DE2841804A1 - Heat pump for central heating - has refrigerator circuit with evaporator in air duct, with exhaust fan and heater - Google Patents

Abstract

The heat pump for a heating system has an engine (5) driving a compressor (6) in a circuit with a condenser (7) which has a coil in circuit with the engine heat exchanger coil(10). The refrigeration fluid passes through an evaporator coil (9) in a duct (13) thrrough which external air is drawn by an extraction fan (12). This air is preheated by a heater (14) preceding he evaporator (9) and forming a unit with it, and which operates so as to increase the compressor output by permitting higher speeds. This heater, or alternatively an electric element. The duct includes a control flap (16).

Description

SACHS SYSTEMTECHNIK GMBH - 8720 SCHWEINFURT

J

PATENT AND UTILITY MODEL APPLICATION

Heat pump with additional heating. ung

The invention relates to a heat pump with additional heating, which is kept in circulation by a compressor and which transports heat having serving refrigerant, the heat absorbed by an evaporator from the outside air via a condenser is delivered to a heating circuit.

It is known to have heat pump systems with conventional heating in the form of a fired boiler or a water heater to combine, as the heating system after the coldest Anniversary must be designed. When the ambient temperature falls, the heat output of a heat pump is the opposite of the increase Heat requirement of the rooms to be heated. The additional heating by the boiler takes place either in bivalent-parallel mode when outside temperatures are low Operation, i.e. the useful heat generation takes place by heat pump and boiler, or the heating is operated in bivalent alternative mode, d. i.e. at low outside temperatures the useful heat is only generated by the boiler; the boiler usually provides the heating flow brought to the required temperature.

These heat pump heating systems are different as a result of the two Heat generator and the associated complex heat exchanger with a high construction cost and a large one Space is required so that the investment for such systems is substantial.

In climate zone 2, designated according to DIN 4701, outside temperatures below -5 ⁰ C occur annually only for a period of approx. Ten heating days. Accordingly, the frequency of use of the additional heating is low, so that its operating costs, measured against the total heating period, are of secondary importance.

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28418Q4

The object of the present invention is to provide a heat pump heating system that is simple compared to the previously known heat pump extraction systems to create, whereby existing system components should be used as far as possible. In addition, the heat pump heating system should be easy to assemble and inexpensive to purchase and take up as little space as possible.

According to the invention this object is achieved in that the additional heater is arranged in the area of the evaporator and the evaporator is heated by this. This will do this in an easy way the peak heat demand on the few very cold days covered by this heat pump heating system, with the construction of the heating system it is easy to use existing system components and thus also the investment costs for such a system are low. In addition, a small installation space is required, so that extensive freedom of movement is guaranteed when installing the system is.

A further increase in the heating power of the heat pump is obtained according to the invention in that, in addition to the auxiliary heating At temperatures below the design point of the heat pump, the compressor output is increased by increasing the compressor speed will. Such an increase in the compressor speed is possible in particular in the case of a heat pump operated by an internal combustion engine is driven, with the internal combustion engine only demanding peak performance on the very few cold days in the rest of the heating season, the internal combustion engine is operated in the partial load range.

A very simple and inexpensive solution in structure is obtained according to a feature in that the auxiliary heating and the Evaporator form a structural unit. An alternative solution results according to the invention by the outside air in one Channel is out and sucked in by a fan and the additional heater is arranged in the air flow in front of the evaporator, the Additional heating heats the evaporator via the air flow.

The additional heating can either be a gas or an oil burner or be formed by electric heating rods. According to the invention, the channel has a short circuit channel

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on, wherein a deflection device for the air flow is arranged, which switches to a circulating air flow as a function of the temperature. In the case of evaporator heating, this switchover is expediently carried out when the exhaust air temperature is downstream of the evaporator corresponds to the outside air temperature, since no more heat can then be extracted from the surroundings. This deflector is designed according to the invention as a flap and thus easy to expand.

Another major simplification of the heat pump heating system is obtained according to the invention in that the additional heater is designed as a defrosting device for the evaporator is.

If the evaporator freezes up, it is therefore easily possible to defrost it by using the auxiliary heating.

The invention is more detailed below with reference to drawings explained. It shows:

Fig. 1 shows the course of heating power of the heat pump and heat demand of the rooms above the ambient temperature;

2 shows the annual duration curve of the outside temperature;

3 shows the heat pump with additional heating in a schematic representation and

4 shows the heat balance of the heating system shown as an example.

In Fig. 1, the heat demand curve 1 is plotted against the ambient temperature. It is assumed that the average room temperature should be 20 C, so that at an ambient temperature of 20 C, the heat demand curve 1 intersects this abscissa, ie the heating output is 0 % at this point. According to the design according to DIN ^ 701, climate zone 2 is the coldest

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The anniversary is assumed to be -15 C, so that the heat demand curve 1 at -15 ° C results in a heating output of 100%. The heating output of the heat pump at constant output is shown by curve 2. The heat demand curve 1 and the heating output curve 2 intersect in point 3- Accordingly, the heat demand can only be covered by the heat pump up to a temperature of -5 C, although this heat demand only corresponds to 70% of the heating output for which the heating in the climate zone is 2 must be interpreted. The design described above is based on the heat pump with additional heating.

The annual duration curve h shown in FIG. 2 shows that 195 days of the year have outside temperatures between +3 and +18 C. Fig. 2 also shows that during a year 35 days have temperatures which are below +3 C and a total of only 10 days colder than -5 ° C. A heat pump designed for maximum heating output has comparatively high investment costs and, because of the specific heating output curve of heat pumps, would have to be operated in the low partial load range during most heating days, ie in uneconomical intermittent operation. Due to these relationships, it does not make sense to design a heat pump heating system for the coldest anniversary. However, this then results in the need for an additional heat generator to cover the peak heat demand on the few particularly cold days.

The heat pump with additional heating is shown schematically in FIG. 3. The compressor 6, which is the refrigerant used for heat transport, is driven by the internal combustion engine 5 compressed and conveyed to the condenser 7 via the pipeline. The refrigerant reaches the evaporator 9 via the expansion valve 8, in which it absorbs heat from the outside air. In the condenser 7, this heat is given off to the heating circuit via a heat exchanger, with the waste heat from the internal combustion engine 5 being transferred the heat exchanger 10 is also fed to the heating circuit

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will. This heating circuit is maintained by the circulation pump 11. The fan 12, the evaporator 9 and the additional heater 14 are arranged in a channel 13. This channel 13 has a short-circuit channel 15, which can be connected through the valve 16 with the channel 13 such that the air flow only through the passage 13 and the short-circuit passage is circulated 15th The additional heater 14 can be combined with the evaporator 9 to form one component, or - as shown in the figure, be arranged separately in the air flow. The flap 16 normally closes the short-circuit channel 15 so that the air sucked in by the fan 12 is conveyed through the fins of the evaporator 9 and cooled, whereby the refrigerant evaporates.

The design point of the heat pump is - as shown in Fig. 1 at -5 C. If the outside temperature now falls below this design point, the heat demand is met by increasing the refrigerant throughput by increasing the speed of the internal combustion engine 5, with the auxiliary heater 14 providing heat to the evaporator 9 feeds. For this purpose, the additional heater 14 can be integrated in the evaporator or the additional heater 14 emits the heat to the air that is sucked in by the fan 12 through the evaporator 9. When the temperature of the air sucked through the evaporator 9 reaches the outside temperature, no more heat can be absorbed from the surroundings and the flap 16 closes the duct 13, as shown in the drawing. The air now flows from the channel 13 into the short-circuit channel 15 and forms a circulating air flow which is heated by the additional heater l4 ₃ , cools at the evaporator 9 and is again passed through the short-circuit channel 15 to the additional heater. If the evaporator 9 reaches temperatures below the freezing point of the water, it will ice up more and more as a result of the condensate from the air flowing through it, whereby the auxiliary heater 14 can then be used to defrost the evaporator.

In Fig. 4, the heat demand curve 17 is above the ambient temperature plotted, the design point of the heat pump through

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the intersection of the heating power curve 18 of the heat pump with the heat demand curve 17 is formed. The heating output curves of the heat pump 18, 20 and 21 are curves of constant output, with curve 18, for example, a compressor speed of 3,000 l / min, curve 20 a compressor speed of 3 * 800 l / min and curve 21 a compressor speed of 4,600 l / min. The intersection of curves 17 and 18, ie the design point of the heat pump corresponds to the heat demand at -5 ⁰ C outside temperature, the heat pump supplying 70% of the maximum heat demand at -15 C -. TJm to ensure a long service life of the internal combustion engine driving the compressor, this is driven in normal operation in the partial load range according to curve 18.

If the outside temperature falls below the design temperature (-5 C), then the heating power without additional heating on the evaporator will run in accordance with the curve 19 drawn in dashed lines. Because of the strong increase in the specific volume of the refrigerant vapor at low evaporation temperatures, the speed should of the internal combustion engine-compressor unit up to 5,000 l / min can be increased. With additional heating of the evaporator, at a constant speed of 3,000 l / min at temperatures below -5 C the heating power curve 18 is reached.

When the evaporator is heated and the drive power is increased by increasing the speed to 3 · 800 l / min, an intersection point is obtained between the heat demand curve 17 and the heat output curve 20 at an ambient temperature of -11.5 ° C. The heat output of the heat pump heating system then increases to approx. 90 % of the maximum heat demand. A further increase in the drive power by increasing the speed to * 1,600 l / min leads to an intersection of the heat demand curve 17 with the heating power curve 21 at maximum heat demand corresponding to the outside temperature of -15 ° C

08/31/78
TIP-I Be

0300U / 0A43

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Claims (9)

PATENT CLAIMS Heat pump with additional heating, which is kept in circulation by a compressor and used to transport heat having, the heat absorbed by an evaporator from the outside air via a condenser to a heating circuit is given, dad. gek. That the additional heater (14) is arranged in the area of the evaporator (9) and the evaporator (9) is heated by this. 2. Heat pump according to claim 1, dad. gek. that apart from the additional heating (14) at temperatures below the design point of the heat pump, the compressor output due to higher compressor speed is raised. 3. Heat pump according to claims 1 and 2, dad. gek. that the auxiliary heating (14) and the evaporator (9) form a structural unit. 4. Heat pump according to claims 1 and 2, dad. gek. that the outside air is guided in a channel (13) and sucked in by a fan (12) and the auxiliary heater (14) in the air flow in front of the Evaporator (9) is arranged. 5. Heat pump according to claims 1 to 4, dad. gek. that the additional heater (.14) has a gas or an oil burner. 6. Heat pump according to claims 1 to 4, dad. gek. that the auxiliary heating (14) is formed by electric heating rods. 7. Heat pump according to claims 1 to 6, dad, k. That the channel (13) has a short-circuit channel (15), a deflection device for the air flow being arranged which is temperature-dependent switches to a circulating air flow. 8. Heat pump according to claims 1 to 7, dad. gek. that the deflection device is a flap (16). 9. Heat pump according to claims 1 to 8, dad. gek. that the auxiliary heating (14) is designed as a defrosting device for the evaporator (9). 3I.O8.1978 - TIPP-I Be / whm- 030ÖU / 0U3 ORIGINAL INSPECTED