Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
  • F28F13/06—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media
  • F28F13/10—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media by imparting a pulsating motion to the flow, e.g. by sonic vibration

Definitions

• the present invention relates to a method and an apparatus for enforced heat transmission between a body, solid or liquid, and an ambient gas.
• the enforced he transmission is achieved in that the gas is set in oscillatory motion which is genera by a standing sound wave of low frequency, and in that the body is placed in that p of the sound wave where the oscillatory motion is greatest.
• a fundamental problem in heat transmission for example from a warm body to an flow enveloping the body, is that the transferred thermal effect per surface unit fro the body to the gas flow will be slight at low gas flow rates.
• high gas flow rates are required, which implies that a large air flow be necessary.
• the temperature rise in the air will be sli
• the large flow entails that cooling will be expensive and, in consequence of the sli temperature rise, the energy in the heated air can seldom be utilized!
• the object of the present invention is to solve the above-mentioned problem and to realize a method and an apparatus for transferring high thermal effect per surface u from a body to ambient gas. Instead of increasing the heat transmission by aspirati the gas over the surface of the body at high speed, the enforced heat transmission i achieved by imparting to the ambient gas a low frequency oscillation.
• the wire When the steel wire leaves the rolling mill, it is at a temperature of approx. 850 °C must by cooled to 300 °C in order to be handled. A number of different processes a currently employed for such cooling.
• the wire is laid out i spiral bights of approx. 1 m diameter on a roller conveyor where the wire bights are conveyed forwardly at a speed of approx. 0.5 m/s, at the same time as cooling air i blown onto the wire with the aid of a plurality of large fans placed beneath the roller conveyor.
• a cooling distance of approx. 60 m is required.
• Fig. 1 shows a solid body in a standard airflow
• Fig. 2 shows a solid body in an air flow which has been exposed to an infrasound field
• Fig. 3 shows an installation for cooling of metal wire using low-frequency so
• Fig. 4 shows a plant for cooling cement clinker using low-frequency sound. 5
• Fig. 1 shows a solid b at a temperature T which is exposed to an air flow.
• a particle in the air flow is mar 0 as a dot and the position of the air particle at various points in time is marked by t- j
• the temperature of the air flow is T-
• Fig. 2 shows the same solid body when it has been expos to the same air flow, but under the influence of infrasound.
• the position of the air particle at different points in time is also marked by t- j -t here.
• 5 each air particle which passes the solid body, because of the pulsating air current * • generated by the low frequency sound, will pass not just once but a plurality of tim If the body is at a higher temperature than the air flow, the air particle will absorb m and more heat each time it passes the solid body, and the temperature of the body will be correspondingly reduced. Enforced heat transmission will thus be obtained.
• the velocity of the oscillating motion of gas is great, while the pressure variations, the so-called sound pressure, are slight.
• the pressure variations are gre while the velocity of the oscillating motion is low.
• both the particl velocity and the sound pressure will thus vary with time and, under ideal conditions will describe a sinusoidal oscillatory motion.
• the highest value of the particle veloci and the sound pressure, respectively, is indicated by the amplitude of each respect oscillatory motion.
• the amplitude of the partice velocity assumes a maxim value, i.e.
• the particle velocity anti-node has a so-called particle velocity anti-node, at the same time as the amplitude of the sound pressure assumes a minimum value, i.e. has a so-called sound pressure node. It is desirable, in accordance with the foregoing, that the particle velocity assumes high a value as possible in order that maximum enforced heat transmission be obtained. In a standing sound wave, there may be several positions where the particle velocity amplitude assumes its maximum level.
• the amplitude of the particle velocity has a maximum only at one point, in order to obtain as high an enforced heat transmission as possible, the surface from whence the heat transmission is to take place should therefore be sited at a position as close to the particle velocity anti-node as possible.
• an enforced heat transmission between a body, solid or liquid, and a gas, as shown in Fig. 2 is realized in that a standing, low-frequency sound wave is generated in one or more sound resonators
• the term low-frequency sound is here taken to mean sound at a frequency of 50 H lower.
• frequencies above 50 Hz are less interesting is that a close half-wave resonator has such small dimensions at high frequencies that the apparatus will be uninteresting from the point of view of capacity. Since possibly disruptive sound fades at lower frequencies, a frequency of 30 Hz or lower should preferably be used.
• the sound resonator is preferably of a length corresponding to a half wavelength o the generated low-frequency sound, but other designs of the sound resonator are also possible.
• the sound wave is obtained in that air pulses are generated by a so-called exigator located at a sound pressure anti-node in the resonator.
• the ter exigator is here employed to indicate that part of a generator for iow-frequency sou which generates a particle velocity in one point in a resonator where a high sound pressure prevails, see for example Swedish patent No. 446 157 and Swedish pate applications Nos. 8306653-0, 8701461-9 and 8802452-6.
• a particle velocity anti-node will occur simultaneously with a sound pressure node and, at that point, the resonance tube may be open.
• the surface fro which the above-considered heat transmission is intended to take place is advanc through this opening.
• the surface is then located in a particle velocity anti-node of the above-mentioned standing low-frequency sound wave.
• a stationary air current flows through the resonator tube, one portion of the air curr deriving from the driving air which emanates from the exigator, and its other portio from the air which flows in at the opening through which the heat transmission surf is advanced. It is also possible to use a special cooling air fan.
• Low-frequency sound is generated by one or more low-frequency sound generator consisting of an exigator part and a resonator part.
• a standing sound wave occurs which shows sound pressure nodes where the sound pressure is at its minimum.
• the resonator tube has an opening where these nodes are located, the opening being designed such that the wire may pass through the resonator tube and thereby be subjected to infrasound-influenced cooling air.
• Fig. 3 shows in greater detail a plant in which steel wire, which is to be cooled, is allowed to pass across a cooling table 1 where it is subjected to low-frequency sou Acoustically, the plant consists of a virtually closed system.
• the steel wire is laid o on a roller conveyor or other conveyor belt in accordance with standard usage and advanced across the cooling table at uniform speed in a plane perpendicular to the plane of the paper.
• Two tube resonators 2, 3 are disposed above the table, their o ends discharging above the table.
• the resonators are preferably of a length corresponding to a quarter of a wavelength of the generated sound.
• exigator 4 At the other en of each respective resonator, there is a so-called exigator 4, 5.
• This exigator may b of the type which is described in Swedish Patent application No. 8802452-6. Together with the resonator 2, 3, the exigator 4, 5 forms a low-frequency sound generator.
• Both of the exigators 4, 5 are jointly driven by a motor by means of one the same driving shaft in such a manner that a phase lag of 180° is obtained betw the exigators when these operate. Since the exigators operate in counterphase, a standing sound wave of the same frequency will be generated in each resonator.
• two resonators of quarter-wave type thereby together form one resonator of half-w type of the same resonance frequency as the resOnance frequency of the individu resonators and one single common standing sound wave is generated.
• Cooling air is supplied with the aid of a cooling air fan 12 which conveys the coolin air to the cooling table via two ducts 7 and 8 located between the two resonators.
• Each one of these ducts has a lower emanation in the wall which is common to ea respective resonator tube, and this emanation is located in the lower region of eac respective resonator tube.
• a nose portion 9 is located between the lower regions o the two resonator tubes and mainly beneath the discharge of the cooling air duct i each respective resonator tube, the nose portion preferably being designed as a cross-section of a cone or other similar configuration. This nose portion extends al and between the lower parts of the resonator tubes as a bulge-like projection.
• the of the conical nose portion is secured in the wall which is common to both of the cooling air ducts and the curved portion constitutes an extension of this wail which thereby, is divided into two walls. With the aid of the nose portion, favourable cooli air flow characteristics will be obtained into the lowermost portion of the resonator tubes where the air is exposed to the low-frequency sound.
• the wall which is common to each respective cooling air duct and resonator tube may, on it inner side located within the cooling air duct, be provided with a curved plate 10, 1
• the nose portion 9 has a substantially planar underside which is turned to face the cooling table, this having the effect that the cooling air oscillates reciprocally along underside of the nose portion and thus a greater portion of the cooling table and th steel wire located thereon is exposed to cooling air than would have been the case without the nose portion.
• th _ steel wire which is advanced in recumbent spiral bights is exposed to more powerf cooling at the outer edges of the table where the wire is more closely wound and, consequently, requires greater cooling effect in order for the wire to be of uniform quality.
• the heated cooling air is removed with the aid of a fan 13 which, for example, may located beneath the cooling table, and its thermal effect content may be extracted employed for various purposes, for example in that tt is allowed to pass through a heat exchanger.
• water may be sprayed into the coolin air in the proximity of the pertinent cooling region.
• cooling air instead of using cooling air to dispose of the thermal effect emitted from the bodies convection surface, such as a pipe system containing a flowing cooling agent such cooling water, ammonia, freon or similar, may be installed in the proximity of the cooling area.
• a pipe system containing a flowing cooling agent such cooling water, ammonia, freon or similar
• the heat given off by the bodies can also be utilized.
• Fig. 4 shows one embodiment for enforced cooling of, for example, hot cement clinkers 20 which are advanced on a conveyor belt.
• This plant does not constitute acoustically closed system. Otherwise, the plant operates in the same manner as t plant for cooling steel wire, with the difference that the two resonators 21 , 22, each with their respective exigator 23, 24, and the motor 25 are installed beneath the conveyor belt which advances the clinkers.
• the surface which i be subjected to heat transmission is placed in the particle velocity anti-node, this constitutes an obstacle for the standing sound wave.
• the cement clink are a considerably greater obstacle than the steel wire in Fig. 3.
• the impedance becomes excessive, this is expressed in that the sharpness of the resonance of the resonators becomes poorer, which implies that the relationship between the amplitude of the particle velocity in the anti-node and the node respectively is reduced. It will be understood that, in a situation implying large losses, there is no reason to generate the standing sound wave with the aid of a long resonance tube. By placing the exigator closer to the particle velocity anti-node, the length of the resonance tube may be shortened.
• An open resonator as in the embodiment described above implies that the amplitud of the particle velocity declines drastically when the resonator opens outwardly, i.e. its opening. Even though, in the case using a quarter wave resonator, there is still particle velocity anti-node at the open end of the resonator, this may be difficult to
• the sound volume velocity is not affected by the diamet of the resonator but retains its sinus wave form, which in periodicity coincides with particle velocity amplitude. It may therefore be more appropriate and simpler to identify that region where the greatest heat transmission may be obtained as that a where the volume velocity has a anti-node.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Cookers (AREA)

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• 1988
  • 1988-11-01 SE SE8803974A patent/SE463786B/sv not_active IP Right Cessation
• 1989
  • 1989-10-30 CA CA 2001721 patent/CA2001721A1/en not_active Abandoned
  • 1989-10-31 CN CN 89108352 patent/CN1022440C/zh not_active Expired - Fee Related
  • 1989-10-31 JP JP51112089A patent/JPH04501456A/ja active Pending
  • 1989-10-31 AU AU44293/89A patent/AU4429389A/en not_active Abandoned
  • 1989-10-31 WO PCT/SE1989/000619 patent/WO1990005275A1/en not_active Application Discontinuation
  • 1989-10-31 EP EP19890911916 patent/EP0441816A1/en not_active Withdrawn

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