US 5,347,103 AGranted

Convection furnace using shimmed gas amplifier

AssigneeBTU International, Inc.

InventorPierre J. LeMieux

Life of this patent

Estimating the term…

Loading patent…

Abstract

A convection furnace using a shimmed gas amplifier to provide a flow of gas over a heating element is disclosed. The heating element is mounted in a substantially leak proof, pressurizable heating chamber. A gas amplifier in an upper plate of the chamber draws gas from a surrounding plenum into the heating chamber at a high flow rate. The pressure in the chamber increases from the input of pressurized gas and the heating of gas flowing over the heating element. The gas amplifier is provided with a toothed spacing shim which creates a stronger flow into the chamber. The stronger flow is capable of resisting the back pressure on the flow from the high pressure in the chamber. The heated gas passes through a plurality of orifices in a lower plate of the chamber to impinge on product traveling below the heating chamber on a conveyor and is recirculated via the plenum to the gas amplifier. The heat transfer rate in the chamber may be controlled by controlling the input flow rate to the gas amplifier.

Claims24

Dependent claims

A convection furnace comprising:

a thermally insulated housing;
a sealed, pressurizable heating box mounted inside said housing defining a heating chamber;
a heating element mounted inside said box;
a gas plenum inside said housing above said heating box;
and
a gas amplifier mounted in an upper section of said box to draw gas from said plenum into said box for circulation over said heating element, said gas amplifier comprising:
a nozzle having an entrance from said plenum, said entrance being formed with a Coanda profile, and an exit to said heating chamber,
opposed interior surfaces configured to define an annular gap surrounding said entrance of said nozzle, one of said opposed surfaces being contiguous with said Coanda profile of said nozzle,
a gas input inlet for connection to a source of pressurized gas, said inlet being in fluid communication with said annular gap to introduce a pressurized input gas from the source of pressurized gas to said annular gap for flow over said Coanda profile of said nozzle and into said heating chamber, whereby gas in said plenum becomes entrained in said flow of input gas, and
a shim disposed between said opposed surfaces to define the width of said annular gap, said shim having a plurality of radially inwardly extending teeth thereon configured to protrude into a flow passage of said nozzle, whereby said flow of input gas and entrained gas becomes capable of withstanding pressure in said heating chamber.

7 more elements

Dependencies are inferred from the claim text.