BURNER ASSEMBLY FOR A DOMESTIC FIREPLACE

Abstract

The present invention relates to a burner assembly for a domestic fireplace, configured to burn a mixture of a first combustible fuel and a second combustible fuel, comprising a combustible long chain hydrocarbon fuel, the assembly comprising at least one burner and a mixing device, the mixing device comprising: a housing, defining a mixing interior, at least one discharge opening in the housing, connected to the at least one burner and configured to provide access from the mixing interior towards the burner, a first fuel supply, projecting into the mixing interior and configured to supply the first fuel into the mixing interior, and a second fuel supply, projecting into the mixing interior and configured to supply the second fuel into the mixing interior, characterized in that, the mixing device further comprises: a heating element, e.g. a second heating element, arranged at least partially in the mixing interior and configured to heat the second fuel to a mixing temperature, wherein the mixing device is configured to mix the first fuel with the heated second fuel to form the fuel mixture, and wherein the at least one burner is configured to combust the fuel mixture.

Claims

1. A burner assembly for a domestic fireplace comprising: at least one burner; and a mixing device comprising: a housing, defining a mixing interior; at least one discharge opening in the housing, connected to the at least one burner and configured to provide access from the mixing interior towards the at least one burner; a first fuel supply, projecting into the mixing interior and configured to supply a first fuel into the mixing interior; a second fuel supply, projecting into the mixing interior and configured to supply a second fuel comprising a combustible long chain hydrocarbon fuel into the mixing interior; and a second heating element, arranged at least partially in the mixing interior and configured to heat the second fuel to a mixing temperature; wherein the mixing device is configured to mix the first fuel with the heated second fuel to form a fuel mixture; and wherein the at least one burner is configured to combust the fuel mixture.

2. The burner assembly according to claim 1, wherein at least one of: the first fuel is in a liquid state at room temperature; or the second fuel is in a solid state at room temperature.

3. The burner assembly according to claim 1, wherein the first fuel supply is further configured to supply the first fuel to the mixing device in a gaseous state.

4. The burner assembly according to claim 1, wherein the mixing device further comprises: an air supply, projecting into the mixing interior and configured to supply a flow of air into the housing to provide a flow of air through the mixing interior along a flow path.

5. The burner assembly according to claim 4, wherein the first fuel supply is further configured to supply the first fuel to the mixing device in a gaseous state; and wherein the air supply forms part of the first fuel supply, and is configured to supply a gas mixture to the mixing device, which gas mixture comprises the flow of air and the gaseous first fuel.

6. The burner assembly according to claim 1, wherein the mixing device further comprises: a first heating element; wherein the first fuel supply is further configured to supply the first fuel to the mixing device in a liquid state; and wherein the first heating element is arranged at least partially in the mixing interior and is configured to heat the first fuel to a vaporizing temperature to vaporize the first fuel inside the mixing interior.

7. The burner assembly according to claim 6, wherein the first heating element is a resistive heating element, projecting at least partially into the mixing interior.

8. The burner assembly according to claim 7, wherein the mixing device further comprises: a first temperature sensor located in the mixing interior, configured to emit a first temperature sensor signal representative for the temperature inside the mixing interior; and a control unit, configured to control the first heating element on the basis of the first temperature sensor signal to set the vaporizing temperature.

9. The burner assembly according to claim 8, wherein the first temperature sensor is a thermocouple.

10. The burner assembly according to claim 1, wherein the mixing device further comprises: a second temperature sensor located in the mixing interior, configured to emit a second temperature sensor signal representative for the temperature inside the mixing interior; and a control unit, configured to control the second heating element on the basis of the second temperature sensor signal to set the mixing temperature.

11. The burner assembly according to claim 10, wherein the second temperature sensor is a thermocouple.

12. The burner assembly according to claim 10, wherein the second heating element is a resistive heating element or a radiant heating element projecting at least partially into the mixing interior.

13. The burner assembly according to claim 1, wherein the mixing device further comprises: a plurality of obstructions, which are located in the mixing interior and configured to promote mixing of the fuel mixture.

14. The burner assembly according claim 1, wherein the mixing interior comprises a first interior section and a second interior section; wherein the first fuel supply projects into the first interior section; and wherein the second fuel supply projects into the second interior section.

15. The burner assembly according to claim 14, wherein the mixing device further comprises: a first heating element; wherein the first fuel supply is further configured to supply the first fuel to the mixing device in a liquid state; wherein the first heating element arranged at least partially in the mixing interior and configured to heat the first fuel to a vaporizing temperature to vaporize the first fuel inside the mixing interior; and wherein at least one of the first heating element or the first temperature sensor is arranged at least partially in the first interior section.

16. The burner assembly according to claim 14, wherein at least one of the second heating element or the second temperature sensor is arranged at least partially in the second interior section.

17. The burner assembly according to claim 14, wherein the housing comprises: a first chamber, of which an interior forms the first interior section; and a second chamber, separate from the first chamber, of which an interior forms the second interior section; and wherein the first chamber and the second chamber are fluidly connected in series along a flow path.

18. The burner assembly according to claim 17, wherein the first chamber is an elongate first chamber comprising a first end and an opposed second end; wherein the flow path through the first chamber extends between its first end and its second end; wherein the second chamber is an elongate second chamber comprising a first end and an opposed second end; wherein the flow path through the second chamber extends from its first end to its second end; and wherein the first chamber and the second chamber are arranged next to each other, so that the flow path through the first chamber is parallel or anti-parallel to the flow path through the second chamber.

19. The burner assembly according to claim 18, wherein the first end of the first chamber is located adjacent to the first end of the second chamber; wherein the second end of the first chamber is located adjacent to the second end of the second chamber; and wherein the flow path through the first chamber extends from its second end to its first end, so that the flow path through the first chamber is substantially anti-parallel to the flow path through the second chamber.

20. The burner assembly according to claim 19, wherein the second chamber comprises a head section at its first end, which is substantially separated from the second interior section by a transverse wall; wherein the first chamber projects into the head section of the second chamber; wherein the transverse wall comprises a plurality of apertures that provide a fluid connection between the head section and the second interior section; and wherein at least one of the second heating element or the second temperature sensor extends into the second interior section through the head section and one of the apertures in the transverse wall.

21. The burner assembly according to claim 18, wherein the first fuel supply and the first heating element project into the first chamber at the first end thereof; wherein the second fuel supply and the second heating element project into the second chamber at the first end thereof; and wherein the at least one discharge opening is provided at the second end of the second chamber.

22. The burner assembly according to claim 18, wherein the mixing device further comprises: an air supply, projecting into the mixing interior and configured to supply a flow of air into the housing to provide a flow of air through the mixing interior along a flow path; and wherein the air supply projects into the first chamber at the second end thereof and is further configured to provide the flow of air along the flow path through the first chamber and the second chamber.

23. The burner assembly according to claim 1, wherein the housing is made of a ceramic material.

24. The burner assembly according to claim 1, wherein the at least one burner has an outer shape that corresponds to the outer shape of a wooden log.

25. A mixing device of a burner assembly comprising: a housing, defining a mixing interior; at least one discharge opening in the housing, configured to be connected to at least one burner of the burner assembly and configured to provide access from the mixing interior towards the at least one burner; a first fuel supply, projecting into the mixing interior and configured to supply a first fuel into the mixing interior; a second fuel supply, projecting into the mixing interior and configured to supply a second fuel comprising a combustible long chain hydrocarbon fuel into the mixing interior; and a second heating element, arranged at least partially in the mixing interior and configured to heat the second fuel to a mixing temperature; wherein the mixing device is configured to mix the first fuel with the heated second fuel to form a fuel mixture; and wherein the fuel mixture is configured to be combustible by the at least one burner.

26. A hybrid domestic fireplace comprising: the burner assembly according to claim 1; a combustion chamber, in which the at least one burner is accommodated; and a flue gas discharge, configured to discharge flue gasses out of the combustion chamber.

27. A method of creating a fire by means of a burner assembly comprising: supplying a first combustible fuel to a mixing interior of a mixing device of the burner assembly; supplying a second combustible fuel, comprising a second combustible long chain hydrocarbon fuel, to the mixing interior; heating, inside the mixing interior, the second fuel to a mixing temperature; mixing, in the mixing device, the first fuel with the heated second fuel to form a fuel mixture; and combusting the fuel mixture with a burner of the burner assembly to create the fire.

28. The method according to claim 27 further comprising: heating, inside the mixing interior, the first fuel to a vaporizing temperature to vaporize the first fuel inside the mixing interior.

29. The method according to claim 28 further comprising: measuring, with a first temperature sensor located in the mixing interior, the temperature inside the mixing interior; and controlling, with a control unit, the heating of the first fuel on the basis of the measured temperature to set the vaporizing temperature.

30. The method according to claim 27 further comprising: measuring, with a second temperature sensor located in the mixing interior, the temperature inside the mixing interior; and controlling, with a control unit, the heating of the second fuel on the basis of the measured temperature to set the mixing temperature.

31. The method according to claim 27, wherein the first fuel comprises an alcohol and is in a liquid state at room temperature.

32. The method according to claim 27, wherein the second fuel comprises a wax and is in a solid state at room temperature.

33. The method according to claim 27, wherein the second fuel comprises an oil and is in a liquid state at room temperature.

34. The method according to claim 27 further comprising: preheating the burner according to a preheating cycle to a predetermined preheating temperature, the preheating cycle comprising: supplying the first combustible fuel to the burner, via the mixing device; combusting the first fuel with the burner of the fireplace to create the fire; and heating the burner by means of the fire; whereupon, when a temperature of the burner exceeds the predetermined preheating temperature, the preheating cycle is terminated and the second combustible fuel is supplied to the mixing device and mixed with the first fuel.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0202] Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:

[0203] FIG. 1 schematically depicts a mixing device of an embodiment of the burner assembly according to the present invention,

[0204] FIG. 2 schematically depicts a cross-section of the mixing device of FIG. 1,

[0205] FIG. 3 schematically depicts the mixing device of FIG. 1 in an exploded-view representation,

[0206] FIG. 4 depicts the entire burner assembly according to the embodiment of FIG. 1,

[0207] FIG. 5 schematically depicts a cross-section of an alternative mixing device, and

[0208] FIG. 6 schematically depicts the mixing device of FIG. 5 in an exploded-view representation.

[0209] Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

DETAILED DESCRIPTION OF EMBODIMENTS

[0210] FIG. 1 schematically depicts a mixing device of an embodiment of the burner assembly according to the present invention, to which is referred with reference numeral 10. The mixing device 10 is configured to mix a first fuel F1 and a second fuel F2 to form a fuel mixture. The mixing device 10 comprises a housing 103, which is made of a low thermal expansion coefficient ceramic material. The ceramic material is able to resist the temperatures that may occur in the mixing device 10, in particular during the heating the first fuel F1 and/or the second fuel F2.

[0211] The first fuel F1 is in a liquid state at room temperature, comprising an alcohol. In particular, the first fuel F1 is a mixture comprising a spirit, which contains ethanol with about 15 wt % water in it.

[0212] The second fuel F2 is in a solid state at room temperature, comprising a wax. In particular, the second fuel F2 contains paraffin or stearin.

[0213] Furthermore, burner assembly comprises a burner 40, as is best shown in FIG. 4, which has a shape that corresponds to the outer shape of a wooden log. The burner 40 is fluidly connected to a discharge opening 42 of the mixing device 10 by means of a burner channel 41 to guide a flow of the fuel mixture from the mixing device 10 towards the burner 40. The burner 40 is, in turn, configured to combust the fuel mixture, so that flames are visible at the outer surface thereof, i.e. of the log.

[0214] The mixing device 10 is configured to heat the first fuel F1 by means of a first heating element 11, which is embodied as an infrared heating element. The mixing device 10 is configured to heat the first fuel F1 to a vaporizing temperature to vaporize the first fuel F1 in the mixing device 10. In the present embodiment, the vaporizing temperature is set at 90? C. To obtain this temperature, the first heating element 11 itself is controlled to reach a temperature of 250? C.

[0215] The mixing device 10 comprises a first temperature sensor 13, which is arranged adjacent the first heating element 11. The first temperature sensor 13 is configured to emit a first temperature sensor signal representing the temperature at which the first fuel F1 is heated, e.g. representing the temperature of the first heating element 11.

[0216] The mixing device 10 is further configured to heat the second fuel F2 by means of a second heating element 12, which is, in the embodiment shown in FIGS. 1-4 embodied as a resistive heating element. The mixing device 10 is configured to heat the second fuel F2 to a mixing temperature to heat the second fuel F2 in the mixing device 10, to vaporize and/or to nebulize the second fuel F2. In the embodiment shown in FIGS. 1-4, the mixing temperature is set at 300? C. To obtain this temperature, the second heating element 12 itself is controlled to reach a temperature of 600? C.

[0217] The mixing device 10 further comprises a second temperature sensor 14, which is arranged adjacent the second heating element 12. The second temperature sensor 14 is configured to emit a second temperature sensor signal representing the temperature at which the second fuel F2 is heated, e.g. representing the temperature of the second heating element 12.

[0218] The burner assembly further comprises a control unit (not visible in the figures), which is embodied as a proportional-integral-derivative (PID) controller and which is configured to control the mixing device 10 and to operate in a feedback manner. The control unit is electrically connected to the first heating element 11 and to the second heating element 12, for providing electricity towards the respective heating elements 11, 12, and is electrically connected to the first temperature sensor 13 and to the second temperature sensor 14, for transmitting the sensor signals from the respective temperature sensors 13, 14 to the control unit.

[0219] The control unit is configured to control the first heating element 11 on the basis of the first temperature sensor signal, in order to set the vaporizing temperature, and is configured to control the second heating element 12 on the basis of the second temperature sensor signal, in order to set the mixing temperature.

[0220] The mixing device 10 comprises a first fuel supply, which is configured to feed the first fuel F1 into the mixing device 10. The first fuel supply comprises a first fuel line that projects into the mixing device 10 indirectly, by means of a first nozzle 27.

[0221] The mixing device 10 further comprises a second fuel supply, which is configured to feed the second fuel F2 into the mixing device 10. The second fuel supply comprises a second fuel line that projects into the mixing device 10 indirectly, by means of a second nozzle 37.

[0222] FIG. 2 shows a cross-sectional view on the mixing device 10 of FIG. 1, seen from the top in a vertically downward direction. It is shown in FIG. 2 that the mixing device 10 comprises a first chamber 15 and a second chamber 16, which respectively form a first interior section and a second interior section 16a. The first chamber 15 and the second chamber 16 are substantially physically separated from each other by an intermediate wall 104 of the housing 103, only being connected by a fluid connection in between them, which is embodied as an opening 19 between the chambers 15,16.

[0223] The first chamber 15 is substantially elongate along a longitudinal direction L and comprises a first end 151 and a second end 152. A flow path in the first chamber 15, indicated by means of arrows, extends from the second end 152 to the first end 151.

[0224] Similarly, the second chamber 16 is elongate along the longitudinal direction L as well, extending parallel to the first chamber 15, and also comprises a first end 161 and a second end 162. A flow path in the second chamber 16, indicated by means of arrows, extends from the first end 161 to the second end 161.

[0225] The first end 151 of the first chamber 15 is located adjacent to the first end 161 of the second chamber 16. The second end 152 of the first chamber 15 is located adjacent to the second end 162 of the second chamber 16, so that the flow path through the first chamber 15 is substantially anti-parallel, i.e. in opposite direction, to the flow path through the second chamber 16. The overall flow path through the mixing device 10 is thus from the second end 152 of the first chamber 15 to the first end 151 of the first chamber 15, to the first end 161 of the second chamber 16, e.g. via the opening 19, and eventually to the second end 162 of the second chamber 16, where the discharge opening 42 provided to guide the flow towards the burner 40.

[0226] Both the first chamber 15 and the second chamber 16 have a circular cross-section, seen in a plane perpendicular to the longitudinal direction L, and each have a diameter in this plane that is substantially equal to each other. Furthermore, the length of the first chamber 15, i.e. parallel to the longitudinal direction L, is substantially the same as the length of the second chamber 16.

[0227] Furthermore, the second chamber 16 comprises a head section 17 at its first end 161, which is substantially separated from a remainder of the second chamber 16, e.g. of the second interior section 16a, by a transverse wall 18. Seen along the flow path, the head section 17 is provided in between the first chamber 15 and the second interior section 16a of the second chamber 16. The first chamber 15 thereby projects into the head section 17, e.g. via the opening 19, so that a flow from the first chamber 15 first enters the head section 17, before entering the second interior section 16a.

[0228] The transverse wall 18 in the second chamber 16 is provided in a plane perpendicular to the longitudinal direction L, so that it extends over substantially the entire cross-section of the second chamber 16. The transverse wall 18 comprises multiple apertures 19, as is best shown in FIG. 3, which are spread over the entire cross-section of the second chamber 16, to allow for the passage of a flow from the head section 17 into the second interior section 16a. The spread apertures 19 have the benefit that the entrance of the flow, e.g. comprising the first fuel F1, into the second interior section 16a is spread over multiple locations, i.e. multiple apertures 19, instead of only at a single location, to provide for improved dispersion of the first fuel F1 amongst the second fuel F2.

[0229] The mixing device 10 further comprises a plurality of obstructions, not visible in the figures, which are located in the second chamber 16, e.g. in the second interior section 16a thereof, and which are configured to promote mixing of the flow entering from the head section 17, e.g. to promote mixing of the first fuel F1 and the second fuel F2.

[0230] The first nozzle 27 projects into the first chamber 15 and the second nozzle 37 projects into the second chamber 16. The first fuel F1 is thus supplied into the first chamber 15 and the second fuel F2 is supplied in the second chamber 16.

[0231] The first nozzle 27 enters the first chamber 15 at the first end 151, but extends through the first chamber 15 along the longitudinal direction L over a substantial part, e.g. approximately two thirds of the length of the first chamber 15. As such, the first fuel F1 is configured to be supplied into the first chamber 15 from multiple discharge openings 28 of the first nozzle 27, spread over part of the length of the first chamber 15.

[0232] The second nozzle 37 enters the second chamber 16 at the first end 161 and extends through the entire head section 17. The second nozzle 37 is not configured to supply the second fuel F2 in the head section 17 and is, to this end, free of openings in the head section 17. The second nozzle 37 further extends through one of the apertures 19 in the transverse wall 18, to project into the second interior section 16a of the second chamber 16. The second nozzle 37 extends along the longitudinal direction L over a substantial part, e.g. approximately three quarters of the length of the second interior section 16a of the second chamber 16. As such, the second fuel F2 is configured to be supplied into the second chamber 16 from multiple discharge openings 38 of the second nozzle 37, spread over part of the length of the second chamber 16.

[0233] The first heating element 11 is embodied as a resistive heating element, which projects into the first chamber 15 at the first end 151 as well and comprises a thermocouple 13 as first temperature sensor. The first heating element 11 also extends through the first chamber 15 along the longitudinal direction L over a substantial part, e.g. approximately two thirds of the length of the first chamber 15, similar as the first nozzle 27. As such, the first fuel F1 is configured to be heated over part of the length of the first chamber 15, to improve the heating of the first fuel F1.

[0234] In the present embodiments, the first thermocouple 13 is integrated in the first heating element 11, in order to provide for a first temperature sensor signal representative for the actual temperature inside the first heating element 11, without being disturbed by possible temperature variations at an outer surface of the first heating element 11 with the first fuel F1.

[0235] In the embodiment shown in FIGS. 1-4, the second heating element 12 is also embodied as a resistive heating element, which projects into the second chamber 16 at the first end 161 as well and comprises, in the embodiment shown in FIGS. 1-4, a thermocouple 14 as second temperature sensor. Similar as the second nozzle 37, does the second heating element 12 extend through the entire head section 17. The second heating element 12 further extends through another one of the apertures 19 in the transverse wall 18, to project into the second interior section 16a of the second chamber 16. The second heating element 12 also extends through the second chamber 16 along the longitudinal direction L over a substantial part, e.g. approximately two thirds of the length of the second chamber 16. As such, the second fuel F2 is configured to be heated over part of the length of the second chamber 16, to improve the heating of the second fuel F2.

[0236] The second heating element 12 is configured to heat the second fuel F2 in the second interior section 16a, and not in the head section 17. Hence, the transverse wall 18 in the second chamber 16 provide for thermal insulation between the second interior section 16a and the head section 17.

[0237] The first heating element 11 and the first temperature sensor 12 are arranged at least partially in the first chamber 15 and the first fuel F1 is supplied in the first chamber 15 as well. As such, the heating of the first fuel F1 only takes place in the first chamber 15.

[0238] The second heating element 12 and the second temperature sensor 13 are arranged at least partially in the second chamber 16 and the second fuel F2 is supplied in the second chamber 16 as well. As such, the heating of the second fuel F2 only takes place in the second chamber 16.

[0239] The mixing device 10 further comprises an air supply, projecting into its interior and configured to provide a flow of air through the mixing device 10, to act as a carrier for the vaporized first fuel F1 and the heated second fuel F2. The mixing device 10 is further configured to mix the fuel mixture with the air supplied by the air supply. Inside the mixing device 10, the flow of air is guided along the first heating element 11, to pick up vaporized first fuel F1, and along the second heating element 12, to pick up heated second fuel F2.

[0240] The air supply comprises an air hose that projects into the mixing device 10 indirectly, by means of an air nozzle 67. The air nozzle 67 projects into the first chamber 15 and comprises an exit opening 68, through which the flow of air is introduced in the first chamber 15. The exit opening 68 of the air nozzle 67 is located at the second end 152 of the first chamber 15 and is configured to provide the flow of air along the flow path through the first chamber 15 and the second chamber 16. The flow of air thereby acts as a carrier for the first fuel F1 as it passes along the first nozzle 27 and the first heating element 11, i.e. at which the first fuel F1 is vaporized.

[0241] The flow of air, thus comprising the first fuel F1, is directed from the second end 152 of the first chamber 15 to the first end 151 of the first chamber 15. Next, the flow of air, containing the first fuel F1, is guided towards the head section 17 of the second chamber 16. From the head section 17, the flow of air is fed into the second interior section 16a of the second chamber 16 through the apertures 19.

[0242] In the second interior section 16a, the flow of air is guided towards the discharge opening 42, located at the second end 162 of the second chamber 16, and towards the burner 40. In the second interior section 16a, the flow of air containing the first fuel F1 is passed along the second nozzle 37 where the second fuel F2 is supplied. Upon heating of the second fuel F2 by the second heating element 12, the heated second fuel F2 is mixed with the flow of air and the first fuel F1, to obtain the fuel mixture of the first fuel F1 and the second fuel F2.

[0243] The flow of air in the mixing device 10 may give rise to turbulences in the mixing device 10, which turbulences may contribute to the mixing of the first fuel F1 and the second fuel F2, i.e. with each other and with the air in the flow of air, in order to provide for a more homogeneous fuel mixture. Furthermore, with the air being mixed with the fuel mixture, primary combustion air may already be present in the mixture that is fed from the mixing device 10 towards the burner 40. This primary combustion air may contribute in reducing the formation of CO and carbon, e.g. soot, upon combusting the fuel mixture.

[0244] In FIGS. 5 and 6, an alternative mixing device according to the invention is shown, to which is referred with reference numeral 10. The mixing device 10 in FIGS. 5 and 6 is, to a large extent, similar to the mixing device 10 shown in FIGS. 1-4. In particular, their first chambers 15, 15, including the air nozzle, first nozzle, first heating element and first temperature are the same.

[0245] The housing 103 of the mixing device 10 in FIGS. 5 and 6 is free of the transverse wall and the head section. Instead, the mixing device 10 comprises a unitary second chamber 16 that is fluidly connected to the first chamber 15 by means of the opening 19. The second chamber 16 comprises, at its first head end 161, a removable head end wall 163. In FIG. 6, the head end wall 163 is shown removed from the second chamber 16, thereby allowing access into the second chamber 16. During normal use of the mixing device 10, the head end wall 163 is installed in the second chamber 16 to close off the interior of the second chamber 16.

[0246] A further difference is provided by the second heating element 12 of the mixing device 10, which has a functionally combined with the second nozzle 37. The second heating element 12 is an infrared radiant heating element, which projects into the second chamber 16 and which is configured to be subjected to an electric current through it, e.g. initiated by a control unit.

[0247] The second heating element 12 comprises a frame element 121, which comprises a number of fins, and a coil 122. The fins of the frame element 121 outwardly protrude away from each other and are together configured to guide the coil 122. The electric current is adapted to be guided through the coil 122, so that electromagnetic radiation, i.e. in the infrared regime, is emitted by the coil 122. The infrared radiation is emitted towards the second fuel F2 in the second chamber 16, in order to heat the second fuel F2 to the mixing temperature.