Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
1999-08-12
2001-09-18
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S200000, C134S113000, C134S16600C, C134S184000
Reexamination Certificate
active
06290778
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of sonic cleaning of surfaces, and more particularly to the field of cleaning chiller heat exchangers using sonic waves.
BACKGROUND OF THE INVENTION
It is known that the buildup of deposits and contaminants on the surface of heat exchangers reduces their efficiency, and that the removal of these deposits restores efficiency.
In the field of refrigeration and chillers, the evaporator heat exchanger is a large structure, containing a plurality of parallel tubes, within a larger vessel comprising a shell, through which refrigerant flows, absorbing heat and evaporating. Outside the tubes, an aqueous medium, such as brine, circulates and is cooled, which is then pumped to the process region to be cooled. Such an evaporator may hold hundreds or thousands of gallons of aqueous medium with an even larger circulating volume. The known process for cleaning the aqueous portion these heat exchangers involves flushing an aqueous cleaning fluid around the heat exchange pipes, hoping to dissolve or dislodge deposits. More aggressive cleaning involves dismantling the shell of the evaporator and manually cleaning the refrigerant tubes by scrubbing. This cleaning process is thus cumbersome and inefficient.
U.S. Pat. Nos. 4,437,322; 4,858,681; 5,653,282; 4,539,940; 4,972,805; 4,382,467; 4,365,487; 5,479,783; 4,244,749; 4,750,547; 4,645,542; 5,031,410; 5,692,381; 4,071,078; 4,033,407; 5,190,664; and 4,747,449 relate to heat exchangers and the like.
The operation of various pipes and tubes and vessels including heat exchangers is routinely impeded by the buildup of sedimentation in and around heat exchange surfaces and components causing restriction of flow and impediment of enthalpy or both. Devices using acoustic-type energy to resist or remove sedimentation have been suggested. In such devices, a portion of energy is imparted to tubes and other walls encountered and to molecules and particles in suspension or solution in the fluid. If the imparted energy density is less than the deposition energy of suspended or dissolved particles and/or the binding energy of deposited particles, deposition restrain and/or dislodgment of sediment particles will be less efficient in accordance with the laws of statistics. If the imparted energy density exceeds such sedimentation rate and/or binding energy, sedimentation will be prevented and existing sediment more rapidly dissipated.
The issue then becomes effectively and efficiently imparting the acoustic waves. The efficiency of prior art acoustic devices is limited, and, moreover, there is a limit to the power which can be applied to the transducer because of the so-called cavitation effect in the fluid and risk of damage. While composite wave devices have been suggested, these utilize resonance effects and produce resultant standing wave patterns which may leave areas untreated and subject to load and configuration variances.
U.S. Pat. Nos. 2,987,068; 3,640,295; and 3,295,596, expressly incorporated herein by reference, as well as British Pat. Nos. 1,456,664 and 1,385,750 each teach ultrasonic cleaning apparatuses which include a plurality of transducers affixed to a cleaning vessel or container for effecting ultrasonic cleaning of items inserted within the vessel or container. U.S. Pat. No. 3,240,963, expressly incorporated herein by reference, teaches a plurality of transducers movably mounted within a vessel for cleaning items disposed therein. Ultrasonic transducers are shown in U.S. Pat. No. 2,716,708, expressly incorporated herein by reference, and British Pat. No. 1,282,552. U. S. Pat. No. 3,371,233 discloses a multifrequency ultrasonic cleaning apparatus. U. S. Pat. No. 3,638,087, expressly incorporated herein by reference, discloses a gated power supply for sonic cleaners.
High pressure, low-frequency shock waves are used to unplug blocked pipes (Simon, U.S. Pat. No. 4,974,617, expressly incorporated herein by reference; Coon et al., U.S. Pat. No. 4,551,041, expressly incorporated herein by reference), and clean corrosion products and sedimentation from the interior walls of heat exchanger tubes (Scharton et al., U.S. Pat. No. 4,645,542, expressly incorporated herein by reference). Such techniques are, however, not suitable for cleaning the interior surfaces of elongated tubes for the purpose of degreasing or cleaning, due to the high pressures (up to 5,000 psi) of the shock waves and extended time periods required (1-24 hours).
It is known in the ultrasonic cleaning art that high peak or power bursts are necessary for aggressive cleaning or for cavitating liquids. The prior art provides various power burst controls for adjusting a duty cycle, amplitude and frequency of the transducer output, in addition to the pulse sequences and parameters.
U.S. Pat. No. 4,736,130, expressly incorporated herein by reference, relates to a multiparameter generator for ultrasonic transducers, which controls seven variables. These are: 1) the time duration of a power pulse train, which is followed by a 2) time period of no activity for degassing, 3) the time duration of individual power bursts during the power train period, 4) the time duration of periods of no activity between the individual power bursts, 5) the range of amplitude modulation of each power burst, 6) the mean transmitted frequency, and 7) a frequency modulation index.
In U.S. Pat. No. 4,398,925 Trinh et al., expressly incorporated herein by reference, relates to an ultrasonic transmitting apparatus for removing dissolved gas in a fluid. It is disclosed that the transmitted frequency is swept from 0.5 kHz to 40 kHz and that the ratio between the low and high frequency limit should be at least 10 times.
In U.S. Pat. Nos. 3,648,188, and 4,588,917, expressly incorporated herein by reference, relate to power oscillators with different resonant arrangements and positive feedback components to cause oscillation.
U.S. Pat. No. 4,864,547, expressly incorporated herein by reference, relates to a system for producing a soft start and means to vary the power to the transducer.
Several phase locked loop arrangements are described so that a resonant frequency of the transducer is locked onto by the drive electronics. U.S. Pat. No. 4,748,365, expressly incorporated herein by reference, is an example of this which describes means for searching for the load resonance point and then locking onto it.
U.S. Pat. No. 4,120,699, expressly incorporated herein by reference, relates to a method for acoustical cleaning of heat exchangers and the like.
U.S. Pat. Nos. 4,244,749 and 4,375,991, expressly incorporated herein by reference, relate to ultrasonic cleaning methods for heat exchangers.
U.S. Pat. No. 4,358,204, expressly incorporated herein by reference, relates to an ultrasonic method for cleaning ultraviolet lamps in a treatment chamber.
U.S. Pat. No. 4,366,003, expressly incorporated herein by reference, relates to a method for periodically cleaning out solid deposits from heat exchanger pipes.
U.S. Pat. No. 4,645,543, expressly incorporated herein by reference, relates to a method of pulse pressure cleaning the interior of heat exchanger tubes.
U.S. Pat. No. 4,750,547, expressly incorporated herein by reference, relates to a method for cleaning inner surfaces of heat-transfer tubes in a heat exchanger employing ultrasonic waves.
U.S. Pat. No. 4,773,357, expressly incorporated herein by reference, relates to a water cannon apparatus for cleaning tube bundle heat exchangers.
U.S. Pat. No. 4,974,617, expressly incorporated herein by reference, relates to a low frequency sonic method for clearing a liquid-filled pipe.
U.S. Pat. No. 4,991,609, expressly incorporated herein by reference, relates to an ultrasonic cleaning method.
U.S. Pat. No. 4,966,177, expressly incorporated herein by reference, relates to a method for ultrasonic cleaning of fuel rod tubes.
U.S. Pat. No. 4,972,805, expressly incorporated herein by reference, relates to a gas-pulse method and apparatus for removing foreign matter from heat exchanger tubesheets.
U.S. Pat. No. 5,076,854, expres
Chaudhry Saeed
Gulakowski Randy
Hudson Technologies Inc.
Milde Hoffberg & Macklin, LLP
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