JPS6039710Y2 - hot water tank - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a hot water storage tank that employs a structure in which a plurality of heat exchangers with different temperatures are arranged in the tank to simultaneously heat water for hot water supply.

When multiple heat exchangers are installed in a hot water storage tank, and heat sources with different temperature levels, such as waste heat, are circulated and heated or stored simultaneously, the water in the tank causes natural convection, and the overall temperature gradually increases. is rising.

For this reason, they have disadvantages in terms of use, such as requiring a certain amount of waiting time to obtain high-temperature water and not being able to store heat by effectively using the capacity of the hot water storage tank.

For example, to explain the drawbacks of the conventional method of utilizing waste heat in an engine-driven heat pump system, in Fig. 1, 18 is a hot water storage tank, 11 is an engine, 12 is a compressor, 13 is a waste heat circuit, and 14 is a waste heat pump system. 15 is a heat exchanger (heat exchanger for high temperature heat source), 15 is a condenser of the heat pump circuit (heat exchanger for low temperature heat source), 16 is an expansion valve, and 17 is an evaporator.

In such a waste heat utilization system, the temperature level Th on the waste heat circuit 13 side is high ((for example, 80°C)
The temperature level on the side is low (eg 45°C).

Therefore, there are two types of heat sources with different temperature levels in the hot water storage tank 18.
The problem is how to store heat at different temperature levels.

In the case of FIG. 1, heat from the high-temperature heat source and heat from the low-temperature heat source are generated at the same time. The engine-driven heat pump stops hot water storage operation when the temperature around the heat exchanger 15 reaches the temperature TI of the low-temperature heat source, whichever comes first.

Therefore, the amount of heat stored in the hot water tank 18 at that time is
If the capacity of the hot water storage tank 18 is constant, it will strongly depend on the temperature distribution within the hot water storage tank 18 and the arrangement of the high temperature and low temperature heat exchangers.

Assume that operation for hot water storage is started in a state where all water temperatures in the hot water storage tank are equal to the water supply temperature.

The temperature distribution inside the hot water storage tank when the hot water storage operation is stopped is as shown in Figure 2.
, In the 13th part, there is hot water with a temperature T1 equal to that of the low-temperature heat source.
It is assumed that each heat exchanger is installed in a hot water storage tank so that hot water can be stored.

Now, assume that there is a demand for hot water supply from the outside for hot water xl, and high temperature hot water X1 is used (x<aX x<b).

Warm rin water is supplied from the lower part of the hot water tank 18,
The temperature distribution within 8 is as shown in Figure 3, and during hot water supply operation, water Xl at the supply water temperature Tin is heated by the low temperature heat source.
Water X1 at temperature T1 will be heated by the high temperature heat source.

If the specific heat of water is C, the amount of heat required for water a1 at temperature TI to reach ℃ is (Th-TI)X-c, temperature T
The amount of heat required for the water X1 in the water to reach the temperature above is (T
I −Tin) ・x”c.

Taking the ratio of this heat amount, (Th-T1)・X-c: (T'1-Tin)・X-c
= (Th −TI) : (TI−Tin) −
−−・−■.

However, in a gas engine heat pump, the ratio of the amount of heat generated from the high-temperature heat source and the low-temperature heat source is determined, for example, as shown in FIG. 4, and generally does not match the ratio shown in equation (2).

This shows that water heated by a high-temperature heat source or a low-temperature heat source generally cannot reach the maximum temperature that both can reach, and the capacity of the hot water storage tank cannot be used effectively. It shows that there is no.

The cause of this situation is that the arrangement of the high temperature heat exchanger 14 and the low temperature heat exchanger 15 in the hot water tank 18 is
There is a level difference, and the water at the top of each heat exchanger is heated by the hot water in that heat exchanger, gradually raising the overall temperature by natural convection, and finally reaches the same temperature as the heat source. This is because water heated to the same temperature as the heat source is not stored in layers from above.

When heating with this heat exchanger, the present invention does not gradually raise the temperature of the water present in the upper part of the heat exchanger as a whole, but heats the water partially and brings the water closer to the heat source temperature. The unique feature is that hot water is stored in layers from the top of the tank.

Hereinafter, the present invention will be described in detail based on FIGS. 5 and 6. In FIG. The upper opening 2 is located above the tank, the lower opening 3 is located below the tank, and there is a thermovalve (automatic flow control valve) inside the heat insulating cylinder 1 that closes when the temperature is below a set temperature and opens when the temperature exceeds the set temperature. This is the configuration with 4 installed.

Note that the thermovalve 4 may be one that utilizes thermal expansion of gas or liquid, or one that is electrically activated by detecting water temperature.

FIG. 6 shows an embodiment in which a low-temperature heat exchanger 15 is installed below the high-temperature heat exchanger 14 configured as described above in the hot water storage tank 18.

If the inside of the hot water storage tank 18 is configured as described above and the set temperature of the thermovalve 4 is set near the temperature of the heat source, the water surrounded by the heat insulating tube 1 and the thermovalve 4 will flow near the thermovalve 4. It is not allowed to move inside the hot water storage tank 18 while the temperature of the hot water is lower than the set temperature, and the valve 4 opens only when the temperature near the thermovalve 4 reaches the set temperature, and the high temperature water in the heat insulating cylinder 1 opens. The hot water comes out from the upper opening 2 of the hot water storage tank 18 and is stored in the upper part of the tank.

When high-temperature water flows out from inside the heat insulating cylinder 1 and the temperature near the thermovalve 4 decreases, the thermovalve 4 closes and repeats the same operation.

Comparing this with the case where the heat insulating cylinder 1 and thermovalve 4 are not present, in the latter case, when the water existing around the heat exchanger is heated by the heat source, even if the temperature has risen slightly, the water surrounding the heat exchanger will Due to the difference in specific gravity between the heat exchanger and the heat exchanger, the water moves to the upper part of the hot water storage tank, and new low-temperature water flows into the area around the heat exchanger, repeating the same process.

In this way, natural convection occurs freely within the hot water tank, so
The temperature inside the hot water storage tank gradually rises as a whole, and it is not possible to create a layer of high-temperature water near the heat source from the top, as in the present invention.

Next, if a heat exchanger having the above-mentioned heat insulating tube 1 and thermovalve 4 is installed as a heat exchanger for a high-temperature heat source at a sufficiently low position in the hot water storage tank 18 as shown in FIG. The generated hot water has a temperature close to the high-temperature heat source and is stored from the upper part of the hot water storage tank 18, and is not dispersed over the entire water above the high-temperature heat source.

Therefore, the hot water storage operation is stopped by the low temperature heat exchanger 15.
When the ambient temperature reaches the temperature of the low-temperature heat source, the hot water storage tank 18 automatically has the maximum amount of heat that can be stored.

As described above, according to the present invention, heat generated at different temperature levels at the same time is formed into layers close to each temperature level in one hot water tank 18, and the boundary between the two layers is automatically formed at an optimal position. It has the effect of storing heat.

Further, according to the present invention, the temperature of the stored hot water can be set by the set temperature of the thermovalve 4, and the temperature of the heat insulating cylinder 1 can be set.
By selecting a material that has as little heat conduction as possible between the inside and outside, the above-mentioned functions and effects of the present invention can be further promoted.

Next, according to the present invention, hot water is stored by gradually expanding (descending) the high-temperature layer from the top of the tank downward by the action of the heat insulating cylinder 1 and thermovalve 4, thereby shortening the waiting time for hot water supply at the time of startup. It is possible to increase hot water supply and heat storage capacity.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional hot water storage tank, FIGS. 2 to 4 are explanatory diagrams of a conventional hot water storage tank, and FIGS. 5 and 6 are explanatory diagrams of a hot water storage tank according to the present invention. 1...Insulating cylinder, 2...Top opening, 3
...Lower opening, 4...Thermo valve, 14...High temperature heat exchanger, 15...
Low temperature heat exchanger, 18...Hot water storage tank.

Claims (1)

[Scope of utility model registration request] In a hot water storage tank with a low-temperature heat exchanger installed in the lower part of the tank and a high-temperature heat exchanger installed in the upper part, the high-temperature heat exchanger is covered with an insulating cylinder that is long in the vertical direction of the tank, and is also insulated. A hot water storage tank with the top and bottom of the cylinder open and an automatic flow control valve attached to the top of the insulated cylinder.