NZ758244B2 - High-shrink, high-strength multilayer film - Google Patents
High-shrink, high-strength multilayer filmInfo
- Publication number
- NZ758244B2 NZ758244B2 NZ758118A NZ75811818A NZ758244B2 NZ 758244 B2 NZ758244 B2 NZ 758244B2 NZ 758118 A NZ758118 A NZ 758118A NZ 75811818 A NZ75811818 A NZ 75811818A NZ 758244 B2 NZ758244 B2 NZ 758244B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- impeller wheel
- product
- centrifugal pump
- temperature
- rotational speed
- Prior art date
Links
- 235000021056 liquid food Nutrition 0.000 claims description 95
- 230000001105 regulatory Effects 0.000 claims description 58
- 239000002826 coolant Substances 0.000 claims description 53
- 238000001816 cooling Methods 0.000 claims description 28
- 230000001965 increased Effects 0.000 claims description 19
- 230000001276 controlling effect Effects 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000001704 evaporation Methods 0.000 claims description 6
- 230000001419 dependent Effects 0.000 claims description 5
- 235000013305 food Nutrition 0.000 claims description 5
- 102000004169 proteins and genes Human genes 0.000 claims description 4
- 108090000623 proteins and genes Proteins 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- 238000000034 method Methods 0.000 claims description 2
- 230000000977 initiatory Effects 0.000 abstract description 2
- QVFWZNCVPCJQOP-UHFFFAOYSA-N Chloralodol Chemical compound CC(O)(C)CC(C)OC(O)C(Cl)(Cl)Cl QVFWZNCVPCJQOP-UHFFFAOYSA-N 0.000 abstract 1
- 239000000047 product Substances 0.000 description 231
- 239000007788 liquid Substances 0.000 description 9
- 238000010586 diagram Methods 0.000 description 7
- 230000035515 penetration Effects 0.000 description 7
- 230000003068 static Effects 0.000 description 6
- 238000006073 displacement reaction Methods 0.000 description 5
- 238000005553 drilling Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000006071 cream Substances 0.000 description 3
- 230000002708 enhancing Effects 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000010327 methods by industry Methods 0.000 description 3
- 235000018102 proteins Nutrition 0.000 description 3
- 235000008452 baby food Nutrition 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000012141 concentrate Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000005755 formation reaction Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 210000004080 Milk Anatomy 0.000 description 1
- 229910017436 S2 Can Inorganic materials 0.000 description 1
- 206010057040 Temperature intolerance Diseases 0.000 description 1
- 102000007544 Whey Proteins Human genes 0.000 description 1
- 108010046377 Whey Proteins Proteins 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 230000001364 causal effect Effects 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 235000013365 dairy product Nutrition 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 235000013336 milk Nutrition 0.000 description 1
- 239000008267 milk Substances 0.000 description 1
- 235000008935 nutritious Nutrition 0.000 description 1
- 230000003134 recirculating Effects 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 230000000246 remedial Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
- 235000021119 whey protein Nutrition 0.000 description 1
Abstract
emergency lighting system comprising a control node and plurality of emergency luminaires, wherein each the plurality of emergency luminaires receives control signals directly from the control node across a LoRa wireless communications network, the control node being configured to transmit test initiation signals to each emergency luminaire. nitiation signals to each emergency luminaire.
Description
Method and system for controlling and/or regulating the treatment of heat-sensitive
liquid food products
TECHNICAL FIELD
The invention relates to a method and a system for controlling and/or regulating the treatment
of heat-sensitive liquid food products such as whey protein concentrate, baby food, liquid baby
food concentrates, nutritious beverages or dairy milk, wherein steam directly heats the liquid
food product to establish a germ-free state in an infuser container, wherein water is removed
from the liquid food product by flash evaporation at a low pressure in an amount which
corresponds to that of the previously supplied steam, wherein the liquid food product is
delivered by means of a centrifugal pump between heating and flash evaporation, wherein the
liquid food product undergoes cooling in at least one section of this flow path by each of the
associated walls bordering this flow path starting upon entry into a base region of the infuser
container and at most until entering the centrifugal pump. Moreover, the invention relates to a
centrifugal pump for such a system.
Heat-sensitive liquid food products of the aforementioned type contain a relatively large amount
of protein, a large amount of dry mass and little water, and they may possess a low, average or
high viscosity. The term “heat sensitivity” should be understood in the following to mean that
these food products, preferably at temperatures above 100°C, tend to collect up to baking on,
i.e., to form a coating on critical walls under these conditions, i.e., the walls of the infuser
container, the centrifugal pump conveying them, and on the walls of the flow path connecting
the infuser container with the centrifugal pump. This coating formation is also termed product
fouling. Product fouling reduces the service life, or respectively the operating time of the infuser
container and in particular the centrifugal pump between two cleaning cycles. The baking on
of the heated liquid food product on the critical walls is counteracted by cooling these walls.
PRIOR ART
Particularly critical regions of a heating system with an infuser container and a delivery
apparatus designed in whatever manner and arranged downstream from the infuser container,
are the bottom region of the infuser container that tapers downward to an outlet opening, and
the delivery apparatus. The delivery apparatus can be a rotating displacement pump known per
se such as a gear pump, vane pump, impeller pump or rotary pump. The rotating displacement
pump is generally arranged directly at the outlet opening because unproblematic regulation of
a desired minimum fill level in the infuser container is possible due to the specific rotary-speed-
dependent volumetric flow of this pump type. The arrangement of a gear pump is known from
EP 0 794 706 B1, wherein its housing has a cooling system, and the housing directly adjoins
the outlet opening of the infuser container. Depending on the design, a gear pump possesses an
ability to clean itself because the gears mesh tightly with each other and scrape along the
associated housing walls and thereby prevent gradually accumulating formation of a coating
(product fouling).
It has, however, already been proposed to use a delivery apparatus designed as a centrifugal
pump, wherein this is generally arranged above a drainpipe terminating at the outlet opening
and extending downward, and accordingly at a distance from the infuser container. Such a
distance that represents an additional liquid reservoir in the drainpipe between the outlet
opening and the entrance into the centrifugal pump is necessary in order to achieve sufficiently
reliable fill level regulation in the infuser container. A fluctuating fill level in the bottom region
of the infuser container leads to an undesirable and undefined dwell time at that location; a
lowering of the fill level to the entrance of the centrifugal pump can cause vapor to be sucked
into the centrifugal pump and hence can cause undesired cavitation. Undefined dwell times and
cavitation cause a reduction in the quality of the liquid food product.
In A1, the system for heat-treating heat-sensitive liquid foods known from
EP 0 794 706 B1 is modified in that, with an otherwise unchanged configuration of the
individual assemblies of the system, the cooling jacket surrounding the bottom of the infuser
container that serves to cool this bottom extends underneath the pump and, according to an
advantageous embodiment, into the pump housing. The pump is a displacement pump,
preferably a gear pump or piston pump. However, a centrifugal pump is also claimed without
indicating how this centrifugal pump is designed. It can therefore be assumed that a
conventional and hydraulically optimized centrifugal pump is provided whose basic design is
known to the expert.
A centrifugal pump for unproblematic liquid food products such as water has a basic design
that is sufficiently known. It is designed and configured such that it possesses maximum
hydraulic efficiency, i.e., it achieves a maximum product of the volumetric flow times the
delivery rate with a given drive energy. In a pump housing generally consisting of at least two
housing parts, an impeller wheel with blades is arranged on a shaft. Inside the pump housing, a
guide apparatus in the form of, for example, a spiral housing or a blade-free annular space
adjoins the outside of a ring-shaped, surrounding impeller wheel exit cross-section. Located on
the suction-side housing part, a housing cover, is an inlet coaxial to the impeller wheel axis said
inlet being generally designed as a so-called suction port, and an outlet that preferably
discharges tangentially in the perimeter and is generally designed as a so-called pressure port.
An impeller wheel pressure side forms a so-called rear wheel side chamber with the housing
part, a housing rear wall, facing away from the suction side which generally has a short axial
extension to achieve good hydraulic efficiency by the centrifugal pump. This axial or gap-wide
extension is generally dimensioned short enough to ensure the mechanical functioning of the
centrifugal pump given appropriate production tolerances. In the same way, the impeller wheel
front side, and in this case this is the front end-face blade edges of an open impeller wheel, is
adapted to the contour of the housing cover with a very narrow gap. To reduce an axial force
that results from the pressures acting on both sides of the impeller wheel, a plurality of pressure
compensation holes with a relatively small diameter are arranged in the hub region of the
impeller wheel and distributed over its circumference.
With heat-sensitive liquid food products of the aforementioned type, the primary goal is for
there to be a minimum tendency to deposit on the walls of the centrifugal pump while the
products are being delivered by a centrifugal pump. For example, when directly heating very
heat-sensitive liquid food products in an infuser container and then discharging the heated liquid
food products out of the infuser container by means of a downstream centrifugal pump of the
usual design, i.e., hydraulically optimized design, it was revealed that this centrifugal pump
becomes clogged within a very short time, that is, clogged within seconds to a few minutes, by
product fouling, and therefore stops operating. Particularly critical regions are the intake region
of the impeller wheel because undissolved gases and, in particular, non-condensed steam
enhance product fouling here, and the narrow, gap-wide rear wheel side chamber.
A satisfactory solution remains unknown for the specific design of a centrifugal pump in a
system for treating heat-sensitive liquid food products in which the latter undergo direct heating
by means of culinary steam.
In known systems in which a centrifugal pump is connected by a drainpipe to the outlet opening
of the infuser container, fill level regulation is required in the region of the outlet opening and
the drainpipe that is used to control and/or regulate the operating phase of the system. With this
type of control and/or regulation, it was revealed that fill level fluctuations in the drainpipe
unavoidably occur and cannot be prevented. These fill level fluctuations cause dwell time
fluctuations in the infuser container and the drainpipe connecting thereto that comprise 15 to
% of the dwell time in this region of the liquid food product to be heated directly. If the fill
level is too high, then the exposure time of the liquid food product to the steam is insufficient
with this necessarily reduced drop height, the desired product temperature setpoint is not
reached, and vapor bubbles inclusions remain in the insufficiently heated liquid food product.
If a fill level is too low, on the one hand the product temperature setpoint is exceeded, and on
the other hand the danger exists of vapor being sucked into the centrifugal pump which can
produce cavitation there with harmful consequences to the liquid food product and the
centrifugal pump.
Vapor bubble inclusions from fluctuations in the fill level and hence dwell time lead to
increased product fouling, in particular on the blades of the centrifugal pump. Product fouling
generally causes a shortening of the operating phase of the system, wherein the duration of the
operating phase is also termed the service life of the system. The service life is equivalent with
the length of time between two cleaning cycles of the system for eliminating product fouling.
Lengthening the service life is, however, generally desirable, not just because of a lengthening
of the operating phase for the aforementioned reasons; a lengthening of the service life that
results from less quantitative product fouling over time also yields greater product quality
because protein and fat in the liquid food product are less damaged, or respectively influenced.
The cooling of the centrifugal pump also has a significant influence on the service life. As
presented above, product fouling occurs at this location in particular in the intake region of the
impeller wheel because undissolved gases and in particular non-condensed steam enhance
product fouling at this location, and in the narrow, gap-wide rear wheel side chamber. Cooling
these regions causes a lengthening of the service life but cannot prevent product fouling on the
blades of the centrifugal pump; instead, it can only inhibit the growth of product fouling. This
product fouling necessarily yields a reduction of the throughput of the centrifugal pump because
passage cross-sections constrict, and friction resistances in the regions of the flow close to the
wall increase, which further enhances the fill level fluctuations and hence dwell time
fluctuations in the relevant parts of the system which are already problematic.
It is the object of the present invention to create a method for controlling and/or regulating the
treatment of heat-sensitive liquid food products, a system for carrying out the method, as well
as a centrifugal pump for this system by means of which an improvement in fill level regulation
in the infuser container and hence a constant dwell time of the liquid food product to be heated
is achieved in the event of growing product fouling in the centrifugal pump. An additional
object consists of modifying a preferably commercially available centrifugal pump such that it
inhibits the growth of product fouling therein and contributes to the lengthening of the service
life.
SUMMARY OF THE INVENTION
This object is achieved by a method with the characteristics of claim 1. Advantageous
embodiments of the method according to the invention are the subject of the associated
dependent claims. A system for performing the method is the subject of independent claim 10.
Advantageous embodiments of the system according to the invention are the subject of the
associated dependent claims. A centrifugal pump for a system according to claim 10 is the
subject of claim 13. Advantageous embodiments of the centrifugal pump according to the
invention are the subject of the associated dependent claims.
In terms of process engineering, the invention is based on a method for controlling and/or
regulating the treatment of heat-sensitive liquid food products, wherein steam directly heats the
liquid food product to establish a germ-free state in an infuser container, wherein water is
removed from the liquid food product by flash evaporation at a low pressure in an amount which
corresponds to that of the previously supplied steam. In the method, the liquid food product is
delivered by means of a centrifugal pump between heating and flash evaporation, and the liquid
food product undergoes cooling in at least one section of this flow path by each of the associated
walls bordering this flow path starting upon entry into a base region of the infuser container and
at most until entering the centrifugal pump.
The underlying object of the invention is achieved when, in the method of the generic type
during the treatment known per se of the liquid food product to be directly heated, on the one
hand a centrifugal pump is used with an impeller wheel rotatably accommodated in a pump
chamber, wherein the centrifugal pump is designed such that part of a volumetric flow of the
liquid food product, delivered by the impeller wheel, serves to rinse the impeller wheel itself
and the regions of the pump chamber as specified that are directly adjacent to the impeller
wheel.
On the other hand, the following treatment steps (a) to (e) according to the invention are
provided:
(a) A product temperature detected downstream after the centrifugal pump of an infuser-
heated liquid food product is regulated by steam at a steam temperature that is supplied
to a head region of the infuser container to a product-specific product temperature
setpoint to be achieved as specified. In so doing, a drop in the product temperature
causes a rise, and a rise in the product temperature causes a drop, in the steam
temperature in a manner known per se.
(b) In an initial phase of the treatment of the liquid food product, the centrifugal pump is
operated at an initial rotational speed lying below a rated rotational speed of the
centrifugal pump by a predetermined amount. This initial rotational speed depends on
the liquid food product and/or on the design of the centrifugal pump, i.e., on the extent
of the specified rinsing, or respectively the rinsing volumetric flows in the pump
chamber and in the impeller wheel itself.
(c) A reduction of the volumetric flow of the centrifugal pump is then counteracted by an
increase in the initial rotational speed when said reduction occurs at the same time as a
drop in the product temperature.
(d) The initial rotational speed is increased depending on a drop of the product temperature,
and/or a rise of the steam temperature. In so doing, the respective extent of increasing
the initial rotational speed results from the regulatory necessity of keeping at least the
product temperature constant during the respective application. The respective initial
rotational speed is generally determined by empirical values obtained experimentally
beforehand for the respective liquid food product.
(e) Steps (c) and (d) are repeatedly executed until the specified product temperature setpoint
(T2(S)) to be achieved, and/or the steam temperature (T1) needed to achieve the product
temperature set point (T2(S)) at the start of treatment, consistently occur/occurs.
The inventive basic concept is founded on the insight that changes in the fill level are the result
of disturbance variables of which product fouling on the blades of the centrifugal pump is an
essential one. This product fouling necessarily reduces the volumetric flow in the centrifugal
pump and, without counteracting measures, such as without increasing the drive performance
of the centrifugal pump for the purpose of retaining the desired volumetric flow, leads to an
increase in the fill level in the infuser container. Maintaining a specified volumetric flow under
these conditions requires an increase in the rotational speed and thus the noted increase in the
drive performance. This necessary increase in the fill level occurs indirectly through a drop in
the product temperature and as a consequence, indirectly through a rise in temperature in the
infuser container. In summary, the method according to the invention exploits the following
causal relationships:
• The gradually growing product fouling on the walls between an outlet opening of the
infuser container and an exit from the centrifugal pump leads to a reduction in the
volumetric flow passing through this region.
• If the system is supposed to be operated at a constant volumetric flow, the product
fouling in this region causes an increase in the drive performance due to the required
increase in rotational speed or, if the required increase in rotational speed does not occur,
causes a reduction in the volumetric flow.
• The reduction of the volumetric flow under these conditions leads to an increase in the
fill level in the infuser container and thus to a temperature drop in the infuser-heated
liquid food product because the steam in the available fall time, or respectively exposure
time cannot, as before, transfer its enthalpy to the liquid food product to be heated.
• As a consequence of the temperature drop in the infuser-heated liquid food product,
there is a rise in the steam temperature and hence, for reasons of control engineering,
necessarily a temperature rise in the infuser container.
Accordingly it is possible to not just use the change in the fill level in the infuser container itself
which is costly to detect, but rather to use the effects of these fill level changes, which are much
easier to detect, by themselves or in addition to regulate the fill level according to the invention,
and hence to control and/or to regulate the treatment of heat-sensitive liquid food products in
the relevant system.
The invention provides that the increase in the initial rotational speed occurs steadily, wherein
according to another proposal, an increase thereof is carried out such that the gradient of the
steady increase in the initial rotational speed results from the regulatory requirements, i.e., from
the given control requirements in the respective specific application, and is adjusted depending
on the drop in temperature of the product temperature, and/or the rise in temperature of the
steam temperature, and/or the product-specific requirements.
Alternatively to steadily increasing the initial rotational speed, the invention proposes a
stepwise increase, wherein the increase is carried out in at least one discrete step with a
rotational speed differential that results from the regulatory requirements, i.e., from the given
control requirements in the respective specific application. In this regard, another proposal
provides adjusting the rotational speed differential, depending on the drop in temperature of the
product temperature and/or the rise in temperature of the steam temperature, and/or product-
specific requirements.
The invention proposes another process engineering embodiment according to which the initial
rotational speed and/or the product temperature setpoint are, or respectively is set depending on
default parameters that are characteristic of the liquid food product, wherein “default
parameters” are understood to be the physical variables such as density, viscosity and thermal
conductivity of the liquid food product, and/or its composition such as the portion of fat and
protein. The proposed method can therefore be adapted to the special needs of the liquid food
product to be heated.
Since the method according to the invention cannot be operated dissociated from the physical
boundary conditions to which it is subjected, another process engineering embodiment
moreover provides that the initial rotational speed and/or the product temperature setpoint are,
or respectively is adjusted depending on the physical boundary conditions to which the method
is subjected, wherein the “physical boundary conditions” of the method are understood to be
process-related default parameters of the method such as pressure and temperature.
Another embodiment of the method provides that the initial rotational speed, and/or the product
temperature setpoint, and/or the rotational speed differential, and/or alternatively to the
rotational speed differential, the gradient of the steady increase in the initial rotational speed
are, or respectively is adjusted by means of a calibration function tested and saved before or
while starting the method. The control and/or regulation according to the invention of the
treatment of the liquid food product in line with obtained product-specific empirical values can
thereby be supported in a time-saving and cost-saving manner and operated with high quality
for the liquid food product.
The method according to the invention can also be used for an infuser container in which the
liquid food product is supplied annularly, and is impinged on from the inside by internal steam
which is the subject of the main claim, and from the outside by external steam. In this case, the
supply of the external steam is adjusted depending on a required supply pressure for the internal
steam in the head region of the infuser container, and by differential pressure regulation.
A system according to the invention for controlling and/or regulating the treatment of heat-
sensitive liquid food products is based in a manner known per se on an infuser container in the
headspace of which a steam line for steam and a product inlet terminate, a vacuum chamber
fluidically connected to the infuser container by a connecting line, a centrifugal pump arranged
in the connection line, an outlet opening arranged in a bottom of the infuser container, and a
drainpipe connecting to the outlet opening and terminating in the centrifugal pump. A container-
bottom-side coolant chamber, and furthermore a pump-housing-side coolant chamber, and/or a
drainpipe-side coolant chamber are provided for cooling.
The underlying object of the invention is achieved by a system that is characterized by the
following features according to the invention which go beyond the generic features:
• a centrifugal pump is provided that has an impeller wheel which is rotatably
accommodated in a pump chamber in a manner known per se and that is designed
according to the invention such that part of a volumetric flow of the liquid food product,
delivered by the impeller wheel, serves to rinse the impeller wheel itself and the regions
of the pump chamber as specified that are directly adjacent to the impeller wheel;
• downstream directly after the centrifugal pump, a temperature regulating apparatus is
provided in the connecting line which is configured to regulate a product temperature
and interacts with a control valve arranged in the steam line;
• downstream after the control valve, a temperature measuring apparatus is provided in
the steam line for a steam temperature;
• the centrifugal pump is assigned a rotational speed regulating apparatus for regulating a
rotational speed of the centrifugal pump;
• a control and regulating apparatus is provided that adjusts a product-specific initial
rotational speed of the centrifugal pump and the steam temperature, and executes an
increase in the initial rotational speed in conjunction with the temperature regulating
apparatus, the control valve, the temperature measuring apparatus and the rotational
speed regulating apparatus.
The seamless cooling of the heated liquid food product is achieved as provided in an initial
proposal in this regard when the container-bottom-side coolant chamber, the drainpipe-side
coolant chamber, and the pump-housing-side coolant chamber undergo cooling separately from
each other. With regard to cooling, a second proposal that reduces the cooling effort provides
that at least two coolant chambers are series-connected with each other and undergo cooling in
a countercurrent to an infuser-heated food product.
A centrifugal pump according to the invention that is suitable for a system to control and/or
regulate the treatment of heat-sensitive liquid food products is based on a centrifugal pump
which is known per se with an inlet, an outlet, a pump housing that is formed by at least a
housing cover and a housing rear wall. It is also based on the pump chamber formed in the
pump housing and in fluidic connection with the inlet and the outlet, the impeller wheel that is
rotatably accommodated in the pump chamber and is designed open toward the housing cover
and closed to the housing rear wall by a rear side of the impeller wheel, a front impeller wheel
gap provided between the housing cover and the impeller wheel, and a rear impeller wheel gap
provided between the housing rear wall and the impeller wheel.
The inventive basic idea consists of rinsing the impeller wheel itself and its adjacent critical
regions up to the immediate pump-housing-side edge of the impeller wheel front side and the
impeller wheel rear side with the infuser-heated and hence treated liquid food product to be
delivered, and thereby inhibiting product fouling at that location because said pump-housing-
side edges are, or respectively can be simultaneously cooled in a manner known per se during
the rinsing according to the invention.
The treated liquid food product accordingly serves to rinse the pump housing and the impeller
wheel itself as specified with part of its volumetric flow delivered in the impeller wheel. In so
doing, the volumetric flows of the specified rinsing exceed by several times the necessary
compensating flows in the pump housing that result from a normal hydraulically optimized
design of the centrifugal pump. The tendency of liquid food product to bake onto the walls of
the centrifugal pump is reduced by the cooling. This is accomplished by a specified sacrifice of
optimum hydraulic efficiency. In the centrifugal pump according to the invention, a volumetric
flow is delivered in the impeller wheel which is increased by the sum of all more-or-less
recirculating rinsing volumetric flows than the volumetric flow drawn by the suction port. The
rinsing volumetric flows generated during the specified rinsing guide volumes from the core of
the blade channels to the cooled walls of the pump housing and from there back into the impeller
wheel, wherein the cooling action condenses non-condensed steam and thereby reduces the
tendency of product fouling.
The above-described interrelationships reveal that a centrifugal pump which is rinsed according
to the invention with the liquid food product that it delivers possesses an impeller wheel whose
hydraulic output relative to the impeller wheel must be greater than the hydraulic output of the
centrifugal pump that actually ultimately occurs at the pressure port. If a hydraulically-
optimized centrifugal pump is chosen to realize a rinsed centrifugal pump of the relevant kind,
then its rated output must be chosen to be correspondingly higher by the aforementioned
difference in output. Given the same rated output, an outer impeller wheel diameter of the rinsed
centrifugal pump must therefore be larger than one for a hydraulically optimized centrifugal
pump.
The specific solution for implementing the aforementioned inventive basic ideas consists of
designing the impeller wheel in a manner known per se as an impeller wheel which is designed
open toward the housing cover and closed to the housing rear wall by a rear side of the impeller
wheel. Moreover, the front impeller wheel gap is increased up to several times in comparison
to a minimum front impeller wheel gap that ensures the mechanical functioning of the
centrifugal pump by reducing the width of the impeller wheel. This increase is configured such
that the front impeller wheel gap undergoes a maximum increase at an outer diameter of the
impeller wheel that decreases steadily to the minimum front impeller wheel gap into the region
of the entrance into the blade channels of the impeller wheel, and the reduction of the width of
the impeller wheel at the outer diameter of the impeller wheel is 40 to 50% of the width of a
hydraulically optimized impeller wheel. In the region of the front impeller wheel gap, a second
rinsing flow forms that extends out of the region of the outlet into the region of the inlet of the
impeller wheel. Due to the enlargement of the front impeller wheel gap, the flow is significantly
increased around the front edge of the blades of the open impeller wheel that exists there even
when the impeller wheel gap is narrow, driven by the difference in pressure between the
pressure side and suction side of the blade which generates a third rinsing flow as specified.
Each blade channel of the impeller wheel between two adjacent blades is fluidically connected
to the rear impeller wheel gap in the region of its adjacent impeller wheel rear side by at least
one rinsing hole that penetrates the impeller wheel rear side. The position, designed shape and
dimensions of the rinsing hole are features by means of which an associated first rinsing flow
is established with respect to its radial penetration depth, its shape and quantitative intensity.
When a rinsing hole is arranged in each blade channel, it is useful with regard to flow and
production if all of these rinsing holes are arranged on a circle of holes with corresponding
spacing. With respect to the positioning of the rinsing hole, it has proven to be advantageous
when the geometric location of the respective penetration site of the rinsing hole in the impeller
wheel rear side that also determines the hole circle diameter is determined as follows:
• approximately through the middle of the blade channel relative to the distance of the
blades at the penetration site, and
• approximately through the middle of a maximum flow thread length of the blade
channel between its entrance and exit.
With regard to the dimension of the rear impeller wheel gap, it has proven to be useful when
the access to a minimum rear, radially-oriented impeller wheel gap that ensures the mechanical
functioning of the centrifugal pump and that begins at the outer diameter of the impeller wheel
is increased by up to 5 mm by reducing the outer diameter of the impeller wheel. Moreover, the
rear impeller wheel gap is enlarged according to the invention in that the impeller wheel rear
side undergoes an annular drilling out in the region between the rinsing hole and a hub of the
impeller wheel with an axial depth of up to 2 mm.
The generation of the desired and necessary first and second rinsing flow is only enabled by the
enlargement of this impeller wheel gap. The respective width of the front and rear impeller
wheel gap can be dimensioned depending on the specific properties of the liquid food product.
The rinsing hole in the most general case comprises passages of any shape, i.e., a circular shape
that is easy to produce is not essential. The rinsing hole is either designed circular with a hole
diameter, or it has a shape that deviates from the circular shape with a hydraulic diameter that
is essential for this shape. It has proven to be useful if the hole diameter or the hydraulic
diameter is 30 to 50%, and in this region preferably 40 to 50%, of the spacing of the blades at
the penetration site.
SHORT DESCRIPTION OF THE DRAWINGS
A more detailed representation of the invention is evident from the following description and
the attached figures in the drawings as well as from the claims. Whereas the invention is realized
in a wide range of designs of a method of the type described above and a wide range of
embodiments of a system for performing the method, a preferred exemplary embodiment of a
system according to the invention, and its control and regulation according to the invention, as
well as a centrifugal pump according to the invention for such a system, will be described below
with reference to the drawing.
In the figures:
Fig. 1 shows a schematic representation of a system for treating heat-sensitive liquid
food products according to the prior art;
Fig. 2 shows a schematic representation of a section of a system for controlling and/or
regulating the treatment of heat-sensitive liquid food products according to the
invention in the region of an infuser container for directly heating the liquid food
product in direct connection with a centrifugal pump;
Fig. 3 also shows a schematic representation of the section from the system according
to Fig. 2 with indications of the control and/or regulation of the treatment of
heat-sensitive liquid food products according to the invention;
Fig. 4 shows a schematic representation of a diagram that shows the interaction of the
respective pump characteristic of the centrifugal pump with the pipeline
characteristic of the systems according to Fig. 3 and 4 in the context of the
control and/or regulation according to the invention;
Fig. 5, 6 show a schematic representation of a diagram that qualitatively depicts the
characteristics of the product temperature and steam temperature in the context
of controlling and regulating according to the invention, and on the basis of the
interaction of characteristics according to Fig. 4;
Fig. 7 shows a schematic representation of a diagram that qualitatively depicts the
power consumption of the first delivery apparatus in the context of controlling
and regulating according to the invention, and on the basis of the interaction of
characteristics according to Fig. 4;
Fig. 8 shows a screen section from a graphic measuring record for the method
according to the invention applied to a special liquid food product, and
Fig. 9 shows the side view of a meridian section of the impeller of the centrifugal pump
according to the invention according to Fig. 2 with the approximate indication
of a first, second and third rinsing flow.
A system 100 known from the prior art according to Fig. 1 (such as A1)
contains an infuser container 10 as described for example in A1 and that has
a product inlet 20 in its headspace through which a liquid food product P that is to be heat-
treated is supplied to this infuser container 10 centrally and annularly. The liquid food product
P supplied in this manner is also supplied with steam D for direct heating through the headspace
of the infuser container 10, namely a first steam D1 radially from the outside through an external
steam inlet 22, and a second steam D2 radially from the inside through an internal steam inlet
The infuser container 10 is bordered at its bottom tapering downward toward an outlet opening
by a container-bottom-side coolant chamber 10.4. The outlet opening of the infuser container
is connected by a drainpipe 12 that is surrounded by a drainpipe-side coolant chamber 12.1
to a first delivery apparatus 14 that is designed as a displacement pump, preferably as a rotating
displacement pump, and is arranged in a connecting line 30 leading from the first delivery
apparatus 14 to an entrance into a vacuum chamber 16. The first delivery apparatus 14 possesses
a pump-housing-side coolant chamber 14.1.
The pump-housing-side coolant chamber 14.1 is supplied coolant to cool K it through a pump-
side coolant entrance 26 which then flows through the drainpipe-side coolant chamber 12.1 to
cool K it, and finally enters the container-bottom-side coolant chamber 10.4 to cool K the
bottom of the infuser container 10. The coolant is discharged through an infuser-side coolant
exit 28.
The delivery apparatus 14 delivers an infusion-heated liquid food product P’ from the infuser
container 10 to the vacuum chamber 16. The vacuum chamber 16 is designed to remove the
amount of water W from the infusion-heated liquid food product P’ that cools from the
reduction in pressure as so-called flash steam that is supplied in the form of steam D, in the
present case consisting of the first steam D1 and the second steam D2, to the infuser container
. The water W is withdrawn through a vapor exit 32 preferably arranged in the top region of
the vacuum chamber 16. A liquid food product P* treated in this manner leaves the vacuum
chamber 16 through a drain line 34 preferably arranged in the bottom region in a tapering
bottom along the way through a second delivery apparatus 18 that is preferably designed as a
centrifugal pump.
Fig. 2 shows a schematic representation of a section of a system 100 for controlling and/or
regulating the treatment of heat-sensitive liquid food products P according to the invention in
the region of an infuser container 10 for directly heating the liquid food product P. The infuser
container 10 selected as an example is of the same design and is supplied in the same manner
with steam D, or respectively D1, D2 and the liquid food product P as is the case according to
Fig. 1. It has a preferably cylindrical container jacket 10.1 and a container bottom 10.2 adjacent
thereto and tapering downward into an outlet opening 10.3, wherein the container bottom 10.2
is bordered by the container-bottom-side coolant chamber 10.4. The outlet opening 10.3 is
connected by the drainpipe 12 surrounded by the drainpipe-side coolant chamber 12.1 to the
first delivery apparatus 14 designed as a centrifugal pump. The pump-housing-side coolant
chamber 14.1 extends into a pump housing 14.2 of the centrifugal pump 14 that rotatably
accommodates an impeller wheel 14.3.
The coolant chambers 10.4, 12.1 and 14.1 are preferably series-connected to each other and
undergo cooling K in a countercurrent to an infuser-heated liquid food product P’ that leaves
the centrifugal pump 14 through the connecting line 30 and flows toward the vacuum chamber
16. A first cooling K1 comprises the pump-housing-side coolant chamber 14.1 on the way from
a first coolant entrance 14.1.1 to a first coolant exit 14.1.2. A second cooling K2 concerns the
drainpipe-side coolant chamber 12.1 on the way from a second coolant entrance 12.1.1 to a
second coolant exit 12.1.2. A third cooling K3 comprises the container-bottom-side coolant
chamber 10.4 on the way from a third coolant entrance 10.4.1 to a third coolant exit 10.4.2.
The internal steam inlet 24 for supplying steam D or internal steam D2 to the infuser container
is connected to a steam line 24.1. Downstream directly after the centrifugal pump 14 (Fig.
3), there is a temperature regulating apparatus 44 in the connecting line 30 that is configured to
regulate (“C”) a product temperature T2 or a product temperature setpoint T2(S) with the
additional capability of displaying (“I”) a temperature (“T”) (→ TIC), and that interacts through
a control and regulating apparatus 50 with a control valve 46 arranged in the steam line 24.1.
Downstream after the control valve 46, a temperature measuring apparatus 40 is provided in
the steam line 24.1 for a steam temperature T1 or a steam temperature setpoint T1(S) with the
capability of displaying (“I”) a temperature (“T”) and initiating an error message (“A”) in this
regard (→ TIA). The centrifugal pump 14 is assigned a rotational speed regulating apparatus
42 for regulating (“C”) a rotational speed n (“S”) of the centrifugal pump 14 (→SC). Signals
for controlling and/or regulating are transmitted through signal lines, of which one signal line
48 is shown as an example.
A liquid level N of an infuser-heated liquid food product P’ is drawn as an example in the
infuser container 10, wherein a change in a liquid level ∆h that can also extend into the drainpipe
12 is to be minimized by the method according to the invention. An available drop height h for
the liquid food product P to be heated that should be kept as constant as possible according to
the invention necessarily results from the position of the liquid level N, or respectively the
changes in the liquid level ∆h. The centrifugal pump 14 generates a delivery pressure of the
centrifugal pump p(14) at its pressure-side exit in the connecting line 30.
The control and regulating apparatus 50 has connections a, b, c, d, by means of which they are
connected to the associated connections a, b, c, d of the temperature measuring apparatus 40,
the rotational speed regulating apparatus 42 and the temperature regulating apparatus 44 and
the control valve 46 for signaling and controlling. The control and regulating apparatus 50, in
cooperation with the temperature measuring apparatus, the rotational speed regulating
apparatus and the temperature regulating apparatus 40, 42, 44 and the control valve 46, sets a
product-specific initial rotational speed n(o) of the centrifugal pump 14 and the steam
temperature T1, and executes an increase in the rotational speed n starting from the initial
rotational speed n(o).
The qualitative diagrams in Fig. 4 to 7 in conjunction with Fig. 3 serve to explain the method
according to the invention for controlling and/or regulating the treatment of heat-sensitive liquid
food products P, wherein this can be accomplished with a system 100 according to the invention
designed as an example according to Fig. 2. The basic method for directly heating a liquid food
product P by means of steam has already been sufficiently described by way of introduction.
The solution to the object, namely to achieve an improvement of fill-level regulation and hence
a constant dwell time of the liquid food product P to be heated in the event of increasing product
fouling F in the centrifugal pump 14, will be described below.
Operating phase
In a trouble-free operating phase of the system 100 (see Fig. 3), the product temperature T2
of the infuser-heated liquid food product P’ detected downstream after the centrifugal pump 14
is regulated to the product-specific product temperature setpoint T2(S) to be achieved as
specified. This is accomplished by the regulated supply of steam D, or respectively D1, D2 at
steam temperature T1 which in this case corresponds to the steam temperature setpoint T1(S).
The supply occurs in the head region of the infuser container 10 by means of the temperature
regulating apparatus 44 in collaboration with the control and regulating apparatus 50 and the
control valve 46. In a manner known per se, a drop in the product temperature T2 from the
product temperature setpoint T2(S) causes a rise, and a rise in the product temperature T2
relative to the product temperature setpoint T2(S) causes a drop, in the steam temperature T1,
i.e., a respective deviation from the specified steam temperature setpoint T1(S) to be adjusted.
Initial phase
In an initial phase of the treatment of the liquid food product P that can be seen inter alia in
Fig. 4, product fouling F has not yet occurred. Fig. 4 shows a diagram for a volumetric flow Q
depending on a delivery pressure p, two pump characteristics PKL for the centrifugal pump 14,
and a standard pipeline characteristic RKL for the system 100. In the initial phase, the
centrifugal pump 14 is operated at the initial rotational speed n(o) lying below a rated rotational
speed n(N) of the centrifugal pump 14 by a given amount at its assigned pump characteristic
without product fouling PKL(o). In conjunction with the standard pipeline characteristic RKL,
an operating point is set without product fouling B(o). At this operating point B(o), the
centrifugal pump 14 delivers a volumetric flow without product fouling Q(o) against a delivery
pressure of the centrifugal pump without product fouling p(14)(o).
In the diagram for the steam temperature T1 as a function of time t (Fig. 6), for the product
temperature T2 as a function of time t (Fig. 5) and for power consumption L as a function of
time t (Fig. 7), the initial phase in this regard is always located to the left of a first point in time
t1 at which the product fouling F should for example begin. In Fig 6, a steam temperature
without product fouling T11 is in effect that corresponds to the steam temperature setpoint
T1(S) set as specified. In Fig 5, a product temperature without product fouling T21 is in effect
that corresponds to the product temperature setpoint T2(S) to be achieved as specified. In Fig.
7, power consumption without product fouling L1 of the centrifugal pump 14 is in effect that
results at the operating point without product fouling B(o) from the initial rotational speed
without product fouling n(o).
When product fouling F starts at the first point in time t1, the volumetric flow through the
centrifugal pump 14 decreases, as shown in Fig. 4, by a volumetric flow differential ΔQ to a
volumetric flow with product fouling Q(F)1 with a delivery pressure of the centrifugal pump
with product fouling p(14)(F)1 reduced by a delivery pressure differential Δp(14). A first
operating point with product fouling B(F)1 occurs in an associated pump characteristic with
product fouling PKL(F)1 while the initial rotational speed n(o) is initially unchanged in
conjunction with the approximately unchanged pipeline characteristic RKL. The reduction of
the volumetric flow without product fouling Q(o) by the volumetric flow differential ΔQ to the
volumetric flow with product fouling Q(F)1 at a second point in time t2 selected as an example
leads to a temperature drop ΔT2 of the product temperature T2, namely from the product
temperature without product fouling T21 to a product temperature with product fouling T22
(Fig. 5).
The depicted time differential t2-t1 can be a finite time differential Δt, but it can also be a
differential time interval dt, wherein control and/or regulation is performed with any given
number of sequential time intervals dt. The control and/or regulation according to the invention
should be configured for both cases. In the context of the temperature drop ΔT2 depicted in
Fig. 5, a temperature rise ΔT1 in the steam temperature T1 occurs as of the first point in time
t1 and up to the second point in time t2, namely from the steam temperature without product
fouling T11 to a steam temperature with product fouling T12 (Fig. 6). Without remedial
measures according to the invention, the temperature conditions in Fig. 5, 6 would manifest, so
that the first operating point with product fouling B(F)1 in Fig. 7 with an unchanged initial
rotational speed n(o) and an unchanged power consumption with product fouling L1 would be
situated at the second point in time t2.
Control phase
Upon the beginning of product fouling F at the first point in time t1, the method according to
the invention provides that a reduction in the volumetric flow of the centrifugal pump 14 is then
counteracted by an increase in the initial rotational speed n(o) when this reduction occurs at the
same time as a temperature drop ∆T2 in the product temperature T2. The initial rotational speed
n(o) is increased depending on the temperature drop ∆T2 of the product temperature (T2),
and/or the temperature rise ΔT1 of the steam temperature T1. The increase in the initial
rotational speed n(o) as a function of the temperature drop ΔT2 and/or the temperature rise ΔT1
is continued until the product temperature setpoint T2(S) to be achieved as specified and/or the
necessary steam temperature T1 to achieve the product temperature setpoint T2(S) at the start
of treatment, consistently occur/occurs.
The result of the control phase is apparent from Fig. 4 and 7. The increase in the initial rotational
speed n(o) by a rotational speed differential Δn leads to a rotational speed with product fouling
n(F)2 = n(o) + Δn at a second operating point with product fouling B(F)2 of an associated pump
characteristic with product fouling PKL(F)2. At a second operating point with product fouling
B(F)2, a volumetric flow with product fouling Q(F)2 and a delivery pressure with product
fouling p(14)(F)2 occur, wherein Q(F)2 = Q(o) and p(14)(F)2 = p(14)(o) (Fig. 4). In Fig. 7, it
is apparent that in the time period at issue between the first and second point in time t1, t2, a
rise in the power consumption L by the centrifugal pump 14 is discernible by a power
differential ∆L from the power consumption without product fouling L1 to power consumption
with product fouling L2 (second operating point with product fouling B(F)2 at the rotational
speed with product fouling n(F)2) from increasing the initial rotational speed n(o) by the
rotational speed differential Δn.
Both the second operating point with product fouling B(F)2 as well as an associated pump
characteristic with product fouling PKL(F)2 are identical with the operating point without
product fouling B(o), or respectively the pump characteristic without product fouling PKL(o).
This is a necessary result because in accordance with the object, after successfully controlling
and/or regulating, as presented above, the volumetric flow Q through the infuser container 10
and the adjacent centrifugal pump 14, the liquid level N and accordingly the dwell time in the
infuser container 10 up to inside the centrifugal pump 14 are kept constant, and the product
temperature T2 as well as the steam temperature T1 are returned to their specified setpoints
T2(S), or respectively T1(S).
In an advantageous embodiment, the method according to the invention provides that the
increase in the initial rotational speed n(o) occurs steadily in the sense of real-time regulation.
In this regard, it is furthermore proposed that the gradient of the steady increase in the initial
rotational speed n(o) results from regulatory requirements, and is set depending on the
temperature drop ΔT2, and/or the temperature rise T1, and/or on product-specific requirements
as well.
Alternatively to the above proposal, another embodiment provides that the increase in the initial
rotational speed n(o) occurs in at least one discrete step with a rotational speed differential Δn
that results from regulatory requirements. In this regard, it is furthermore provided that the
rotational speed differential Δn is set depending on the temperature drop ΔT2, and/or the
temperature rise ΔT1, and/or product-specific requirements.
Fig. 8 shows a screen section of a graphic measuring record for the method according to the
invention used for the treatment of 35,000 L of cream within a treatment period of
approximately 3 hours (see time axis t, 8:33 to 11:33 o’clock). The top line in the measuring
record shows the readiness of the system 100 for operation, wherein the stair-shaped beginning
up to approximately 8:20 o’clock in this regard represents the starting phase of the system 100
with water. The employed centrifugal pump 14 is a centrifugal pump modified according to the
invention with a rated power of 15 kW, a rated rotational speed of n(N) = 2,900 rpm, and an
outer diameter of the impeller wheel that was machined from 205 mm to 195 mm to rinse the
pump chamber 68 and the impeller wheel 14.3 itself in the sense described below.
The treatment of the cream starts with an initial rotational speed of n(o) = 2117 rpm that is 73%
below the rated rotational speed of n(N) = 2,900 rpm (given amount below the rated rotational
speed n(N) according to step (b) of claim 1). At the end of the operating phase, the rotational
speed n has risen to 77% of the rated rotational speed by increasing the rotational speed
according to the invention, and is therefore n = 2233 rpm. The increase of the rotational speed
was executed steadily as indicated by the control variable for the flow (bottom line in the graph,
“control variable – (14) – flow”). The power consumption of the rotational-speed-regulated
drive motor of the centrifugal pump 14 is approximately proportional to the rotational speed n
of the drive motor and hence the centrifugal pump 14. The wide bar identified by “14 – flow”
represents the actual power consumption of the drive motor, wherein the fluctuation width of
the power consumption is explained by the rotational speed regulation of the drive motor as
such. The regulation of the rotational speed is realized by the centrifugal pump 14, the
associated rotational speed regulating apparatus 42 (SC), and by the product-specific default
parameters saved in the control and regulating apparatus 50 (Fig. 3).
The diagram according to Fig. 8 moreover clearly reveals that the requirement, namely of
keeping the product temperature T2 constant despite product fouling F is satisfied very well
over the entire treatment period of 3 hours with T2 = 144°C. The components participating
therein are the temperature regulating apparatus 44 (TIC), the product-specific default
parameters saved in the control and regulating apparatus 50, and the control valve 46 (Fig. 3).
The goal envisioned by the solution according to the invention, and to be pursued in any event,
of returning the steam temperature T1 at a constant product temperature T2 and over the entire
treatment period of 3 hours to the value (T1(8:33 o’clock) = 146.2°C) required at the beginning
of the treatment time period, or respectively also at the end, is not achieved with T1 (11:33
o’clock) = 147.7°C and hence with an associated temperature differential ΔT1 = 1.5°C. In the
present case, an initial explanation can be offered in that, to protect to the product of cream
according to the customer’s wishes, the reduction of the volumetric flow of the centrifugal
pump 14 by product fouling F was not entirely overcome by the necessary and possible increase
in the rotational speed. A second explanation could be that reheating the infuser-heated liquid
food product P’ that also occurs in this region was restricted by unexpectedly strong product
fouling F between the outlet opening 10.3 of the infuser container 10 and the exit from the
centrifugal pump 14 despite fully compensating for a reduction in the volumetric flow Q of the
central pump in this regard, and this restriction could only be permanently compensated by a
steam temperature T1 higher by ΔT1 = 1.5°C in the context of the method according to the
invention. Nonetheless, the result depicted in Fig. 8 obtained under real conditions in a
production facility, and taking into account customer requirements of a gentle treatment of the
customer’s heat-sensitive liquid food product P, does not cast any doubt on the method
according to the invention; it is in contrast a confirmation of the validity of the approach of the
solution according to the invention.
The arranged position of a centrifugal pump 14 according to the invention and depicted in Fig.
9 has a horizontally oriented rotational axis of a pump shaft. In conjunction with an infuser
container 10, the rotational axis of the pump shaft is preferably oriented in the direction of
gravity, whereby this centrifugal pump 14 can be advantageously connected by an inlet 60 that
can be designed as a suction port directly to the bottom end of the drainpipe 12 discharging out
of the outlet opening 10.3 in the infuser container 10. The centrifugal pump 14 in the
embodiment according to the invention is particularly suitable for delivering heat-sensitive
liquid food products P that enter through the inlet 60 and exit out of an outlet 62 designed as a
pressure port. In a manner known per se, the centrifugal pump 14 moreover possesses the pump
housing 14.2 that is formed by at least a housing cover 64 and a housing rear wall 66. The pump
chamber 68 which is in fluidic connection with the inlet 60 and the outlet 62 is formed in the
pump housing 14.2 and accommodates the impeller wheel 14.3. The impeller wheel 14.3 with
its blades 72 and the blade channels 74 formed by them is designed open toward the housing
cover 64 and closed to the housing rear wall 66 by an impeller wheel rear side 70. The impeller
wheel rear side 70 is at a distance from the housing rear wall 66 by a rear impeller wheel gap
s1. A front side of the impeller wheel 14.3 substantially formed by the front edges of the blades
72 is also at a distance from the housing cover 64 by a front impeller wheel gap s2. The inlet
60, the housing cover 64 and the housing rear wall 68 can be bordered entirely or partially, for
example in the form of a pump-housing-side coolant chamber 14.1 for the purpose of the first
cooling K1.
The front impeller wheel gap s2 is increased in comparison to a minimum front impeller wheel
gap s2* that ensures the mechanical functioning of the centrifugal pump 14 by reducing the
width of the impeller wheel 14.3, namely such that it undergoes a maximum enlargement at an
outer diameter DL of the impeller wheel 14.3 which preferably decreases continuously into the
region of the entrance into the blade channels 74 to the minimum front impeller wheel gap s2*,
and the reduction of the width of the impeller wheel 14.3 at the outer diameter DL is 40 to 50%
of the width of a hydraulically optimized impeller wheel.
Each blade channel 74 of the impeller wheel 14.3 between two adjacent blades 72 is fluidically
connected to the rear impeller wheel gap s1 in the region of its adjacent impeller wheel rear
side 70 by at least one rinsing hole 76 that penetrates the impeller wheel rear side 70. The
geometric location for the respective penetration site of the rinsing hole 76 in the impeller wheel
rear side 70 is determined by the middle of the blade channel 74 relative to the spacing of the
blades 72 at the penetration site, and approximately by the middle of a maximum flow string
length of the blade channel 74 between its entrance and exit. All rinsing holes 76 in this case
are preferably arranged on a single circle of holes.
Another preferred embodiment provides that the access to a minimum rear, radially-oriented
impeller wheel gap s1* that ensures the mechanical functioning of the centrifugal pump 14 and
that begins at the outer diameter DL of the impeller wheel 14.3 is increased by up to 5 mm by
reducing the outer diameter DL. A necessary and desirable enlargement of the rear impeller
wheel gap s1 exists in that the impeller wheel rear side 70 undergoes an annular drilling out 78
in the region between the rinsing hole 76 and a hub of the impeller wheel 14.3 with an axial
depth of up to 2 mm.
The rinsing hole 76 is either designed preferably circular with a hole diameter Db, or it
alternatively has a shape that deviates from the circular shape with a hydraulic diameter Dh that
is standard for this shape, wherein the hydraulic diameter Dh is dimensioned as a quotient in a
known manner from four times the passage cross-section of the rinsing hole 76 and the
circumference of the rinsing hole 76. In this case, it is preferably suggested that the hole
diameter Db or the hydraulic diameter Dh is 30 to 50% of the spacing of the blades 72 at the
penetration site of the rinsing hole 76.
Finally, Fig. 9 shows, approximately and schematically indicated, a first rinsing flow S1, a
second rinsing flow S2, and a third rinsing flow S3 according to the invention which will be
explained in greater detail below.
The following measures with which a centrifugal pump according to the prior art, preferably a
commercially available centrifugal pump, is to be modified according to the invention, ensure
the rinsing of the impeller wheel 14.3 according to the invention in combination with each other
or also considered by themselves:
• widen the rear impeller wheel gap s1 and/or the front impeller wheel gap s2 (see Fig. 9), either
o by drilling out the impeller wheel 14.3 on both sides,
o or by an axially effective spacer element in the direction of a pump shaft which
is arranged at the connecting point between the housing cover 64 and the housing
rear wall 66, wherein the impeller wheel 14.3 is not axially offset relative to the
housing rear wall 66, or is correspondingly axially offset on or with the pump
shaft in the pump chamber 68.
• arrange the aforementioned rinsing holes 76 in the above-described manner.
By widening the rear impeller gap s1, or respectively by the expanded access thereto, the
associated rear wheel side chamber is impinged upon over its entire radial area of extension
more or less unrestrictedly by the static pressure predominating at the exit side of the impeller
wheel 14.3 that possesses the outer impeller wheel diameter DL at that location. In the blade
channel 74, there is less static pressure at the respective rinsing hole 76 than in the rear wheel
side chamber. In the blade channel 74, this yields the first rinsing flow S1 directed from the
inside to the outside. When the treated liquid food product P* located in the rear wheel side
chamber is cooled if appropriate at the housing rear wall 66 because the first cooling K1 is
provided there if appropriate, treated liquid food product P* permanently cooled by the first
rinsing flow S1 preferably passes into the core region of the flow in the blade channel 74.
By means of the described widening of the front impeller wheel gap s2, the third rinsing flow
S3 can form viewed over the respective end face front edge of the blades 72 and over their axial
area of extension. The propulsion forces for this third rinsing flow S3 result from the difference
in pressure at each blade 72 that exists from the static pressure on the blade top side, a pressure
side, and by the static pressure on the blade bottom side, a suction side. The third rinsing flow
S3 brings about an exchange of the treated liquid food product P* into and out of the core region
of the flow in the associated blade channel 74.
Due to the wider front impeller wheel gap s2, a radially oriented second rinsing flow S2 can
form due to the difference in the static pressure at the exit of the impeller wheel 14.3 and the
static pressure in the suction side entrance of the impeller wheel 14.3 that overlaps the third
rinsing flow S3 in a more or less perpendicular manner. Here as well, this second rinsing flow
S2 brings about an exchange of the treated liquid food product P* into and out of the core region
of the flow in the associated blade channel 74.
REFERENCE LIST OF THE ABBREVIATIONS USED
Fig. 1 (prior art)
100 System
10 Infuser container – (general)
.4 Container-bottom-side coolant chamber
12 Drainpipe
12.1 Drainpipe-side coolant chamber
14 First delivery apparatus
14.1 Pump-housing-side coolant chamber
16 Vacuum chamber
18 Second delivery apparatus
Product inlet
22 External steam inlet
24 Internal steam inlet
26 Pump-side coolant entrance
28 Infuser-side coolant exit
Connecting line
32 Vapor exit
34 Drain line - (for treated food product)
D Steam
D1 External steam
D2 Internal steam
K Cooling
P Liquid food product
P’ Infuser-heated liquid food product
P* Treated liquid food product
W Water
Figures 2 and 3
(10 Infuser container)
.1 Container jacket
10.2 Container bottom
.3 Outlet opening
(10.4 Container-bottom-side coolant chamber)
.4.1 Third coolant entrance
10.4.2 Third coolant exit
(12 Drainpipe)
(12.1 Drainpipe-side coolant chamber)
12.1.1 Second coolant entrance
12.1.2 Second coolant exit
14 Centrifugal pump
(14.1 Pump-housing-side coolant chamber)
14.1.1 First coolant entrance
14.1.2 First coolant exit
14.2 Pump housing
14.3 Impeller wheel
24.1 Steam line
40 Temperature measuring apparatus
42 Rotational speed regulating apparatus
44 Temperature regulating apparatus
46 Control valve – (for steam D, D2)
48 Signal line
50 Control and regulating apparatus
K1 First cooling (of the pump housing 14.2)
K2 Second cooling (of the drainpipe 12)
K3 Third cooling (of the container bottom 10.2)
N Liquid level
SC Rotational speed regulation
T1 Steam temperature – (steam D, D2)
T1(S) Steam temperature setpoint (steam D, D2)
TIA Temperature display and alarm
T2 Product temperature (infuser-heated food product P’)
T2(S) Product temperature setpoint
TIC Temperature display and regulation
a, b, d, d Connections (control and regulation apparatus 50 and (40, 42, 44, 46))
h Drop height
∆h Change in the liquid level
p(14) Delivery pressure of the centrifugal pump
n Rotational speed (in rpm or rotational frequency in rps)
Figures 4 to 8
F Product foulings
B(o) Operating point without product fouling
B(F)1 First operating point with product fouling – (at n(o))
B(F)2 Second operating point with product fouling – (at n(F)2 = n(o) + ∆n)
L Power consumption – (centrifugal pump 14)
L1 Power consumption without product fouling – (at n(o))
L2 Power consumption with product fouling – (at n(F)2 = n(o) + ∆n)
∆L Power differential
PKL Pump characteristic, general
PKL(o) Pump characteristic without product fouling – (at n(o))
PKL(F)1 Pump characteristic with product fouling – (at n(o))
PKL(F)2 Pump characteristic with product fouling – (at n(F)2 = n(o) + ∆n)
Q Volumetric flow - (general)
Q(o) Volumetric flow without product fouling – (at n(o))
Q(F)1 Volumetric flow with product fouling – (at n(o))
Q(F)2 Volumetric flow with product fouling – (at n(F)2 = n(o) + ∆n)
ΔQ Volumetric flow differential
RKL Pipeline characteristic
T11 Steam temperature without product fouling ( = T1(S))
T12 Steam temperature with product fouling
ΔT1 Temperature rise – (from product fouling)
T21 Product temperature without product fouling ( = T2(S))
T22 Product temperature with product fouling
ΔT2 Temperature drop – (from product fouling)
n(o) Initial rotational speed (without product fouling)
n(F)2 Rotational speed with product fouling at the second operating point – (at B(F)2)
n(N) Rated rotational speed – (of the centrifugal pump 14 at the design point)
Δn Rotational speed differential (or respectively rotational frequency differential)
P Delivery pressure (general)
p(14)(o) Delivery pressure of the centrifugal pump without product fouling (at B(o))
p(14)(F)1 Delivery pressure of the centrifugal pump with product fouling (at B(F)1)
p(14)(F)2 delivery pressure of the centrifugal pump with product fouling (at B(F)2)
Δp(14) Delivery pressure differential
t Time – (general)
t1 First point in time – (start of product fouling)
t2 Second point in time – (increased product fouling)
Δt Finite time difference
dt Differential time difference
Fig. 9
(14 Centrifugal pump)
(14.1 Pump-housing-side coolant chamber)
(14.2 Pump housing)
(14.3 Impeller wheel)
60 Inlet (suction port)
62 Outlet (pressure port)
64 Housing cover
66 Housing rear wall
68 Pump chamber
70 Impeller wheel rear side
72 Blade
74 Blade channel
76 Rinsing hole
78 Annular drilling out
DL Outer impeller wheel diameter
Db Hole diameter
Dh Hydraulic diameter
(K1 First cooling (of the pump housing 14.2))
S1 First rinsing flow
S2 Second rinsing flow
S3 Third rinsing flow
s1 Rear impeller wheel gap
s1* Minimum rear impeller wheel gap
s2 Front impeller wheel gap
s2* Minimum front impeller wheel gap
Claims (12)
1. A method for controlling and/or regulating the treatment of heat-sensitive liquid food products (P), wherein steam (D; D1, D2) directly heats the liquid food product (P) to establish a germ- 5 free state in an infuser container (10), wherein water (W) is removed from the liquid food product (P) by flash evaporation at a low pressure in an amount which corresponds to that of the previously supplied steam (D; D1, D2), wherein the liquid food product (P) is delivered by means of a centrifugal pump (14) 10 between heating and flash evaporation, wherein the liquid food product (P) undergoes cooling (K) in at least one section of this flow path by each of the associated walls bordering this flow path starting upon entry into a base region of the infuser container (10) and at most until entering the centrifugal pump (14), 15 wherein the centrifugal pump (14) has an inlet (60), an outlet (62), a pump housing (14.2) that is formed by at least a housing cover (64) and a housing rear wall (66), and in which pump housing (14.2) a pump chamber (68) is formed which is in fluidic connection with the inlet (60) and the outlet (62), wherein the centrifugal pump (14) has an impeller wheel (14.3) rotatably accommodated 20 in the pump chamber (68), which impeller wheel (14.3) is designed open toward the housing cover (64) and closed to the housing rear wall (66) by a rear side of the impeller wheel (70), wherein the centrifugal pump (14) comprises a front impeller wheel gap (s2) provided between the housing cover (64) and the impeller wheel (14.3), and a rear impeller wheel 25 gap (s1) provided between the housing rear wall (66) and the impeller wheel (14.3), wherein the front impeller wheel gap (s2) is increased in comparison to a minimum front impeller wheel gap (s2*) that ensures the mechanical functioning of the centrifugal pump (14) by reducing the width of the impeller wheel (14.3), wherein the front impeller wheel (s2) gap undergoes a maximum increase at an outer 30 diameter (DL) of the impeller wheel (14.3) that decreases to the minimum front impeller wheel gap (s2*) into the region of the entrance into the blade channels (74) of the impeller wheel (14.3), and wherein the reduction of the width of the impeller wheel (14.3) at the outer diameter (DL) of the impeller wheel (14.3) is 40 to 50% of the width of a hydraulically optimized impeller wheel, and wherein the following steps (a) to (e) are provided: 5 (a) a product temperature (T2) detected downstream after the centrifugal pump (14) of an infuser-heated liquid food product (P’) is regulated by supplying steam (D; D1, D2) at a steam temperature (T1) to a head region of the infuser container (10) at a product-specific product temperature setpoint (T2(S)) to be achieved as specified, wherein a drop in the product temperature (T2) causes a rise, and a 10 rise in the product temperature (T2) cause a drop, in the steam temperature (T1); (b) in an initial phase of the treatment of the liquid food product (P), the centrifugal pump (14) is operated at an initial rotational speed (n(o)) lying below a rated rotational speed (n(N)) of the centrifugal pump (14) by a predetermined amount, wherein the initial rotational speed (n(o)) is dependent on the liquid food product 15 (P) and/or on the design of the centrifugal pump (14); (c) a reduction of the volumetric flow of the centrifugal pump (14) is then counteracted by an increase in the initial rotational speed (n(o)) when said reduction occurs at the same time as a temperature drop (∆T2) in the product temperature (T2); 20 (d) the initial rotational speed (n(o)) is increased depending on the temperature drop (∆T2) of the product temperature (T2), and/or a temperature rise (ΔT1) of the steam temperature (T1), wherein the extent of the increase in the initial rotational speed (n(o)) results from a regulatory requirement of keeping at least the product temperature (T2) constant; 25 (e) steps (c) and (d) are repeatedly executed until the specified product temperature setpoint (T2(S)) to be achieved as specified, and/or the steam temperature (T1) needed to achieve the product temperature set point (T2(S)) at the start of treatment, consistently occur/occurs. 30
2. The method according to claim 1, characterized in that the increase in the initial rotational speed (n(o)) occurs steadily.
3. The method according to claim 2, characterized in that the gradient of the steady increase in the initial rotational speed (n(o)) results from regulatory requirements, and is set depending on the temperature drop (ΔT2), and/or the 5 temperature rise (ΔT1), and/or on product-specific requirements.
4. The method according to claim 1, characterized in that the increase in the initial rotational speed (n(o)) occurs in at least one discrete step with 10 a rotational speed differential (Δn) that results from regulatory requirements.
5. The method according to claim 4, characterized in that the rotational speed differential (Δn) is set depending on the temperature drop (ΔT2), 15 and/or the temperature rise (ΔT1), and/or product-specific requirements.
6. The method according to one of the preceding claims, characterized in that the initial rotational speed (n(o)) and/or the product temperature setpoint (T2(S)) are or 20 is set depending on default parameters that are characteristic of the liquid food product (P), wherein “default parameters” are understood to be the physical variables such as density, viscosity and thermal conductivity of the liquid food product (P), and/or its composition such as the portion of fat and protein. 25
7. The method according to one of the preceding claims, characterized in that the initial rotational speed (n(o)) and/or the product temperature setpoint (T2(S)) are or is adjusted depending on the physical boundary conditions to which the method is subjected, wherein the “physical boundary conditions” of the method are understood to 30 be process-related default parameters of the method such as pressure and temperature.
8. The method according to one of claims 2 to 7, characterized in that the initial rotational speed (n(o)), and/or the product temperature setpoint (T2(S)), and/or the rotational speed differential (Δn), and/or alternatively to the rotational speed differential (Δn), the gradient of the steady increase in the initial rotational speed (n(o)) are or is adjusted by means of a calibration function tested and saved before or while 5 starting the method.
9. The method according to one of the preceding claims, characterized in that the liquid food product (P) is supplied annularly, and is impinged on from the inside by 10 internal steam (D2) and from the outside by external steam (D1), and the supply of the external steam (D1) is adjusted depending on a required supply pressure for the internal steam (D2) in the head region of the infuser container (10), and by differential pressure regulation. 15 10. A system (100) for controlling and/or regulating the treatment of heat-sensitive liquid food products (P) with an infuser container (10) in the headspace of which a steam line (24.1) for steam (D; D2) and a product inlet (20) terminate, with a vacuum chamber (16) fluidically connected to the infuser container (10) by a connecting line (30), with a centrifugal pump (14) arranged in the connection line (30), with an outlet opening (10.3) 20 arranged in a container bottom (10.2) of the infuser container (10), and a drainpipe (12) connecting to the outlet opening (10.3) and terminating in the centrifugal pump (14), • with a container-bottom-side coolant chamber (10.4), and moreover • with a pump-housing-side coolant chamber (14.1) • and/or with a drainpipe-side coolant chamber (12.1), 25 characterized in that • the centrifugal pump (14) has an inlet (60), an outlet (62), a pump housing (14.2) that is formed by at least a housing cover (64) and a housing rear wall (66), and in which pump housing (14.2) a pump chamber (68) is formed which is in fluidic connection with the inlet (60) and the outlet (62), 30 • the centrifugal pump (14) has an impeller wheel (14.3) rotatably accommodated in the pump chamber (68), which impeller wheel (14.3) is designed open toward the housing cover (64) and closed to the housing rear wall (66) by a rear side of the impeller wheel (70), • the centrifugal pump (14) comprises a front impeller wheel gap (s2) provided between the housing cover (64) and the impeller wheel (14.3), and a rear impeller wheel gap (s1) provided between the housing rear wall (66) and the impeller wheel (14.3), 5 • the front impeller wheel gap (s2) is increased in comparison to a minimum front impeller wheel gap (s2*) that ensures the mechanical functioning of the centrifugal pump (14) by reducing the width of the impeller wheel (14.3), • the front impeller wheel (s2) gap undergoes a maximum increase at an outer diameter (DL) of the impeller wheel (14.3) that decreases to the minimum front
10 impeller wheel gap (s2*) into the region of the entrance into the blade channels (74) of the impeller wheel (14.3), and • the reduction of the width of the impeller wheel (14.3) at the outer diameter (DL) of the impeller wheel (14.3) is 40 to 50% of the width of a hydraulically optimized impeller wheel, 15 • downstream directly after the centrifugal pump (14), a temperature regulating apparatus (44) is provided in the connecting line (30) which is configured to regulate a product temperature (T2) and interacts with a control valve (46) arranged in the steam line (24.1), • downstream after the control valve (46), a temperature measuring apparatus (40) 20 is provided in the steam line (24.1) for a steam temperature (T1), • the centrifugal pump (14) is assigned a rotational speed regulating apparatus (42) for regulating a rotational speed (n) of the centrifugal pump (14), • and a control and regulating apparatus (50) is provided that adjusts a product- specific initial rotational speed (n(o)) of the centrifugal pump (14) and the steam 25 temperature (T1) and executes an increase in the initial rotational speed n(o)) in conjunction with the temperature regulating apparatus (44), the control valve (46), the temperature measuring apparatus (40) and the rotational speed regulating apparatus (42). 30
11. The system (100) according to claim 10, characterized in that the container-bottom-side coolant chamber, the drainpipe-side coolant chamber, and the pump-housing-side coolant chamber (10.4, 12.1, 14.1) undergo cooling (K) separately from each other.
12. The system (100) according to claim 10, characterized in that 5 at least two coolant chambers (10.4, 12.1, 14.1) are series-connected with each other and undergo cooling (K) in a countercurrent to an infuser-heated food product (P’).
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201762485132P | 2017-04-13 | 2017-04-13 | |
US62/485,132 | 2017-04-13 | ||
PCT/US2018/027428 WO2018191583A1 (en) | 2017-04-13 | 2018-04-13 | High-shrink, high-strength multilayer film |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ758118A NZ758118A (en) | 2021-05-28 |
NZ758244B2 true NZ758244B2 (en) | 2021-08-31 |
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