Note: Descriptions are shown in the official language in which they were submitted.
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PHD 82-035 1 4.1.1983
Lid-shaped reflux condenser for cookers.
The invention relates to a lid-shaped reflux
condenser for cookers, in particular cooking pots.
Such a reflux condenser is known from DE-PS
36 158. It consists of a lid in which cooling ducts are
provided in which cooling ~ater circulates which is fed and
drained from a lid hinge. The water circulating through
the cooling ducts cools the lower surface of the lid so
that the rising vapours condense on said surface and fall
back into the boiling mass again in the form of droplets.
10 In this manner not only the escape of unpleasant or detri~
mental vapours is avoided but the possible escape of useful
components of the boiled mass is also prevented.
The known lid has for its disadvantage that it
continuously needs fresh cooling water and requires an
15 expensive construction of the connections for the cooling
duc-ts. Furthermore, sealing proble~s occur at the connec-
tions. Moreover the efficiency of the cooling by circulating
water is unsatisfactory.
It is the object of the invention to provide
20 a structurally simple and at the same time effective lid-
~ike reflux condenser for cookers.
~ccording to the invention this object is achieved
in that the reflux condenser comprises a latent hea-t ac-
cumula-tor.
So it is the object of the invention to cover
the conventional cooking pots with a ]atent heat accumula-
tor by which the cooking vapours are condensed at normal
pressure and are refluxed to the food again.
The accumulator preferably consists of a flat
30 (for example, dish shaped or discus-shaped)metal holder
which is filled with a heat-storage material. The metal
holder preferably comprises cavities or bulges for receiving
water vapour and for increasing the cooling area. It is
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PHD 82-035 2 l~ 1.1983
also possible to provide several metal holders which
have, for example, the shape of accumulator plates, one
on top of the other so as to ensure a sufficient conden-
sation even when larger quanti-ties of vapour are presented.
In this case the cavities are provided between at least
2 metal holders placed one on top of the other.
As heat-storage materials are to be considered
such materials which have a heat of fusion w}lich is as
great as possible and melt reproducibly at a temperature
between 25 and 95 C. In order to ensure a reproducible
crystallization without larger super-cooling small quanti-
ties of nucleating agen-t may also be added to the heat
storage material. For example, the following hydrates can
very readily be used as a heat storage material:
1. CaC12 . 6H2o + o.o57b by wei~ht BaC03 melting point: 29C
2. NaOOCCH3 . 3H20 melting point: 58C
g~ 3)2 2 melting points 89 C
The necessary quantity of heat-storage material
and hence the proportioning of the metal holders and ac-
cumulator plates, respectively, depend on the capacity andthe dimensions of the cooker in question as well as on the
planned duration of cooking which, for example, for vege-
tables is approximately 10 to 30 minutes. As an indication
may hold good that for a commercial 2 litre cooker 1 to
2 kg of NaOOCCH3 . 3 H20 are required. Generally speaking
the thickness of the accumulator plates filled with heat-
storage material should preferably be 0.5 to 2 cm.
The accumulator is automatically regencrated
again in that the thermal energy -taken up during the
condensation of the cooking vapour and consumed for fusing
the hea-t storage material is given off to the cooler
surroundings. The heat s-torage material solidifies again
and becomes automatically ready for a new cooking operation.
This comparatively slow regeneration process
can additionally undertake a very useful function in the
household. The hot plates which are ~ept at the fllsion
te~nperature of the heat storage material by -the melting
heat for quite a period of time can in fact be used as
37~i
PHD 82-035 3 4.1.1983
SUC}l as plate-warmers. The pla-tes are suitable both as
a plate-warmer stand and as a plate-warmer lid for pots
and dishes of nearly any shape.
AdvantaFes of the reflux condenser:
1. No water vapour load of the house and consequently
a saving of energy.
2. No smell load of the house; aromas remain in -the food.
3. Simul-taneous availability of plate-warmers without
additional expenditure of labour and energy.
4. Construction, maintenance and cleaning are as simple
as possible.
5. Can be used as such for most of the conventional cookers
and service pots.
A few embodiments of the invention are shown in
lS the drawing and will be described in detail hereinafter.
Figure 1 is a sectional vicw of a cooker having
a lid-like reflux condenser.
Figures 2 and 3 are perspective views, partly
brokon away of a lid-like reflux condenser, and
Figure 4 is a sectional view of a cooker having
the reflux condenser shown in Figures 2 and 3.
Figure 1 shows a cooking pot 1 which is filled
partly with water 2 and with food (not shown) which is
to be stewed or cookedO The cooking pot is covered with
an accumulator plate 3 which has a cylindrical continuous
aperture 4 in its center. A second accumulator plate 5
(without aper-ture) is present over the accumulator plate
3. The heat-storage material inside the accumulator plates
is shown shaded. The accumulator plates comprise several
handles 6 with stands. Between the edge of -the cooking
pot 1 and the lower accumulator plate 3 a rubber member
7 is presen-t which is connected to the accurnulator plate
3. The gaseous water vapour with odours formed during
cooking or stewing are indicated by broken-line-arrows;
the solid-line-arrows indicate liquid water condensate
with odours.
After termination of the cooking process the
lower accumulator plate 3 may remain on the cooking pot
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PHD 82-035 4 40l.1983
1 to keep the food warm, while the top plate 5 may serve
as a plate-warmer stand for a dish on the dining table.
Particularly suitable as a heat storage material
for -the condenser consisting of two circular plates is
CH3COONa . 3H20 (Fusion temperature = 58 C) since the tem-
perature at which latent heat is stored is suitable both
for -the condensation of the coolcing water and for the sub-
sequent keeping warm of ser-~ice dishes. Moreover, sodium
acetate has a comparatively high heat capacity of 2.79 kJ/
kg and a heat of fusion of 289 kJ/dm3 and is cheap and
unpoinonous.
A difficulty, however, is its strong tendency
to supercooling (about 20 to 40 C). Although this can be
3( 4)2 8~2o or SrC204 . H20 9 the method
is not reliable and for reasons not yet e~plained (ageing?,
conversion?) said nucleating action can fail partly or
entirely.
Other heat-storage materials such as CaC12 . 6H2o
or Na2HP04 . 12H20 which are also suitable for use in
reflux condensers also tend to supercooling.
Ln order to exclude said supcrcooling it is
advantageous to provide the accumulator plates 3 and 5,
as shown in Figure 4, with har~dles 6 of tube which are
open towards the inside of the accumulator plates. Said
tube handles 6 are filled with heat-storage material 8
which i9 in direct contact with the same heat-storage
material in the plates. The heat-storage material 8 is
shown dotted in Figurc 4 (so different frorn Figure I) to
indicate that different heat storage materials can be
used.
Since the handles 6 are laterally in the air
and do not contact the hot cooking vapour, they remain
comparatively cool. The heat storage material in the
handles is thus not melted when the plates are used and
the nucleation occurs without inhibition starting from
said solid residual substance in the handle tubes over
the whole accumulator plate.
Moreover the handles 6 serve for eas~er
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PHD 82_035 5 L~. 1.1983
handling. In order that they should not become too :hot
also after very intensive and long cooking, they should
be manufactured as much as possible from thin-walled tube
and thermally poorly conducting material, for example,
Cr/Ni steel.
For a better heat trans~er of vapour to the
pla-te walls and hence ~or the better condensation, the
vapour flowing through the hole in the lower plate is
reciprocated by guides 9 in the slot be-tween the two plates
(Figure L~; in Figure 3 the ~lowing vapour is indica-ted
by arrows).
For a better heat -transfer from the plate walls
in the heat storage material, heat guides 10 are provided
radially in the interior of the two plates and are in
good thermal contact with the plate walls (Figures 2 and 4).
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