HEATING APPARATUS

Abstract: The present invention relates to an apparatus for heating fluid in a heating system, such as central heating, comprising at least one heating device with: a container (3) filled with transfer medium, having an inlet connection (4) and an outlet connection (5) and in the interior thereof an electric heating element (9) and a heat accumulator; a feed-through pipe functioning as heat exchanger which is immersed in the transfer medium and connected to the inlet connection and the outlet connection; and pumping means (6) connected to the feed-through pipe to push the fluid therethrough. Particularly mass and heat characteristics of the transfer medium, heat exchanging surface area of the heating element, heating surface area of the feed-through pipe, power of the heating element and volume of the feed-through pipe are taken such that the transfer medium forms the heat accumulator in the container.

Description: HEATING APPARATUS The present invention relates to an apparatus for heating fluid in a heating system, such as central heating, comprising at least one heating device with: - a container filled with transfer medium, having an inlet connection and an outlet connection and in the interior thereof an electric heating element and a heat accumulator; - a feed-through pipe functioning as heat exchanger which is immersed in the transfer medium and connected to the inlet connection and the outlet connection; and - pumping means connected to the feed-through pipe to push the fluid therethrough. Such an apparatus is known from the French patent application 2.707.738 in which a container for a salt solution is arranged as separate heat accumulator. A drawback of such a known apparatus is that the container with the salt solution does not represent an effective method for buffering heat in the apparatus. In addition, damage to or in any case an adverse effect on the container can be caused by the salt solution, wherein the container, particularly when it is manufactured from metal, can corrode or oxidize. If this container begins to leak and the salt solution enters the oil, the heat characteristics thereof are affected in a negative way, wherein heat transfer deteriorates. Assuming therefore_ that the efficiency of the known apparatus is adequate in practice, it will deteriorate in the particular case of leakage of the salt solution into the oil. The object of the invention is to obviate or at least diminish the above stated drawback and an apparatus is provided for this purpose which is distinguished in that particularly mass and heat characteristics of the transfer medium, heat exchanging surface area of the heating element, heating surface area of the feed-through pipe, power of the heating element and volume of the feed-through pipe are taken such that the transfer medium forms the heat accumulator in the container. In an apparatus according to the present invention the transfer medium, for instance the oil, serves not only for heat transfer for direct heating of the fluid but also for buffering of heat which is transferred to the fluid when the heating element is rendered inoperative. This is realized according to the present invention without making use of an additional container having therein as accumulator a solution which can possibly damage the apparatus . An apparatus is moreover provided according to the invention with which an efficiency is possible which is considerably higher than in the known art, since heating of the fluid takes place directly from the transfer medium when the heating element is rendered inoperative and not, as in the known art, indirectly from the accumulator via the transfer medium. In a first embodiment an apparatus according to the present invention comprises the measure that the heating element is electric and is connected via switching means to an electrical power source for activating and deactivating the heating element . When use is made herein of an electric heating element in the above described assembly with the contain- er, the heat transfer medium and the feed-through pipe, wherein this latter is immersed in the heat transfer medium, no gas feed pipes, flue gas discharge or chimney need be provided for an apparatus in for instance a central heating system, so that installation costs are_ low and there is a large measure of freedom in the choice of the location where it is wished to install the apparatus, wherein only a contact for electrical power supply is required. An apparatus according to the present invention is also relatively inexpensive to purchase and simple and quick to install. The apparatus can function as heat exchanger for a room in which it is placed and as heat source for the heat exchangers in other room areas, so that central heating pipes for a connection to a separate boiler or the like are not required. At least one heat exchanger and a considerable length of piping and fluid are therefore saved. There is further no danger of fire or explosion and the apparatus generates practically no noise. In addition, the apparatus according to the present invention is environmentally-friendly since no emission of CO compounds occurs. Nor does regular servicing have to take place and the apparatus is durable, wherein it can function continuously for instance for twenty years with only a very small chance of malfunction. In the first embodiment the switching means are preferably connected to heat sensors in the heat transfer medium in order to switch in response to a temperature signal originating therefrom such that the electric heating element is only in operation when this is found to be necessary on the basis of the temperature of the heat transfer medium being below a predetermined threshold value . In the first embodiment the container preferably has an axial length direction, such as a cylindrical contain- er, wherein the inlet connection and the outlet connection are arranged at least close to one of the axial ends of the container and the heating element is placed through the other of the axial ends of the container and extends in the length direction of the container. An optimal compact configuration of an apparatus according to the invention is hereby achieved. The electric heating element preferably has a power in the order of magnitude of 1-1.5 kWh. A power is herein produced by the heating element sufficient to bring the fluid to a temperature of for instance 55°C, which is sufficient for a more than adequate heating of room areas where a heat exchanger connected to the apparatus is arranged. At such relatively low temperatures, for instance 55°C, no specific safety measures have to be implemented such as those prescribed (by law) for heating boilers in which temperatures close to or higher than at least 100°C are reached. In a second embodiment an apparatus according to the present invention comprises the measure that the feed- through pipe is wound at a predetermined distance round the heating element. The heat transfer characteristic between heating element and feed-through pipe is herein optimal. In a container with an axial length direction the heating element herein preferably lies substantially parallel to the length direction of the container, wherein the feed-through pipe is wound helically round the heating element so that turbulence of the transfer medium occurs round the heating element and the feed-through pipe during operation of the heating element. The second embodiment preferably comprises the measure that the container has a length of 510 mm and an internal dimension of 146 mm, wherein the feed-through pipe has a diameter of 22 mm and is wound 19 times fully round the heating element. Inter alia as a result of this dimensioning the ratios between surface areas of the heating element and the feed-through pipe for effective heat transfer are such that this transfer, and therefore the efficiency, are optimal. In a third embodiment an apparatus according to the present invention is such that the heat transfer medium comprises an oil, wherein an oil displays practically no expansion as temperatures rise. It is hereby possible in a wide range of temperatures to make use of a container without special strengthening to counter the effects of expansion under the influence of a higher temperature. This is already substantially avoided in that the temperature of the fluid can remain relatively low, in the order of magnitude of 55°C, wherein it will be possible for the temperature of the medium in the container to remain at all times below 95°C in normal operation of the apparatus. An apparatus in the third embodiment preferably has the measure that the oil is a synthetic oil such as an oil marketed commercially by the company "Texaco" under the brand name "Texatherm HT" , the heat transfer characteristics of which are such that the oil retains for a long time a temperature given thereto and also heats the fluid flowing through the feed-through pipe efficiently and effectively. Even in the case of failure of all components pres- ent in an apparatus according to the present invention and contributing indirectly or directly to the control of the temperatures of the fluid and the medium in the container, the oil, or medium, will never reach a temperature higher than 110 °C. It is possible to envisage here the failure of the switching means, pump, heat sensors etc., and then only in the case of simultaneous failure of said components, which event cannot possibly occur in practice . The present invention further relates to a heating system provided with at least one heating apparatus as described above. The invention will be further elucidated hereinbelow with reference to an embodiment thereof. In the drawing: fig. 1 shows a partly cut-away perspective view of a heating apparatus according to the present invention; fig. 2 shows a perspective view of separate parts of a component of the heating apparatus shown in fig. 1; fig. 3 shows a view in section of the component shown in fig. 2 in the assembled state; and fig. 4 is a perspective view corresponding with fig. 3. The apparatus 1 shown in fig. 1 comprises three heating devices in the form of containers 3, whereof inlet connections 4 and outlet connections 5 of the containers 3 placed one above the other are mutually connected in series, wherein a pump 6 is connected between the inlet connection 4 of the lowest container 3 in the figure and a pipe 7 coming from heat exchangers such as radiators (not shown) . The outlet connection 5 from_ the uppermost container 3 in the figure is connected to a pipe 8 running to the heat exchangers . Round the assembly of containers 3 can be arranged a housing 2 which is shown here in removed position. In operation the containers per se form radiators as a result of the heat generated thereby to the environment, so that separate heat exchangers in the room area where apparatus 1 is placed are not necessary. One of the containers 3 will be further described hereinbelow with reference to figures 2-4. Container 3 is cylindrical and encases an electric heating element 9 and, in the assembled situation, a feed-through pipe 10 which is wound in a spiral round heating element 9 and which is connected to inlet connection 4 and outlet connection 5. Container 3 is otherwise sealed and filled with a heat transfer medium in the form of oil 11. This oil is synthetic such as that marketed commercially by the company "Texaco" under the brand name "Texatherm HT" . The heat characteristics of this or a similar oil are such that once a quantity of heat has been supplied it retains this heat for a long time and can be heated very quickly. Container 3 is filled with the oil to a level lower than complete filling, here 95%. There follows below a summary of the oil applied here and known as Texaco "Texatherm HT" . APPLICATIONS For all heat transfer systems with oil film temperatures up to 320°C. COMPOSITIONS Texatherm HT consists of a mixture of aromatic syn- thetic hydrocarbons with a high boiling point. SPECIFIC PROPERTIES Natural detergent capacity High thermal conduction coefficient Very high oxidation and thermal stability Low solidification point and low viscosity Odourless and non-toxic EXPLANATORY NOTE Maximum heat transfer in wide temperature range Limited deposition on components and in oil, long_ life-span Quick and simple start-up characteristics Code 29993 ISO class 22 ANALYTICAL VALUES Colour, ASTM 0.5 density 15°C kg/m 3 907 Flash-point COC degrees 200 Flow point degrees -45 Boiling point degrees 330 kin. vise , at 20°C mm 2 /s (cSt) 60.0 at 40°C 22.8 at 50°C 15.5 at 100°C 4.0 at 200°C 1.0 THERMAL CONDUCTION COEFFICIENT At 100°C W/m,C 0.123 At 300°C W/m,C 0.109 SPECIFIC HEAT At 100°C kJ/kg,C 2.08 At 300°C kJ/kg,C 2.79 max. film temp. degrees 320 auto- ignition temp. degrees 370 Conr. carbon residue %m 0.01 ash %m 0.001 Heat sensor 12 is arranged in the oil 11 as component of the electric heating element 9 in order to deter- mine the temperature of the oil 11. The measurement signal herefrom is transmitted to switching means (not shown) placed between electric heating element 9 and the power supply for the purpose of selectively activating ^ or deactivating the electric heating element on the basis thereof. The heating element is activated and deactivated to bring about a practically constant temperature of the transfer medium in the form of oil 11, for instance within tolerance limits of 0% - minus 8%. In order to obtain a temperature of the fluid running through the feed-through pipe 10 of approximately 55°C, a temperature of the medium, the oil, of 85 to 90°C is sufficient. Even in the very exceptional case for a temperate climate such as that prevailing in Western Europe of an outside tern- perature of -10°C and hard wind, such as force 6, a comfortable temperature of for instance about 21°C can be achieved in living areas with use of an apparatus according to the present invention as "heating boiler" in a central heating installation. As a result of this switching characteristic of the apparatus in combination with the thermal properties of the heat transfer medium applied therein, heat transfer to the fluid continues even after the heating element has been (temporarily) deactivated. This is of great importance in the realization of very economical characteristics in combination with a favourable ratio between volume or mass and heat characteristics of the heat transfer medium, surface of the heating element available for heating, surface of the feed-through pipe available for heat exchange, the fluid content of the feed-through pipe, power of the heating element and so on. This behaviour which yields savings is shown unequivocally in the following survey. Average living area temperatures of the Atrium VHR type 15 and 20 Settings of the Boiler temperatures thermocontrol 40 45 50 55 60 65 70 75 80 Room temperatures Outside temp. Well 18 19 20 21 22 22+ 23 23+ 24 -10 insulated 19 20 21 22 22+ 23 23+ 24 - 5 dwelling 20 21 22 23 23+ 24 - 0+ 21 22 23 23+ 24 + 5 22 23 24 +10 23 24 +15 Poorly insulated dwelling 18 19 20 21 21+ 22 22+ 23 -10 18 19 20 21 21+ 22 22+ 23 23+ - 5 19 20 21 22 22+ 23 23+ 24 - 0+ 20 21 22 23 23+ 24 + 5 21 22 23 24 +10 22 23 24 +15 Non- insulated dwelling 18 19 19+ 20 20+ 21 -10 18 19 19+ 20 20+ 21 21+ - 5 18 19 20 20+ 21 21+ 22 22+ - 0+ 18 19 20 21 21+ 22 22+ 23 23+ + 5 19 20 21 22 23 24 +10 20 21 22 23 24 +15 Energy 45 70 90 130 150 190 220 250 290 consumption Average energy consumption per hour per 1000 Watt to radiators Example: the thermocontrol is set to 45°C and at that moment 6 Kw of radiators is in use, the energy consumption is then 6 x 70 Watt = 420 Watt The container 3, feed-through pipe 10 and the spiral have the following dimensioning: the container has a length of 510 mm and an inner diameter of 150 mm, wherein the feed-through pipe has a diameter of 22 mm and is trained 19 times fully round the heating element, of which heating element a heating part placed in the container has a length of approximately 460 mm. Other dimensionings and ratios thereof are of course also possible. However, with the above described dimensions it has been found that the ratios between the surfaces serving for heat transfer, such as the heat- transferring surface of the heating element and the heat- absorbing surface of the feed-through pipe, in combination with the volume in the container, are such that an optimum efficiency is realized. In addition to that already shown and described here, an apparatus according to the present invention is also suitable for applications other than a central heating installation only. An apparatus with a single container can for instance be used for floor heating, wherein such a single container already generates sufficient heat for such a floor heating. The above described apparatus with three containers further provides sufficient heat for an average family home . For a larger than average house or a poorly or non- insulated dwelling, an apparatus according to the present invention can be provided with more than three containers to provide a desired temperature. Nor is the invention limited to heating systems for room areas but can also be employed for hot water supply or similar alternative application, such as liquid heat- ing for oil. As alternative in the above described embodiment it is also possible to make use of a heat transfer medium other than the "Texatherm HT" oil marketed by the company "Texaco", such as water, cooling liquid, antifreeze and the like. In addition, the foregoing description of an apparatus according to the present invention with reference to the drawing only mentions serial connection of the containers, wherein it is noted that parallel connection is equally possible, which is a further indication that alternatives are possible within the scope of the invention which have remained undis- cussed here but which will occur to a skilled person on reading of the description. *****

Claims: CLAIMS 1. Apparatus for heating fluid in a heating system, such as central heating, comprising at least one heating device with: - a container filled with transfer medium, having an inlet connection and an outlet connection and in the interior thereof an electric heating element and a heat accumulator; - a feed-through pipe functioning as heat exchanger which is immersed in the transfer medium and connected to the inlet connection and the outlet connection; and - pumping means connected to the feed-through pipe to push the fluid therethrough, characterized in that particularly mass and heat characteristics of the transfer medium, heat exchanging surface area of the heating element, heating surface area of the feed-through pipe, power of the heating element and volume of the feed-through pipe are taken such that the transfer medium forms the heat accumulator in the container. 2. Apparatus as claimed in claim 1, characterized in that the container has a length of 510 mm and an internal diameter of 150 mm, wherein the feed-through pipe has an outer diameter and an inner diameter of respectively 22 mm and 19.6 mm and is wound 19 times fully round the heating element. 3. Apparatus as claimed in claim 1 or 2 , characterized in that the heating element is connected via switching means to an electrical power source for selectively activating and deactivating the heating element and the apparatus further comprises adjusting means with which a desired temperature of the transfer medium can be adjusted corresponding with a degree of heating. 4. Apparatus as claimed in claim 3, characterized in that the switching means are adapted to activate the heating element when an adjusted temperature cools by approximately eight percent, wherein the switching means are connected to a heat sensor in the heat transfer medium. 5. Apparatus as claimed in any of the foregoing claims, characterized in that the container has an axial length direction, such as a cylindrical container, wherein the inlet connection and the outlet connection are arranged at least close to one of the axial ends of the container and the heating element is placed through the other of the axial ends of the container and extends in the length direction of the container. 6. Apparatus as claimed in any of the foregoing claims, characterized in that the electric heating element has a power in the order of magnitude of 1.5 kWh. 7. Apparatus as claimed in any of the foregoing claims, characterized in that the feed-through pipe is wound at a predetermined distance round the heating element . 8. Apparatus as claimed in claims 5 and 7, characterized in that the heating element lies substantially parallel to the length direction of the container, wherein the feed-through pipe lies helically round the heating element . 9. Apparatus as claimed in any of the foregoing claims, characterized in that the heat transfer medium comprises an oil. 10. Apparatus as claimed in claim 9, characterized in that the oil is a synthetic oil. 11. Apparatus as claimed in claim 10, characterized in that the synthetic oil is an oil marketed by the company "Texaco" under the brand name "Texatherm HT" . 12. Heating system comprising pipes and at least one heat exchanger, such as a radiator, and a heating apparatus as claimed in any of the foregoing claims . 13. Heating system as claimed in claim 12, character- ized by at least two heating apparatuses. 14. Heating system as claimed in claim 13, characterized in that the heating apparatuses are connected in series . 15. Heating system as claimed in claim 14, characterized in that the heating apparatuses are arranged in a collective housing. 16. Heating system as claimed in claim 15, characterized in that the housing functions per se as heat exchanger . *****

Inventors: VAN DEN BERG ROBERT FERDINAND, VAN DEN BERG, ROBERT, FERDINAND, ALWIN
Applicants: DEN BERG ROBERT FERDINAND ALWI, VAN DEN BERG, ROBERT, FERDINAND, ALWIN
Application year: 1997
Main classification: F24H1
IPC codes: F24H1, F24H7