GB2203824A

GB2203824A - Rotary thermal regenerators

Info

Publication number: GB2203824A
Application number: GB08708565A
Authority: GB
Inventors: Waldemar Hryniszak
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-04-07
Filing date: 1987-04-07
Publication date: 1988-10-26
Also published as: GB8708565D0

Abstract

An exhaust gas extractor fan 1 and a rotary regenerative airpreheater are combined in one unit to extract heat from hot waste gases, for example of a heating appliance, and transfer it to fresh air before being used, partly or completely for instance for combustion purposes. Therefore the amount of fuel consumed by such an appliance can be reduced, having, apart from reducing fuel costs, the additional benefit of reducing air pollution. The regenerative airpreheater disc is preferably made from a ceramic material. The disc can be driven via a reduction gear by the motor of the extractor fan, or a separate motor, its speed being geared down to that of the disc. <IMAGE>

Description

THE THERMODYNAMIC AUGMENTOR.

The need to reduce energy consumption is increasingly appreciated when it comes to central or individual heating of the rooms of a building. After all, in highly industrialised countries one third of the energy consumed is for industrial and domestic heating.

There are two trends for reducing energy which can be distinguished: (a) Reduction of the heat wasted in the exhaust by recovering and recirculating it, (b) recovery of the latent heat contained in the water vapour of the combustion products, for example of natural gas.

Both methods of reducing gas consumption can be realised if the heat contained in the initially hotter.exhaust gases are transferred through a heat exchanger to the new charge of initially colder air, thus preheating it.

As tulle ambient temperatures are usually well below the condensing temperature of the water vapour contained in the exhaust gases it will condense within the matrix i.e. heat transferring palt of the heat exchanger if there is sufficient time, and the latent heat will be added to the waste heat recovered as mentioned above, Provided that the matrix is made from a ceramic material there will be no attack by the condensing products.

Natural circulation in the case of a warm water generator has already been replaced by forced circulation due to the introduction of a water circulating pump.

Increasingly the advantages are realised if instead of natural circulation, forced circulation is also introduced on the gas side. Smaller heat exchanging surfaces, i.e. greater compactness together with improved controllability of the amount of warm water to be generated can be mentioned in this context. But in other appliances too, for example radiant heaters, such forced circulation has similar advantages. To realise it however pressurising or extracting by a blower or fan has to be employed.

The function of such forced circulation combined with waste heat recovery are fulfilled by the proposed thermodynamic augmentor. Forming a self contained unit it can roughly be compared with the turbosupercharger of internal combustion engines.

There are several ways f realising such an augmentor as briefly described in the following.

-FIGS. 1A and 1B.

The impeller with backward curved blades (1) is fixed in the conventional way to the outside rotor of the electric motor (2). The casing (3) is linked with the -sta=tionry part (4) of this motor. The outlet of the exhaust gas i8 provided-at -(5).

In addition to this blower assembly there is the disc assembly (6) consisting of the casing part (6a) between the blower inlet and disc outlet. The disc casing (6b) containing the rotary disc (7) and the outlet casing'(6c). The inlet of the exhaust gas is at (8), the outlet of the warm fresh air at (9)ç.

The air before being heated enters the casing part (6a) at (10).

The fixed axle (11) provided for the rotation of the disc is supported in casing part (6a) by support (12) which is linked to the dividing plate (13) in casing (6a) separating the exhaust gas flow entering the blower from the fresh air flow. The separator (14) thus divides the disc in two halves.

In casing part (6c) there is also a support (15) for the axle. The hub (16) of the disc contains preferably at its low temperature end the rotating part of the bearing (17).

The drive of the disc is by friction, a conical pinion (18) is directly driven by a small electric motor (19). The support (20) of the motor/pinion assembly has a spring (21) which presses I.tc pinion against the rough surface of the rim of the disc in approximately its low temperature face.

FIGS. 1A and 1B (contd.) As an alternative, instead of a friction drive a positive engagement drive is possible as shown in Fig. lib where an L shaped ring (22) with a simple gear (23) on its radial leg, this gear meshing with pinion (18) fixed to the shaft of the electric motor (19j with a support (20).

FIG. 2.

The impeller with backward curved blades (1) is fixed in the conventional way to the outside rotor (2) of the electric motor (3). The casing (4) is linked with the stationary part (5) of this motor. An opening (6) is provided for the egress of the exhaust gas.

In addition to this blower assembly there is a disc assembly (7) incorporating the disc (8) in the casing (9). A plate (10) guides the exhaust gas from the upper half of the disc into the blower and separates it from the fresh air. The opening (11) is provided for the ingress of the fresh air due to the suction of the blower into the lower half of the disc. Linked with the separating plate (10) is a central bearing (12) for the support of the driving shaft (13) of the disc. The shaft (14) of the motor is hollow and linked in the stationary side of the blower with a pinion (15). Four gear trains consisting of similar large and small wheels reduce the speed of the motor to that of the disc, its shaft (13) being linked to the large wheel (16) of the last gear train.

This wheel is also linked with a slipping clutch (17) in such a manner that if the power required by the disc xr.eeds a certain value, the shaft of the disc is automatically disconnected from that of the motor.

FIG. 3.

The impeller (1) of the blower is driven in the usual way by an electric motor (2).

In this case a standard arrangement of motor and impeller has been used whereby the outer rotor is linked with the impeller.

It is of course possible to buy the impeller, which has preferably backward curved blades from an established maker and drive it by any suitable electric motor say with an inner rotor.

At a certain distance which is mainly governed by aerodynamic considerations as affecting flow losses due to deflection, acceleration or deceleration, the disc (3) is arranged preferably on the same axis as the blower. This disc is subdivided in two halves by separators (adjacent to each of the two faces) (4).

On the upper half (4a) of the disc the exhaust gas entering at (5) passes through the porous matrix, i.e. heat exchanging part of the disc, and is then drawn into the blower. Thus from a half circular shape, the flow channel changes into a circular in accordance with the inlet of the impeller. The exhaust gas after leaving (4a) and travelling through the blades of the impeller (1) is led to the atmosphere at (8).

As far as the other half (4h! is concerned, fresh air is drawn in from an annular inlet () by the blower, i heated in the matrix because of heat exchange between the two media and then leaves at (7) the casing of the disc.

The casing (9) of the blower is linked with that (10) of the disc. So there are essentially, from an assembly point of view two parts, the blower (9) which is a standard item and the casing (10) with the disc and its drive.

FIG. 3. (contd.) One simple'way of driving the disc is by using a unit (15) consisting of a standard small electric motor (11) linked with a speed reduction gear (12). Motors of different performance and gears of different ratios are well tried stock items.

The'speed of the electric motor will be at 50Hz between 250 and 500. The low speed of the disc may be anything between 10 and 25 rpm so that the gear ratio required is 10 and 50.

The shaft from the gear is linked with the hub (13) of the disc. In view of its very low weight an overhung arrangement can be accepted.

One disadvantage of this simple and straightforward way of driving the disc is that the gear has to be arranged near the hot face of the disc and attached to the casing adjacent to this face which leads the hot exhaust gases to the disc and the hot air from the disc. However, it is possible to distance (14) the gear from the hot walls of the casing and it is also possible to ventilate the space (15) in which the gear is operating by having a pipe (16) between this space and the suction side of the blower together with inlet apertures (17) for the cooling air. It is also possible to draw the cooling air from this aperture directly into the inlet of the exhaust gas via an aperture (18).

In the design described, the disc is supported in its centre requiring either a central shaft or axle with bearings either outside the disc and in the stream of the heat exchanging gases in the case of the former design, and bearings within the disc in the case of the latter.

It is however possible to arrange both the support and drive of the disc at its outer periphery.

With the high temperatures which may be encountered as far as the two heat exchanging gases are concerned, it is advisable to protect the rim area of the disc from overheating and therefore jeopardising the proper functioning of support and drive. This can be achieved as illustrated in Fig.4.

The impeller (1) of the extractor fan is attached to the outside rotor of an motor (2) in the conventional way. Its stationary part is fixed to the casing (3) of the impeller and the motor. An outlet (4) is provided for the exit of the exhaust gases. This extractor fan is one sub assembly of the thermodynamic augmentor.

The second sub assembly consists of a rotary regenerative heat exchanger incorporating a disc (5). The rim made from a material such as nylon, having a good dry friction capability consists of a gear ring (6) with a bearing extension (7).

This rim is attached to the low temperature part of the disc. A mild steel ring (8) forms the stationary part of both the journal and the thrust bearing.

Furthermore a spring type thin walled seal (9) presses gently the disc with its rim against this supporting seal ring.

So as to keep the disc near its rim and support cool1 a space (10) is provided through which ambient air is drawn into the fresh air side (11) as well as the exhaust gas side (12). These two sides of the disc are formed by separators (13) and (14). Thus a lay-r of cold air protects the rim and the support of the disc from overheating.

A pinion (15) meshes with the gear ring (6) and is directly driven by an electric motor (16) supported in p.t-t. (i 1) wtlictl is fixed to title the support (8) of the disc.

An inlet header (18) and an outlet header (19) similar in shape are provided for the inflow of the exhaust gas and the outflow of the fresh air. A plate (20) linked with the separator (13) guides the exhaust gas from the half circular heat exchanger outlet to the circular impeller inlet of the blower.

Further outer cooling of the gear ring and its support including the bearings can be provided in a similar way as in the case of the inner cooling if so required.

The directions of flow of the initially hot exhaust gas and the initially cold fresh air both travelling through the permeable matrix of the disc in counter-flow have been shown in the drawing. It is worthwhile noting that the fresh air before entering, cools the motor (16) driving the disc.

The peripheral annular flow of the fresh air for cooling the rim and its support have also been indicated.

Claims

CLAIMS:

1. Thermodynamic augmentor characterised by an extractor fan and a disc type regenerative airpreheater combined in one unit, its function being to extract hot exhaust gases from a heating appliance thus providing on its gas side forced circulation and in addition transfer of some of the heat contained in the exhaust gas to the fresh air thus preheating it.

2. Thermodynamic augmentor in accordance with Claim 1 where the disc of the airpreheater is driven via a speed reduction gear by the electric motor of the extractor fan.

3. Thermodynamic augmentor in accordance with Claims 1 - 2 where the fan, the gear and the disc are co-axial.

4. Thermodynamic allgmentor in accordance with Claims 1 - 3 where the disc of the @@@@@@@@@@@ is driven separately by an electric motor.

5. Thermodynamic augmentor in accordance with Claims 1 - 4 where the speed reduction g('lt consists of the large wheel being integrated with the rim of the disc and the small wheel being directly driven by the electric motor.

6. Thermodynamic augmentor in accordance with Claims 1 - 5 where contact between the large and the small wheel is by friction.

CLAIMS: (continued)

7. Thermodynamic augmentor in accordance with claims 1 - 6 where the friction gear driving the disc is chosen in such a way that when the torque required by it exceeds the capability of the electric motor, slipping occurs.

8. Thermodynamic augmentor in accordance with Claims 1 - 7 characterised by a cylindrically shaped augmentor whereby the components required for the control of the speed of the extractor fan and that of the disc are mounted on the rear of the augmentor fan within the envelope of the cylinder.

9. Thermodynamic augmentor in accordance with Claims 1 - 8 where the matrix of the disc is employed as part of a burner providing hot combustion products to be used in the appliance linked with the augmentor.

10. Termodynamic augmentor where the disc is driven and supported on its ut.t-t' persiph*^ry incorporating a rim with a gear ring preferably integral with this rim, the rim being attached to the outer surface of the disc, tit is rim with its gear being near the low temperature face of the disc..

11. Thermodynamic augmentor in accordance with Claims 9 and 10 where the rim with its gear is made from a dry lubricating material such as PTFE and the stationary portion for the bearings is in the form of a ring as well as a header for the hot exhaust gas and the warm CLAIMS (continued): 11. (contd).

fresh air, leaving a gap between this stationary ring and the outer periphery of the disc, so that the cooling air, attracted by the suction of the extractor forms a cold layer between the warm heat exchanging media and the rim parts of the disc.

12. Thermodynamic augmentor in accordance with Claims 10 - 11 where channels are formed both in the rotating and the stationary part of the disc support and drive in such a way that due to the suction of the extractor fan cold ambient air can flow through the said parts of the rim in such a way that they are additionally cooled.