WO2001042716A1

WO2001042716A1 - Heating apparatus generating radiant heat and convection heat

Info

Publication number: WO2001042716A1
Application number: PCT/HU2000/000126
Authority: WO
Inventors: Attila Paics; Gyula Kovács; József Lengyel
Original assignee: Attila Paics; Kovacs Gyula; Lengyel Jozsef
Priority date: 1999-12-06
Filing date: 2000-12-05
Publication date: 2001-06-14
Also published as: AU1874501A; HU220805B1; HU9904477D0; HUP9904477A2

Abstract

A heating apparatus comprising a heating pipe element (1) emitting radiant heat, a reflector (2) arranged along at least one part of the length of the heating pipe element (1) and having a longitudinal edge part (7) on each side of the heating pipe element (1), a hood (4) arranged above at least one part of the reflector (2), and a fan (5) associated with a space between the hood (4) and the reflector (2) in order to forward heated air (3) to a required place. At least on one side of the heating pipe element (1) the hood (4) has a longitudinal edge part (8) projecting laterally and downwards over the longitudinal edge part (7) of the reflector (2) on the same side, thereby determining at least one longitudinal intake opening (10) for the heated air (3) flowing upwards into the space between the hood (4) and the reflector (2).

Description

HEATING APPARATUS GENERATING RADIANT HEAT AND CONVECTION HEAT

TECHNICAL FIELD

The invention relates to a heating apparatus generating radiant heat and convection heat The apparatus according to the invention can be particularly used for heating large size indoor spaces of buildings with a high headroom and also for heating outdoor spaces

BACKGROUND ART

According to the current practice, gas heated radiant pipe based heating units are generally used for heating purposes as mentioned above, but it is also possible to use for example hot water, steam or electrically heated radiant pipe heating units Heating by a radiant pipe heating apparatus is generally more cost efficient than other conventional, for example hot air injection or radiator heating solutions, because the same temperature sensation can be ensured at a lower air temperature, due to the temperature sensation intensifying effect of radiant heat

The radiant pipe heating units are usually installed in an upper part of spaces to be heated, and for the purpose of reflecting the radiant heat emitted upwards by the radiant pipes, a general practice is to use reflectors arranged above the radiant pipes However, the radiant pipe heated up by combustion products or a certain medium therein or by electricity, not only emits radiant heat but also so-called convection heat by heating up the air directly A problem is that the heated air carrying the convection heat generated by the radiant pipe and the reflector flows upwards as a result of its specific weight and would not heat the lower parts of the space to be heated The convection heat ratios are of a significant extent, in conventional radiant pipe heating units, the convection heat generated by the reflector is approx 5 - 8 % of the heat introduced, and the convection heat generated hy the radiant pipe is approx 30 - 40 % of the heat introduced

A known solution for reducing the convection heat emitted by the reflector is to cover its upper surface with a heat insulating material However, the generated convection heat can only be reduced slightly in this way Furthermore, another generally applied solution for utilising the convection heat is to install large ceiling fans to introduce the hot air collected and mixed in the upper part of the space to be heated into the workspace located in the lower part of the space However, this solution necessitates the use of noisy fans that have an unfavourably high power consumption, to make sure that a suitable volume of hot air is introduced into the workspace And, the ceiling fans are not suitable for utilising directly the convection heat generated

A combined convection/radiant heating apparatus is described for example in WO 98/46946 This known heating apparatus comprises a gas heated radiant pipe, which emits radiant heat and is located in the upper part of the space to be heated, a 'heat exchanger plate', i e a reflector arranged above the radiant pipe and a hood open at the bottom which surrounds the reflector from the top and from the sides An intake fan is connected to the hood by means of an opening at the top By means of the intake fan, air is injected between the hood and the reflector from the top part of the space, the air is heated up by means of the reflector and the hood and it flows downwards through slots between the longitudinal edges of the hood and the reflector

The problem of this known solution is that if the slots are narrow, the air jet vanishes on a relatively short distance without reaching the workspace If the slots are wide, then due to the relatively large air volumes flowing, fans of a large power consumption and weight are required, and the air injected will not be sufficiently warm in the given case, in fact it may have a cooling effect on a human skin above certain air velocities However, if the air jet succeeds in generating a sense of warmth, this is provided in the part of the workspace where due to the radiant heat the temperature sensation is the most favourable anyway

It is also a problem that the air jet of a relatively high velocity directed downwards has a substantial injecting effect, which accelerates the air flows around the radiant pipes The turbulence resulting from the accelerated flow cools the radiant pipes more intensively due to an increase in the heat transfer coefficient, i e the heating pipes will be cooler A slight cooling of the radiant pipes causes a substantial decrease in the radiant heat, because the radiant heat emitted to the environment is proportional to the difference between the fourth power of the absolute temperature of the radiant body and the fourth power of the absolute temperature of the environment And in radiant pipe heating the object is generally to make sure that as much radiant heat reaches the workspace as possible Therefore, cooling of the pipe reduces the efficiency of heating

A radiant pipe heating apparatus is described in DE 32 17 948 A1 In this known heating apparatus, the heat emitted upwards by the heating pipe is taken away by air flowing in a duct arranged above the heating pipe The air so heated is directed to the bottom part of the space to be heated or to other desired places In this way efforts are made to collect both radiant heat and convection heat escaping laterally or upwards, by using the air flowing in the duct consisting of a reflector- type lower section and a hood-type upper section joining the former from the top Furthermore it is described that openings can be formed in the bottom section of the duct to collect the convection heat directly

The disadvantage of this known solution is that without the slots in the bottom section of the duct, it is not possible to collect all the convection heat but it is almost entirely the radiant heat emitted upwards which is utilised This means that the air heated up by the heating pipe flows upwards by escaping laterally from the lower section of the duct On the other hand the air flowing in the duct cools the same which makes an indirect cooling effect on the heating pipe and this reduces the efficiency of radiant heating By means of the slots in the lower section of the duct all the convection heat can be collected by means of the duct but these slots excessively accelerate the air flow around the heating pipe which leads to an even more intensive cooling of the heating pipe Consequently by means of this solution it is not possible to utilise the convection heat in a way that the radiant heat is of a maximum extent A further disadvantage is that the operation of the heating apparatus is substantially influenced by slight disturbing effects for example by draught effect by changing of the operating temperature for example as a result of a variation in the calorific value of the heating gas etc , thereby upsetting the adjusted ratio of convection/radiant heating

DISCLOSURE OF INVENTION

It is an object of the invention to provide a radiant pipe based heating apparatus, by which all the convection heat generated can be utilised, while the emission of radiant heat is kept at a maximum Utilising the convection heat means that the heated air generated by convection is supplied in a directed way to the workspace or to other desired places It is another object of the invention to provide a radiant pipe heating apparatus, which is less sensitive to disturbing effects regarding the utilisation of convection heat

For a better understanding of the invention, flow processes taking place at radiant pipes are discussed below Below the reflector arranged above the radiant pipes an essentially horizontal boundary layer generates between the hot air flowing out of the reflector and the air of lower temperature below the reflector This boundary layer can be detected for example by smoke test In the air layer above the boundary layer, substantial horizontal velocities arise which on the one hand have a pipe-direction component (to compensate the temperature differences existing in the longitudinal direction) and on the other they have a component perpendicular to the pipe which is practically proportional to the convection heat escaping from below the reflector The air flow having the velocity component perpendicular to the pipe bends upwards after escaping from under the reflector Of course below the radiant pipe there is an intensive flow upwards to replace the air flowing upwards after escaping in lateral directions If all the convection heat generated is to be guided away, the longitudinal change of the convection, the internal compensation caused by disturbances, and the amount of heat arising are to be taken into consideration The flow conditions are also influenced by a non-horizontal arrangement of the radiant pipe Determining the extent of convection heat to be guided away and thereby the technical design of guiding away are only possible by an approximating method because the flow conditions are also influenced by the operating conditions, temperatures and draught conditions in the space to be heated

IT IS advisable to provide a technical design allowing significant tolerances in dimensioning, without leading to the undercooling of radiant pipes In this way the appropriate utilisation of the total convection heat is possible while retaining a maximum radiant effect

According to the description above, slots formed in the reflector deteriorate the radiation efficiency The suction flow lines around such slots practically show a roughly symmetric flow pattern Therefore, such slots must be dimensioned in an extremely accurate way, and theoretically unchanged operating conditions must be maintained to make sure that exactly the generated convection heat is guided away Because the slots are in the flow zones naturally arising at radiant pipes they cause turbulences and extra air flows which have a cooling effect on the radiant pipe A horizontal intake opening designed at the edge of the reflector is not the most appropriate solution either, because its flow conditions are also symmetric This means that if the air volume extracted is small one part of the convection heat escapes, and if it is large the flow conditions under the reflector are accelerated

To eliminate all these problems and to accomplish the objectives above, the invention is a heating apparatus generating radiant heat and convection heat comprising a heating pipe element emitting radiant heat a reflector arranged along at least one part of the length of the heating pipe element and having a longitudinal edge part on each side of the heating pipe element, the reflector reflecting back into a space to be heated heat rays emitted by the heating pipe element a hood arranged above at least one part of the reflector, and a fan associated with a space between the hood and the reflector in order to forward heated air to a required place According to the invention, at least on one side of the heating pipe element the hood has a longitudinal edge part projecting laterally and downwards over the longitudinal edge part of the reflector on the same side thereby determining at least one longitudinal intake opening for the heated air flowing upwards into the space between the hood and the reflector wherein the heated air flowing into the space betv/een the hood and the reflector is forwarded to the required place by means of extraction from the space by the fan

The heating apparatus according to the invention enables that the total convection heat generated can be guided away and supplied to the required place By forming an intake opening collecting the convection heat according to the invention, a convection heat utilisation solution is provided, which is self-regulating in a relatively wide interval, in which self-regulating interval the position of the boundary layer changes by an extremely small extent Thereby, utilisation of the total amount of the convection heat is achieved, without any undercooling of the heating pipe element According to our measurements, the self-regulating design allows a relatively large, ± 50 % change in the volumetric flow or in the intake opening width

In a preferred embodiment of the invention, the longitudinal edge parts of the reflector are arranged essentially on the same level compared to the heating pipe element, and the hood has a longitudinal edge part defining a longitudinal intake opening on each side of the heating pipe element This design is advantageous for a heating apparatus fitted on a ceiling From the aspect of guiding the convection air flow, it is advantageous if the longitudinal edge parts of the reflector are bent outwards from the heating pipe element and upwards, and the longitudinal edge parts of the hood are bent towards the heating pipe element

In another preferred embodiment, one of the longitudinal edge parts of the reflector is arranged on a higher level than the other where the at least one longitudinal intake opening is formed at the higher longitudinal edge part of the reflector This design is advantageous for wall mounted heating units In this case the longitudinal edge part of the reflector arranged on a higher level is preferably bent outwards from the heating pipe element and upwards and the corresponding longitudinal edge part of the hood is bent downwards

It is particularly advantageous if in the space between the hood and the reflector in the flow direction of the heated air flowing upwards after the at least one longitudinal intake opening, a longitudinal slot is formed with a width smaller than that of the intake opening By means of this slot, the extracted air volume can be appropriately regulated, while the width of the intake opening can be selected appropriately large for safe extraction. The longitudinal slot can be preferably formed between an inner wall of the hood and an adjacent edge of the reflector.

The heating pipe element can be a radiant pipe having an operating temperature varying along its length, for example a gas heated or hot water heated radiant pipe, and the at least one longitudinal intake opening and/or the longitudinal slot can be formed with a width varying proportionally with the operating temperature of the heating pipe element along its length. Alternatively, the reflector and the hood can be arranged in a way steadily ascending compared to the heating pipe element in a travelling direction of a medium flowing in the heating pipe element. The radiant pipe can also be a steam heated or electrically heated radiant pipe having an essentially constant operating temperature along the total length thereof.

The convection heat can be preferably guided away by a fan supplying the heated air via an air duct or directly to the bottom part of the space to be heated.

The suction of the fan, as well as the width of the at least one longitudinal intake opening or the width of the longitudinal slot can be preferably adjusted in a way that the amount of the heated air flowing into the space between the reflector and the hood essentially corresponds to the amount of heated air flowing upwards by the reflector without the hood.

The heating pipe element can be an essentially straight radiant pipe or a radiant pipe bent in a "U" shape. In the given case the top surface of the reflector can be covered with a heat insulating material.

BRIEF DESCRIPTION OF DRAWINGS

Hereinafter, the invention will be described by means of preferred embodiments as shown in the drawings, where

Fig. 1 is a partly exploded schematical view of a heating apparatus according to the invention,

Fig. 2 is a schematic cross section of the embodiment in Fig. 1 ,

Figs. 3 and 4 are magnified views of section A in Fig. 2 showing flow conditions. Figs 5-7 are schematic cross sections of further preferred embodiments of the invention,

Fig 8 is a schematic side view of a preferred embodiment having a heating pipe element with a temperature varying along its length, and

Fig 9 is a diagram depicting an air layer having a thickness compensated by the embodiment in Fig 8

MODES FOR CARRYING OUT THE INVENTION

The heating apparatus depicted in Fig 1 comprises a heating pipe element

1 which in the depicted embodiment is an essentially straight gas heated radiant pipe A burner known per se and necessary for gas heating is not shown in the figure This embodiment is advantageous for ceiling installations, where a reflector

2 made of sheet metal for reflecting heat radiation emitted upwards by the heating pipe element 1 is arranged essentially in a symmetric way above the heating pipe element 1 A hood 4 made of sheet metal is located above the reflector 2 A space between the hood 4 and the reflector 2 is confined by end walls 9 and through an opening formed in one of the end walls 9 a fan 5 is attached to the space between the hood 4 and the reflector 2 An air duct not shown here may be connected to an outlet stub of the fan 5

The end walls 9 are formed in the embodiment shown in Fig 1 and also in further embodiments in a way that they close fully from the side the structure consisting of the reflector 2 and the hood 4 at its longitudinal ends Therefore the air heated up by the heating pipe element 1 is unable to escape upwards at the longitudinal ends of the reflector 2, but as described below it only flows into the space between the hood 4 and the reflector 2

In the schematic cross section of Fig 2 it is shown that the reflector 2 has a longitudinal edge part 7 on each side which edge parts 7 are formed in the preferred embodiment depicted in a way that they curve outwards and upwards from the heating pipe element 1 The two longitudinal sides of the hood 4 also have a longitudinal edge part 8 on each side which are projecting over the respective longitudinal edge parts 7 of the reflector 2 in a lateral and downward direction, and so they define a longitudinal intake opening 10 each, through which the air 3 heated up by the heating pipe element 1 is able to flow into the space between the hood 4 and the reflector 2. It is depicted in the figure that for the appropriate exhaustion of the heated air 3, the longitudinal edge parts 8 of the hood 4 are formed in a way that they curve towards the heating pipe element 1. In the given case, the edge parts 8 can be bent towards the heating pipe element 1 and upwards. In this case the upward bent edge ends of the edge parts 8 of the hood 4 may act as reflectors, but they are considered as part of the hood 4 according to the invention.

The fan 5 associated with the space between the hood 4 and the reflector 2 can forward the heated air 3 by extracting from the space via an air duct 6 to the required place, for example to a bottom part of the space to be heated which is subjected to cold radiation or draught. This part of the heated space can be an industrial gate or a wall fitted with large windows. The air 3 heated up for heating purposes can be guided furthermore not only into the heated space but also through an appropriate air duct for example to another room, or it may also be used in industrial technologies.

Figs. 3 and 4 depict flow conditions corresponding to two different suction per ormances of the fan 5. The volumetric flow V depicted in Fig. 3 is of such an extent that the distance H between the boundary layer and the bottom of the edge part 7 is exactly identical with the distance between the lowest point of the edge part 7 and that of the edge part 8. In this case a relatively low amount of cold air is introduced into the volumetric flow V, and a majority part M thereof is the air heated up by the heating pipe element 1.

In the situation depicted in Fig. 4, the fan 5 connected to the space between the hood 4 and the reflector 2 generates a volumetric flow V > V, when the distance of the boundary layer is reduced to H'. In this case much more cold air is introduced into the volumetric flow V, i.e. its M' part comprising the heated air will be smaller, but even in this case it can be ensured that the total convection heat generated is guided away and utilised. The situations shown in these two figures may arise not only by changing the suction performance of the fan 5, but also as a result of various disturbances during operation, for example draught, a change in the operating temperature, etc. The self-regulating design according to the invention is extremely advantageous on the one hand because it is practically insensitive to disturbances generally and frequently arising in spaces to be heated, and on the other because the extracting of hot air practically may not be dimensioned exactly

In the depicted preferred embodiments of the heating apparatus according to the invention, in the space between the hood 4 and the reflector 2 in the flow direction of the air 3 heated up and flowing upwards, after the at least one longitudinal intake opening 10 a longitudinal slot 13 is formed with a width smaller than that of the slot This slot 13 is formed in the depicted embodiments between an inner wall of the hood 4 and an edge of the reflector 2 next to the internal wall By means of this slot 13, the amount of the extracted air can be appropriately regulated, while the width of the intake opening 10 can be dimensioned sufficiently large for safe extraction For example, the width of the slots 13 can be between 0 5 and 20 mm

In the heating apparatus according to the invention, in the case of a larger air exhaustion, the boundary layer is shifted upwards automatically and when a smaller amount of air is extracted, it is shifted downwards In this way in both cases an exhaustion corresponding to the total amount of convection heat is accomplished without any undercooling of the heating pipe element 1 According to our measurements, the self-regulating design allows a relatively large, ± 50 % change in the volumetric flow or in the slot width compared to the respective middle values It is advisable to choose the exhaustion of the fan 5 and the width of the at least one longitudinal intake opening 10 and/or the width of the longitudinal slot 13 in a way that the amount of the heated air 3 flowing into the space between the reflector 2 and the hood 4 essentially corresponds to the amount of heated air 3 flowing upwards by the reflector 2 without the hood 4 In this case the smallest interference is made in the flow conditions around the heating pipe element 1

From the aspect of a better heating efficiency it is advantageous that the collecting of heated air 3 is done in the space between the hood 4 and the reflector 2, because in this way a hood insulating effect is also accomplished This results from the fact that the difference between the surface of the hood 4 and that of the reflector 2 is less than the difference between the temperature differences between the respective surface and its surrounding air

The embodiment depicted in Fig 5 is advantageous because it allows wall mounting The reflector 2 and the hood 4 of the heating apparatus are turned by about 30° around the heating pipe element 1 , as a result of which the heating apparatus radiates the heat in a slant way to the bottom part of the space to be heated In this embodiment, there is no longitudinal intake opening 10 between the edge part 7 of the reflector 2 arranged at a lower level and the respective edge part 8 of the hood 4, but the air 3 heated up by convection is flowing into the space between the hood 4 and the reflector 2 through a longitudinal intake opening 10" between the edge part 7 of the reflector 2 arranged at a higher level and the respective edge part 8 of the hood 4 The width of the intake opening 10' of this embodiment is preferably approximately twice of the width of the intake opening 10 of the embodiment in Fig 2 In this embodiment it is advisable to bend the edge part 8 of the hood 4 determining the intake opening 10' essentially vertically downward In a way similar to Fig 5 the heating apparatus can be turned arbitrarily in a range between 0 and 30° according to the required heating conditions

The embodiment in Fig 6 differs from that according to Fig 5 in that the collection of the air 3 heated up by convection is carried out in a space determined by a hood 11 arranged above one part of the reflector 2 only In this way less plate is required for producing the heating apparatus In this embodiment a heat insulating material 12 is preferably fitted on a top surface of the reflector 2 so as to reduce the amount of heat transferred by the reflector 2 to the ambient air

In the embodiment according to Fig 7 the heating pipe element 1 is a radiant pipe bent in a U shape known per se the two branches of which are arranged below the common reflector 2

In Fig 8 a preferred embodiment of the heating apparatus is shown in which the operating temperature of the heating pipe element 1 varies along its length This phenomenon can be observed for example in gas heated or hot water heated heating pipe elements 1 where in the flow direction of the medium flowing in the heating pipe element 1 , the operating temperature of the heating pipe element 1 decreases steadily In such cases the thickness of the air layer consisting of heated air above the boundary layer and the velocity of its generation along the length of the heating pipe element 1 decrease steadily in the flow direction of the flowing medium In this case the utilisation of the total convection heat can be ensured for example in a way that the longitudinal intake openings 10 and/or the longitudinal slots 13 along the length of the heating pipe element 1 are formed with a width changing proportionally with the operating temperature of the heating pipe element 1 The solution shown in Fig 8 can also be advantageous where in the travelling direction of the medium depicted by an arrow and flowing in the heating pipe element 1 , the reflector 2 and the hood 4 are arranged in an ascending manner compared to the heating pipe element 1 In this way it is not necessary to change the width of the intake openings 10 and/or that of the longitudinal slots 13, which results in more simple manufacturing The ascending a is preferably approx 0 5 - 3 %

In the heating apparatus designed with ascending reflector 2 and hood 4 the thickness of the air layer is compensated along the length of the heating pipe element 1 This is shown in Fig 9, which depicts an air layer hatched vertically and exhibiting thickness Vi at the start of the hood 4 and thickness v₂ at the end of the hood 4, this air layer characterising a heating apparatus without an ascending α In the heating apparatus with the ascending α an air layer with a uniform thickness v_: is developed In addition to the uniform intake opening and/or slot width this design has the further advantage that the ascending α influences the temperature distribution of the heating pipe element 1 in a way that the temperature difference between its starting and end points will be smaller than in the case of a design without the ascending α

If the heating pipe element 1 is for example a steam heated or electrically heated radiant pipe, the operating temperature of which does not vary along its length, or a gas heated radiant pipe having a uniform operating temperature as a result of internal insulation, the use of the above inclined design is not necessary

The heating apparatus according to the invention can be implemented other than the embodiments described, or as a combination thereof In the heating apparatus according to the invention, it is not necessary to form reducing slots 13 after the intake openings 10 and 10', but the exhaust of the heated air 3 may also be regulated by the width of the intake openings 10 and 10'. It is possible to fit several radiant pipes with reflectors below a single hood and to implement the tilted heating apparatus of the wall mounted type with an ascending α. It is also possible furthermore to arrange the two branches of the U shaped radiant pipe under separate reflectors, when between the two reflectors a further longitudinal intake opening can be designed for the heated air flowing upwards. Furthermore, the heating pipe element can be designed in a form other than the straight and "U" shapes.

It will be evident to those skilled in the art that the above disclosure is exemplary only and that various other alternatives, adaptations and modifications may be made within the scope of the present invention as defined by the following claims.

Claims

1 A heating apparatus generating radiant heat and convection heat, comprising a heating pipe element emitting radiant heat, a reflector arranged along at least one part of the length of the heating pipe element and having a longitudinal edge part on each side of the heating pipe element, the reflector reflecting back into a space to be heated heat rays emitted by the heating pipe element, a hood arranged above at least one part of the reflector, and a fan associated with a space between the hood and the reflector in order to forward heated air to a required place, c h a r a c t e r i s e d in that at least on one side of the heating pipe element (1 ) the hood (4, 11 ) has a longitudinal edge part (8) projecting laterally and downwards over the longitudinal edge part (7) of the reflector (2) on the same side, thereby determining at least one longitudinal intake opening (10 10') for the heated air (3) flowing upwards into the space between the hood (4 1 1 ) and the reflector (2), wherein the heated air (3) flowing into the space between the hood (4, 11 ) and the reflector (2) is forwarded to the required place by means of extraction from the space by the fan (5)

2 The heating apparatus according to claim 1 , characterised in that the longitudinal edge parts (7) of the reflector (2) are arranged essentially on the same level compared to the heating pipe element (1 ), and the hood (4) has a longitudinal edge part (8) defining a longitudinal intake opening (10) on each side of the heating pipe element (1 )

3 The heating apparatus according to claim 2, characterised in that the longitudinal edge parts (7) of the reflector (2) are bent outwards from the heating pipe element (1 ) and upwards, and the longitudinal edge parts (8) of the hood (4) are bent towards the heating pipe element (1 )

4 The heating apparatus according to claim 1 , characterised in that one of the longitudinal edge parts (7) of the reflector (2) is arranged on a higher level than the other, where the at least one longitudinal intake opening (10') is formed at the higher longitudinal edge part (7) of the reflector (2)

5 The heating apparatus according to claim 4, characterised in that the longitudinal edge part (7) of the reflector (2) arranged on a higher level is bent outwards from the heating pipe element (1 ) and upwards, and the corresponding longitudinal edge part (8) of the hood (4, 11) is bent downwards

6 The heating apparatus according to claim 1 , characterised in that in the space between the hood (4, 11 ) and the reflector (2), in the flow direction of the heated air (3) flowing upwards after the at least one longitudinal intake opening (10, 10'), a longitudinal slot (13) is formed with a width smaller than that of the intake opening (10, 10')

7 The heating apparatus according to claim 6, characterised in that the longitudinal slot (13) is formed between an inner wall of the hood (4, 1 1 ) and an adjacent edge of the reflector (2)

8 The heating apparatus according to claim 6, characterised in that the heating pipe element (1 ) is a radiant pipe having an operating temperature varying along its length, for example a gas heated or hot water heated radiant pipe and the at least one longitudinal intake opening (10, 10') and/or the longitudinal slot (13) is formed with a width varying proportionally with the operating temperature of the heating pipe element (1) along its length

9 The heating apparatus according to claim 1 , characterised in that the heating pipe element (1) is a radiant pipe having an operating temperature varying along its length, for example a gas heated or hot water heated radiant pipe and the reflector (2) and the hood (4, 11) are arranged in a way steadily ascending compared to the heating pipe element (1 ) in a travelling direction of a medium flowing in the heating pipe element (1)

10. The heating apparatus according to claim 1 , characterised in that the heating pipe element (1) has an essentially constant operating temperature along its length, for example it is a steam heated or electrically heated radiant pipe.

11. The heating apparatus according to claim 1 , characterised in that the fan (5) supplies the heated air (3) via an air duct (6) or directly to a bottom part of the space to be heated.

12. The heating apparatus according to claim 6, characterised in that the suction of the fan (5), as well as the width of the at least one longitudinal intake opening (10, 10') or the width of the longitudinal slot (13) are adjusted in a way that the amount of the heated air (3) flowing into the space between the reflector (2) and the hood (4, 11) essentially corresponds to the amount of heated air (3) flowing upwards by the reflector (2) without the hood (4, 11 ).

13. The heating apparatus according to claim 1 , characterised in that the heating pipe element (1 ) is an essentially straight radiant pipe.

14. The heating apparatus according to claim 1 , characterised in that the heating pipe element (1 ) is a radiant pipe bent in a "U" shape.

15. The heating apparatus according to claim 1 , characterised in that the top surface of the reflector (2) is covered with a heat insulating material (12).