inlet 302: Steam exhaust pipe 401: Cooling water inlet 402: Cooling water outlet 503:High temperature water tank 512,612: Control Department 704:Medium temperature water tank 704c: Inflow pipe 704d: Supply pipeline 704e: Flow path switching valve 704f: Flow path switching valve 713: Heat transfer fluid supply unit 714:Heat exchanger Ci1: High temperature water preparation circulation circuit Ci2: Medium temperature water preparation circulation circuit Ci3: Medium temperature water circulation circuit Ci4: Heating and sterilization cycle Ci5: Heat recovery circuit Ci6: Cooling circuit Cw: Cooling water Htf: Heat Transfer Fluid Htm: Medium temperature water Hth: High temperature water Re1, Re3: Medium temperature water recovery line Re2: High temperature water recovery circuit Re4: Cooling water recovery line Rp: conditioning package S1, S2, S3, S4, S5: Steps Sp1, Sp3: Medium temperature water injection line Sp2: High temperature water injection line Sp4: Cooling water injection line Tch1, Tch2, Te1, Te2, Ti1, Ti2: Temperature changes Td1, Td2: temperature difference Tr: Tray Tst: heating sterilization temperature De,Di,TLag,Ue,Ui:Time Vah: Steam FIG1 is a schematic diagram showing a heat sterilization device according to this embodiment. FIG. 2 is a block diagram showing an overview of a preheating step for utilizing heat recovered by heat recovery for the next heat sterilization control during the heat sterilization control of the heat sterilization apparatus of this embodiment. FIG3 is a graph showing the relationship between the time of heat sterilization control and the temperature change of the sterilization tank in the heat sterilization apparatus of the embodiment. FIG. 4 is a graph showing the relationship between the time of heat sterilization control and the temperature change of the sterilization tank in the heat sterilization apparatus of the comparative example. FIG5 is a schematic diagram showing the preparation of high-temperature water before the loading step of the heat sterilization apparatus of this embodiment. FIG6 is a schematic diagram showing the preparation of warm water performed before the loading step of the heat sterilization apparatus of this embodiment. FIG. 7 is a schematic diagram showing a loading step in the heat sterilization control of the heat sterilization apparatus according to the present embodiment. FIG8 is a schematic diagram showing the medium-temperature water injection step of the preheating step in the heat sterilization control of the heat sterilization apparatus of this embodiment, which shows the medium-temperature water injection step following the carrying-in step shown in FIG7 . 9 is a schematic diagram showing a medium-temperature water circulation step of a preheating step in the heat sterilization control of the heat sterilization apparatus of this embodiment, which shows the medium-temperature water circulation step following the medium-temperature water injection step shown in FIG. 8 . FIG10 is a schematic diagram showing a medium-temperature water recovery step in a preheating step in the heat sterilization control of the heat sterilization apparatus according to this embodiment, which shows the medium-temperature water recovery step following the medium-temperature water circulation step shown in FIG9 . 11 is a schematic diagram showing a high-temperature water injection step of the object heating step in the heat sterilization control of the heat sterilization apparatus of this embodiment, which shows the high-temperature water injection step following the medium-temperature water recovery step shown in FIG. 10 . FIG12 is a schematic diagram showing a temperature rising step and a heat sterilization step of an object heating step in the heat sterilization control of the heat sterilization apparatus of this embodiment, showing the temperature rising step following the high-temperature water injection step shown in FIG11 . Figure 13 is a schematic diagram showing the step of recovering high-temperature water to a high-temperature water tank for heat recovery in the high-temperature water heat recovery step in the heat sterilization control of the heat sterilization device of this embodiment, which shows the high-temperature water heat recovery step following the temperature increase step shown in Figure 12. 14 is a schematic diagram showing a medium-temperature water injection step of a medium-temperature water heat recovery step in the heat sterilization control of the heat sterilization apparatus of this embodiment, which shows the medium-temperature water injection step following the high-temperature water heat recovery step shown in FIG. 13 . 15 is a schematic diagram showing a medium-temperature water circulation step of a medium-temperature water heat recovery step in the heat sterilization control of the heat sterilization apparatus of this embodiment, which shows the medium-temperature water circulation step following the medium-temperature water injection step shown in FIG. 14 . 16 is a schematic diagram showing a medium-temperature water recovery step of a medium-temperature water heat recovery step in the heat sterilization control of the heat sterilization apparatus of this embodiment, which shows the medium-temperature water recovery step following the medium-temperature water circulation step shown in FIG. 15 . FIG17 is a schematic diagram showing a cooling water injection step of the object cooling step in the heat sterilization control of the heat sterilization apparatus of this embodiment, which shows the cooling water injection step following the medium-temperature water recovery step shown in FIG16 . FIG. 18 is a schematic diagram showing a cooling step of the object cooling step in the heat sterilization control of the heat sterilization apparatus according to this embodiment, and shows the cooling step following the cooling water injection step shown in FIG. 17 . FIG19 is a schematic diagram showing a cooling water recovery step of the object cooling step in the heat sterilization control of the heat sterilization apparatus according to this embodiment, and shows the cooling water recovery step following the cooling step shown in FIG18 . FIG. 20 is a schematic diagram showing a carry-out step in the heat sterilization control of the heat sterilization apparatus according to the present embodiment. FIG. 21 is a diagram comparing a graph of heat sterilization control performed by a heat sterilization apparatus of a comparative example and a graph of heat sterilization control performed by a heat sterilization apparatus of this embodiment. FIG. 22 is a flow chart showing a heat sterilization method performed by the heat sterilization apparatus of this embodiment. FIG. 23 is a schematic diagram showing a state of an object heating step of a hot water storage type heating sterilization apparatus according to a first modified example of the present embodiment. FIG. 24 is a schematic diagram showing a state of an object heating step of a steam-type heat sterilizer according to a second modified example of the present embodiment. FIG25 is a schematic diagram showing a heat sterilization apparatus according to a third modified example of the present embodiment. The following describes embodiments of the present invention with reference to the drawings. 1 to 22 , the structure of a heat sterilization apparatus 100 according to this embodiment will be described. (Heating sterilization device) As shown in FIG1 , the heat sterilization device 100 of this embodiment is a distributed device that heats a food-enclosed food pack Rp using high-temperature water Hth, thereby sterilizing the food and the pack Rp. The food-enclosed food pack Rp is an example of a "sterilization target" within the scope of the patent application, and the high-temperature water Hth is an example of a "high-temperature fluid" within the scope of the patent application. As shown in Figure 1, the heating sterilization device 100 of this embodiment includes a sterilization tank 1, a spreading nozzle 2, a high-temperature water tank 3, a medium-temperature water tank 4, a circulation path 5, a supply path 6, a discharge path 7, a discharge path 8, a supply path 9, a discharge path 10, a heat exchanger 11 and a control unit 12. (Sterilization tank) The sterilization tank 1 is a sealed container that sterilizes the prepared food packets Rp by heating them with high-temperature water Hth and cools them with cooling water Cw. Furthermore, medium-temperature water Htm is supplied to the sterilization tank 1 for various processes, including preheating and heat recovery of the prepared food packets Rp. The medium-temperature water Htm is generated separately from the high-temperature water Hth and has a temperature higher than the cooling water Cw but lower than the high-temperature water Hth. Preheating and heat recovery using the medium-temperature water Htm will be described in detail later. The sterilization tank 1 includes a loading and unloading door 1a, a temperature sensor 1b, a water level sensor 1c, a storage space 1d, and a reservoir space 1e. The loading and unloading door 1a is opened and closed by the user when the tray Tr carrying a plurality of conditioning packets Rp is loaded into the sterilization tank 1 in a stacked state and when it is loaded out of the sterilization tank 1. The temperature sensor 1b is used to measure the temperature inside the sterilization tank 1. The water level sensor 1c is used to measure the water levels of the high-temperature water Hth, medium-temperature water Htm, and cooling water Cw stored in the storage space 1e. The storage space 1d is used to store the conditioning packets Rp to be heat-sterilized by the high-temperature water Hth. The storage space 1e is used to store the high-temperature water Hth, medium-temperature water Htm, and cooling water Cw during preheating, heat sterilization, heat recovery, and cooling, respectively. The storage space 1e is located in the storage space 1d, at the lower side of the tray Tr on the bottom layer among the plurality of stacked trays Tr. (Dispersing nozzle) The dispensing nozzle 2 in the dispensing heat sterilizer 100 of this embodiment is configured to discharge high-temperature water Hth, medium-temperature water Htm, and cooling water Cw into the sterilization tank 1. The dispensing nozzle 2 includes a plurality of nozzles 2a. Each nozzle 2a is positioned to align with a plurality of stacked trays Tr. This allows the high-temperature water Hth, medium-temperature water Htm, and cooling water Cw discharged from the dispensing nozzle 2 to be directed toward the prepared packets Rp placed on the trays Tr. Multiple dispensing nozzles 2 of this configuration are disposed within the sterilization tank 1. (high temperature water tank) As shown in Figure 1, the high-temperature water tank 3 recovers and stores the high-temperature water Hth, the high-temperature fluid that has been heat-sterilized and stored in the sterilization tank 1. The hot water storage space within the high-temperature water tank 3 can store the high-temperature water Hth, which is the combined capacity of the storage space 1e, the circulation path 5, and the supply path 6. The high-temperature water tank 3 includes a temperature sensor 3a and a water level sensor 3b. The temperature sensor 3a measures the temperature within the high-temperature water tank 3. The water level sensor 3b measures the level of the high-temperature water Hth stored in the hot water storage space. (Medium temperature water tank) Here, the medium-temperature water tank 4 of this embodiment recovers and stores the preheated and heat-recovered medium-temperature water Htm stored in the sterilization tank 1. The medium-temperature water storage space of the medium-temperature water tank 4 can store a volume of medium-temperature water Htm equal to the combined capacity of the storage space 1e, the circulation path 5, and the supply path 6. As shown in Figure 1, the medium-temperature water tank 4 includes a temperature sensor 4a and a water level sensor 4b. The temperature sensor 4a measures the temperature within the medium-temperature water tank 4. The water level sensor 4b measures the level of the medium-temperature water Htm stored in the medium-temperature water storage space. (Circular Path) As shown in Figure 1, the circulation path 5 returns the cooling water Cw, high-temperature water Hth, and medium-temperature water Htm discharged from the sterilization tank 1 to the sterilization tank 1 via the heat exchanger 11. The circulation path 5 includes a discharge line 5a, a discharge line 5b, an upstream line 5c, a downstream line 5d, a temperature sensor 5e, a circulation pump 5f, and a flow path switching valve 5g. The discharge pipe 5a and the discharge pipe 5b respectively discharge the cooling water Cw, high-temperature water Hth, and medium-temperature water Htm stored in the storage space 1e. The upstream pipe 5c is connected to the heat exchanger 11, the discharge pipe 5a, and the discharge pipe 5b. The downstream pipe 5d is connected to the heat exchanger 11 and the sterilization tank 1. The circulation pump 5f discharges the cooling water Cw, high-temperature water Hth, and medium-temperature water Htm discharged from the sterilization tank 1 and circulates them within the sterilization tank 1. The circulation pump 5f also returns the high-temperature water Hth discharged from the sterilization tank 1 to the high-temperature water tank 3. Furthermore, the circulation pump 5f returns the medium-temperature water Htm discharged from the sterilization tank 1 to the medium-temperature water tank 4. The flow path switching valve 5g is used to switch the flow paths of the cooling water Cw, high-temperature water Hth, and medium-temperature water Htm. (Supply path) The supply path 6 branches off from the circulation path 5 to supply high-temperature water Hth to the high-temperature water tank 3. The supply path 6 also branches off from the circulation path 5 to supply medium-temperature water Htm to the medium-temperature water tank 4. The supply path 6 includes a common pipe 6a, a branch pipe 6b, a branch pipe 6c, a flow path switching valve 6d, and a flow path switching valve 6e. The common pipe 6a is connected to the circulation path 5 and is shared by the high-temperature water tank 3 and the medium-temperature water tank 4. The branch pipe 6b branches off from the common pipe 6a and is connected to the high-temperature water tank 3. The branch pipe 6c branches off from the common pipe 6a and is connected to the medium-temperature water tank 4. (Discharge path) The discharge path 7 connects the high-temperature water tank 3 and the discharge path 8 so that the high-temperature water Hth in the high-temperature water tank 3 flows into the circulation path 5. The discharge path 7 includes a connecting pipe 7a and a flow path switching valve 7b. The discharge path 8 connects the medium-temperature water tank 4 and the circulation path 5 so that the medium-temperature water Htm in the medium-temperature water tank 4 flows into the circulation path 5. The discharge path 8 includes a connecting pipe 8a and a flow path switching valve 8b. Here, the circulation path 5, the common pipe 6a and branch pipe 6c of the supply path 6, and the connecting pipe 8a of the discharge path 8 are examples of the "first connecting path" for the purposes of the claimed invention, connecting the sterilization tank 1 and the medium-temperature water tank 4. Furthermore, the circulation path 5, the common pipe 6a and branch pipe 6c of the supply path 6, and the connecting pipe 8a of the discharge path 8 are examples of the "second connecting path" for the purposes of the claimed invention, connecting the sterilization tank 1 and the high-temperature water tank 3. Furthermore, cooling water Cw supplied from a cooling water source 200 installed in the factory where the heat sterilization apparatus 100 is installed flows into the circulation path 5. Cooling water Cw is also supplied to the portion of the upstream pipe 5c further upstream of the circulation pump 5f. (Supply path) The supply path 9 connects the steam inlet 301 of the boiler equipment installed in the factory where the heat sterilization apparatus 100 is installed and the cooling water inlet 401 of the cooling water source to the heat exchanger 11. The supply path 9 includes a common pipe 9a, a connecting pipe 9b, a flow path switching valve 9c, and a flow path switching valve 9d. (Discharge path) Discharge path 10 connects the steam exhaust pipe 302 and cooling water outlet 402, both installed in the factory where the sterilization apparatus 100 is installed, to the heat exchanger 11. Discharge path 10 includes a common pipe 10a, a connecting pipe 10b, a flow switching valve 10c, a flow switching valve 10d, and a steam dehumidifier 10e. (Heat Exchanger) As shown in Figure 1, the heat exchanger 11 causes the cooling water Cw and high-temperature water Hth flowing in the circulation path 5 to exchange heat with the steam flowing into the steam inlet 301, thereby heating the cooling water Cw and high-temperature water Hth. In addition, the heat exchanger 11 causes the cooling water Cw flowing in the circulation path 5 to exchange heat with the cooling water flowing into the cooling water inlet 401, thereby cooling the cooling water Cw. (Control Department) The control unit 12 is configured to control the heat sterilization apparatus 100. The control unit 12 includes a central processing unit (CPU), a memory unit such as a solid state disk (SSD) or hard disk drive (HDD), and memory devices such as read-only memory (ROM) and random access memory (RAM). The memory unit stores a heat sterilization program. This heat sterilization program controls the loading and unloading of prepared packets Rp within the heat sterilization apparatus 100, as well as the heat sterilization, cooling, preheating, and heat recovery of the prepared packets Rp. The control unit 12 is electrically connected to each of the temperature sensor 1b, the water level sensor 1c, the temperature sensor 3a, the water level sensor 3b, the temperature sensor 4a, the water level sensor 4b, the temperature sensor 5e, the circulation pump 5f, the flow switching valve 5g, the flow switching valve 6d, the flow switching valve 6e, the flow switching valve 7b, the flow switching valve 8b, the flow switching valve 9c, the flow switching valve 9d, the flow switching valve 10c, and the flow switching valve 10d. Furthermore, the control unit 12 is electrically connected not only to the aforementioned sensors but also to flow measurement sensors, pressure sensors, and the like. The control unit 12 controls the loading and unloading of the prepared packets Rp and the heating, sterilization, cooling, and heat recovery of the prepared packets Rp based on necessary measurement information from various sensors. (Overview of Operation Control of the Heat Sterilizer of the Present Embodiment) First, an overview (concept) of the operation control (hereinafter referred to as "heat sterilization control") of the heat sterilization apparatus 100 according to this embodiment will be described with reference to FIG. 2 . As shown in Figure 2, the heat sterilization control system of this embodiment includes a series of processes, including a preheating step, an object heating step, a high-temperature water heat recovery step, a medium-temperature water heat recovery step, and an object cooling step. The heat sterilization control system of this embodiment can reduce the total amount of thermal energy required when performing multiple heat sterilization processes including a series of processes. Specifically, a preheating step is performed before the object heating step, heating the low-temperature retort 1 and the preparation packet Rp (the object to be sterilized). This preheating step reduces the amount of heat absorbed by the retort 1 from the high-temperature water Hth during the object heating step, making it easier for the high-temperature water Hth to heat the preparation packet Rp to the sterilization temperature Tst for heat sterilization. As shown in FIG2 , in the heat sterilization control of this embodiment, the medium-temperature water heat recovery step recovers heat from the high-temperature retort 1 and the preparation package Rp (sterilization target) after heat sterilization in the first heat sterilization control, thereby raising the temperature of the medium-temperature water Htm (to 90° C.). The raised medium-temperature water Htm is then used for preheating in the second heat sterilization control, thereby lowering the temperature of the medium-temperature water Htm from 90° C. to 50° C. Furthermore, the heat recovery is repeated in the same manner from the second heat sterilization control onwards, with the heat recovered in the second heat sterilization control being used for preheating in the third heat sterilization control. In this way, the thermal energy required for preheating can be obtained from the heat of the high-temperature sterilization tank 1 and the conditioning package Rp (sterilization object) that would have been discharged through the cooling water Cw in the object cooling step, thereby reducing the total amount of thermal energy required for multiple heating sterilization controls including a series of treatments. (Details of Heat Sterilization Control in This Embodiment) 3 to 22 , details of the heat sterilization control including the preheating step and the medium-temperature water heat recovery step of this embodiment will be described. As shown in FIG3 , the heat sterilization control system of this embodiment sequentially performs a loading step, a preheating step (preheating control), an object heating step (sterilization object heat sterilization control), a high-temperature water heat recovery step (high-temperature water heat recovery control), a medium-temperature water heat recovery step (medium-temperature water heat recovery control), an object cooling step (sterilization object cooling control), and a loading step. The preheating step includes a medium-temperature water injection step, a medium-temperature water circulation step, and a medium-temperature water recovery step. The object heating step includes a high-temperature water injection step, a temperature increase step, and a heat sterilization step. The medium-temperature water heat recovery step includes a medium-temperature water injection step, a medium-temperature water circulation step, and a medium-temperature water recovery step. The object cooling step includes a cooling water injection step, a cooling step, and a cooling water recovery step. In contrast to the heat sterilization control of this embodiment, which includes the above-described steps, the heat sterilization control of the comparative example (equivalent to the conventional example) shown in FIG4 performs controls related to the steps of loading and unloading the prepared packets, as well as the heat sterilization step, the high-temperature water heat recovery step, and the cooling step of the prepared packets. Specifically, the heat sterilization apparatus performing the heat sterilization control of this comparative example lacks a medium-temperature tank for storing medium-temperature water and does not perform preheating and heat recovery using the medium-temperature water. Thus, among the aforementioned multiple steps of the heat sterilization control of this embodiment, the preheating step and the medium-temperature water heat recovery step are different structures not included in the heat sterilization control of the comparative example, which will be described in detail below. (Preparation of high temperature water) First, as shown in FIG5 , prior to the loading step, high-temperature water Hth is prepared. Specifically, the controller 12 controls the flow switching valves 5g, 6e, and 8b to close, and the flow switching valves 6d and 7b to open, thereby forming a high-temperature water preparation circulation path Ci1. Furthermore, the controller 12 uses the circulation pump 5f to circulate cooling water Cw supplied from the cooling water source 200 through the high-temperature water preparation circulation path Ci1. Simultaneously, the circulating cooling water Cw is heated by heat exchange with steam in the heat exchanger 11, thereby preparing high-temperature water Hth. The high-temperature water preparation circulation path Ci1 includes an upstream pipe 5c, a downstream pipe 5d, a common pipe 6a, a branch pipe 6b, a connecting pipe 7a, and a connecting pipe 8a. Within the high-temperature water preparation circulation path Ci1, the cooling water Cw flows in the order of the connecting pipe 7a, the connecting pipe 8a, the upstream pipe 5c, the downstream pipe 5d, the common pipe 6a, and the branch pipe 6b. (Preparation of medium-temperature water) Furthermore, as shown in FIG6 , before the carrying-in step, preliminary preparation of the medium-temperature water Htm is performed. Specifically, after preparing high-temperature water Hth, the controller 12 controls the flow switching valves 5g, 6d, and 7b to close, and the flow switching valves 6e and 8b to open, thereby forming a medium-temperature water preparation circulation path Ci2. Furthermore, the controller 12 uses the circulation pump 5f to circulate cooling water Cw supplied from the cooling water source 200 through the medium-temperature water preparation circulation path Ci2. Simultaneously, the circulating cooling water Cw is heated by heat exchange with steam in the heat exchanger 11, thereby preparing medium-temperature water Htm at a medium temperature (approximately 90°C). The medium-temperature water preparation circulation path Ci2 includes an upstream pipe 5c, a downstream pipe 5d, a common pipe 6a, a branch pipe 6c, and a connecting pipe 8a. In the intermediate-temperature water preparation circulation path Ci2, the cooling water Cw flows in the order of the connecting pipe 8a, the upstream pipe 5c, the downstream pipe 5d, the common pipe 6a, and the branch pipe 6c. (Moving in steps) As shown in Fig. 7, after the medium temperature water Htm and the high temperature water Hth are prepared, the loading step is performed. In the loading step, the trays Tr carrying the plurality of conditioning packets Rp are loaded in a stacked state into the sterilization tank 1 according to the user's operation. (Preheating step) As shown in FIG8 , the control unit 12 preheats the retort 1 and the retort Rp using medium-temperature water Htm supplied from the medium-temperature water tank 4 before heat-sterilizing the retort Rp with the high-temperature water Hth. This preheating of the retort 1 with the medium-temperature water Htm before the high-temperature water Hth is injected into the retort 1 can suppress abrupt temperature changes Tch1 in the retort 1 (see the comparative example in FIG4 ). Specifically, the control unit 12 controls the flow path switching valve 6d and the flow path switching valve 7b to be closed, and controls the flow path switching valve 5g and the flow path switching valve 8b to be open, thereby forming the medium-temperature water injection path Sp1. Furthermore, the control unit 12 uses the circulation pump 5f to inject the medium-temperature water Htm in the medium-temperature water tank 4 into the sterilization tank 1 via the medium-temperature water injection path Sp1 (medium-temperature water injection step (see Figure 3)). Here, the medium-temperature water injection path Sp1 includes an upstream pipe 5c, a downstream pipe 5d, and a connecting pipe 8a. In the medium-temperature water injection path Sp1, the medium-temperature water Htm flows in the connecting pipe 8a, the upstream pipe 5c, and the downstream pipe 5d in this order. In this manner, the control unit 12 supplies the medium-temperature water Htm to the sterilization tank 1 via the upstream pipe 5c, the downstream pipe 5d, and the connecting pipe 8a during preheating. As shown in Figure 9 , after injecting the medium-temperature water Htm, the controller 12 controls the flow switching valves 6d, 6e, 7b, and 8b to close, and controls the flow switching valve 5g to open, thereby forming the medium-temperature water circulation path Ci3. Furthermore, the controller 12 uses the circulation pump 5f to circulate the medium-temperature water Htm through the sterilization tank 1 via the medium-temperature water circulation path Ci3 without undergoing heat exchange in the heat exchanger 11, thereby performing preheating control (medium-temperature water circulation step (see Figure 3)). The medium-temperature water circulation path Ci3 includes a circulation path 5 (discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d). Within the medium-temperature water circulation path Ci3, the medium-temperature water Htm flows in the order of the discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d. During the preheating process of retort 1, control unit 12 causes medium-temperature water Htm supplied from medium-temperature water tank 4 to be discharged toward preparation pack Rp. During the preheating process, the temperature of medium-temperature water Htm decreases to the post-preheating temperature (approximately 50°C) due to heat transfer to retort 1 and preparation pack Rp. As shown in FIG. 10 , the control unit 12 circulates the medium-temperature water Htm for a predetermined period of time, and then recovers the preheated medium-temperature water Htm in the sterilization tank 1 through the medium-temperature water recovery path Re1 and stores it in the medium-temperature water tank 4 . Specifically, after circulating the medium-temperature water Htm for a predetermined period of time, the control unit 12 controls the flow path switching valves 5g, 6d, 7b, and 8b to close, and controls the flow path switching valve 6e to open, thereby forming the medium-temperature water recovery path Re1. Furthermore, the control unit 12 controls the recovery of the medium-temperature water Htm by using the circulation pump 5f to recover the medium-temperature water Htm via the medium-temperature water recovery path Re1 to the medium-temperature water tank 4 (medium-temperature water recovery step (see FIG. 3 )). The medium-temperature water recovery path Re1 includes a discharge line 5a, a discharge line 5b, an upstream line 5c, a downstream line 5d, a common line 6a, and a branch line 6c. In the medium-temperature water recovery path Re1, the medium-temperature water Htm flows in the order of the discharge line 5a, the discharge line 5b, the upstream line 5c, the downstream line 5d, the common line 6a, and the branch line 6c. After the medium-temperature water Htm in the sterilization tank 1 is recovered via the medium-temperature water recovery path Re1 into the medium-temperature water tank 4, the control unit 12 performs the step of heating the object in the conditioning pack Rp. At this time, the water level sensor 1c confirms that the medium-temperature water Htm has been discharged from the sterilization tank 1, thereby preventing the temperature of the high-temperature water Hth from falling below the medium-temperature water Htm. (Object Heating Step) As shown in FIG. 11 and FIG. 12 , the control unit 12 preheats the seasoning pack Rp with the medium-temperature water Htm and then heat-sterilizes the seasoning pack Rp using the high-temperature water Hth supplied from the high-temperature water tank 3 . Specifically, as shown in Figure 11, the control unit 12 controls the flow switching valves 6d, 6e, and 8b to close, and controls the flow switching valves 5g and 7b to open, thereby forming a high-temperature water injection path Sp2. Furthermore, the control unit 12 controls the circulation pump 5f to inject the high-temperature water Hth within the high-temperature water tank 3 into the sterilization tank 1 via the high-temperature water injection path Sp2. Here, the high-temperature water injection path Sp2 includes an upstream conduit 5c, a downstream conduit 5d, a connecting conduit 7a, and a connecting conduit 8a. In the high-temperature water injection path Sp2, the high-temperature water Hth flows in the order of the connecting conduit 7a, the connecting conduit 8a, the upstream conduit 5e, and the downstream conduit 5d. As shown in Figure 12 , after high-temperature water Hth is injected, the controller 12 controls the flow switching valves 6d, 6e, 7b, and 8b to close, and controls the flow switching valve 5g to open, thereby forming a heating and sterilization circulation path Ci4. Furthermore, the controller 12 uses the circulation pump 5f to circulate the high-temperature water Hth through the heating and sterilization circulation path Ci4 within the sterilization tank 1. Simultaneously, the high-temperature water Hth exchanges heat with steam in the heat exchanger 11, raising its temperature to the sterilization temperature Tst (e.g., slightly above 120°C), thereby controlling the temperature increase (temperature increase step (see Figure 3)). The heating and sterilization circulation path Ci4 includes a circulation path 5 (discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d). In the heating and sterilization circuit Ci4, high-temperature water Hth flows sequentially through discharge pipes 5a and 5b, upstream pipe 5c, and downstream pipe 5d. The sterilization temperature Tst being slightly above 120°C is merely an example; the situation may vary depending on the type of object being sterilized. Furthermore, after the high-temperature water Hth is heated to the heating and sterilization temperature Tst, the control unit 12 circulates the high-temperature water Hth in the sterilization tank 1 through the heating and heating and sterilization circulation path Ci4 by means of the circulation pump 5f, and at the same time exchanges heat with the steam in the heat exchanger 11 to maintain the high-temperature water Hth at the heating and sterilization temperature Tst, thereby performing heating and sterilization control (heating and sterilization step). (High-temperature water heat recovery step) As shown in FIG13 , after heat sterilization with high-temperature water Hth for a predetermined period of time, the control unit 12 recovers the sterilized high-temperature water Hth in the sterilization tank 1 via the high-temperature water recovery path Re2 and stores it in the high-temperature water tank 3. The high-temperature water heat recovery step recovers the high-temperature water Hth, maintained at the temperature after heat sterilization, into the high-temperature water tank 3. Specifically, after heat sterilization with high-temperature water Hth for a predetermined period of time, the control unit 12 controls the flow path switching valves 5g, 6e, 7b, and 8b to close, and controls the flow path switching valve 6d to open, thereby forming a high-temperature water recovery path Re2. Furthermore, the control unit 12 controls the high-temperature water Hth by having the circulation pump 5f recover it via the high-temperature water recovery path Re2 to the high-temperature water tank 3 (high-temperature water heat recovery step (see FIG. 3 )). The high-temperature water recovery path Re2 includes a discharge line 5a, a discharge line 5b, an upstream line 5c, a downstream line 5d, a common line 6a, and a branch line 6b. In the high-temperature water recovery path Re2, the high-temperature water Hth flows in the order of the discharge line 5a, the discharge line 5b, the upstream line 5c, the downstream line 5d, the common line 6a, and the branch line 6b. Furthermore, after the high-temperature water Hth discharged from the sterilization tank 1 is recovered into the high-temperature water tank 3 via the high-temperature water recovery line Re2, the control unit 12 performs the medium-temperature water heat recovery step for the sterilization tank 1 and the preparation pack Rp. Specifically, the control unit 12 performs the medium-temperature water heat recovery step after the high-temperature water Hth, which has undergone heat sterilization, has been discharged from the sterilization tank 1. At this time, the water level sensor 1c confirms that the high-temperature water Hth has been discharged from the sterilization tank 1, thereby suppressing the temperature increase of the medium-temperature water Htm caused by the high-temperature water Hth. (Medium-temperature water heat recovery step) As shown in Figures 14 to 16 , the controller 12 uses the medium-temperature water Htm supplied from the medium-temperature water tank 4 to recover heat from the retort 1 and the retort Rp before the cooling water Cw is used to cool the retort Rp, thereby performing a medium-temperature water heat recovery step. This recovery of heat from the retort 1 using the medium-temperature water Htm before the cooling water Cw is injected into the retort 1 can suppress a sudden temperature change Tch2 in the retort 1 (see the comparative example in Figure 4 ). Specifically, as shown in Figure 14 , the control unit 12 controls the flow switching valves 6d, 7b, and 6e to close, and controls the flow switching valves 5g and 8b to open, thereby forming a medium-temperature water injection path Sp3. Furthermore, the control unit 12 uses the circulation pump 5f to inject the medium-temperature water Htm within the medium-temperature water tank 4 into the sterilization tank 1 via the medium-temperature water injection path Sp3 (medium-temperature water injection step (see Figure 3)). Here, the medium-temperature water injection path Sp3 includes an upstream conduit 5c, a downstream conduit 5d, and a connecting conduit 8a. In the medium-temperature water injection path Sp3, the medium-temperature water Htm flows in the connecting conduit 8a, the upstream conduit 5c, and the downstream conduit 5d, in that order. As shown in Figure 15 , after the medium-temperature water Htm is injected, the controller 12 controls the flow path switching valves 6d, 6e, 7b, and 8b to close, and controls the flow path switching valve 5g to open, thereby forming a heat recovery circuit Ci5. Furthermore, the controller 12 controls the medium-temperature water Htm by causing it to circulate through the sterilization tank 1 via the heat recovery circuit Ci5 via the circulation pump 5f without undergoing heat exchange in the heat exchanger 11, thereby performing heat recovery control for the medium-temperature water (medium-temperature water circulation step (see Figure 3)). The heat recovery circuit Ci5 includes a circulation path 5 (discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d). In the heat recovery circuit Ci5, the medium-temperature water Htm flows in the order of the discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d. During this heat recovery process in retort 1, controller 12 directs medium-temperature water Htm supplied from medium-temperature water tank 4 toward preparation pack Rp. During this medium-temperature water circulation step, the temperature of medium-temperature water Htm rises to the post-heat recovery temperature (approximately 90°C) due to heat from both retort 1 and preparation pack Rp. As shown in FIG. 16 , the control unit 12 circulates the medium-temperature water Htm for a predetermined period of time, and then recovers the heat-recovered medium-temperature water Htm in the sterilization tank 1 through the medium-temperature water recovery path Re3 and stores the recovered heat in the medium-temperature water tank 4 . Specifically, after circulating the medium-temperature water Htm for a predetermined period of time, the control unit 12 controls the flow path switching valves 5g, 6d, 7b, and 8b to close, and controls the flow path switching valve 6e to open, thereby forming the medium-temperature water recovery path Re3. Furthermore, the control unit 12 controls the recovery of the medium-temperature water Htm by using the circulation pump 5f to recover the medium-temperature water Htm via the medium-temperature water recovery path Re3 to the medium-temperature water tank 4 (medium-temperature water recovery step (see FIG. 3 )). The medium-temperature water recovery path Re3 includes a discharge line 5a, a discharge line 5b, an upstream line 5c, a downstream line 5d, a common line 6a, and a branch line 6c. In the medium-temperature water recovery path Re3, the medium-temperature water Htm flows in the order of the discharge line 5a, the discharge line 5b, the upstream line 5c, the downstream line 5d, the common line 6a, and the branch line 6c. Thus, before the object cooling step of the conditioning package Rp is performed using cooling water Cw, the control unit 12 uses the medium-temperature water Htm supplied from the medium-temperature water tank 4 to recover heat from the sterilization tank 1 after heat sterilization, thereby performing the medium-temperature water heat recovery step. Furthermore, the medium-temperature water Htm used in the medium-temperature water heat recovery step is stored in the medium-temperature water tank 4. Specifically, the control unit 12 recovers the medium-temperature water Htm in the sterilization tank 1 after heat recovery via the discharge pipe 5a, the discharge pipe 5b, the upstream pipe 5c, the downstream pipe 5d, the common pipe 6a, and the branch pipe 6c, and stores it in the medium-temperature water tank 4. In addition, the control unit 12 performs a cooling step for the conditioning package Rp after the medium-temperature water Htm in the sterilization tank 1 is recovered into the medium-temperature water tank 4 via the medium-temperature water recovery path Re3. At this time, the water level sensor 1c confirms that the medium-temperature water Htm has been discharged from the sterilization tank 1, and the temperature of the cooling water Cw can be suppressed from rising due to the medium-temperature water Htm. (Object Cooling Step) As shown in FIG. 17 to FIG. 19 , after the control unit 12 recovers heat from the conditioning pack Rp using the medium-temperature water Htm, it uses the cooling water Cw supplied from the cooling water source 200 (see FIG. 1 ) to cool the conditioning pack Rp and the sterilization tank 1 to perform a cooling step. Specifically, as shown in Figure 17 , the control unit 12 controls the flow switching valves 6d, 6e, 7b, and 8b to close, and controls the flow switching valve 5g to open, thereby forming a cooling water injection path Sp4. Furthermore, the control unit 12 uses the circulation pump 5f to inject cooling water Cw supplied from the cooling water source 200 into the sterilization tank 1 via the cooling water injection path Sp4 (cooling water injection step (see Figure 3)). Here, the cooling water injection path Sp4 includes a circulation path 5 (discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d). In the cooling water injection path Sp4, the cooling water Cw flows in the order of upstream line 5c, downstream line 5d, discharge line 5a, and discharge line 5b. As shown in Figure 18, after the cooling water Cw is injected, the controller 12 controls the flow switching valves 6d, 6e, 7b, and 8b to close, and controls the flow switching valve 5g to open, thereby forming a cooling circulation path Ci6. Furthermore, the controller 12 uses the circulation pump 5f to circulate the cooling water Cw through the retort 1 via the cooling circulation path Ci6. Simultaneously, the cooling water Cw exchanges heat with the cooling water in the heat exchanger 11, absorbing heat from the preparation package Rp and the retort 1, and cooling the heated cooling water Cw, thereby performing cooling control (cooling step (see Figure 3)). Here, the cooling circulation path Ci6 includes a circulation path 5 (discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d). In the cooling circulation path Ci6, the cooling water Cw flows in the order of the discharge line 5a, discharge line 5b, upstream line 5c, and downstream line 5d. As shown in Figure 19, after cooling the sterilizer 1 with cooling water Cw for a predetermined period of time, the controller 12 uses the circulation pump 5f to recover the cooled cooling water Cw within the sterilizer 1 through the cooling water recovery path Re4 (cooling water recovery step). The cooling water recovery path Re4 includes a discharge line 5a, a discharge line 5b, and an upstream line 5c. In the cooling water recovery path Re4, the cooling water Cw flows through the discharge line 5a, the discharge line 5b, and the upstream line 5c in that order. (Moving out steps) As shown in FIG. 20 , in the unloading step, the user unloads the cooled plurality of conditioning packets Rp from the sterilization tank 1 . Next, the next heating and sterilization control of the plurality of conditioning packages Rp is performed. At this time, the control unit 12 performs a preheating step of preheating the sterilization tank 1 using the medium-temperature water Htm heated in the medium-temperature water heat recovery step (medium-temperature water heat recovery control) and accumulated in the medium-temperature water tank 4 before heating the conditioning packages Rp with the high-temperature water Hth. Thus, in the heating and sterilization control of this embodiment, since the heat absorbed from the conditioning packages Rp and the sterilization tank 1 in the medium-temperature water heat recovery step is utilized, the occurrence of heat loss can be suppressed. Moreover, since only a slight reheating (for example, about 1 to 2°C) is required during the preliminary preparation of the medium-temperature water Htm shown in FIG6 , the heat required for heating the medium-temperature water Htm and the time required for heating the medium-temperature water Htm after the initial heating and sterilization control can be suppressed. This heat sterilization control is performed multiple times a day. The medium-temperature water Htm stored in the medium-temperature water tank 4 is reused and then drained from the medium-temperature water tank 4. Furthermore, new medium-temperature water Htm is stored in the medium-temperature water tank 4 (see Figure 6). The user can set the timing for replacing the medium-temperature water Htm as appropriate, for example, daily or every few days. This reduces the increase in water usage caused by the use of medium-temperature water Htm, compared to preparing medium-temperature water Htm for each heating control. (Comparison between the Heat Sterilization Control of the Comparative Example and the Heat Sterilization Control of the Present Embodiment) FIG21 is a graph showing the heat sterilization control curve of the comparative example (equivalent to the conventional example) shown in FIG4 overlaid with the heat sterilization control curve of the present embodiment. The heat sterilization control curve of the comparative example is shown as a thick two-dot chain line, while the heat sterilization control curve of the present embodiment is shown as a thick solid line. When comparing the heat sterilization control of this embodiment with the heat sterilization control of the comparative example, the operation time of the heat sterilization control of the embodiment increases by the time TLag due to the addition of the preheating step and the medium-temperature water heat recovery step. However, because the initial temperature of the object heating step in the heat sterilization control of this embodiment is higher than the initial temperature of the object heating step in the heat sterilization control of the comparative example due to the implementation of the preheating step, the time Ui of the temperature rise step in the heat sterilization control of this embodiment is shorter than the time Ue of the temperature rise step in the heat sterilization control of the comparative example. Furthermore, because the initial temperature of the object cooling step in the heat sterilization control of this embodiment is lower than the initial temperature of the object cooling step in the heat sterilization control of the comparative example due to the implementation of the medium-temperature water heat recovery step, the time Di of the object cooling step in the heat sterilization control of this embodiment is shorter than the time De of the object cooling step in the heat sterilization control of the comparative example. Furthermore, because the heating step time Ui is shorter than the heating step time Ue, the amount of steam required to heat the high-temperature water Hth can be reduced. Furthermore, although steam is used to heat the intermediate-temperature water Htm during the preliminary preparation of the intermediate-temperature water Htm, the reuse of the intermediate-temperature water Htm and the reduction in the amount of steam required to heat the high-temperature water Hth can reduce the thermal energy required for the sterilization control when performing the sterilization control multiple times in this embodiment, compared to the comparative example, which performs the sterilization control multiple times. Furthermore, the heat sterilization control system of this embodiment injects medium-temperature water Htm into the sterilization tank 1 after the loading step. Therefore, compared to the temperature change Te1 of the sterilization tank 1 after the loading step in the comparative example, the temperature change Ti1 of the sterilization tank 1 after the loading step in this embodiment can reduce the temperature difference Td1. Furthermore, the heat sterilization control system of this embodiment injects medium-temperature water Htm into the sterilization tank 1 after the high-temperature water heat recovery step. Therefore, compared to the temperature change Te2 of the sterilization tank 1 after the loading step in the comparative example, the temperature change Ti2 of the sterilization tank 1 after the high-temperature water heat recovery step in this embodiment can reduce the temperature difference Td2. This suppresses rapid temperature changes in the sterilization tank 1, thereby reducing expansion and contraction of the sterilization tank 1. (Heat sterilization method) 7, 9, 12, 15, 18, 20 and 22, the heat sterilization method performed by the heat sterilization apparatus 100 will be described. The heat sterilization method is executed by the control unit 12 according to the heat sterilization program. Prior to the preheating step in step S1 shown in FIG22 , high-temperature water Hth and medium-temperature water Htm are prepared. The following description assumes that the medium-temperature water Htm is heated in the medium-temperature water heat recovery step (medium-temperature water heat recovery control) and stored in the medium-temperature water tank 4. Furthermore, the user performs a loading step (see FIG7 ) in which trays Tr carrying multiple preparation packets Rp are stacked in multiple layers into the sterilization tank 1. Step S1 shown in FIG22 is a preheating step performed after the loading step. The preheating step involves preheating the retort 1 using medium-temperature water Htm heated during heat recovery in the retort 1 before supplying high-temperature water Hth for heat-sterilizing the recipe packets Rp to the retort 1 (see FIG9 ). In step S2, an object heating step is performed. In the object heating step, high-temperature water Hth is supplied to the sterilization tank 1 for heat sterilization, and the preparation pack Rp in the sterilization tank 1 is heat sterilized by the high-temperature water Hth (see FIG. 12 ). In step S3, a high-temperature water heat recovery step is performed. In the high-temperature water heat recovery step, after heat sterilization by the high-temperature water Hth, the high-temperature water Hth in the sterilization tank 1 is recovered through the high-temperature water recovery path Re2 and stored in the high-temperature water tank 3 (see FIG13 ). In step S4, a medium-temperature water heat recovery step is performed. This step involves recovering heat from the sterilization tank 1 after heat sterilization using medium-temperature water Htm, which is generated separately from the high-temperature water Hth and has a temperature higher than the cooling water Cw but lower than the high-temperature water Hth, before the conditioning pack Rp is cooled by the cooling water Cw (see FIG. 15 ). In step S4, the object cooling step is performed. After the heat in the sterilization tank 1 is recovered, the heat-sterilized preparation packet Rp is cooled using cooling water Cw (see FIG. 18 ). Thus, after step S5, the heat sterilization method is terminated. Here, after the heat sterilization method is completed, the user performs a carry-out step of carrying out the cooled conditioning pack Rp from the sterilization tank 1 (see FIG. 20 ). (Seasoning Packet) The recipe packet Rp produced by this heat sterilization tank method is heat sterilized by the heat sterilization device 100 . Specifically, the conditioning pack Rp (the object to be sterilized) is heat-sterilized and then treated by a heat sterilization apparatus 100. The heat sterilization apparatus 100 includes a sterilization tank 1 and a control unit 12. The sterilization tank 1 has a storage space 1d. The storage space 1d accommodates the conditioning pack Rp (the object to be sterilized) to be heat-sterilized by high-temperature water Hth (high-temperature fluid). The sterilization tank 1 also receives a supply of high-temperature water Hth (high-temperature fluid) for heat sterilizing the conditioning pack Rp (the object to be sterilized) and cooling water for cooling the conditioning pack Rp (the object to be sterilized) after heat sterilization by the high-temperature water Hth (high-temperature fluid). The control unit 12 uses medium-temperature water Htm, which is generated separately from the high-temperature water Hth (high-temperature fluid) and has a temperature higher than the cooling water Cw but lower than the high-temperature water Hth (high-temperature fluid), to perform medium-temperature water heat recovery control to recover the heat of the sterilization tank 1 after heating and sterilization before cooling the conditioning package Rp (sterilization object) by the cooling water Cw. (Effects of this embodiment) This embodiment can achieve the following effects. In this embodiment, as described above, the heat sterilization apparatus 100 includes a control unit 12 that, before cooling the prepared package Rp (the sterilization target) with the cooling water Cw, performs a heat recovery step (heat recovery control) for recovering heat from the sterilization tank 1 after the target heating step (heat sterilization control) using medium-temperature water Htm (high-temperature fluid) generated separately from the high-temperature water Hth and having a temperature higher than the cooling water Cw but lower than the high-temperature water Hth. This recovery of heat from the sterilization tank 1 after heat sterilization using the medium-temperature water Htm generated separately from the high-temperature water Hth prevents the temperature of the high-temperature water Hth from decreasing, thereby preventing the time required to raise the high-temperature water Hth to the sterilization temperature Tst during the next heat sterilization after heat recovery. Furthermore, since the sterilization tank 1 can be cooled after the object heating step (heat sterilization control) using medium-temperature water Htm, which is higher than the cooling water Cw, before the prepared package Rp (the object to be sterilized) is cooled using the cooling water Cw, it is possible to suppress abrupt temperature changes (sudden temperature drops) in the sterilization tank 1 after the object heating step (heat sterilization control). As a result, unlike in the case of repeated large expansion and contraction, the expansion and contraction of the sterilization tank 1 can be reduced, thereby suppressing the increase in metal fatigue caused by thermal stress and preventing a decrease in the durability (shortening of the life) of the sterilization tank 1. Furthermore, in this embodiment, as described above, the controller 12 performs a medium-temperature water heat recovery step (medium-temperature water heat recovery control) to recover heat from the sterilization tank 1 after the object heating step (heat sterilization control) using medium-temperature water Htm, which is generated separately from the high-temperature water Hth and has a temperature higher than the cooling water Cw but lower than the high-temperature water Hth, before cooling the conditioning pack Rp (the object to be sterilized) with the cooling water Cw. Thus, in the medium-temperature water heat recovery step (medium-temperature water heat recovery control), heat from the sterilization tank 1 after the object heating step (heat sterilization control) is recovered using the medium-temperature water Htm, thereby suppressing heat loss from the conditioning pack Rp and the sterilization tank 1 during the object heating step (heat sterilization control). Furthermore, in this embodiment, as described above, the control unit 12 performs the medium-temperature water heat recovery step (medium-temperature water heat recovery control) while the high-temperature water Hth, which has been sterilized by heating, is being discharged from the sterilization tank 1. Thus, since heat recovery is achieved by simply discharging the high-temperature water Hth, a dedicated heat exchanger and water supply tank for heat recovery using the high-temperature water Hth are unnecessary, thereby reducing the need for an increased size of the device that would otherwise be required to recover heat using the high-temperature water Hth. Furthermore, in this embodiment, as described above, the heat sterilization apparatus 100 includes a medium-temperature water tank 4 that stores medium-temperature water Htm. The control unit 12 is configured to use the medium-temperature water Htm supplied from the medium-temperature water tank 4 to perform a medium-temperature water heat recovery step (medium-temperature water heat recovery control) to recover heat from the sterilization tank 1 after heat sterilization, before cooling the prepared package Rp (the sterilization target) with the cooling water Cw. Furthermore, the medium-temperature water Htm used in the medium-temperature water heat recovery step (medium-temperature water heat recovery control) is stored in the medium-temperature water tank 4. This allows the medium-temperature water Htm to be stored in the medium-temperature water tank 4, making it easier to supply the medium-temperature water Htm to the sterilization tank 1 after heat sterilization during heat recovery. Furthermore, when the medium-temperature water Htm used for heat recovery is not discharged but stored in the medium-temperature water tank, the heat recovered by heat recovery can be easily reused. Furthermore, in this embodiment, as described above, the control unit 12 performs a preheating step (preheating control) to preheat the sterilization tank 1 using the medium-temperature water Htm heated and stored in the medium-temperature water tank 4 during the medium-temperature water heat recovery step (medium-temperature water heat recovery control) before heating the prepared package Rp (the sterilization target) with the high-temperature water Hth. This preheating of the sterilization tank 1 using the heated medium-temperature water Htm used in the heat recovery step can raise the initial temperature of the sterilization tank 1 at the start of the target heating step (heat sterilization control). This reduces the amount of heat required to heat the high-temperature water Hth when raising the temperature to the target heating step (heat sterilization control) compared to a case where no preheating is performed. In other words, using the medium-temperature water Htm allows the heat recovered by heat recovery to be effectively utilized for preheating. As a result, during preheating, an increase in thermal energy required in the heat sterilization apparatus 100 can be suppressed, and accordingly, the amount of (high-temperature) steam used to increase the temperature of the high-temperature water Hth can be reduced. Furthermore, in this embodiment, as described above, the heat sterilization apparatus 100 includes a circulation path 5, a common pipe 6a, a branch pipe 6c, and a connecting pipe 8a (a first connecting path) interconnecting the sterilization tank 1 and the medium-temperature water tank 4. The control unit 12 controls the medium-temperature water Htm in the sterilization tank 1 after heat recovery to be recovered via the discharge pipe 5a, the discharge pipe 5b, the upstream pipe 5c, the downstream pipe 5d, the common pipe 6a, and the branch pipe 6c (the first connecting path) and stored in the medium-temperature water tank 4. Furthermore, the control unit 12 controls the supply of the medium-temperature water Htm to the sterilization tank 1 via the upstream pipe 5c, the downstream pipe 5d, and the connecting pipe 8a (the first connecting path) during preheating. Thus, the heat-recovered medium-temperature water Htm can be easily stored in the medium-temperature water tank 4 using the common pipe 6a and the branch pipe 6c (first connection path), and can be supplied from the medium-temperature water tank 4 to the sterilization tank 1 during preheating. Furthermore, in this embodiment, as described above, the control unit 12 controls the discharge of the medium-temperature water Htm supplied from the medium-temperature water tank 4 toward the conditioning pack Rp (the sterilization target) during the preheating of the sterilization tank 1 and the heat recovery of the sterilization tank 1. Thus, during preheating, when the low-temperature sterilization tank 1 is preheated, the discharged medium-temperature water Htm contacts the conditioning pack Rp (the sterilization target), causing the temperature of the medium-temperature water Htm to decrease. This lowered temperature medium-temperature water Htm can be supplied to the sterilization tank 1, thereby suppressing rapid temperature changes in the sterilization tank 1. Furthermore, during heat recovery of the sterilization tank 1, the discharged medium-temperature water Htm contacts the conditioning pack Rp (the sterilization target), causing the temperature of the medium-temperature water Htm to increase. This increased temperature medium-temperature water Htm can be supplied to the sterilization tank 1, thereby suppressing rapid temperature changes in the sterilization tank 1. This can suppress a decrease in the durability of the sterilization tank 1 due to an increase in thermal stress caused by a sudden temperature change during preheating of the sterilization tank 1 and heat recovery of the sterilization tank 1 . Furthermore, in this embodiment, as described above, the heat sterilization apparatus 100 includes a high-temperature water tank 3 that recovers and stores high-temperature water Hth, a high-temperature fluid, after the object heating step (heat sterilization control) stored in the sterilization tank 1. The heat sterilization apparatus 100 includes a common pipe 6a and a branch pipe 6b (second connection path) that interconnect the sterilization tank 1 and the high-temperature water tank 3. After the object heating step (heat sterilization control) of the conditioning package Rp (the object to be sterilized) is completed and the high-temperature water Hth discharged from the sterilization tank 1 is recovered into the high-temperature water tank 3 via the common pipe 6a and the branch pipe 6b (second connection path), the control unit 12 performs a heat recovery step (medium-temperature water heat recovery control) of the medium-temperature water in the sterilization tank 1. In this way, the high-temperature water Hth in the sterilization tank 1 is recovered through the dedicated common pipe 6a and the branch pipe 6b (second connection path) that connect the sterilization tank 1 and the high-temperature water tank 3 to each other, so that the heat of the high-temperature water Hth after the object heating step (heating sterilization control) is not taken away, thereby suppressing the temperature drop of the high-temperature water Hth recovered in the high-temperature water tank 3. Furthermore, in this embodiment, as described above, the heat sterilization apparatus 100 includes a circulation path 5, which includes a circulation pump 5f. The circulation pump 5f discharges the cooling water Cw, high-temperature water Hth, and medium-temperature water Htm discharged from the sterilization tank 1 and circulates them through the sterilization tank 1. The control unit 12 uses the circulation pump 5f to circulate the medium-temperature water Htm through the circulation path 5 through the sterilization tank 1, thereby performing the medium-temperature water heat recovery step (medium-temperature water heat recovery control). This allows the circulation path 5 used in the object heating step (heat sterilization control) and the object cooling step (cooling control) to be commonly utilized in the medium-temperature water heat recovery step (medium-temperature water heat recovery control), thereby suppressing the structural complexity and size of the heat sterilization apparatus 100 caused by the increase in the path length. Furthermore, in this embodiment, as described above, the conditioning pack Rp (the object to be sterilized) is heat-sterilized by a heat sterilization apparatus 100 including a sterilization tank 1 and a control unit 12. The sterilization tank 1 has a storage space 1d for storing the conditioning pack Rp (the object to be sterilized) to be heat-sterilized by high-temperature water Hth. The sterilization tank 1 receives a supply of high-temperature water Hth for performing an object heating step (heat sterilization control) on the conditioning pack Rp (the object to be sterilized) and cooling water Cw for cooling the conditioning pack Rp (the object to be sterilized) after the object heating step (heat sterilization control) by the high-temperature water Hth. Before the conditioning pack Rp (the object to be sterilized) is cooled by the cooling water Cw, the control unit 12 performs a medium-temperature water heat recovery step (medium-temperature water heat recovery control) for recovering heat from the sterilization tank 1 after the object heating step (heat sterilization control) using medium-temperature water Htm, which is generated separately from the high-temperature water Hth and has a temperature higher than the cooling water Cw but lower than the high-temperature water Hth. In this way, a conditioning package Rp (sterilization object) can be provided which is heat-sterilized by the heat sterilization device 100. Since the heat sterilization device 100 uses the medium-temperature water Htm generated separately from the high-temperature water Hth to recover the heat of the sterilization tank 1 after heat sterilization, the temperature of the high-temperature water Hth will not be reduced. Therefore, during the next heat sterilization after heat recovery, the time required to heat the high-temperature water Hth to the heat sterilization temperature Tst can be suppressed from being prolonged. In addition, the durability of the sterilization tank 1 can be suppressed from being reduced due to the increase in thermal stress caused by the sudden temperature change. Furthermore, in this embodiment, as described above, the heat sterilization method includes a step S4 of recovering heat from the retort tank 1 after the heat sterilization step (heat sterilization control) using intermediate-temperature water Htm, which is generated separately from the high-temperature water Hth and has a temperature higher than the cooling water Cw but lower than the high-temperature water Hth, before cooling the prepared package Rp (the sterilization target) with the cooling water Cw. This recovery of heat from the retort tank 1 after heat sterilization using the intermediate-temperature water Htm, which is generated separately from the high-temperature water Hth, prevents the temperature of the high-temperature water Hth from decreasing. Consequently, the provided heat sterilization method can prevent the time required to raise the high-temperature water Hth to the heat sterilization temperature Tst from being prolonged during the next heat sterilization step after heat recovery. Furthermore, it can prevent a decrease in the durability of the retort tank 1 due to increased thermal stress caused by rapid temperature changes. Furthermore, in this embodiment, as described above, the heat sterilization method includes a step S1 of preheating the sterilization tank 1 using the medium-temperature water Htm heated during heat recovery in the sterilization tank 1 before supplying the high-temperature water Hth to the sterilization tank 1 for the object heating step (heat sterilization control) of the preparation package Rp (the object to be sterilized). This preheating of the sterilization tank 1 can increase the initial temperature of the sterilization tank 1 at the start of the object heating step (heat sterilization control). Compared to a case where no preheating is performed, the amount of heat required to raise the high-temperature water Hth to the temperature required for the object heating step (heat sterilization control) can be reduced. Furthermore, since the intermediate-temperature water Htm after the intermediate-temperature water heat recovery step (intermediate-temperature water heat recovery control) is used to preheat the sterilization tank 1, raising the intermediate-temperature water Htm to the preheating temperature, the heat of the sterilization tank 1 and the preparation package Rp (sterilization target) after the object heating step (heat sterilization control) can be utilized. Thus, when the intermediate-temperature water Htm after the intermediate-temperature water heat recovery step (intermediate-temperature water heat recovery control) is used to preheat the sterilization tank 1, the thermal energy required for preheating in the heat sterilization apparatus 100 can be reduced, and accordingly, the amount of (high-temperature) steam used to raise the temperature of the high-temperature water Hth can be reduced. Furthermore, in this embodiment, as described above, the control unit 12 controls the flow path switching valves 6d, 6e, and 7b to be closed, and controls the flow path switching valves 5g and 8b to be open, during the preheating step, thereby forming the medium-temperature water injection path Sp1. Thereafter, the medium-temperature water Htm in the medium-temperature water tank 4 is injected into the sterilization tank 1 via the medium-temperature water injection path Sp1 using the circulation pump 5f. Thus, the medium-temperature water Htm can be injected from the medium-temperature water tank 4 into the sterilization tank 1 without using a pump other than the circulation pump 5f. Furthermore, in this embodiment, as described above, the control unit 12 controls the flow path switching valves 5g, 6d, 7b, and 8b to be closed and the flow path switching valve 6e to be open during the preheating step, thereby forming the medium-temperature water recovery path Re1. Thereafter, the medium-temperature water Htm is recovered to the medium-temperature water tank 4 via the medium-temperature water recovery path Re1 using the circulation pump 5f, thereby performing recovery control. This allows the medium-temperature water Htm to be recovered from the sterilization tank 1 to the medium-temperature water tank 4 without using a pump other than the circulation pump 5f. Furthermore, in this embodiment, as described above, the control unit 12 controls the flow path switching valves 6d, 7b, and 6e to be closed, and controls the flow path switching valves 5g and 8b to be open, during the medium-temperature water heat recovery step, thereby forming the medium-temperature water injection path Sp3. Thereafter, the medium-temperature water Htm in the medium-temperature water tank 4 is injected into the sterilization tank 1 via the medium-temperature water injection path Sp3 using the circulation pump 5f. Thus, the medium-temperature water Htm can be injected from the medium-temperature water tank 4 into the sterilization tank 1 without using a pump other than the circulation pump 5f. Furthermore, in this embodiment, as described above, the controller 12 controls the flow path switching valves 5g, 6d, 7b, and 8b to be closed, and the flow path switching valve 6e to be open, during the medium-temperature water heat recovery step, thereby forming the medium-temperature water recovery path Re3. The medium-temperature water Htm is then recovered to the medium-temperature water tank 4 via the medium-temperature water recovery path Re3 using the circulation pump 5f, thereby performing recovery control. This allows the medium-temperature water Htm to be recovered from the sterilization tank 1 to the medium-temperature water tank 4 without using any pump other than the circulation pump 5f. Furthermore, in this embodiment, the supply path 6 branches off from the circulation path 5 to supply high-temperature water Hth to the high-temperature water tank 3. Furthermore, the supply path 6 branches off from the circulation path 5 to supply medium-temperature water Htm to the medium-temperature water tank 4. The supply path 6 includes a common pipe 6a. The common pipe 6a is connected to the circulation path 5 and is common to both the high-temperature water tank 3 and the medium-temperature water tank 4. Thus, when the sterilization tank 1 is preheated with the medium-temperature water Htm, the medium-temperature water Htm flows through the common pipe 6a, preheating not only the sterilization tank 1 but also the common pipe 6a. Therefore, compared to a situation where the piping connecting the sterilization tank 1 to the high-temperature water tank 3 and the medium-temperature water tank 4 is not shared, when the high-temperature water Hth is supplied to the sterilization tank 1 after preheating, the common pipe 6a is also preheated. This suppresses not only the rapid temperature rise of the sterilization tank 1 but also the rapid temperature rise of the common pipe 6a. As a result, the risk of damage caused by stress due to a rapid temperature rise is reduced not only in the sterilization tank 1 but also in the common pipe 6a. Furthermore, when heat is recovered from the sterilization tank 1 using the medium-temperature water Htm, when the high-temperature water Hth in the sterilization tank 1 is recovered to the high-temperature water tank 3, the medium-temperature water Htm flows through the common pipe 6a heated by the high-temperature water Hth. Therefore, not only the heat from the sterilization tank 1 but also the heat from the common pipe 6a heated by the high-temperature water Hth is recovered by the medium-temperature water Htm. Thus, the heat of the common pipe 6a heated by the high-temperature water Hth can be recovered, so the temperature of the medium-temperature water Htm used for preheating the next sterilization tank 1 can be increased compared to the case where the common pipe 6a is not used. Furthermore, in this embodiment, as described above, the medium-temperature water tank 4 recovers and stores the preheated and heat-recovered medium-temperature water Htm stored in the sterilization tank 1. This allows the medium-temperature water Htm to be stored for preheating when the heat-recovered medium-temperature water Htm is recovered, and also allows the medium-temperature water Htm to be stored for heat recovery when the preheated medium-temperature water Htm is recovered. This allows a single medium-temperature water tank 4 to serve as both a source of medium-temperature water Htm for the sterilization tank 1 and a recycling station for the medium-temperature water Htm recovered from the sterilization tank 1, thereby achieving a heat sterilization apparatus 100 that performs heat recovery and preheating with a simple configuration. [Modification] It should be understood that all embodiments disclosed herein are for illustrative purposes only and are not intended to limit the present invention. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and includes all variations (modifications) within the scope and equivalents of the claims. For example, the above embodiment illustrates a heat sterilization apparatus 100 as a dispersing type apparatus equipped with a dispersing nozzle 2. However, the present invention is not limited thereto. In the present invention, the heat sterilization apparatus may also be a type of apparatus that uses medium-temperature water for preheating and heat recovery, or a steam-type apparatus that uses steam as the high-temperature fluid. For example, the hot water storage type heat sterilization apparatus 500 of the first modified example shown in FIG23 performs heat sterilization control as described below. Specifically, the control unit 512 performs heat sterilization control by heat sterilizing the preparation package Rp (heat sterilized object) using high-temperature water Hth (high-temperature fluid) in the object heating step, recovering the high-temperature water Hth (high-temperature fluid) discharged from the sterilization tank 1 into the high-temperature water tank 503. Subsequently, the heat of the sterilized sterilization tank 1 is recovered using medium-temperature water Htm generated separately from the high-temperature water Hth (high-temperature fluid), thereby performing medium-temperature water heat recovery control. Here, in the hot water storage type heating and sterilization device 500, after the high-temperature water Hth is recovered to the high-temperature water tank 503, the medium-temperature water Htm of the medium-temperature water tank 4 is circulated in the sterilization tank 1, thereby recovering the heat of the sterilization tank 1 after heating and sterilization, and the temperature of the high-temperature water Hth will not be reduced. Furthermore, for example, in the steam-type heat sterilization apparatus 600 of the second modified example shown in FIG24 , the following heat sterilization control can be performed. Specifically, the control unit 612 heat sterilizes the preparation packet Rp (heat-sterilized object) using high-temperature steam Vah (high-temperature fluid) during the object heating step. Thereafter, the control unit 612 uses medium-temperature water Htm generated separately from the high-temperature steam Vah (high-temperature fluid) to recover heat from the sterilization tank 1 after heat sterilization, thereby performing medium-temperature water heat recovery control. Here, the steam-type heat sterilization apparatus 600 uses steam Vah (high-temperature fluid) for heat sterilization instead of high-temperature water, and therefore cannot recover heat in the high-temperature water tank 3. However, according to the above-described configuration of the second modified example of this embodiment, by performing medium-temperature water heat recovery control, even the steam-type heat sterilization apparatus 600 can recover heat from the sterilization tank 1 after heat sterilization. Furthermore, the above embodiment illustrates that the heat sterilization apparatus 100 includes both the high-temperature water tank 3 and the medium-temperature water tank 4. However, the present invention is not limited thereto. In the present invention, the heat sterilization apparatus only needs to include the medium-temperature water tank and may not include the high-temperature water tank. Furthermore, the above embodiment illustrates that the heat sterilization device 100 is a device for heat sterilizing a food-enclosed food package Rp using high-temperature water Hth, but the present invention is not limited thereto. In the present invention, the heat sterilization device may also be a device for heat sterilizing other products such as cans. Furthermore, while the above embodiment illustrates a configuration in which the control unit 12 directly uses the medium-temperature water Htm supplied from the medium-temperature water tank 4 to preheat and recover heat from the sterilization tank 1 and the preparation packs Rp, the present invention is not limited thereto. Specifically, as described below, the heat sterilization apparatus may also include a modified configuration that indirectly utilizes medium-temperature water. Specifically, as shown in the third variation of FIG25 , the heat sterilization apparatus 700 includes a heat transfer fluid supply unit 713 for supplying heat transfer fluid Htf heated by medium-temperature water Htm. The heat sterilization apparatus 700 includes a heat exchanger 714 for performing heat exchange between the medium-temperature water Htm stored in the medium-temperature water tank 704 and the heat transfer fluid Htf supplied by the heat transfer fluid supply unit 713. During preheating of the sterilization tank 1, the control unit 12 supplies the heat transfer fluid Htf, which has been heated by heat exchange with the medium-temperature water Htm in the heat exchanger 714, to the sterilization tank 1. During heat recovery from the sterilization tank 1, the control unit 12 supplies the heat transfer fluid Htf, which has been heated by heat exchange with the medium-temperature water Htm in the heat exchanger 714, to the sterilization tank 1. Thus, compared to the case where medium-temperature water Htm is directly supplied to the sterilization tank 1, during the preheating of the sterilization tank 1, the heat transfer fluid Htf is heated by heat exchange with the medium-temperature water Htm in the heat exchanger 714. This allows the heat transfer fluid Htf to be gradually heated before being supplied to the sterilization tank 1. This suppresses the temperature difference between the heat transfer fluid Htf and the sterilization tank 1, allowing the heat transfer fluid Htf to gradually raise the temperature of the sterilization tank 1 to the preheating temperature. Consequently, rapid temperature changes in the sterilization tank 1 can be suppressed. Furthermore, the heat transfer fluid Htf is gradually cooled by heat exchange with the medium-temperature water Htm in the heat exchanger 714, recovering heat. This allows the heat transfer fluid Htf to be gradually cooled before being supplied to the sterilization tank 1. This suppresses the temperature difference between the heat transfer fluid Htf and the sterilization tank 1, allowing the heat transfer fluid Htf to gradually lower the temperature of the sterilization tank 1 to the post-heat recovery temperature (precooling temperature). Consequently, rapid temperature changes in the sterilization tank 1 can be suppressed. 25, the medium-temperature water tank 704 is connected to the heat exchanger 714. That is, the medium-temperature water tank 704 includes an inlet pipe 704c, a supply pipe 704d, a flow switching valve 704e, and a flow switching valve 704f. Furthermore, the above embodiment illustrates that the control unit 12 controls both the recovery of the preheated medium-temperature water Htm in the sterilization tank 1 and its storage in the medium-temperature water tank 4, and the recovery of the heat-recovered medium-temperature water Htm in the sterilization tank 1 and its storage in the medium-temperature water tank 4. However, the present invention is not limited to this. In the present invention, the control unit only needs to control at least one of the recovery of the preheated medium-temperature water in the sterilization tank and its storage in the medium-temperature water tank 4 and the recovery of the heat-recovered medium-temperature water in the sterilization tank and its storage in the medium-temperature water tank. Furthermore, in the above embodiment, for convenience of explanation, a flow-driven flowchart is used to illustrate the control processing of the control unit 12, in which processing is performed sequentially along the processing flow. However, the present invention is not limited to this. In the present invention, the control processing of the control unit can also be performed by event-driven processing, in which processing is performed in units of events. In this case, the control processing of the control unit can be performed using a complete event-driven processing, or a combination of event-driven and flow-driven processing can be used to perform the control processing of the control unit. 1: Sterilization tank 1a: Door for moving in and out 1b: Temperature sensor 1c: Water level sensor 1d: Containment Space 1e: Storage space 2: Spreading nozzle 2a: Injection port 3: High temperature water tank 3a: Temperature sensor 3b: Water level sensor 4:Medium temperature water tank 4a: Temperature sensor 4b: Water level sensor 5: Circular Path 5a: discharge pipe 5b: discharge pipe 5c: Upstream pipeline 5d: Downstream pipeline 5e: Temperature sensor 5f: Circulation pump 5g: Flow path switching valve 6: Supply path 6a: Shared pipeline 6b: Branch pipeline 6c: branch line 6d: Flow path switching valve 6e: Flow path switching valve 7: Discharge path 7a: Connecting pipes 7b: Flow path switching valve 8: Discharge path 8a: Connecting pipes 8b: Flow path switching valve 9: Supply Path 9a: Shared pipeline 9b: Connecting pipes 9c: Flow path switching valve 9d: Flow path switching valve 10: discharge path 10a: Shared pipeline 10b: Connecting pipes 10c: Flow path switching valve 10d: Flow path switching valve 10e: Steam dehumidifier 11: Heat exchanger 12: Control Department 100: Heating sterilization device 200: Cooling water source 301: Steam inlet 302: Steam exhaust pipe 401: Cooling water inlet 402: Cooling water outlet Cw: Cooling water Htm: Medium temperature water Hth: High temperature water Rp: conditioning package Tr: Tray

Claims

1. A heating sterilization apparatus comprising: a sterilization tank having an internal receiving space for accommodating an object to be sterilized by heating with a high-temperature fluid, and receiving the high-temperature fluid for heating and sterilizing the object and cooling water for cooling the object after sterilization by the high-temperature fluid; a medium-temperature water tank for storing medium-temperature water, which is generated separately from the high-temperature fluid, and the temperature of the medium-temperature water is higher than that of the cooling water but lower than that of the high-temperature fluid; and a control unit for supplying the medium-temperature water from the medium-temperature water tank to the sterilization tank before cooling the object by the cooling water, and using the medium-temperature water to perform medium-temperature water heat recovery control for recovering heat from the sterilization tank after heating and sterilization.

2. The heating sterilization apparatus as described in claim 1, wherein, The aforementioned control system is configured to perform the aforementioned medium-temperature hydrothermal recovery control while the aforementioned high-temperature fluid, which has been heated and sterilized, is discharged from the aforementioned sterilization tank.

3. The heating sterilization apparatus as described in claim 1, wherein, The aforementioned control unit is configured to use the aforementioned medium-temperature water to perform the aforementioned medium-temperature water heat recovery control before cooling the aforementioned sterilization target object by means of the aforementioned cooling water, and to accumulate the aforementioned medium-temperature water used for the aforementioned medium-temperature water heat recovery control into the aforementioned medium-temperature water tank.

4. The heating sterilization apparatus as described in claim 3, wherein, The aforementioned control unit is configured to preheat the sterilization tank by using the aforementioned medium-temperature water that has been heated and accumulated in the aforementioned medium-temperature water tank during the aforementioned medium-temperature water heat recovery control, before heating the aforementioned sterilization target object by the aforementioned high-temperature fluid.

5. The heating sterilization apparatus as described in claim 4 further comprises a first connection path that connects the aforementioned sterilization tank and the aforementioned medium-temperature water tank to each other; the aforementioned control unit is configured to control the recovery of the aforementioned medium-temperature water in the aforementioned sterilization tank after heat recovery through the aforementioned first connection path and to store it in the aforementioned medium-temperature water tank, and to control the supply of the aforementioned medium-temperature water to the aforementioned sterilization tank through the aforementioned first connection path during preheating.

6. The heating sterilization apparatus as described in claim 4, wherein, The aforementioned control unit is configured to control the release of the medium-temperature water supplied by the medium-temperature water tank toward the object to be sterilized during the preheating of the aforementioned sterilization tank and the heat recovery of the aforementioned sterilization tank.

7. The heating sterilization apparatus as described in claim 1 further comprises: a high-temperature water tank for recovering and storing high-temperature water of the aforementioned high-temperature fluid after heating and sterilization stored in the aforementioned sterilization tank; and a second connection path for connecting the aforementioned sterilization tank and the aforementioned high-temperature water tank to each other; the aforementioned control unit is configured to perform the aforementioned medium-temperature water heat recovery control of the aforementioned sterilization tank after the heating and sterilization of the aforementioned sterilized object is completed and the aforementioned high-temperature water discharged from the aforementioned sterilization tank is recovered into the aforementioned high-temperature water tank via the aforementioned second connection path.

8. The heating sterilization apparatus as described in claim 3 further comprises: a heat transfer fluid supply unit for supplying heat transfer fluid heated by the aforementioned medium-temperature water; and a heat exchanger for performing heat exchange between the aforementioned medium-temperature water accumulated in the aforementioned medium-temperature water tank and the aforementioned heat transfer fluid supplied by the aforementioned heat transfer fluid supply unit; the aforementioned control unit is configured to, during the preheating of the aforementioned sterilization tank, control the supply of the aforementioned heat transfer fluid whose temperature rises due to heat exchange with the aforementioned medium-temperature water in the aforementioned heat exchanger to the aforementioned sterilization tank, and during the heat recovery of the aforementioned sterilization tank, control the supply of the aforementioned heat transfer fluid whose temperature decreases due to heat exchange with the aforementioned medium-temperature water in the aforementioned heat exchanger to the aforementioned sterilization tank.

9. The heating sterilization apparatus as described in claim 1 further includes a circulation path, the circulation path including a circulation pump, the circulation pump discharging the aforementioned cooling water, the aforementioned high-temperature fluid and the aforementioned medium-temperature water discharged from the aforementioned sterilization tank and circulating them in the aforementioned sterilization tank; the aforementioned control unit is configured to perform the aforementioned medium-temperature water heat recovery control by circulating the aforementioned medium-temperature water in the aforementioned sterilization tank through the aforementioned circulation pump via the aforementioned circulation path.

10. A method for heat sterilization, comprising: supplying a high-temperature fluid to a sterilization tank to be sterilized by the high-temperature fluid, thereby sterilizing an object to be sterilized in the sterilization tank; accumulating medium-temperature water in a medium-temperature water tank, wherein the medium-temperature water is generated separately from the high-temperature fluid, and the temperature of the medium-temperature water is higher than that of cooling water used to cool the object to be sterilized but lower than that of the high-temperature fluid; supplying the medium-temperature water from the medium-temperature water tank to the sterilization tank before cooling the object to be sterilized by the cooling water, and using the medium-temperature water to perform heat recovery of the sterilization tank after heat sterilization; and cooling the object to be sterilized after heat sterilization by the cooling water after heat recovery of the sterilization tank.

11. The heating sterilization method as described in claim 10 further includes a step of preheating the sterilization tank using the medium-temperature water heated during the heat recovery process of the sterilization tank before the high-temperature fluid to be used for heating sterilization of the object to be sterilized is supplied to the sterilization tank.

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