2 The Coanda Effect

Anyone who has ever dribbled while trying to pour liquid out of a spout or bottle has experienced the Coanda Effect. As you know, the liquid tends to adhere and run around the curved lip of the spout or bottle.

It was in 1910 that a Romanian-born engineer, Henri Coanda accidentally discovered the phenomenon which was later named after him. He had built a kind of jet aircraft equipped with an air compressor powered by a reciprocating engine. By injecting fuel into the compressed air, he achieved an afterburner which provided thrust. Concerned that the flames from the two jet exhausts might set fire to the plane's plywood fuselage, he installed metal plates to deflect the exhaust flames.

"Coanda took his vehicle out for a test run on a filed at Issy les-Moulineaux, a Paris suburb. As he taxied across the filed, he saw with dismay that the deflecting plate, instead of diverting the exhaust away from the body of the plane, were actually drawing the flames toward it! Preoccupied with this surprising development and with handling the engine throttle, Coanda did not notice until the last moment that he was approaching the Paris city wall at high speed. He jerked back on the control stick, became airborne long enough to clear the wall, then crashed.

As far as is known, this was the first flight of a jet airplane. Reflecting on the incident, however, Coanda was less interested in the takeoff than in the strange phenomenon of the wrong-way bending of the jets by his deflector plates. At the first opportunity he discussed the events with Theodor Von Karmen, the foremost theorist of aerodynamics, who was then working at the University of Gottingen. Von Karmen realized that the phenomenon was a new discovery and named it the Coanda effect."

Coanda's later experiments showed that a sheet of fluid discharged through a slit onto an extended and rounded lip will attach itself to the curved surface and follow its contour. He discovered that a shoulder made of a series of short flat surfaces, each at a specified angle to the one before and each with a certain length would make it possible to bend a jet stream around a 180° arc.

Further he found that the deflected air-stream sucked up air from the surroundings. He found that as the jet flowed around the shoulder, it entrained up to twenty (20) times the amount of air in the original jet. (See Fig.1)

Fig.1: The Coanda Effect is the tendency of a fluid to cling to a surface that is near an orifice from which the fluid emerges. An important part of the effect is the tendency of a small stream of air or fluid (primary stream) to entrain a larger volume (secondary stream) and cause it to be drawn along with the primary stream. The result is an air powered fan.

The flow amplification principal of the Coanda Effect is a feature used to great advantage by Texan in their Pol-O.R. Bear system. (See Fig. 2)

Fig. 2: Pol-O.R. Bear tubing creates hundreds of tiny fans that are directed at the desired angle along a length of specially designed tubing.

Excerpts from "Applications of the Coanda Effect", by Imants Reba; Scientific American, June 1966

Coanda fans are the heart of Texan's Pol-O.R. Bear system. This Coanda tubing can be used in any number of ways where increased air flow or cooling is needed. When worn on the body, they form a unique cooling system

In operation, clean, dry, compressed medical air is expelled through hundreds of tiny pressure drop points along the Pol-O.R. Bear tubing, which acts as a self balancing distribution system. The Coanda Effect causes an air flow amplification, resulting in increased air movement. The result is a small drop in temperature and the evaporation and purging of hot, sweaty vapors from the user's garments. Body cooling is achieved as perspiration evaporates.

A miniature pressure regulating valve supplied with the Pol-O.R. Bear system is used to easily adjust the comfort level to suit individual needs. Lightweight air feed lines, connections and controls allow freedom of movement without dragging or tugging at the user

Point of use regulating valve, balanced distribution and built-in flow control ensure that a minimum of air is needed and that multiple users can be supplied from a single source.

•Keeps Surgeons and Nurses Cool, Dry and Comfortable: Excessive heat drains energy from the body causing impaired judgment, sluggish reflexes and sometimes blurred vision. The Pol-O.R. Bear system and is localized cooling effect helps operating room personnel remain sharp and focused on their task. It also allows for elevated room temperatures for optimal patient comfort.

•Easy to Use: Put on the Pol-O.R. Bear cooling vest beneath your surgical gown and snap in the air supply quick-connect. Adjust the control valve to achieve the comfort level you desire and go to work. Cooling begins immediately.

•Virtually Silent Operation: Unlike noisy vortex coolers or heavy icepack vests, Pol-O.R. Bear uses low pressure air to generate cooling air flow, for quiet operation and for as long as you need it.

•Energy Efficient: Coanda fans multiply air flow rate by as much as 20 times, reducing the amount of input air needed to maximize effectiveness. Pol-O.R. Bear requires only a few feet per minute (CFM) at 10-15 psig of compressed air to operate.

•Lightweight: Texan's unique vest design eliminates bulky garments and heavy icepack vests.. Our custom designed Pol-O.R. Bear feed line and valve are all lightweight. Only ten (10) ounces for a typical vest.

•Increases Users Efficiency: Promotes evaporation and purging of hot, sweaty vapors from the users garments and keeps the wearer cool and dry. This reduces the constant threat of heat stress and enables Surgeons and Nurses to operate at peak performance for extended periods of time.

•Quick Connect/Disconnect: Users can quickly connect or disconnect at any time through the use of convenient, quick coupling connectors.

•No Moving Parts To Fail: The Coanda system is an air operated flow multiplication device that has no moving parts.

•Comfort Level is Easily Adjusted: Individual point of use pressure regulating valve allows the user to adjust their comfort level.

•Safe: Lightweight air feed lines, connections and controls allow freedom of movement around the operating room without dragging or tugging at the user. Also medical personnel can quickly disconnect at any time through use of the convenient quick coupling connectors.

When used in confined space, ONLY air of a breathable quality should be used.

FEATURES:	BENEFITS:
• Coanda enhanced air flow designed around	• Keeps medical personnel cool and comfortable
users blush zones
• Includes air pressure regulator	• Adjusts to individual comfort levels
• Optional manifold available	• Allows both Surgeons and Nurses to stay cool
• Works off existing medical air line	• Cooling begins immediately when connected to
	medical airline
• Virtually silent operation	• Does not distract Surgeons or Nurses from task
• No moving parts	• Low maintenance
• Uses little air pressure to provide effective	• Energy efficient
cooling
• Lightweight	• Unnoticeable and unobtrusive to user
• Quick connects and disconnects	• Vest easily slips on and off
• Provides localized cooling to medical personnel	• Allows higher room temperatures for optimal
	patient comfort
• Cooling vest can be laundered	• Allows for repeat and clean use

EQUIPMENT LIST:	SPECIFICATIONS:
• Pol-O.R. Bear vest; includes vest and supply tether	• Pol-O.R. Bear tubing is a soft silicone extrusion
• Air pressure regulator; require one (1) per vest	• Supply tubing (tether) is PVC
• Medical air line tethers:	• Tubing connectors are nylon
• 15 ft. for wall mounted medical air couplings	• Miniature disconnects are stainless
• 8 ft. for ceiling drop - down medical air couplings	• Pressure regulator has supply pressure gauge
• 5 ft. for under table pedestal mount	• Maximum operating pressure is 50 PSI
• Manifold - to - vest tether; 10 ft.
• Multi-user manifold; 2 user (4 user available)
• Wye fittings; branches medial air line to Pol-O.R. Bear vest and to anesthesiologists station
• Medical air couplings; Texan stocks a complete line of standard medical air couplings including: Ohmeda, Chemtron, Schrader, Puritan and DISS

TEXAN THERMAL SYSTEMS is a pioneer in the use of the Coanda Effect to provide extremely effective cooling, and the originator of the Pol-O.R. Bear system. TEXAN also designs and manufactures garments and related products for use by personnel working in high heat situations. A team of experienced engineers and stringent quality control ensure that all TEXAN products are of the highest quality.