JP2016148493A - Air conditioning system for large space - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain constant temperature in an air conditioning space and improve work environment in the air conditioning space.SOLUTION: An air conditioning system 10 for a large space for cooling a large space S in which a heating element M is installed to a constant temperature, makes cooling air forcibly faced downward and linearly blown down in a plurality of places in the large space S excluding right above a heating place of the heating element M thereby to reach a floor surface; and makes air heated by the heating element M ridden on an upward current and linearly raised naturally without colliding with cooling air having been blown down.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an air conditioning system for a large space for cooling a large space in which a device with a large amount of heat is installed at a constant temperature.

  Conventionally, various devices and systems are equipped to cool a large space where a device with a large amount of heat generation is installed, such as a metal processing factory where machine tools are installed and a data center where large computers are installed.

  However, in such a large space, it takes time to mix the air heated by the waste heat of the equipment with the air for cooling and take off the heat load. There is a problem that the heat drifts in the air-conditioned space and may hinder the performance of the device.

  In addition, temperature unevenness between an area where a device with a large amount of heat generation is installed and an area where the device is not installed, or a temperature caused by irregularly performing operations that cause a device with a large amount of heat to operate or stop Unevenness is likely to occur. Further, the waste heat from the device moves horizontally in the air-conditioned space, so that a high temperature region is easily formed like a river flow toward the suction port. Therefore, there is a problem that it is difficult to keep the air-conditioned space at a constant temperature due to these factors.

  Therefore, in order to solve the problems as described above, for example, by giving a swirl component to the low-temperature air blown sideways from the air supply port of the air supply chamber installed on the wall surface toward the air-conditioned space, A replacement ventilation system has been proposed in which the amount of air attracted by low-temperature air is increased and the temperature difference between the conditioned spaces is reduced (see, for example, Patent Documents 1 and 2 or Non-Patent Document 1).

  In addition, by using the momentum of jet air blown out at high speed from the nozzle of the blower unit installed on the ceiling, the apparent ventilation frequency is increased to form a constant temperature environment in the room. An air-conditioning ventilation system has also been proposed (see, for example, Patent Document 3 or Non-Patent Document 2).

JP 2002-372268 A (Patent No. 4006196) Japanese Patent Laying-Open No. 2005-282892 (Patent No. 4421347) JP 07-318124 A (Patent No. 3339527)

Takasago Thermal Engineering Co., Ltd. website (http://www.tte-net.co.jp/solution/systems/009.html) regarding the swirl flow induced stratified air conditioning system Nihon Floda Co., Ltd. website (http://www.nipponfloda.co.jp/products/dv/dv.html) about large space special air conditioning ventilation system

  However, in the conventional replacement ventilation system described above, since the air supply chamber is installed on the wall surface, depending on the arrangement of the equipment installed in the air-conditioned space, low-temperature air blown out from the air supply port of the air supply chamber may be There is a risk of not reaching the surroundings of the device sufficiently. For this reason, a temperature difference occurs in the air-conditioned space, and there is a problem that it is difficult to maintain the air-conditioned space at a constant temperature.

  In addition, there is a problem in that work in the air-conditioned space is hindered because the air velocity of the cooling air is high in the immediate vicinity of the air supply port of the air supply chamber installed on the wall surface.

  Furthermore, since the wall surface is used as an installation space for the air supply chamber, equipment cannot be placed near the wall, or in the case of a factory, the air supply chamber may interfere with the running of the forklift. There are also problems.

  Furthermore, in a factory with a space of 100 m square, for example, the air supply chambers installed on the walls on both sides must be responsible for a temperature environment of 50 m in length, so that the temperature environment in the air-conditioned space tends to be uneven. As described above, there is a problem that as the space becomes larger, delicate temperature control cannot be performed.

  On the other hand, the above-mentioned conventional Derivet (registered trademark) type air-conditioning ventilation system has a problem in that work in the air-conditioned space is hindered because the air velocity is very fast in front of the nozzle of the blower unit.

  In addition, when the amount of heat generated from the equipment in the air-conditioned space is large or the ceiling height in the air-conditioned space is high, the air for cooling must be sufficiently agitated only with the induced airflow from the nozzle of the general-purpose class blower unit. Therefore, there is a problem that it is difficult to maintain the air-conditioned space at a predetermined temperature.

  The present invention has been made to solve the various problems described above, and provides an air conditioning system for large spaces that can maintain a constant temperature in the air-conditioned space and does not interfere with the work in the air-conditioned space. The purpose is to do.

  The present invention is an air conditioning system for a large space for cooling a large space in which a heating element is installed at a constant temperature, and forcing cooling air at a plurality of locations in the large space except directly above the heating point of the heating element. The air heated by the heating element is placed on an ascending airflow without colliding with the air for cooling that has been blown down, and is linearly natural. It is characterized by raising.

  According to this feature, the air-conditioned space can be maintained at a constant temperature, and the working environment in the air-conditioned space can be improved.

  In the large space air conditioning system according to the present invention, the large space is an air conditioning space that needs to be maintained at a predetermined temperature, and is outside the air conditioning management that is located above the air conditioning space and does not need to be maintained at the predetermined temperature. It is preferable to have a space.

  According to this feature, since the volume of the air-conditioned space can be minimized, the energy saving effect can be enhanced.

  In the large space air conditioning system according to the present invention, in the space outside the air conditioning management, an air conditioner that forcibly sends the cooling air and a variable that adjusts the cooling air sent from the air conditioner to a predetermined air volume. An air volume device, an air outlet that blows out air for cooling adjusted to a predetermined air volume by the variable air volume device toward the air-conditioned space, and a suction port that sucks in air that has been naturally raised by being heated by the heating element. It is preferable.

  According to this feature, the space in the large space can be used effectively.

  In the large space air conditioning system according to the present invention, it is preferable that the air conditioned space has a plurality of zones divided for each predetermined area, and the air conditioner is provided for each zone.

  According to this feature, the environment in the air-conditioned space can be accurately controlled.

  In the large space air conditioning system according to the present invention, it is preferable that the cooling air is blown out from the air outlet so that an airflow velocity in the air conditioned space is a low speed of 0.6 m / s or less.

  According to this feature, the working environment in the air-conditioned space can be enhanced and work efficiency can be improved.

  In the air conditioning system for large spaces according to the present invention, it is preferable that the heating element is a machine whose rated heat generation amount per place is 5 to 30 kW and whose heat generation amount varies.

  According to this feature, the inside of the air-conditioned space can be maintained at a constant temperature by following the fluctuation in the amount of heat generated from the heating element.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to maintain the inside of an air conditioned space at constant temperature, various effects, such as being able to improve the working environment in an air conditioned space, can be acquired.

It is a conceptual diagram which shows the air conditioning system for large spaces which concerns on embodiment of this invention. It is a duct top view (upper space) which shows the air conditioning system for large spaces concerning an embodiment of the invention. It is a perspective view which shows the mobile temperature sensor used in the air conditioning system for large spaces which concerns on embodiment of this invention. It is a top view which shows the screen of the monitor of tablet PC used in the air conditioning system for large spaces which concerns on embodiment of this invention.

  Hereinafter, an air conditioning system for large spaces according to an embodiment of the present invention will be described with reference to the drawings. Here, FIG. 1 is a conceptual diagram showing a large space air conditioning system according to an embodiment of the present invention, FIG. 2 is a duct plan view (upper space) showing a large space air conditioning system according to an embodiment of the present invention, FIG. 3 is a perspective view showing a mobile temperature sensor used in the large space air conditioning system according to the embodiment of the present invention, and FIG. 4 shows a tablet PC used in the large space air conditioning system according to the embodiment of the present invention. It is a top view which shows the screen of a monitor.

  In the following description, a case where the large space air conditioning system according to the present invention is used in a large space S of a metal processing factory where a plurality of machine tools M as heating elements are installed will be described.

  As shown in FIG. 1, the large space S does not need to be maintained at a predetermined temperature by being positioned at the ceiling level above the air-conditioned space Sa that needs to be maintained at a predetermined temperature and the air-conditioned space Sa. And an air conditioning management outside space Sb. The air-conditioned space Sa has a plurality of zones Z1 to Zn divided in a plane, and the air-conditioning outside management space Sb is divided in a plane so as to correspond to the zones Z1 to Zn of the air-conditioned space Sa.

  A large space air conditioning system 10 according to an embodiment of the present invention includes an air conditioner 11, a variable air volume device (VAV) 12, and an air outlet 13. The air conditioner 11, the variable air volume device (VAV). 12 and the blower outlet 13 are each installed in the air conditioning management outside space Sb.

  The air conditioner 11 includes a main body 17 having a cooling coil 15 and a fan 16 disposed in a casing, a supply chamber 18 disposed downstream of the main body 17 in the air flow direction, and an upstream of the main body 17 in the air flow direction. And a return chamber 19 disposed on the side.

  A main duct 21 is connected to the supply chamber 18 via a damper 20, and a plurality of branch ducts 22 are further branched from the main duct 21 and connected to the downstream side of the main duct 21 in the air flow direction. Air outlets 13 are respectively attached to the downstream ends of the branch ducts 22 in the airflow direction, and the variable air volume devices (VAVs) 12 are attached to the airflow direction upstream of the air outlets 13, respectively. In addition, a suction port (not shown) is opened in the return chamber 19, whereby the air conditioning management outside space Sb forms a heat accumulation region, and this heat accumulation is returned to the air conditioner 11.

  The large space air conditioning system 10 according to the embodiment of the present invention is an outdoor air treatment air conditioner (hereinafter referred to as “external air conditioner 24”) installed in a machine room outside or outside the large space S. )), And an air supply port 26 connected to the external air conditioner 24 via an air supply duct 25, and an exhaust air port 28 connected to the external air conditioner 24 via an exhaust air duct 27. The air supply port 26 and the exhaust port 28 are disposed in the air conditioning management outside space Sb and open to the air conditioning management outside space Sb. Preferably, the air supply port 26 and the exhaust port 28 are disposed at a position higher than the air outlet 13, the air supply port 26 is provided so as to be able to blow outside air in the downward vertical direction, and the exhaust port 28 is air-conditioned from the horizontal direction. It is provided so that air in the non-managed space Sb can be sucked.

FIG. 2 shows a large space air conditioning system 10 according to an embodiment of the present invention installed in a large space S of a metal processing factory having a floor area of 2000 m ² (40 m × 50 m square) and a ceiling height (straight sky) of 13 m. A plan view of the case is shown. In this large space S, a space up to 4.5 m above the floor is set as the air-conditioned space Sa. This air-conditioned space Sa is planarly divided into 20 zones Z1 to Z20, and each of the zones Z1 to Z20 has a floor area of 100 m ² of 10 m × 10 m square.

  In the air-conditioned space Sa, a machine tool M (see FIG. 1) whose rated heat generation amount per place is 5 to 30 kW and whose heat generation amount varies is fixed on a mat slab (pressure plate or solid base). 0 to 2 machine tools M are arranged in each of the zones Z1 to Z20 of the air-conditioned space Sa. In addition, since it is difficult to manage the temperature in the vicinity of the wall surface due to the Coanda effect, when placing the machine tool M, it is preferable to consider that the heat generation point of the machine tool M is not located in the area in the vicinity of the wall surface. Further, a mobile crane C (see FIG. 1) is attached to the space Sb outside the air conditioning management of the large space S so as to be linearly movable between opposing walls.

  In the air-conditioned space Sa of the large space S shown in FIG. 2, it is required to maintain an environment with a temperature of 23 ° C. ± 1 ° C., a humidity of 50% or less, and an air velocity of 0.6 m / s or less throughout the year. In order to realize this environment, each of the 20 air conditioning management outside spaces Sb divided in a plane corresponding to the zones Z1 to Z20 of the air conditioning space Sa has one air conditioner 11, 9 per section. A variable air volume device (VAV) 12 and nine air outlets 13 are provided.

  Each air conditioner 11 includes a cooling coil 15 having a cooling capacity of 21 kW and a fan 16 having an air flow rate of 18000 CMH, and air supply from each air conditioner 11 by a control sensor (not shown) described later. Cascade control is performed so that the temperature becomes a predetermined temperature. In this case, the supply air temperature of the cooling air from the 20 air conditioners 11 in each of the zones Z1 to Z20 is 18.5 ° C. to 24.5 ° C. with respect to 23 ° C. which is the required temperature in the air conditioned space Sa. It is preferable that the temperature is controlled to a temperature as close to 23 ° C. as possible while following the heat load from the machine tool M.

  Each variable air volume device (VAV) 12 is provided so that the opening degree can be adjusted manually between 0 and 100% (or automatically controlled) and a maximum air volume of 2000 CMH can be supplied to each air outlet 13. . Each air outlet 13 is of a nozzle type and is provided so that cooling air can be blown out linearly from a height of 11 m above the floor in a downward vertical direction. The external air conditioner 24 has a cooling capacity of 168 kW, a heating capacity of 144 kW, and an air blowing capacity of 9000 CMH. The air outlet 13 may be an air outlet of a type other than the nozzle, such as a line diffuser or a square diffuser.

  Further, a fixed-point temperature sensor (not shown) and a movable temperature sensor 29 are installed in the air-conditioned space Sa. The fixed-point temperature sensor includes a control sensor for controlling the air conditioner 11 and a measurement sensor for measuring the temperature in the air-conditioned space Sa, and each of the columns and walls of the air-conditioned space Sa. In a predetermined position, it is fixed at four places in the upper and lower sides (in order from the lower side, each height of 300 mm, 1500 mm, 3000 mm, 4500 mm on the floor).

  As shown in FIG. 3, the mobile temperature sensor 29 includes a carriage 31 having wheels 30, a pole 32 erected perpendicularly to the carriage 31, and four upper and lower positions of the pole 32 (in order from the lower side, And a wireless sensor 33 fixed to a height of 300 mm, 1500 mm, 3000 mm, and 4500 mm on the floor. Each wireless sensor 33 is configured to be communicable with a central monitoring device (not shown), thereby enabling the temperature of an arbitrary place in the air-conditioned space Sa to be described later and a monitor (not shown) of the central monitoring device. ) Can be monitored.

  Next, the operation of the large space air conditioning system 10 having the above-described configuration will be described.

  In the air conditioners 11 in the zones Z1 to Z20, the cooling air cooled to a predetermined temperature by the cooling coil 15 and sent out by the fan 16 has been adjusted to a predetermined opening degree in advance through the main duct 21 and the branch duct 22. Each variable air volume device (VAV) 12 adjusts to a predetermined air volume.

  In this case, the opening degree of each variable air volume device (VAV) 12 is adjusted in advance according to the arrangement of the machine tool M in the air-conditioned space Sa, and corresponds to the air outlet 13 located immediately above the heat generation point of the machine tool M. The variable air volume device (VAV) 12 is fully closed (opening degree 0%). The opening adjustment of each variable air volume device (VAV) is manually performed using the tablet PC 34, as shown in FIG.

  The tablet PC 34 is configured to be communicable with the central monitoring device via the Internet, and is capable of monitoring temperature, changing the opening of the variable air volume device (VAV) 12 (multiple selection and batch conversion is possible), and setting the indoor temperature setting value. Change, call the summary graph of the central monitoring device to monitor the heat source (not shown) of the air conditioner 11 and the condition of the external air conditioner 24, or the fixed point temperature sensor and the mobile temperature sensor 29 The temperature of the wireless sensor 33 is displayed, or a plurality of opening patterns of the variable air volume device (VAV) 12 are registered.

  In this way, the air for cooling adjusted to a predetermined air volume by each variable air volume device (VAV) 12 is supplied from each air outlet 13 to the air-conditioned space so that the air flow velocity in the air-conditioned space Sa becomes a low speed of 0.6 m / s or less. It is blown down linearly in the downward vertical direction toward Sa and reaches the floor surface. At this time, since the cooling air is not blown down from the air outlet 13 located immediately above the heat generation point of the machine tool M, the warm air heated by the machine tool M collides with the blown-down cooling air. It rises naturally in a straight line with an updraft.

  Thereafter, a part of this naturally elevated warm air is sucked into the exhaust port 28 and is discharged to the outside through the exhaust duct 27. On the other hand, air having the same air volume as the discharged air is taken in from the outside by the external air conditioner 24, supplied through the air supply duct 25 from the air supply port 26 into the air-conditioning management outside space Sb, and the naturally raised air Mixed with. The air thus mixed returns to the air conditioner 11 via the suction port of the return chamber 19 and is cooled by the cooling coil 15 and then blown out into the air conditioned space Sa by the fan 16 to form a circulating airflow. Is done.

  As described above, in the large space S of the metal processing factory where the large-space air conditioning system 10 operates, the machine tool M is monitored for 48 hours in each state of no load and loaded (full operation). Using the mobile temperature sensor 29, environmental measurements were performed randomly in more than 200 areas with different positions and heights of the air-conditioned space Sa. All these areas were within a temperature range of 23 ° C ± 1 ° C. I was able to confirm that it was received. At this time, when the air velocity was measured at any 10 locations in the air-conditioned space Sa, it was possible to obtain a good result of 0.49 m / s at the maximum at no load (or less at the time of load). It was.

  These results show that the air conditioning system 10 for large spaces according to the embodiment of the present invention does not stir the room with a direct airflow or an induced airflow, so that the cooling air moves and the temperature in the air-conditioned space Sa is uniform. It is a characteristic thing that shows that it is possible. In other words, in the air-conditioned space Sa where there is a large amount of air, it is difficult for the air for cooling to rise except for the upward air flow of the air heated by the heat generated by the equipment (machine tool M). Flows into an area where there is little. For this reason, even if the air conditioner 11 that is in charge of a certain zone is in a blowing operation, the temperature may be lower than the blowing temperature due to the inflow of air from the area near the zone. In addition, the air heated by the heat generated by the equipment reaches the exhaust port 28 and the suction port of the return chamber 19 of the air conditioner 11 in a short time, but the air for cooling is on the ceiling surface unless the updraft lifts up. The exhaust port 28 and the suction port that are arranged cannot be reached. Further, when the device is stopped, the ascending air current is stopped and the air just stops moving as in the area where no heat is generated, and the change in the environment of the air-conditioned space Sa is small. In this way, only the cooling air whose temperature has been raised by heat exchange or mixing becomes lighter in specific gravity and rises toward the exhaust port 28 or the suction port, and remains at a low temperature where it does not work as cooling air. Since the air stays in the low-rise part of the large space S for a long time, the air conditioning system 10 is a thermally highly efficient system.

  In addition, the large space air conditioning system 10 according to the embodiment of the present invention is characterized in that the number of circulations is extremely small. When trying to maintain a metal processing factory at a set temperature ± 1 ° C with a conventional air conditioning system, in order to exchange heat and heat with the waste heat from the equipment, it is usually It is necessary to plan the number of circulations from 60 to 80 times. However, since this large space air conditioning system 10 does not require heat exchange or mixing in the first place, the number of cooling air circulations can be reduced to about nine. Furthermore, since the cooling air returns to the air conditioner 11 by natural circulation, the external static pressure of the fan 16 of the air conditioner 11 is almost only the main duct 21 and the branch duct 22 for supplying air, and energy saving performance is achieved. Can be improved.

  As described above, according to the large space air conditioning system 10 according to the embodiment of the present invention, the air (heat load) heated by the machine tool M rides on the rising airflow and naturally rises to the air conditioning control outside space Sb. The air for cooling from the air conditioner 11 is blown out at a low speed toward the air-conditioned space Sa, and reaches the floor without being mixed with the heated air (heat load) that rises. In other words, in the large space air conditioning system 10 according to the embodiment of the present invention, the concept of removing the heat load with the cooling air is not used, and therefore, waste heat from the machine tool M is sucked into the air conditioner 11. However, since the temperature of the cooling air from the air conditioner 11 is hardly increased, the amount of cooling air blown out can be reduced.

  In addition, after the cooling air blown down from the air outlet 13 reaches the floor surface, it expands horizontally along the floor surface, and the inside of the air-conditioned space Sa is almost in a laminar flow state. There is no need to force return. Further, since it rises independently from the air heated by the machine tool M, the air age is not uniform as in the conventional replacement air conditioning system, and the fan 16 is not affected even when the ceiling height of the large space S is increased. There is no need to increase the power. Therefore, energy saving can be promoted.

  Furthermore, as the area of the machine tool M that generates a large amount of heat is generated, a larger upward air flow is generated, and the air pressure decreases accordingly, so that the surrounding air is sucked in. Therefore, the temperature in the air-conditioned space Sa is automatically leveled. can do. Further, since the cooling air blown down from the air outlet 13 does not collide with the rising airflow, an airflow arranged like a river flow can be formed in the air-conditioned space Sa, and so-called turbulent flow is not generated. , Do not spread the heat load.

  In addition, since the airflow speed in the air-conditioned space Sa is low, there is no possibility that the work in the air-conditioned space Sa will be hindered, and the work environment can be improved. Furthermore, since the cooling air is blown down, the airflow sufficiently reaches the periphery of the machine tool M and the dead angle of the airflow disappears, so that the performance of the machine tool M can be maintained high.

  In order to maintain the air-conditioned space Sa in a predetermined environment, it is particularly preferable to periodically measure and maintain the temperature in a narrow area on the side of the machine tool M. At this time, the mobile temperature sensor 29 can be used to monitor the temperature of an arbitrary place in such an area with the tablet PC 34 or the monitor of the central monitoring room, so that the maintenance management work can be performed easily and reliably.

  Further, in a large space such as a metal processing factory where the machine tool M is frequently replaced and rearranged, the location of the waste heat changes each time. Therefore, the opening degree of the variable air volume device (VAV) 12 is adjusted and blown. Although it is necessary to perform an operation of adjusting the air volume from the outlet 13, by using the tablet PC 34 at this time, the opening adjustment operation of the variable air volume device (VAV) 12 can be simplified. Furthermore, by installing the variable air volume device (VAV) 12 and the air outlet 13 with sufficient capacity and number in advance, the variable air volume device (VAV) 12 can be used for large-scale rearrangement and expansion of equipment. It is possible to easily cope with this by simply adjusting the opening.

  In the above description of the embodiment of the present invention, the system is operated using the mobile temperature sensor 29 and the tablet PC 34, but without using these devices, the central monitoring device directly Needless to say, the system can be operated.

  Moreover, since the above description of the embodiment of the present invention describes a preferred embodiment of the air conditioning system for large spaces according to the present invention, technically such as the size of the large space and the capacity of the air conditioning equipment. Various preferred limitations may be given, but the technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. That is, the above-described components in the embodiment of the present invention can be appropriately replaced with existing components and the like, and various variations including combinations with other existing components are possible. The description of the embodiment of the present invention described above does not limit the contents of the invention described in the claims.

  The technology of the present invention is not limited to the above-described various factories such as metal processing factories, and the amount of heat generated from the equipment is considerably larger than the amount of cold heat per unit area, and the equipment etc. to maintain the indoor environment within a predetermined range. It is also expected to be used in buildings for other purposes such as data centers with large spaces where it is necessary to remove waste heat from the heating elements.

DESCRIPTION OF SYMBOLS 10 Air conditioning system for large spaces 11 Air conditioner 12 Variable air volume device 13 Air outlet M Machine tool (heating element)
S Large space Sa Air-conditioned space Sb Space outside air-conditioning management Z1-Zn zone

Claims (6)

An air conditioning system for a large space for cooling a large space where a heating element is installed to a constant temperature,
While cooling air is forcibly blown downward downward at a plurality of locations in the large space except directly above the heat generating portion of the heating element to reach the floor surface, the air heated by the heating element is An air conditioning system for a large space, which naturally rises linearly on an ascending airflow without colliding with the cooling air blown down.   The large space includes an air-conditioned space that needs to be maintained at a predetermined temperature, and an air-conditioning control outside space that is located above the air-conditioned space and does not need to be maintained at the predetermined temperature. The air conditioning system for large spaces according to claim 1.   In the space outside the air conditioning management, an air conditioner that forcibly sends the cooling air, a variable air volume device that adjusts the cooling air sent from the air conditioner to a predetermined air volume, and a predetermined air volume by the variable air volume device The air outlet according to claim 2, further comprising: a blowout port that blows out the cooling air adjusted to the air-conditioned space; and a suction port that sucks in air that has been naturally raised by being heated by the heating element. Air conditioning system for large spaces.   The air-conditioning system for large spaces according to claim 3, wherein the air-conditioned space has a plurality of zones divided into predetermined areas, and the air conditioner is provided for each zone.   The air conditioning system for large spaces according to claim 3 or 4, wherein the air for cooling is blown out from the air outlet so that an air velocity in the air conditioned space is a low speed of 0.6 m / s or less. .   The air conditioning system for a large space according to any one of claims 1 to 5, wherein the heating element is a machine having a rated heat generation amount per place of 5 to 30 kW and a change in the heat generation amount.

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