Refrigeration – Disparate apparatus utilized as heat source or absorber – With vapor compression system
Patent
1981-11-18
1983-11-22
King, Lloyd L.
Refrigeration
Disparate apparatus utilized as heat source or absorber
With vapor compression system
237 2B, F25B 2702
Patent
active
044161212
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a heat recovery device.
FIG. 1 illustrates such a previously known device comprising a heat pump 1 and a container 2 for consumption hot water. The heat pump transfers heat from a heat source, namely from the exhaust air from a building, to the water in the container 2. For this purpose, the exhaust air is drawn (arrow P1), at a temperature of, e.g., 22.degree. C. by means of a fan 3 past the evaporator 4 of the heat pump (arrow P2), so that the outflowing air (arrow P3) leaves the device at a substantially lower temperature, e.g., 5.degree. C. By means of a compressor 5, the heat carrying medium is pumped to a condenser 6 located in the lower part of the hot water container 2, from which heat is transferred to the ambient water. From the condenser 6, the heat carrying medium is returned via a throttle 7 to the evaporator 4.
Hot water is discharged via a connection 8 located in the upper part of the container 2, whereas cold water is supplied via a lower connection 9. A temperature sensor 10 controls the compressor 55 of the heat pump so that the water temperature in the container 2 is kept at a desired level, e.g., 55.degree. C.
It is recognized that, by this method, heat can be pumped from the exhaust air to the hot water only to the extent that the hot water is discharged from the container 2 (on the assumption that the container is well insulated so that heat loss to the environment is negligible). An obvious method to solve this problem and enable continuous recovery of heat from the exhaust air to the building would be to let hot water circulate from the discharge connection 8 of the container 2 via a water radiator 11 to the supply connection 9 by means of a circulation pump 12, as shown in FIG. 3. In this figure, for the sake of simplicity, the various parts of the heat pump 1 are left out. However, the condenser 6 in the container 2 is shown. In the re-circulation circuit, there is also a non-return valve 13 preventing cold water from flowing backwards through the radiator 11, when for some reason the pump 12 does not work.
With the embodiment shown in FIG. 3, one obtains the advantage that the heat pump 1 can work continuously. However, a remaining problem is that the efficiency of the heat pump is unsatisfactory.
Therefore, the object of the invention is to substantially improve the efficiency of the heat pump so as to further reduce the total energy consumption in the building, in which the device is installed.
The invention is based on the knowledge that the efficiency of the heat pump strongly depends on the temperature difference between the condenser 6 and the vaporizer 4. The functional temperature T (for a given temperature of the vaporizer 4) is shown in FIG. 2. As an example, the efficiency factor is about 2 in the above-mentioned example, i.e., at a condenser temperature of about 55.degree. C., while the efficiency factor can be doubled, i.e., to about 4, if the condenser 6 can be brought to work at a temperature of about 10.degree. C. Even a moderate temperature reduction could, however, result in a substantial improvement, since the relation is essentially linear.
In order to achieve the stated object, the inventive device has a means for recovery of heat from the hot water container consisting of a fluid circulation circuit, which is in heat transferring contact with the water in the lower part of the hot water container, in which lower part the condenser of the heat pump and the cold water supply connection are located.
This arrangement has made it possible to achieve a formation of layers in the hot water container, a lower zone containing relatively cold water, e.g., of about 30.degree. C., and an upper zone containing relatively hot water, e.g., of about 55.degree. C. Hereby, the efficiency factor of the heat pump can be maintained above 3, which in a typical single-family house corresponds to an energy saving of about 40%, provided that the hot water consumption and the heat delivered by the fluid circulation circuit (via, e.g., a water radiator
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Carlsson Gunnar
Lindholm Hans
Sjostedt Bertil
Elektro Standard AB
King Lloyd L.
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