Heating device

Abstract

 The invention relates to a method of controlling the energy management of a heating device for heating a fluid, for example, a heat transport fluid for a central heating system or tap water, comprising a burner having a fuel dispensing member and a channel provided with a blower for the supply of combustion air and an outlet for combustion products, a heat exchanger arranged above the burner and adapted to pass the fluid and adjusting means for adjusting the effective flow rate of the blower. The method according to the invention is characterized in that a characteristic temperature and the fluid inlet temperature are measured and the flow rate of the fuel dispensed by the fuel dispensing member constructed in theform of adjustable fuel dosing member and the number of revolutions of the blower are adjusted in dependence on the measured temperatures.
The invention furthermore relates to a device for carrying out such a method.

Description

[0001] The invention relates to a method of controlling the energy management of a heating device for heating fluid, for example, a heat transport fluid for a central heating system or tap water, comprising a burner having a fuel dispensing member and a channel provided with a blower for the supply of combustion air and an outlet for combustion products, a heat exchanger arranged above the burner and adapted!.to pass the fluid and blower flow rate adjusting means for adjusting the effective flow rate of the blower as well as to a device for carrying said method into effect. Such a method and device are known from German patent application G 77 37 272 laid out for public inspection.

[0002] In accordance with the technology described in said D.A.S. the adaptation of the amount of air supplied per unit time to the burner or else the effective flow rate of the blower is performed by means of a controllable by-pass conduit, whose adjustment, that is to say, degree of activity is determined by the fuel flow rate once adjusted. The blower continously rotates with its maximum speed and the effective flow of combustion air depends on the extent to which the by-pass conduit short-circuits the blower.

[0003] This known technology exhibits drawbacks and limitations. In the first place the blower remains fully operative without interruption, which is undesirable with regard to an efficient use of energy and will, moreover, adversely affect the lifetime of the blower. Furthermore, control is performed entirely by mechanical agency, whilst there are no means to ensure that the effective flow of combustion air corresponds to an adjusted fuel rate to an extent such that combustion takes place with optimum efficiency. Finally, the above-mentioned German patent application doe snot disclose how the fuel rate has to be chosen or adjusted in order to attain a degree of efficiency which will be as high as possible in view of given variables.

[0004] The invention has for its object to eliminate said drawbacks and limitations of the known technology and provides to this end a method of the kind set forth, in which in accordance with the invention a characteristic temperature and the fluid inlet temperature are measured and the flow rate of the fuel dispensed by the fuel dispensing member constructed in the form of an adjustable fuel dosing member and the number of revolutions of the blower are adjusted in dependence on the measured temperatures, as well as a device for carrying said method which is characterized in that the characteristic temperature is the temperature of the open air.

[0005] Preference is given to that method according to the invention in which at the start for a first,.predetermined time interval a maximum blower rate is set and subsequently for a predetermined, second time interval a maximum fuel rate is set with sumultaneous ignition of the fuel, said time intervals terminating at the same instant.

[0006] The device according to the invention may comprise memory means for storing a predetermined relationship between, on the one hand, said characteristic temperature and the fluid inlet temperature and, on the other hand, the fuel rate and the blower rate and calculating means for calculating the desired fuel rate and blower rate on the basis of the measured characteristic temperature and fluid inlet temperature. In this case reading means are preferably provided for loading said relationship. Said reading means may serve for a single setting to be maintained for at least a long period, whilst nevertheless the user has the possibility of modifying the adjustment at any desired instant.

[0007] In order to minimize standstill losses said relationship may include the maximum value of the xternal temperature above which the fuel rate is reduced to zero.

[0008] In the abovementioned device disclosed in the German patent application G77 37 272 laid open for public inspection the blower is disposed upstream with respect to the burner. This means that the blower creates excess pressure in the burner space with respect to the ambience. In the event of leakage of the housing of the device noxious combustion products may escape into the space accomodating the device rather than being conducted away through the outlet. According to the invention the blower flow in a preferred embodiment is arranged downstream with respect to the burner place. In this case the blower produces subatmospheric pressure in the combustion space so that in the event of leakage air is conveyed from the ambience towards the combustion space, whilst noxious combustion products can leave the device only through the outlet.

[0009] Preferably, the temperature variations in the flue gas outlet channel are determined and these measured temperature variations are employed for fine control of the number of revolutions of the blower. It is thus ensured, that despite, for example, ageing, fouling or tolerances of the blower specimens a correct rate adjustment can always be obtained. Quite simple is the method in which the temperature variations are determined by measuring the temperature difference between two preselected positions in the outlet channel of the combustion products.

[0010] As an alternative, the concentration of a gas component in the outlet channel of combustion products which is characteristic of the degree of efficiency of the combustion process can be determined. For example, the gas component may be one of the group comprising carbon-dioxide, oxygen, carbon-monoxide.

[0011] In a preferred embodiment safety means are provided adapted for comparing the voltage applied to the blower with a preselected, maximum permissible voltage and for reducing the fuel rate to zero when said value is exceeded.

[0012] In an advantageous embodiment the memory means form part of a microprocessor.

[0013] Further features and particularities of the invention will be mentioned and explained with referecen to a drawing.

[0014] In the drawing show

Figure 1 an embodiment of a device in accordance with the invention,

Figure 2 a detail of a first variant of the device in accordance with the invention,

Figure 3 a detail corresponding to figure 2 of a second variant of the device in accordance with the invention.

[0015] The device shown in figure 1 comprises a housing 1, which is completely closed with the exception of a connection with a tubing 2, inside which a second tubing 3 is arranqed whilst leaving free an inlet channel 4 for fresh air. The inner or second tubing 3 bounds an outlet channel 5 for combustion products, for example, flue gases. The outlet channel 5 communicates with a dome 6 arranged inside the housing 1 and accommodating a burner 7 and a heat exchanger 8. The heat exchanger comprises a plurality of metal laminations 9 in the form of a toppled-over V. By this shape and orientation it is ensured that the stream of the hot gases produced by the operation of the burner transfers its heat at an optimum to the laminations. The laminations 9 are thermally coupled with a fluid conduit 10 having an inlet stub 11 projecting out of the housing and an outlet stub 12. The conduit 10 may form part of a central heating circuit or of a duct for hot tap water, the inlet stub 11 being connected in the latter case with the water mains. Out of the housing 1 furthermore protrudes a fuel inlet stub 13. Through a controllable valve 14 fuel, for example, gas is fed through said stub 13 to the burner 7. Near the burner apertures 4 this embodiment comprises a spark ignition member 15.

[0016] Theoutlet channel 5 comprises a blower 16, which rotates in a sense such that an outwardly directed stream is produced . In this embodiment the inlet/outlet tubing 3,2 extends across an outer wall 17. The outlet tubing 3 is prolonged beyond the inlet tubing 2 in order to prevent combustion products from being sucked in.

[0017] The controllable valve 14, the spark ignition member 15 and the blower 16 are all electrically actuated from a memory calculating unit 18. The latter has a plurality of inputs connected to (a) a write unit 19, (b) an output terminal of the blower 16 at which a signal representative of the number of revolutions is available, (c) a sensor 21 on the stub 11 for measuring the inlet temperature of the fluid, (d) a temperature sensor 20a,20b for determining a characteristic temperature. When the present device is employed for central heating purposes, the temperature sensor 20a shown in the figure is used as an external temperature sensor. If the present device serves for hot tap water purposes a temperature sensor 20b thermally coupled with the outlet stub 12 is used. Consequently, either the sensor 20a or the sensor 20b is employed in accordance with the specific function of the device. Therefore, the signal conductors of the sensors 20a and 20b are indicated by broken lines.

[0018] In the unit 18 is stored by means of the write unit 19 a relationship between, on the one hand, the temperature measured by the sensor 20a or 20b and the fluid inlet temperature measured by the sensor 21 and, on the other hand, the setting of the valve 14 (fuel rate) and the number of revolutions of the blower 16(blower rate).

[0019] In the present embodiment the unit 18 comprises, in addition, a comparator for comparing the desired number of revolutions with the calculated, desired number of revolutions and control means connected to the output of the comparator for the blower 16. It is thus ensured that the measured rate of the blower is invariably at least substantially equal to the calculated, desired rate.

[0020] When the device according to the invention is employed as a central heating boiler, the write unit 19 can be used for an optional adjustment of the firing curve.

[0021] It appears that the device according to the invention described above attains an excellent degree of efficiency since invariably optimum use is made of a thermodynamically desirable relationship between the aforesaid input quantities and output quantities.

[0022] It will be obvious that the device according to the invention may be constructed so that it is suitable for simultaneously heating tap water and heat transport water of a central heating system. In this case the device comprises two separate heat exchangers, whilst a temperature sensor at the outlet stub 12 and an external temperature sensor are employed. Useless to note that at any instant only one of these temperature sensors may serve for indicating a temperature typical for the control. There may be provided a priority switch by which, when tap water is taken, the function of the external temperature sensor is taken over by the fluid outlet temperature sensor.

[0023] In figures 2 and 3 elements corresponding with those of figure 1 are designated by the same reference numerals. A further description thereof is omitted.

[0024] The device shown in figure 2 comprises a carrier plate 22 arranged in the outlet channel 5, on which two temperature sensing members 23 and 24 are arranged at a preselected, axial distance from one another. The outputs of these temperature sensing members are connected to the memory calculating unit 18. By determining the temperature difference between the sensors 23 and 24 and by adjusting the blower rate in accordance herewith a fine control is obtained as compared with the coarse control described above.

[0025] Figure 3 shows a further embodiment of the device in which a fine control of a different kind is used. The device shown in figure 3 comprises a sensor 25 arranged in the outlet channel 5, which sensor is sensitive to a gas component representative of the efficiency of the combustion process. The output of the sensor 25 is connected to the memory calculating unit 18.

[0026] The invention is not limited to the embodiments described in the foregoing. Various modifications of components and their relationship may be applied without going beyond the scope of the invention.

[0027] For example, combinations of the principles of the invention as described are possible whilst the leading idea thereof is maintained. Temperature sensors arranged in the outlet may be used in conjunction with a sensor for a desired gas component.

[0028] There may furthermore be provided safety means for comparing the voltage applied to the blower with a predetermined, maximum permissible voltage, the fuel rate being reduced to zero when said value is exceeded.

Claims

1. A method of controlling the energy management of a heating device for heating a fluid,. for example, a heat transport fluid for a central heating system or tap water, comprising a burner having a fuel dispensing member and a channel provided with a blower for the supply of combustion air and an outlet for combustion products, a heat exchanger arranged above the burner and adapted to pass the fluid and blower flow rate adjusting means for adjusting the effective flow rate of the blower characterized in that a characteristic temperature and the fluid inlet temperature are measured and the flow rate of fuel dispensed by the fuel dispensing member constructed in the form of a fuel dosing member and the number of revolutions of the blower are adjusted in dependence on the measured temperatures.

2. A method as claimed in claim 1 characterized in that the characteristic temperature is the fluid outlet temperature.

3. A method as claimed in claim 1 wherein the fluid is the heat transport fluid for a central heating system, characterized in that the characteristic temperature is the temperature of the open air.

4.A method as claimed in anyone of claims 1 to 3 characterized in that at the start first for a preselected first time interval a maximum blower rate is set and subsequently for a preselected, second time interval a maximum fuel rate is set with simultaneous ignition of the fuel, said time intervals terminating at the same instant.

5. A method as claimed in anyone of the preceding claims characterized in that the temperature variations in the outlet channel for combustion products are determined and employed for the fine control of the number of revolutions of the blower.

6. A method as claimed in claim 5 characterized in that the temperature variations are determined by measuring the temperature difference between two preselected axially spaced positions in the outlet channel for combustion products.

7. A method as claimed in anyone of claims 1 to 4 characterized in that the concentration of a gas component representative for the efficiency of the combustion process is determined in the outlet channel for combustion products and is employed for the fine control of the number of revolutions of the blower.

8. A method as claimed in claim 7 characterized in that said gas constituent is one of the group comprising carbon-dioxide, oxygen, carbon-monoxide.

9. A heating device for carrying out the method claimed in anyone of the preceding claims for heating a fluid, for example, a heat transport fluid for a central heating system or tap water, comprising a burner having a fuel dosing member and a channel provided with a blower for the supply of combustion air and an outlet for combustion products, a heat exchanger arranged above the burner and adapted to pass the fluid, adjusting means for adjusting the effective flow rate produced by the blower, characterized by:

1. a member for measuring said characteristic temperature,

2. a member for measuring the fluid inlet temperature and

3. adjusting means coupled with the two temperature measuring members for adjusting the flow rate of the fuel dispensed by the fuel dosing member, the blower rate adjusting means being adapted to adjust the number of revolutions of the blower in dependence on the measured characteristic temperature and the measured fluid inlet temperature.

10. A device as claimed in claim 9 characterized by memory means for storing a predetermined relationship between , on the one hand, said characteristic temperature and the fluid inlet temperature and, on the other hand, the fuel rate and the blower, rate and by calculating means for calculating a desired fuel rate and blower rate on the basis of the measured characteristic temperature and the fluid inlet temperature.

11. A device as claimed in claim 10 characterized by write means for loading said relationship.

12. A device as claimed in claim 10 or 11 characterized in that said relationship includes a maximum value of the external temperature, above which the fuel rate is reduced to-zero.

13. A device as claimed in anyone of claims 9 to 12 characterized in that the blower is arranged downstream of the combustion area.

14. A device as claimed in anyone of claims 9 to 13 characterized in that the memory means form part of a microprocessor.

15. A device as claimed in anyone of claims 9 to 14 characterized by measuring means for measuring the number of revolutions of the blower, comparing means for comparing the measured number of revolutions with the calculated, desired number of revolutions and control means for the blower connected to the output of the comparing means in a manner such that the measured number of revolutions of the blower is always substantially equal to a calculated desired number of revolutions.

16. A device for carrying out the method claimed in claim 6 characterized by two temperature -sensing members arranged at a preselected axial distance from one another in the outlet channel for combustion products, the output signals of said members being applied to the blower rate adjusting means.

17. A device for carrying out the method claimed in claims 7 or 8 characterized by a sensor arranged in the outlet channel for combustion products which is sensitive to a gas component representative of the efficiency of the combustion process, the output signals of said sensor being applied to the blower rate adjusting means.

18. A device as claimed in claim 17 characterized in that the sensor comprises a zirconium element.

Drawing