Heat exchanger with recirculation

A heat exchanger wherein an upright insulated outer jacket contains a body of relatively cold liquid and spacedly surrounds an upright hollow cylindrical heat conducting body which, in turn, spacedly surrounds a helical heating body confining a flowing heating medium. The upper and lower ends of the heat conducting body are open so that cold liquid can enter the heat conducting body from below to exchange heat with the medium in the helical heating body, to thereby rise in the heat conducting body, and to issue at the upper end of the heat conducting body. The upper end of the heat conducting body has a flow restrictor which defines an outlet opening for the heated liquid. An electric heater can be installed in the outer jacket to heat the liquid when the supply of warmer medium is insufficient.

BACKGROUND OF THE INVENTION 
The invention relates to a heat exchanger for transferring the heat 
contents of a warm medium to a liquid to be heated, with a substantially 
upright insulated outer jacket and a heat conducting body that guides the 
flow of the cooling liquid and that extends in the interior of an inner 
space surrounded by the outer jacket. 
Heat exchangers of this type serve particularly for the reclaiming of heat 
from heated cooling media, from waste water and from naturally warm media. 
Their heat contents could have been heretofore utilized only with 
difficulty. Attempts at the reclaiming of this heat have been only very 
reluctantly realized in practice, inasmuch as the investment expenditures 
were very high in comparison to the reclaimed heat. In view of the 
relatively small temperature gradient, it was necessary, as a rule, to 
operate with large heating surfaces. Recently, the considerations for the 
construction of heat exchangers which are suited for these purposes have 
again gained in importance in view of the rising costs of energy and 
increasing demands for environmental protection. 
OBJECTS AND SUMMARY OF THE INVENTION 
Consequently, it is an object of the present invention to so improve the 
heat exchanger of the initially mentioned type that good efficiency is 
obtained at a small temperature difference and at relatively small 
throughput amounts of the warmer medium, with simple construction. 
This objective is achieved in accordance with the invention in that the 
heat conducting body surrounds a heating body traversed by the warmer 
medium and is configurated as a separating wall that separates the liquid 
to be heated which warms up at the heating body from the remaining 
contents of the inner space and that is provided, in the sense of the 
liquid to be heated which rises therein based on its warming-up, with an 
inlet opening at its lower end and an outlet opening at its upper end. 
With the aid of the heat conducting body, a relatively small proportion is 
delimited from the total volume of the liquid to be heated and is brought 
into immediate contact with the heating body. Consequently, this 
proportion of the liquid which is surrounded by the heat conducting body 
is intensely heated at the heating body, inasmuch as its mixing with the 
remainder of the liquid to be heated is prevented by the heat conducting 
body. As a result of the heating, the liquid to be heated rises upwardly 
so that a colder liquid can enter from below into the heat conducting 
cylinder. In this manner, a flow is created in the heat conducting body 
which results in that the warmed-up liquid emerges out of the upper part 
of the heat conducting body and becomes layered on the cooler fluid which 
is present in the lower part of the heat exchanger. The temperature of the 
warmer liquid renders it possible to economically utilize the same. It is 
withdrawn from the upper part of the heat exchanger without being able to 
mix with the cold liquid that is fed into the lower part of the container, 
in view of the relatively exactly configurated separating layer. 
According to a preferred embodiment of the invention, the outlet opening is 
configurated as a trottling location. It is prevented by it that a natural 
flow in the heat conducting body could occur with such vigor that the 
outlet temperature at the outlet opening would not be high enough for the 
purposes of use. By the selection of the trottling openings, the flow in 
the heat conducting body can be so determined that the temperature at the 
outlet opening can be considerably determined in the framework of the 
thermodynamic possibilities of heat exchange. 
Further details of the invention will become apparent from the following 
detailed description and the accompanying drawings, in which there is 
exemplarily illustrated a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A heat exchanger consists essentially of an outer jacket 1, a heat 
conducting body 2, and a heating body 3 which is constructed as a heat 
exchanger. The outer jacket 1 extends, with its longitudinal axis, 
substantially upright, on legs 15 which are connected to a lower outer 
bottom 16 of the outer jacket 1. In the lower bottom 16, there is provided 
an opening 17 the cross section of which is so dimensioned that the heat 
conducting body 2 with the heating body 3 can be introduced through the 
opening 17 into the interior 18 of the outer jacket 1. This opening 17 is 
fluidtightly closed by a bottom plate 12. The heating body 3 is connected 
to the bottom plate 12 so that the inlet 20 and the outlet 19 for the warm 
medium which flows through the heating body extend through the bottom 
plate 12. The heating body 3 is constructed as a helix the diameter of 
which approximately corresponds the inner diameter of the heat conducting 
body 2 which is configurated as a cylinder. Herein, the heating body 3 is 
so designed as to its dimensions that the convolutions do not touch the 
inner surface of the heat conducting body 2. In this manner, flow can 
still form in the liquid which fills the heat conducting body 2 between 
the helix and the inner surface of the heat conducting body 2. 
In the lower part of the outer jacket 1, there is provided an inflow 
opening 6 for cold liquid. It is located immediately upwardly of the 
rounding of the inner bottom 10, but it can also be provided in the lower 
part of the bottom 2 immediately next to the bottom plate 12. Inasmuch as 
the liquid to be heated should enter the inflow opening 21 of the heat 
conducting body 2 from all sides of the cross section, the concentric 
arrangement of the heat conducting body 2 relative to the outer jacket 1 
offers itself. 
The heat conducting body 2 is provided, at its upper end, with an exit 
opening 22 out of which the warmed-up liquid can emerge in a direction to 
the interior of the outer jacket 1. When the flow distribution within the 
heat conducting body 2 is uniform, the warmed-up liquid enters the 
interior 18 to all sides and becomes layered on the cold liquid which is 
present in the lower part of the outer jacket 1. At the highest point of a 
domeshaped upper bottom 11, there is provided an outflow opening 7 through 
which the warm liquid can be withdrawn from the interior 18. A thermometer 
9 indicates the temperature of the warm liquid. 
The heating medium, for instance, the heated-up cooling fluid of a 
circulation circuit which is not shown in detail, is introduced into the 
helix of the heating body 3 at the inlet 20 and conducted away again at 
the outlet 19. It flows through the helix and, in connection therewith, 
transmits its heat contents to the liquid to be heated which surrounds the 
heating body 3 within the heat-conducting body 2. Based on its warming up, 
the liquid present in the interior of the heat conducting body 2 rises in 
the heat-conducting body 2 and forms a natural flow which extends in the 
direction to the upper bottom 11. Herein, the liquid which has been 
already pre-heated at the lower part of the heating body 3 flows, at the 
upper part, through further convolutions of the heating body helix 3 so 
that it is progressively heated in correspondence with the heat made 
available by the warm medium and in dependence on the respective 
temperature level, with long dwell in the heat conducting body 2. The 
liquid which has been warmed up in this manner exits at the opening 22 
from the heat conducting body 2 and is discharged at all sides onto the 
cold liquid which is present in the lower part of the interior 18, so that 
the warmed-up liquid becomes layered on the cold liquid. Depending on the 
demand, the warmed-up liquid can be withdrawn from the outflow opening 7. 
The temperature is indicated by the thermometer 9. 
A controlling possibility for the temperature of a liquid to be heated is 
achieved with the aid of a throttling location 5. This is formed at the 
exit opening 22 of the heat conducting body 2, in that the latter is 
closed by a plate 4 except for the desired throttling location 5. By the 
proper selection of the throttling location 5, the warm liquid is hindered 
in its emergence from the heat conducting body 2 until it has reached the 
desired temperature. For the event that varying temperatures are to be 
made available at the outflow opening 7 of the heat exchanger, it is 
possible to so construct the throttling location 5 as to be variable. 
Advantageously, the throttling location 5 can be moreover constructed as 
riser tube, which enhances the uniform distribution of the liquid to be 
heated. This riser tube can moreover be arranged eccentrically with 
respect to the cylindrical heat conducting body 2 in order to prevent, in 
this manner, the possibility that the liquid which rises through the riser 
tube and which is being heated would be directly evacuated through the 
outflow opening 7. 
The heat conducting body 2 can be held in the interior 18 of the outer 
jacket 1 with the aid of supporting braces 13. These supporting braces 13 
are so constructed that they present as small an obstruction as possible 
to the liquid flow which forms in the interior of the heat exchanger. They 
serve as transportation security in order to prevent bending of the 
heating body 3 and of the heat conducting body during the transportation. 
In addition to the mounting of the heating body 3 on the bottom plate 12, 
it is advantageous to also support the same in the interior of the heat 
conducting body 2 with respect to the latter. In this manner, the helix is 
so secured in the heat conducting body 2 that it cannot suffer any damage 
even during transport of the heat exchanger. 
It is very important that the heat conducting body 2 be so small with 
respect to its volume that the heating body just fits into the same. In 
this manner, the volume of the heat conducting body 2 is maintained small 
so that the liquid which is present there and which is to be warmed up can 
be rapidly heated. As a result of this, there is created a vigorous upward 
flow which results in an advantageous heat exchange at the heating body 3. 
Should the medium provided for the heating of the liquid be unavailable in 
sufficient amounts or at the desired temperature, a pump can be provided 
to enhance the flow which develops in the heat conducting body 2, which 
pump takes care of the necessary circulation speed and thus contributes to 
improved heat transfer. In addition, it is possible to provide an electric 
heating device 8 in the interior 18 of the heat exchanger. This is 
switched on for the support of the entire system when an insufficient 
amount of heat is made available by the medium to be cooled. With its aid, 
it is possible, in an economical manner, to always have constant supply of 
heat available at the upper part of the heat exchanger. 
The heat conducting body 2 can consist of metallic or other materials. When 
the materials are metallic, heat transfer along the heat conducting body 2 
to the cooling liquid present outwardly of the heat conducting body 2 has 
to be taken into account. In contradistinction, other materials, such as 
synthetic plastic materials and ceramic materials, act insulatingly, so 
that a good warming-up of the liquid to be heated within the heat 
conducting body 2 can be anticipated even at a small temperature 
difference. Especially in these cases, it is important to so keep the heat 
contents within the heat conducting body 2 that natural flow of the liquid 
which is being heated can form within the heat conducting body 2. For this 
reason, it is proposed in these cases to make the heat conducting body 2 
of materials which constitute poor heat conductors. 
The function of the heat exchanger according to the invention is 
independent of the constructional arrangement of the bottom plate 12. The 
heat conducting body 2 with the heating body 3 extending in the same can 
now be also introduced into the outer jacket 1 in a different manner. For 
instance, it is to be contemplated that the heat conducting body 2 and the 
heating body 3 are introduced into outer jacket 1 from above. In this 
case, there is to be provided in the upper bottom a closing plate with 
which the heat conducting body 2 as well as the heating body 3 are 
connected.