WO2010041071A1

WO2010041071A1 - Air cleaning apparatus

Info

Publication number: WO2010041071A1
Application number: PCT/GB2009/051338
Authority: WO
Inventors: Malcolm Messiter
Original assignee: Grid Xitek Ltd
Priority date: 2008-10-08
Filing date: 2009-10-08
Publication date: 2010-04-15
Also published as: GB2464170B; GB2464215B; GB0909893D0; GB0917622D0; GB0909890D0; GB2464170A; GB0818372D0; GB2464215A

Abstract

A process for cleaning breathable air in an environment meant for human occupancy is disclosed; in an air conditioning unit, the first step is to increase the temperature of the incoming air significantly above ambient and its absolute water vapour content to a point where the relative humidity is close to 100%. The heated, humidified air is then passed through a cold region; the air becomes supersaturated with water vapour which then condenses to water droplets using any suspended particles as nucleation centres.

Description

AIR CLEANING APPARATUS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an air cleaning apparatus adapted to providing clean, breathable air in an environment meant for human occupancy.

2. Technical Background

There are various instances in which it is desirable to clean the breathable air in an environment meant for human occupancy. Hay fever sufferers may wish to breathe air that is free from particles of pollen. Those with other allergies may wish other airborne particulates to be removed from the air. Others may want the removal of dust, cooking fumes, tobacco smoke, bacteria, fungal spores and viruses. These requirements could also be extended to other enclosed spaces, such as inside vehicles, inside aeroplanes, and in hospital rooms such as for patients with acute allergy symptoms. In industrial clean rooms, the amount of airborne particulates has to be kept below a maximum permitted level. Cleaner air may also be of benefit in industrial or in office, hospital, shopping centre, sports centre or hotel environments. Cleaner air may be of benefit inside military vehicles. Air may also be cleaned before release into the environment, such as after industrial processes or after automotive combustion processes. The quantities of matter which should be removed from the air in these cases are typically moderate or less.

Presently available systems for filtering unwanted matter from breathable air in an environment designed for human occupancy suffer from a number of drawbacks. The filters usually block larger particles, but therefore allow small particles to pass through freely, which means they are not effective at capturing pollen or smoke particles. Filters become increasingly inefficient as the number of particles trapped on them increases. Filters require regular cleaning or replacement. Filters impose a resistance to the air flow, hence they require the use of stronger fans to ensure sufficient air flow rates. Leakage can occur around the filter housing, reducing the effectiveness of the filter.

Another presently available system for removing unwanted matter from air is the use of HEPA filters. These filters have numerous complex pathways through them. But if a pathway traps a particle, the pathway becomes blocked, restricting air flow. To obtain a sufficiently high air flow rate, very powerful air pumps are required. If powerful pumps are not used, then the low flow rate means that even small leaks upstream of the filter can render the filter ineffective. The filters are also relatively expensive. The filters become progressively more clogged and eventually have to be replaced. Hence the cost of this system tends to prevent its widespread use.

Another presently available system for removing unwanted matter from air is the use of electrostatic filters. Particles are removed through electrostatic attraction to a plate. But the particles tend to be good insulators. After a while the plates become covered with particles and further particles tend not to be cleaned from the air.

There are some instances in which large amounts of particulates should be removed from the effluents of industrial processes. Because these are not relevant to providing clean, breathable air in an environment meant for human occupancy, they are not prior art to the present invention, but we will discuss them briefly here for completeness. Examples are disclosed in EP0555474A1, which deals in the effluent from smoke stacks; JP 10227483, which describes an air cleaner situated in a machine room; GB1492604, which deals with polluted effluent; and US 4227895 which describes a device that cleans lint from the air outlet of a textile dryer.

In the air handling area, one can draw a distinction between process applications and comfort applications. Comfort oriented applications are designed to provide an environment that is comfortable for humans. Process oriented applications on the other hand are designed to provide an environment suitable for an industrial process. JP2000-042350A (TOYO, JP63-119832A (MATSUSHITA), and JP1-315306A

(MITSUBISHI) provide various apparatus for cleaning air. But all are process oriented - typically aimed at providing ultra-clean air for clean rooms used in multi-billion dollar semiconductor fabrication plants. They are not comfort oriented, and are hence very different from conventional air conditioning devices, whose principal purpose is to chill and reduce the humidity of air inside a domestic room for the comfort of its inhabitants.

Reference may also be made to JP2005-106358A (RICOH); although this is aimed at cleaning the air in homes and offices, it is not an air conditioning device, but is purely an air cleaner.

Overall, in the comfort oriented area, the prior art includes air cleaners that are not effective as air conditioners, and air conditioners that are not effective as air cleaners. This invention addresses this gap.

SUMMARY OF THE INVENTION

The present invention is an air cleaning apparatus adapted to providing clean, breathable air in a room meant for human occupancy; the apparatus includes: (a) an air inlet through which breathable air passes, the breathable air including small particulates;

(b) a humidifying region in which the air is subject to a process that increases the amount of water vapour it contains;

(c) a heating element adapted to heat air and/or water that is in the humidifying region; (d) a condensing region in which water vapour cools and nucleates around some of the particulates forming liquid water; wherein the apparatus is operable also to function as a conventional air conditioning apparatus whose principal purpose is to chill and reduce the humidity of air inside a room for the comfort of its occupants.

Clean, breathable air is output from the apparatus; the particulates, trapped in the water, can be disposed of. This invention is a hybrid, dual-use design that combines air cleaning functionality with air conditioning functionality, for comfort oriented applications, such as keeping the air in a domestic room both clean and at a desirable temperature for the comfort of its occupants.

In a preferred implementation, the apparatus is an adaptation of a conventional domestic air conditioning unit, in which the air inlet feeds a humidifier unit including the heating element. Heated, humidified air is then sent to the condensing portion of the conventional air conditioning unit. As water vapour cools, it nucleates around some of the particulates forming liquid water, trapping those particulates and hence cleaning the air.

Hence, conventional air conditioning devices can be adapted to include an air purification function by the inclusion of a humidifying region. The latent heat of evaporation must be provided in the humidifier to create water vapour from water. We may heat the water, or the air, or both. The amount of heat needed will vary according to various factors including: the temperature of the incoming air; the humidity of the incoming air; the temperature at which we wish to emit the cleaned air, and the amount of cleaning needed. More cleaning will result from the use of more water, which will use (and return, in the condensing region) more latent heat. An air temperature as low as 20° C may be sufficient, for example — the critical thing is for there to be sufficient latent heat to create sufficient water vapour.

Further, where the ambient air is already very warm, it may be sufficient to humidify that air without actually heating it. Equally, where the ambient air is already very hot and also humid, it may sufficient to neither heat nor humidify it. But the apparatus itself must be capable of doing those things, if necessary. The temperature and humidity of incoming air should be measured by the apparatus to determine if it is necessary; the more hot and humid the air is, then the less heat and water vapour is needed. The air should however meet a predefined range of warmth and humidity when it reaches the condensing region.

Core advantages of an implementation are:

(1) Removes particulate pollutants across a wide range of sizes.

(2) Removes water soluble gases.

(3) High efficient airflow rate as there is no filter.

(4) No filter is used, so no replacement filters needed.

(5) No deterioration of performance over time. (6) No accumulation of dirt within apparatus.

(7) Can also be used to control temperature and humidity in a single unit.

(8) It can be added as a component to existing air conditioning products.

(9) Constitutes a dual-use device, with both air cleaning and air conditioning capabilities.

Other, optional implementation features include one or more of the following:

• heat generated by the latent heat of condensation is used by the heating element. • the humidifying region may subject the air to heating to over 40° C using the heating element, irrespective of the temperature of the incoming air, and water vapour is introduced into or formed in the region.

• in the humidifying region, liquid water is heated to more than 40⁰C but less than 100⁰C using the heating element to generate the water vapour. (A lower temperature may also be sufficient; also where the ambient air is already very warm, it may be sufficient, as noted above, for the heating element to be used solely to heat water).

• the heating element heats the air or water to over 40⁰C but under 100° C (e.g. so that no pure jet of steam is generated) • the user can increase or decrease the temperature of the heating element; a higher temperature will lead to removal of more particulates.

• the small particulates include one or more of: pollen, dust, tobacco smoke, fungal spores, other allergens.

• the humidifying region includes an ultrasonic water vapour generator to generate a fine mist, which in turn leads to increased water vapour content through evaporation of the water droplets in the mist.

• the humidifying region includes no water or steam jets or nozzles. Instead, it relies simply on evaporation from warm water.

• the output air is temperature controlled for user comfort. • the principal purpose of the apparatus is to clean air inside a region, as opposed to cleaning air from outside and pumping that cleaned air into a region. It may also be used to clean air taken in from the outside into a region.

• the environment includes one or more of a domestic home; an office; a shop; a hospital; a hotel — anywhere that the comfort oriented benefits of the present invention are desirable.

• the environment is a mobile environment, such as the environment inside an automobile, an aircraft, a train, a bus or a truck.

• Although we have used the term 'water vapour', it is possible to use liquids other than water. For example, butanol can be used, but is costly. The term 'water' and 'water vapour' should be expansively construed to mean any suitable liquid and its gaseous form. Another aspect is a method of providing clean, breathable air in an environment meant for human occupancy, the method comprising:

(a) passing breathable air through an air inlet, the breathable air including small particulates;

(b) in a humidifying region, subjecting the air to a process that increases the amount of water vapour it contains;

(c) using a heating element to heat air and/or water that is in the humidifying region;

(d) using a condensing region in which water vapour cools and nucleates around some of the particulates forming liquid water; comprising the further step of operating as a conventional air conditioning apparatus whose principal purpose is to chill and reduce the humidity of air inside a room for the comfort of its occupants.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram of an apparatus according to an implementation of the invention. Figure 2 is a diagram of an apparatus according to an implementation of the invention. Figure 3 is a diagram which shows the mass of water in saturated water vapour in a cubic metre of air as a function of temperature, for temperatures in the range from 0⁰C to 100⁰C. Figure 4 shows sets of data on the number of particles detected for various particle size classes as a function of time during a test of an implementation of the invention. Figure 5 is a diagram of an apparatus according to an implementation of the invention. Figure 6 shows modelled cleaning rates for a room, in which leakage of outside air into the room is included in the model. Figure 7 is a schematic overview of an implementation of the invention.

DETAILED DESCRIPTION

Overview

An implementation of the present invention is intended for use in cleaning breathable air which contains unacceptable levels of contaminants such as pollen, dust, bacteria, tobacco smoke, pet allergens, fungal spores and viruses. The target particle size varies from IOnm through to 100 micrometres. It is possible also to remove even smaller particles, such as very small viruses.

The cleaning process increases the temperature of the incoming air and its absolute water vapour content to a point where the relative humidity is close to 100% and temperature is significantly greater than ambient. A key advantage of this implementation over, for example, HEPA filter systems, is the practicality of achieving a very high flow rate. The heated, humidified air is then passed through a cold region when the air becomes supersaturated with water vapour which then condenses to water droplets using any suspended particles as nucleation centres. During cooling, the airflow passes through a restricted space where the water droplets will contact the sides of a cooled heatsink and adhere to the surface. As the droplets build up they will acquire sufficient mass to overcome surface tension and run to a collection region in the base of the heatsink. When leaving the cooled region the air will now be below ambient temperature and can be adjusted for overall heating or cooling.

The potential market for this technology can be split into those applications where particles must be removed from the air to improve the air quality of the immediate environment:-

o Domestic air cleaning products o Industrial/office environments o Aeroplane cabins o Automotive cabins o Medical facilities O Military vehicles The market for improved cleaning technology is therefore large and extensive where every business sector, worldwide, would have potential applications for an efficient, low cost and non-intrusive product that efficiently removed particulates from a gas.

Implementation using a modified conventional air conditioning unit

Since evaporation occurs when heat is absorbed, and condensation occurs when heat is released, air conditioners are designed to use a compressor to cause pressure changes between two compartments, and actively pump a refrigerant around a closed system. A refrigerant is pumped into the low pressure compartment (the evaporator coil), where, despite the low temperature, the low pressure causes the refrigerant to evaporate into a vapor, taking heat with it. In the other compartment (the condenser), the refrigerant vapour is compressed and forced through another heat exchange coil, condensing into a liquid, rejecting the heat previously absorbed from the cooled space. The heat exchanger in the condenser section is cooled most often by a fan blowing outside air through it.

An implementation of the invention is shown in Figure 1. 10 is the apparatus used in the implementation of the invention which comprises principally a humidification unit 11 and an air conditioning apparatus 12. Air 13 which has been heated by some means 29, such as by an electric fan heater, enters the humidification unit 11. The humidification unit 11 comprises at least a water reservoir 15 in which the water may be temperature controlled, and a mixing volume 14 in which the input air 13 is rendered more humid. A fan 16 assists in drawing air 13 into volume 14 and sending it into linking duct 17. Air from linking duct 17 enters the air conditioning apparatus 12. Typically, in use the standard filter present in air conditioning apparatus 12 is removed and is not used. 18 is the part of the air conditioning apparatus 12 which houses the evaporator coil. Here the humid air is cooled, causing nucleation of water droplets. These water droplets may nucleate on unwanted matter, which thereby removes unwanted matter from the air. The principle of water droplet nucleation on unwanted matter is disclosed in EP0555474A1, for example, and relates to the Kelvin-Thomson law. The condensed water flows away through waste water pipe 28 to waste water receiver 27. If the contamination level of the waste water is acceptable, the waste water may be disposed of in a drain. Fan 23 expels the cleaner air 26 with reduced humidity content into the room. In use, the air conditioning unit 12 has a compressor 19 which draws refrigerant vapour from 18 to the condenser 20. After condensing in the condenser 20 to form a liquid, the refrigerant flows back to 18 via pipe 21. The condenser 20 is cooled using fan 22 which draws in air 24 which is expelled as warmer air 25. The air 24 and 25 may be air outside the room, or air inside the room, or air 24 may be inside the room and air 25 may be outside the room, or vice versa.

A preferred implementation of the invention is shown in Figure 2. 40 is the apparatus used in implementation of the invention which comprises principally a humidification unit 41 and an air conditioning apparatus 42. Air 43 which has been heated enters the humidification unit 41. The humidification unit 41 comprises at least a water reservoir 45 in which the water may be temperature controlled, and a mixing volume 44 in which the input air 43 is rendered more humid. A fan 46 assists in drawing air 43 into volume 44 and sending it into linking duct 47. Air from linking duct 47 enters the air conditioning apparatus 42. Typically, in use the standard filter present in air conditioning apparatus 42 is removed and is not used. 48 is the part of the air conditioning apparatus 42 which houses the evaporator coil. Here the humid air is cooled, causing nucleation of water droplets. These water droplets may nucleate on unwanted matter, which thereby removes unwanted matter from the air. The condensed water flows away through waste water pipe 58 to waste water receiver 57. Fan 53 expels the cleaner air 56 with reduced humidity content into the room, where the temperature of air 56 is a well-controlled quantity. In use, the air conditioning unit 42 has a compressor 49 which draws refrigerant vapour from 48 to the condenser 50. After condensing in the condenser 50 to form a liquid, the refrigerant flows back to 48 via pipe 51. The condenser 50 is cooled using fan 52 which draws in room air and/or outside air 54 which is expelled as warmer air. At least some of the warmer air is sent as 43 to supply the humidification unit 41 which thereby enables waste heat from the air conditioning process to be used to heat the air supplied to the humidification unit 41, which improves energy efficiency. Optionally, the temperature of air 43 may be further raised by heater 59. Some of the warmer air expelled by the fan 52 may be released into the room or outside the room as hot air 55. A further implementation of the invention is shown in Figure 5. 80 is the apparatus used in implementation of the invention. Room air 95 is drawn into the humidification unit 82 by fan 81. The air flow rate through fan 81 may be about 2 cubic metres per minute, or more, or less. The humidified air travels through a mixing space 83 which permits the air to obtain relatively homogenous properties in terms of its temperature and humidity. The air then encounters cooled unit 84 on or near to which moisture may condense, thereby removing unwanted matter from the air. Unit 84 is cooled using thermoelectric cooling system 92. The heat removed by thermoelectric cooling system 92 is removed to heatsink 85. Thermoelectric coolers may provide greater control of the cooling level than in conventional air conditioners. Condensed moisture flows along waste pipe 93 to waste water collector 86. Alternatively, if the waste water contamination level is acceptably low, the waste water may flow to water tank 88. However, in this event, some method of water sterilization may be preferable to prevent mould growth. Water from water tank 88 is drawn by pump 87 through pipe 89 and pumped down pipe 90, where it cools heat sink 85. The water, which is thereby heated up, flows along pipe 91 to be used in humidifying humidifier 82. The water in pipe 91 may be heated further before being used in humidifier 82. The water flowing along pipe 91 may be at a temperature of about 50⁰C to 70⁰C. Cleaned air 94 which is emitted by the apparatus 80 may be at a temperature of about 20⁰C to 30⁰C. Different implementations may use different temperature ranges.

The unit 80 in Figure 5 is preferably computer controlled. Temperature monitors may be placed to determine the local temperature in unit 80 such as at items 82, 83, 84, 85, 91, 81, 88 and 94. Temperatures could be monitored using thermistors which could interface to a computer. The unit 80 could be controlled using a USB digital to analogue converter (DAC) connected to a personal computer. The thermoelectric cooling system may be computer controlled. The humidity may also be monitored at items 95, 82, 83 and 94 by the computer.

In Figure 1, the air heater 29, the humidification unit 11 and the air conditioning unit 12 may be standard commercially available items sold for household use. Alternatively, they may be designed with the purpose of comprising an integrated system 10 with an optimized level of efficiency. In Figure 2, the humidification unit 41 and the air conditioning unit 42 may be standard commercially available items sold for household use. Alternatively, they may be designed with the purpose of comprising an integrated system 40 with an optimized level of efficiency.

The systems 10, 40 and 80 of Figures 1, 2 and 5 respectively may also be used to control both temperature and humidity. For example, if a relatively high humidity in a room is required, the air may be drawn quickly through the air conditioning unit so as to reduce the amount of water vapour condensation, thereby providing an output with controllable humidity to the room. The air may be emitted by the system at a temperature which is greater than, or less than, the original ambient temperature by a controlled amount.

The systems 10, 40 and 80 of Figures 1, 2 and 5 respectively may also be used to protect the occupants of a room against the effects of a biological, chemical or nuclear attack which may be a military attack or a terrorist attack. In such attacks, dangerous amounts of biological agents, chemicals or radioactive matter may be released into the environment. Even though a room may be leaky, the air cleaning apparatus of the invention may be able to keep the levels of such matter in the room to levels low enough to improve the chances of the occupants of the room surviving the attack over the case where no air cleaning apparatus of the invention is available.

The systems 10, 40 and 80 of Figures 1, 2 and 5 respectively have the following in common. The systems all employ a method of cleaning air in an enclosed space comprising the steps of drawing air of the enclosed space into a first part of an apparatus whereby the air is heated and humidified, drawing the resulting air into a second part of the apparatus whereby it is cooled and the water vapour in it becomes supersaturated, such that some of the supersaturated water vapour in the second part of the apparatus nucleates on particles of unwanted matter, causing the unwanted matter to be collected in a flow of water which exits the second part of the apparatus, characterized in that the temperature of the heated and humidified air in the first part of the apparatus is at least 20⁰C and is less than 100⁰C. In application in a room environment, the water supplied to provide humidity may come from a bottle or a similar volume container, which may require refilling once a day or so, but connection to the mains water supply is possible. In application in an industrial clean room environment, or in a single system for a sizeable workplace, it may be preferable to connect the water supply to the mains water supply, as relatively large volumes of water, such as a litre per hour, may be required. Small units may be used for application inside vehicles for example.

Figure 3 shows a plot of the mass of water that comprises saturated water vapour for a cubic metre of air at atmospheric pressure, as a function of temperature. It is clear that there is a very large increase in the maximum amount of water vapour which may be present in air at equilibrium as the air temperature is increased from zero degrees Celsius to 100 degrees Celsius. The implication is that if very large amounts of unwanted matter are to be removed from air using the nucleation of water vapour on the matter, it is desirable to introduce the water vapour to the air at as high a temperature as possible, such as by boiling the water to produce steam at a temperature of at least 100 degrees Celsius. However, if the amounts of unwanted matter to be removed from the air are less, other considerations may lead to the conclusion that the maximum temperature in the process used for removing the unwanted matter from the air could be less than 100 degrees Celsius. For example, a temperature between 40 degrees Celsius and 100 degrees Celsius may generate sufficient mass of water vapour in the air to remove moderate amounts of unwanted matter from the air in various circumstances. The temperature can be user controlled — so for example, someone suffering from severe allergies may wish to use the highest possible temperature, despite the fact that considerable power will be consumed. The appropriate temperature levels will also depend on the air flow through the apparatus: routine empirical studies can be used to determine the appropriate temperature levels and ranges appropriate to a given design of apparatus, using a given flow of air.

It will be appreciated by those skilled in the art that there exists an optimum level of humidity in the air cleaning apparatus. If the level of humidity is too high, there will be many condensed water droplets which do not capture a particle of unwanted matter. Hence energy will have been wasted in generating humidity and condensing water droplets. However, if the level of humidity is too low, the rate of removal of unwanted matter from the air will be too low, and the cleaning rate will be unsatisfactory. Hence in a given situation there will exist an optimum level of humidity which is a trade off between the cost of generating and removing the humidity, and the air cleaning rate desired.

There are various reasons why an air temperature below 100 degrees Celsius may be preferable for removing unwanted matter from air in moderate quantities or less. For example, raising the air temperature from the ambient temperature to 100 degrees Celsius requires more energy than raising the temperature from the ambient temperature to a lower temperature than 100 degrees Celsius. In a domestic setting, a temperature within the air cleaning apparatus of up to 100 degrees Celsius may pose a thermal hazard as parts of the apparatus may become unacceptably hot or dangerously hot to the touch. In addition, the hot air generated requires cooling to an ambient temperature by the air conditioning apparatus. The hotter the air, the greater will be the energy required to accomplish this process. However, it is clear that there is still an advantage in raising the air temperature in the humidifier above the ambient temperature, because of the greater quantity of water vapour which is present in saturation at greater temperatures. For example, by Figure 3, whereas a cubic metre of air at 100 degrees Celsius contains 584 g of water vapour at saturation, a cubic metre of air at 20 degrees Celsius contains only 17 g of water vapour at saturation. A further advantage is that at more elevated temperatures mould growth in the humidifier is inhibited.

A relatively high flow rate through the air cleaning apparatus is required if an effective rate of removal of unwanted matter from the air is to be achieved. Assuming a filter efficiency C which is independent of particle size, it is trivial to show that the ratio of the number of particles P in a room as a function of time t, given by the function P(t), relative to the number of particles in a room at t=0, P(O), is equal to

P(t)/P(0) = Exp[-F C t/V], where P(O) is the number of particles at t=0, F is the flow rate of air through the air cleaner, and V is the volume of the room, and we have ignored ingress of particles into the room eg. it is assumed that windows and doors are closed and are relatively well sealed. Hence for a totally efficient filtering process C = I, for a small bedroom with a volume V of 30 cubic metres, and a flow rate F of 2 cubic metres per minute, at t=30 minutes the fraction of unwanted particles remaining is Exp[ -2*1*30/30], which is about 14%. If the conditions are identical, except that F is 1 cubic metre per minute, at t=30 minutes the fraction of unwanted particles remaining is Exp[ -1*1*30/30], which is about 37%. If the conditions are identical, except that F is 3 cubic metres per minute, at t=30 minutes the fraction of unwanted particles remaining is Exp[ -3*1*30/30], which is about 5%. Hence flow rates of about one or two cubic metres per minute are likely to be the minimum acceptable amount in typical domestic situations. A typical leak rate into a room would be about 0.1 cubic metres per minute, which would not alter the results calculated here very much.

A more sophisticated model of the time evolution of P(t) is given by

P(t+1) = P(t) - [P(I) F C] /V + [P(O) - P(t)] Pleak/V

Where Pleak is the rate of leakage into the room. Modelling results are shown in Figure 6, where Pleak is 0.1 cubic metres per minute, V is 30 cubic metres, C = I, and F takes various values. In curve 100, F is 0.5 cubic metres per minute. In curve 101, F is 1.0 cubic metres per minute. In curve 102, F is 2.0 cubic metres per minute. In curve 103, F is 4.0 cubic metres per minute. The results show that when leak rates are fairly low, such as 0.1 cubic metres per minute, they do not affect the rate of air cleaning very much, at least in the initial stages of cleaning, such as during the first hour.

It will be appreciated by those skilled in the art that the present invention may be implemented by using any known humidification process including mechanical humidification, ultrasonic humidification, pressure mist jet humidification or spinning disc humidification. It will also be appreciated by those skilled in the art that some external air may be fed into the air cleaning device which will generate a pressure in the room which is slightly in excess of the pressure outside the room, thereby reducing the rate of external particle ingress.

EXAMPLE

This is an example of the invention according to Figure 1. The air conditioning unit in this example was an Amcor PLM 15000EH air conditioning unit, with a cooling capacity of 3,500 W, or 12,000 BTU/h, a power consumption of 1,330 W, a refrigerant charge of R407C 720 g, and an energy efficiency rating (EER) of 2.65. The humidifier was a small domestic unit Air-O-Swiss home humidifier, with a height of 335 mm, a width of 422 mm, a depth of 284 mm, with a humidifying capacity of 300 ml/h a dry weight of 3.8 kg, a water tank volume of 8 litres and a power consumption of 20 W.

In this example of the invention, the room size which contained the apparatus was 2.85 m by 4.45 m by 2.5 m which gave a room volume of about 30 cubic metres. The air used to cool the air conditioner condenser was taken from outside the room and was vented outside the room.

In one case, ambient air at 26 ⁰C was supplied to the humidifier. The temperature of the humidified air leaving the humidifier was measured to be 23 ⁰C. The temperature of the air emitted by the air conditioner was measured to be 12 ⁰C. In a further case, ambient air at 25

⁰C was heated by a heater to 47 ⁰C. The heated air was supplied to the humidifier. The temperature of the humidified air leaving the humidifier was measured to be 35 ⁰C. The temperature of the air emitted by the air conditioner was measured to be 15 ⁰C. In both cases, the air cools as it passes through the humidifier, due to evaporative cooling and/or thermal losses to the humidifier container. It should be noted that this temperature drop is due to the latent heat of evaporation; it is always the same amount of heat that is regained as the latent heat of condensation, in the condensing chamber. This leads to high levels of energy efficiency. A test was performed of the performance of the system, where heated air was supplied to the humidifier. The room door and windows were closed. These were considered to leak negligibly for the purposes of this test. A Grimm 108 pollution monitoring device, manufactured by Grimm Technologies of Douglasville, Georgia, USA, was used to characterize the air output from the air in the room. The device sampled the air over six second intervals, and recorded the number of particles found during the interval as a function of particle diameter. The data is shown in Figure 4 as a function of time. In Figure 4, data set 70 corresponds to particle diameters between 7.5 μm and 10 μm, data set 71 corresponds to particle diameters between 5.0 μm and 7.5 μm, data set 72 corresponds to particle diameters between 4.0 μm and 5.0 μm, data set 73 corresponds to particle diameters between 3.0 μm and 4.0 μm, data set 74 corresponds to particle diameters between 1.6 μm and 2.0 μm, data set 75 corresponds to particle diameters between 2.0 μm and 3.0 μm, and data set 76 corresponds to particle diameters between 1.0 μm and 1.6 μm. Data sets were also measured for particles in the diameter range from 10 μm to 15 μm, from 15 μm to 20 μm, and for diameters greater than 20 μm. These three data sets showed trends similar to data set 70, but the number of particles measured were fewer than in data set 70, hence these data sets are not shown in Figure 4.

In Figure 4, about seven minutes after the start of the test a small amount of pollution was introduced to the room air. A small cigar was lit and was extinguished after about a minute, to introduce some smoke into the room. A small flower was shaken to release some pollen at about the same time. The air cleaning device was switched on at about the same time. The data in Figure 4 shows that after about 30 minutes from switching on the device the quantities of particles in the room were similar to or lower than the levels that were present prior to the introduction of pollution to the room air. The room door was opened about 58 minutes after the start of the test: the resulting increase in particle numbers is visible in

Figure 4. A similar test using a pollution monitoring device manufactured by TSI

Instruments Ltd, High Wycombe, UK, showed similar behaviour for particle sizes down to about 10 nm. For the sake of comparison, the test was repeated using the Grimm 108 pollution monitoring device with the air cleaning device switched off throughout. The decline in particle numbers recorded was much slower than when the air cleaning device was switched on and was consistent with a slow leakage of particles out of the room through the windows and doors. The test results demonstrate that the air cleaning device is effective in removing unwanted matter from room air.

Finally, Figure 7 is a schematic and self-explanatory overview of an implementation. In the Figures herein, the relative dimensions shown are not necessarily to scale.

In an implementation of the invention, the humidification process may be turned off, which then permits the apparatus to function as a conventional air conditioning apparatus. This may be desirable when there is no requirement by the user or users of the system for the air to be cleaned. Such an apparatus may have a filter on its air input port, as with a conventional air conditioning apparatus.

Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

Claims

1. An air cleaning apparatus adapted to providing clean, breathable air in a room meant for human occupancy, the apparatus including: (a) an air inlet through which breathable air passes, the breathable air including small particulates;

(c) a heating element adapted to heat air and/or water that is in the humidifying region; (d) a condensing region in which water vapour cools and nucleates around some of the particulates forming liquid water; wherein the apparatus is operable to function as a conventional air conditioning apparatus whose principal purpose is to chill and reduce the humidity of air inside a room for the comfort of its inhabitants.

2. The apparatus of Claim 1, being an adaptation of a conventional air conditioning unit, in which the air inlet feeds a humidifier unit including the heating element and the humidified air is sent to the condensing portion of the conventional air conditioning unit.

3. The apparatus of Claim 1 or 2 in which heat generated by the latent heat of condensation is used by the heating element.

4. The apparatus of any preceding Claim in which the humidity of the incoming air is measured by the apparatus to determine the extent to which it is necessary to increase the amount of water vapour it contains.

5. The apparatus of any preceding Claim in which the temperature of the incoming air is measured by the apparatus to determine the extent to which it is necessary to heat the air.

6. The apparatus of any preceding Claim 4 or 5 in which the apparatus operates to feed air falling within a pre-defined range of warmth and humidity when it reaches the condensing region.

7. The apparatus of any preceding Claim in which the humidifying region subjects the air to heating to over 40° C using the heating element, irrespective of the temperature of the incoming air, and water vapour is introduced into the region.

8. The apparatus of any preceding Claim in which, in the humidifying region, liquid water is heated to more than 40° C but less than 100° C using the heating element to generate the water vapour

9. The apparatus of any preceding Claim in which the heating element heats the air or water to over 30° C but under 100° C.

10. The apparatus of any preceding Claim in which the user can increase or decrease the temperature of the heating element.

11. The apparatus of Claim 10 in which a higher temperature will lead to removal of more particulates.

12. The apparatus of any preceding Claim in which the small particulates include one or more of: pollen, dust, tobacco smoke, fungal spores, other allergens.

13. The apparatus of any preceding Claim in which the humidifier does not include steam jets.

14. The apparatus of any preceding Claim in which the humidifying region includes an ultrasonic water vapour generator.

15. The apparatus of any preceding Claim in which the humidifying region includes no water or steam jets or nozzles.

16. The apparatus of any preceding Claim in which the output air is temperature controlled for user comfort.

17. The apparatus of any preceding Claim in which the principal purpose of the apparatus is to clean air inside a region, as opposed to cleaning air from outside and pumping that cleaned air into a region.

18. The apparatus of Claim 17 which is also used to pump clean air from outside into a region.

19. The apparatus of any preceding Claim in which the environment includes one or more of a domestic home; an office; a shop; a hospital; a hotel.

20. The apparatus of any preceding Claim in which the environment is a mobile environment meant for human occupancy.

21. The apparatus of Claim 20 in which the environment is inside an automobile.

22. The apparatus of Claim 20 in which the environment is inside an aircraft.

23. The apparatus of Claim 20 in which the environment is inside a train.

24. The apparatus of Claim 20 in which the environment is inside a bus.

25. The apparatus of Claim 20 in which the environment is inside a truck.

26. A method of providing clean, breathable air in an environment meant for human occupancy, the method comprising:

(a) passing breathable air through an air inlet, the breathable air including small particulates; (b) in a humidifying region, subjecting the air to a process that increases the amount of water vapour it contains;

(d) using a condensing region in which water vapour cools and nucleates around some of the particulates forming liquid water; comprising the further step of functioning as a conventional air conditioning apparatus whose principal purpose is to chill and reduce the humidity of air inside a room for the comfort of its inhabitants.