GB2198055A - Air conditioning system - Google Patents

Abstract

A microwave source 4 irradiates water 9 contained in a container 6 located in a microwave cavity 3. The water is heated to produce water vapour under which the action of a microwave stirrer element 5 is driven through a connecting pipe 10 into a conduit 1 through which air 2 flows. A control unit 13 is provided to control the amount of water vapour 11 entering the conduit 1. Automatic level means 14 control supply of water into and out of the container 6. The liquid in container 6 need not be water. <IMAGE>

Description

AIR CONDITIONING SYSTEM This invention relates to a vapour conditioning system, and in particular to an air conditioning system having a humidifier.

In air conditioning systems, it is important to produce air at both a comfortable temperature and comfortable humidity. Particularly in winter when cold intake air is heated, the humidity level of the heated air can drop to an unacceptable level. Consequently, it is preferable to incorporate a humidifier with the air conditioning system so as to insert warmer vapour into the heated, relatively drier air.

A basic humidifier system comprises passing the drier heated or cooled air over a tray of water. The tray of water can be heated by immersed electrodes.

However, the vapour transfer is not particularly efficient and in addition the electrodes collect scale from hard water and the tray generally tends to be a source of bacterial growth and infection and a source of contamination from hardness scale and corrosion products.

An alternative humidifier comprises a pipe along 2 wall of a duct carrying the heated or cooled air, this pipe includes apertures to allow passage of steam from the interior of the pipe into the duct. A steam generator can supply the steam for the pipe. In such systems, it is frequently necessary to incorporate some form of collection means to collect condensed water vapour which condenses prior to entry into the air conditioning distribution system.

One of the problems associated with hitherto known humidifier systems for air conditioning systems is the complexity thereof when an efficient system is required. For example, both the above systems cannot easily regulate the quantity of steam placed into the heated air. Also as mentioned hereinbefore, the more complex systems require some form of collection arrangement to collect condensate. In addition, the hardness of water employed in such systems has a tendency to clog up the electrodes heating the water so that they eventually require replacement. This adherence of scale to the heating electrodes either in the water tray or steam generator reduces the efficiency of heating of the water. Furthermore, such systems require large volumes of water to be maintained for heating to ensure the electrodes are covered.It can therefore be seen that hitherto known humidifiers are not energy efficient and are subject to problems with the heating electrodes therefor which require expensive replacement of parts.

It is an object of the present invention to provide an energy-efficient humidifier for an air conditioning system which enables relatively lower volumes of water to be employed and with lower maintenance requirements.

According to the invention there is provided a conditioning system comprising a conduit carrying a gas, a microwave cavity arranged to irradiate a liquid phase thereof, and means to transfer said vapour phase chemical to the conduit for mixing with said gas.

By employing a microwave cavity to heat the liquid phase of the chemical to produce the vapour phase thereof, it is possible to have remote heating of the chemical. In this way, there is no likelihood of the chemical clogging up the source of heat. It is only necessary to provide some means of holding the liquid phase chemical within the microwave cavity so that only this holding portion would require replacement.

The present invention obviates the necessity to include electrodes for heating of the liquid phase chemical. In this way, it is possible to operate with non-conductive liquids and also the indirect excitation of the liquid phase chemical without high surface temperatures associated with heating electrodes allows low temperature construction materials to be employed thereby avoiding deposition of hardness or suspended solids for the chemical. In addition, any hot spots associated with heating electrodes are avoided so that flammable chemicals can be handled. Finally, the separation of the electrical supply providing the microwave energy from the chemical being irradiated enhances the safety of the system.

The conversion of microwave heating energy into heating of the chemical is considerably more efficient than the heating electrode arrangement of hitherto known humidifiers. Furthermore, since the microwave energy acts preferentially on the chemical in its liquid phase, a lesser amount of the chemical needs to be maintained in the microwave cavity compared with hitherto known arrangements and any condensate is itself subject to heating by the microwaves.

Consequently, a cost-effective, reliable and energy efficient conditioning system can be produced with a quicker response, and more accurate controls with less variation between upper and lower control limits.

It will be apparent that the conditioning system is particularly appropriate for an air conditioning system wherein the chemical irradiated by microwaves is water. However, it will be apparent that the conditioning system of the present invention encompasses heating of volatile chemicals for use in production methods wherein a vapour phase of a liquid chemical is required during a production step.

Preferably, the conditioning system includes means to control the residency of the liquid phase chemical within the microwave cavity. Consequently, a minimal quantity of liquid phase chemical can be heated so as to provide rapid production of the vapour phase. This can be particularly important in industrial production techniques to save production time. Conveniently, the quantity of liquid phase chemical resident in the microwave cavity is adjusted in response to sensor means provided within the conditioning system so that the amount of vapour phase chemical transferred to the conduit can be easily and accurately regulated.

An example of the invention will now be described with reference to the accompanying drawing, which shows an air conditioning system embodying the present invention.

A conduit 1 includes gas 2 flowing in the direction illustrated. A microwave cavity 3 receives microwave energy from a source 4. A known stirrer element 5 is arranged to ensure suitably uniform microwave irradiation within the cavity 3.

The microwave cavity disclosed in this example comprises an open container 6 having an inlet pipe 7 and outlet pipe 8. Water 9 is provided through the inlet pipe 7 up to a predetermined level. On actuation of the microwave source and the stirrer 5, the water in the container 6 is heated to produce water vapour. A pipe 10 connects the cavity 3 to the conduit 1. As a result of the action of the stirrer 5 together with the positive pressure created by the water vapour, water vapour passes up pipe 10 and into the conduit 1 as shown by numeral 11. Actuation of the microwave source 4 can be in response to a sensor 12 which may be suitably located within the air conditioning system or in some other suitable position. A control unit 13 receives an indication from the sensor 12 that actuation of the microwave source is required to produce a required humidity and accordingly actuates that source. This control unit is also arranged to actuate an arrangement of valves 14 whereby water in the container 6 can be topped up to compensate for loss of vapour through the pipe 10. The arrangement 14 also includes a further valve allowing draining of the water 9 through the outlet pipe 8 to a drain 15. It will be apparent that during this operation, the microwave source 4 is disabled. The sensing of the level of water in the container 6 can take any known form, for example the power absorbed from the microwave source 4 could be monitored.

It will be apparent that the described system can be subject to considerable modification. For example, with an air conditioning system, the container 6 comprises preferably plastics material which can itself include a lining for removal when required. Furthermore, as an alternative to the stirrer 5 an extracter fan within the pipe 10 could create a negative pressure therein to suck the vapour out from the cavity 3. It is however particularly convenient to combine the action of the microwave stirrer with creating a positive pressure in the cavity 3. It will also be apparent that the simple construction of the container 6 is the preferred form, however other more intricate arrangements of container could be employed to enhance the surface area available for evaporation of the vapour.

Finally, the conditioning system shown in the figure could be altered to allow production of controllable amounts of vapour of a chemical for use in some production process. For example, the conduit 1 could be carrying a gas requiring the addition of a predetermined amount of a volatile liquid. The volatile liquid can be provided in the container 6 and irradiated by the microwave source 4 to produce the volatile vapour. A meter (not shown) could be incorporated into pipe 10 to detect flow rate and thereby calculate the amount of volatile vapour passed into the conduit 1. This meter can be connected to the control unit 13, which in response to predetermined instructions can dissable the energy source 4 so that a fixed amount of volatile vapour is inserted into the gas contained in the conduit 1. Such an arrangement is particularly convenient since the microwave energy heats the volatile liquid remotely and rapidly with no exposure to the electrical power supplying the microwave source 4. Furthermore, the heating of the volatile liquid by the microwaves is free from hot spots and the temperature of the entire cavity need only attain a temperature below the flash point of the volatile liquid.

Claims (10)

1. A conditioning system comprising a conduit carrying a gas, a microwave cavity arranged to irradiate a liquid phase chemical to produce the vapour phase thereof, and means to transfer said vapour phase chemical to the conduit for mixing the said gas.

2. A system as claimed in claim 1 wherein the microwave cavity comprises an open non metallic container for said chemical, and a microwave source arranged to irradiate the container.

3. A system as claimed in claim 2 wherein the microwave source includes a stirrer element located to enhance uniformity of irradiation of the container and to assist in transfer of the vapour phase chemical to the conduit for mixing with said gas.

4. A system as claimed in claim 3 wherein said container and stirrer element are located within an air pipe enclosure and said means to transfer connects said enclosure to the conduit.

5. A system as claimed in any preceding claim wherein the means to transfer includes a fan element for transferring said vapour phase chemical to the conduit.

6. A system as claimed in any preceding claim wherein means are provided to control the residency of the liquid phase chemical within the microwave cavity.

7. A system as claimed in claim 6 wherein sensor means are provided within the conditioning system and are connected to said control means to adjust the quantity of liquid phase chemical resident in the microwave cavity in response to an output from said sensor means.

8. A system as claimed in any preceding claim wherein the means to transfer includes a meter sensing quantity of vapour phase chemical transfer to the conduit, and control means are provided to operate the microwave cavity in response to an output from the meter.

9. A system as claimed in any preceding claim being an air conditioning system.

10. A conditioning system substantially herein described with reference to the accompanying drawing.