WO1992008943A1

WO1992008943A1 - Improved heat exchange equipment

Info

Publication number: WO1992008943A1
Application number: PCT/GB1991/001959
Authority: WO
Inventors: John David Gillan; Stephen John Hall
Original assignee: Suter Environmental Limited; H. & M. Disinfection Systems Limited
Priority date: 1990-11-08
Filing date: 1991-11-07
Publication date: 1992-05-29
Also published as: EP0555322A1; GB2249827A; AU8869991A; GB9024315D0; GB2249827B

Abstract

The exterior surfaces of an air-treating heat exchanger (13) are washed in situ in a treatment (e.g. food processing) space (10) by enclosing the heat exchanger and fans in a casing (15) and spraying the exterior surfaces with washing liquid issuing from nozzles (21) while collecting the washing liquid dripping from the heat exchanger in a tray (18), the fans being inoperative throughout each spray time.

Description

IMPROVED HEAT EXCHANGE EQUIPMENT

Technical Field

This invention relates to a method of periodically washing the exterior surfaces of an air-treating heat exchanger and to heat-exchange equipment for employment in the method.

The invention has particular utility to bacteria level control in air coolers used in food processing spaces but is expected to find uses in other applications.

Summary of the Invention

In its method aspect, the invention comprises enclosing the heat exchanger and air-moving fans in a casing including means to collect liquid dripping from the heat exchanger, and is characterised by spraying the exterior surfaces of the heat exchanger and fans with the required washing liquid delivered under supra-atmospheric pressure and timing the supply of washing liquid both as to duration of spray time and periods between spray times, the air-moving fans being inoperative throughout each spray time.

Suitably the washing liquid is supplied with compressed gas via a series of nozzles angled to spray, in concert, all exterior surfaces of the heat exchanger and fans.

Where the washing is to disinfect, a concentrated source of fluent (e.g. liquid, cream or soluble powder) disinfectant can be provided which is dispensed under the control of mechanical and electrical control means into a diluting water supply. The mechanical control means can include a pump to automatically dilute the concentrated disinfectant into the water supply, a source of compressed air or a valve for an external supply of compressed air, pressure regulators for the disinfectant solution and compressed air to give a desired spray droplet size within the casing. Non-return valves- and filters to prevent blockages or backpressure are preferably also included in the mechanical control means. The electrical control means can secure electronic control of solenoid valves provided as part of the mechanical control means to make the system fully automatic and accurate. Visual indication by means of illuminated lights can be provided to show the washing system is in operation.

Where the washing is also required to achieve some defrosting of the heat exchanger, the washing liquid can be heated prior to spraying.

In its apparatus aspect, air-treating heat-exchange equipment comprising a heat exchange coil having extended air contact surfaces, at least one fan for moving air over the air contact surfaces, and a casing containing the coil and at least one fan and providing an air inlet to the contact surfaces and an air outlet from the casing, is characterised by a pipe system within the casing which includes a plurality of spray nozzles and terminates in a washing liquid inlet to the casing, means to supply disinfecting liquid to the washing liquid inlet and drain means for collecting washing liquid running off said at least one fan and extended air contact surfaces.

Desirably the means to supply washing liquid also supplies pressurised air so that it is an aerosol of washing

(e.g. disinfecting) liquid which is sprayed into the casing.

Preferably at least one electrical motor for the at least one fan is also housed within the casing, the or each motor being proofed against liquid ingress. Suitably the drain means includes a drip tray for collecting the liquid sprayed into the casing and at least one drain pipe from the tray for ducting condensate and used washing liquid from the casing to waste. Brief Description of the Drawings

One embodiment of apparatus in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which

Figure 1 is a schematic view of a cased air-cooler mounted in a treatment room, and

Figure 2 is an enlarged view of part of the air-cooler with an upper closure plate of the casing removed.

Description of Preferred Embodiment

A treatment room 10 is shown in Figure 1 with a treatment surface 11 on which food processing is taking place. To keep the air in the room at a required tempera¬ ture acceptable to the processing being carried out therein, an air cooler 12 is provided having a heat exchange coil 13 (not shown in Figure 1) and one or more electrically powered fans (also not shown) contained in a casing 15 located in an upper part of the room 10. Air 14 is drawn into the rear of the casing 15 by the fan(s) through the air cooler 12 and cooled air 17 is discharged from the front of the casing 15 through grilles 16. The casing 15 is provided with a drip tray 18 connected to a waste pipe 19 and a pipe system 22 (see Figure 2) within the casing which leads to a series of spray nozzles 21.

The pipe system 22 is connected to a liquid supply pipe 20 leading to a control panel 23 (as shown - located in the room 10). A supply 24 of clean water, a supply 25 of compressed air and a supply 26 of concentrated liquid disinfectant are also provided to the panel 23. The supply 26 leads from a reservoir 27 of concentrated fluent disinfectant.

At pre-determined intervals during a working day, the panel 23 becomes effective to turn ^"off the power to the fan(s) and the supply of refrigerant to the heat exchange coil 13 and to supply compressed air, and diluted disinfectant to the pipe 20 where it feeds the system 22 and is sprayed over the exposed surfaces of the fan blades and extended heat exchange surfaces of the coil 13 within the casing 15, to thoroughly wash these components as well as the inside surfaces of the casing. The nozzles 21 are provided in sufficient number and each is adjusted as to the semi-cone of spray droplet pattern produced and angle of spraying, to achieve proper coverage of all surfaces within the casing likely to become contaminated with bacteria, but without spraying any significant volume of liquid into the room 10. The sprayed liquid drips down into the tray 18 and discharges to waste via the pipe 19. When the spraying cycle is completed, the panel 23 is effective to cut off the supplies 24, 25 and 26 and thereafter to re-energise the fan motor(s) and restore circulation of refrigerant to the coil 13, so that the air flows 14 and 17 can resume until the next timed disinfecting cycle is scheduled to commence when the sequence described above is repeated.

In practice, a plurality of coolers 12 would be provided in the room 10 so that as the coolers are washed one-by-one, the other cooler(s) take(s) over the air cooling duty in the room. The control panel 23 can be responsible for the sequencing of the washing cycles for the various coolers. If only one air cooler 12 is present, its rating and down-time during washing must be selected so that no excessive rise in temperature in the room 10 occurs during each washing cycle.

A preferred form of control panel 23 comprises

(1) A mechanical panel containing a pump to automatically dilute disinfectant from the reservoir 27 into the water supply 24, pressure regulators for the disinfectant solu¬ tion, compressed air regulators to give the correct droplet size at the nozzles 21 and the necessary solenoid control valves, non-return valves and filters to prevent backpres- sure and blockages.

(2) An electronic panel containing an electronic system to control the solenoid valves in the mechanical panel to make the system fully automatic and accurate in operation. Operation of the system is suitably indicated visually by means of illuminated lights on this panel.

There is no limitation on the size or type of air cooler to which a system according to the invention may be applied providing that adequate space is available for the installation of the nozzles 21 and sprays and that the air cooler is not specified to operate continuously at sub-zero temperatures .

The method of the invention can be applied to air- treating equipment in a variety of different locations which could be mobile as well as static.

Thus, for example, the air-conditioning equipment in a food distribution vehicle can be periodically disinfected by the method of the invention as could air-conditioning equipment in a hospital, factory or public building.

For chill room applications where light frosting of the heat exchange surface may occur, the spray system may also be used as a method of frost removal. The sprayed liquid can be heated to facilitate frost removal.

It is also possible to provide additional pipes and nozzles to ensure a spray of disinfecting fluid and air over the external surfaces of the cooler casing to wash these if so desired.

The duration of spraying will typically be determined by two factors:

Firstly the contact time required by the chemical disinfectant solution to be effective. A typical minimum time for this would be fifteen minutes and on this basis all spray times would be at least fifteen minutes in duration.

The second factor would determine the upper level of spray time. This might be attributed to the level of particulate soiling build up in the air cooler. If the cooler was situated in an area where particulate dirt was very extensive then the spray time may be very long or cycles of disinfecting may be more frequent.

20 nozzles spraying for 15 minutes per day might use 48 litres of disinfectant solution at 3 bar pressure per day.

At 1% concentration of disinfectant this would relate to a usage of some 175 litres of concentrated disinfectant per annum.

Claims

1. A method of periodically washing the exterior surfaces of an air-treating heat exchanger which comprises enclosing the heat exchanger and air-moving fans in a casing including means to collect liquid dripping from the heat exchanger, characterised by spraying the exterior surfaces of the heat exchanger and fans with the required washing liquid delivered under supra-atmospheric pressure and timing the supply of washing liquid both as to duration of spray time and periods between spray times, the air-moving fans being inoperative throughout each spray time.

2. A method as claimed in claim 1, characterised in that the washing liquid is supplied with compressed gas via a series of nozzles angled to spray, in concert, all exterior surfaces of the heat exchanger and fans.

3. A method as claimed in claim 1, characterised in that a concentrated source of fluent disinfectant is dispensed under the control of mechanical and electrical control means into a diluting water supply.

4. A method as claimed in claim 3, characterised in that the mechanical control means includes a pump to automatically dilute the concentrated disinfectant into the water supply, a source of compressed air and pressure regulators for the disinfectant solution and compressed air to give a desired spray droplet size within the casing.

5. A method as claimed in claim 3 or claim 4, characterised in that the electrical control means secures electronic control of solenoid valves provided as part of the mechanical control means to make the system fully automatic and accurate.

6. A method as claimed in claim 1, characterised in that the washing liquid is heated prior to spraying to achieve some defrosting of the heat exchanger during washing .

7. Air-treating heat-exchange equipment comprising a heat exchange coil having extended air contact surfaces, at least one fan for moving air over the air contact surfaces, a casing containing the coil and at least one ^■ fan and providing an air inlet to the contact surfaces and an air outlet from the casing, characterised by a pipe system within the casing which includes a plurality of spray nozzles and terminates in a washing liquid inlet to the casing, means to supply disinfecting liquid to the washing liquid inlet and drain means for collecting washing liquid running off said at least one fan and extended air contact surfaces.

8. Equipment as claimed in claim 7, characterised in that the means to supply washing liquid also supplies pressurised air so that it is an aerosol of washing liquid which is sprayed into the casing.

9. Equipment as claimed in claim 8 or claim 9, characterised in that at least one electrical motor for the at least one fan is also housed within the casing, the or each motor being proofed against liquid ingress.

10. Equipment as claimed in claim 8, characterised in that the drain means includes a drip tray for collecting liquid sprayed into the casing and at least one drain pipe from the tray for ducting condensate and used washing liquid from the casing to waste.