Heat exchange manifold

Details Heat exchange manifold Heat exchange manifold

1997-04-07

2001-01-23

Chambers, A. Michael (Department: 3753)

Heat exchange

Movable heating or cooling surface

Rotary drum

C165S085000, C165SDIG001

Reexamination Certificate

active

06176300

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to indirect heat transfer to and from the solid phase. Specifically, it relates to rotating-drum-type drying machines and flaking machines for use in the chemical processing industry.
Drying machines frequently generate their granular solid products by having a solution (or slurry) applied to a heated metal roller. The slurry features a volatile solvent which quickly evaporates, so that, in effect, the solute remaining is dried. These rotating-drum-type drying machines are commonly referred to as drum dryers. One common way of heating the drum dryer is to employ a hollow roller and to inject gaseous steam into the hollow interior of the roller, withdrawing the condensate with a siphon line.
Many flaking machines, or flakers, also operate by applying a feed material to a rotating drum. However, in the case of a flaker, the feed material is typically a relatively hot molten wax-like feed and the rotating drum is a cooled (rather than heated) metal roller. When this hot molten feed material is applied to the cooled metal roller, solidification occurs, and the product may then be collected.
These drum dryers and drum flakers represent two types of a general class of machines known as heat exchangers. In the case of the drum dryer, the transfer (or exchange) of heat occurs when heat passes from the outer surface of the heated rotating drum to the slurry, resulting in the drying of the solute. In the case of the drum flaker, the transfer of heat occurs when heat passes from the hot molten feed material to the outer surface of the cooled rotating drum.
Thus, this invention relates to an improved heat exchanger, which will prove itself to be particularly useful to those interested in performing flaking operations. However, the heat exchanger will doubtless also be useful in other applications in other industries. Rotating-drum designs are employed in grinding machines and printing machines as well, for example, and the advantages of the design of this invention may find excellent application in those technologies as well.
BACKGROUND OF THE INVENTION
Drum dryers and revolving-roller flakers have been employed in industry for many years. They have been applied to a wide range of chemical products (organic and inorganic), pharmaceutical compounds, waxes, soaps, and food products.
Key to the performance of these machines is the maintenance of a controlled temperature distribution across the outside surface of the roller. The outside surface of the roller is the surface upon which the feed material to be dried or flaked is deposited. A common design objective is for this temperature distribution to be substantially uniform, or constant, from one endwall of the cylindrical roller to the other. Another common objective is that, if the temperature on the outside surface of the roller is to vary, it do so in a gradual fashion and by a relatively small amount.
A common design for drum flakers involves the use of a hollow cylindrical roller. Within the interior of the roller, and along its longitudinal axis, is placed a central pipe. The pipe is perforated with holes. A heat exchange fluid, such as water, is pumped transferred down the perforated central pipe. The fluid exits the central pipe through the numerous holes in a spray which strikes the inside surface of the roller. It is commonly observed that this cools the roller, which has been heated by the application of the heated molten feed material. A transfer of heat results (or the heat “flows”) from the feed material to the roller wall (first to the outside surface then to the interior then to the inside surface) to the heat exchange fluid. The heat exchange fluid (now at an elevated temperature) then accumulates at the bottom of the substantially empty roller and is removed, commonly by means of a siphon line. See, e.g., U.S. Pat. No. 2,445,526; CHEMICAL ENGINEERS' HANDBOOK 11-40 to 11-41 (including FIGS. 11-26(
c
)-(
d
)) (Robert H. Perry & Cecil H. Chilton eds., 5th ed. 1973).
Another general approach has been to substantially fill the roller with heat exchange fluid, but to assure that good heat transfer and good subsequent mixing takes place by means of various baffling arrangements. See, e.g., U.S. Pat. No. 2,068,779; U.S. Pat. No. 3,633,663.
Only a few patents have employed a piping manifold to directly transfer a heat exchange medium directly to the inside surface of a heat exchange roller. U.S. Pat. No. 3,426,839
discloses a drum dryer design, which uses spoke pipes and longitudinal jet pipes to transfer gaseous steam from a central pipe to the roller wall. The longitudinal jet pipes are directly adjacent the inside surface of the roller, so that gaseous steam is distributed to the wall through tiny openings along the length of the jet pipe. The longitudinal jet pipes represented a good distribution mechanism for drum dryers employing gaseous steam.
U.S. Pat. No. 2,603,457 features the use of upwardly-directed jet injectors. This patent emphasizes quick withdrawal of the fluid, so that the hollow interior of the roller is never more than half full.
The present invention surpasses the prior art in that it provides an improved (and economic) temperature distribution across the outside surface of the heat exchange roller. In many cases, the desired temperature distribution is a uniform or only gradually varying one, and this invention is well adapted to generating these types of distributions.
It should be noted that the specification here provided simultaneously discloses both apparati and methods for exchanging heat. While it is anticipated that the present invention will primarily be used to effect flaking, as stated above, the apparati and methods here disclosed are well suited to other applications in other industries. Thus, for example, the invention is frequently referred to as either (a) a flaker or flaking machine, or (b) a heat exchanger. The latter designation is chosen to highlight that the instant invention includes non-flaking heat-exchange applications.
SUMMARY OF THE INVENTION
The heat exchanger of this invention comprises a hollow, cylindrical roller mounted for rotation on its longitudinal axis and a manifold positioned in the hollow interior of said roller. The manifold comprises a central pipe, extending axially along the longitudinal axis of said roller, and a plurality of spoke pipes. These spoke pipes are in communication with both the central pipe and the hollow interior of the roller. In one embodiment, the spoke pipes radiate from, and independently define a plurality of spoke pipe planes perpendicular to, the central pipe.
Heat exchange fluid is sequentially (a) introduced to the central pipe, (b) transferred through the central pipe and then through the spoke pipes, so as to exit the spoke pipes and collide against the inside surface of the roller, thereafter turbulently mixing with the entire mass of heat exchange fluid contained within the substantially full roller, and thereafter (c) withdrawn from the hollow interior of said roller.


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