JPS63315862A - Thermoaccumulative type heat exchanger - Google Patents

Abstract

PURPOSE:To provide a peeling of a solid phase layer of PCM generated when a heat is produced under a variation of shape of an object and output heat under a thermal medium of specified temperature by a method wherein a substance accompanied with a variation in phase (PCM) in a region of applied temperature and an object showing a variation in shape near a melting point of the substance are stored in a desired cell of a honeycomb structure. CONSTITUTION:PCM 2 is filled in a zig-zag form in respect to a plurality of cells of a honeycomb rib 1, a shape varying object 3 of which shape is varied with temperature is inserted into PCM 2. The cell filled with these substances is constituted by a thermal accumulation body with lids 4 at both ends, a shell 6 for guiding a thermal medium 3 for storing the thermal accumulation body and a thermal insulation material 7 present between the shell and the thermal accumulation body. With this arrangement, a contact are between the thermal medium 5 and PCM 2 contacting through the honeycomb rib 1 is increased, resulting in that a converted thermal calorie between the time of thermal accumulation and the time of thermal discharging can be increased. Since the shape of a shape varying object 3 is varied with a variation in temperature of PCM 2, a solid phase layer of PCM 2 formed in the rib wall surface is peeled off, a natural convection flow is generated and then a total thermal conductivity is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat engine, and particularly to a regenerative heat exchanger suitable for converting a periodically fluctuating heat source into a steady heat source.

[Conventional technology]

With the depletion of fossil fuels, natural energy sources are being reconsidered, and solar energy is being considered for effective blade use. However, solar energy has the fundamental and unavoidable problem that it is scarce, fluctuates periodically, and is also greatly influenced by the weather.

Therefore, in order to obtain steady output from this solar energy, it is essential to establish heat storage technology. There are two types of heat storage methods for physically storing heat: a sensible heat storage method that stores heat by increasing the temperature of a material, and a material that undergoes a phase change in the operating temperature range (PhaseChange Material).
It is a latent heat type that stores heat in (hereinafter referred to as PCM).

The latent heat type is an extremely attractive heat storage method that stores a larger amount of heat per unit volume than the sensible heat type, and can be extracted at a constant temperature when heat is released.

[Problem that the invention seeks to solve]

However, there was a problem in that the PCM solidified on the wall surface, particularly when heat was released, and the heat exchange characteristics were significantly deteriorated.

For this purpose, the following selection conditions on the PCM side are preferable. In other words, it is a material with high thermal conductivity in the solid phase (reducing thermal resistance), a material with a large volume change during phase change (solidification wall separation occurs, and natural convection heat transfer is maintained). Conditions include the substance having a large coefficient of volumetric expansion in the liquid phase (promoting natural convection), and crystals appearing when the solution solidifies (fin effect).

On the other hand, the conditions for the heat transfer container for filling PCM are as follows:
Examples include a large heat transfer area, a shape that promotes natural convection, and a material with high thermal conductivity.

However, within the conditions required for PGM and heat transfer containers,
These are not necessarily prioritized; for example, if a PCM or heat transfer vessel is selected that satisfies the conditions such as heat storage amount, heat storage temperature, heat exchanger volume, etc., the above conditions are satisfied. PCM was not always present, and there were cases where the heat exchange characteristics during heat output had to be sacrificed.

On the other hand, if the heat exchange characteristics at the time of heat output are satisfied, specifications such as the amount of heat storage, the heat storage temperature, and the volume of the heat exchanger may not be met.

That is, in the conventional technology, no fundamental measures have been taken against the deterioration of heat exchange characteristics due to wall surface solidification of the PCM during heat release, and these measures have only been secondary measures.

The purpose of the present invention was to solve the above-mentioned problems, and to provide a regenerative heat exchanger that prevents wall surface solidification during heat output from any PCM and does not reduce heat exchange characteristics. There is a particular thing.

[Means for solving problems]

In order to achieve the above object, the regenerative heat exchanger of the present invention includes, in a predetermined cell of a plurality of cells of a honeycomb structure,
A heat storage body filled with PCM and into which an object that changes shape near the melting point of the PCM is inserted, and a lid is placed only on the predetermined cell in which the PCM and the shape-changeable object reside, and the heat storage body is housed. It consists of a shell through which a heat medium is guided.

[Effect]

According to the above configuration, in the predetermined cells of the honeycomb structure,
Since the PCM and an object whose shape changes near the melting point of the PCM are subjected to internal pressure, the shape of the object changes as the temperature of the PCM changes during heat storage or heat release.

Therefore, especially when heat is released, the in-phase layer of PCM that is being formed on the rib wall surface of the honeycomb peels off from the rib wall surface due to the shape change of the object. As a result, liquid phase PCM flows to fill the space formed between the rib wall surface and the separated solid phase layer of PCM, and natural convection is restored or continues between the rib wall surface and the liquid phase PCM. The overall heat transfer coefficient increases, and heat exchange during heat output is promoted. Furthermore, the shape-changing object will develop a fin effect in the PCM, promoting heat transfer.

〔Example〕

Embodiment 1 A first embodiment of the present invention will be described below based on the drawings.

FIGS. 1 and 2 show an embodiment of the regenerative heat exchanger according to the present invention, with FIG. 1 being a fragmented vertical cross-sectional view and FIG. 2 being a cross-sectional view.

PCM in staggered position for multiple cells of honeycomb rib 1
A shape-changing object 3 whose shape changes depending on the temperature is inserted into the PCM 2, and only the cell filled with these materials has a heat storage body with lids 4 on both ends, and a heat storage body that houses this and a heat medium. 5 and a heat insulating material 7 interposed between the heat storage body.

In this example, the honeycomb rib 1 has a cordierite composition, a cell size of 10 nm square, a rib thickness of 1 mm, and an outer diameter of 155 nm.
n square, number of cells 14x14. A material with a thickness of 500 mm was used. C22H4G (melting point 44°C, latent heat 60 kca Q/kg) is filled as PCM2, and Cu
-Z n -A Q-based shape memory alloy (10~50℃
A material formed into a spring shape at 10° C. or lower is inserted into the filling material (deformed at 10° C.), and both ends of the filling material are covered with lids 4 using an inorganic adhesive.

Next, the operation of this embodiment will be explained.

Since the cells containing the PCM 2 and the shape-changing object 3 are arranged in a staggered manner as shown in FIG. 2 among the plurality of cells of the honeycomb structure, the contact area between the heat medium 5 and the PCM 2 that come in contact with each other through the honeycomb ribs 1 becomes large, and as a result, the amount of converted heat during heat storage and heat output can be increased.

In addition, as the shape of the shape-changing object 3 changes as the temperature of the PCM 2 changes, the solid phase layer of the PCM 2 formed on the rib wall peels off, natural convection occurs, and the overall heat transfer coefficient increases. heat exchange is promoted.

In this embodiment, air at a temperature of 50 to 80°C is used as the heating medium 5 at 0°C per minute.
．． Figure 3 shows the heat storage characteristics when 5 to 1 rri' is distributed.
Figure 4 shows the heat output characteristics. As is clear from these characteristics, it can be seen that the outlet temperature of the heating medium 5 is kept almost constant during heat output.

In addition, as Example 2, when using the same cell dimensions as Example 1, except for the same external shape, thickness PCM, and shape memory alloy, as shown in FIGS. 3 and 4, Compared to Example 1, the characteristic is that the heating medium temperature during heat output tends to gradually decrease.

When these Examples 1 and 2 are compared with a comparative example in which no shape memory alloy is inserted in Example 1, as shown in FIGS. 3 and 4, the comparative example is different from the example. It can be seen that the temperature at the time of heat release decreases almost continuously compared to Example 1 and Example 2.

In this way, according to these embodiments, the solid phase layer of PCM generated on the heat transfer surface during heat output is peeled off at any time, and natural convection is continuously generated near the heat transfer surface. It has the effect of being extracted using a heating medium at a certain temperature.

As still another example 3, as shown in FIGS. 5 and 6, a shape-changing object 3 is provided in a honeycomb cell with a spring 31 having a high thermal conductivity (made of steel) and whose shape changes at 10 to 50 degrees Celsius. A spring having a structure in which springs 32 made of shape memory alloy (Cu-Zn-AQ series) are connected in series is inserted, and both ends are embedded and fixed in the lid 4 made of inorganic adhesive.

The springs 31 and 32 are arranged to be substantially inscribed within the honeycomb rib 1, and the spring 31 is always in a tensioned state, and the spring 32 is installed in a contracted state at a temperature higher than the melting point of the PCM2.

According to the third embodiment, when the shape memory alloy has a melting point of PCM or lower, the spring 31 contracts and the spring 32 expands. On the contrary, PC
If the temperature is higher than the melting point M, the spring 31 will expand and the spring 32 will contract.

At this time, there are contact points between the springs 31 and 32 and the cell wall surface on the wall surface which is the starting point for the formation of the solid phase layer 2a of the PCM 2.

Therefore, even if the shape memory alloy spring 32 locally reaches the temperature where the memory temperature is expressed, the spring expands and contracts, resulting in the peeling effect of the solid phase layer 2a.

As a result, at temperatures where PCM2 undergoes a phase change, the spring 31
．． 32 moves along the heat transfer wall (honeycomb ribs 1), which has the effect of peeling off the solid phase layer 2a especially when heat is released, thereby improving heat transfer efficiency. Further, since the springs 31 and 32 exhibit a fin effect, a synergistic effect of improving heat transfer efficiency occurs.

In addition, 2b in FIG. 6 is PCM2 in a liquid phase.

〔Effect of the invention〕

As described above, according to the present invention, PCM and an object whose shape changes near the melting point of the PCM are present in the predetermined cells of the honeycomb structure, so that the solid phase layer of PCM generated when heat is released is It peels off at any time due to changes in shape, and heat is emitted by a heating medium at a constant temperature.

Therefore, a regenerative heat exchanger with no deterioration in heat exchange characteristics can be obtained.

Furthermore, if the regenerative heat exchanger according to the present invention is used.

It can collect and store solar heat or exhaust heat from boilers, etc. in a high density, and can be used as a heat storage medium in a Ljungström air preheater, for example. Also, when heat is output, it is output as a heat medium with little temperature fluctuation, so the temperature can be reduced. It is possible to create a heat exchange system that does not require a control device.

[Brief explanation of the drawing]

Fig. 1 is a fractured longitudinal cross-sectional view of Example 1 or 2, Fig. 2 is a nn cross-sectional view of Fig. 1, Fig. 3 is a heat storage characteristic graph, Fig. 4 is a heat output characteristic graph, and Fig. 5 is a detailed diagram inside the cell of Example 3,
FIG. 6 is a cross-sectional view of Example 3. 1...Honeycomb ribs. 2...PCM, 3...Shape changing object, 4...Lid, 5...Heating medium, 6...Shell, 7...Insulating material.

Claims (3)

[Claims] (1) An object filled with a substance that undergoes a phase change in the operating temperature range and whose shape changes near the melting point of the substance is inserted into a predetermined cell among the plurality of cells of the honeycomb structure, and the substance and the shape A regenerative heat exchanger comprising a heat storage body in which only the predetermined cell in which a changeable object resides is covered, and a shell that houses the heat storage body and allows a heat medium to flow therethrough. (2) The regenerative heat exchanger according to claim 1, wherein the predetermined cells are arranged in a staggered manner with respect to the plurality of cells of the honeycomb structure. (3) The shape-changing object is composed of a highly thermally conductive steel spring and a shape-memory alloy spring whose shape changes depending on temperature, which are connected in series, and both ends are fixed to the lid. A regenerative heat exchanger according to claim 1 or 2, characterized in that: