JPH0438998B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] Latent heat storage devices with non-decomposable molten substances are effective systems for relieving or supplementing the load on conventional energy generation systems and adjusting the temporal fluctuations between energy generation and energy demand. . Therefore, the latent heat type heat storage device according to the present invention is particularly designed to adjust the heat consumption system to the usage conditions of the amount of heat determined by the energy source, that is, to temporally adjust the amount of heat generation and the amount of heat demanded. and used to store heat. Characteristics of prior art solutions Typical heat storage devices operate primarily on the basis of detectable heat. The heat storage materials used for this purpose, such as water, oil, rock, cast iron, magnesite, and soil, all have low heat capacity, so if such a heat storage system is used, especially when storing a large amount of heat, an abnormally large amount of heat will be required. This becomes a heat storage volume, resulting in an uneconomical waste situation. From a practical point of view, conventional heat storage systems have the following important drawbacks: − The heat storage and heat dissipation of the heat storage device will lead to the increase or decrease of the heat storage temperature, which is actually very disadvantageous during heat storage and release, but it is possible to constantly change the heat storage temperature and heat transfer efficiency, and reduce the cost of the control technology to be adopted. This will result in an increase. - Due to the low heat capacity common to heat storage materials, the weight/power ratio is very unfavorable compared to the latent heat storage devices described below. - the storage of a large amount of heat is associated with a large volume of the heat storage device, which is often not possible with today's technology or can only be realized at great expense (construction of auxiliary buildings);
or have a very unfavorable cost impact. − In order to reduce the heat storage volume to a technically feasible extent, it is necessary to allow large temperature differences between heat storage and heat dissipation conditions, in which case the required heat storage temperature can be reduced to the required operating temperature of the heat dissipating system. higher than that,
This means that we have to accept that the energy characteristics (heat storage amount) of the heat source are nullified. − When water is used as the most frequently used heat storage material, the storage temperature required for industrial applications in particular must be at an upper temperature limit of 90-70°C for heating equipment (approximately 90°C at normal pressure). ), if
It is particularly important to store large amounts of energy. Increasing the heat storage capacity by increasing the water temperature is not possible at normal pressure and leads to large technical and equipment expenditures, further exacerbating an otherwise disadvantageous cost situation. The possibility of overcoming these drawbacks is based less on detectable heat and more on latent heats such as heat of solution, heat of solidification, heat of vaporization, heat of condensation, heat of reaction, heat of hydration, heat of solution, heat of crystallization, etc. provided by a thermal storage device that operates based on This type of heat storage device is referred to as a "latent heat storage device" in the literature.
It is called. These heat storage devices have the following drawbacks compared to normal heat storage devices. - When performing heat storage and heat dissipation, the heat storage temperature is maintained constant within a narrow range during heat absorption or heat dissipation. − The heat transfer efficiency is also kept constant within a narrow range depending on each technological solution. - Compared to conventional heat storage devices, the heat absorption capacity is 2 to 40 times greater, depending on the heat storage material used and the width of the total temperature range in which heat absorption and heat release occur. The most obvious improvement is in latent heat storage devices, in particular those operating on the basis of the heat of fusion and solidification. There are a range of solutions for such heat storage devices that involve fusible materials and eliminate the well-known thermophysical and physicochemical problems. These solutions include West German Patent No. 2648678,
East German Patent No. 154125, West German Patent No. 1928694, West German Patent No. 2523234, West German Patent No. 2517920 and West German Patent No. 2517921, and East German Economic Patent Application WP
C 09K/243619 belongs to this patent. These disclose improvements regarding selection of heat storage materials, suppression of supercooling, stratification, etc. The following issues are still unresolved. Various molten substances that melt non-decompositionally, e.g. in the eutectic or isocratic state, have a tendency for the crystals formed to form bulky agglomerates when solidified, a tendency to produce significantly reduced heat transfer efficiency as heat enters and exits, and coatings. There is a tendency for formation, impermeability of the melt, thermal stress and pressure build-up inside the heat storage device. Furthermore, it is known from the literature that the addition of fluorine-containing surface-active substances can reduce the size of crystals that form when Glauber's salt (Na ₂ SO ₄ .10H ₂ O) molten in a non-isocratic state solidifies. ing. This corresponding patent is US Pat. No. 4,267,879. On the other hand, there is no known concrete solution for reducing the crystal grain size of a heat storage material that melts without decomposition (eg, isocratic). The transition to isocratic melting materials such as Na ₂ S.5H ₂ O has not been successful. [Object of the Invention] The object of the present invention is to provide a non-decomposable molten material that prevents large volume agglomerates, film formation and impermeability from occurring, and at the same time increases heat dissipation and heat absorption efficiency, without using mechanical means. An object of the present invention is to provide a latent heat type heat storage device having the following properties. [Description of the essence of the invention] A latent heat storage device having a non-decomposed molten material, such as a material that melts in an isocratic state and a eutectic state, when solidified, forms crystals that form agglomerates with a large volume. Tend. This means low heat dissipation and
This causes heat absorption efficiency and thermal stress inside the heat storage device. In order to suppress the above-mentioned difficulties, this invention provides four
This is done by means of an active heat storage filling consisting of a type of material. Substance system Consists of one or more substances that exhibit heat storage properties due to heat of fusion (or general heat of conversion) and significant heat capacity, are non-decompositionally molten, and can be employed as heat storage materials. The proportion of the material system in the total volume of the active heat storage filling amounts to 50 to 95 vol.% in the present invention. Substance System The substance system consists of a liquid heat transfer medium composed of one or more components which are insoluble or only soluble to a limited extent. in this case,
According to the present invention, the density of the material system (ρ _II ) and the density of the molten liquid phase of the material system (ρ _I ) satisfy the condition ρ _I ≦ρ _II , for example, 0.8ρ _I , and the vapor pressure P of the material system According to this invention, _DI and the vapor pressure P _DII of a material system satisfy the condition of P _DI <<P _DII . The proportion of the material system is between 5 and 50 vol% relative to the total volume of the active heat storage filling of the heat storage device. Material system Consisting of one or more surface-active substances. The proportion of the material system to the total volume of the active heat storage filling of the latent heat storage device is 0.01 to 5 vol%. The material system has the role of preventing the formation of microcrystals and preventing growth and film formation when the material system solidifies. Material system Consists of one or more nucleators that induce nucleation phenomena due to their lattice structure or initiate heterogeneous nucleation. According to the invention, the proportion of the material system to the total volume of the active heat storage fill of the latent heat storage device is 0 to 20 vol%. If the material system is supercooled or slightly supercooled, the ratio of material system to active heat storage filling is zero. [Example] The latent heat type heat storage device according to the present invention will be explained based on the following 13 types of variations of three types of heat storage fillers.

【table】

[Table] The effects of these material systems will be explained based on a latent heat type heat storage device having the basic structure shown in FIG. The four material systems are filled in a thermally insulated pressure vessel as a mixture with an active heat storage fill.
The introduction of heat takes place via a heat transfer device 3 surrounded by a heat storage filling, and the release of heat takes place via a heat transfer device 4 surrounded by vapor of a heat transfer medium.
Heat transfer proceeds through three types of phase transformations. If heat above the melting temperature is introduced, the material system will vaporize. When it encounters an unmolten substance in a system of matter, the system condenses and melts the system of matter. The heat of condensation released from the material system is received by the material system as heat of fusion. If heat is released below the melting temperature, the material system is vaporized again, in this case at a lower pressure than when the heat is introduced. The heat of vaporization required for this is extracted from the heat storage material (material system). This material then solidifies. The vapor of the material system condenses in the heat transfer device 4, and the resulting heat of condensation is received by this heat transfer device. The heat transfer takes place in both cases with intensive mixing of the heat storage filling and significant foam formation. A uniformly distributed heat reception and release throughout the heat storage material therefore occurs. This process, which is known per se, proceeds in the case of non-decomposed molten substances, with the formation, growth and stratification of large volume agglomerates in the absence of a substance system. Addition of the substance system prevents the above situation. Depending on the intensity of the foam formation and the amount of material system, small crystals form which form coarse permeable gaps inside the heat storage device. A material system is needed to initiate crystal formation and prevent supercooling when heat is extracted. Other embodiments can be realized using the following non-decomposable molten materials as material systems. -KF.2H2O _{-Na2S2O3.5H2O -CH3COONa.3H2O The} heat accumulating substance ₍ substance system ₎ determines _the main component of this active heat storage _filling . The quality of the material system is selected according to the criterion condition: −ρ _II <ρ _I −P _DI ≪P _DII − The substances do not mix, so the active heat storage filling described in the claims becomes.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a latent heat type heat storage and transmission according to an embodiment of the present invention. Reference symbols in the figure: 1... Container, 2... Filling containing four types of material systems, 3... Heat transfer device for heat supply,
4... Heat transfer device for heat extraction, 5... Hollow chamber.

Claims (1)

[Scope of Claims] 1. A latent heat storage device having an active filling to be mixed with a non-decomposed molten substance in a closed heat storage container, wherein the active filling has a substance system, and optionally, - the system of matter consists of one or more heat storage substances that are molten in a eutectic or isocratic state and represent 50 to 95 vol% of the total volume of the heat storage filling; does not melt, is in the molten phase with the condition ρ _II > ρ _I , satisfies P _DI ≪ P _DII , and consists of a heating medium that is 3 to 50 vol% of the total volume of the heat storage filling, - the material system is the heat storage filling 0.01 of the total volume of
5 vol% of surface-active substances;
At 20vol%, if the material system is not supercooled,
A latent heat type heat storage device characterized in that the nucleation material is 0vol%.