ES2987247T3 - Combined system and process for heating a main water circuit - Google Patents

Abstract

1. Combined heating system (1) of a main water circuit (30) comprising a condensing boiler (20) and a heat pump (11, 12, 13, 14, 16). The boiler (20) has a combustion smoke outlet (23), the heat pump (11, 12, 13, 14, 16) comprises a refrigerant circuit (11) through which a refrigerant fluid circulates and a first heat exchanger (12) crossed by the circuit (11) in which the refrigerant fluid receives heat passing from a liquid to a gaseous state. The combined heating system (1) comprises a duct (40) extending between the smoke outlet (23) of the boiler (20) and said first heat exchanger (12) such that it conducts the smoke from the smoke outlet (23) to the first heat exchanger (12). (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Combined system and process for heating a main water circuit

The present invention relates to a combined system and process for heating a main water circuit. In particular, the heating system consists of a condensing boiler and a heat pump. In the industry, this combination is often referred to as a "hybrid system".

Central heating systems that simultaneously use a heat pump and a boiler are now known. In particular, the boiler is of the instantaneous condensation type.

In these systems, a main water circuit is first heated by the heat pump and then by the boiler. In particular, the heat pump consists of a cooling fluid circuit, which receives heat from the ambient air and transfers it to the water. The preheated water then reaches the boiler, where it is further heated by heat exchange with the combustion products generated by a burner.

In this context, it is known to recover heat from combustion fumes within the system. For example, patent EP2926059 (originating from WO 2014/083440 A1) shows a heating appliance comprising a condensing boiler and a heat pump. In this appliance, an air flow receives heat from the combustion fumes within a special heat exchanger. This air flow is then used in an evaporator of the heat pump to exchange heat with a refrigerant.

The main disadvantage of the solution just described is the use of a specific component to heat the air flow, which makes the device structurally more complicated. In addition, the presence of a double heat exchange (flue-air and air-cooling fluid) causes significant heat losses and consequently low efficiency.

From IT BO20 120458 A1 a heating appliance is known which aims to recover heat from flue gases, where the gases are sent to a pressurized zone.

From document CN 107 101 374 A a method is known for converting a non-condensing gas wall-mounted boiler into a deep-condensing gas wall-mounted boiler, in which the fumes are expelled by a fan.

In this context, the technical task underlying the present invention is to provide a combined system and a process for heating a main water circuit, which avoids the drawbacks of the state of the art cited above.

In particular, an objective of the present invention is to provide a combined system for heating a main water circuit, which is structurally simpler with respect to known solutions.

Another object of the present invention is to propose a combined system and a method for heating a main water circuit, in which the heat of the combustion fumes is recovered with high efficiency.

The specified technical task and the specified objects are substantially achieved by a combined system for heating a main water circuit, comprising a condensing boiler and a heat pump. The boiler has a combustion flue, the heat pump consists of a coolant circuit through which a coolant flows and a first heat exchanger crossed by the circuit in which the coolant receives heat by passing from a liquid to a gaseous state. The combined heating system comprises a duct extending between the flue of the boiler and the first heat exchanger for transporting the flue coming from the flue into the first heat exchanger.

According to one embodiment, the condensing boiler comprises a sealed chamber in which combustion occurs. The flue and the duct are inside the sealed chamber.

According to the invention, there is provided a combined system according to claim 1, wherein the combined heating system comprises a fan associated with the first heat exchanger such that the fumes exiting the duct are drawn towards the first heat exchanger.

Preferably, the combined heating system comprises a drain to the atmosphere for the flue gases downstream of the first heat exchanger.

According to one embodiment, the combined heating system comprises a domestic hot water production tank arranged along the main water circuit. The tank has an inlet for the water to be heated and an outlet for the hot water. The system comprises another heat exchanger arranged inside the tank and crossed by the refrigerant circuit to exchange heat between the refrigerant fluid and the water of the main circuit.

The stated technical task and the specified objects are substantially achieved by a combined method for heating a main water circuit, comprising the steps of:

• carry out a first heating of the water by means of heat exchange with a refrigerant fluid in a gaseous state, the refrigerant fluid passing from the gaseous state to a liquid state;

• carry out a second heating of the water by exchanging heat with the combustion fumes;

• after carrying out a second heating of the water, carrying the combustion fumes to a first heat exchanger, in which the step of carrying the combustion fumes to the first heat exchanger (1) occurs inside the sealed chamber (50);

• exchanging heat in the first heat exchanger between the combustion fumes and the liquid state cooling fluid, the cooling fluid passing from the liquid state to the gaseous state to be used in the stage of carrying out a first heating of the water.

Preferably, a wall defining the sealed chamber acts as a seal for the fumes exiting the first heat exchanger.

Preferably, the heating process comprises a step of mixing the combustion fumes with ambient air before the heat exchange step, said heat exchange step occurring between a mixture of air and fumes and the cooling fluid.

According to an example of the process, this comprises the steps of:

• accumulate water from the main water circuit;

• heat the accumulated water by heat exchange with the refrigerant fluid;

• exchange heat between the stored and heated water and a domestic hot water circuit to produce domestic hot water.

Additional features and advantages of the present invention will become more apparent from the approximate and therefore non-limiting description of a preferred, although not exclusive, form of a combined system and process for heating a main water circuit, as illustrated in the attached drawings, in which:

• Figure 1 shows a first example of a combined system for heating a main water circuit, according to the present invention, in schematic view;

• Figure 2 shows a second embodiment of a combined system for heating a main water circuit, according to the present invention, in schematic view.

Referring to the drawings, number 1 indicates a combined system for heating a main water circuit 30.

The combined heating system 1 comprises a condensing boiler 20 and a heat pump. The two devices are associated with each other to form a single combined system.

The main water circuit extends partly through the combined heating system 1 so that the water in it is heated first by the heat pump and then by the boiler 20, and then sent to a heating system. In particular, the main water circuit 30 includes a supply line 32 for hot water to the radiators of the heating system and a return line 31 for the water to the combined heating system 1.

The heat pump comprises a refrigerant fluid circuit 11, which has the task of heating the water of the main circuit 30 for the first time.

Said circuit 11 passes through a first heat exchanger 12, in which the refrigerant fluid evaporates, passing from the liquid phase to the gaseous phase. The first heat exchanger 12 is generally indicated as an "evaporator". From now on, the term evaporator 12 is used to indicate the first heat exchanger 12.

From said evaporator 12, the refrigerant fluid is sent by a compressor 13 to a second heat exchanger 14, where the refrigerant fluid is condensed from the gaseous state to the liquid state, transferring heat to the water returning from the heating system. The second heat exchanger 14 is generally indicated as a "condenser". From now on, the term condenser 14 is used to indicate the second heat exchanger 14.

In summary, the compressor 13 has the function of circulating the refrigerant fluid in the circuit 11, sucking it from the evaporator 12 in the form of gas and compressing it to lead it to the condenser 14, at high pressure. Any type of compressor 13 that involves volumetric compression can be used.

The refrigerant fluid circuit 11 also has a rolling (adiabatic) valve, which determines the pressure drop necessary and sufficient to maintain the pressure of the refrigerant fluid at the desired values of the evaporator 12 and the condenser 14.

The condensing boiler 20 consists of components of the known type, therefore it will not be described in detail. By way of explanation, the boiler 20 consists of a burner 21 in which combustion takes place generating combustion fumes, a fan 22 for supplying ambient air to the burner 21, at least a portion of the fuel gas supply pipe to the burner 21 and a heat exchanger crossed by the main water circuit 30. In the heat exchanger, heat exchange takes place between the fumes produced by the burner 21 and the water of the main heating circuit 30.

Suitably, the boiler 20 comprises a combustion smoke outlet 23.

Going into detail of the main water circuit 30, water returns from the heating system via return line 31 and passes through condenser 14, where it is heated for the first time as described above for the heat pump. The main circuit 30 then passes through boiler 20, where the water is heated a second time as described above for boiler 20. At this point, the hot water leaves the combined heating system 1 via a supply line 32, moving towards the terminals of the heating system. The terminals may be, for example, radiators or a floor system. Originally, the combined heating system 1 consists of a line 40 connected to the flue outlet 23 of the condensing boiler 20. The line 40 extends to carry the flue gases to the first heat exchanger, i.e. the evaporator 12.

In other words, in the combined heating system 1 proposed here, heat exchange takes place directly between the combustion fumes and the coolant.

According to the invention, the condensing boiler 20 comprises a sealed chamber 50, a chamber isolated from the surrounding environment, in which combustion takes place. Air is sucked in from the outside by means of the fan 43, so the sealed chamber 50 is under negative pressure.

By virtue of the conduit 40, the fumes remain in the sealed chamber 50 until they reach the evaporator 12.

Preferably, the combustion fumes exiting the duct 40 are mixed with the air surrounding the sealed chamber. The mixture of air and fumes generated is then drawn into the evaporator 12 by means of a fan 43 associated therewith. In this way, heat exchange occurs in the evaporator 12 between the mixture of air and fumes and the refrigerant fluid.

Downstream of the evaporator 12 there is a drain 42 to the atmosphere of the mixture of air and fumes.

Thus, the mixture of air and fumes, once the heat has been transferred to the refrigerant fluid, is evacuated into the atmosphere.

In the embodiment described and illustrated here, the combined heating system 1 comprises a wall 60 arranged close to the evaporator 12. The wall 60 delimits a part of the sealed chamber 50 and at the same time performs the function of an insulating or sealing panel for the gas and air mixture exiting the evaporator 12 towards the drain 42. In existing solutions, the spent gas containment function is performed by a specially provided casing around the evaporator 12.

According to one embodiment, shown in Figure 1 and described so far, the boiler 20 and the heat pump are used to serve only the heating of the water of the main circuit 30.

According to another embodiment, shown in Figure 2, the instantaneous condensation boiler and the heat pump are intended to heat the water of the main circuit 30 and to produce domestic hot water, known by the acronym SHW.

In this case, the combined heating system 1 comprises a tank 70 for producing domestic hot water. In particular, the tank 70 has the function of accumulating water from the main circuit 30 which is exchanged for the production of domestic hot water. A tank 70 is arranged along the main water circuit 30 and has an inlet 71 for the water to be heated (cold water) and an outlet 72 for the hot water. The coolant circuit 11 passes through the tank 70 and comprises a third heat exchanger 16 configured to exchange heat between the coolant fluid and the water of the main circuit.

Taking into account the extension of the refrigerant fluid circuit 11, the third heat exchanger 16 is inserted between the evaporator 12 and the condenser 14. In other words, the refrigerant fluid evaporates in the first heat exchanger 12 thanks to the mixture of air and fumes, transfers heat in the third exchanger 16 to the main water used to produce domestic hot water and subsequently condenses in the second heat exchanger 14, heating the main water returning from the heating system.

Preferably, a three-way valve 33 is arranged along the main water circuit 30. The valve 33 has an inlet 33a for the water heated by the boiler, a first outlet 33b for the delivery of the heating water and a second outlet 33c communicating with a fourth heat exchanger 34. The operation of the three-way valve 33 is of the exclusive type. In other words, the first outlet 33b and the second outlet 33c are enabled alternately and cannot be crossed by water at the same time: the incoming water is sent either to the heating system or to the exchanger 34 to produce DHW. In said fourth heat exchanger 34, the hot water transfers heat to a domestic water circuit 80. The outgoing cold water is sent to the tank 70 to be heated again.

In this embodiment, the main water circuit 30 is obtained in the following way: cold water returns from the heating system via the return line 31, passes through the condenser 14 and then through the boiler 20, thus obtaining hot water. After passing through the boiler 20, the hot water meets the three-way valve 33: the water can be sent either to the supply line 32 of the system via the first outlet 33b, or to the fourth heat exchanger 34, where domestic hot water is produced, via the second outlet 33c. The cold water leaving the fourth heat exchanger 34 passes through the tank 70, where it is again heated by the exchanger 16 and conducted to the boiler 20. A combined process for heating a main water circuit, according to the present invention, is described below. Such a process is advantageously implemented by a combined heating system 1 as described above.

The combined heating process comprises the step of carrying out a first heating of the water by means of heat exchange with a refrigerant fluid in a gaseous state. The heat exchange is such that the refrigerant fluid changes from a gaseous state to a liquid state.

The water is then heated for a second time by heat exchange with the combustion fumes. The combustion fumes are generated in the condensation boiler 20.

After carrying out the second heating of the water, the combustion fumes are extracted from the condensation boiler 20 and are taken to a first heat exchanger 12, or evaporator. Here, heat exchange with the liquid coolant takes place. In this way, the heat of the fumes allows the fluid to pass from the liquid to the gaseous state and it is possible to reuse the coolant for the stage of carrying out a first heating of the water.

In other words, energy is recovered from the combustion fumes in the process to heat the cooling fluid. In this way, the heat from the combustion fumes is reused within the process, with a major advantage in terms of efficiency.

Preferably, the step of delivering the combustion fumes to a first heat exchanger 12 occurs within a sealed chamber 50.

Preferably, after extracting the combustion fumes and before heat exchange with the cooling fluid, the combined heating process comprises a step of mixing the combustion fumes with ambient air. As a result, heat exchange occurs between a mixture of air and fumes and the cooling fluid.

Preferably, the process comprises a stage of evacuation of fumes into the atmosphere by means of forced ventilation.

Preferably, the process further comprises a step of accumulating water from the main circuit 30. The accumulated water is reheated by heat exchange with the cooling fluid. Specifically, the cooling fluid is in a gaseous state.

The accumulated and heated water then exchanges heat with a domestic hot water circuit to produce domestic hot water.

According to the description provided, the characteristics of the combined system and the process for heating a main water circuit according to the present invention are clear, as are its advantages.

In particular, by providing a duct that transports the combustion fumes from the boiler to the evaporator, a heat exchange between the flue gas (or the mixture of ambient air and flue gas) and the refrigerant fluid is enabled. It is therefore no longer necessary to include a special heat exchanger between the combustion fumes and an ambient air flow, nor to include a second flue-refrigerant fluid evaporator. The combined heating system is therefore structurally simpler and, by introducing "direct" heat exchange between the flue gas and the refrigerant fluid, the efficiency is increased compared to known solutions.

Claims (8)

1. A combined system for heating (1) a main water circuit (30) comprising a condensing boiler (20) and a heat pump (11, 12, 13, 14, 16), said boiler (20) having a combustion smoke outlet (23), said heat pump (11, 12, 13, 14, 16) comprising a refrigerant circuit (11) through which a refrigerant fluid flows and a first heat exchanger (12) crossed by said circuit (11) in which the refrigerant fluid receives heat passing from a liquid state to a gaseous state; said combined system comprising a duct (40) extending between the smoke outlet (23) of the boiler (20) and said first heat exchanger (12) to transport the smoke coming from the smoke outlet (23) to the first heat exchanger (12), wherein the condensing boiler (20) comprises a sealed chamber (50), which is a chamber isolated from a surrounding environment where combustion occurs, the air being sucked in from outside by means of a fan (43), so that the sealed chamber (50) is under depression, said smoke outlet (23) being inside the sealed chamber (50); characterized in that said duct (40) is inside the sealed chamber (50). 2. The combined heating system (1) according to claim 1, comprising a fan (43) associated with the first heat exchanger (12) such that the fumes exiting the duct (40) are sucked towards the first heat exchanger (12). 3. The combined heating system (1) according to any one of the preceding claims, comprising a drain (42) to the atmosphere for the flue gases downstream of said first heat exchanger (12). 4. The combined heating system (1) according to any one of the preceding claims, comprising: - a tank (70) for producing domestic hot water which can be placed along the main water circuit (30), said tank having an inlet (71) for the water to be heated and an outlet (72) for the hot water; - an additional heat exchanger (16) arranged inside the tank (70) and crossed by the refrigerant circuit (11) to exchange heat between the refrigerant fluid and the water of the main water circuit (30). 5. A combined process for heating a main water circuit (30) by means of the combined heating system (1) according to any of the preceding claims, comprising the steps of: - carrying out a first heating of the water by heat exchange with a refrigerant fluid in a gaseous state, said refrigerant fluid passing from the gaseous state to a liquid state; - carrying out a second heating of the water by heat exchange with the combustion fumes; after carrying out a second heating of the water, bringing the combustion fumes to the first heat exchanger (12), wherein the step of bringing the combustion fumes to the first heat exchanger (12) occurs within the sealed chamber (50); - exchanging heat in the first heat exchanger (12) between the combustion fumes and the cooling fluid in liquid state, said cooling fluid passing from the liquid state to the gaseous state to be used in the stage of carrying out a first heating of the water. 6. The combined heating process according to claim 5, wherein a wall defining the sealed chamber (50) acts as a seal for the fumes exiting the first heat exchanger (12). 7. The combined heating process according to any one of the preceding claims, comprising a step of mixing the combustion fumes with ambient air before the heat exchange step, said heat exchange step occurring between a mixture of air and fumes and the cooling fluid. 8. The combined heating process according to any one of claims 5 to 7, comprising the steps of: - accumulate water from the main water circuit (30); - heat the accumulated water by heat exchange with the cooling fluid; - exchange heat between the stored and heated water and a domestic hot water circuit to produce domestic hot water.