Heat exchange – Radiator core type – Side-by-side tubes traversing fin means
Patent
1981-09-21
1984-01-31
Cline, William R.
Heat exchange
Radiator core type
Side-by-side tubes traversing fin means
165109R, F28D 100
Patent
active
044284195
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to the art of heat engineering and has particular reference to tube-and-fin heat exchangers.
The proposed apparatus may be used in a wide variety of applications as liquid-to-air or air-to-air heat exchangers and may also be employed in air-cooled condensers and evaporators intended for handling various liquids. Said apparatus can operate on dust-free air as well as on dusty air.
The apparatus of the invention may be used with particular advantage as water-to-air radiators and air-cooled oil coolers in the cooling system of transport and stationary power installations.
BACKGROUND ART
Known in the art is a tube-and-fin heat exchanger employed as a water-to-air radiator on motor vehicles, tractors and diesel locomotives. This apparatus comprises flat or round tubes intended for the passage of the coolant flow and installed in appropriate broached holes provided in flat plates serving as cooling fins. The coolant tubes may be disposed in parallel or staggered rows. With this construction, plain rectangular ducts are formed between the tubes, said ducts having no turbulence producing means required for intensifying the heat exchange process in the intertubular space.
Said means for intensifying the heat exchange process have to be provided because the water-to-air radiators of various power installations operate under conditions where the radiator heat transfer coefficient K is approximately equal to the air heat transfer coefficient .alpha..sub.1, i.e., K.apprxeq..alpha..sub.1. Therefore, decreasing the volume and mass of a water-to-air radiator necessitates increasing K which is uniquely determined by the value of .alpha..sub.1. As is known, plain ducts give the least values of .alpha..sub.1. Therefore, the known tube-and-fin heat exchanger has a substantial size and mass.
To decrease the size and mass of the water radiators of the known type, the air heat transfer coefficient .alpha..sub.1 has to be increased, which can be accomplished only by setting up turbulence in the air flow through the radiator passages by the agency of various turbulence producing means.
Also known in the art is a tube-and-fin heat exchanger comprising flat tubes intended for the passage of the water being cooled and installed in parallel or staggered rows in a stack of fins. In order to intensify the process of convective heat transfer in the intertubular space, the fins are profiled in the direction of the cooling air flow as a continuous symmetrical wavy line, whilst adjacent fins are installed in the tube bank so that the projections and depressions of said fins are disposed equidistantly with respect to each other. Consequently, between adjacent fins cooling air ducts are formed which have a wavy profile in the direction of the air flow.
The analysis of the results of tests of the water-to-air radiators of the type under consideration shows that such radiators give little thermohydraulic effectiveness inasmuch as the increase of the air heat transfer coefficient .alpha..sub.1 in the aforementioned ducts substantially lags behind the increase in the energy expended in intensifying heat transfer therein, as compared with similar plain ducts. This is attributed to the fact that when air flows in such ducts a vortex system is set up after each turn and therebefore, said system being equal in scale to or commensurable with the height of the projection in the wavy duct, whereas the height of the projection in such ducts is equal to or commensurable with the duct hydraulic diameter. As a result, up to 70-80 percent of the supplementary energy supplied to the cooling air in said wavy ducts is expended in setting up turbulence in the flow core where the gradients of the temperature field and the density of the thermal flow are small, which entails little increase in the density of the thermal flow. Since these large-scale vortex systems possess substantial kinetic energy, they, overcoming viscosity and friction forces, gradually become dissipated and enter the air layer at the walls. As a resul
Averkiev Leonid A.
Dubrovsky Evgeny V.
Dunaev Viktor P.
Folts Lev A.
Kuzin Anatoly I.
Cline William R.
McNally John F.
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