NO772954L - HEAT RECOVERY SYSTEM. - Google Patents

Description

Heat recovery system

This invention relates to a heat recovery system.

It is previously known to use heat pumps to extract useful heat from the ambient heat, such as solar energy collected by means of a heating panel.

One of the purposes of the invention is to provide an improved heat recovery device for optimal utilization of the surrounding heat or waste heat, particularly, but not exclusively, in connection with the collection of solar thermal energy for heating rooms or water.

In accordance with the invention, a heat recovery device is provided comprising a heat pump which has a closed coolant circuit comprising a throttle device, a compressor and a condenser upstream of the throttle device and an evaporator downstream of the throttle device, where the evaporator is arranged, in or forms part of. a heat collector for ambient heat or waste heat, as well as an air inlet duct which is in communication with the inside of the collector to direct the air through the collector and over the evaporator used in the device, where the compressor and/or at least part of the condenser or of a refrigerant pre-cooler is in direct heat exchange relationship with the collector or with the air inlet duct for precooling the refrigerant on the upstream side of the throttle device when the device is in use.

The precooling of the refrigerant upstream of the throat device increases the density of the refrigerant and thus the efficiency of the heat pump while it increases the temperature of. the refrigerant vapor in the evaporator, so that rimming on this is avoided. The heat collector preferably comprises a hollow collector panel for solar heat which has a light-permeable wall or window and which surrounds a winding or heat exchanger which acts as an evaporator.

The low temperature of the refrigerant passing the evaporator increases the efficiency of collecting heat with the help of the solar panel.

When the system is in use, the translucent wall or window in the panel lets the sun's radiant heat through and the heat is absorbed by the evaporator. The wall or window is impermeable or opaque to the relatively long-wave radiation emitted by the heated panel. This effect is known as the greenhouse effect which increases the heat collected by the solar panel.

The air flow over the evaporator in the panel further increases the evaporator's heat absorption, and in a preferred practical embodiment of the invention, the collection panel for solar heat in the form of a low or shallow house is arranged in a suitable position, e.g. on a wall or roof of a building. The air flow through the panel can be ambient air or warm air obtained either with the help of solar heating or waste heat. Thus, in a preferred embodiment of the invention, the panel is mounted on the roof of a building and the air flow through the panel is drawn from an attic or a roof space by means of one or more fans. In this way, solar heat that has been absorbed by the building's roof can be utilized and transferred to the air in the underlying attic or roof space. Such a device is particularly applicable in houses that are made with a pitched roof where. there is a significant volume of air under the roof. The vaporizer can. have corrugated surface cladding that faces the light-transmitting wall or window of the panel, so that turbulent flow is produced in the refrigerant in the evaporator's channel for maximum absorption of radiant heat from the sun's rays falling on the panel. The pre-evaporator surface facing the aforementioned wall or window will in practice have a matt black finish to increase the heat absorption coefficient.

The throat device may comprise an expansion valve, et

capillary tube or other pressure control device.

Alternatively or in addition, the air flow through the panel can be heated with waste heat, e.g. heat .from the heat pump's compressor or waste heat from any other source, e.g. heat from overproduction of hot water in an air conditioning system. In one embodiment of the invention, at least part of the coolant precooler or of the condenser is placed in the air inlet duct for heating air that enters the collector when the system is in use. Alternatively or additionally, the compressor can be placed in the air inlet duct to heat the air

. which goes into the collector when the system is in operation.

Preferably, at least one fan is arranged in the air inlet duct. Thus, the channel can comprise a centrifugal fan which is supplied with air by means of at least one axial fan. The air inlet duct preferably has at least a converging throat section between the or each fan and the interior of the heat collector.

In practice, this has proven to be a particularly quiet and efficient device.

To further increase the heat efficiency of the system, the heat pump's compressor can be enclosed in a housing that is immersed in liquid in a tank. Furthermore, the heat pump's condenser may comprise a winding which is submerged in said tank and which surrounds the compressor housing, where both the compressor housing and the condenser winding are preferably located at the bottom of the tank. At its lower end, the condenser winding can be converted into a storage winding which acts as a container for the refrigerant liquid when the system is switched off. The coolant circuit can be completed in that the heat pump's evaporator is connected to the interior of the compressor housing, and that the surrounding tank contains a heat exchange liquid, such as water.

Alternatively, the compressor housing, which can also enclose a drive motor, can be arranged in a tight tank which is passed by the refrigerant sub-fluid at a sub-ambient temperature on its way from the evaporator before it enters the compressor, so that the waste heat produced in the compressor and its drive motor is absorbed by the refrigerant. The compressor housing can e.g. be equipped with a coolant inlet that opens into the tank, so that the compressor draws in the coolant after it has taken heat from the compressor.

In another embodiment of the invention, a heat recovery system is provided which comprises a heat pump which has a closed coolant circuit. which in turn comprise throttle devices arranged in series, such as an expansion valve, an evaporator, a compressor and a condenser, where the evaporator is arranged in or forms part of a collector for collecting ambient heat or waste heat, and where the compressor is connected to the throttle device through a high pressure refrigerant line which is in heat exchange relationship with at least one space heater and which, when the system is in use, acts as at least part of the condenser or of a refrigerant precooler. In this embodiment of the invention, the refrigerant that leaves the compressor at high temperature and high pressure gives off its heat to the space heater or heaters that are passed by the high-pressure line, so that the refrigerant is condensed and cooled and enters the throttle device at a temperature that is only slightly above the ambient temperature. The refrigerant leaving the throat device and flowing into the evaporator is at a sub-ambient temperature so that the refrigerant can absorb heat from the surroundings including e.g. solar heat from the radiation acting on the heat collector. It will be noted that the use of a separate condenser winding or heat exchanger which usually occurs in most heat pump installations is not necessary in this embodiment, because the high pressure line which is in heat exchange relationship with the space heater or heaters can serve as a condenser.

The space heater or heaters are arranged to receive heat from the refrigerant high-pressure line and may comprise at least one air heater for natural or forced convection, e.g. in the form of a vertical channel in which a winding which forms part of the refrigerant high-pressure line is arranged and which is passed in an upward direction by the air to be heated. Alternatively or in addition, the space heater or space heaters may comprise at least a flat, hollow radiator which is filled with a heat-absorbing medium and which is arranged vertically, and where the coolant high-pressure line is led through a lower part of the radiator in heat exchange conditions with and tightly bounded from the medium in the radiator. Such a radiator can e.g. include a hollow skirting board that is filled with a liquid or other heat-absorbing medium. The heat-absorbing medium can be a refractory heat storage material, in which a line forming part of the high-pressure line is incorporated.

In those cases where, as previously mentioned, the compressor and/or part of the condenser is immersed in a tank filled with liquid, usually water, the water in the tank will be heated independently of the heating of the space heater or heaters and can f .ex. form part of the hot water supply to heating radiators or space heaters in one separate circuit from the heat pump's cooling circuit.

The invention shall be explained in more detail below by means of examples and with reference to the drawings, where: Figs. 1, 2 and 3 are simplified circulation circuit diagrams illustrating systems for recovering solar heat in accordance with three different embodiments of the invention for house heating, fig. 4 and 5 are perspective sketches with some parts removed showing two examples of solar heat collection panels and air introduction units that can be used in systems according to the invention, and fig. 6 shows a perspective and disassembled state of a solar heating panel. to use

. in the system according to fig. 3.

Fig. 7 schematically shows a vertical section through a liquid storage tank and compressor unit which forms part of the system according to fig: 3, fig. 8 illustrates a further embodiment of the invention', and fig. 9 is a schematic perspective view showing

a space heater with some parts removed that can be used in the system according to fig. 1 or 2.

In the drawings, the same reference numbers are used for

the same parts occurring in different embodiments of the invention.

A domestic heating system shown in fig. 1, has two flat radiator panels 1 each of which has a sealed metallic casing which is fixed vertically in a room and which contains a heat-absorbing liquid, such as water.

A coolant high-pressure line 2 extends through the bottoms of the panel radiators 1 and passes these in sequence and is sealed at the inlet and outlet to respectively. from the radiators 1 and

the parts of the line 2 that are inside the radiators are then in a heat exchange relationship with the liquid in the radiators. The high-pressure line 2, which in practice can be a copper tube with a diameter of 12 mm, is connected to the high-pressure outlet of a compressor 3 driven by an electric motor which is arranged in a sealed housing 4. The compressor 3 has a service inlet valve 5 which opens to the internal of the housing 4. After the high-pressure line 2 has passed the radiators 1, it draws to a throttle device 6. placed at the inlet end of a solar heat collection panel 7, while the low-pressure side of the throttle device 6 is in connection with a heat exchanger (not shown) inside the panel 7 which acts as a vaporizer. The evaporator's outlet is connected to the inside of the housing 4, which is in turn connected to the compressor's 3 inlet 5 and thus the heat pump's refrigerant circuit is closed.

The heat collection panel 7 is placed on the roof or wall of

a building in such a position that the panel can receive the sun's radiant energy.gi. The panel's 7 outer surfaces will in practice be painted with matt black paint to increase the heat absorption coefficient.

When the system is in use, the refrigerant (appropriate refrigerant type R12 or R22) circulates in the closed circuit

which includes the line 2 and the throttle device 6. The latter is set and thermostatically controlled so that the temperature in the refrigerant partial vapor that flows into the evaporator in the heat collection panel 7

from the throat device, 6 is approximately -2°C, i.e. slightly below the freezing point and so that the refrigerant leaving the panel 7 has a temperature

temperature of approximately 3°C below ambient temperature. The collection panel 7 will therefore be kept at a temperature which is significantly lower than the ambient temperature and will therefore be able to absorb heat from the surroundings and from the solar radiation that hits the panel. After the heat has been absorbed in the evaporator, the refrigerant vapor at a temperature equal to or slightly lower than the ambient temperature will flow to the inlet of the compressor 3, where the refrigerant is compressed and which will then leave the compressor 3 at a high pressure, e.g. 21 kg/cm^, and high temperature, e.g. 78°C. The coolant gas at high temperature is condensed when it passes through the high-pressure line 2 in the panel radiators 1 and emits heat to the liquid in the radiators, so that the coolant liquid that enters the throat device 6 has a temperature that is only slightly above the ambient temperature. In reality, therefore, the high-pressure line 2 passing the radiators 1 or other heat-absorbing devices will serve as a condenser in the refrigerant circuit.

It will be seen that the system is similar to the existing "mini-bore" central heating systems except that it is not hot or heated water, but hot coolant liquid circulating through the high-pressure line 2.

The system's operating temperature can be controlled by means of a high-pressure-sensitive switching valve in the high-pressure line 2 arranged to close when the pressure in the line 2 exceeds a certain limit (e.g. 21 kg/cm 2 ) which corresponds to a desired maximum operating temperature (e.g. .78°C-82°C). In addition, there will be a thermostat to switch off the compressor motor if the water in the tank gets too hot.

The temperature of the coolant in the heat collector 7 can be regulated by setting the thermostatically controlled throttle device 6, so that the setting of the valve 6 is adjusted automatically in accordance with the ambient temperature at the panel 7, so that it is ensured that the coolant that passes the evaporator always has a temperature that is below ambient temperature. In practice, the refrigerant circulating in the evaporator in panel 7 can be cooled down to -6°C.

The sealed housing 4 containing the compressor 3 receives gaseous or vapor refrigerant from the heat collection panel 7, usually at a temperature of 28°C. The compressor 3 is operated with the inlet 5 in open connection with the housing 4 inlet and draws refrigerant gas from the housing 4. As the gas has a lower temperature than the compressor itself, the compressor unit cools and the refrigerant gas enters the compressor in an overheated state. In this way, the waste heat from the compressor is absorbed by the refrigerant and utilized in the system.

Fig. 2 shows an alternative system according to the invention

and the same reference numbers are used in the figure for the same or corresponding parts. In this system, the sealed housing 4 contains the compressor 3 which is arranged at the bottom of a water heating tank 8. and a heating coil 9 is connected to the outlet of the compressor and is placed in the lower area of the tank 5 for heating the water in the tank. Hot coolant liquid which has circulated through the coil 9 is fed into the line 2 which in this case comprises a chamber armer 10 arranged in series, a pre-cooling coil 11 which is connected to the high pressure side of a throttle device comprising a ter-. statically controlled expansion valve 6, and whose low-pressure side is connected to an evaporator 19 in a solar heat collection panel 7. The evaporator 19's outlet is in connection with the interior of the compressor housing 4 and thus

with the compressor 3' inlet 5 to complete the refrigerant sub-circuit.

The winding 11 is arranged in an air inlet channel 12 which is

in connection with a roof space or gayel room in a building as close as possible to the roof ridge. A fan 13 sucks air from this space over the winding 11 and over the surface of the evaporator channel in the panel 7 as shown by arrow A. A glass window 14 forms the top of the panel 7 and defines a tight enclosure through which the fan 13 pumps the air.

When the system according to fig. 2 is in use, cold refrigerant gas circulates through the evaporator 19 in the heat collection panel 7 after leaving the expansion valve 6. The refrigerant absorbs both the radiant heat from the radiation that hits the panel 7 through the window 14 and the heat from the hot air that circulates through the panel 7 with the help of the fan 13 After the hot compressed refrigerant gas has left the compressor 3, it passes the winding 9 where it condenses and heats the water in the tank 8 and then flows through the conduit 2 to give off heat to the space heater 10. Any excess heat in the refrigerant liquid is removed by the air which is blown over the pre-cooling winding 11. Any non-condensed refrigerant is condensed in the winding 11 and in reality the winding 9, the line 2 and the winding 11- can be considered as a condenser in the heat pump's refrigerant circuit.

The space heaters 10 in the designs according to fig. 1 and 2 can be convection panel radiators made for rapid heating of a

air space. Such a pahel radiator is shown schematically in fig.9.

A winding 15 which forms part of the line 2 for the protected refrigerant part is connected to one side of a front plate 16 made of metal, which on the back has a reflector plate 17 which together with the front plate 16 forms one vertical air channel. Alternatively, the winding 15 in the radiator 10 can be embedded in a solid material ■ with a large heat capacity to form a heat condenser or a magazine heater.

The water in the tank 8 is quickly heated by the winding 9 and emits heat to conventional hot water radiators 18 in a hot water system which is separated from the coolant circuit.

It is a well-known fact that an increase in the condensing temperature is accompanied by a dramatic reduction in the efficiency of a cooling system or heat pump. The consequence is that the condensation temperature must be kept as low as possible and the evaporation temperature as high as possible.

Fig. 3 shows an alternative system according to the invention. In this case, the tight housing 4 containing the compressor 3 is arranged at the bottom of a water heating tank 8, and a heating winding 9 which forms a pre-condenser in the heat pump circuit is connected to the high-pressure outlet from the compressor 3. The winding 9 coaxially surrounds the compressor housing 4 and is located in the lower part of the tank 8

for heating the water in the tank. Hot coolant liquid that has passed the coil 9 passes the pre-cooling coil 11 which in this embodiment is placed under the panel 7 and in heat exchange relationship with an evaporator coil 19 which is schematically shown by a dashed ■ line in the panel 7.

A fan 13 sucks air from the attic or roof space into an air inlet channel 12 which is in connection with the interior of the panel 7. A glass window 14 forms an upper light-permeable wall in the panel 7 and delimits a tight enclosure which is passed by ambient air which is pumped through by means of the fan 13.

When the system according to fig. 3 is in use, cold refrigerant vapor passes the evaporator coil 19 in the solar heat collection panel 7 downstream of the expansion valve 6. The refrigerant absorbs heat both from the solar radiation that hits the panel 7 through the window 14

and from the hot air that is transported over the evaporator coil 19 by means of the fan 13 before the refrigerant enters the compressor .3. After the refrigerant has left the compressor 3, the hot refrigerant gas heats the water in the tank 8 by means of vik- . the winding 9 and is condensed in the winding 9. Any excess

heat in the coolant liquid is transferred through the pre-cooling coil 11 to the evaporator coil 19 to reduce the risk of icing or riming on. the evaporator as a result of its low working temperature. The precooling of the refrigerant during the passage of the winding 11 upstream of the expansion valve 6 also increases the density of the refrigerant and thus improves the cooling effect produced by the expansion valve 6.

An electric air heater in the form of a encapsulated resistance heating element 20 of 2 kw can, as shown schematically, be incorporated into the air inlet channel 12 for preheating the air that enters the solar heat collection panel 7 for defrosting the evaporator coil 19 in the event of high humidity in the atmospheric air. Automatic defrosting can be provided by connecting the heating element 20 to a control device (not shown) which is in connection with a timer and which switches the compressor 3 a-v and turns the heating element 20 on for a short period, usually 10-15 minutes, on a pre-determined -.set time or times during the day for periodic defrosting. The control can be switched off using a main switch when humidity is low and in summer.

The water in the tank 8 is heated quickly by means of the winding

,9 and the waste heat from the compressor 3. Hot water from the tank 8 is supplied to ordinary • hot water radiators 19 in a closed hot water circuit or hot water circuit which is separated from a hot water supply provided by means of a hot water storage cylinder 21.

When the system is in operation, the normal temperature of the coolant at the pre-cooling coil 11 (not shown in Fig. 4) is approximately 50°C when it comes to normal operating systems, while the air leaving the heat collection panel 7 will have a slightly lower temperature than the ambient temperature as it gives off its heat to the evaporator coil 19.

The thermostatic control of the expansion valve 6 is such that the degree of opening of the valve is made dependent on the ambient temperature, and the control for the valve is provided by means of a temperature element which is placed in the roof space. On a hot day, the valve 6 will be open, so that more refrigerant will pass and a relatively high evaporator temperature can be achieved, while on a cold day the valve will seek to close the passage, so that a lower evaporator temperature is obtained, which in both case results in the greatest possible degree of efficiency for the plant.

Fig. 4 shows a practical embodiment of a collection panel for solar heat for use in a system according to the invention, as shown in fig. 3.

The air inlet duct 12 is arranged in the roof or in the attic of a building and has two side inlets, each of which is equipped with an axial fan 22 which, through two side inlets, sucks air from the roof space or the attic space into a central collecting comb 23, namely through two converging inlet neck sections 24. A centrifugal fan 25 . is placed in the central collecting comb 23 and guides the air through a diverging channel. 26 through the upper edge of the panel 7 into the panel. The air is blown downwards, over the evaporator winding 19 in the panel 7 and out into the atmosphere through air openings not shown in the lower part of the panel. This air introduction system has proven to be relatively noiseless in operation.

Fig. 5 schematically shows another collection panel for collecting solar heat and an air introduction unit for use in the system as shown in fig. 3.

A hollow, rectangular solar collector panel .7 is designed to be placed on the roof of a building at an angle to the horizontal. The panel 7 is covered with glass or has a light-transmitting window 14 and in the panel there is arranged a heat exchanger (not shown) which forms the heat pump's evaporator, and in which a coolant liquid circulates continuously with the help of a compressor 3 which is enclosed in a sealed housing 4 The compressor 3 and evaporator are connected in a heat pump circuit in a manner that may be shown. fig.2 or 3.

In this embodiment, the compressor housing 4 is placed in a vertical air inlet channel 12 which is connected to the upper edge of the hollow solar panel 7 through a diverging connection channel 26, while the lower edge of this inner channel is open to the atmosphere. The lower end of the air inlet duct 12 is in connection with the outlet of a centrifugal fan 25 which has two axially arranged, opposite

.directed inlets which, through respective converging neck portions 24, are in connection with each axial fan 22, as in the device according to fig. 4. The fans 22 and 25 are driven from a single electric motor or from separate electric motors. The fans 22 and 25 suck stagnant warm air from an attic or roof space of a building into the inlet duct 12 and force the air to flow over and absorb the heat from the compressor housing 4 and from there to flow through the duct 26 into the inner duct of the solar panel 7. When the air flows through the panel 7, heat is transferred

from the air to the evaporator, which thus receives heat directly from the solar radiation on panel 7.

In practice, various devices can be used to improve heat transfer between the compressor housing 4 and the air in the duct 12. The compressor housing can e.g. be equipped with external fins over which the air will flow when it passes the channel 12.

The arrangement whereby the compressor housing 4 is enclosed in the inlet duct 12 effectively reduces the noise produced by the compressor unit when the system is in operation. •

Fig. 6 shows an embodiment of the collection panel 7 for use in a system shown in Fig.'3. The panel has lower and upper walls 27,28 of heat-conducting metal, where the upper wall 27 is provided with a black matt finish. For the sake of clarity, the glass window 14 is not shown in fig. 6, but is supported above and parallel to the upper wall 27, so that the sun's trawl falls on the upper wall 27-. A heat exchanger 29 is arranged in the space between the walls 27 and 28 and is connected in series with two windings 30 respectively. 31 which are connected in parallel with each other with an inlet connection which is aity-that of the arrow I., and the heat exchanger 2? is connected by an outlet connection as indicated by the arrow 0. The windings 30 and 31 are arranged in thermal contact with the inner fins of the walls 27 and 28 respectively. The heat exchanger 29 has a number of parallel fins 32 which extend over the gap between the walls 27,28 and which form intermediate air passages for guiding the air, through the panel from the air inlet channel 12. The inlet edge of the panel is shown on the left in Fig. 6. When the air passes the passages formed by the fins 32 between the walls 27 and 28, it emits heat to the refrigerant flowing through the evaporator or heat exchanger 29 and through the windings 30 and 31.

A pre-cooling winding 11 is attached to the bottom outer surface of the lower wall 28 and is covered with a layer 33 of thermally insulating material, and the winding 11 and the layer 33 are enclosed in a bottom cover 34. This device ensures that the pre-cooling winding 11 supplies heat to the evaporator winding 31 mainly through the wall 28.

Fig. 7 and 8 show two alternative devices for heating water using heat recovery systems in accordance with the invention, e.g. in domestic hot water systems or central heating systems and of the type shown in fig. 2 or 3. Fig. 7 shows an open tank 8 which is enclosed in a thermally insulating jacket 35 and which is supplied with cold water through an inlet 36 in connection with a ball float valve 37 which maintains a constant water level in the tank 8. A compressor unit comprising a compressor and the compressor's drive motor, are enclosed in a tight cylindrical housing 4 which rests on the bottom of the tank 8. The condenser winding 9 coaxially surrounds the housing 4 and is connected through the housing 4 to the outlet of the compressor. Electrical connections to the compressor's motor comprise the power supply through a line 38 which has a tight passage to the housing 4.

Fig. 8 shows an alternative system according to the invention placed in a roof space or attic space. In this case, the capacitor winding 9 is arranged as in the embodiment according to fig. 7 in a tank 8 with an open top, which is kept filled with water and where the water level is controlled by a float valve 37. In this case, however, the sealed compressor housing 4 is placed in a separate, sealed copper tank 39 which is filled with coolant liquid that comes directly from the solar panel's 7 evaporator channel 8. The compressor housing 4 has an open inlet valve 5' in connection with the interior of the surrounding refrigerant sub-tank 39 to receive the refrigerant from there..

In systems where it is not possible to utilize the roof space, the water circulation system can be closed and the tank 8 can be replaced with a closed and sealed copper cylinder.

The devices shown in fig. 7 and 8 for heating water, can suitably replace the existing domestic hot water systems or central heating systems with only minor modifications and additional plumbing work.

The system described in connection with fig. 2 and 3 can, after appropriate setting of the thermostatic expansion valve 6, be operated to cool the air during its passage through the heat collector panel 7 sufficiently for air conditioning purposes, in which case a further channel will be in connection with the air outlet side of the panel to conduct cooled air to the air conditioning system's channels. The cooling of air by means of the heat pump system in this way would inevitably result in the production of a significant amount of hot water as a result of heat exchange in the condenser windings 9 and 11. If this water were to prove superfluous in relation to the requirements, it could be used as a heat source in an absorption refrigeration circuit and thus utilized to produce additional cold air for air conditioning purposes. Hot water produced by such tandem systems can, e.g. used for heating a swimming pool.

Claims (22)

1. Heat recovery system comprising a heat pump with a closed refrigerant circuit comprising a throttle device, a compressor, a condenser upstream of the throttle device and an evaporator downstream of the throttle device, where the evaporator is arranged in or forms part of a heat collector for ambient heat or waste heat, characterized in that an air inlet duct (12) is in connection with the interior of the collector (7) for conducting air through the collector and over the evaporator (19) when the system is in use, and that a precooler (11, fig. 3; 4, fig.5; 11, fig. 6) for the coolant is included in the heat pump circuit for precooling the coolant upstream of the throttle device (6) when the system is in use. 2. System according to claim 1, characterized in that at least part of the refrigerant precooler or of the condenser consists of a high-pressure refrigerant channel (11) which is arranged in a heat exchange relationship with the evaporator. (19). 3. System according to claim 1, characterized in that at least part of the coolant precooler or of the condenser is arranged in the air inlet channel (12) for the transfer of heat to air entering the collector (7) when the system is in use. 4. System according to claim 1, 2 or 3, characterized in that the condenser or refrigerant evaporator comprises a high-pressure refrigerant line (2) which is in direct heat exchange with at least one space heater (1). 5. System according to one or more of claims 1 to 4, characterized in that the compressor (3) is arranged in the air inlet channel (12) for the transfer of heat to air that enters the collector (7) when the system is in use. 6. System according to one or more of the preceding claims, characterized in that at least one fan (13) is arranged in the air inlet duct (12). 7. System according to claim 6, characterized in that the air inlet channel (12) comprises a centrifugal fan (25) which is supplied with air from at least one axial fan (22). 8. System according to claim 6 or 7, characterized in that the air inlet duct (12) has at least a converging neck section between the fan or each fan and the interior of the heat collector (7). 9. System according to claim 6,7 or 8, characterized in that it comprises two branch inlet ducts, each of which is equipped with an axial fan (12) and each is connected through a converging neck part (24) to the air inlet duct (12) which leads to the collector ( 7). 10. System according to one or more of the preceding claims, characterized in that an electric air heater (20) is arranged in the air inlet duct (12). 11. System according to one or more of the preceding claims, characterized in that the heat collector comprises a hollow collector panel (7) for solar heat which has a light-permeable wall or a window (14) and which surrounds a winding or heat exchanger (19) which acts as an evaporator . 12. System according to claim 11, characterized in that a high-pressure coolant channel (11) acts as at least part of the condenser or coolant precooler and is in a heat exchange relationship with the evaporator winding or heat exchanger (19) on that side of the panel (7) which is opposite the light-permeable wall or window (14). 13. System according to claim 12, characterized in that a heat-insulating layer (33) covers the coolant channel (11) on the outside of the solar heat collection panel (7). 14.. System according to one or more of the preceding claims, characterized in that the compressor (3) is enclosed in a housing (4) which is immersed in liquid in a tank (8). 15. System according to claim 14, characterized in that the condenser comprises a winding (9) which is immersed in the tank (8) and surrounds the compressor housing (4). 16. System according to claim 14 or 15, characterized in that the heat pump's evaporator (19) is connected to the interior of the compressor housing (4), which is in turn connected to the compressor's (3) inlet, and that the tank (8) contains a heat exchange liquid, such as ■ water. 17. System according to claim 14, characterized in that the tank is a tightly closed tank (39) which is connected to the evaporation • clean (19) and arranged to receive from there refrigerant, that the compressor has an inlet (5') which is in connection with the interior of the tank to receive from there refrigerant after it has absorbed heat from the compressor. 18. Heat recovery system comprising a heat pump with a closed coolant circuit which includes a throttle device arranged in series, an evaporator, a compressor and a condenser, where the evaporator is arranged in or forms part of a heat collector for ambient heat or waste heat, characterized in that the compressor (3) is connected to the inlet of the throttle device (6) through a high-pressure coolant line (2) which is in a heat-exchange relationship with a coolant precooler, e.g. at least one space heater (1) . 19. System according to claim 18, characterized in that the heat collector comprises a solar heat collection panel (7) which surrounds a heat exchanger which acts as an evaporator and through which evaporator the coolant flows after passing the throat device. 20. System according to claim 18 or 19, characterized in that the space heater or space heaters comprise at least one convection heater (15, 16, 17) for air with natural or forced convection. 21. System according to claim 20, characterized in that the air heater or each air heater comprises a vertical channel (16,17) in which a winding (15) which forms part of the high-pressure refrigerant line is arranged and through which channel air heated, flows upwards. 22. System according to one or more of claims 18 to 21, characterized in that the air heater or air heaters comprise at least one hollow, flat radiator (1) which is filled with a heat-absorbing medium and arranged vertically with the high-pressure coolant line (2) running through the lower part of the radiator in heat exchange with and sealed from the medium in the radiator.