The present invention relates to a heat recovery device of the kind defined in the preamble of claim 1,

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 contai- ^ner 2- For this purpose, the exhaust air is drawn., (arrow PI temperature e.g. 22 C) by means of a fan 3 passed the eva¬ porator 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 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 eva¬ porator 4. _■

Hot water is discharged via a connection 8 located in the up¬ per part of the container 2, whereas cold water is supplied via a lower connection 9. A temperature sensor 10 controls the compressor 5 of the heat pump so that the water tempera- ture in the container 2 is kept at a desired level, e.g. 55 C

It is recognized that, by this method, heat can be pumped from the exhaust air to the hot water only in so far as the hot water is discharged from the container 2 (on the assump- tion that the container is well insulated so that theheat leakage 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 wate 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 con¬ tainer 2 is shown. In the re-circulation circuit, there is also a non-return valve 13 preventing cold water from flow- ing backwards through the radiator 11, when for some reason the pump 12 does not work.

With the embodiment shown in Fig. 3, one obtains an advanta in that the heat pump 1 can work continuously. However, a remaining problem is that the efficiency of the heat pump i unsatisfactory.

Therefore, the object of the invention is to substantially improve the efficiency of the heat pump so as to further re duce 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 diffe-

^* _> rence between the condenser 6 and the vaporizer 4. The func tional relation between the efficiency factor£and the con¬ denser temperature T (for a given temperature of the vapori zer 4) is shown in Fig. 2. As an example, the efficiency fa tor is about 2 in the above-mentioned example, i.e. at a co denser temperature of about 55 C, while the efficiency fac¬ tor can be doubled, i.e. to about 4, in case the condenser can be brought to work at a temperature of about 10°C. Even a moderate temperature reduction could, however, result in substantial improvement, since the relation is essentially linear.

In order to achieve the stated object, the inventive device principally characterized in that the means for recovery of heat from the hot water container consists of a fluid circu lation circuit, which is in heat transferring contact with

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. Compare claim 1.

Hereby, it has turned out to be possible to achieve a forma¬ tion of layers in the hot water container, so that one ob¬ tains a lower zone containing relatively cold water, e.g. of about 30 C, and an upper zone containing relatively hot water, e.g. of about 55 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 or a supply air device) altogether amount to about 60% of the total heat energy consumption.

Suitable additional features of the device and various embodi¬ ments appear from the sub-claims 2-11 and from the detailed description below.

Thus, the invention will be described further below with refe¬ rence to the drawings.

Figs. 1-3 illustrate, as discussed above, the background of the invention;

Fig. 4 shows schematically a first embodiment of the inventive heat recovery device; and

Figs.5-7 show correspondingly a second, a third and a fourth embodiment.

The heat recovery device shown in Fig. 4 is largely like the device discussed above and shown in Fig. 3, and corresponding parts are given the same reference numerals. However, there is an essential difference in that both connections of the water circulation circuit 11, 12 are located

in the lower part of the hot water container 2 adjacent to the heat pump condenser 6. Thus, the feed conduit connection 14 is disposed near, namely somwhat below, the upper edge of the condenser 6, whereas the return conduit connection, which is joined to the supply connection 9 for cold water, is loca¬ ted near,namely somewhat below, the lower edge of the condens 6. Moreover, the system is controlled by two temperature sensors, namely a first temperature sensor 10, which corre¬ sponds to the sensor 10 in the prior art embodiment shown in Fig. 1 and which, thus..,secures that the heat pump will work as long as the water temperature at the sensor is below the desired hot water temperature, e.g. 40-60 C, in particular appr. 55 C, and a second temperature sensor 15, which secures that the pump 12 will work and the water in the circulation circuit with the radiator 11 will circulate as long as the water temperature at this sensor exceeds a predetermined tem¬ perature of e.g. 30-50 C, in particular about 40 C.

Since the connections 14 and 9 are situated in the region of the condense^ 6, the latter can be kept at an advantec _j usly lo temperature level, resulting in an improved efficiency of the heat pump as discussed above. The return conduit connection 9 is also provided with a deflecting plate which secures that the incoming water does not flow upwards, but only sideways. Thus, in the lower part of the container, a zone Zl having a relatively low temperature can be maintained, whereas in the per part of the container there remains a zone 2 with warmer water(having a lower density) . Thanks to such a temperature distribution in the container 2, it is possible to accomplish an improved efficiency of the heat pump, while preserving ^; -.the desired hot water temperature (at the discharge connection 8) .

In fig. 5 there is shown a second emobodiment of the inventiv heat recovery device, and corresponding parts are given the same reference numerals as in Figs. 1,3 and 4. In this case,

there is likewise a water circulation circuit which, via connections 9 and 14, is in heat transferring contact with the water adjacent to the condenser 6 of the heat pump. In¬ stead of a radiator, the circulation circuit contains a sup- ply air unit having a hot water element 16, e.g. a heating element with flanges, and a fan 17 which causes the supply air to the building to pass the element 16 and thereby be prehea¬ ted, at least up to 15-20 C (depending on the temperature of the outdoor air) , before being blown into the interior of the building. In Fig. 5 the supply air flow is schematically indicated by arrows .-P4 and P5. In the upper part of the con¬ tainer 2, i.e. in the upper zone Z2, electrical additional heating elements 18 are arranged. These elements 18 are con¬ trolled by an adjacent third temperature sensor 19, which . turns on the elements 18 as soon as the water temperature in zone Z2 falls somewhat below the desired hot water tempera¬ ture, e.g. at a temperature of 40-90°C, particularly about 65 C. The temperature sensor 10, controlling the compressor of the heat pump l,is in this case located in an interme- diate zone Z3 between the upper and lower zones Z2 ^and Zl. v Like in the previous embodiment, the heat pump operates as long as the water temperature at the sensor 10 does not ex¬ ceed the desired hot water temperature, namely at a tempera¬ ture ef e.g. 40-60 C, in particular about 55°C.

In this case, the sensor 15 can preferably control the fan 17 (instead of the pump 12, which can work continuously) so that the supply air is delivered as long as the sensed water tem¬ perature and thus approximately the temperature of the heating element 16 does not fall below 5-15 C, particularly about 10°C.

Thus, in this embodiment it is possible to let the condenser ^' 6 operate at a lower temperature, whereby the efficiency of the heat pump will increase , as discussed above.

The embodiment according to Fig. 6 operates substantially in the same way as in Fig. 5. The only difference is that a water radiator 11 (compare Fig. 4) is connected in the water circulation circuit between the pump 12 and the heating ele- ment 16. In this case, the excess heat is transferred from the container 2 to the supply air (P4, P5)as well as to ther air (via the radiator 11) .

A further application of the invention is schematically show in Fig. 7, wherein the units 20 and 21 together correspond t the embodiment according to Fig.5. Thus, the water circulati circuit from the feed conduit connection 14 to the return con connection 9 in the lower part of the container' 2 comprises a supply air υmit 21. However, this circulation circuit is also provided with a heat exchanger loop 23 disposed in the lower part of a central heating unit 22.. This unit comprises a central heating vessel 24 and an expansion vessel 25 con¬ nected thereto. Apart from the heat exchanger loop 23, elec¬ trical heating elements 26 are arranged in the vessel 24 for heating the water, if necessary. From an upper feecf conduit ■connection 27 the water circulates in the building (by means of a pump 28) in a loop comprising radiators 29, 29', etc. (each having a thermostatic valve "30,3θ', etc.) and back to a return connection 31. As shown by dashed lines a shunt 32 can, be arranged in conventional manner in the radiator loop. In the illustrated example, there is still another possibili of heating the water in the heating vessel 24, namely by mea of an additional circulation circuit extending from the retu conduit 33 of the radiator loop via a conduit 34 to an ex- changer loop in a non-illustrated heating device, such as a- solar panel, a fireplace, a stove, a wood heater or the like and back to the vessel 24 via a cut-off valve 35, a conduit 36 and a return conduit connection 37. It is understood that the water in the vessel 24 can be heated in three different ways, simultaneously or separately, namely via the heat pump

and the hot water container 2, by means of the electrical elements 26 or by means of the non-illustrated heating de¬ vice and the circulation circuit 33, 34, 35, 36, 37.

Even in the vessel 24 a separation into different hot zones can be achieved, in which the exchanger loop 23 and the cir¬ culation circuit 33-37 serve to preheat the return water from the radiator loop, whereas the electric elements 26 finally heat the water to a desired temperature.

The invention can be modified in serveral different ways within the scope of the following claims. Thus, the re-cir¬ culation circuit from the hot water container may e.g. con¬ tain some other medium than water, in which case an exchan- ger loop is arranged instead of the open connections 9 and 14. The essential point is that the heat exchange is effec¬ ted in the lower part of the container 2 in the region of th condenser 6 of the heat pump, so that the described tempe¬ rature destribution can be maintained in the container 2. ^

Moreover, the heat pump can pick up heat from some other heat source than the exhaust air, e.g. from a water tank, a salt reservoir or the like, which is fed with heat energy at least intermittently via solar panels or in some other way. However, the disposal of the vaporizer of the heat pump in heat transferring contact with the exhaust air from the building, as described above, will probably give the best result, at least in relation to the required investment in technical equipment.