JPH0737610B2 - Latent heat storage type heating device and solid-liquid two-phase heat medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a latent heat storage type heating device of a heat storage material circulation system and a solid-liquid two-phase heat medium used for the same.

(Prior Art) In a conventional latent heat storage type heating device, a heat transfer method of separating a heat storage material and a heat medium through a heat transfer wall due to the peculiarities of the physical and chemical properties of the heat storage material. The mechanism is commonly used. FIG. 2 and FIG. 3 show an example thereof, and in the former (capsule type), a heat medium C such as air is circulated along the outer surface of the capsule B filled with the heat storage material A,
In the latter case (shell tube type), the heat storage material A
A heat medium C such as water is circulated in a tube D provided inside the heat storage body A to exchange heat between the heat storage body A and the heat medium C.

However, the capsule-type or shell-tube type heat exchange has a basic defect that the heat transfer coefficient in the heat transfer wall is low and it is difficult to increase the heat dissipation rate or the heat storage rate. This is a major obstacle to the practical application of.

For example, during heat dissipation, the solidified heat storage material adheres in layers on the heat transfer surface on the heat storage material side with the lapse of time, and the thickness thereof increases gradually. However, since the heat storage material itself has a relatively low thermal conductivity, its thermal resistance becomes a large value as the thickness of the solidified layer of the heat storage material increases. As a result, even if the heat storage amount of the heat storage material in the molten state is sufficient and the temperature difference between the heat storage material temperature and the heat medium is large, the heat transfer amount is extremely limited, and it is extremely difficult to increase the capacity of the heating device. Become.

On the other hand, in order to eliminate the above-mentioned heat transfer defects of the capsule type and shell tube type, a latent heat storage type heating device using a so-called active type heat exchange of a heat storage material circulation type as shown in FIG. 3 has been developed. ing. That is, the heat storage material A such as the molten salt stored in the tank E is used as the heat medium, and this is used as the circulation pump F.
It is configured to heat the water flowing in the tube H to obtain hot water (or steam) by sending it into the heat exchanger G by. In FIG. 3, I is a water pump, J
Is a heating source such as a heater.

In the latent heat storage type heating device of the heat storage material circulation system, since the heat storage material A is circulated and flowed at a constant flow velocity, the heat transfer tube H
It becomes difficult for the solidified layer of the heat storage material A to adhere to the outer surface of the. As a result, the heat transfer characteristics are considerably improved as compared with the case of the capsule type or shell tube type in which the heat storage material A is in a stationary state.

However, it is difficult to completely prevent the solidified layer of the heat storage material from being stuck and laminated on the outer surface of the tube H. Especially, when the circulation flow velocity of the heat storage material A as the heat medium is low, the solidified layer on the outer surface of the tube is not formed. The sticking of 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 material circulation type heating device, since the single-phase molten salt is used as the heat storage material A which is the heat medium, the melting temperature is 80 ° C to 200 ° C and the heat storage property is excellent. It is difficult to obtain a practical heat storage material A. As a result, there is a problem in that heated water or steam of about 80 to 200 ° C., which is required for cooling and heating equipment, etc., cannot be easily obtained.

(Problems to be Solved by the Invention) The above-mentioned problems in the conventional latent heat storage type heating device of the present invention, that is, in the heating device using the capsule-type or shell-tube type heat transfer mechanism, The heat resistance in the wall becomes extremely high, and it is difficult to obtain the necessary heat transfer characteristics. Also, in the heat storage material circulation type heating device, trying to obtain a high heat transfer coefficient increases the power cost of the circulation pump. , There is no practicable heat storage material A with a melting temperature of 80 to 200 ℃,
It aims to solve problems such as difficulty in obtaining heated water or steam at 0 ° C to 200 ° C, and highly efficient operation of water or steam at 80 ° C to 200 ° C with low power consumption. The present invention provides a latent heat storage type heating device of a heat storage material circulation system, which is easily available and enables the size of the device to be greatly reduced, and a solid-liquid two-phase heat medium used for the heating device.

(Means for Solving the Problem) The invention according to claim (1) is such that a heat storage tank equipped with a heating source and a particle size of 1.5 to 5.0 mm stored in the heat storage tank.
A solid-liquid two-phase heat medium having a mixing ratio of the surface-crosslinked polyethylene particles of φ and a heat-transfer oil or ethylene glycol liquid of 20 to 70 VoL%, a circulation pump for the solid-liquid two-phase heat medium, and the solid-liquid two-phase A heat exchanger that heats feed water by circulating a phase heat medium is a basic configuration of the invention.

Further, the invention according to claim (2) has a particle size of 1.5 to 5.0 mm.
It consists of a mixture of φ surface-crosslinked polyethylene granules and heat carrier oil or ethylene glycol liquid, and the mixing ratio of the surface cross-linked polyethylene granules and heat carrier oil or ethylene glycol liquid is set to 20 to 70 VoL%. This is a basic configuration of the invention.

(Function) By heating the solid-liquid two-phase heat medium at a predetermined temperature for a certain period of time with the heat source in the heat storage tank, the inside of the surface-crosslinked synthetic resin granules forming the solid phase of the heat medium is in the solid state. Causes a phase transition in a liquid phase, and the amount of heat corresponding to latent heat is stored inside the granules and sensible heat is stored in the heat medium and the granules.

The solid-liquid two-phase heat medium in which the latent heat storage is performed is circulated through the heat exchanger by the circulation pump, and gives the heat to the feed water through the finned heat exchange water pipe. Since the surface of the granules in the heat medium is cross-linked, the granules retain their shape even in the heat storage state and retain their original shape.

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

As mentioned above, the surface-crosslinked synthetic resin 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.

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

FIG. 1 is a system diagram of a latent heat storage type heating device according to the present invention. In the drawing, 1 is a heat storage tank, 2 is a heater which is a heating source of a heat storage material, 3 is a heat medium circulation pump, and 4 is heat exchange. Bowl, 5
Is a water pipe for heat exchange with fins, 6 is a water supply pump, 7 is an outlet for hot water (or steam), 8 is a pipeline, and K is a heat medium stored in the heat storage tank 1.

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

The solid phase component Kb of the heating medium K is composed of so-called surface-crosslinked synthetic resin particles obtained by crosslinking only the surface layer of the granular material such as polyethylene, polyester and polypropylene. In this embodiment, the diameter is 1.5 to 5 mmφ, the specific gravity is about 0.9 to 1.0, and the softening temperature is about 80 ° C.
Surface-crosslinked polyethylene having a latent heat of about 50 to 80 Kcal / kg at -20 ° C is used as the solid phase Kb of the heat medium. More specifically, the particle size of the surface cross-linked polyethylene is
It is optimal for heat transfer and circulation of heat medium K, and its softening temperature is about 133 ℃ and 188 ℃.
Practical tests were carried out on the two types.

Surface cross-linking of the polyethylene particles is carried out by a so-called electron beam irradiation method, etc. By the surface cross-linking treatment, only the surface layer portion of the polyethylene particles is slightly cured. 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, a heating medium oil or a liquid polymer material such as ethylene glycol or propylene glycol is used. In this embodiment, as the liquid phase component Ka of the heat medium, either heat medium oil or ethylene glycol is used according to the softening temperature of the surface-crosslinked polyethylene granules.

The material of the liquid phase component Ka of the heat 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 synthetic resin granules forming the solid phase component Kb. Need not to interfere. 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 cross-linked polyethylene granules having a softening temperature of about 133 ° C. are used as the solid phase component Ka, 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 mixing ratio (Kb / Ka) of the liquid phase component Ka and the solid phase component Kb constituting the solid-liquid two-phase heating medium K is about 20 to 70 VOL%, and about 50% is optimal in terms of heat transfer characteristics. Is.

Next, the operation of the latent heat storage type heating device according to the present invention will be described.

The heat medium K (solid phase Kb / surface cross-linked polyethylene, liquid phase Ka ethylene glycol) stored in the heat storage tank 1 is
The surplus power at night is used to heat the surface-crosslinked polyethylene at a softening temperature of about 133 ° C. or higher for a certain time by the heating source 2. 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,
The original shape is maintained), a heat amount corresponding to latent heat is stored, and so-called sensible heat storage is performed on the liquid phase component such as ethylene glycol.

By driving the heat medium circulation pump 3 and sending the solid-liquid two-phase heat medium K to the heat exchanger 4, heat exchange is performed with the water supply from the water supply pump 6 via the finned heat exchange water pipe 5. And
Hot water (or steam) is taken out from the outlet 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 stick to the outer surface of the heat exchange water pipe 5.

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.

(Effects of the Invention) In the present invention, the heat medium K is a solid-liquid two-phase fluid, and the solid phase is surface-crosslinked synthetic resin particles, so a large amount of latent heat is stored in the solid phase. As a result, the heat storage density of the heat medium rises, and the heat storage rate during heat storage also greatly improves.

Also, since the solid-liquid two-phase fluid is made to flow and the latent heat storage material is made of surface-crosslinked synthetic resin particles, the molten salt on the outer surface of the heat exchange water pipe of the heat exchanger as in the conventional molten salt circulation system. There is no possibility that the solid-phase component of will adhere and the heat transfer coefficient will deteriorate. As a result, it has been confirmed that the heat transfer coefficient is improved by about 3 times as compared with the case of the molten salt circulation method.

Furthermore, since the solid-liquid two-phase heat transfer medium is circulated by a pump while the latent heat storage material with a small particle size is suspended in the liquid phase component, it is possible to compare it with the conventional method of circulating molten salt in the form of slurry. As a result, the fluidity of the fluid is improved, and the pump power cost can be reduced.

In addition, the softening temperature of the surface cross-linked synthetic resin granules should be 80 ℃ ～ 20
By selecting around 0 ° C, high temperature water or steam can be easily obtained, and since the liquid phase of heat transfer oil etc. is normal pressure even at 100 ° C or higher, no pressure is applied to the heat storage tank, which is safe. It is also convenient in terms of efficiency and economy.

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

[Brief description of drawings]

FIG. 1 is a system diagram of a latent heat storage type heating device according to the present invention. 2 to 4 are explanatory views of a conventional latent heat storage type heating device. 1 ... Heat storage tank 2 ... Heating source 3 ... Heat medium circulation pump 4 ... Heat exchanger 5 ... Heat exchange water pipe K ... Heat medium Ka ... Liquid phase component Kb ... Solid phase component

Claims (2)

[Claims] 1. A heat storage tank equipped with a heating source, and a mixing ratio of a surface cross-linked polyethylene particle having a particle size of 1.5 to 5.0 mmφ and a heat transfer oil or ethylene glycol liquid stored in the heat storage tank to 20 to. Latent heat storage type heating device comprising a solid-liquid two-phase heat medium of 70VoL%, a circulation pump for the solid-liquid two-phase heat medium, and a heat exchanger for heating feed water by circulating the solid-liquid two-phase heat medium . 2. A mixture of surface-crosslinked polyethylene particles having a particle diameter of 1.5 to 5.0 mm and heat carrier oil or ethylene glycol liquid, wherein the surface-crosslinked polyethylene particles and heat carrier oil or ethylene glycol liquid. Mixing ratio 20-70VoL
%, And a solid-liquid two-phase heat medium for a latent heat storage type heating device.