JPH0823449B2 - Heat storage type electric hot water / steam generator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a heat storage type electric hot water / steam generator.

(Prior Art) The conventional latent heat storage type electric hot water / steam generator is usually the fifth type.
As shown in the figure, a latent heat storage material A such as molten salt is stored in a heat medium tank E provided with a heating source J such as a heater, and the heat storage material A is heated by using nighttime electric power to make it into a molten state. So-called latent heat storage is performed, and hot water or steam is obtained by sending feed water into the heat exchanger H provided in the heat medium tank E and heating it.

However, in the electric hot water / steam generator having the configuration shown in FIG. 5, since the heat transfer coefficient in the heat transfer wall portion of the heat exchange tube H is low, the heat dissipation rate from the heat storage material A to the water supply becomes extremely slow. ,
There is a fundamental drawback that it is difficult to downsize the hot water / steam generator.

For example, during heat dissipation, the solidified heat storage material A adheres to the outer surface of the heat exchange tube H in a layered manner, and its thickness gradually increases over time. However, since the heat storage material itself has a relatively low thermal conductivity, the thermal resistance thereof remarkably increases as the thickness of the solidified layer increases. As a result, the heat transfer to the water supply cannot be performed smoothly, which inevitably leads to an increase in the size of the hot water / steam generator.

On the other hand, in order to solve the above problems, an electric hot water / steam generator using a so-called active heat exchange system of a heat storage material circulation type as shown in FIG. 6 has been developed. That is, the heat storage material A such as molten salt stored in the heat medium tank E is used as a heat medium, and this is sent into the heat exchanger G by the circulation pump F to heat the water flowing in the heat exchange pipe H. It is configured to obtain hot water (or steam). In FIG. 6, I is a water feed pump and J is a heat medium heating source such as a heater.

In the latent heat storage type electric hot water / steam generator of the heat storage material circulation system, since the heat storage material A is circulated and flowed at a constant flow velocity,
It becomes difficult for the solidified layer of the heat storage material A to adhere to the outer surface of the heat exchange tube H. As a result, the heat transfer characteristics are also considerably improved as compared with the case where the heat storage material A is stationary.

However, even in the heat exchange of the heat storage material circulation system, it is difficult to eliminate the solidified layer of the heat storage material on the outer surface of the heat exchange tube H.
If the circulation flow rate is low, the adherence of the solidified layer to the outer surface of the tube is significantly increased. As a result, in order to maintain high heat transfer characteristics, it is necessary to considerably increase the circulation flow velocity of the heat storage material A, and the molten salt that is the heat storage material is in the form of slurry and its fluidity is relatively low. Therefore, the power cost of the circulation pump F will increase significantly.

Further, in the conventional heat storage type electric hot water / steam generator, the heat dissipation rate of the heat storage material A is low even if the hot water / steam load is temporarily increased and a peak load is applied to the generator. In addition, there is a problem that it is not possible to properly respond to this, and when the heat storage amount of the heat storage material A itself is insufficient, it is not possible to meet the load demand at all.

(Problems to be Solved by the Invention) The present invention has the above-described problem in the conventional heat storage type electric hot water / steam generator, that is, since the heat transfer coefficient of the heat exchange tube H is low, it responds to a change in load. Performance is poor and the device cannot be downsized. Even when the heat storage material circulation type is used, the heat transfer coefficient is relatively low, the power cost of the circulation pump increases, and the peak load is applied to the generator. Even if
Since the heat dissipation rate of the heat storage material is low, it is not possible to respond quickly, and in the unlikely event that the load increases and the amount of heat storage becomes insufficient, the hot water / steam generator becomes completely unusable. The problem is to be solved, and the heat storage type hot water / steam generator is configured to combine heating by heat dissipation from the heat storage material A and heating by an electric heater, and
By providing a solid-liquid two-phase heat medium with a completely new structure as a heat storage material, it is possible to provide a heat storage type hot water / steam generator capable of handling both base load and peak load as necessary and sufficient. is there.

(Means for Solving the Problems) The invention according to claim 1 of the present application provides a heater 2 for heating a heat medium.
A heat storage tank 1 equipped with the above, a surface cross-linked polyethylene particle Kb having a particle size of 1.5 to 5 mmφ, and a heat transfer oil or ethylene glycol Ka are mixed in the former ratio Kb / Ka to the latter in the range of 20 to 70 VoL%. And a solid-liquid two-phase heat medium K stored in the heat storage tank 1 and a heat exchange water pipe 5a, and a heat exchanger 4a for heating the feed water by the solid-liquid two-phase heat medium K flowing at peak load, A heat exchanger having a heat exchange water pipe 5b provided therein with a heater 10 for heating the feed water at a steady load, and heating the feed water by a solid-liquid two-phase heat medium K flowing at a peak load.
4b, a circulation pump 3 for the solid-liquid two-phase heat medium K that operates at the time of peak load, a water exchange pump 5b or a water exchange pump 5 for supplying water to the heat exchange water pipe 5a and the heat exchange water pipe 5b, and the heat exchange The water supply pipe 5b or the heat exchange water pipe 5a and the steam separator 7 that receives heated water from the heat exchange water pipe 5b are the basic constitution of the invention.

(Function) By heating the solid-liquid two-phase heat medium in the heat storage tank or tank main body with the heater for heating the heat medium, the inside of the surface-crosslinked polyethylene granules forming the solid phase of the heat medium changes from the solid phase to the liquid phase. A phase transition occurs in the and the amount of heat equivalent to the latent heat is stored inside the granules.

The solid-liquid two-phase heat medium in which the latent heat is stored is flowed by the circulation pump or stirred and flowed by the stirring device, and the heat retained through the heat exchange water pipe is applied to the feed water.

Since the surface of the particles in the heat medium is cross-linked, the particles have a shape-retaining property even in a heat storage state and retain the original shape.

Due to the heat exchange, the particles in the heat medium release their latent heat, the internal liquid phase changes to a solid phase, and the particles are sequentially returned to the heat storage tank.

As mentioned above, the surface-crosslinked polyethylene granules retain their original shape even under heat storage conditions, so that they do not stick to the outer surface of the heat exchange water pipe at all, and the heat transfer coefficient Is significantly improved.

In the hot water / steam generator according to claim (1), the heating by the heaters for heating feed water arranged in parallel and the heating by the stored heat medium are appropriately operated according to the hot water / steam load, For example, the normal load is shared by heating with a heating medium, and the peak load is shared by the operation of the feed water heating heater.

The same applies to the hot water / steam generator according to claim (2), and the peak load is dealt with by appropriately operating the heater for heating the heat medium other than during heat storage.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 is a heat storage type electric hot water according to the first embodiment of the present invention.
FIG. 2 is a system diagram of a steam generator, and FIG. 2 is a cross-sectional view showing another example of the heat exchanger used.

In the figure, 1 is a heat storage tank, 2 is a heater for heating a heat medium, 3 is a heat medium circulation pump, 4a and 4b are heat exchangers, and 5a and 5b.
Is a fin heat exchange water pipe, 6 is a water supply pump, 7 is a steam separator, 8 is a pipe line, 9 is a control device, 10 is a sheath heater for heating the water supply, 11 is a pressure regulator, 12 is a water supply gauge, K
Is a heat medium stored in the heat storage tank.

The heat medium K is a so-called solid-liquid two-phase fluid, and flows in the pipe 8 and the heat exchanger 4a in a state where the solid phase Kb is mixed in the liquid phase Ka.

The solid phase Kb of the heating medium K is composed of so-called surface-crosslinked polyethylene granules obtained by crosslinking only the surface layer portion of polyethylene granules. In this embodiment, the diameter is 1.5 to 5 mmφ and the specific gravity is about 5.
0.9-1.0, softening temperature about 80 ℃ -200 ℃, latent heat about 50-80Kcal /
kg of surface-crosslinked polyethylene is used as the solid phase Kb of the heat medium. More specifically, the particle size of the surface-crosslinked polyethylene granules is optimally in the range of 1.5 to 3 mmφ in terms of heat transfer and circulation flow of the heat medium K, and its softening temperature is about 133 ° C. and 188 ° C. Practical tests were carried out on two types of materials at temperatures of ° C.

Surface cross-linking of the polyethylene granules is performed by a chemical method, an electron beam irradiation method, or the like, and the surface cross-linking treatment slightly cures only the surface layer portion of the polyethylene granules. As a result, even if the inside of the granule is in a molten state under heating, the surface layer portion thereof remains in a solidified state and maintains the shape of the granule. Even if the surface cross-linking treatment is applied, the latent heat of polyethylene is not significantly reduced.

On the other hand, for the liquid phase component Ka of the solid-liquid two-phase heating medium K, either heating medium oil or ethylene glycol is used depending on the softening temperature of the surface-crosslinked polyethylene granules.

The material of the liquid phase component Ka of the heating medium K must have a specific gravity such that the solid phase component Kb can float, and further, the stability of the surface layer portion of the surface-crosslinked polyethylene granules forming the solid phase component Kb can be improved. It is necessary not to block. In addition, the liquid phase component Ka is preferably a substance having excellent chemical stability and fluidity and a large heat capacity.
Taking these points into consideration, in the present embodiment, as described above, when the surface-crosslinked polyethylene granules having a softening temperature of about 133 ° C. are used as the solid phase component Kb, ethylene glycol is added, and the softening temperature is about
When the surface-crosslinked polyethylene granules at 188 ° C. are used as the solid phase component Kb, the heat transfer oil is used as the liquid phase component Ka respectively.

The liquid phase component Ka and the solid phase component Kb constituting the solid-liquid two-phase heat medium K
Mixing ratio with (Kb / Ka) is about 20-70 VOL%, 50%
The degree is optimal in terms of heat transfer characteristics.

The seed heater 10 for heating the feed water directly heats the feed water through the finned heat exchange water pipe 5b of the heat exchanger 4b, and in this embodiment, as described later, the heater 10 is normally used. The load (base load) is shared, and the peak load is also shared by the heat storage amount of the heat medium K in the heat storage tank 1.

In this embodiment, the base load is shared by the heater 10 as described above, but the heat medium K may share the base load and the heater 10 may share the peak load. Further, in the present embodiment, the heat exchanger 4b having the heater 10 for heating the feed water and the heat exchanger 4a in which the solid-liquid two-phase heat medium K circulates are separately provided, respectively, but shown in FIG. As described above, the sheathed heater 10 for heating the feed water is inserted into the inside of the fin-equipped heat exchange water pipe 5a, and the gap between the heater 10 and the water pipe 5a is used as the water supply passage, so that one heat exchanger is provided. It may be a combined configuration.

Next, the operation of the heat storage type hot water / steam generator will be described.

Heat medium K stored in the heat storage tank 1 (solid phase Kb, surface cross-linked polyethylene, liquid phase Ka ethylene glycol, etc.)
Is heated at a softening temperature of the surface cross-linked polyethylene of about 133 ° C. or about 188 ° C. for a certain period of time by the heater 2 by using surplus power at night. As a result, the inside of the surface-crosslinked polyethylene granules becomes in a molten state (the outer surface layer of the particles is slightly softened, but the original shape is maintained), and the amount of heat corresponding to latent heat is accumulated and the ethylene glycol So-called sensible heat storage is performed in the liquid phase components such as.

The hot water (or steam) is generated in the daytime by the operation of the heater 10 for heating the water supply, and the heater 10, the water supply pump 6 and the like are controlled via the water supply gauge 12, the pressure regulator 11 and the control device 9. .

On the other hand, when the steam load or the like suddenly increases, the heat medium circulation pump 3 is driven and the solid-liquid two-phase heat medium K is sent to the heat exchanger 4a, so that the water supply pump via the finned heat exchange water pipe 5a. The feed water from 6 is heated and the heated water is sent to the steam separator 7.

Even if the inside of the polyethylene particles in the heating medium K is melted, the outer surface layer is in a solidified state and maintains the particle shape. Therefore, the solid phase does not adhere to the outer surface of the heat exchange water pipe 5a at all.

The polyethylene particles, which have released latent heat by heat exchange, are returned to the heat storage tank 1 through the conduit 8 in a state where the inside thereof undergoes a phase transition to a solid phase and is suspended in the liquid phase component Ka.

3 and 4 are a horizontal sectional view and a vertical sectional view showing a second embodiment of the present invention.

In this embodiment, the heat storage tank and the heat exchanger are integrally formed, and the solid-liquid two-phase heat medium K is forcibly stirred in the tank body 13 by the stirring device 14.

That is, the tank body 13 is formed in a sealed structure including the water pipe wall 15. The upper and lower ends of each water pipe 15a forming the water pipe wall 15 are connected to an upper header 16 and a lower header 17, respectively, and water is supplied from the water supply pump 6 to the lower header 17. Further, a plurality of sheath heaters 2 for heating the heat medium and stirring blades 14a forming a stirring device 14 are arranged inside the tank main body 13, respectively, and a solid-liquid two-phase heating medium K is supplied by night power or the like. Is heated by the heater 2 while being stirred, and heat is stored.

The solid-liquid two-phase heat medium K is a mixture of surface-crosslinked polyethylene particles and heat transfer oil or ethylene glycol as in the case of the first embodiment, and latent heat is stored in the polyethylene particles. Further, in FIG. 3 and FIG. 4, 14b is a drive motor for the stirring device, 18 is a power supply line, 19 is hot water / steam extraction port, and 20 is a heat insulating material.

The water supply supplied from the water supply pump 6 into the water pipe 15a is heated by heat exchange with the solid-liquid two-phase heat medium K flowing by stirring, and becomes hot water (or steam) from the outlet 19 and flows out of the tank. . As described above, the solid phase component (polyethylene granules) Kb in the solid-liquid two-phase heat medium K has its outer surface layer portion in the solidified phase even during heat storage, and as a result, adheres to the outer surface of the water pipe 15a. There is no stacking and heat exchange is performed with a high heat transfer coefficient.

The power supply to the heat medium heating heater 2 does not have to be limited to power supply only at night, and when the steam load or the like rapidly increases, the heater 1 is operated to supply water through the heat medium K that stirs and flows. It is also possible to accelerate the heating of the.

(Effects of the Invention) In the present invention, the heating of the feed water by latent heat storage and the heating of the feed water by the electric heater can be used together, so that a quick response to a peak load can be achieved. In addition to being able to do so, it is possible to avoid all the various inconveniences due to insufficient heat storage.

Further, since the heat medium is a solid-liquid two-phase fluid having surface-crosslinked polyethylene particles as the solid phase component, a large amount of latent heat can be stored in the solid phase component, and the heat storage density of the heat medium is significantly improved.

Furthermore, since the solid-liquid two-phase heat medium is made to flow and the solid phase portion is made of surface-crosslinked polyethylene granules, the solid phase of the molten salt is formed on the outer surface of the heat exchange water pipe like the conventional molten salt circulation system. There is no possibility that the heat transfer coefficient will be deteriorated due to the fixed amount, and the heat transfer coefficient will be improved by about 3 times as compared with the case of the molten salt circulation system. As a result, it is possible to significantly reduce the size of the hot water / steam generator.

In addition, the solid-liquid two-phase heat medium is circulated by a pump or made to flow by a stirring blade in a state in which a latent heat storage material having a small particle size is suspended in the liquid phase component. The fluidity of the fluid is improved and the pump power cost can be reduced as compared with the case where the fluid is circulated or stirred.

Moreover, by selecting the softening temperature of the surface-crosslinked polyethylene granules in the heating medium to about 80 to 200 ° C, high-temperature water or steam can be easily obtained, and the liquid phase content of the heating medium oil, etc.
Since the pressure is not applied to the heat storage tank or the main body of the tank because it is normal pressure even at 100 ° C or higher, it is convenient in terms of safety and economy.

As described above, the present invention has excellent practical utility.

[Brief description of drawings]

FIG. 1 shows a heat storage type electric hot water according to the first embodiment of the present invention.
It is a system diagram of a steam generator. FIG. 2 is a sectional view showing another example of the heat exchanger used in the first embodiment. 3 and 4 are a horizontal sectional view and a vertical sectional view of a heat storage type electric hot water / steam generator according to a second embodiment of the present invention. 5 and 6 are schematic explanatory views of a conventional heat storage hot water temperature air temperature water / steam generator. 1 …… Heat storage tank 2 …… Heater for heating heat medium 3 …… Heat medium circulation pump 4a ・ 4b …… Heat exchanger 5a ・ 5b …… Water pipe for heat exchange 6 …… Water supply pump 7 …… Steam separator 10 …… Heater for supplying water 13 …… Bath body 14 …… Stirring device 15 …… Water pipe wall K …… Solid-liquid two-phase heat medium

Claims (1)

[Claims] 1. A heat storage tank (1) equipped with a heater (2) for heating a heat medium, surface-crosslinked polyethylene particles (Kb) having a particle size of 1.5 to 5 mmφ, and a heat transfer oil or ethylene glycol (K).
a) and the ratio (Kb / Ka) of the former to the latter is 20-70VoL%
And a solid-liquid two-phase heat medium (K) stored in the heat storage tank (1) and a water pipe (5a) for heat exchange, and flowing at peak load. (K) is equipped with a heat exchanger (4a) that heats the feed water, and a heat exchange water pipe (5b) that internally has a heater (10) that heats the feed water during a steady load. A heat exchanger (4b) for heating the feed water with a phase heat medium (K), a circulation pump (3) for the solid-liquid two-phase heat medium (K) that operates at peak load, and the heat exchange water pipe (5b) Alternatively, a water supply pump (6) for supplying water to the heat exchange water pipe (5a) and the heat exchange water pipe (5b), and the heat exchange water pipe (5b) or the heat exchange water pipe (5a) and the heat exchange water pipe (5b). Regenerative electric hot water / steam comprising a steam separator (7) for receiving heated water from Generator.