Patent Publication Number: US-2022233013-A1

Title: Noodle boiling apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Japan application serial No. 2021-009513, filed on Jan. 25, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a noodle boiling apparatus. 
     Related Art 
     A noodle boiling apparatus is provided with a boiling tank storing water heated to a predetermined temperature, and boils noodles put into the boiling tank. Various methods have been known for heating the water in the boiling tank. 
     In a noodle boiling apparatus disclosed in Japanese Utility Model Patent Publication No. S62-032485, water in the boiling tank is heated by a gas burner installed below the boiling tank. In a noodle boiling apparatus disclosed in Japanese Patent Publication No. S57-009339, water in the boiling tank is heated by an electric heater provided in the boiling tank. In a noodle boiling apparatus disclosed in Japanese Patent Publication No. 6433104, vapor is supplied to the water in the boiling tank for heating. 
     In the conventional apparatus, water at room temperature is stored in the boiling tank, and then the water is heated. Therefore, it takes a relatively long time to start up the apparatus as it has to go through two steps, i.e., water supply and heating. In addition, the loss in heating is relatively large, and energy loss occurs. 
     Further, when noodles are boiled, precipitate such as starch dissolved from the noodles accumulates in the boiling tank. If this precipitate accumulates for a long time, it sticks to the bottom surface and the wall surface of the boiling tank, which may affect the quality of noodles and increase the labor for cleaning. To prevent the accumulation of precipitate, it is conceivable to increase the amount of water supplied to the boiling tank to increase the amount of water circulation, but there is a limit to the increase in the water supply amount as it causes a drop in the water temperature. 
     SUMMARY 
     An embodiment of the disclosure provides a noodle boiling apparatus including a noodle boiling unit, and a hot water supply mechanism supplying water, which is heated, to the noodle boiling unit. The noodle boiling unit includes a boiling tank storing the water and boiling noodles, a hot water pipe supplying the water, which is heated, to the boiling tank, and a discharge pipe discharging the water from the boiling tank to the hot water supply mechanism. The hot water supply mechanism includes a heat exchanger and a circulation pump. The heat exchanger includes a first passage having a first inlet to which vapor is supplied and a first outlet from which the vapor is discharged, and a second passage having a second inlet to which the water is supplied and a second outlet from which the water is discharged. The first inlet is connected to a vapor supplier which supplies the vapor, the second inlet is connected to the discharge pipe and a clean water supplier which supplies clean water, the second outlet is connected to the hot water pipe, and the water flowing in the second passage undergoes heat exchange by the vapor flowing in the first passage to be heated to a desired temperature. The circulation pump is provided between the second inlet and the discharge pipe and pumps the water to the second inlet. The hot water supply mechanism is configured to circulate the water constantly between the boiling tank and the hot water supply mechanism when the noodles are boiled. 
     In the noodle boiling apparatus according to an embodiment of the disclosure, water heated in advance by the heat exchanger is supplied to the boiling tank. Since the water supply to the boiling tank and the heating of the water are performed in parallel, start-up of the apparatus can be performed in a shorter time and with energy efficiency. In addition, when the noodles are being boiled, water can also be supplied to the boiling tank while avoiding causing a water temperature drop of the boiling tank as much as possible. Therefore, when the noodles are being boiling, water can be constantly circulated between the boiling tank and the hot water supply mechanism. As a result, it is possible to prevent precipitate from sticking to the boiling tank. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration view of a noodle boiling unit. 
         FIG. 2  is a cross-sectional view of the periphery of a boiling tank. 
         FIG. 3  is a circuit diagram of a hot water supply mechanism. 
         FIG. 4  is a schematic configuration view of a heat exchanger. 
         FIG. 5  shows flow paths during a start-up process before starting circulation of hot water. 
         FIG. 6  shows flow paths during the start-up process after starting circulation of hot water. 
         FIG. 7  shows flow paths during a noodle boiling process. 
         FIG. 8  shows flow paths during a pipe cleaning process. 
         FIG. 9  shows flow paths during a tank cleaning process. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The disclosure provides a noodle boiling apparatus with which start-up of the apparatus can be performed efficiently in a shorter time, and precipitate is less likely to stick to the boiling tank. 
     Hereinafter, an embodiment of the disclosure will be described with reference to the drawings. Various modification examples described below may be implemented in any combination. 
     A noodle boiling apparatus of this embodiment includes a noodle boiling unit  1 A which boils noodles, a hot water supply mechanism  1 B which supplies heated water to the noodle boiling unit  1 A, and a controller (not shown) which controls the noodle boiling unit  1 A and the hot water supply mechanism  1 B. The noodles in this specification generally refer to foods formed by kneading edible flour with water or the like, and include udon noodles, buckwheat noodles, somen noodles, hiyamugi, Chinese noodles, pasta, rice noodles, and cellophane noodles. In other words, the noodles in this specification include noodles using non-wheat edible flour as the main raw material. Further, in this specification, water heated to a predetermined temperature by the hot water supply mechanism  1 B is particularly referred to as hot water, and clean water before heating, more specifically, tap water at room temperature, is referred to as clean water. Further, in this specification, water vapor is simply referred to as vapor. 
     As shown in  FIG. 1  to  FIG. 3 , the noodle boiling unit  1 A of this embodiment includes a boiling tank  11 , a transfer device  12 , a hot water pipe  13 , a discharge pipe  15 , an overflow port  16 , a drain supply pipe  17 , and a water level gauge  18 . 
     Hot water is stored in the boiling tank  11 , and noodles put into the hot water are boiled. The noodle boiling unit  1 A of this embodiment is of a so-called continuous type, and a predetermined amount of noodles is transferred by the transfer device  12  and passes through the hot water of the boiling tank  11 . Specifically, the transfer device  12  has a chain  121 , sprockets  122 , buckets  123 , and a supply/discharge device (not shown), and noodles contained in the bucket  123  are guided inside the boiling tank  11  by the chain  121  and the sprockets  122 , and then discharged from the bucket  123 . The noodle boiling unit  1 A may also be of a so-called batch type which boils a large amount of noodles at one time. 
     The hot water pipe  13  is one or more pipes that supply hot water to the boiling tank  11 . In this embodiment, the hot water pipe includes a main hot water pipe  131 , a loosening jet pipe  132 , and a tank bottom jet pipe  133 . The main hot water pipe  131  has an opening provided at an upper part or above the boiling tank  11  and serves as a main supply port of hot water supplied from the hot water supply mechanism  1 B. The loosening jet pipe  132  and the tank bottom jet pipe  133  are configured to be capable of jetting hot water supplied from the hot water supply mechanism  1 B as jets, and are, for example, pipes on which holes are formed at a predetermined interval. Shower nozzles may also be provided at the holes of the pipes as necessary. The loosening jet pipe  132  ejects jets to noodles of the boiling tank  11  to loosen the noodles. In the noodle boiling unit  1 A of the continuous type, the loosening jet pipe  132  is provided in the boiling tank  11  so that the jets hit the transfer passage of the noodles. The tank bottom jet pipe  133  is provided at a lower part of the boiling tank  11  and ejects jets toward the bottom surface of the boiling tank  11 . Accordingly, it is possible to prevent precipitate generated during boiling noodles from accumulating and sticking to the bottom surface of the boiling tank  11 . 
     On-off valves  141  and  142  are respectively provided on the inlet sides of the loosening jet pipe  132  and the tank bottom jet pipe  133 . If necessary, hot water may be supplied to the boiling tank  11  using all of the main hot water pipe  131 , the loosening jet pipe  132 , and the tank bottom jet pipe  133 , or hot water may be supplied to the boiling tank  11  only from the main hot water pipe  131 . 
     The discharge pipe  15  has an opening provided at the lower part of the boiling tank  11 , and discharges hot water from the boiling tank  11  to the hot water supply mechanism  1 B. The hot water discharged from the discharge pipe  15  is reheated by the hot water supply mechanism  1 B and returned to the boiling tank  11  again. 
     The boiling tank  11  is configured to maintain a predetermined water level, and hot water exceeding the predetermined water level and overflowing from the boiling tank  11  is discharged from the overflow port  16  to the outside of the apparatus. During boiling noodles, the supply amount of hot water to the boiling tank  11  may be greater than the discharge amount and the evaporation amount of hot water from the boiling tank  11 . In other words, noodle boiling may be performed while constantly discharging hot water in the boiling tank  11  little by little to the outside of the apparatus via the overflow port  16 . Accordingly, precipitate in the boiling tank  11  can be discharged to the outside of the apparatus, and salt concentration and the like of the hot water can be kept uniform. 
     The drain supply pipe  17  has an opening provided inside the boiling tank  11  and supplies into the boiling tank  11  the drain generated from condensation of vapor in the hot water supply mechanism  1 B. By reusing the drain generated in the hot water supply mechanism  1 B, hot water can be circulated without wasting the heat energy of the drain. 
     The water level gauge  18  detects the water level of hot water in the boiling tank  11 . In this embodiment, the water level gauge  18  is configured to be capable of detecting the water level at which the circulation of hot water is started and the water level when the boiling tank  11  is full. 
     The hot water supply mechanism  1 B is configured to circulate water constantly between the boiling tank  11  and the hot water supply mechanism  1 B when the noodles are boiled. As shown in  FIG. 3 , the hot water supply mechanism  1 B of this embodiment includes a circulation passage  2  which circulates water between the boiling tank  11  and a heat exchanger  21 , a vapor passage  3  which supplies vapor to the heat exchanger  21 , a water supply passage  4  which supplies clean water to the heat exchanger  21 , a cleaning liquid pump unit  5  which supplies a cleaning liquid to the circulation passage  2 , a degassing passage  6  for performing degassing from the circulation passage  2 , and a drainage passage  7  which drains water to the outside of the apparatus. 
     The circulation passage  2  includes a heat exchanger  21 , a circulation pump  23 , a flow rate adjustment valve  25 , an on-off valve  27 , a filter  29 , and pipes connecting each part. The discharge pipe  15  and the hot water pipe  13  are connected by the circulation passage  2  having the heat exchanger  21 . Water and vapor are supplied to the heat exchanger  21 , and the water heated by heat exchange with the vapor is discharged from the heat exchanger  21  and sent to the boiling tank  11  via the hot water pipe  13 . The circulation pump  23  is provided upstream of the heat exchanger  21 , and pumps the water supplied from the water supply passage  4  and the water discharged from the boiling tank  11  to the heat exchanger  21 . The flow rate adjustment valve  25  controls the flow rate of water circulating in the circulation passage  2 . The on-off valve  27  is provided upstream of the hot water pipe  13  and is opened when hot water is supplied to the boiling tank  11 . The filter  29  removes impurities such as noodle scraps contained in the water discharged from the discharge pipe  15 . 
     The heat exchanger  21  of this embodiment is specifically a plate-type heat exchanger, but other types such as a multi-pipe heat exchanger and a spiral heat exchanger may also be adopted. As shown in  FIG. 3  and  FIG. 4 , the heat exchanger  21  of this embodiment is configured by overlapping a plurality of heat transfer plates  213 , and includes a first passage  211  partitioned by the heat transfer plates  213  and through which vapor flows, and a second passage  212  partitioned by the heat transfer plates  213  and through which water flows. The first passage  211  has a first inlet  211   a  to which vapor is supplied and a first outlet  211   b  from which vapor is discharged. The second passage  212  has a second inlet  212   a  to which water is supplied and a second outlet  212   b  from which water is discharged. The second inlet  212   a  is connected to a clean water supplier  41  via the water supply passage  4  and is connected to the discharge pipe  15 . The circulation pump  23  is provided between the second inlet  212   a  and the discharge pipe  15  and pumps water to the second inlet  212   a.  The second outlet  212   b  is connected to the hot water pipe  13 . With such a configuration, the water flowing through the second passage  212  undergoes heat exchange by the vapor flowing through the first passage  211  and is heated to a desired temperature. The temperature of hot water generated by the heat exchanger  21  is, for example, about 99° C. 
     The vapor passage  3  includes a first pressure reducing valve  33 , a second pressure reducing valve  35 , a proportioning valve  37 , a steam trap  39 , and pipes connecting each part. The vapor passage  3  is supplied with vapor from a vapor supplier  31 . The vapor supplier  31  is, for example, a boiler, which is a device capable of supplying water vapor at a predetermined temperature and pressure. The vapor supplier  31  is connected to the first inlet  211   a  of the heat exchanger  21  via the first pressure reducing valve  33 , the second pressure reducing valve  35 , and the proportioning valve  37 . The amount of vapor supplied to the heat exchanger  21 , and thus the temperature of hot water discharged from the heat exchanger  21 , may be controlled by the first pressure reducing valve  33 , the second pressure reducing valve  35 , and the proportioning valve  37 . For example, it is possible that temperature control is basically performed by the proportioning valve  37 , and the first pressure reducing valve  33  and the second pressure reducing valve  35  are used only when the control is difficult solely by the proportioning valve  37 . The steam trap  39  is connected to the first outlet  211   b  of the heat exchanger  21 . The steam trap  39  prevents vapor from leaking from the vapor passage  3  and discharges drain generated from the vapor to prevent problems such as a water hammer phenomenon. The drain discharged from the steam trap  39  is sent to the boiling tank  11  via the drain supply pipe  17 . 
     The water supply passage  4  is connected to the upstream side of the heat exchanger  21  of the circulation passage  2  and supplies clean water to the circulation passage  2 . The water supply passage  4  is supplied with clean water from the clean water supplier  41 . The clean water supplier  41  is, for example, a tap water supply. The water supply passage  4  of this embodiment is configured to be capable of switching the flow rate in two stages as necessary, and includes a first water supply passage and a second water supply passage that may supply clean water of different flow rates to the circulation passage  2 . The first water supply passage includes a flow rate adjustment valve  42 , a check valve  43 , and an on-off valve  44 . The second water supply passage branches from the middle of the first water supply passage and includes a flow rate adjustment valve  45 , a check valve  46 , and an on-off valve  47 . The first water supply passage has a larger suppliable flow rate than the second water supply passage. When it is desired to supply a relatively large amount of clean water, e.g., at the time of start-up or cleaning of the apparatus, the on-off valve  47  is closed and the on-off valve  44  is opened to supply clean water using the first water supply passage. The water supplied from the clean water supplier  41  is adjusted to a predetermined flow rate by the flow rate adjustment valve  42  and then sent to the circulation passage  2 . When it is desired to supply a relatively small amount of clean water, e.g., during boiling noodles, the on-off valve  44  is closed and the on-off valve  47  is opened to supply clean water using the second water supply passage. The water supplied from the clean water supplier  41  is adjusted to a predetermined flow rate by the flow rate adjustment valve  42  and the flow rate adjustment valve  45  and then sent to the circulation passage  2 . 
     By adding water through the water supply passage  4 , hot water can be circulated while discharging hot water from the overflow port  16 , and noodle boiling can be performed while keeping the inside of the boiling tank  11  clean. Further, since the water pressure from the clean water supplier  41  is applied in addition to the pressure by the circulation pump  23  to the water circulating in the circulation passage  2 , hot water can be circulated at a higher speed. Furthermore, although the water discharged from the discharge pipe  15  contains precipitate, since it is diluted with clean water supplied from the water supply passage  4  and then sent to the heat exchanger  21 , adhesion of the precipitate to the heat exchanger  21  can be suppressed. Specifically, the water supply passage  4  may be connected to the upstream side of the circulation pump  23 . In other words, the clean water supplied from the clean water supplier  41  may be supplied to the pipe connecting the circulation pump  23  and the discharge pipe  15 . According to such a configuration, since the temperature of water on the suction side of the circulation pump  23  can be lowered and the pressure of water on the suction side can be increased, cavitation can be prevented. 
     The cleaning liquid pump unit  5  is connected to any position of the circulation passage  2  and is configured to be capable of supplying a cleaning agent to the circulation passage  2 . The cleaning liquid pump unit  5  includes a cleaning liquid tank  51 , a cleaning liquid pump  53 , and an on-off valve  55 . At the time of cleaning the circulation passage  2 , the on-off valve  55  is opened, and the cleaning liquid stored in the cleaning liquid tank  51  is pumped by the cleaning liquid pump  53  to the circulation passage  2 . 
     The degassing passage  6  is connected to the downstream side of the heat exchanger  21  of the circulation passage  2  and discharges air and water vapor contained in water. The degassing passage  6  includes an on-off valve  61  and a pipe. The end of the pipe of the degassing passage  6  is opened upward, and the opening is provided at the highest position that water flows in the hot water supply mechanism  1 B. The air and water vapor that pass through the degassing passage  6  are discharged to the outside of the apparatus via the opening of the pipe. The degassing passage  6  is used only in a pipe cleaning process to be described later, and is not used in other processes in which degassing from the boiling tank  11  is possible. 
     The drainage passage  7  drains water out of the apparatus with a desired passage. In this embodiment, the drainage passage  7  includes a pipe that has one end connected between the second outlet  212   b  and the on-off valve  27  and the other end communicating with the outside of the apparatus, and this pipe is connected to a pipe between the discharge pipe  15  and the second inlet  212   a.  On-off valves  71 ,  73 ,  75 , and  77  are respectively provided on four sides of a connection point of the pipes. Specifically, the on-off valve  71  is provided between the second outlet  212   b  and the on-off valve  27 , the on-off valve  73  is provided on the outside of the apparatus, the on-off valve  75  is provided on the discharge pipe  15  side, and the on-off valve  77  is provided on the second inlet  212   a  side. 
     The noodle boiling apparatus is provided with pressure gauges, thermometers, and flow meters at appropriate positions. The pressure gauges, the thermometers, and the flow meters each display detected parameters to the operator. It is possible that at least a part of the pressure gauges, the thermometers, and the flow meters may output a signal indicating the detected parameter to the controller as necessary. In this embodiment, as the pressure gauges, a pressure gauge  811  is provided between the vapor supplier  31  and the first pressure reducing valve  33  of the vapor passage  3 , a pressure gauge  812  is provided between the first pressure reducing valve  33  and the second pressure reducing valve  35  of the vapor passage  3 , a pressure gauge  813  is provided between the proportioning valve  37  and the first inlet  211   a  of the vapor passage  3 , and a pressure gauge  814  is provided between the second outlet  212   b  and the hot water pipe  13  of the circulation passage  2 . As the thermometers, a thermometer  831  is provided in the boiling tank  11 , a thermometer  832  is provided near the second inlet  212   a  of the circulation passage  2 , a thermometer  833  is provided near the second outlet  212   b  of the circulation passage  2 , and a thermometer  834  is provided near the boiling tank  11  of the circulation passage  2 . As the flow meters, a flow meter  851  is provided between the second pressure reducing valve  35  and the proportioning valve  37  of the vapor passage  3 , a flow meter  852  is provided between the clean water supplier  41  and a branch point of the first water supply passage and the second water supply passage of the water supply passage  4 , and a flow meter  853  is provided in the degassing passage  6 . In this embodiment, the thermometer  831  is connected to the controller, and the controller performs temperature control by operating the proportioning valve  37 , the first pressure reducing valve  33 , and the second pressure reducing valve  35  based on the hot water temperature in the boiling tank  11  detected by the thermometer  831 . Further, in this embodiment, the flow meter  853  is connected to the controller, and the controller performs control associated with the pipe cleaning process to be described later based on the flow rate detected by the flow meter  853 . 
     The controller operates the noodle boiling apparatus to perform various control. Specifically, based on the operation by the operator and the signals from the water level gauge  18  and the thermometer  831 , the controller controls the transfer device  12 , the on-off valve  141 , the on-off valve  142 , the circulation pump  23 , the on-off valve  27 , the first pressure reducing valve  33 , the second pressure reducing valve  35 , the proportioning valve  37 , the on-off valve  44 , the on-off off valve  47 , the cleaning liquid pump  53 , the on-off valve  55 , the on-off valve  61 , the on-off valve  71 , the on-off valve  73 , the on-off valve  75 , the on-off valve  77 , etc. The controller may be configured by any combination of hardware and software as long as the desired control is achieved. 
     Herein, a method of boiling noodles by the noodle boiling apparatus of this embodiment described above will be described. The method of boiling noodles of this embodiment includes a start-up process, a noodle boiling process, a pipe cleaning process, and a tank cleaning process.  FIG. 5  to  FIG. 9  show the flow paths of water, vapor, etc. in each process, in which solid lines show the flow paths used, dotted lines show the flow paths not used, and dashed lines show the flow paths used as necessary (however, the dashed lines in the heat exchanger  21  are not limited to this). 
     In the start-up process, hot water of a predetermined temperature is stored in the boiling tank  11 . In other words, the water supply to the boiling tank  11  and the heating of water are performed in parallel. First, as shown in  FIG. 5 , clean water is supplied from the first water supply passage of the water supply passage  4 . The supplied clean water is pumped by the circulation pump  23  to the heat exchanger  21 , where the water undergoes heat exchange with vapor and is heated to a desired temperature. The hot water thus generated is stored in the boiling tank  11  via the main hot water pipe  131  of the hot water pipe  13 . At the time of start-up, the on-off valves  75  and  77  may be closed, and circulation of hot water may be not yet performed. When the water level gauge  18  detects that the hot water of the boiling tank  11  has reached a predetermined water level, the circulation of hot water is started. In other words, as shown in 
       FIG. 6 , the on-off valves  75  and  77  are opened, and the discharge pipe  15  and the heat exchanger  21  are communicated with each other. Hot water discharged from the boiling tank  11  and clean water supplied from the first water supply passage of the water supply passage  4  are together pumped by the circulation pump  23  to the heat exchanger  21 , are heated, and then are supplied to the boiling tank  11 . At this time, the on-off valves  141  and  142  are opened, and hot water is supplied to the boiling tank  11  via the main hot water pipe  131 , the loosening jet pipe  132 , and the tank bottom jet pipe  133  of the hot water pipe  13 . By storing the hot water while circulating the hot water, it is possible to prevent the temperature of the hot water in the boiling tank  11  from dropping during the start-up process. 
     When the water level gauge  18  detects that the boiling tank  11  is full, it is determined that the start-up process has been completed, and the noodle boiling process is performed. As shown in  FIG. 7 , the supply passage of clean water is switched from the first water supply passage to the second water supply passage, and a smaller amount of clean water than during the start-up process is supplied as added water. Similarly, the hot water discharged from the boiling tank  11  and the clean water supplied from the second water supply passage of the water supply passage  4  are together pumped by the circulation pump  23  to the heat exchanger  21 , are heated, and then are supplied to the boiling tank  11 . At this time, hot water is supplied to the boiling tank  11  via the main hot water pipe  131 , the loosening jet pipe  132 , and the tank bottom jet pipe  133  of the hot water pipe  13 . With hot water circulated in this manner, noodle boiling is performed in the noodle boiling unit  1 A. In other words, in this embodiment, the transfer device  12  is operated, and noodles are continuously transferred and boiled in the boiling tank  11 . Accordingly, during the noodle boiling process, water is constantly circulated between the boiling tank  11  and the hot water supply mechanism  1 B. Since water flows are constantly generated in the boiling tank  11 , precipitate is unlikely to adhere to the boiling tank  11 . 
     In the noodle boiling process, hot water may be circulated at a high speed to maintain the hot water temperature in the boiling tank  11 . Specifically, the required amount of circulating water is calculated as follows. The required amount of circulating water per minute is V (L/min), the amount of heat per minute radiated to the outside of the apparatus is Q (kcal/min), the amount of heat per minute taken by the noodles and the added water is W (kcal/min), the inlet temperature of water of the heat exchanger  21  is T 1  (° C.), and the outlet temperature of water of the heat exchanger  21  is T 2  (° C.). Herein, assuming that the density of the circulating water is 1.0 (g/cm 3 ) and the specific heat of the circulating water is 1.0 (cal/g·° C.), Mathematical Formula 1 below holds according to the formula of heat “heat (cal)=mass (g)×specific heat (cal/g· 20   C.)×temperature difference (° C.)”. 
     
       
         
           
             
               
                 
                   
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     In other words, in the noodle boiling apparatus of this embodiment, since a value obtained by dividing the amount of heat (kcal) per minute required for performing noodle boiling by the amount of temperature rise (° C.) due to the heat exchanger  21  is the required amount of circulating water V (L/min), the noodle boiling process may be performed while circulating hot water at this water amount or above. 
     According to an experiment, it is estimated that, regardless of the size of the boiling tank  11 , if hot water is circulated at a water amount equal to or greater than a value obtained by dividing a water amount (L) at the time of full capacity of the boiling tank  11  by 2, the required amount of circulating water V (L/min) or above may be obtained, and the hot water temperature may be maintained. 
     After the noodle boiling process is completed, the pipe cleaning process is performed. First, with the on-off valves  27 ,  75 , and  77  being closed, the on-off valves  71  and  73  are opened, and the water in the circulation passage  2  is drained. Next, as shown in  FIG. 8 , with the on-off valves  27 ,  73 , and  75  being closed, the on-off valves  71  and  77  are opened, and a flow path through which water may circulate is formed without going through the boiling tank  11 . Then, clean water is supplied from the second water supply passage of the water supply passage  4  to the circulation passage  2 . At this time, the on-off valve  61  is opened, and air and water vapor pushed out by water are discharged from the degassing passage  6 . When the flow meter  853  detects that the water has reached the degassing passage  6 , the on-off valve  61  is closed. Accordingly, it is possible to prevent air or water vapor from flowing into the circulation pump  23 . On the other hand, the on-off valve  55  is opened, and the cleaning liquid is appropriately supplied from the cleaning liquid pump unit  5  to the circulation passage  2 . When the flow meter  853  detects a predetermined flow rate and determines that the pipe of the circulation passage  2  is filled with water containing the cleaning liquid, the on-off valve  47  is closed, and the water supply from the water supply passage  4  is stopped. In this state, the water containing the cleaning liquid is pumped by the circulation pump  23  and circulates in the pipe. Depending on the type of the cleaning liquid, the circulating water may be heated by the heat exchanger  21  to enhance the cleaning effect. After circulating the water for a predetermined time, the on-off valve  77  is closed, the on-off valve  73  is opened, and the water is discharged to the outside of the apparatus. Then, the above procedure is repeated to perform pipe cleaning. 
     After the pipe cleaning process is completed, the tank cleaning process is performed. First, as shown in  FIG. 9 , with the on-off valves  71  and  77  being closed, the on-off valves  73  and  75  are opened, and the water stored in the boiling tank  11  is discharged. Afterwards, the boiling tank  11  is cleaned by any method. For example, when the boiling tank  11  is provided with a nozzle (not shown) capable of ejecting pressurized hot water or a cleaning liquid, cleaning-in-place of the boiling tank  11  is performed using the nozzle. Alternatively, the operator may also manually clean the boiling tank  11 . The pipe cleaning process and the tank cleaning process may be performed in parallel, or the tank cleaning process may be performed first. 
     As having been specifically shown in some examples, the disclosure it is not limited to the configuration of the embodiment shown in the drawings, and various modifications or applications are possible without departing from the technical concept of the disclosure. 
     For example, in this embodiment, the drain generated from the vapor used for heat exchange is supplied to the boiling tank  11  via the drain supply pipe  17 , but the drain may also be discharged to the outside of the apparatus. 
     Further, it is desirable that the pressure of vapor supplied to the heat exchanger  21  is suppressed as low as possible. Therefore, specifically, the pressure of vapor adjusted by at least one of the first pressure reducing valve  33  and the second pressure reducing valve  35  is desirably 0.03 MPa or more and 0.07 MPa or less. Latent heat decreases as pressure increases. By lowering the pressure of vapor, heat exchange can be efficiently performed in the heat exchanger  21 , and the amount of vapor used can be reduced. 
     Further, when the set temperature of hot water is a high temperature close to 100° C., it is desirable that the proportioning valve  37  is controlled by PID control. By setting an appropriate gain value, it is possible to prevent boiling of hot water and prevent temperature variation.