The invention relates to a domestic water heating unit for mobile applications, with a domestic water storage unit. The invention further relates to a method for heating domestic water for mobile applications.
Domestic water is currently heated in motor homes using primarily electricity or gas as the energy source. For stationary operation, electricity represents a convenient, rapid and safe heating option. However, electricity is ordinarily available only at corresponding hook-up sources at specially designated parking spaces and is relatively expensive. Operating the current-fed domestic water heating system using the on-board network (usually 12-volt systems) offers an insufficient buffer over longer distances and does not appear to be very economical.
Gas is relatively widely used as an energy source for heating domestic water. Disadvantages that have been identified in association with this include the availability of gas, which is not always ensured, and the danger of fire or explosion with improper use and/or improper maintenance. Furthermore, the gas supply tanks require significant storage space and decrease potential loading capacity of the motor home.
Also known is the process of using exhaust heat from the combustion engine of the motor home to heat the domestic water. With the fuel-efficient engines in use today, however, the amount of exhaust heat generated that could be used to heat the domestic water is small. Accordingly, an additional, auxiliary heat source must be provided with which the domestic water can be heated to the desired temperature.
Additionally, a domestic water heating unit for mobile applications is known, which employs a heating device to use heated air to heat the domestic water. In this process, the heated air that is already made available to the vehicle is also used to heat the domestic water. One disadvantage of this is that using heated air exclusively to heat the domestic water involves using a medium having a relatively low specific heat capacity. This can adversely affect the efficiency or the dimensions of the domestic water heating device.
The object of the invention is to further improve upon this type of domestic water heating device such that it will ensure a heating of the domestic water in a simple and efficient manner, independently of the energy sources gas and electricity.
This object is attained with the characterizing features described in the independent claims.
Advantageous further improvements and embodiments of the invention are described in the dependent claims.
The domestic water heating unit of the invention builds upon the generic prior art in that the domestic water heating unit has a fluid/domestic water heat exchanger, wherein thermal energy can be supplied to the fluid via an auxiliary heating device, and the thermal energy of the fluid can be transferred at least partially to the domestic water via the heat exchanger. In this, already existing components such as an auxiliary heating device or a fluid that has already been used can advantageously be relied upon. By using a fluid as the heat transfer medium to heat the domestic water, especially a heat transfer medium having a high specific heat capacity can be used. Furthermore, the domestic water heating unit of the invention offers the advantage that the fluid can be brought to any temperature within a selected range by means of the auxiliary heating device, thus a potentially desired heating level can also be achieved for the domestic water. At the same time, the fluid, as a heat transfer medium, can absorb any potentially existing exhaust heat from the engine of the motor home and use it to heat the domestic water. With the proper structural configuration of the fluid/domestic water heat exchanger, the domestic water and the fluid can be channeled separately, in the interest of food safety. For example, the fluid/domestic water heat exchanger can be configured as a countercurrent heat exchanger, in order to generate an efficient heat transfer. Other configurations are also conceivable, however, such as a heat exchanger according to the continuous-flow heater principle, in which the domestic water is channeled under thermal contact with the fluid within the same, or a heat exchanger, in which the fluid, channeled within the domestic water, releases thermal energy to it.
In a preferred embodiment it is provided that the fluid forms a heat transfer medium in a closed heat transfer circuit. The heat transfer circuit can, for example, be a coolant circuit in a motor home. In this manner, the domestic water heating unit can be integrated into an already existing circuit. The closed heat transfer circuit can be heated independently of the domestic water energy requirement using the auxiliary heating device, and can be used supplementarily or exclusively to heat the domestic water via the fluid/domestic water heat exchanger. The closed configuration of the circuit enables a material separation of fluid and domestic water with simultaneous thermal contact.
Especially in one embodiment it can be provided that the heat transfer circuit has solenoid valves. With the solenoid valves, a control of the heat transfer from the fluid to the domestic water can be achieved. For example, with a high domestic water energy requirement, the flow of fluid through the fluid/domestic water heat exchanger can be increased, while other energy consumers in the heat transfer circuit also receive a lower fluid flow or, optionally, can be completely removed from the circuit. Alternatively, the fluid/domestic water heat exchanger could be completely removed from the heat transfer circuit via correspondingly switched valves, if no additional domestic water heating is desired.
In a similarly preferred embodiment of the invention, the auxiliary heating device is run on a liquid fuel. Especially if the same type of fuel is used with which the motor home is operated, this enables a simple supply of the corresponding fuel to the auxiliary heating device. For example, the fuel can be taken directly from the fuel tank of the motor home, allowing a simple supply of the auxiliary heating device, and thereby of the domestic water heating device, to be achieved in stationary operation and during driving of the motor home.
A preferred embodiment of the domestic water heating device of the invention provides that the heat exchanger is arranged inside the domestic water storage unit. This arrangement facilitates placing a relatively large surface of the heat exchanger in contact with the domestic water. For example, the domestic water is able to flow directly around areas and/or surfaces of the heat exchanger. Optionally, parts of the heat exchanger can project directly into the domestic water, thereby enabling an effective transfer of heat.
In this connection, it can advantageously be further provided that the heat exchanger forms a piping section of the heat transfer circuit. This represents a simple and efficient embodiment of a heat exchanger. The piping section can, for example, dip directly into the domestic water storage unit and heat the domestic water via the heat transfer fluid flowing through it.
Especially, it can advantageously be provided that the piping section is helical in shape. The helical embodiment expands the surface of the heat exchanger available for releasing thermal energy, thereby improving the thermal contact between the heat transfer fluid and the domestic water.
Furthermore, in a preferred further improvement on the invention it can be provided that the domestic water storage unit is insulated. This ensures a supply of hot domestic water for a longer period of time after the domestic water heating unit is switched off.
With a preferred further improvement on the invention it is provided that the domestic water storage unit has a cylindrical tank. This type of shape enables cost-effective production due to a small number of weld seams.
The invention further relates to a method for heating domestic water for mobile applications, which comprises the following steps:
In this manner the advantages of the invention are also realized within the framework of a process.
The invention is based upon the idea of using an auxiliary heating device that is already present in a motor home, for example an engine-independent air heating system, to heat domestic water. In this, according to the invention, a coolant/domestic water heat exchanger is integrated into the coolant circuit connected to the auxiliary heating device. The heat exchanger can be configured, for example, as a spiral or helical piping section that projects into the domestic water tank. The amount of energy released to the domestic water can be controlled, for example, via solenoid valves, which supply the heating power from the engine-independent air heating system to heat the domestic water, to heat the vehicle interior, or both.
In what follows, the invention will be described in greater detail by way of example with reference to the appended set of drawings of preferred embodiments.
The drawings show:
The integration of the heat exchanger 14 and the domestic water tank 12 in a coolant circuit, according to the invention, is shown in
Via the heat exchanger intake 68, the heated coolant 16 flows through the piping section 28 into the interior of the domestic water tank 12. Along the path from the heat exchanger intake 68 to the heat exchanger outlet 70, the coolant 16 flows through the helix 30. The helix 30 is completely surrounded by domestic water 20, which is thus in close thermal contact with the coolant 16 via the wall of the pipe of the helix 30. This allows the coolant to release a portion of its thermal energy to the domestic water 20. The U-shaped and/or helical arrangement of the piping section 28 inside the domestic water tank 12 permits an even heating of the domestic water 20. This results in a temperature gradient in the domestic water: Those parts of the domestic water 20 in the area of the domestic water outlet 62 have a higher temperature than those parts that are in the lower area of the domestic water tank 12 in the vicinity of the domestic water intake 60. Thus heated domestic water 20 can be drawn via the domestic water outlet 62, while at the same time cold water is supplied to the domestic water tank 12 via the domestic water intake 62 [sic].
The illustrated arrangement can be operated especially in two modes: In a first operating mode the coolant 16 circulates between the elements of engine-independent air heating system 18, fluid/domestic water heat exchanger 14, fluid/air heat exchanger 40 and combustion engine 46. In this, the engine-independent air heating system 18 draws the fuel 26 from the fuel tank 48 via the pipeline 80, burns the fuel 26 and thereby heats the coolant 16. The coolant flows via the pipeline 50 to the fluid/domestic water heat exchanger 14, where it transfers a portion of its thermal energy to the domestic water 20 held in the domestic water tank 12, as described in reference to
The above-described coolant circuit is intended only to illustrate the concept of the invention. Of course, significantly more complicated circuits, for example having a greater number of solenoid valves, are also conceivable, in which, for example, each heat source and/or each individual thermal energy consumer can be added to or removed from the circuit. This type of circuit can also contain a larger or smaller number of thermal energy consumers.
The characterizing features of the invention disclosed in the above description, in the set of drawings, and in the claims can be considered essential, alone or in any combination, to implementation of the invention.
Number | Date | Country | Kind |
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102005007086.8 | Feb 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE2006/000274 | 2/15/2006 | WO | 00 | 10/22/2007 |