Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B1/00—Methods of steam generation characterised by form of heating method
  • F22B1/28—Methods of steam generation characterised by form of heating method in boilers heated electrically
  • F22B1/282—Methods of steam generation characterised by form of heating method in boilers heated electrically with water or steam circulating in tubes or ducts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41H—ARMOUR; ARMOURED TURRETS; ARMOURED OR ARMED VEHICLES; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL
  • F41H9/00—Equipment for attack or defence by spreading flame, gas or smoke or leurres; Chemical warfare equipment
  • F41H9/06—Apparatus for generating artificial fog or smoke screens

Definitions

• the present invention refers to a device for generating fog and to an operating method of such device .
• the present invention refers to a steam generating system, through electric heating of a liquid circulating in pipes or ducts.
• Fog-generating apparatus for theft prevention, entertainment, screening, defence purposes and the like, pressurized or connected downstream to at least one pump and a heat exchanger to allow taking to the vapour phase the liquid contained in the tank.
• the size of the thermal exchange surface of the heat exchanger depends on the value of the desired thermal power necessary to allow forming the fog.
• Patent US5706389A deals with and solves the problem of the heating time of the heat exchanger through a device for evaporating liquids comprising at least one section composed of an alloy of about 55% of copper and about 45% of nickel, the remaining part of such heat exchanger being of stainless steel.
• such heat exchanger is a round tube with an internal diameter from 0.3 to 1 mm, with the wall of such tube having a thickness from 0.1 to 0.3 mm and a length from 120 to 1000 mm.
• the device disclosed in patent US5706389A is unsuitable for anti-theft applications.
• Patent US5706389A deals with ahd solves the problem of measuring the temperature of the heat exchanger through a portion of the heat exchanger designed to operate as a heating resistance having a low temperature coefficient. Such portion is directly used as measuring resistor of the temperature of the heat exchanger connected in parallel to an electronic unit, preferably arranged between the heat exchanger and the supply source. The electronic unit output is directly connected to the supply source. This implies having to use as measuring resistance a particularly costly material, which can be found with difficulty in tubes, such as constantan.
• Object of the present invention is solving the above prior art problems, by providing a device for generating fog capable to operate through the measure of an electric potential difference to thermally check the pressurized fluid before of vaporizing the pressurized fluid.
• a further object of the present invention is providing a device for generating fog capable of continuously operate, above all in case of an electric current interruption.
• a further object of the present invention is providing a device for generating fog in which it is possible to increase the latency time without electric supply.
• a further object of the present invention is providing a device capable of substantially cancelling the self-consumption during the stand-by pauses, in order to save energy.
• Another object of the present invention is providing an operating method of a device for generating fog through which it is possible to control the heating time of the heat exchanger in order to reach the standby temperature in one, two seconds, in addition to control the temperature value of a device subjected to sudden temperature gaps .
• a further object of the present invention is providing an operating method of a device for generating fog through which it is possible to control and optimize the temperature distribution.
• Figure 1 shows an operating diagram of an embodiment of the device for generating fog according to the present invention
• Figure 2 shows an axonometric view of some components of an embodiment of the device for generating fog according to the present invention
• - Figure 3 shows a first connection diagram of the embodiment of the device of Figure 1;
• Figure 4 shows a second connection diagram of the embodiment of the device of Figure 1;
• Figures 5, 6 show an axonometric view of an assembly of an embodiment of the device for generating fog according to the present invention.
• a device for generating fog 1 comprises at least one heat exchanger 10 electrically heated to be able to vaporize at least one pressurized fluid, pressurizing means 20 to be able to send the fluid from at least one tank 30 towards the heat exchanger 10, at least one electronic unit 40 to control the temperature of the heat exchanger 10 and the operation of the pressurizing means 20.
• the heat exchanger 10 comprises tubular elements in contact with the pressurized fluid, each tubular element being subjected to an electric potential difference to thermally check the pressurized fluid, before and during the vaporizing step of the pressurized fluid.
• tubular elements of the heat exchanger 10 comprise at least one thin wall composed of at least one first layer of structurally resisting material and of at least one second layer of material having a high electric conductivity to obtain an optimum value of equivalent electric resistance, without having to increase the thermal mass of the heat exchanger 10.
• the tubular elements of the heat exchanger 10 comprise at least one thin wall made of titanium, the titanium being at the same time a structurally resisting material and an optimum electric conductor to obtain an optimum value of equivalent electric resistance, without having to increase the thermal mass of the heat exchanger 10.
• the heat exchanger 10 is composed of a pair of sections 11 and 12 of tubular elements, each section of such pair of sections 11 and 12 being supplied with a proper electric voltage and connected to a control unit 41 and 42 to allow controlling the operation of the pressurizing means 20, in order to keep constant the lower of the temperatures detected between those of the control units 41 and 42 in order to exploit the maximum absorbed power.
• the heat exchanger 10 can be made of a single section of tubular elements.
• each of such sections of tube 11 and 12 comprises at least one portion 111, 121 adapted to operate as a resistor to allow computing the weighed mean of the steady state temperature of the respective section of tube
• each of such sections of tube 11 and 12 comprises at least one portion 112, 122 composed of a tubular serpentine adapted to operate as fluid super-heater .
• the sections of tube 11 and 12 are connected in parallel through the portions 111, 121 operating as resistor, and in series through the portions 112, 122 operating as fluid super-heater, to allow vaporizing high fluid flow rates.
• the sections of tube 11 and 12 are connected in series through the portions 111, 121 operating as resistor, and in series through the portions 112, 122 operating as fluid super-heater.
• each of such sections of tube 11, 12 is electrically connected to at least one accumulator 60 of the electrochemical type and a low electric voltage to allow almost instantaneously heating the heat exchanger 10 and basically cancel the internal losses of heating energy.
• the first 41 or second 42 control unit shows an estimation of the current delivered by the accumulator 60.
• Such estimation is computed through the value of the voltage drop measured in at least one of such portions 111, 121 to allow knowing the status of the accumulator 60, in terms of electric charge, performance drop due to ageing, possible need for a replacement.
• such at least one portion 111, 121 is kept cooled. According to a preferred configuration, such at least one portion 111, 121 is cooled by the fluid circulating in the device 1.
• such electronic unit 40 is programmed to allow substantially cancelling the self-consumption during the operating pauses, in order to save energy.
• the present invention further deals with an operating method to allow optimizing the heating times and maximizing the thermal power transferred to a fluid of a device for generating fog 1 as previously described, such method comprising the following steps:
• the device for generating fog of the present invention allows obtaining the stated objects.
• the heat exchanger is dimensioned with a big thermal mass and thermally insulated from the external environment.
• the ratio between the thermal capacity and the thermal resistance, in this type of apparatuses generates a certain time constant, for which, starting from the instant in which the electric supply drops, the expected performances can quickly decay till they stop.
• an energy self-consumption appears, caused by unavoidable losses of thermal insulation.
• Such self-consumption can be a strong economic loss and this practice can result in a yearly cost equal to 25% of the purchase value of an apparatus having a high class and equal to half the purchase value of a machine with a lower insulation class, namely a machine which absorbs much more energy.
• Another solved object of the present invention is the functionality time without electric supply.
• the functionality time is necessarily limited and the risk of theft with "preventive disconnection" is not wholly cancelled if it is not possible to timely intervene in case of lack of current.
• the device of the present invention allows storing Energy, instead of in a thermal mass to be kept hot and thermally insulated, by accumulating energy in an accumulator of the electrochemical type, preferably with acid lead, and by quickly extracting it upon use.
• Such quick extraction deemed critical and at the same time indispensable for an anti-theft application, makes it necessary to minimize the thermal mass of the exchanger, by taking in temperature the exchanger itself before inserting therein the fog-generating fluid. It goes without saying that the time constant of the system at start-up is directly proportional to the thermal mass/inserted power ratio.
• the apparatus consists in a tubular serpentine made of conducting material, adapted to operate as a resistor.
• a tubular serpentine made of conducting material, adapted to operate as a resistor.
• the relevant currents are on the order of hundreds to thousands of Amperes.
• the fog generating fluid is injected through a pump from an atmospheric tank, namely through a valve with fixed or variable opening from a pressurized tank. Passing in the tubular serpentine, the fluid is vaporized, taken to the saturated steam phase and delivered to the environment through a suitable nozzle.
• the high emission speed makes steam divided into small condensing centres which, by getting cooled due to the contact with the colder air, condensate into very small drops which will scatter light, causing the so-called white-out phenomenon, with absolute fog, protecting the environment.
• the heating time of the heat exchanger is a critical element to be able to make an efficient anti-theft device.
• the ideal situation would be that the heat exchanger is made in order to reach its standby temperature of regime in one, two seconds.
• This objective can be reached by optimizing the following parameters: total thermal mass of the heat exchanger - so that, upon increasing the thermal mass, necessary time and energy must increase - and electric resistance of the serpentine in order to be perfectly suited to the battery impedance; structural resistance of the apparatus subjected to a fluid pressure.
• the first obvious choice could be stainless steel, a mechanically resistant metal, which can technologically be made in resisting tubes but with a small thickness, in order to minimize the thermal capacity, but unfortunately equipped with a too high resistivity for the application.
• this solution consists in making the tubular serpentine of stainless steel with the technologically minimum thickness possible to obtain a suitable mechanic resistance; whichever other metal equipped with enough resistivity and mechanical resistance can be used as well for such purpose, and afterwards coating through galvanic processes or vacuum coating such tubular serpentine with a thin layer of an optimum conducing metal, for example: copper, gold, etc. In this way, it is possible to regulate the equivalent electric resistance of the serpentine till the optimum value is obtained without having to increase the exchanger mass.
• this solution consists in increasing the supply voltage till the necessary power is reached in a tubular serpentine made of stainless steel, copper or whichever other material.
• an optimum compromise can be found for any material equipped with enough mechanical resistance, with the risk however of having to manage dangerous voltages, which are costly to reach with the batteries, in case of a high resistivity metal.
• the same is valid for the opposite case, namely a metal with low resistivity, in cui a current of several thousands of Amperes has to be managed.
• the tubular serpentine is preferably made of titanium, a shape of a tube with thin wall capable of reaching 12 Volt with a warm up time shorter than three seconds.
• an optimum material for the serpentine could be made through layering ordinary metals with complementary electric and physical characteristics, such as for example stainless steel, copper, gold.
• thermocouple does not allow measuring the temperature of a tubular serpentine which therefore quickly changes.
• the thermometer mass being high with respect to the local mass of the tubular serpentine would affect the measure too much.
• the measure would be performed in any case in a spot and with a delay given by the time constant caused by the thermometer mass.
• the choice has been measuring the resistance of the tubular serpentine itself with a volt-ampere method, comparing it with the voltage drop on a small load in series composed of a sample element, in this case a tubular portion of the heat exchanger adapted to operate as a resistor.
• Another problem solved by the present invention deals with controlling and optimizing the temperature distribution.
• several phenomena occur, du to the phase variation of the fluid, or depending on cavitation due to excess of inserted power, local boiling only on the surface, which creates a layer of insulating gas between the wall of the tubular serpentine and the liquid.
• Such phenomena can change the process of removing heat.
• the local temperature lowering under a higher absorption condition creates a local temperature lowering also of the tubular serpentine in that spot.
• This effect reduces the resistivity in the cooled section, the metals have a positive temperature coefficient of the resistivity, consequently linearly reducing the dissipated power in that section.
• This effect causes a positive reaction of the local system, which further cools the already cooled section.
• a device which tries in a single stage to obtain the complete vaporization can be locally unstable. To obtain the stabilization in this case, the thermal mass/device power ratio can be reduced.
• the exchanger can be divided into several tubular serpentines, each with one, preferably two, independent control ring.
• the operating method of the device of the present invention allows optimizing the heating times and maximizing the thermal power transferred to a fluid for generating fog.
• a control algorithm it is possible to optimize the warm-up times and maximize the power transferred to the fluid.
• each section of tube goes to its final temperature.
• fluid is inserted in a controlled way, starting from zero, till the first section of tube cannot keep any more the steady state temperature value. This point is the maximum flow that the device can support and manage.
• the pump speed is regulated in order to keep constant the temperature of the section of tube which cools first. In the other sections of tube, their temperature is self-regulated in order to keep it constant.
• a scheme suited to a device for generating fog with high flow-rate allows reducing the load losses through a preheating along sections of tube in parallel, when fluid is in its liquid phase, namely with more resistance to sliding and better thermal inertia, and through an overhearing along sections of tube in series, when the fluid tends to its overheated vapour phase.
• fluid slows down in the first ducts, by 1/n, where n is the number of ducts and accelerates next to the super-heater in series for the final evaporation, where the maximum flow speed is needed, to guarantee a more violent shot.
• a preferred configuration of the device for generating fog 1 of the present invention comprises:
• the tank 30 is a pressurized bag connected to pressurizing means comprising a valve, not shown.
• the tank 30 can be of the type connected to pressurizing means 20 comprising a pump;

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• Control Of Resistance Heating (AREA)
• Spray Control Apparatus (AREA)

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Citations (4)

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• 2016
  • 2016-04-11 IT ITUA2016A002466A patent/ITUA20162466A1/it unknown
• 2017
  • 2017-03-24 DK DK17721218.0T patent/DK3443263T3/da active
  • 2017-03-24 WO PCT/IT2017/000059 patent/WO2017179080A1/en not_active Ceased
  • 2017-03-24 ES ES17721218T patent/ES2922542T3/es active Active
  • 2017-03-24 EP EP17721218.0A patent/EP3443263B1/en active Active

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