GB2049145A - A gas heater - Google Patents

Abstract

A gas heater has a number of groups 1, 2 of heat exchange tubes arranged in series. A hot gas passes through the tubes, and the gas to be heated passes around the outsides of the tubes. The gas to be heated passes from one side 6 of the tube group to the other 4, and then through a conduit 8 to the next, series-arranged tube group where it again passes from one side 7 of the group to the other 5. The direction of flow of the gases around the tubes is the same in each group. The gas therefore flows along a Z-shaped path through the heater. <IMAGE>

Description

SPECIFICATION A gas heater The present invention relates to gas heaters, particularly for heating air for steam boilers, furnaces and similar apparatus.

According to the invention, there is provided a tubular air heater for steam boilers and furnaces, comprising: tube bundles, built into gas ducts and connected to each individual pass at opposite ends by distributing and collecting air boxes arranged in series one above the other; bypass air conduits for conveying air into individual passes in one and the same direction in a criss-cross flow with respect to gases, the bypass air conduits being formed in voids between the tube bundles of each individual pass and coupling one with another the collecting and the distributing air boxes.

The bypass air conduits are preferably built in voids between the tube bundles of each individual pass and connect one to another the collecting and the distributing air boxes.

In an alternative embodiment, the tube bundles may be assembled as separate sections having lateral enclosures serving as walls of the bypass air conduits, the inlet and the outlet orifices thereof being brought out into the collecting and the distributing air boxes of the passes arranged in series.

This technical solution additionally reduces the amount of metal necessary to manufacture the air conduits and simplifies the design thereof.

The invention will now be further described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a vertical section through a twopass air heater according to the invention; Figure 2 is a horizontal section on line ll-ll through the first pass of the air heater shown in Fig. 1; Figure 3 is a horizontal section on line Ill-Ill through the second pass of the air heater illustrated in Fig. 1; Figure 4 is a vertical section on line IV-IV through the tube bundles of the air heater shown in Fig. 1.

The air heater comprises a first set 1 and a second set 2 of tube bundles built into gas ducts 3. Heating gas passes along the ducts 3 inside the tubes. In both passes, there are collecting air boxes 4, 5 and distributing air boxes 6, 7. As is readily apparent from Fig. 1, the collecting and the distributing air boxes are arranged in series one above the other.

Bypass air conduits 8 connect to one another the collecting box 4 of the first pass and the distributing air box 7 of the second pass. Fig.

1 also shows in dotted lines the flow of air through the heater along a Z-criss-cross pattern.

Fig. 2 clearly shows in a horizontal section on line ll-ll through the first pass of the air heater illustrated in Fig. 1 a distributing air box 6 and a collecting air box 4 on opposite sides of the tube bundles. Air passing from box 6 to box 4 passes through the tube bundles 1. The bundles 1 can be assembled as separate sections 11. Bypass air conduits 8 are built into gaps between the tube sections 11. Inlet orifices 1 3 of the air conduits 8 are open into the collecting air box 4. Lateral enclosures 14 of the sections 11 between which the bypass air conduits are formed serve as walls thereof. This arrangement of the tube bundles with the air boxes and the bypass air conduits is very compact and ensures a small resistance to air flow thereof.

The use of the enclosures of the sections 11 for building the air conduits 8 reduces the consumption of metal for the manufacture thereof.

On Fig. 2 is also shown the flow of air from the distributing air box 6 into the tube bundle 1, and therefrom, into the collecting air box 4, wherefrom air passes into the second pass through the bypass air conduits 8.

The horizontal section on line Ill-Ill through the second pass of the air heater of Fig. 1, illustrated on Fig. 3, is similar to the section through the first pass. Here outlet orifices 1 6 of bypass air conduits 8 open into a distributing air box 7 coupled with sections 1 8 of the tube bundles 2. Air flows from the air box 7 through the tube bundles 2 to a collecting air box 5.

Arrows on Fig. 3 also illustrate the flow of air from the bypass air conduits 8 into the distributing air box 7, then into the sections 18, wherefrom air is directed into the collecting air box 5.

Fig. 4 shows in vertical section the gas ducts 3 accommodating the tube bundles 1, 2. Bypass air conduits 8 are fully shown here.

The air heater operates in the manner below.

The tube bundles 1 and 2 of both passes are heated by gases passing through the gas ducts 3. Air to be heated is conveyed to the distributing air box 6 of the first pass, wherefrom it passes into the sections 11 of the tube bundles 1. Once heated in the tube bundles 1, air exits into the collecting air box 4 of the first pass, thence rises into the second pass through the bypass air conduits 8 whose inlet orifices 1 3 open into the collecting air box 4.

Air flows into the distributing air box 7 of the second pass through the outlet orifices 1 6 of the bypass air conduits, and as it passes through the tube bundles 2 of the second pass it is finally heated to the required temperature. It should be noted that air enters the tube bundles of the second pass from the same end as the tube bundles of the first pass so that the air moves in the same direction in the tube bundles of both passes, this ensuring a high effect from the Z-criss-cross flow.

Air exits from the tube bundles 2 of the second pass into the collecting air box 5 and is exhausted from the air heater into a boiler firebox, a furnace or similar units.

When an air heater is built, for example, of three passes, its design and mode of operation are no different from those of the air heater described above, the third pass repeating the preceding pass.

The heater described has a maximum heating surface and a small resistance to air flow to be obtained against minimum weight and size of the air boxes.

Claims (3)

1. A gas heater comprising a plurality of heat-exchange tubes arranged in groups, means for passing hot gases through the tubes, a distributing gas box on one side of each group of tubes and a collecting gas box on the other side so that gas to be heated passes from the distributing box around the tubes to the collecting box, and a bypass gas conduit for conducting gas from the collecting box of one tube group to the distributing box of another group in such a way that the gas to be heated passes through each group in the same direction.

2. A heater as claimed in claim 1, wherein the tube groups have lateral walls which form boundaries for the bypass gas conduits, the inlet of each conduit communicating with the collecting box of one tube group and the outlet communicating with the distributing box of an adjacent, series-arranged group.

3. A gas heater substantially as hereinbefore described with reference to, and as shown in the accompanying drawing.