Acoustic drying

Acoustic drying is of potentially great commercial importance. Ultrasonically enhanced drying can be carried out at lower temperatures than conventional methodology which reduces the probability of oxidation or degradation in the... 

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Borisov Yu Ya, Gynkina NM. Experiments on acoustic drying. Ultrazvukovaiya Tekh-nika 5(3) 38, 1967 (in Russian). 

Borisov Yu Ya, Gynkina NM. Acoustic drying. In Rosenberg LD, ed. Physical Principles of Ultrasonic Technology. Vol. 2. New York Plenum Press, 1973, pp 381-473. 

Eairbanks HV. Acoustic drying of ultraflne coal. Mining Eng. 22(12) 49-50, 1970. 

Marziniak R. Kinetic of acoustic drying process. Acustica 27 122-131, 1972 (in German). 

Mashkova TL. Acoustic drying. In Application of Ultrasonics in Processes of Chemical Engineering. Moscow TINTIEPP Publishing House, 1960, pp 196-201 (in Russian). 

Muralidhara HS, Ensminger D. Acoustic drying of green rice. Drying Technology 4(1) 137-143, 1986. 

Da Mota, V. M., Palau, E 1999. Acoustic drying of onion. Drying Technol. 17 855-867. 

Screw compressors of the dry type generate high frequency pulsations that move into the system piping and can cause acoustic vibration problems. These would be similar to the type of problems experienced in reciprocating compressor applications, except that the frequency is higher. While volume bottles will work with the reciprocator, the dry type screw compressor would require a manufacturer-supplied proprietary silencer that should take care of the problem rather nicely. 

Academic des Sciences, 224 Accelerometers, 349 Accumulators, 317 Acoustic Velocity, 26, 39 Adiabatic, 30 Adiabatic efficiency dry, helical, 101 sliding vane, 126 Adiabatic exponent for air-vapor mixtures, 494 Adiabatic head, 32 Adiabatic head... 

Recently, dry wire-pipe ESPs are being cleaned acoustically with sonic horns (Flynn, 1999). The horns, typically cast metal horn bells, are usually powered by compressed air, and acoustic vibration is introduced by a vibrating metal plate that periodically interrupts the airflow (AWMA, 1992). As with a rapping system, the collected particulate slides downward into the hopper. The hopper is evacuated periodically, as it becomes full. Dust is removed through a valve into a dust-handling system, such as a pneumatic conveyor, and is then disposed of in an appropriate marmer. 

An effective and environmentally friendly acoustic barrier consists of a framework of woven, freshly cut willow, filled with soil, into which the willow stems root. Variations include a soil-filled framework of dried willow, in which ground-cover plants are established. Dense, compressed reed walls designed to reduce noise are also available. 

Solids usually have larger ultrasonic velocities and acoustic impedance, than liquids, which have larger values than gasses. Air has a very low acoustic impedance compared to liquids or solids which means that it is difficult to transmit ultrasound from air into a condensed material. This can be a problem when ultrasound is used to test dry materials, e.g., biscuits or egg shells. A small gap of air between an ultrasonic transducer and the sample to be tested can prevent ultrasound from being transmitted into the material. For this reason coupling materials (often aqueous or oil based) can be placed between the transducer and sample to eliminate the effects of the air gap, or alternatively soft-tip ultrasonic transducers can be used. 

Interestingly, the presence of reverberation is clearly preferred for most sounds, particularly music. Music without reverberation sounds dry and lifeless. On the other hand, too much reverberation, or the wrong kind of reverberation, can cause a fine musical performance to sound muddy and unintelligible. Between these extremes is a beautiful reverberation appropriate for the music at hand, which adds fullness and a sense of space. Consequently, a number of concert halls have built reputations for having fine acoustics, based on the quality of the perceived reverberation. 

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