HIGH-EFFICIENCY HEATING UNIT FOR PRODUCING HOT WATER

Abstract: High-efficiency heating unit for producing hot water, which includes in combination a heat pump (1) which exploits the thermal energy of the sun and/or that of the environmental air for heating water or for producing sanitary water, namely warm water, and an electric burner or boiler (2) for possible supplementary heating of the heated water or water preheated by the heat pump and designed either to be supplied to a heating system or for sanitary use.

Description: The present invention relates to a high-efficiency heating unit for producing hot water in combination with a heating/conditioning system. Outdoor hot water generators suitable for exploiting solar radiation striking the exposed generator surface have already been proposed. Such generators can have good performance only with prolonged insolation but their efficiency drops considerably in adverse atmospheric or meteorological conditions. Thus, such generators have been used as single groups for the production of sanitary water mostly during good insolation periods. However, users had to use an outdoor sanitary water generator during the hot season and a conventional indoor heating unit for producing hot water to be used during cold periods for their heating system. Apart from economic considerations on the entity of capital investment for two separate generator groups, suggested solutions up to now are not suitable for fully taking advantage, at least during the cold season; of the environmental heat resources which are not at all negligeable. A heating unit for buildings is disclosed by DE-A-31 02 286, the known heating unit including a heat pump with a compressor for a heat conveying fluid, an evaporator in contact with the environmental air, an additional heater, a storage tank designed to supply the additional heater with hot water and fluid condenser (for the heat conveying fluid) immersed in, and in heat-transfer relationship with the water in the storage tank. A similar unit is disclosed by DE-A-35 00 252, which however replaces the additional heater known from DE-A-31 02 286 and provides instead for a water-to-water heat exchanger located within its water storage tank. A high efficiency apparatus for producing thermal power is disclosed by EP-A-0 082 825. The known high efficiency apparatus includes a heat pump with compressor, a condenser, an evaporator circuit and a water tank. However, these known units also fail to provide for an efficient solution if used in adverse meteorological conditions. Furthermore, said known units fail to interact with the building conditioning system so as to provide for a rational energy use. Given this situation, the aim of the present invention is to eliminate or drastically reduce the shortcomings known from prior art devices for the benefit of economy and more rational use of environmental heat resources. The above aim, and other aims and objects which will become apparent hereinafter are achieved by a high-efficiency heating unit for producing hot water as defined in claim 1. Further aspects and advantages of the present invention will better appear from the following detailed description of its principle of operation and of a preferred, but not exclusive, embodiment thereof illustrated by way of non limitative example in the accompanying drawings, in which: Figure 1 shows a schematic view illustrating the components and the operation of a heating unit according to the invention; Figure 2 is a perspective view of an embodiment of a heating unit according to the present invention; Figure 3 shows a diagrammatic vertical axial section view of the heating unit of Figure 2; and Figure 4 shows a diagrammatic exploded view of the heating unit of Figures 2 and 3. With reference to the drawings in which the same or similar components have been indicated with the same reference numerals, a heating unit according to the present invention essentially comprises a heat pump generally indicated at 1, an electric or fuel fired boiler 2 and a water storage system 3. The heat pump 1 comprises: a motor-driven compressor 4 designed to compress a heat conveying fluid such as Freon; a solar evaporator 5 which is placed upstream of the compressor and, in use, can be exposed and hit by a surrounding air flow; a condenser 6 for the fluid, placed downstream of the compressor and constituted by a fluid-water heat exchanger placed in the tank 3; as well as an expansion valve 7 inserted on a pipe 8 which connects the condenser 6 to the evaporator 5. Advantageously, the laminar or expansion valve 7 can be controlled by a thermostatic sensor 9 and a pressostatic sensor 10. Furthermore, the valve 7 is preferably bypassed by a safety valve 12. On the pipe 8 a dehydration filter 13 for the heat conveying fluid can be provided upstream of the expansion valve 7 and the safety valve 12. At the inlet of the evaporator 5 a three-way valve 14 is provided, which is connected to the pipe 8, the evaporator 5 and a pipe 15 from an auxiliary heat exchanger 16, that will be described further on. The evaporator outlet communicates with a pipe 17 on which a safety valve 18 can be placed. Pipe 17 branches out at 19 in one or more section 20, each leading to a respective air-fluid heat exchanger 21 which is arranged to receive air blown in from one or a respective fan 23, and in a section 24 in which a check valve 25 is provided. The arrangement is such that the air blown in by the fan or fans 23, passes through the heat exchanger 21 and hits the solar evaporator 5. Pipe 24 communicates at 26 with the outlet pipe 27 of the compressor 4, whereas the outlets 28 of the heat exchangers 21 join into a pipe 29 which before reaching the compressor inlet 30 can lead to an on-off valve 31 and a liquid separator 32 connected in series. Upstream of the valve 31 of the pipe 29 a section 34 branches off which supplies heat-conveying fluid to the heat exchanger 16. For safety reasons, the compressor 4 can have a pressure switch 35 both at its inlet and outlet 27. The latter reaches the top of the tank 3 to feed the condenser-heat exchanger 6. Tank 3 is coated with one or more layers of insulating material, such as foamed polystyrene. Advantageously tank 3 can be enclosed in a jacket which delimits a chamber for the insulating material. Tank 3 is fed with water, e.g. by a heating system, through an inlet duct 36 on which a three-way valve 37 is provided and stored up water is let off through an outlet duct 38 which supplies a first inlet of the boiler 2. In tank 3 there is also a water-to-water heat exchanger 39 which receives water from a water system through a duct 40 and supplies a second inlet of the boiler 2 through a tube 41. The boiler 2 can be a conventional hot water generator, e.g. a gas boiler or an oil-fired boiler or an electric boiler, or any other suitable generator. The generator or boiler 2 can be controlled by control means, such as a thermostat (not shown) which sets the generator in operation only if the temperature of the water coming from one of the ducts 38 or 41 is lower than a predetermined threshold level. Generator or Boiler 2 has two outlets: an outlet 42, which discharges water supplied to the generator through its inlet pipe 38 and is connected to the delivery of a heating system, and the other outlet 45 which, for example, discharges water from the inlet 41 and is connected to the inlet 46 of a sanitary water distribution system. Advantageously, from the outlet 42 downstream of a check valve 48 a tube 49 branches off at a point 47 and is connected to the heat exchanger 16 arranged for conditioning or anyway for auxiliary purposes. The outlet connected to tube 49 of the heat exchanger 16 leads to the three-way manual valve 37 through the pipe 50. The operation of the heating unit described above is as follows. Once the motor of the compressor 4 has been connected to the mains and the necessary hydraulic connections made, water in the tank 3 heats up owing to the heat pump (heat exchanger 6). During the hot season the heat pump also heats up the cold water which passes through the heat exchanger 39 and is fed into 46. Should the water temperature in the duct 41 not reach a predetermined threshold level, the generator or boiler 2 is activated for supplying additional heat to it and raising its temperature. During the cold season the tank 3 can also act as a plenum chamber for the water of the heating system. Warm water from the tank 3 through the outlet 38 is heated up to a suitable temperature, e.g. 50°-85°C, by the generator 2 before being discharged through the outlet 42, i.e. mainly to the heating system from where it returns through pipe 36 and valve 37 and possibly partly through the heat exchanger 16. During the hot season the heat exchanger 16 can act as a conditioner or cold source for any water coming from the heating system through the valve 37, since the heat conveying fluid of the heat pump will remove heat from the heat exchanger 16, and thus water passing through the pipe 49 and fed to the heating system is colder than the water fed to the heat exchanger 16. Figures 2 to 4 show a practical embodiment of the invention in which the tank 3 is cylindrical in shape and is divided, by a top sealing partition 57, into two compartments, a lower compartment 55 and a higher one 56. The compartment 55 acts as a water storage and accommodates the condenser 6 and the heat exchanger 39, whereas the upper compartment 56 receives the generator 2, e.g. comprising a gas burner 58 and a boiler 59 arranged above it. On top of the compartment 56 extends a stack 65 for discharging the burner flue gases. The tank 3 is laterally and externally wrapped throughout its length in an insulating jacket 66. On the bottom of the compartment 55 insulation is provided by a false bottom 67, whereas a second insulating partition 68 is provided on the top underneath the burner 58, but externally to the partition 57. In this way the compartment 56 is also thermally insulated except on its top where it is at least partly closed by a cap 69 through which the stack 65 extends. The outer surface of the jacket 66 is preferably chromium plated and uneven or rough for a more efficient reflection of solar light. Around such a surface, there is spirally wound the solar evaporator 5 which can thus absorb by reflection and conduction most of the heat gained by the jacket 66. At a certain distance around the evaporator 5 an external transparent cylinder is provided, e.g. made of plexiglass which, with jacket 66 and coil 5, delimits an annular gap or tunnel 70 which produces a greenhouse effect and is closed on its top by means of a lid 75, e.g. made of fibreglass, bearing a small dome 76 under which outlet slits 77 are provided. The tank 3 rests on a base 78, e.g. having a roughly truncated pyramidal shape, which also supports a fibreglass ring for supporting the transparent cylinder 70 and encloses and houses the remaining components of the heating unit, that is to say: the compressor 4, the separator 32, the two fans 23 and the heat exchangers or dynamic evaporators 21, suitably arranged one opposite the other to create a rising air flow through the gap or tunnel 70, as well as all the other electric parts of their respective controls 80. The control instruments are advantageously protected by a transparent lid. The base 78 can rest on small legs 81. With the above described arrangement the solar evaporator 5 is positively assisted, during the cold season, by the air flow fed in from outside by the fans 23. Such air flow passes throughout the heat exchangers 21, is forced through tunnel 70 and flows onto the relatively large exposed surface of the evaporator to which it can give off heat before being discharged through the slits 77 under the domed lid 75. If desired, the air current through tunnel 70 can also act as a cooling medium which can be exploited according to user's needs. As one can appreciate, a heating unit according to the present invention actually meets the requirements of providing a very high energy saving in the production of hot water and for domestic and industrial heating. Moreover, such a unit is extremely versatile since it can provide hot water for a heating system or sanitary water for a building or act as a conditioner-refrigerator arranged to feed a heating system with water at a lower temperature than that of the environment. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included just for the sole purpose of increasing intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: A high-efficiency heating unit for producing hot water in combination with a heating/conditioning system comprising at least one heat pump (1) with a respective motor-driven compressor(4) for a heat conveying fluid, a solar evaporator (5) which, in use, can be hit by environmental air, an expansion valve (7) for the fluid, a boiler (2), a water storage tank (3) designed to supply the boiler (2) with hot water, at least one heat-conveying fluid condenser (6) immersed in, and in heat-transfer relationship with the water in said water storage tank (3), and a water-to-water heat exchanger (39) located in said water storage tank (3) and arranged to receive cold water which is preheated by absorbing heat from the water in said storage tank (3) before being conveyed to said boiler (2), wherein an auxiliary water-fluid heat exchanger (16) is arranged between said solar evaporator (5) and said water storage tank (3) for heating the heat conveying fluid before being supplied to said solar evaporator (5) absorbing heat from water from said heating/conditioning system. A heating unit as claimed in claim 1, characterized in that said boiler (2) has a first water inlet (38) coming from the said storage tank (3) and a first water outlet (42) for discharging hot water, as well as a second water inlet (41) connected to said water-to-water heat exchanger (39) and a second water outlet (45) for discharging sanitary water. A heating unit as claimed in claim 2, characterized in that it comprises control means acting in response to water temperature at one or both outlets (42, 45) of said boiler (2), thereby letting said boiler (2) in operation when the water temperature is lower than a predetermined threshold level. A heating unit as claimed in any previous claim, characterized in that said evaporator (5) is placed in, and separated from, a transparent casing which together with it delimits a gap or tunnel (70) in which a greenhouse effect is formed during insolation hours and through which environmental air can flow. A heating unit as claimed in claim 4, characterized in that it comprises at least one fan (23) for forcing environmental air through the said gap or tunnel (70). A heating unit as claimed in claim 5, characterized in that it comprises at least one auxiliary heat exchanger (21) between the heat-conveying fluid and air which is arranged upstream of said compressor (4) and through which the or each fan (23) causes air to flow before reaching the said gap or tunnel (70). A heating unit as claimed in any previous claim 4 to 6, characterized in that the said evaporator (5) is arranged on an insulating cover (66) of said storage tank (3) and said casing accommodates and envelopes both the tank (3) and the evaporator (5) and includes at the top thereof a protection cap (76) for discharging air from the gap or tunnel (70).

Inventors: MELZI, OMAR
Applicants: ITALCLIMAX S.R.L.
Application year: 1987
Main classification: F24D3
IPC codes: F24D3, F24H4