CH712542A2 - Vacuum cooling system and method for operating such a vacuum cooling system. - Google Patents

Abstract

The invention is based on a vacuum cooling system (10) with a closable vacuum chamber (11), the interior (11a) of which can be fed with food to be cooled (16), with at least one via an intake line (23) to the interior (11a) of the vacuum chamber (11a). 11) in connection with a vacuum pump (12) and with a chamber control (13), by means of which the pressure in the vacuum chamber (11) and / or the temperature in the dough (16) can be varied as a function of time along a predetermined curve , A simplified structure of the system is achieved in that the at least one vacuum pump (12) is a motor-driven, speed-controlled, dry-compressing claw vacuum pump that the chamber controller (13) via a motor controller (14) controls the speed of the at least one vacuum pump (12) in that the inlet of the at least one vacuum pump (12) is fluidly connected directly to the interior (11a) of the vacuum chamber (11).

Description

Description TECHNICAL AREA

The present invention relates to the field of vacuum cooling. It relates to a vacuum cooling system according to the preamble of claim 1.

It further relates to a method for operating such a vacuum cooling system.

STATE OF THE ART

The cooling of baked or pre-baked baked goods in a vacuum chamber by vaporizing the moisture contained in the baked goods has long been known in baking technology.

Baked goods are to be understood in a broader sense as pastry products of various kinds, e.g. Bread, rolls, other biscuits, pizzas and cakes that get essential properties through a thermal treatment (baking). But also included are products that are thawed and baked as frozen dough pieces and products that are first pre-baked to a certain percentage and then baked, for example, in retail outlets or by end customers.

At such baked goods various requirements are made. For example, the bread offered in the retail outlets should be fresh and have a crunchy crust. In addition, the bread should also be cut on customer request, to be cut immediately before the sale in the presence of the customer.

During the cooling process following baking, the baked product is deprived of a few percent of the total weight of product moisture. This dehumidification can be compensated by appropriate process adjustment of the baking process, for example, by shorter baking times, but this often draws disadvantages of other kinds. So it can be e.g. happen that shortened baking times also reduces the formation of roasted aromas in the crust. These aromas are due to the well-known Maillard reaction, a non-enzymatic browning reaction responsible for the typical aroma and the coloration of protein-rich roasted, baked and fried only in the last minutes of a baking phase.

The usual available on the market vacuum cooling systems for cooling food, especially hot baked goods, have an essential common feature: The pressure profile is controlled by a valve which is arranged in the connecting pipe between the vacuum chamber and the vacuum pump, while the vacuum pump with constant or only slightly changing speed runs (see for example GB 141 3481 A or EP 0 006 290 A1 or DE 2 507 003 A1).

This solution is based on the common technique for controlling fluid flows (gas or liquids) and takes into account the fact that the relatively large vacuum pumps have a correspondingly large mass moment of inertia. Typically, oil lubricated rotary vane pumps or dry screw pumps are used.

Many vacuum cooling systems also work with capacitors. Thus, a portion of the resulting during the vacuum cooling process steam is eliminated by means of an actively cooled condenser, which reduces the workload for the vacuum pump, because not the entire amount of steam needs to be removed via the pump. The condenser is in the vapor flow between the vacuum chamber and the vacuum pump (see, for example, EP 2 177 851 A1).

The use of a capacitor allows to use smaller and cheaper vacuum pumps; However, the thermal cooling work is not reduced (1st law of thermodynamics), the lower energy consumption of the smaller pump is offset by a higher energy demand by the active cooling of the capacitor.

Economically, the combination of capacitor and smaller vacuum pump is advantageous if a water-cooled vacuum pump is used anyway, because the necessary water cooler (chiller) can also be used to cool the capacitor. The savings made by the smaller pump and the additional costs for the condenser result in a total saving.

The disadvantages of the capacitor are the higher complexity of the whole system, combined with additional cleaning effort. From a hygienic point of view, a condenser is not the first choice because the moisture in the condensate tank is basically a risk of contamination.

To realize the necessary for the vacuum cooling highly dynamic pressure control exclusively on the variation of the pump speed, is limited because of the moment of inertia of the above pump types possible.

Thus, document EP 2 832 242 A1 discloses a method for controlling a vacuum cooling device for cooling a foodstuff, in particular hot baked goods. The vacuum cooling device includes a vacuum chamber for receiving the food. This vacuum chamber is fed with food to be cooled, wherein the food is assigned a cooling program, the vacuum chamber is closed, a vacuum pump is put into operation to evacuate the vacuum chamber. The pressure in the vacuum chamber is detected with a pressure gauge or a temperature measurement is carried out in the vacuum chamber and the pressure is controlled based on the temperature measurement. The pressure gauge converts the pressure into a pressure measurement signal. The pressure measurement signal becomes one

Control unit supplied. The control unit contains a storage element, wherein the storage element contains the cooling program for each food to be cooled. The cooling program contains a desired pressure profile, wherein the desired pressure curve corresponds to the desired pressure profile of the vacuum cooling for the food to be cooled during the cooling period, wherein at least one time within the cooling period, the pressure measuring signal is compared with the target pressure at this time. The target pressure is assigned a target speed of the vacuum pump. The vacuum pump is equipped with a tachometer to measure the speed of the vacuum pump, wherein at least one time the speed of the vacuum pump is compared with the target speed and an adjustment element is provided to adjust the speed to the target speed.

The solution described in EP 2 832 242 A1 makes no specific information about the type of pump, in practice, however, water-cooled dry screw pumps are used. This type of pump can be operated at different speeds. However, the possible variation of the speed is limited both in terms of the usable speed range (co) and with respect to the speed change rate (dco / dt).

The present invention takes advantage of the fact that since recently vacuum pumps, in particular in the form of so-called claw vacuum pumps, are available, on the one hand also dry compaction and on the other hand have a dynamic servo drive. The design-related much lower mass moment of inertia of the claw vacuum pumps, coupled with a dynamic servo drive, enables new methods for pressure control. The previously necessary valve flaps for responsive (dynamic) pressure control are no longer necessary.

Furthermore, these new, advanced types of jaw vacuum pumps develop less heat loss, which makes it possible to cool exclusively with air even at high pumping speed. The usual liquid cooling (water, oil) is eliminated.

Overall, the system complexity could be significantly reduced in vacuum cooling systems. The elimination of control valve and liquid cooling increased reliability. The use of structurally and manufacturing technically simpler vacuum pumps reduced the manufacturing cost. Furthermore, the absence of a hygienic questionable capacitor reduced the cleaning and maintenance costs.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to provide a vacuum cooling system which has a significantly reduced system complexity.

It is a further object of the invention to provide a vacuum cooling system, which is characterized by increased reliability.

It is also an object of the invention to provide a vacuum cooling system which is manufactured and operated at a reduced cost.

It is finally an object of the invention to provide a method for operating such a vacuum cooling system.

These objects are achieved by the features of claims 1 and 10.

The invention relates to a vacuum cooling system with a closable vacuum chamber, the interior of which can be fed with abzukühlendem dough, with at least one via a suction line with the interior of the vacuum chamber in communication vacuum pump, and with a chamber control, by means of which the pressure in the Vacuum chamber and / or the temperature in the dough as a function of time along a predetermined curve can be changed.

It is characterized in that the at least one vacuum pump is a motor-driven, speed-controlled, dry-compressing claw vacuum pump that controls the chamber control via a motor controller, the speed of at least one vacuum pump, and that the input of the at least one vacuum pump directly to the interior the vacuum chamber is fluidly connected.

The constructionally much lower mass moment of inertia of the claw vacuum pumps, coupled with a dynamic servo drive, allows new methods for pressure control. The previously necessary valve flaps for responsive (dynamic) pressure control are no longer necessary.

Such motor-driven, variable speed, dry-compressing claw vacuum pumps are manufactured and offered for example by the company Busch, Maulburg (DE), under the name «Mink». These claw vacuum pumps have a high intake capacity and operate absolutely oil and non-contact. They have a very high efficiency, which has a positive effect on energy consumption and performance. Due to the non-contact operation, these vacuum pumps operate virtually maintenance-free.

If the claw vacuum pumps driven by a directly mounted synchronous motor, which is powered by a frequency converter, the respective pumping speed can be adapted to the process by the operation with the frequency converter, the rated speeds, for example, between 1200 and 4200 revolutions per Minute may vary. Depending on the type, the nominal pumping speeds of these claw vacuum pumps are, for example, between 40 m3 / h and 1200 m3 / h.

An embodiment of the vacuum cooling system according to the invention is characterized in that the at least one vacuum pump is an air-cooled, dry-compressing claw vacuum pump.

Since the available claw vacuum pumps deliver less heat loss, it is possible to cool even with high suction exclusively with air. The usual liquid cooling (water, oil) is eliminated, which simplifies the system and reduces operating costs.

Particularly flexible can operate the vacuum cooling system according to the invention, when a plurality of speed-controlled, air-cooled and dry-compressing claw vacuum pumps are fluidly connected to the interior of the vacuum chamber.

In this case, a plurality of claw vacuum pumps may be connected in parallel.

But it can also be connected in series, the multiple jaw vacuum pumps.

In both cases, it is conceivable that the multiple jaw vacuum pumps are the same, so have the same size and the same power. This simplifies maintenance and repair.

However, it is also conceivable in both cases that the multiple jaw vacuum pumps have different powers.

A further embodiment of the invention is characterized in that in the vacuum chamber, a temperature sensor is provided for the dough, which is connected to the chamber control.

The recorded temperature can be used to control the cooling process.

Another embodiment of the invention is characterized in that in the vacuum chamber, a pressure sensor is provided which is connected to the chamber control.

The recorded pressure can be used to control the cooling process, in particular also for controlling the vacuum pumps.

The inventive method for operating a vacuum cooling system according to the invention is characterized by the following steps: a. Opening the vacuum chamber; b. Introducing the cooled, hot baked goods into the interior of the vacuum chamber; c. gastight closure of the vacuum chamber filled with dough pieces; d. Cooling the baked good along a predetermined cooling curve by pumping the vacuum chamber by means of the at least one variable speed claw vacuum pump by correspondingly changing the rotational speed of the claw vacuum pump; e. Establishing pressure equalization in the vacuum chamber by introducing a gas or gas mixture into the vacuum chamber; f. Opening the vacuum chamber; and G. Removing the cooled baking material from the vacuum chamber.

BRIEF EXPLANATION OF THE FIGURES

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it:

1 shows the simplified system diagram of a vacuum cooling system according to an embodiment of the invention with a single variable-speed, dry-compressing claw vacuum pump.

2 shows the simplified system diagram of a vacuum cooling system according to another embodiment of the invention with two parallel speed-controlled, dry-compressing claw vacuum pumps of the same type; and

Fig. 3 shows the simplified system diagram of a vacuum cooling system according to another embodiment of the invention with two series-connected speed-controlled, dry-compressing claw vacuum pumps of different performance.

WAYS FOR CARRYING OUT THE INVENTION

Fig. 1 shows the simplified system diagram of a vacuum cooling system according to an embodiment of the invention with a single variable speed, dry compressing claw vacuum pump.

The vacuum cooling system 10 of Fig. 1 comprises a vacuum chamber 11, the interior 11a is accessible from outside via a lockable door (not shown) and with the door open with the dough 16 (breads, rolls, croissants, etc.) on several superimposed arranged levels 17 can be filled. The dough 16 can be pre-baked or even baked.

To the vacuum chamber 11, a speed-controlled, dry-compressing claw vacuum pump 12 is connected via a suction line 23 with a sufficiently large cross-section, the gases and moisture from the vacuum chamber 11 sucks, compressed and emits via an exhaust pipe 24. The claw vacuum pump 12 is driven by a frequency controlled drive controlled by a motor controller 14.

The desired cooling curve of the hot introduced into the vacuum chamber 11 baking material 16 is achieved by a corresponding pressure reduction curve. For this purpose, the instantaneous pressure in the vacuum chamber 11 is continuously measured by means of a pressure sensor connected to the interior 11a and passed the measured pressure to a chamber controller 13, the pressure in the vacuum chamber 11 in accordance with a stored in a memory 15 pressure reduction curve via the engine control 14 and the drive frequency or speed of the jaw vacuum pump 12 controls.

The pressure reduction curve may be steadily decreasing, but may also decrease stepwise or have inflection points and intermediate maxima. In particular, gases or gas mixtures or ambient air can be introduced into the vacuum chamber 11 during or at the end of the cooling phase in order to influence the pressure drop and / or to moderate the processes taking place in the dough. For this purpose, external gas sources 21, 22 may be connected to the vacuum chamber 11 via corresponding controllable valves V1. Ambient air can be admitted into the vacuum chamber 11 via the controllable valve V2 (in particular after filtering).

In the vacuum chamber 11, a temperature sensor 18 may additionally be provided, which is introduced into the baked goods 16 to be cooled. This temperature sensor 18 is connected to the chamber controller 13, so that at the same time when actually setting the predetermined pressure reduction curve in the dough itself 16 adjusting (inner) temperature can be determined and controlled and optionally used for a corrective intervention in the curve. Furthermore, it is conceivable to attach a humidity sensor 19 to the vacuum chamber 11 and to connect it to the controller 13. Hereby the moisture in the chamber can be monitored and if necessary moisture, e.g. in the form of steam, if necessary.

The structure of the system is simplified in that speed or frequency-controlled claw vacuum pumps are used with air cooling. The use of a dynamic and speed-controlled claw vacuum pump with air cooling is new in the history of vacuum cooling because the previously available claw vacuum pumps could not achieve the minimum required ultimate pressure needed for vacuum cooling. By combining two or more claw vacuum pumps of the same or different size, the requirements for the pressure curve, the pressure change rate and the final pressure can be elegantly and cost-effectively met. In particular, eliminates the costly expense of the control valves and the liquid cooling.

2 shows the simplified system diagram of a vacuum cooling system 10 'according to another embodiment of the invention with two parallel speed controlled, dry compacting claw vacuum pumps 12a and 12b same type and performance, and Fig. 3 shows the simplified system diagram of a vacuum cooling system 10 " According to a further embodiment of the invention with two series-connected speed-controlled, dry-compacting claw vacuum pumps 12a and 12b of different size and power.

The combination of two or more claw vacuum pumps allows a simple increase in the pumping speed, without causing a thermal overload due to the air cooling. For small vacuum chambers 11, two (or more) similar smaller jaw vacuum pumps 12a, 12b having a nominal suction capacity of e.g. 2 x 80 m3 / h in parallel. For larger vacuum chambers, which are operated in batch mode, according to FIG. 3 for the same reasons differently sized pumps 12a, 12b (eg 1 x 400 m3 / h + 1x1200 m3 / h) are connected in series, the larger pump 12b also by several parallel smaller pumps can be replaced (eg 1 x 400 m3 / h + (2x 630 m3 / h)). In operation, usually all pumps run at the same time and share the work.

So that the moisture present in the exhaust air can be specifically collected at the outputs of the pumps, it is expedient to arrange a condensate collector in the exhaust pipe 24 and to provide the cable sections leading therewith with a heat insulation.

REFERENCE NUMERAL LIST 10, 10 ', 10 "vacuum cooling system

Claims (10)

11 Vacuum chamber 11a Interior 12 Claw vacuum pump 12a, b Claw vacuum pump 13 Chamber control 14 Motor control (vacuum pump) 15 Storage 16 Baking goods 17 Level 18 Temperature sensor (for placing in the dough) 19 Humidity sensor (vacuum chamber) 20 Pressure sensor (vacuum chamber) 21,22 Gas source 23 intake pipe 24 exhaust pipe V1, V2 valve claims 1. Vacuum cooling system (10, 10 ', 10 ") with a closable vacuum chamber (11), the interior (11 a) with abzukühlendem baked goods (16) can be charged with at least one via a suction line (23) with the interior (11 a) Vacuum chamber (11) associated vacuum pump (12; 12a, 12b), and with a chamber controller (13), by means of which the pressure in the vacuum chamber (11) and / or the temperature in the dough (16) as a function of time along a predetermined curve can be changed, characterized in that the at least one vacuum pump (12; 12a, 12b) is a motor-driven, speed-controlled dry-compressing claw vacuum pump that the chamber controller (13) via a motor controller (14) the speed of the at least one vacuum pump (12; 12a, 12b), and in that the inlet of the at least one vacuum pump (12; 12a, 12b) is fluidly connected directly to the interior (11a) of the vacuum chamber (11). 2. Vacuum cooling system according to claim 1, characterized in that the at least one vacuum pump (12; 12a, 12b) is an air-cooled, dry-compressing claw vacuum pump. 3. Vacuum cooling system according to claim 2, characterized in that a plurality of speed-controlled, air-cooled and dry-compressing claw vacuum pumps (12a, 12b) with the interior (11a) of the vacuum chamber (11) are fluidly connected. 4. Vacuum cooling system according to claim 3, characterized in that the plurality of claw vacuum pumps (12a, 12b) are connected in parallel. 5. Vacuum cooling system according to claim 3, characterized in that the plurality of claw vacuum pumps (12a, 12b) are connected in series. 6. Vacuum cooling system according to one of claims 3 to 5, characterized in that the plurality of claw vacuum pumps (12a, 12b) are similar. 7. Vacuum cooling system according to one of claims 3 to 5, characterized in that the plurality of claw vacuum pumps (12a, 12b) have different powers. 8. Vacuum cooling system according to claim 1, characterized in that in the vacuum chamber (11) a Temperaturaufnehmer (18) for the dough (16) is provided, which with the chamber control (13) is connected. 9. Vacuum cooling system according to claim 1, characterized in that in the vacuum chamber (11), a pressure sensor (20) is provided which is connected to the chamber controller (13). 10. A method for operating a vacuum cooling system according to one of claims 1 to 9, characterized by the following steps: a. Opening the vacuum chamber (11); b. Introducing the hot baking material (16) to be cooled into the interior (11a) of the vacuum chamber; c. gastight closure of the vacuum chamber (11) filled with dough (16); d. Cooling the baked good (16) along a predetermined cooling curve by pumping the vacuum chamber (11) by means of the at least one variable-speed vacuum pump (12; 12a, 12b) by correspondingly changing the rotational speed of the vacuum pump (12; 12a, 12b); e. Establishing pressure equalization in the vacuum chamber (11) by introducing a gas or gas mixture into the vacuum chamber (11); f. Opening the vacuum chamber (11); and G. Removing the cooled baking material (16) from the vacuum chamber (11).