Heat exchange – With means flexing – jarring or vibrating heat exchange surface
Patent
1991-06-18
1994-05-31
Davis, Jr., Albert W.
Heat exchange
With means flexing, jarring or vibrating heat exchange surface
165120, 34164, 34171, 34174, 34360, 34279, 62 63, F28F 1310
Patent
active
053160762
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and an arrangement for enforced heat transmission between an alimentary body, solid or liquid, and an ambient gas. In particular, the invention relates to heat transmission from relatively small solid alimentary bodies, which occur in large amounts, and where it is desirable to fluidize the alimentary bodies constituting a product flow in order to improve both the heat transmission and the motion of the alimentary bodies. The enforced heat transmission is achieved in that the ambient gas is set in oscillatory motion which is generated by a standing sound wave of low frequency and in that the alimentary bodies are placed in that part of the sound wave where the oscillatory motion is greatest.
DESCRIPTION OF THE BACKGROUND ART
A fundamental problem in cooling/freezing alimentary bodies, i.e. products intended as food for human beings or animal fodder, is that the transferred thermal effect per surface unit from the alimentary body to a gas flow enveloping the alimentary body will be low at low gas flow rates. In order to transfer large thermal effects, high gas flow rates are required, which implies that a large air flow will be necessary. At the same time, however, the temperature rise in the air will be slight. The large flow entails that cooling/freezing will be expensive and, in consequence of the slight temperature rise, the energy in the heated air can seldom be utilized.
Depending on, among other things, the feeding temperature of the alimentary bodies, their consistency, thickness etc., variations in transit time must be foreseen in order to achieve the desired outlet temperature of the alimentary bodies. The transmit time, i.e. the time during which the alimentary bodies are present in the cooling/freezing chamber, is generally controlled by the feed rate of the product flow, so that a low feed rate result in a longer transmit time than a high feed rate would.
It is previously known from V. B. Repin, "Heat exchange of a cylinder with low-frequency oscillations", Zhurnal Prikladnoi Mehaniki i Tekhnicheskoi, No. 5, pp. 67-72, September-October 1981, that heat transmission may be improved by generating a sonic field in the liquid. It is also previously known that it is advantageous if such a sonic field is of low frequency.
It will be obvious from the two parameters sound pressure and particle velocity in a sonic field that it is the particle velocity which provides the enforced heat transmission. It is also obvious that the heat transmission increases with increasing particle velocities. The reason why the prior-art method of employing low-frequency sound for heating or cooling of bodies has not hitherto enjoyed any practical importance is that there have not been any usable method or apparatus for generating sound with a sufficiently high particle velocity throughout the entire surface of the body intended to be cooled, or alternatively, heated.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above mentioned problem and to attain a method and an arrangement for achieving enforced heat transmission by transferring high thermal effect per surface unit from a alimentary body to ambient gas, especially for applications in which the alimentary body consists of a quantity of small solid alimentary bodies, for example granules or pellets or drops. Instead of increasing the heat transmission by passing the gas over the surface of the alimentary body at high speed, the enforced heat transmission is achieved by imparting to the ambient gas a low frequency oscillation. For the purposes of clarifying the present invention, different embodiments thereof regarding to cooling/freezing will be described.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since vari
REFERENCES:
patent: 2664274 (1953-12-01), Worn et al.
patent: 4334366 (1982-06-01), Lockwood
patent: 4359962 (1982-11-01), Olsson et al.
patent: 4624220 (1986-11-01), Olsson
patent: 4650413 (1987-03-01), Olsson et al.
"Heat Exchange of a Cylinder with Low-Frequency Oscillations" by V. B. Repin, 1982, pp. 651-655.
Andersson Alvar
Lundsten Lars
Maxe Ann
Sandstrom Roland
Strandberg Tore
Davis Jr. Albert W.
Frigoscandia Food Process Systems AB
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