Field of the invention

The invention relates to a heat pump installation for heating a medium according to the preamble of claim 1. The invention also relates to a method for heating a medium according to the preamble of claim 6.

Background of the invention

Known is a heat pump installation for heating a medium comprising a refrigerant circuit comprising a compressor and an expansion member and a refrigerant circulating therein which extracts heat from a source by means of a first heat exchanger at a lower temperature and relinquishes heat to the medium by means of a second heat exchanger at a higher temperature. In a ‘condensing’ heat pump cycle the refrigerant leaves the compressor in its gas phase, after which it relinquishes heat to the medium in the second heat exchanger (condenser), and in doing so condenses. The pressure of the refrigerant is then reduced in the expansion member, after which it extracts heat from the source in the first heat exchanger (evaporator) and evaporates again. Ina ‘transcritical’ heat pump cycle the refrigerant leaves the compressor in its supercritical phase, after which it relinquishes heat to the medium to be heated in the second heat exchanger (gas cooler) and in doing so remains in its supercritical phase. The pressure of the refrigerant is then reduced in the expansion member and in doing so it condenses (partially or wholly), after which it extracts heat from the source in the first heat exchanger (evaporator) in its subcritical phase and evaporates (wholly ) again. Flow rate, supply temperature, specific heat capacity and desired discharge temperature of the medium determine the necessary properties of the refrigerant leaving the compressor: flow rate, specific condensation heat or heat capacity, temperature and pressure. The temperature of the supplied medium to be heated determines here the maximum amount of heat which can be extracted from the refrigerant circulating in the refrigerant circuit. A heat pump installation can also comprise two refrigerant circuits, wherein a second refrigerant circulating in a second refrigerant circuit extracts additional heat from a first refrigerant circulating in a first refrigerant circuit by means of a third heat exchanger, which additional heat is upgraded to a higher temperature by means of the second refrigerant circuit and is then relinquished to the medium by means of a fourth heat exchanger. Additional heat can thus be extracted from the first refrigerant by means of the third heat exchanger, wherein the first refrigerant can be cooled in the third heat exchanger to a temperature below the temperature of the supplied medium to be heated. The additional heat extracted from the first refrigerant by means of the third heat exchanger can here be taken from the source, while no additional mechanical energy, for driving the first compressor, is necessary for this purpose. This can concern two transcritica! heat pump cycles, wherein heat is relinquished to the medium by means of the second heat exchanger and the fourth heat exchanger in parallel, see EP2631562A1, or two condensing heat pump cycles wherein heat is relinquished to the medium by means of the second heat exchanger and the fourth heat exchanger in series, see JPH04263758A, or a condensing first heat pump cycle and a condensing or transcritical second heat pump cycle wherein heat is relinquished to the medium by means of the second heat exchanger and the fourth heat exchanger in series, see CN110260550A. The present invention now provides an improved heat pump installation comprising two refrigerant circuits of said type and also an improved method for heating medium by means of such a heat pump installation.

Summary of the invention

The invention provides a heat pump installation according to claim 1 and a method according to claim 6. Heat can thus be optimally extracted from the first refrigerant by means of the second heat exchanger, fifth heat exchanger and third heat exchanger, wherein the first refrigerant can be cooled again to a temperature below the temperature of the supplied medium to be healed. Hie additional heat extracted from the first refrigerant by means of the fifth heat exchanger can here once again be taken from the source, while once again no additional mechanical energy, for driving the first compressor, is necessary for this purpose. Brief description of the drawings

The invention is further elucidated hereinbelow on the basis of non-limitative exemplary embodiments. Schematically in the drawings: figure 1 shows a first exemplary embodiment of a heat pump installation according to the invention, and figure 2 shows a more elaborate detail thereof; and figure 3 shows a second exemplary embodiment of a heat pump installation according to the invention.

Further elucidation and exemplary embodiments

The heat pump installation (1) according to the invention shown in figure 1 comprises means for supplying medium to be heated ( 10), having medium flow (11-19) through the heat pump installation (1) and discharging heated medium (30), a first refrigerant circuit (100) with a first refrigerant (50) circulating therein and comprising a first compressor (101) and a first expansion member (102), a first heat exchanger (103) for extracting heat from a source and relinquishing heat to the first refrigerant (50), a second refrigerant circuit (200), see figure 2, with a second refrigerant (51) circulating therein and comprising a second compressor (201) and a second expansion member (202), a second heat exchanger (40) for extracting heat from the first refrigerant (50) and for relinquishing heat to at least a part (13) of medium flowing through the heat pump installation (1), a third heat exchanger (42), in series with and downstream of the second heat exchanger (40) in respect of the first refrigerant (50), for extracting heat from the first refrigerant (50) and for relinquishing heat to the second refrigerant (51), and a fourth heat exchanger (43) for extracting heat from the second refrigerant (51) and for relinquishing heat to at least a part (15) of medium flowing through the heat pump installation (1). The third heat exchanger (42) here transfers heat from the first refrigerant (50) to the second refrigerant (51) via a first intermediate medium (52), and from the second refrigerant (51 ) to the medium (15) via a second intermediate medium (53), as shown in figure 2, although this can also be done directly without intermediate media. According to the invention, the heat pump installation (1) now also comprises a fifth heat exchanger (41), in series with and downstream of the second heat exchanger (40) in respect of the first refrigerant (50) and in series with and upstream of the third heat exchanger (42) in respect of the first refrigerant (50), for extracting heat from the first refrigerant (50) and for relinquishing heat to at least a part (11) of the medium flowing through the heat pump installation (1). Here, it concerns a condensing heat pump cycle in both refrigerant circuits (100,200). The supplied medium (10) to be heated is here heated (11-12) at least partially (11) by means of the fifth heat exchanger (41) and, for the remaining part (13), heated (13- 14) in parallel by means of the second heat exchanger (40). The part-flows (12,14) heated in parallel are then combined (12+14=18) and then heated further (15-16) at least partially (15) by means of the fourth heat exchanger (43). The remaining part (19) is combined (19+16) with the further heated part-flow (16) and leaves (30) foe installation (1).

The heat pump installation (2) according to the invention shown in figure 3 is largely identical to the heat pump installation (1) shown in figure 1, but here it concerns a transcritical heat pump cycle in the first refrigerant circuit (100) and a condensing heat pump cycle in the second refrigerant circuit (200). Supplied medium (10) to be heated is here heated (11-12) by means of the fifth heat exchanger (41) and then heated further (13-14) in series at least partially (13) by means of the second heat exchanger (40). The remaining part (20) is heated further (15-16) at least partially (15) by means of the fourth heat exchanger (43) and for the remaining part leaves the installation (31). The part-flow (16) heated further by means of the fourth heat exchanger (43) leaves the installation (32) at least partially (17) and, for the remaining part (21), is combined (21+14) with the part-flow (14) heated further by means of the second heat exchanger (40) and leaves the installation (33).

Correctly controlling the mutual ratios of the part-flows (11-21) of foe medium, the flow rates of the refrigerants (50,51) and foe pressures and temperatures of the refrigerants (50,51) when leaving the compressors (101,201), and thereby the amount of heat exchanged in foe heat exchangers (40-43), enables the flow rates and temperatures of heated medium (30-33) leaving the installation (1,2) to be controlled as desired within relatively wide ranges, wherein a maximum amount of heat can be extracted from the first refrigerant and an optimal COP of the whole heat pump installation (1,2) can be achieved.