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THERMAL DEVICES, DEVICES FOR HEATING LIQUID MEDIA AND THEIR APPLICATION
INVENTION
Patent of the Russian Federation RU2088857

HEAT EXCHANGING ELEMENT AND THERMAL BATTERY BASED ON ITS BASIS

THERMAL-CONTAINING ELEMENT AND THERMAL BATTERY BASED ON ITS BASIS

The name of the inventor: Vladimir V. Bulychev; Yemelyanov Yevgeny Stefanovich; Zagryazkin Valery Nikolaevich; Makovetsky Alexander Viktorovich; Stepanov Viktor Sergeevich
The name of the patent holder: Vladimir V. Bulychev; Yemelyanov Yevgeny Stefanovich; Zagryazkin Valery Nikolaevich; Makovetsky Alexander Viktorovich; Stepanov Viktor Sergeevich
Address for correspondence:
Date of commencement of the patent: 1993.07.16

Usage: for accumulation of heat of phase transition in thermal accumulators for heating of premises. SUMMARY OF THE INVENTION: The heat storage element is made in the form of a block with ducts of a composite material containing a substrate of heat-resistant ceramics in which granules are distributed from an hypereutectic aluminum-silicon alloy. The composite material is in particular made on the basis of magnesium oxide with granules of an aluminum-based alloy with 12.5-25.0% by weight silicon with a granular content of up to 30-70% (by volume). The heat-storage element described is used as a thermal battery base and fixed inside a monolithic block of highly porous concrete based on a material selected from the group of mullite, forsterite, chamotte, perlite, vermiculite. The assembly of one or more monolithic blocks is thermally insulated in a metal container with double walls, the space between which is filled with highly effective thermal insulation, and can be used to organize channels for natural or forced convection of the coolant.

DESCRIPTION OF THE INVENTION

The invention relates to the field of heat supply and can be used for heating and hot water supply of residential and industrial premises.

It is known to perform a heat-storage element in the form of a capsule filled with a eutectic mixture of salts melting in the operating temperature range. Capsules are placed in a common thermally insulated container. For the organization of heat supply to the charge-discharge heat exchanger and the removal of heat from it by evaporation-condensation, a separate heat carrier is used (Beckman, G. Gilli, P. Thermal accumulation of energy, M. Mir, 1987, p. 64).

An electric heater is also known, comprising a housing divided by a transverse perforated partition into the upper and lower chambers, the first of which is provided with a supply pipe for the heated heating medium, and the latter is filled with a heat-accumulating substance with a phase transition in the operating temperature zone and is provided with an electric heating element. The electric heater is provided with an additional transverse partition placed in the upper chamber with the formation between the additional and perforated partitions of the cavity, the volume of which is equal to the difference in the volumes of heat-accumulating substance in the solid and liquid states at the melting temperature of the heat-storage substance. After the electric heating element is turned on, heating of the heating medium (water) begins only after the heat-accumulating substance has completely melted. After the electric heating element is turned off and the hardening of the substance begins, an air gap forms in the cavity, preventing heat from being drawn to the heat carrier, which increases the uniformity of heating the room through the side walls of the housing. As a melting agent, paraffin is suggested.

On the basis of this electric heater, a heating system has been built in which the individual electric heaters can be switched on both in their nominal position and rotated 180 ° relative to their horizontal axis. Connection of electric heaters is carried out by pipes with the help of connecting couplings. The electrical connection is carried out by threaded couplings (Aut.N. 1688071 AI, MCI 5 F 24H 7/00, 1/20 of 30.10.91).

The drawbacks of the known design include low efficiency of supply and removal of heat due to low thermal conductivity of paraffin both in solid and liquid states, which limits the geometric dimensions of the heater. The limitations on the maximum dimensions imposed by the low thermal conductivity of paraffin, together with the low heat of fusion of 40 kWh / m 3 at a temperature of about 60 ° C, result in a high material consumption and low efficiency of the heating system as a whole for heating the living quarters.

The task of the authors is to increase the specific capacity of a single heat-accumulating element and, as a result, reduce the cost of manufacturing and increase the efficiency of operation of a thermal battery created on its basis.

To solve the problem, the authors propose a heat storage element to be made in the form of a cylinder with a through central hole from a composite material containing a base of heat-resistant ceramics in which granules are distributed from hypereutectic alloys based on aluminum and silicon. This heat-accumulating element can be made either monolithic or as the sum of individual blocks. The compositions of heat-resistant ceramics and granules must be matched both in compatibility in the operating temperature range and in terms of thermal expansion coefficients (CTE). In particular, for heat accumulators based on Al Si alloys designed for heating living quarters, the minimum melting temperatures in the Al Si system, which are 577-700 ° C, are the most convenient as operating temperatures, which corresponds to the composition of the alloy with 12.5-25 mass% . Silicon, and the closest in KTP ceramics for these alloys is a ceramics based on magnesium oxide.

One of the main technical problems associated with the creation of thermal accumulators, based on the proposed high-temperature elements, is the problem of high-efficiency thermal insulation. In the proposed thermal battery design, the thermal insulation, in particular as an option, can be made in the form of three layers. The first layer is made of heat-resistant highly porous concrete, in which a heat storage element or a group of heat storage elements is fixed. Based on the functional purpose and temperature conditions of operation, in particular, the concrete of cheap materials with low intrinsic specific density and thermal conductivity of materials such as mullite, forsterite, dinas, chamotte, vermiculite with a porosity of 50-70% can be used as the material of the first layer. In doing this Layer of heat insulation in the form of a rectangle in the section by placing one heat-insulated block on the other, it is possible to organize a multi-element thermal battery.

The assembly thus obtained, consisting of one or more heat-storage elements with thermal insulation from porous concrete, is fixed through heat-insulating gaskets in a metal container with double walls. The space between the heat-accumulating assembly and the inner walls of the metal container is filled with highly effective thermal insulation, for example on the basis of mineral wool. The space between the inner and outer metal walls is the third thermal insulation layer and, depending on the capacity of the thermal battery, is used to organize natural or forced convection of the coolant. As the heat carrier, air and / or water can be used first.

In particular, natural air convection is realized by arranging through channels at different levels with an adjustable cross-section for controlling the power of the heat sink. Forced convection is carried out by an additional installation of micro-fans at the air inlet to the heat accumulator.

For large heat capacity devices, water heat exchangers (coils) with natural or forced circulation of water can additionally be inserted into the space between the inner and outer metal walls.

Additionally, at the top, the heat accumulator can have a removable heat-insulating cover covering the flat radiator serving for cooking.

The proposed design significantly increases the specific capacity of the heat-storage element. Thus, for example, for an element with an outer diameter of 100 mm, an inner diameter for an electric heater of 15 mm, and a total length of 650 mm made of a magnesium oxide composite material with 50% by volume of granules from an hypereutectic Al + 12.5 wt. Si, the heat storage capacity is 2.7 kWh in the operating temperature range 300-700 o C. Assembly of four such elements will have a capacity of 10 kWh, and the heat accumulator as a whole will have external dimensions (approximately) 1000х1000х400 mm. Taking into account the small values ​​of the densities of the materials used (~ 2.5 3.0 g / cm 3 ), the specific heat dissipation in relation to the active part of the thermal battery is 0.2 kWh / kg or 0.6 kWh / dm 3 .

High thermal conductivity of the composite materials used (~ 100 W / m o K) allows, if necessary, to increase the single capacity of the TA without any restrictions, and the multilayer thermal insulation design provides an effective limitation of the temperature of the external heat-dissipating surfaces.

The design of the heat accumulator is shown in the drawing.

THERMAL-CONTAINING ELEMENT AND THERMAL BATTERY BASED ON ITS BASIS

It consists of heat-storage elements 1 made of a composite material consisting of refractory ceramics and Al-Si alloy beads, a tubular electric heater 3 is inserted into the through central hole 2. A monolithic block of highly porous concrete 4 serves as the first layer of thermal insulation. The assembly of the heat-storage elements is fixed in a metal container with double walls 5 and 6. The space between the assembly and the walls of the metal container is filled with highly effective heat insulation 7. In the space between the inner and outer metal walls, channels for removing the stored heat with air 8 and / or Water 9. At the top of the heat accumulator is a heat-insulated detachable cover 10, which opens access to a flat radiator 11 serving for cooking.

The thermal battery operates as follows. When power is connected to electric heaters, heat is generated in them, which is transferred to the surrounding composite material of the heat storage element. Material, having a high thermal conductivity, quickly warms up. The granules that form part of it are melted. At the same time, the heat of fusion accumulating from 100 to 300 kWh / m 3 of thermodynamically highly effective energy is accumulated, depending on the volume fraction of Al-Si-alloy pellets in the composition of heat-storage elements without taking into account the internal heat content. After their complete melting, the process of heat accumulation ends and the electric heaters are switched off. The stored heat is transferred to the room through layers of thermal insulation and radiated predominantly by the front panels. If necessary, increase the heat flow using air cooling channels and / or water radiators. As the stored heat is consumed, the Al-Si alloy granules solidify toward the center of the heat-storage element. After the granules have completely hardened, the heat accumulator is ready for a second cycle.

This heat accumulator is manufactured as follows. The heat-accumulating substance containing granules of a selected composition of an Al-Si alloy with a volume content of 30-70% is kneaded together with a ceramic mass based on magnesium oxide, is formed as a cylindrical blank with a central hole and then subjected to a reaction sintering. The elements thus obtained, individually or as a group, are molded into the heat-resistant, highly porous concrete of rectangular shape on the basis of light materials with low intrinsic thermal conductivity of materials selected from the group of mullite, forsterite, chamotte, perlite, vermiculite. The resulting block, together with the inserted electric heaters, the thermal insulation is installed in a metal container with double walls. If necessary, to increase the heat dissipation, channels for the circulation of the coolant (water or air) are organized.

CLAIM

1. A heat storage element containing a substance melting at operating temperatures, characterized in that it is made in the form of a block with ducts of a composite material comprising a substrate of heat-resistant ceramics in which granules are distributed from an hypereutectic aluminum-silicon alloy.

2. Element according to claim 1, characterized in that the composite material is based on magnesium oxide with granules of an aluminum-based alloy with 12.5 25.0 wt. Silicon with a volume content of granules of 30 70 vol.

3. A heat accumulator comprising a housing in which heat storage elements are stored inside which heat is accumulated due to the heat of fusion, electrical heaters, heat insulation, characterized in that the heat storage element or the group of heat storage elements according to claim 1 is fixed on heaters in a metal container with double walls so , That the space between the assembly of heat storage elements and the walls is filled with highly effective thermal insulation, for example, mineral wool and / or highly porous, heat-resistant concrete, and the space between the inner and outer walls is additionally used for organizing natural or forced convection of the coolant.

4. Battery according to claim 3, characterized in that in its upper part is additionally installed a flat radiator, closed from above by a removable heat-insulating lid.

print version
Date of publication 21.03.2007gg