US 5,287,919 AGranted

Heat exchanger

AssigneeGas Research Institute

InventorsPaul E. George, II, John S. Barnhart

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Abstract

A gas-fired apparatus for high-volume commercial cooking comprises double-sided griddles, each having a lower platen with a horizontal top cooking surface and an upper platen with a bottom cooking surface. The upper platen of each griddle is moved into a horizontal position in contact with the food, presses downward on the food until it reaches a predetermined level above the lower platen, and stops there. It is lifted away when the food is cooked. Heated oil (maintained at substantially constant pressure by a weight controlled valve) is circulated through a first heat exchanger, which contacts, and transfers heat to, the lower platen, and through a second heat exchanger, which contacts, and transfers heat to, the upper platen. Each heat exchanger comprises three contiguous flat metal layers. The inner layer has a spiral-like passage for the oil to flow through, to heat an outer layer and maintain a substantially uniform temperature over its outer surface. Shape and dimensions for the passage may be determined in part by a finite element thermal conduction computer program. To minimize stresses in the inner plate and differences in thermal expansion among the layers, the passage may be cut out by a laser.

Claims19

Dependent claims

Apparatus for exchanging heat between a heat conductive surface and an adjacent region or object, comprising

a first cover plate at least an order of magnitude longer and wider than its thickness;
a middle plate substantially similar to the first cover plate, contiguous with, and joined to, the first cover plate over their coextensive surfaces;
a second cover plate substantially similar to and positioned opposite to the first cover plate, contiguous with, and joined to, the middle plate over their approximately rectangular coextensive surfaces;
the second cover plate having high heat conductivity;
the middle plate having a confined path therein for fluid to flow into, through, and out of;
the path for fluid being bounded on a first pair of opposite sides by inner surface portions of the cover plates, and one a second pair of opposite sides substantially perpendicular to the first pair by material in the middle plate;
the path for fluid being substantially longer than the perimeter of the coextensive surfaces of the plates, and comprising predominantly a double spiral substantially symmetrical about the centerline between one pair of parallel opposite sides of the coextensive surfaces of the plates and substantially symmetrical about the centerline between the other pair of parallel opposite sides of the coextensive surfaces of the plates, the midpoint of the double spiral lying on one said centerline;
and
wherein the thickness of the second cover plate is about one-fifth to one-third of the thickness of the center plate, and the apparatus comprises also an additional plate in intimate contact with the outer surface of the second cover plate over the region thereof opposite the region that is joined with the middle plate, the additional plate being thicker than the second cover plate, and the total thickness of the second cover plate plus the additional plate is about one-fourth to three-fourths of the separation distance between adjacent portions of the path for fluid.

6 more elements

Apparatus for exchanging heat between a heat conductive surface and an adjacent region or object, comprising

a first cover plate at least an order of magnitude longer and wider than its thickness;
a middle plate substantially similar to the first cover plate, contiguous with, and joined to, the first cover plate over their coextensive surfaces;
a second cover plate substantially similar to and positioned opposite to the first cover plate, contiguous with, and joined to, the middle plate over their approximately rectangular coextensive surfaces;
the second cover plate having high heat conductivity;
the middle plate having a confined path therein for fluid to flow into, through, and out of;
the path for fluid being bounded on a first pair of opposite sides by inner surface portions of the cover plates, and on a second pair of opposite sides substantially perpendicular to the first pair by material in the middle plate;
the path for fluid being substantially longer than the perimeter of the coextensive surfaces of the plates, and comprising predominantly a double spiral substantially symmetrical about the centerline between one pair of parallel opposite sides of the coextensive surfaces of the plates and substantially symmetrical about the centerline between the other pair of parallel opposite sides of the coextensive surfaces of the plates, the midpoint of the double spiral lying on one said centerline;
the separation distance between adjacent portions of the path for fluid being equal to about one-half to four-thirds of the width of the path;
and the thickness of the second cover plate being about one-third to three-fourths of the separation distance between adjacent portions of the path for fluid;
and
means for conveying fluid through the path at a predetermined velocity and a predetermined temperature, upon entering the path, that provide approximately a selected substantially uniform temperature over the outer surface of the second cover plate adjacent to the path.

8 more elements

Dependencies are inferred from the claim text.