EP3335613A1

EP3335613A1 - Device for the condensation of steam in an air recirculation circuit of an industrial dishwasher or the like

Info

Publication number: EP3335613A1
Application number: EP16425113.4A
Authority: EP
Inventors: Andrea Ambrosi; Eros Pinaroli; Andrea Zinetti; Mauro Tosi
Original assignee: Bonferraro SpA
Current assignee: Bonferraro SpA
Priority date: 2016-12-19
Filing date: 2016-12-19
Publication date: 2018-06-20

Abstract

Steam condensation device comprising a condensation chamber (1) with relevant inlet (2) and outlet (3) ducts that form a circuit for the recirculation of moist air coming from a wash tank (4) of an industrial dishwasher or the like, a fan (5) suitable to guarantee the air circulation in the recirculation circuit, a plurality of spraying nozzles (8) arranged in the condensation chamber (1) and fed through a water pipe connected to the water mains system and provided with a valve, a level sensor suitable to detect the amount of water loaded into the device, a recirculation pump (11) that draws water from the bottom of the condensation chamber (1) and sends it to the spraying nozzles (8) through a recirculation duct (12), as well as a control unit operatively connected to the fan (5), to the valve, to the level sensor and to the recirculation pump (11).

Description

The present invention relates to industrial dishwashers or the like, and in particular to a device for the quick condensation of the steam present in the air that is discharged by said machines.
It is known that an industrial dishwasher operates at high temperatures of the wash/rinse water that imply the generation of a significant amount of steam, therefore an inconvenience to the user is the significant release of steam when the dishwasher is opened at the end of the wash cycle. In order to overcome said drawback the dishwasher must include also a steam condenser located in an air recirculation circuit that provides the condensation of the steam prior to the opening of the dishwasher, so as to prevent it from being released in the environment with adverse effects on the operator and/or on other machines present in the room also due to the significant change in temperature and humidity.
This type of condenser generally operates with cold water that is atomized in the air recirculation circuit through which the steam passes, so that the cooling of the steam and of the condenser walls causes the condensation of the water vapour. A water condenser therefore essentially consists of a condensation chamber with relevant inlet/outlet ducts, a water load pipe provided with a valve, a plurality of spraying nozzles fed through said pipe and arranged in said chamber, a pipe for draining water from the condensation chamber and a level sensor arranged in the chamber to detect the lack of water supply or drain.
A conventional condenser has a very simple operation, controlled by a relevant control unit, which consists in opening the water load valve for a pre-set time at the end of the rinse phase, with parallel activation of a fan such that the moist air present in the wash tank circulates between the condenser and the wash tank and the steam contained in said moist air is condensed by means of repeated passages through the condenser.
In order to limit the water consumption, it is advantageous that the water fed to the condenser and the same condensate coming from the moist air are used in the following wash cycle, whereby the pipe for draining water from the condensation chamber is preferably connected to a water heater where the water will be heated for use in the following rinse. It should be noted that a power saving is also achieved in this way, since the water is already partially heated from the contact with the steam and the condenser walls.
This known arrangement has the drawback that it cannot strike an optimal balance between the contrasting requirements of achieving a sufficient condensation of the steam, minimizing the consumption of water and power, and not excessively lengthening the duration of the wash cycle that is a very important parameter in an industrial dishwasher. It must also be noted that the amount of steam to be condensed depends on the volume of the wash tank, on the temperature of the rinse water and on the type of load whereby this variability makes it even more difficult to achieve an optimal condensation.
In fact, the condenser is designed to operate with given nominal conditions and cannot take into account the actual operating conditions of the machine. For example, with respect to the expected values, the amount of generated steam may be greater or smaller, the temperature of the condensation water may be higher or lower, and the flow rate of the water sprayed by the nozzles may be higher or lower due to an increased or reduced pressure in the water mains system and/or a clogging of the water supply circuit (e.g. in the filters or the sprayers themselves).
Moreover, an insufficient condensation may be due to the fact that the amount of water required for the rinse in the following cycle is not sufficient to condense all the steam. In that case, if the water is loaded in the amount required to condense all the steam a portion of the water will be wasted since it is in excess for the rinse in the following cycle.
It should also be noted that if the water is loaded in the correct amount yet with a reduced flow rate to provide the time for the moist air present in the wash tank to perform repeated passages through the condenser in order to increase the steam condensation, this results in an unacceptable lengthening of the duration of the condensation phase.
Therefore the object of the present invention is to provide a device for the condensation of steam that is free from said drawbacks. Said object is achieved by means of a device comprising a recirculation pump for the water loaded in the condenser that is returned to the nozzles through a recirculation duct. Other advantageous features of the present device are specified in the dependent claims, in particular the use of a thermal and/or hygrometric probe that is able to detect the temperature and/or the humidity of the air that is being recirculated, as well as various alternatives for the loading of the condensation water.
The main advantage of the present device is that of minimizing the water and power consumption and achieving an optimal steam condensation in the shortest possible time regardless of the operating conditions of the machine.
A second significant advantage of this device is that of having a simple structure that is easily applicable to any industrial dishwasher. This device can therefore also be applied as an upgrade on an existing machine without requiring particular changes to the structure of the machine and/or to the arrangement of the components thereof.
Further advantages and characteristics of the device according to the present invention will become apparent to those skilled in the art from the following detailed description of some embodiments thereof with reference to the annexed drawings wherein:

Fig.1 is a diagrammatic side view of a dishwasher comprising a device according to the invention, that shows the path of the moist air recirculated between the wash tank and the condensing device as well as the water recirculation within the latter;
Fig.2 is a diagrammatic rear view showing a first embodiment of the condensing device of said dishwasher;
Fig.3 is a diagrammatic rear view showing a second embodiment of the condensing device of said dishwasher; and
Fig.4 is a diagrammatic rear view showing a third embodiment of the condensing device of said dishwasher.

Referring to said figures, there is seen that a device according to the invention conventionally includes a condensation chamber 1 with relevant inlet 2 and outlet 3 ducts that form the recirculation circuit of the moist air (indicated by the arrows) coming from the wash tank 4 of the dishwasher in which the device is introduced. The air circulation is guaranteed by a fan 5 that can be positioned upstream from (as in Fig.1) or downstream from the condensation chamber 1 depending on the space requirements of the dishwasher in which it is installed.
A water pipe 6 connected to the water mains system and provided with a valve 7 feeds a plurality of spraying nozzles that make up a "shower" system 8 arranged at the top of chamber 1. The water sprayed by nozzles 8 and the condensed steam are discharged from chamber 1 through a drain pipe 9 that conveys them to a water heater 10 where they will be heated for use in the following rinse. The amount of water loaded in the device is monitored by a level sensor (not shown) such as a system with a pressure switch, float or magnet that is operatively connected to a control unit (not shown) that controls also the opening and closing of valve 7 and the operation of fan 5.
The novel aspect of the present device, as mentioned above, lies in the presence of a recirculation pump 11 that draws the condensation water from the base of chamber 1 and returns it to shower 8 at the top of said chamber 1 through a recirculation duct 12. It should be noted that in order to maintain a minimum water level in the condensation chamber 1, necessary for the correct functioning of the recirculation pump 11, the drain 9 that conveys the water to the water heater 10 is arranged at a certain distance from the bottom of chamber 1 so as to act as an overflow pipe.
In this way, it is possible to load only the exact amount of water required for the following rinse and use it several times until a sufficient condensation of the steam present in the moist air coming from the wash tank 4 is achieved. Furthermore, the high flow rate guaranteed by pump 11, higher than the flow rate due to the mere pressure of the water mains system to which pipe 6 is connected, allows to feed shower 8 with an amount of water such as to condense very quickly the steam present in the moist air thus allowing to reduce the duration of the operating cycle.
In this respect it is to be noted that it is possible to calculate theoretically the operating time of the condenser in nominal conditions, but due to the above-mentioned variability of the amount of steam to be condensed it is preferable to provide one or more sensors that allow to precisely determine said operating time.
Therefore it is preferable to arrange in the air recirculation circuit, typically in the outlet duct 3 but possibly also upstream from the condensation chamber 1, a thermal probe (not shown) that is operatively connected to the control unit so as to provide a feedback about the condensation action carried out in chamber 1. In practice, said probe detects the temperature of the air and transmits it to the control unit which can thus control the activation of fan 5 and pump 11 taking into account the fact that a temperature higher than expected indicates an insufficient condensation and therefore it is necessary to extend the operating time of the condenser and vice versa a temperature lower than expected indicates that it is possible to anticipate the end of the condensation phase.
It is clear that the comparison between the detected temperature and the expected temperature, that takes place in the control unit, will cause an intervention on the duration of the condensation phase only if the difference between said temperatures is greater than a minimum pre-set threshold. The thermal probe may obviously be of any type suitable for the purpose, and in order to further optimize the control and effectiveness of the condensing device the probe may be a thermo-hygrometric probe that detects not only the temperature but also the humidity of the outgoing air, or a separate hygrometric probe can be combined with the thermal probe or even used instead of the latter.
As to the possible alternatives of the hydraulic circuit that supplies the condensation water, in the first embodiment illustrated in Fig.2 the pipe 6 supplying the mains water extends up to an air break 13 from which a connection pipe 14 conveys the water to the base of the condensation chamber 1 where pump 11 sends it to shower 8 through duct 12. It should be noted that air break 13 is provided for compliance with the hygienic norms required in some countries, but its presence is not indispensable for the operation of the condenser.
In fact in the second embodiment illustrated in Fig.3 pipe 6 is connected directly to the base of the condensation chamber 1, whereas in the third embodiment illustrated in Fig.4 pipe 6 is connected directly to shower 8 at the top of the condensation chamber 1, whereby in both cases the water is loaded without passing through the air break 13.
It is clear that the embodiments of the device according to the invention described and illustrated above are just examples susceptible of various modifications. In particular, the shape, size and arrangement of the condensation chamber 1 and of the ducts/ pipes 2, 3, 6, 9, 12 and 14 can be varied according to the needs, same as the type and exact position of pump 11 as long as it is capable of recirculating the water in the condenser, as well as the possible thermal and/or hygrometric probe as long as it is arranged in the air recirculation circuit.
It should also be noted that although the dishwasher illustrated in Fig.1 is an undertop front-load dishwasher, the above-described condensing device can be applied to other types of machine, such as a hood-type dishwasher or a washing and disinfecting machine, through a simple adaptation of the size and arrangement of the components and/or of the type of circuit that is within the knowledge of a person skilled in the art.

Claims

Steam condensation device comprising a condensation chamber (1) with relevant inlet (2) and outlet (3) ducts that form a circuit for the recirculation of moist air coming from a wash tank (4) of an industrial dishwasher or the like, a fan (5) suitable to guarantee the air circulation in said recirculation circuit, a plurality of spraying nozzles (8) arranged in said condensation chamber (1) and fed through a water pipe (6) connected to the water mains system and provided with a valve (7), a level sensor suitable to detect the amount of water loaded into the device, as well as a control unit operatively connected to said fan (5), to said valve (7) and to said level sensor, characterized in that it further includes a recirculation pump (11) that draws water from the bottom of the condensation chamber (1) and sends it to said plurality of spraying nozzles (8) through a recirculation duct (12), said control unit being operatively connected also to said recirculation pump (11).
Device according to claim 1, characterized in that it further includes a drain pipe (9) that connects the condensation chamber (1) to a water heater (10), said drain pipe (9) branching out from the condensation chamber (1) at a distance from the bottom sufficient to maintain therein a minimum water level necessary for the correct functioning of the recirculation pump (1).
Device according to claim 1 or 2, characterized in that it further includes at least a thermal probe and/or a hygrometric probe arranged in the moist air recirculation circuit, preferably in the outlet duct (3), the control unit being operatively connected also to said thermal probe and/or hygrometric probe.
Device according to claim 3, characterized in that it includes a thermal probe and a hygrometric probe integrated into a single probe.
Device according to any of the preceding claims, characterized in that the pipe (6) supplying the mains water extends up to an air break (13) from which a connection pipe (14) conveys the water to the base of the condensation chamber (1).
Device according to any of claims 1 to 4, characterized in that the pipe (6) supplying the mains water is connected directly to the base of the condensation chamber (1).
Device according to any of claims 1 to 4, characterized in that the pipe (6) supplying the mains water is connected directly to the plurality of spraying nozzles (8).
Industrial dishwasher or washing and disinfecting machine, characterized in that it includes a steam condensation device according to any of the preceding claims.