Patent Application
20170299207
The present invention relates to a localised personal air conditioning system and to an air conditioning unit for a localised personal air conditioning system.
Conventional air conditioning devices work mostly by injecting cool air into an enclosed space in which cooling is desired. The air is injected in a way that results in mixing of the air in the space to achieve a relatively uniform temperature and perceived comfort level at any location in the enclosed space. Usually the air is injected by a fan in the air conditioner through one or more vents at relatively high velocity to create mixing throughout the enclosed space. In a displacement air conditioning system, the air is injected at the bottom of the space to create a cool air layer only in the lower section of the space occupied by people.
The air conditioner removes heat from the air by passing it through a “cold side” heat exchanger containing a cool fluid, or a heat exchanger cooled by some other mechanism such as the Peltier (or thermoelectric) effect. In this specification, the terms “evaporator” and “condenser” respectively refer to the cold side and the hot side heat exchangers. However the scope of the specification is not limited to compressor-refrigeration cooling.
The air inside the cooled space absorbs heat from the walls, floor, people and other objects inside the space being cooled.
Usually, but not always, the air inside the cooled space is recirculated through the cold side of the air conditioner to reduce the energy required to maintain cooling.
The heat absorbed from the cooled space air (including the latent heat obtained by condensing water vapour to liquid water) at the evaporator reappears at the hot side of the air conditioner. Outside air is passed through the condenser and increases in temperature as it absorbs heat from the condenser. The energy used to compress the refrigerant gas also appears at the condenser. Therefore the heat transferred to the warm outside air at the condenser is greater than the heat absorbed from the cooled space air at the evaporator by an amount equal to the electrical energy supplied to the compressor and fans (apart from relatively small amounts of heat lost from the system by other means). The coefficient of performance of the air conditioner is the rate at which heat is absorbed from the cooled space (including the latent heat obtained by condensing water vapour to liquid water) divided by the electrical power supplied to the compressor.
In essence the air conditioner operates as a heat pump, removing heat from air inside the cooled space in the cold side of the air conditioner and transferring this heat, along with the energy used to compress the refrigerant gas, to warmer air outside the cooled space in the hot side of the air conditioner. In the case of a split system air conditioner, the cold side and the hot side are physically distinct components at some distance from each other. In addition to the power required to run the compressor, a small additional amount of power is needed to run the fans to move the inside and outside air.
A portable air conditioner can be constructed from an air conditioner similar to known domestic air conditioners. The air conditioner is usually placed inside the room to be cooled and, therefore, a relatively large diameter air tube is required to ensure that hot air from the condenser is exhausted through a window. In some cases, a second air tube carries air from the window to the condenser circulation fan to be pumped through the condenser. The cool air mixes with the room air or, in the case of some inventions discussed below, is directed into a localized part of the room.
A substantial part of the energy used in these conventional air conditioning arrangements results only in cooling of the building structure and the objects inside the cooled space, and removal of heat entering through the roof or ceiling, walls, floor and particularly through open or covered apertures such as the windows and doors. This energy requirement can be reduced by providing additional insulation or by shading the roof, walls, windows and doors. However, these measures are not always possible, particularly with older buildings not designed with energy efficiency in mind.
By localizing the effect of an air conditioner to just a small section of the cooled space, typically away from doors, windows and walls, very large energy savings are possible. People often spend long periods of time at a single location within a room (such as sleeping on a bed) and it is only necessary to keep the upper body and face cooled for a person to feel very comfortable.
This principle has been described in U.S. Pat. No. 6,425,255 by Karl Hoffman, Dec. 26 2000 (issued Jul. 30 2002). Further refinements are described in US Patent 2002/0121101 by AsirlyaduraiJebaraj, 2 Jan. 2002 (issued 5 Sep. 2002). This patent also refers to China Patents CN2259099 (San Jianhua et al) and CN1163735 (Tan Mingsen et al) that describe air-conditioned mosquito nets in which outside air is conditioned and supplied to the enclosures and all of the air is exhausted outside the enclosure. China patent CN1061140 (He BaoAn et al) describes an insulating mosquito net with a plurality of inflatable air-pocket walls. Chinese developments also include localised air conditioning for seats in an auditorium.
These were preceded by U.S. Pat. No. 2,159,741 by C. F. Kettering et al, 30 Aug. 1933 (issued 23 May 1939) describes a fabric wall structure around the bed and a small air conditioning unit feeding air into the enclosed walled space over the bed. This invention exploited the displacement air conditioning principle in which it is known that cool air is denser than warmer air and thus remains in the walled enclosure over the bed.
Attempting to localize air conditioning by using a mosquito net, even with relatively fine weave, is inefficient. This difficulty was recognized in CN2803143Y in which the interior of the mosquito net is subdivided with an interior curtain such that only the head of the sleeping person is inside the air conditioned section. The slight density difference between cooler air inside the enclosure and the warmer air outside is sufficient to provide a pressure difference that will allow cool air to rapidly disperse through the net into the room. That is why many patents have disclosed impervious barriers to air flow. However, these can be unattractive for people who need to use the enclosure.
It is evident from the above that there is a need for a localised personal air conditioning system in which the conditioned air is used more effectively to cool a person located in a sleeping space.
Uninterruptible power supplies (UPSs) using battery storage have become popular in regions affected by frequent electricity supply interruptions because they are silent and emit no exhaust fumes. A typical UPS can supply power for several hours to operate low power fluorescent lights, communications equipment and a fan. Typical domestic UPS units can supply between 1000 and 2,500 Watts. In many markets, a high power UPS unit costs up to three times the price of the smallest air conditioner and often the batteries need to be replaced every twelve months or so.
An attractive alternative option is to supply power from a photovoltaic solar cell array through an inverter similar to those used for UPS units.
However, a typical UPS inverter cannot easily provide power for air conditioning. The reason is that the electric motor required to run the compressor (as used in a refrigeration air conditioner) draws up to ten times the normal electric supply current for a brief time, typically 50 to 100 milliseconds, when it starts operating from a stationary condition. While UPS units can supply a larger current for a short time without overloading, the power rating of the UPS unit needs to be about three times larger than the electric motor rating in order for the motor to start reliably. Therefore, one would need a UPS unit with a capacity in excess of 2,000 Watts to run even the smallest air conditioners rated at 600 Watts. Here it should be noted that some of the air conditioners said by their manufacturers to run at a relatively low power rating, for instance 450 Watts, actually require up to twice or two and a half times as much power under certain conditions, including when initially starting up. Therefore they typically cannot be run by a UPS system and instead require a generator that can supply the required power.
Many more people would be able to gain comfort and better sleep by using air conditioning if one could reduce the electric power required for the air conditioning compressor. This can be achieved by significantly reducing the cooling capacity required from the air conditioner. One way to do this is to localize the effect of the air conditioner so that only the air around the head and upper body is cooled.
A further, related problem also exists in the field. In order to achieve such a precisely localised cooling effect on a person from a reasonable distance, the cooling effect of a jet of air should be able to extend some distance from the origin of the jet. This is difficult because any turbulence in the jet is likely to promote mixing with the surrounding air, thereby reducing the velocity, and subsequently reducing the cooling sensation at the location of the person. As it turns out, the jet velocity at the location of the person is significant. For example, if the jet velocity exceeds 0.4 m/s, an additional apparent cooling of approximately 2° C. can be attained, due to the way in which the human physiology senses the apparent temperature of the surrounding air.
For a heat exchanger to operate at maximum heat transfer efficiency, a relatively uniform air velocity is required. If there is a large difference in air velocity in different parts of the heat exchanger, this reduces the effective heat exchange area, resulting in a greater temperature difference between the air in the evaporator tubes and the average temperature of the air after it passes through the heat exchanger. This means that more work needs to be done by a refrigeration compressor to achieve the same cooling effect.
The disadvantage of arrangements provided in the prior art is that air passing through the cooling side of the air-conditioner must be pushed through the evaporator heat exchanger by an air circulating fan. If a motor driven used to force air through the cold air side of an air-conditioner is located adjacent to the heat exchanger, it is difficult to achieve uniform air velocity through all parts of the heat exchanger because air leaves different parts of the fan at different velocities and sometimes different directions, depending on the design of the fan. Moreover, the air exiting the fan has significant vorticity, which can cause additional turbulence, causing the air jet to mix rapidly with the surrounding air.
In order to achieve a more uniform velocity, air-conditioner arrangements having the air pass through the heat exchanger before passing through the fan are often preferred. Undesired vorticity can be reduced through the provision of airflow straighteners. However, air flow straighteners known in the field present manufacturing challenges and have costly parts, taking up a relatively large amount of space. Any attempt to provide a practical, personal localised air conditioner is preferably compact and low-cost.
It is generally desirable to overcome or ameliorate one or more of the above mentioned difficulties, or at least provide a useful alternative.
According to the present invention, there is provided an air conditioner system including:
Preferably, the sleeping enclosure is a tent enclosing the sleeping space and inhibiting insects such as mosquitoes from accessing the skin of the people inside the enclosure. Preferably, the tent is quick-erecting and self-supporting.
The present invention also provides an air conditioner unit for generating a conditioned air flow for an air conditioner system including a sleeping enclosure defining a sleeping space into which conditioned air is adapted to be delivered from one end or side of the sleeping space in a manner which maximizes contact between the conditioned air and a person or persons in the sleeping space, the enclosure including an upper air pervious section and a lower relatively air impervious section adapted to surround a bed in the sleeping space and configured to minimize passage of the conditioned air from the sleeping space through the pervious section or other leakage paths, the air conditioner unit including:
Preferably, the evaporator fan passes air through the air straightener which comprises a series of vanes designed to reduce the exit air velocity and also to ensure that the airflow is sufficiently straightened to avoid unwanted mixing between colder air just above the sleeping surface and warmer layers of air above. Preferably, the series of vanes is designed to reduce the exit air velocity to less than 4 m/s.
The present invention also provides an air conditioner system including:
Preferably, the sleeping enclosure is a tent completely enclosing the sleeping space and inhibiting insects such as mosquitoes from accessing the skin of the people inside the enclosure.
The present invention also provides a localised cooling device including:
Preferably, the curved cold air deflector is in the form of a nozzle. Preferably, the condenser fan and the evaporator fan are centrifugal fans. Preferably, the centrifugal fan has a backward sloping impeller.
Preferred embodiments of the present invention are hereafter described, by way of non-limiting example only, with reference to the accompanying drawing in which:
The outlet of the air conditioner (1) in the embodiment described directs a stream of cool air over the bed as shown in
This overcomes a significant disadvantage of normal room air conditioners. When a room air conditioner is used, the windows must be closed. Many people dislike this and would prefer fresh air from the outside. This invention allows for the room windows to be left open. Even if they are closed, there is minimal warming of the room caused by the relatively small amount of heat released from the air conditioning unit: the net heat released to the room is only the electrical power consumption of the compressor and fans.
The means of localizing the air conditioning effectively permits this embodiment to be used outside in the open air, unlike a normal air conditioner.
When the hinged lid at the top of the unit is lowered, all air inlets and outlets are invisible and protected from dust accumulation. The air conditioning unit, therefore, resembles a normal piece of bedroom furniture when it is not in use.
Referring to
In the arrangement shown in
A jet of cool air emerges from the air cooler outlet 90 at about 2.4 metres per second (m/sec). The outlet flow rate is typically about 30-40 litres per second (I/sec), and the temperature is between about 12° and 18° . By using Bernoulli's famous equations that describe incompressible fluid flow, one can show that the static pressure of the cool air jet is lower than the surrounding air. As a result, shown in
The cool air reaches the end of the enclosure and has to stop moving horizontally. The depth of cool denser air is greater here.
The depth difference can be calculated from fundamental principles: the same principles that Bernoulli used for his famous equations that describe incompressible fluid flow. The reason for working from fundamental principles is that conventional fluid mechanics texts provide equations that describe the flow of water (or similar fluids) in channels, neglecting the density of the air above. This is reasonable because the air is usually around 800 times less dense than water.
However, in the case of the cool air within the enclosure, the warm air above is only slightly less dense than the cooler air at the bottom. Measurements show, in addition, that there is no clear boundary between the cool air and the warmer air. Instead there is a gradual transition from warmer air to cooler air over a distance of about 0.2-0.4 m. However, we can simplify the calculations by assuming that there is a distinct measurable boundary and still obtain results with sufficient accuracy.
A small elemental volume of air close to the head end has potential energy represented by the greater depth of cool air (with higher density). Away from the head end, the depth of cool air is less and this difference causes two effects. First, the air at the head end needs to recirculate back to the foot end of the bed. Second, the cool air flowing over the head and shoulders of the occupant slows down and starts moving up instead. We treat this phenomenon by equating the kinetic energy of the air in motion to the potential energy difference represented by the different depth of cool air, illustrated in
A small volume of moving air, dv, has mass ρi, dv where ρi is the density of the cool air inside the enclosure. The kinetic energy of this small volume of air is therefore 0.5ρi dv u2 where u is the velocity, mostly in the horizontal direction. The potential energy represented by the increased depth of cool air at the head end is also easily calculated. For our small volume at rest, near the head end, the potential energy is (ρi−ρa) dv g (h1 −h2). Here we use the density difference between the cool air (Pi) and the ambient air (ρa) because it is this difference that creates the small pressure difference that affects the air velocity. We can equate these two:
0.5ρidvu2=(ρi−ρa)dvg(h1−h2) (1)
Noting that dv appears on both sides of the equation, we can eliminate it. Thus we can re-arrange the equation and calculate u from:
u=(2(ρi−ρa)g(h1−h2)/ρi)0.5 (2)
Substituting the values described above, we obtain the following calculated results:
What this demonstrates is that if the difference in depth of cool air is 0.5 m, then the expected flow velocity associated with that depth difference is 0.4 m/sec that is what we observe in tests.
The cool air needs to recirculate within the enclosure, partly to provide enough air velocity to create an additional perception of comfort, and partly because the air will be entrained in the jet of conditioned air entering the bed enclosure from the cool air outlet. We can calculate how much space is required for this circulation.
The total flow of mixed cool air over the head and shoulders of the occupant O is about 180 I/sec. At a velocity of 0.4 metres/sec this requires a flow area of 0.46 m2. In fact, the velocity cannot be uniform, so a larger area will be needed, typically around 50% more. Using the measurements obtained to estimate the depth of cool air flowing over the head and shoulders of the occupant; this depth is about 0.3 m. The width of the bed is about 1.8 m, and we need almost this full width to accommodate this flow. Therefore we can conclude that the return air flows over the top of this cooler air layer back to the foot end of the bed. The combined thickness of these two layers needs to be, therefore, about 0.6 m. This corresponds to the observations from experiments. The typical depth of cool air at the head end is around 0.9-1.0 m and at the mid section about 0.4-0.5 m. When we allow for the transition layer between cool and warm air above, we need to allow more depth, and the minimum required will be about 0.1 m greater than these values.
It should be noted that a typical width across the shoulders of a person is 0.45 m. With an occupant sleeping on their side, the shoulder height is greater than the thickness of the cool air layer flowing towards the head end of the bed. However, just as running water flows up and over submerged rocks in a stream, the cool air will flow over the shoulders of the occupant. This will cause some friction flow losses however, but these do not significantly affect the levels of cool air within the enclosure.
An alternative arrangement would be to admit cool air at one end of the bed, say the head end, and extract air from the foot end of the bed to be cooled and recirculated. However, first one has to allow 0.2-0.4 metres transition layer between warm air above and cool air below. Then one has to allow sufficient depth for the air flow to rise over the shoulders of an occupant sleeping on their side, 0.45 m high. This means that the minimum depth of cool air in the enclosure has to be around 0.5 m (0.6 m after allowing for the transition layer). If the impervious part of the fabric curtain containing the cool air is lower than 0.6 m, cool air will overflow the sides of the curtain, significantly reducing the efficiency of the air cooling. In addition significant ducting will be needed to transport the air from one end of the bed to the other end. This ducting is a further source of heat gain due to conduction, reducing the efficiency. Since it is desirable to admit cool air at the head end in this arrangement, there is a further problem that the occupant's ears are closer to the air cooler sound sources, making noise more apparent.
The fabric enclosure may be made in several sections sewn permanently together. One section 4 made of insect screen material forms the top of the enclosure. Four overlapping hanging sections made from insect screen material at the top (2) and impervious fabric at the bottom part (3) are sewn to the top section in such a way that they overlap horizontally by at least 1000 mm at the top, preferably more. Each piece forms part of the end of the enclosure (either the foot end or the head end) and part of the sides, thereby providing access openings in the ends and the sides. Additional material may need to be gathered at the corners and particularly at the foot end of the bed to allow enough fabric to enclose the air conditioner unit.
Fabric hangs over the sides and ends of the bed to form a continuous air and insect barrier, yet still providing convenient side openings for people to enter or leave the enclosed space.
The overlapping fabric at the openings improves thermal insulation between the enclosure and the outside room air.
Fabric ties sewn to the seam joining the top piece and side pieces enables the fabric enclosure to be attached (5) to supporting light weight rods (6) made from metal, wood or bamboo, for example. The rods are suspended from the ceiling (7) such that they are small distance inwards from a position directly above the edges of the bed. By this means the fabric hangs against the sides and ends of the bed forming an effective barrier to prevent air from cascading over the sides and ends of the bed.
A long tube of lightly stuffed fabric about 100 mm in diameter forms a sealing piece between the air conditioner unit and the bed (12). This also helps to anchor the enclosure fabric in place around the sides of the air conditioner unit to prevent leakage (9, 10) of the air between the enclosure and the warmer room air outside.
During the day, the four hanging sections of the enclosure can be drawn apart and tied to allow convenient access to change or air the sheets and make the bed. The air conditioning unit, being mounted on castors, can be moved near to a work desk where the user can be cooled during the day time.
Since the power consumed by the air conditioner is very low, it is suitable to be powered by solar cells of modest size and cost, particularly if coupled to battery storage for night time operation.
Measurements have revealed that a small air conditioner running with an input power of 270 Watts and cooling the enclosure described provides a temperature reduction of about 5° when the room temperature is 35° and humidity is about 50%. The effect of air movement in the enclosure adds an apparent temperature reduction of 2° enabling the unit to meet the comfort requirements established by research. This is achieved by using a cool outlet air vent that supplies cool air to the enclosed space through an air straightener, reducing turbulence in the outlet air stream. This enables the air conditioner to maintain an air flow velocity across the bed that is around 2 metres per second near the outlet air vent, and about 0.4 metres per second at the head end of the bed, sufficient to achieve the apparent 2° cooling.
In an alternative arrangement illustrated in
Remotely controlled vanes V provide a means of adjusting the direction of the cool air jet.
The arrangement of the return air intake to the air cooler needs careful consideration. The cross section area of the intake and the air flow rate together determine the average velocity of air entering the intake. The maximum entry velocity near the middle of the intake will be slightly higher because the air velocity at the edges will be lower than the average velocity.
The depth of cool air with higher density in the enclosure provides a relative pressure difference to accelerate the air to the intake velocity, by Bernoulli's principle. If the intake air velocity is too high, this pressure will be insufficient. When this happens, warm air above the cool air layer will be sucked into the intake along with a proportion of cool air, in the same way that air can be entrained with the water stream draining from a bath when it is not quite empty. This increases the average temperature of the intake air, reducing the cooling efficiency of the air cooler.
The fabric area must be large enough to keep the inflow velocity to about 0.1 m/sec (approximately 0.4 square metres for a flow of 40 litres per second). This is essential to prevent the warm air layer above the cool air from being drawn into the air intake, as explained above.
The air conditioner 1 could alternatively be replaced with an improved air conditioner unit 100 shown in
CN 203586424U, in essence, describes an air conditioner unit 100 that has particular means of evaporating water that is condensed at the cold evaporator, the heat absorbing component of the air-conditioner. The water is evaporated by spraying it in the form of small drops over the hot heat emitting condenser heat exchanger coils. A copy of this patent is attached.
Alternatively, the air conditioner 1 could be replaced with the air conditioner unit 200 shown in
In the improved air conditioner unit 200, both the cold air and hot air to emerge from respective outlets 202, 204 in the top 206 of the unit 200 at lower velocity when compared with the unit 100. The cool air outlet 202 includes a curved air deflector 208 at the top 206 of the unit 200. The deflector 208 serves as:
Experimental testing evidenced that it is important to direct the hot air from the heat emitting side 212 of the air-conditioner unit 200 in an upward direction “DU” so that people in the room with the bed 12 are not as aware of the heat coming out of the air-conditioner 200 as they otherwise might have been. This is in contrast to the air conditioner 1, where the hot air emerged at floor level 11 in a horizontal direction. The hot air outlet 204 includes a deflector 211 positioned to direct hot air vertically away from the outlet 204. The deflector 211 also deflects hot air away from the cool air outlet 202 and there by inhibits heating of the cooled air coming out of the unit 200.
Although the heat from the duct of the unit 1 did not result in any perceptible change in room temperature, the psychological effect on people in the room experiencing this flow of hot air created the sensation that the room was getting hotter. The reason why this heat does not cause the room temperature to be increased is that almost the same amount of heat is being absorbed by the cold side of the air-conditioner at the same time.
The air conditioner unit 1 included an air projector nozzle 90 coupled with an air straightener. However, the nozzle 90 was linked this with the use of the evaporator heat exchanger as the airflow straightener in the manner shown in
Whereas in the air conditioner unit 200, as shown in
As particularly shown in
Air from the room is drawn through the room air inlet 209 at the back of the air-conditioner 200 into the condenser 254 by the fan 252. Air from the fan leaves through the hot air outlet 204 near the top and back end of the air-conditioner 200.
The heat absorbing side 222 of the air conditioner 200 includes:
A motor 250 drives the evaporator fan 262 and the condenser fan 254. These fans can be driven by separate motors if separate speed control is desired.
Air flow through the unit 200 is described below in further detail with reference to the enclosure 306 of the air conditioning systems 300 and 500.
Advantageously, the air conditioner unit 200 is self-contained and the hot air from the condenser 220 is discharged into the room, outside the enclosed sleeping space. It is possible to do this because the electric power used to operate the heat pump function of the air cooler 200 is sufficiently low that discharging this amount of heat does not significantly affect the room temperature. The net difference between the heat absorbed in the cold side 222 of the air-conditioner 200 and the heat emitted at the hot side 212 of the air-conditioner 200 is exactly equivalent to the electric power used operate the heat pump function, this being determined by the laws of thermodynamics and energy conservation. This heat, when discharged into the room, causes an imperceptible temperature rise in the room.
However, from a psychological point of view, it is important to minimise any accidental contact between people using the room and the hot air emerging from the heat emitting side 212 of the air conditioner 200. Therefore, this hot air is discharged in a stream directed substantially vertically upwards from the air cooler 200 by the outlet 204 so that it is not apparent even to people walking past the air conditioner unit 200 at the end or side of the bed.
The deflector 211 functions as a cover for the hot air outlet 204 when arranged in the closed condition of use shown in
The same deflector 211 protects the hot air opening 204 to inhibit dust from entering when the air conditioner 200 is not in use. Opening the hot air deflector 211 also exposes warning indicator lights that enable a user to diagnose a failure of the air-conditioner to operate because of one or more of the following reasons:
These conditions are detected by appropriate sensors and an electronic circuit in the air-conditioner 200 ensures that the air conditioner will not operate under these conditions and that the appropriate warning indicator light is illuminated
In order to minimise the inconvenience of having to empty the water container at intervals, a device on the heat emitting side 212 of the air-conditioner 200 causes small drops of condensed water to be sprayed into the air so that it is evaporated by the heat and passes out as water vapour into the room. The small increase in humidity outside the enclosed sleeping space, like the increase in temperature, is imperceptible to the people using the room. This process is described in CN 203586424U, the contents of which is incorporated herein by way of reference.
With reference to
The temperature sensor 454 mounted on the evaporator 454 senses when ice is likely to form, potentially damaging the evaporator, and operates the switch 456. A further temperature sensor 460 mounted on the discharge tube of the compressor 458 senses when the compressed gas temperature exceeds an upper permissible limit, potentially damaging the compressor, and operates the switch 460.
A float in the water retaining tank 462 operates the switch 464 when the tank is full.
A moving part 470 of the hot air cover 211 operates the switch 472 when the hot air cover 211 is in the fully open position.
A moving part 466 of the cold air deflector 208 operates the switch 468 when the cold air deflector 208 is in the fully open position.
The processor 452 monitors the signals from the switches 456, 460, 464, 472 and 468.
When the signals from switches 472 and 468 indicate that both the hot air cover and the cold air deflector are in the fully open position, the processor supplies power to the fan motor 480.
When the signals from switches 472 and 468 indicate that both the hot air cover and the cold air deflector are in the fully open position, and the signal from switch 456 indicates that the evaporator temperature is above the freezing condition, and the signal from switch 460 indicates that the compressor discharge temperature is less than the permissible upper limit, and the switch 464 indicates that the water tank is not full, then the processor supplies power to the compressor 482. The processor also ensures that the compressor is not restarted within a certain minimum time to prevent the possibility that the compressor will be started while there is excessive residual gas pressure in the refrigeration circuit. The minimum time is typically between one minute and three minutes, depending on the design of the compressor and the refrigeration circuit. It will be appreciated that, depending on the design of the compressor motor, it is possible for the processor to operate the compressor at different speeds in order to regulate the cooling power of the refrigeration circuit. It is also possible for the processor, again depending on the design of the compressor motor, to provide a gradual increase in electric power to the compressor in order to avoid the requirement for excessive electrical current when the compressor is started. This is known as a “soft start” capability. It is also possible for the processor to adjust the electric power supplied to the fan motor to adjust the speed of the fans to suit the operating condition of the air-conditioner 200.
The processor provides power to the indicator lights 476 to indicate particular operating conditions to the user such as when the evaporator temperature is below the freezing condition, when the compressor discharge temperature is above the permissible upper limit, when the water tank is full, when the electric power is available to the processor, and when the hot air cover 211 and the cold air deflector 208 are not fully open. The processor can provide a flashing on and off signal to one or more of the indicator lights to draw the attention of a user to an operating fault condition.
The earth wire from the power connection 490 is also connected to the metal casing of the compressor and other metal parts of the air conditioner 200.
The air conditioner unit includes recessed handles 224a, 224b inset into opposite side panels 226a, 226b. The handles 224a, 224b are shaped for engagement with left and right hands of a person so that the unit 200 can be picked up and carried around. The Unit 200 also includes a power outlet 228 for coupling the electric components of the unit 200 with a power cord (not shown).
The air conditioner system 300 shown in
As particularly shown in
The tent 308 also includes a fabric tent adapter 318 which acts as a conduit joining the air conditioner unit 1,100, 200 with the internal space of the tent 308. The adaptor 318 includes a tent connecting end section 320 coupled to a triangular panel 310 and an air conditioner connecting end section 322 coupled to the air conditioner unit 1, 100, 200. The opening at the air conditioner connecting end section 322 is smaller than the opening at the tent connecting end section 320 so that the adaptor 318 trumpets out from the air conditioner unit 1, 100, 200. This has the effect of slowing the speed of the return air entering the adapter conduit at the tent connecting end section 320 before it enters the air conditioner return air inlet 210.
The air conditioner system 500 shown in
The tent 308 includes four generally rectangular panels 310 coupled to respective sides of a generally rectangular base section 312. Side sections 314 of adjacent panels 310 are coupled together to create a dome like structure 317. The tent 308 also includes an entry aperture (not shown) through which a person can gain entry into, or exit from, the tent 308. Many different forms of above described tent structure are known in the art and can be interchanged with the basic structure of the ten 308.
The tent 308 also includes a fabric tent adapter 318 which acts as a conduit joining the air conditioner unit 1,100, 200 with the internal space of the tent 308. The adaptor 318 includes a tent connecting end section 320 coupled to a triangular panel 310 and an air conditioner connecting end section 322 coupled to the air conditioner unit 1, 100, 200. The opening at the air conditioner connecting end section 322 is smaller than the opening at the tent connecting end section 320 so that the adaptor 318 trumpets out from the air conditioner unit 1, 100, 200. This has the effect of slowing the speed of the return air entering the adapter conduit at the tent connecting end 320 before it enters the air conditioner return air inlet 210.
The adapter 318 is substantially comprised of impervious fabric and forms the return air intake and also encloses an air projector nozzle 208 of the air conditioner unit 200. The adapter 318 also allows for the enclosure to be used on mattresses with different heights above a floor level, even though the air cooler is supported by the floor.
The adapter 318 includes an impervious divider (not shown) providing a separation between air emerging from the cold air outlet 202 and air returning to the return air intake 210 that allows air from the tent to return to the air cooler to be re-cooled. The divider piece is made of fabric and supported at either side at the tent end, and by the cold air outlet of the air cooler at the other end. The divider helps to reduce any tendency of air emerging from the cold air outlet 202 to return immediately to the return air intake 210 before circulating in the enclosure 318.
The adapter 318 is either manufactured as an extension of the enclosure, or is detachable.
The adapter 318 can be made from one or two layers of impervious fabric with an insulating layer, typically made from flexible foam material, in order to reduce the possibility of condensation in humid weather conditions
The enclosure 308 preferably includes insect repellent materials incorporated into the fabric for further inhibiting ingress of insects.
The table below sets out some dimensions for the tent 308. However, these dimensions can vary to suit the needs of any particular application.
With reference to
The return air intake 210 has a sufficient intake area and length which maintains an air intake velocity sufficiently low to inhibit warm air above the conditioned air entering the air intake. For the air conditioner 1, included an area of pervious material serving as an air filter which maintains an air intake velocity sufficiently low to inhibit warm air above the conditioned air entering the air intake. By shaping the air intake as a duct 318 with a large enough intake area, and sufficient length, the area of the duct, decreasing towards the air cooler inlet, which has a relatively much higher intake velocity, inhibits the tendency of warm air above the cool air layer to enter the air intake. As such, there was no need for the pervious air filter.
The localised cooling device 1000 shown in
The cooling device also includes:
The device 1000 shown in
The pathway followed by air as it passes through the cold side 1090 of the air conditioner 1200 is described below in further detail. A person skilled in the art will readily appreciate that the warm air pathway on the warm side 1050 of the air-conditioner is similar in principle.
Air enters the return air inlet 1241 and passes through the return air inlet filter 1240 just before passing through the spaces between the fins of the evaporator 1210. Air leaving the evaporator enters a plenum space 1250 before being drawn into the inlet of the evaporator centrifugal fan impeller 1260 driven by an electric motor 1220. A plenum space 1250 is provided to ensure that air flows with a relatively even velocity across the full area of the evaporator heat exchanger 1210, maximising the heat exchanger efficiency. Air leaving the centrifugal fan impeller 1260 enters a volute 1270 surrounding the impeller and passes from the volute 1270 substantially vertically upwards through the cold air outlet 1300. A curved cold air deflector nozzle 1310 changes the direction of the air to a substantially horizontal direction towards the location of the person using the air-conditioner.
Air from the room is also drawn through the room air filter 1231 adjacent to the condenser 1230, passing through the passages between the condenser fins through a plenum 1232 to an inlet of the condenser centrifugal fan impeller 1370 mounted on the same motor shaft as the evaporator centrifugal fan impeller 1260 driven by the motor 1220. Air leaving the centrifugal fan impeller 1370 enters a volute 1371 and passes out in a substantially vertical direction through the warm air outlet 1380. Air is also drawn through the gap 1390 between the evaporator fan casing and the condenser fan casing in order to pass through the electric motor 1220 to the inlet of the centrifugal fan impeller 1370 to provide cooling for the motor 1220.
A particular advantage of the arrangement in which both the evaporator fan impeller 1260 and the condenser fan impeller 1370 are attached to the same shaft passing through the motor 1220 is that only one motor is required to drive both fans. This reduces the cost and provides a relatively compact physical arrangement of the components.
In order to achieve such a precisely localised cooling effect from a reasonable distance, a jet of conditioned air should leave curved cold air deflector nozzle 1310 in such a way that the cooling effect extends some distance from the origin of the jet, typically at least 1.5 to 2 metres away. It is also desirable that the direction of the nozzle 1310 be adjustable so that the direction of the air jet can be directed at the required cooling location where the person is located.
In order to achieve this, the air jet leaving the curved cold air deflector nozzle 1310 must have as little turbulence as possible: any turbulence in the jet is likely to promote mixing with the surrounding air, reducing the air velocity and reducing the cooling sensation at the location of the person.
The curved cold air deflector has at least one side piece for reducing spillage of air from an at least one side of the deflector. The deflector can be called a curved air projector. Without side pieces on the curved air projector 1310, the pressure difference caused by the acceleration of the air flow towards the centre of curvature causes the airflow near each side of the deflector to “spill” over each side of the curved air projector 1420, reducing the quantity of the air available at the end of the projector to flow in the direction of the desired air jet 1430. This spill effect may cause a considerable reduction of apparent cooling at a distance from the end of the curved air projector.
As particularly shown in
The advantage of a one-sided curved air projector with side pieces is that it can be rotated to a closed position where it acts as a cover for the top and front of the air-conditioner when the air-conditioner is not in use. This prevents dust from contaminating the air inlet and air outlet when the air-conditioner is not in use. Small rotations of the curved air projector can be used to adjust the direction of the coherent jet according to the preference of the user.
A preferable alternative is to provide a compact air flow straightener located between the evaporator fan 1260 and the curved cold air deflector nozzle 1310 to eliminate undesirable vorticity from the air. A centrifugal fan tends to provide the most compact and convenient air pump for an air conditioner because the fan for the cold side of the air-conditioner can be mounted on the same shaft as the fan for the hot side of the air-conditioner, often with the motor mounted in between the two fans.
It is conventional to use forward sloping blades in a centrifugal fan to ensure that the air leaves the impeller substantially in a tangential direction aligned with the volute space surrounding the impeller. However, in this application, a small personal localised air conditioner, the air velocity at the cold air outlet nozzle should be about 3 metres per second to achieve a satisfactory jet of cold air which mixes with the surrounding air as little as possible, while still providing sufficient cooling effect at a distance of about 1.5-2 metres from the air conditioner. A centrifugal fan with forward sloping blades can cause the air to leave a suitably sized impeller at about 12-18 metres per second. The velocity of the air, therefore, needs to be greatly reduced to achieve the desired exit velocity necessitating a loss of much of the kinetic energy in the air generated by the fan impeller. This also contributes substantial noise from the fan which is undesirable in a small air conditioner. The variation of air velocity across the exit from the volute casing is large, and air can even be sucked into the exit aperture in some locations of the exit aperture.
A centrifugal fan with a backward sloping impeller, on the other hand, causes the air to leave the impeller substantially in a radial direction at much less velocity, typically 3-5 metres per second. Using this arrangement the kinetic energy loss in the flow straightener is much reduced, and also the noise of the fan is substantially less. The distribution of air velocity across the exit from the volute casing is also substantially more uniform.
Therefore it is preferable to use a backward sloping centrifugal fan impeller in this application. However, it is still necessary to straighten the air flow and remove vorticity.
In certain embodiments, the evaporator heat exchanger may perform the dual function of a heat exchanger and an airflow straightener.
Many different airflow straighteners have been described in the prior art. Typically they are comprised of a series of narrow air passages which are sufficiently small and long for the turbulent air entering each passage to become laminar at the exit. Straighteners can be made, for example, from honeycomb structures (e.g. U.S. Pat. No. 4,270,577), or a large number of rectangular or circular tubes arranged in a parallel array (e.g. U.S. Pat. No. 6,047,903A). Such airflow straighteners have commonly been used to provide a very even distribution of air velocity and at the same time eliminate vorticity typically in applications such as instrumented wind tunnels for aerodynamic experimentation. In another arrangement, a filter material is arranged in the form of an elongated folded zigzag so as to present a very large surface area to the incident flow (e.g. U.S. Pat. No. 7,905,153 B2). This also provides a high degree of flow straightening and turbulence removal. In another arrangement a large plate with an array of small holes provides similar function (e.g. U.S. Pat. No. 3,840,051).
All these airflow straighteners present manufacturing challenges and take a relatively large amount of space. They are also relatively costly parts which is undesirable for a mass-manufactured personal localised air conditioner.
An alternative air flow straightening arrangement provides a satisfactory degree of flow straightening and turbulence removal in a much more compact form. In this arrangement the air leaving the centrifugal fan impeller enters a curved volute passage surrounding the outside of the fan and passes through this passage to the airflow straightener and then to the cold air outlet nozzle.
The flow straightener consists of a parallel array of rectangular passages approximately 10 mm×10 mm in cross section and about 40 mm long which can be made in a single plastic injection moulded part. The passages are too large and too short to remove most of the vorticity but they are sufficient to change the direction of the air flow from the centrifugal fan 1500 to a vertical direction. Smaller passages would be difficult to manufacture using low cost injection moulding methods. The foam that eliminates the vorticity in the air flow is desirably cut from open cell plastic foam material 10-15 mm thick with a cell size of typically 3 mm -6 mm, a material which is commonly used for aquarium filters and available at very low cost.
Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention
The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in Australia
In this specification and the claims that follow, unless stated otherwise, the word “comprise” and its variations, such as “comprises” and “comprising”, imply the inclusion of a stated integer, step, or group of integers or steps, but not the exclusion of any other integer or step or group of integers or steps.
References in this specification to any prior publication, information derived from any said prior publication, or any known matter are not and should not be taken as an acknowledgement, admission or suggestion that said prior publication, or any information derived from this prior publication or known matter forms part of the common general knowledge in the field of endeavour to which the specification relates.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014903758 | Sep 2014 | AU | national |
| 2015901307 | Apr 2015 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2015/050514 | 9/1/2015 | WO | 00 |
