Enhanced tubular heat exchanger

Abstract

The present invention is an enhanced tubular heat exchanger for a furnace <INS-S DATE="20010109" ID="INS-S-00001">with the heat tubes of the heat exchanger having two straight sections connected by a bend<INS-E ID="INS-S-00001">. The tubes of the heat exchanger include an enhanced portion which has a smaller cross-sectional area than the flue portion, in the form of an elliptically shaped tube. The enhanced portion further includes turbulators to promote the heat exchange from the heated flue gases. Circulation of air around the exterior of the tubes is also facilitated because the enhanced portion is disposed at a small angle relative to the flue portion. A plurality of tubes are disposed within the heat exchanger so that the circulation air first flows over the enhanced portions then over and around the generally cylindrical portions. This lowers the initial pressure drop in the circulation air flow and thereby facilitates the circulation of and heat transfer to the air being heated.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to heat exchangers for furnaces. More specifically, the field of the invention is that of heat exchanger tubes which provide passageways for heated flue gases within furnace heat exchangers.2. Prior ArtTubular conduits are used in heat exchangers to provide an interior conduit for flue gases and exterior heat transfer surface for circulating air. The interior conduits may be formed from metallic clam-shell plates wherein two clam-shell plate surfaces are connected together to form the conduits, or the tubular conduits may comprise metal tubes. Within furnaces, such tubular conduits provide a passageway for flue gases, the heated products of combustion, which flow through the heat exchanger. The flue gas flow transfers heat to the material defining the passageway which then transfers the heat to air circulating over and around the heat exchanger.The heat exchanger contains the flue gas flow. An inducer ...

AI Technical Summary

Benefits of technology

The present invention is a heat exchanger tube which includes an enhanced portion which is narrowed to have a smaller cross-sectional area than the cylindrical flue portion of the tube. The enhanced portion promotes heat transfer by accelerating and disrupting the flow of the flue gases. Also, the heat transfer properties of the present invention are improved by increasing the amount of internal heat transfer surface in comparison to total volume in the enhanced portion.

Also an object of the present invention is to provide a heat exchanger conduit for a furnace which reduces the pressure drop across the heat exchanger conduits.

Problems solved by technology

Also, the conduits generally include two or more elongated sections connected by bend sections so that the interior flow of heated flue gas is disrupted and impacts interior surfaces of the tubes to promote further heat exchange.

However, a problem with prior art heat exchanger conduits involves the inefficiency in the amount of heat transferred from the heated flue gases to the circulating air.

A problem with this configuration is that although disruption is caused within the flow along the inner surfaces of the wall, the flow in the center may only be minimally effected.

A problem with this configuration is the expense involved in manufacturing tubes which vary in cross-sectional shape over their length.

The problem with the clam-shell configuration is that the flow produced by the circulator fan is only minimally disrupted in the spaces between the plates.

A problem with the tubular configuration is that the first row of cylindrical elongated portions causes a high pressure drop in the circulation flow resulting in the circulation flow only minimally wrapping around the other row or rows of elongated portions so that hot spots develop on the downstream elongated portions.

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