US2006200A - Apparatus for heat exchange - Google Patents

Description

June 1935- w. c. HARPSTER APPARATUS FOR HEAT EXCHANGE Filed Jan. 6, 19.32

||||||I l l l Kirk/4 /.M K\\\ Patented June 25, 1935 UNITED STATES PATENT OFFICE APPARATUS FOR HEAT EXCHANGE ration of Delaware Application January 6, 1932, Serial No. 584,983 2 Claims. (01. 122-235) This invention relates to'improvements in the control of transfer of heat through the boundaries or confines of fluid systems. The invention will be fully understood from the following de- 5 scription taken in connection with the accompanying drawing in which latter- Fig. 1 is a side elevational view of a heat exchanger unit containing the improvements.

Fig. 2 is a transverse sectional view taken along the line I[-II of Fig. 1.

Referring to Figs. 1 and 2, heat exchange unit is shown comprising two primary conduits 2| and 22 which are connected by a secondary conduit 23. The secondary conduit 23 constitutes a web which may be perforated at 24' to form channels or passageways for the furnace gases and to permit greater freedom in expansion of the metallic structure. The parallel primary conduits 2I-22 constitute a wall having a heat absorbing face exposed to the interior of the furnace chamber.

The amount of heat imparted to the water or primary fluid within the primary conduits 2 l22 and also the temperature of the metal constituting the wall of the primary conduits is regulated by the use of a secondary fluid medium. The sec ondary fluid medium is passed through secondary or auxiliary conduits 23. The secondary conduits 23 may be secured to the primary conduits 2 I-22 by cementing, welding, direct fabrication or any method of juxtaposition which will afford control of heat transfer and temperature of the primary elements. The secondary conduits may be in any ratio of cross sectional-area with respect to the primary conduit, may be made of any suitable material and may be in any desired number with respect to the primary conduit.

By the construction described the primary conduits while directly exposed to the severe furnace conditions are subjected to a micrometer system of control of tube metal temperatures through the biasing or differential relationship of the two systems. The secondary fluid such as steam which is passed through the secondary conduits can be maintained in a system which is entirely independent of the operation for which the primary fluid is used and is thus variable over a wide range of flow to control the tube metal temperature. of the primary tubes and the rate of heat transfer into the primary fluid. Altematively, the secondary fluid may be a part of the primary circulation by-passed through the secondary tubes at an accelerated rate and passing through external cooling apparatus, not shown, in order to afford a temperature control of the heating surface which is exposed to severe furnace conditions. Any required amount of heat may be swept from the primary conduit elements by the secondary fluid and returned to the system as preheated air, superheated steam or the like. The burning of the primary conduit elements is minimized and the efliciency of the operation is increased by allowing maximum temperatures and minimum excess of air.

The invention is particularly applicable for building heat transfer surfaces of pipe stills for distilling hydrocarbon oil, for cracking coils, for subjecting hydrocarbon oil to cracking conditions of temperature and pressure, and for other oil heating elements. The primary conduit such as 2l-22 is utilized for the main operation of heating the oil as is customary in pipe stills and cracking coils. The secondary conduits such as 23 are for the circulation of another fluid such as steam for superheating, air for combustion or some other medium directly connected with the primary operation. The circulation through the secondary conduits controls radiant heat transfer and allows high heat release in the furnace.

The secondary conduits provide an independent means of controlling tube metal temperatures which is advantageous to prevent burning of the tubes, to control coke formation and to increase the length of runs on cracking coils. As applied to pipe stills for the distillation of hydrocarbon oils, the secondary tubes permit of close regulation over the rate of heat transfer whereby cracking of the less refractory stocks is minimized. When utilized in an oil tube still the control of tube temperatures by the secondary heating elements permits of combustion with a small amount of excess air thus increasing the furnace temperature and raising the thermal efflciency of the operation. If desired, the tubular structure can be used in combining steam generation with oil still operations by passing water through the secondary tubes. The duplex heat transfer surface functions either as a superheating surface or in the direct generation of steam. Also in certain operations it may be desirable to have the secondary fluid hotter than the primary to increase rates of heat transfer in certain portions of total surface.

Various changes may be made within the scope of the appended claims in which it is desired .to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim:

1. Heat exchange apparatus, comprising a plu rality of parallel units assembled to form a wall having a heat absorbing face, each unit including 10 rality ct parallel units assembled to form a wall having a heat absorbing face each unit comprising a primary conduit, and a secondary conduit of relatively small cross sectional area, the adjoining faces of the conduits extending parallel and in direct contact over an extended area transversely with each other, portions of said face of the secondary conduit being recessed to form channels transversely of the conduits.

WALTER C. HARPS'IER.

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