An invention for a canopy using the Coanda effect for air conditioning with thermoelectric modules.

Abstract

An air conditioning device comprises a heat pump device 3 to cool or heat air blown by a fan 5 over a surface of the device, and using the Coanda effect entrains surrounding air 22 adjacent the surfac

Description

The world faces such a challenge of extreme heat that it is often referred to in the media as global boiling. In Europe, a heatwave in 2022 is estimated to have caused more than 60,000 deaths and significantly more other health related incidents. Subsequently, the World Meteorological Service has said that 2023 was the joint warmest or second warmest year on record with a record number of days for extreme heat stress. While mortality figures for 2023 are not yet available, heat related deaths are expected to be at the same or higher levels that 2022. Experts predict that global heat deaths could increase by nearly 400% by the middle of the century (Reuters Nov 14, 2023). In the United States, 2023 saw an extreme heatwave affected many states in southern USA including Texas, New Mexico, Arizona, Nevada and California. Temperatures in Phoenix reached 48 degrees C and saw 54 days of temperatures over 43 degrees C (110 degrees F). It also set a new record of 31 consecutive days (all of July) of temperatures exceeding 43 degrees C compared to the previous record of just 18 consecutive days. (Source: PBS). Figures from the US department of Health and Human Services show show that heat-related deaths have been increasing in the U.S., with approximately 1,602 occurring in 2021,1,722 in 2022, and 2,302 in 2O23.The economic costs of heatwaves are immense with the USA alone estimated to lose approximately $100 billion a year from heat induced loss of productivity (reports quoted by Joint Economic Committee of US Senate). In 2024 alone, at the time of filing the following heat related headlines may be noted: i. In India temperatures have reached or exceeded 50 degrees C with over 40,000 heatstroke cases and 100 lives lost - Economic Times June 20th II. 1301 people were reported dead during the Haj in Saudi Arabia due to a heatwave that reached 51 degrees C - The Independent, Online, June 24th ill. Greek authorities were forced to shut down the Acropolis due to temperatures exceeding 40 degrees C - Euronews with AP, Online, 21st June iv. Though summer is just 3 weeks old, over 50 cities in California and Nevada have broken all time heat records with 30 fatalities already - USA Today, Online,13th July v. 146 million Americans are under extreme heat warnings in California, Nevada, Arizona, Oregon and Idaho. Las Vegas reached record temperatures of 120 degrees F (53.3 C) -The Guardian, Online, 8th July vi. Global temperatures have broken records for 12 consecutive months and May has been the warmest May ever recorded Besides the direct health-related casualties of extreme heat, extreme heat is simply unbearable, equivalent to torture, for most people. As temperatures continue to increase, if nothing is done to defend human populations from its effects, we risk catastrophe and unimaginable human suffering. Up to now, as global temperatures have risen, the world has relied on conventional vapour compression air-conditioning technology as its principal source of heat defence. However, such conventional air-conditioning is not practical for many cases such as i) outdoor work and pastimes ii) activities that require mobility and iii) is not affordable for billions of people across the world, even in developed countries. Conventional air-conditioning also has a high threshold cost and can be wasteful where entire buildings need to be air-conditioned just to cool a relatively small number of people. A final reason against it, is its use of refrigerants which are themselves environmentally damaging and polluting. Conventionally delivered air-conditioning also places an immense pressure on utility grids and in many countries. The capacity, extent and reach of the power grid simply cannot support the level of conventional air-conditioning required to protect their populations. One alternative is to use thermoelectric modules (TEMs) which are often referred to as Peltier modules. We refer to both as TEMs for short. TEMs have the benefit of being of very small size, typically just the size of 4-5 credit cards stacked together and have low absolute cost. A single such TEM may produce as much as 100 watts of cooling which is sufficient for a sedentary human. A few such TEMs could produce up to 300 Watts of cooling which is enough for an active human. As small modular units, such TEM based air-conditioning systems can quite easily be powered by solar power, a commodity that is abundantly available when heat-waves are present. TEM’s challenge however has been that they require a relatively bulky heat transfer apparatus to be attached such as forced convection or conduction heat exchangers / heat sinks which can make the overall solution large and unwieldy. Any approach that can improve their efficiency, effectiveness and ease of use would be highly beneficial to society. In particular, small or large canopies or fans which can provide cooling to individuals or joined together to form heat refuges for larger groups of people would be of great benefit to humanity. One alternative approach which is not shown in the prior art is to use the Coanda effect to achieve the desired control and management of a TEM conditioned air mass. The Coanda effect is well established in fluid dynamics. It is defined by Merrick Webster dictionary as “the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to entrain fluid from the surroundings so that a region of lower pressure develops and refers to the tendency of a jet flow to attach itself to an appropriately curved surface”. This creates an area of low pressure between the surface and the fluid jet and a high pressure zone on the side of the fluid jet furthest away from the surface. As the jet travels across the surface and finally detaches, the low pressure zone has the effect of entraining (or “sucking in” in colloquial terms) air from the low pressure side of the surface to multiply the airflow. In some use cases, air amplification of up to 15x the mass of the original airflow is cited. While this approach has been used previously to create “bladeless” fans, using it for TEMs poses a particular challenge. Whereas a conventional bladeless fan uses just a single airflow of ambient temperature, using it for a TEM requires control of four different air masses, hot, cold, ambient and recirculated, in close proximity to each other. The conventional bladeless fan also does not concern itself directly with recirculation of conditioned air. To use it for a TEM the solution needs to cool air, provide a recirculation system for conditioned air, provide an exhaust system for hot air and introduce fresh air to support respiration. The following prior art has been reviewed: US 3,548,415 from 1970 for an air conditioned helmet but which uses a simple fan mechanism together with a variety of heating or cooling elements such as a TEM. The reference to TEMs is incidental and it does not deal with the requirement of evacuating heat from the hot face of the TEM or provide it with a power source. It does not utilise the Coanda effect nor does it provide for recirculation of air. It’s designed for use by one person only and does not scale up to serve larger areas or groups of people. US 8,308,455 by Gammack et al of 2012 for a bladeless fan deals only with a fan mechanism for ambient air. It uses the Coanda effect to draw in ambient air from a posterior air mass behind an annular Coanda mouth assembly and accelerate it forwards towards an anterior target area. It does not address any additional heating or cooling mechanism or how to manage separate flows of hot, cold, ambient and recirculated air such as required when using a TEM or active cooling or heating mechanism. It also only recirculates air incidentally, if at all, by virtue of the fan and air masses both being in an enclosed space does not recirculate conditioned air in an outdoor space. EP 2778 552 A1 by Yasutomi et al of 2014 and prior art referred to concerning an air-conditioning indoor unit that can vary airflow across a Coanda surface. It refers only to an indoor solution and does not deal with the segregation of the required 4 separate air masses (cold, hot, ambient and recirculated) as is required in an outdoor solution with a TEM. In the indoor case addressed by Yasutomi ET al, the target state is that there is only a single air mass in the room of the target temperature although there may be temperature gradients across the air mass. The concept of using the Coanda flow to segment air masses does not apply and rather the focus is on using the Coanda effect to “throw” the conditioned air further across the room than would otherwise be the case. It does not focus on using the Coanda effect to cling to the target area being cooled or the target persons being cooled nor use it to introduce fresh air. Also, it uses a transversely-mounted longitudinal vane to “throw” the air rather than a hemispherical Coanda surface to constrain teh air in a tightly defined target zone. It also does not address the issue of drawing the recirculating air back through the eye of the Coanda air flow. Rather, as a conventional room air conditioner, the recirculated air is drawn back through a manifold in a distinctly separate plane. To overcome these problems and challenges, the present invention proposes a canopy with curved surfaces and air jets designed to produce the Coanda effect which incorporates a heat pump device such as a TEM. When used for cooling, the cool side of the TEM is directed towards the enclosed inner side of the canopy while the hot side of the TEM vents to the exposed outer side of the canopy. When used for cooling, jets of air are forced through the cool side of the TEM and then directed to the inside wall of the canopy through a diffusion structure. The interior walls of the canopy and diffuser are designed as Coanda surfaces which direct the air jets downwards into the area to be cooled. As the cold face and cold air jets are significantly cooler than the ambient air, the cold air descends and adds to the initial momentum provided by the Coanda effect. The Coanda effect also entrains air from immediately beneath the canopy and causes a recirculating current of air to be set up inside the enclosure which keeps the air inside the enclosure at the desired temperature. The hot side of the TEM is at a significantly higher temperature than the ambient air. It is fitted with a conventional air-cooled heatsink and fan which vents to the atmosphere above the canopy. As hot air rises, the dissipated heat rises through the ambient air and away from the canopy. In the preferred embodiment, a chimney structure may also be provided so that the dissipated hot air does not leak along the edges of the canopy. TEMs commonly produce a temperature differential of 50 degrees centigrade between the hot and cold face after allowing for operational inefficiencies. Assuming even an extreme ambient temperature of 50 degrees centigrade, maintaining the hot-side temperature at 20 degrees centigrade above ambient i.e., 70 degrees centigrade, would deliver a comfortable cool side temperature of 20 degrees centigrade. In colder seasons, the apparatus can be used for heating by simply reversing the polarity of the current applied to the TEM which would put the hot-face of the module on the inside of the canopy and the cold-face on the outside. The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a front elevation of an embodiment of the invention Figure 2 shows a cross-section along the dotted line XX in Figure 1 when viewed along A in the direction of the shown arrow Figure 3 provides a front elevation of the diffuser mechanism Figure 4 shows the embodiment with an optional curtain or barrier of fabric, plastic or other material to reduce entrainment of outside ambient air Figure 5 shows an alternative embodiment without a central pillar structure Figure 6 shows an embodiment where the canopy is supported by a drone instead of a pillar to allow it to be transported for events or emergency applications. Figure 7 shows another embodiment where the canopy is miniaturised to a wearable hat Figure 8A and 8B show an embodiment that allows both the hot air and cold air impellers around a TEM to be driven from a single pump so as to reduce weight, size, energy consumption and cost. Figure 9 shows a portable embodiment that utilises the single pump arrangement The exemplar implementations are now described in more detail. Figure 1 shows a canopy structure 1 and diffuser structure 7. They are supported by a hollow pillar 9 with apertures 10 to allow airflow into the pillar. There is an opening at the apex of canopy 1 where a TEM 3 is located. The inside surfaces of the canopy 1 and diffuser 7 are designed to produce an airflow with the Coanda effect. In this implementation a circular or umbrella structure is used but any other shape may be used that also allows the Coanda effect. For example a rectangular structure may also be used for say a bus shelter. The cold-face of the TEM 3 is attached to a heatsink 6 with fins that are aerodynamically designed so that forced air from the impeller pump 5 is channeled into a diffuser structure 7. While an impeller pump is preferred in this implementation, it may also be replaced by other fan or blower structure. The Coanda effect begins to take effect in the diffuser due to the two narrowing curved surfaces provided by the diffuser 7 and the canopy body 1 .This results in a characteristic jet flow called an air knife 20 being delivered at the annular diffuser mouth aperture at 14. As the air flow 20 exits the diffuser mouth at 14, the Coanda effect causes it to cling to the inner Coanda lip 15 and to the Coanda surface 2 and proceed in the direction shown by the dotted arrows 20. The Coanda effect at the inner lip 15 causes it to entrain air from airflow 21. A further outer Coanda lip 26 is also shown which can be angled in the final design to achieve the optimal characteristics for airflow 20 based on the overall size, shape and performance requirements of the canopy structure. Airflow 20 continues to descend past the outer lip 20 due to its momentum as well as because it is colder than the surrounding air and hence more dense. Due to the Coanda effect it also draws in and entrains a further airflow 22 which acts as a barrier flow between the cold jet and the remaining ambient air in the exterior. Air knife 20 and airflows 21 and 22 mix together near the base 11 of the canopy structure and are drawn up as airflow 23 by the impeller pump 5 through the apertures 10 in the hollow pillar 9. The number of apertures are highest at the bottom of the pillar and reduce as they reach the vicinity of the fan so that most of airflow 22 is from the lower section of the structure. The combination of the impeller pump, diffusers and Coanda effect set up a recirculating cool air-system beneath the canopy. Some external air 21 is also entrained by the Coanda effect. This provides a source for fresh air 21 and also creates a barrier flow so that the cold air flow in 20 is kept contained within the canopy structure to the maximum extent. The hot-face of the TEM is attached to an air cooled heatsink 13 with forced convection towards the atmosphere by a fan 4. As the expelled hot air 24 is at a significantly higher temperature than ambient air, it rises and diffuses away. A chimney element 8 may also be added to minimise the likelihood of the expelled hot air 24 mixing with airflow 22. In this embodiment, the canopy is powered by solar cells 12 affixed to the canopy but it may also be powered by any other external power source or a rechargeable battery pack. Figure 2 shows a cross section along the plane XX when viewed from the base 11 through the pillar 9 and towards the impeller pump 5. At the centre of the cross section can be seen the impeller pump 5 which forces airflow 23 onto radial fins 6 of a heat sink which are attached to the TEM 3. The fins are preferably arranged in a radial arrangement but may be in any other arrangement that aids convection and heat transfer. The fins are cooled by the TEM and absorb heat from the airflow that is forced onto them by impeller pump 5 hence cooling the air to the target temperature. The air is then channelled along the fins into the space behind the diffuser structure 7 as cooled airflow 20. Cooled airflow 20 then exits the diffuser structure 7 at the diffuser mouth 14 and entrains airflow 21 due to the effect caused by the inner Coanda lip 15. Airflow 20 then clings to the Coanda surface 2 of the canopy body 1 before interacting further with the outer Coanda lip 26 already shown in Figure 1. The solar cells that power the unit are shown at 12. Figure 3 shows a front view that provides further detail of the diffuser structure 7 which is attached to the canopy superstructure by flanges 25. The flanges also serve as air channel guides to direct airflows 20 within the diffuser space toward the diffuser mouth at 14 and the inner Coanda lip 15. Figure 4 shows an alternative embodiment where a fabric or other curtain or enclosure has been added to separate the cooled air in the canopy from the ambient air. Infrared or other sensors 35 may also be added to detect the presence of people. Based on the heat signature detected by the sensors of the present human bodies, the amount of power supplied to the system may be regulated and controlled. Figure 5 shows an alternative embodiment without a central pillar structure 9. Figure 6 shows an alternative embodiment without a central pillar but with a number of propellers 60 attached to allow it to hover in place or be directed to travel under its own motive power. Details on the power and control of the propellers and the overall system and mechanism to achieve levitation is not shown as they are well understood in the drone or unmanned aerial vehicle arts. Figure 7 shows an embodiment in a hat-like structure that can be worn by a person 70. 71 shows a TEM with the cold side connected to a heat sink 72 and hot side connected to a heat sink 73. An impeller pump 74 draws in a air mixture 80 of ambient and recirculated air through the cold inlet chamber 76 which is cooled by the heat sink 72. It is expelled as a cold air jet 81 into the cold outlet chamber 77. The air jet 81 proceeds out of the chamber 77 and interacts with the Coanda surface at 78 which draws it in and towards the body of the person 70. The Coanda effect also results in airflow 84 being entrained into airflow 81. As the conditioned air descends and warms, it recirculates as the airflow 82 which rises due to a combination of its lower density, the entrainment current 84 and the suction caused by the impeller pump 74 and air flow 80. Meanwhile, the hot side impeller pump 79 draws in ambient air 85 which absorbs heat from the heat sink 73 and is expelled as airflow 86. Due to its momentum as well as higher temperature and lower density than the ambient air, it rises and diffuses upwards and away from the conditioned area. Taken altogether, this creates a comfortable cool zone beneath the hat arrangement for the comfort and health of the person 20. In a further embodiment, small perforations may also be incorporated into the bottom surface 88 of the cold chamber 77 to allow air conditioning of the person’s enclosed head area. The device may be powered by a rechargeable battery pack, solar cells or mains power which are not shown. They may be attached to the hat or carried on the body, other apparel or carry-bag to reduce the weight on the head and neck of person 70. To further reduce weight, the TEM, heatsinks, motor and impeller assemblies may also be combined as in figures 8A and 8B so that they may be removed from the head area of the person 70 and simply feed a set of air-tubes or valves into the hat arrangement. Figure 8A shows a plan view of a TEM with a dual impeller and single pump assembly which may be used to serve the canopy, hat and other implementations. It particularly provides a method of managing 4 different airflows of cold, hot, ambient and recirculated air though a single motor assembly that powers two impellers. 8A shows a plan view of the 4-way air chamber complex where 101 is the intake duct of recirculated air, 102 is the outlet duct for the cold-air air jet from the cold-side of the TEM, 103 is the inlet chamber for ambient air to cool the the hot-side heatsink and 104 is the exhaust duct for hot-air expelled from the hot-side of the TEM. The TEM, heatsinks, impellers and drive shaft reside inside a void 105. The ducts 101 102 103 104 are wrapped around this void. The inlet ducts 101 and 103 enter the impellers through their inlet ports 106. For simplicity only 2 sets of the 4 ducts are shown. The 8B shows a vertical cross section along the plane BB in Figure 8A. It consists of TEM 150 with a hot-side heatsink 170 and a cold-side heat-sink 160. A motor 110 drives a cold side impeller 120 and a hot side impeller 130 through a driveshaft 111. Recirculated air is sucked in via the duct 101 which reaches down below the TEM 150 and blows onto the cold-side heat sink 160 before being sucked into the central inlet port 121 of the coldside impeller 120. It is then expelled through the impeller blades into the duct 102. From the top of duct 102, a tube or other assembly carries it to the cold-side air vents of the cooling apparatus such as a hat, canopy, vest or other form factor. This removes the need for a TEM, heat-sink and impeller pump assembly 74 in , say, the hat structure and hence reducing the head-worn weight. Similarly ambient air is sucked in via duct 103 which reaches down to the hot-side heatsink 170 beneath the hot side impeller 130. The ambient air is then forced through the fins on the hot-side heat-sink 170 and then enters the hot-side impeller 130 through its central inlet port 131. It is then forced out by the blades of impeller 130 into the hot air exhaust duct 104. From the top of duct 104, a tube or other assembly (not shown) vents the hot air into the atmosphere at a safe or convenient location. The arrangement of the second set of ducts on the reverse side of figure 8B simply mirrors that already described here. Other implementations may have more than 2 sets of ducts in order to have a more evenly distributed set of fluid flows. Figure 9 shows another implementation as a portable device cooling a person located in direction X. The device’s handle incorporates the assembly 250 already shown in Figure 8A and 8B consisting of a TEM, cold side heatsink and impeller, hot-side heatsink and impellers, an associated 4-way air chamber complex and a motor. It also includes other parts as described below. For simplicity, the schematic diagram of the TEM, heatsinks, impeller and motor assembly and its ducts are not shown again in Figure 9 as they have been described in detail in 8A and 8B. A recirculating air inlet 210 draws in air from the direction of the person being cooled and sends it via tube 290 to the impeller and pump assembly 250 already described in Figure 8A and 8B. The cold side impeller then expels a jet of cold-air through tube 291 which emerges through the jet aperture 200. An air jet 202 emerges from the aperture 200 and flows along the convex Coanda surface 201 from where it travels as air jet 202 in the direction of the person being cooled. An ambient air intake 270 delivers ambient air from the posterior of the device into the handle assembly 250 via tube 293. It absorbs heat from the hot-side heatsink and the hot air is exhausted via tube 292 to the hot air vent 280 and thence expelled in direction Y where it dissipates upwards and away from the user and the air conditioned zone which are in the opposite direction X. This represents an advancement on a conventional bladeless and bladed fans which do not provide active cooling nor a way of dissipating the exhaust air from the cooling component.

Claims

1. A canopy with a heat pump device and fans which uses the Coanda effect to create a recirculating body of conditioned air that is cooler or hotter than the ambient air as may be required2. A canopy of claim 1 above where the heat pump device is a TEM3. A canopy of claim 1 above where any of the fans used is an impeller pump4. A canopy of claim 1 above where a body of air that is of an opposite sense of temperature from the recirculating air, when considered in relation to the ambient air, is expelled to the outer side of the canopy structure i.e., if the recirculating air is colder than ambient air and the expelled air is hotter than the ambient air and vice versa.

5. A canopy of claim 1 where the conditioned and exhaust airflows from a heat pump device are kept separate by the canopy structure6. A canopy of claim 1 above incorporating a hollow pillar by which recirculating air may be drawn up towards a cooling device7. A canopy of claim 4 above where the pilar has apertures or other methods of regulating the flow of air8. A canopy of claim 1 where infra-red or other sensors detect the presence of human or animal bodies or the amount of heat they are generating which is then used to regulate the activity of teh canopy9. A canopy of claim 1 with propellers attached instead of a supporting pillar to allow it to hover above a target zone or to be transported to different locations under its own motion.

10. A canopy of claim 1 designed in a shape that may be worn on the head of a person11. A canopy of claim 1 where the TEM, impellers, motors and heatsinks are located remotely but fed into the canopy via tubes or other kinds of fluid transport mechanisms.12 A handheld or portable device that blows a jet of actively cooled air towards a target zone, recirculate air from the target zone after active cooling into the target zone, intake ambient air to cool a TEM and expel such heated air away from the target zone.13 A device of Claim 12 which uses the Coanda effect to influence the direction of any of the air streams.

14. A system of a plurality of impellers that are vertically aligned with a single or plurality of TEMs and a single pump that separately manages concurrent flows of fluids that are hot, cold, recirculated and ambient respectively.

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