summer project pal|
Active In SP
Joined: Jan 2011
10-01-2011, 06:37 AM
Vortex refrigeration is a highly sophisticated system that contains a vortex tube which due to centrifugal force expels the internal energy of the air while the air at the centre core is made cooler. In this type of system the effectiveness is too low but considering its small size this can’t be ruled off. This is used as personal cooling system in suits that are designed to withstand heat.
Vortex refrigeration report.doc (Size: 388.5 KB / Downloads: 172)
passwordeminar and presentationproject and implimentations
*Refrigeration is the science of the producing and maintaining temperatures below that of the surrounding atmosphere. This means the removing of heat from a substance to be cooled. Heat always passes downhill from a warm body to a cooler one, until both bodies are at the same temperature. Not only perishables today many human work spaces in offices and factory building are air-conditioned and a refrigeration unit is the heart of the system.
• Before the advent of mechanical refrigeration water was kept cool by storing it in semi porous jugs so that the water could seep through and evaporate. The evaporation carried away heat and cooled the water. This system was used by the Egyptian and by Indians in the south west. Natural ice from lakes and rivers was often cut during winter and stored in caves, straw-lined pits, and later in sawdust insulated building to be used as required. The Romans carried pack trains of snow from Alps to Rome for cooling the emperor’s drinks. Though these methods of cooling all make used of natural phenomena, they were used to maintain a lower temperature in a space or product and may properly be called refrigeration.
• In simple refrigeration means the cooling or removal of heat from a system. The equipment employed to maintain system at a low temperature is termed as refrigeration system and the system which is kept at lower temperature is called refrigerated system.
• Refrigeration is generally produced in one on the following three ways
1. By melting of a solid ,
2. By sublimation of a solid and
3. By evaporation of a liquid.
• Most of the commercial refrigeration is produced by the evaporation of a liquid called refrigerant. Mechanical refrigeration depends upon the evaporation of liquid refrigerant and its circuit includes the equipments naming evaporator, compressor, condenser, expansion valve. It is used for preservation of food, manufacture of ice, solid carbon-dioxide and control of air temperature and humidity in the air conditioning system.
Elements of refrigeration systems
All refrigeration system must include at least four basic units as given below
1. A low temperature thermal ‘sink’ to which heat will flow from the space to be cooled.
2. Means of extracting energy from the sink, raising the temperature level of these energy, and delivering it to a heat receiver.
3. A receiver to which heat will be transferred from the high temperature high pressure refrigeration
4. Means of reducing pressure and temperature of the refrigerant as it returns from the receiver to the ‘sink’.
The various refrigeration systems may be enumerated as below;
1. ice refrigeration system
2. air refrigeration system
3. vapour compression refrigeration system
4. vapour absorption refrigeration system
5. special refrigeration systems
a. absorption refrigeration system
b. cascade refrigeration system
c. mixed refrigeration system
d. vortex refrigeration system
e. thermoelectric refrigeration system
f. steam jet refrigeration system
The performance of a refrigeration system is expressed by a term known as the Co-efficient Of Performance (COP), which is defined as the ratio of heat absorbed by the refrigerant while passing through the evaporator to the work input required to compress the refrigerant in the compressor ; in short it is the ratio between heat extracted and work done.
The rating of the refrigeration machine is given by a unit of refrigeration known as standard commercial tonne of refrigeration which is defined as the refrigerating effect produced by the melting of 1 tonne of ice from and at 0 degree celcious in 24 hours. Since the latent heat of fusion of ice is 336 kj/kg, the refrigerating effect of 336*1000kj/kg in 24 hours is rated as One TONNE,
In si units its conversions rounded off to 3.5kj/s(kw) or 210 kj/min.
Vortex created by the passage of an aircraft wing, revealed by colored smoke.
A vortex is a spinning, often turbulent, flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation of the fluid are greatest at the center, and decrease progressively with distance from the center.
1.1 Properties of vortex
Vortices display some special properties:
• The fluid pressure in a vortex is lowest in the center where the speed is greatest, and rises progressively with distance from the center. This is in accordance with Bernoulli's Principle. The core of a vortex in air is sometimes visible because of a plume of water vapour caused by condensation in the low pressure of the core. The spout of a tornado is a classic and frightening example of the visible core of a vortex. A dust devil is also the core of a vortex, made visible by the dust drawn upwards by the turbulent flow of air from ground level into the low pressure core.
• The core of every vortex can be considered to contain a vortex line, and every particle in the vortex can be considered to be circulating around the vortex line. Vortex lines start and end at the boundary of the fluid, but they do not start or end in the fluid. (See Helmholtz's theorems.) Vortices readily deflect and attach themselves to a solid surface. For example, a vortex usually forms ahead of the propeller disk or jet engine of a slow-moving airplane. One end of the vortex line is attached to the propeller disk or jet engine, but when the airplane is taxiing the other end of the vortex line readily attaches itself to the ground rather than end in midair. The vortex can suck water and small stones into the core and then into the propeller disk or jet engine.
• Two or more vortices that are approximately parallel and circulating in the same direction will quickly merge to form a single vortex. The circulation of the merged vortex will equal the sum of the circulations of the constituent vortices. For example, a sheet of small vortices flows from the trailing edge of the wing or propeller of an airplane when the wing is developing lift or the propeller is developing thrust. In less than one wing chord downstream of the trailing edge of the wing these small vortices merge to form a single vortex. If viewed from the tail of the airplane, looking forward in the direction of flight, there is one wingtip vortex trailing from the left-hand wing and circulating clockwise, and another wingtip vortex trailing from the right-hand wing and circulating anti-clockwise. The result is a region of downwash behind the wing, between the pair of wingtip vortices. These two wingtip vortices do not merge because they are circulating in opposite directions.
• Vortices contain a lot of energy in the circular motion of the fluid. In an ideal fluid this energy can never be dissipated and the vortex would persist forever. However, real fluids exhibit viscosity and this dissipates energy very slowly from the core of the vortex. (Rankine vortex). It is only through dissipation of a vortex due to viscosity that a vortex line can end in the fluid, rather than at the boundary of the fluid. For example, the wingtip vortices from an airplane dissipate slowly and linger in the atmosphere long after the airplane has passed. This is a hazard to other aircraft and is known as wake turbulence.
1.2 Dimensions - Vortex Tubes
1.2.2 Small With Muffler
1.3 Vortex Tube Specifications
Vortex Tube Specifications by a typical manufacturer
3200 series Vortex Tubes optimize temperature drop and airflow to produce maximum cooling power or Btu/hr. (Kcal/hr.). Specify 3200 series Vortex Tubes for most general cooling applications.
Model # SCFM* SLPM* Btu/hr.** Kcal/hr.** Size
3202 2 57 135 34 Small
3204 4 113 275 69 Small
3208 8 227 550 139 Small
3210 10 283 650 164 Medium
1.4 Some figures of the essential parts
A 1/4 ton of refrigeration in the palm of your hand!
Special high temperature vortex tubes
A Model 3215 Vortex Tube cools a die on a medical tube forming machine
Vortex Tubes are a low cost, reliable, maintenance free solution to a variety of industrial spot cooling problems.
A vortex can be any circular or rotary flow that possesses vorticity. Vorticity is a mathematical concept used in fluid dynamics. It can be related to the amount of "circulation" or "rotation" in a fluid. In fluid dynamics, vorticity is the circulation per unit area at a point in the flow field. It is a vector quantity, whose direction is (roughly speaking) along the axis of the swirl. Also in fluid dynamics, the movement of a fluid can be said to be vortical if the fluid moves around in a circle, or in a helix, or if it tends to spin around some axis. Such motion can also be called solenoidal. In the atmospheric sciences, vorticity is a property that characterizes large-scale rotation of air masses. Since the atmospheric circulation is nearly horizontal, the (3 dimensional) vorticity is nearly vertical, and it is common to use the vertical component as a scalar vorticity. Mathematically, it is defined as,
where is the fluid velocity.
1.6 Vortex Tubes and Spot Cooling Products
stainless steel Vortex Tubes convert an ordinary supply of compressed air into cold air at -50°F (-46°C) on one end, up to 260°F (127°C) on the other. There are no moving parts or refrigerants. They are commonly used to cool electronic controls, machining operations, gas samples, environmental chambers and more.
Vortex Tube products are available that are suited to specific applications. These include the:
Vortex Tubes are available in three sizes (small, medium and large) that have a wide range of cooling capacities.
Adjustable Spot Cooler that has a swivel magnetic base and control knob to select a temperature from -30°F (-34°C) to room temperature. It can be used to adjust thermostats, set hot melts, cool machined or molded plastics and more.
Cold Gun Aircoolant System replaces messy mist systems, cools dry machining operations with clean, cold air.
Mini Cooler prevents burning, melting and heat related breakage on small parts with 20°F (-7°C) air. It is ideal for small tools, blades, sewing needles, and lenses.
1.7 Types of vortex
In fluid mechanics, a distinction is often made between two limiting vortex cases. One is called the free (irrotational) vortex, and the other is the forced (rotational) vortex. These are considered as below:
Two autumn leaves in a counter-clockwise vortex (reference position).
Two autumn leaves in a rotational vortex rotate with the counter-clockwise flow.
Two autumn leaves in an irrotational vortex preserve their original orientation while moving counter-clockwise.
1.7.1 Free (irrotational) vortex
When fluid is drawn down a plug-hole, one can observe the phenomenon of a free vortex. The tangential velocity v varies inversely as the distance r from the center of rotation, so the angular momentum, rv, is constant; the vorticity is zero everywhere (except for a singularity at the center-line) and the circulation about a contour containing r=0 has the same value everywhere. The free surface (if present) dips sharply (as r − 2 ) as the center line is approached.
The tangential velocity is given by:
where Γ is the circulation and r is the radial distance from the center of the vortex.
In non-technical terms the circular streamlines toward the center can sweep out a given angle faster than the outer streamlines. The speed along the circular path of flow is held constant or decreases as you move out from the center. At the same time the inner streamlines have a shorter distance to travel to complete a ring. If you were running a race on a circular track would you rather be on the inside or outside, assuming the goal was to complete a circle? Imagine a leaf floating in a free vortex. The leaf's tip points to the center and the blade straddles multiple streamlines. The outer flow is slow in terms of angle traversed and it exerts a backwards tug on the base of the leaf while the faster inner flow pulls the tip forwards. The drag force opposes rotation of the leaf as it moves around the circle.
1.7.2 Forced (rotational) vortex
In a forced vortex the fluid essentially rotates as a solid body (there is no shear). The motion can be realized by placing a dish of fluid on a turntable rotating at T radians/sec; the fluid has vorticity of 2 T everywhere, and the free surface (if present) is a parabola.
The tangential velocity is given by:
where ω is the angular velocity and r is the radial distance from the center of the vortex.
3.1 Cooling Small Parts After Brazing
The Problem: Air conditioner parts assembled on an automatic brazing machine must be cooled to handling temperature prior to removal. The machine was capable of brazing up to four hundred pieces per hour. However, the time required for the parts to cool severely limited the production rate. Water cooling was unacceptable from the standpoint of both housekeeping and part contamination. Sa1
The Solution: (2) Model 3230 Vortex Tubes (with cold air muffler installed) were used to blow cold air on the parts after the brazing cycle. The vortex tubes were set at an 80% cold airflow (cold fraction) to produce maximum refrigeration. The parts were cooled from brazing temperature of 1450°F (788°C) to handling temperature of 120°F (49°C) within 20 seconds, allowing the machine to operate at its maximum production rate.
Comment: Compared to conventional refrigeration or water cooling, vortex tubes offer a number of advantages: low cost, compact design, inherent reliability and cleanliness. These attributes make vortex tubes the cost effective choice for many small part cooling operations
3.2 Cooling Small Parts After Brazing
A manufacturer of toothpaste seals the ends of plastic tubes with an ultrasonic welder prior to filling. As heat built up at the sealing jaw of the welder, release of the tubes was delayed. Tubes that were too hot would not seal resulting in a high rate of rejection.
The Solution: A Model 3215 Vortex Tube was used to direct cold air at the jaw of the welder. The cooling was transferred through the metal jaw to the tube seam while in the clamped position. Process time was reduced and rejected tubes were eliminated.
Comment: It amazes most people that the cooling from a small vortex tube can dramatically improve quality and throughput. The vortex tube is the low cost solution for cooling parts, chambers, heat seals and various processes. They're easy to use, can be adjusted to produce cold air down to -50°F (-46°C) and have no moving parts to wear out.
3.3 Cooling Vacuum Formed Parts
The Problem: A manufacturer of major appliances vacuum forms the plastic interior shell of refrigerators. The deep draw of the plastic and complex geometry left the four corners unacceptably thin. The corners would tear during assembly or bulge when insulation was inserted between the shell and exterior housing, resulting in a high rejection rate.
The Solution: (4) Model 3225 Vortex Tubes were positioned to cool the critical corner areas just prior to forming the plastic sheet. By cooling these areas, less stretching of the plastic occurred which resulted in thicker corners.
Comment: Rejected parts become very costly, especially when expensive materials and slow process times are involved. The cold air from the vortex tube is just the solution for big problems like this one. It can supply "instant" cold air down to minus 50°F (- 46°C) from an ordinary compressed air supply. Along with cooling other vacuum formed parts such as spas, bathtubs, tote pans and waste cans, it is ideal for cooling hot melts, ultrasonic welders, environmental chambers, etc.
Controlling Temperature and Flow in a Vortex Tube
Cold airflow and temperature are easily controlled by adjusting the slotted valve in the hot air outlet. Opening the valve reduces the cold airflow and the cold air temperature. Closing the valve increases the cold airflow and the cold air temperature. The percentage of air directed to the cold outlet of the vortex tube is called the "cold fraction". In most applications, a cold fraction of 80% produces a combination of cold flow rate and temperature drop that maximizes refrigeration, or Btu/hr. (Kcal/hr.) output of a vortex tube. While low cold fractions (less than 50%) produce lowest temperatures, cold airflow rate is sacrificed to achieve them.
Most industrial applications, i.e., process cooling, part cooling, chamber cooling, require maximum refrigeration and utilize the 3200 series Vortex Tube. Certain "cryogenic" applications, i.e., cooling lab samples, circuit testing, are best served by the 3400 series Vortex Tube.
Setting a vortex tube is easy. Simply insert a thermometer in the cold air exhaust and set the temperature by adjusting the valve at the hot end. Maximum refrigeration (80% cold fraction) is achieved when cold air temperature is 50°F (28°C) below compressed air temperature.
A 1/4 ton of refrigeration in the palm of your hand!
ADVANTAGES AND DISADVANTAGES
1. There is no leakage problem as it uses only air as the refrigerant
2. It is simple in design, and needs only control of valves, for appropriate functioning.
3. No moving parts.
4. Light in weight.
5. Requires less space.
6. Initial cost is low. At places where compressed air is readily available, its working expenses are also low.
7. No expertise attendance is required.
1. Low C.O.P.
2. Limited capacity.
1. Air suits.
3. Cooling of gas turbine rotor blades
4. Spot cooling
5. Cutting tools
6. Shrink fitting
7. Laboratory sample cooler
8. Heating and cooling requirement , simultaneously
9. Cooling enclosures
10. Air suits.
12. Cooling of gas turbine rotor blades
13. Spot cooling
14. Cutting tools
15. Shrink fitting
16. Laboratory sample cooler
17. Heating and cooling requirement , simultaneously
18. Cooling enclosures
A vortex can be seen in the spiraling motion of air or liquid around a center of rotation. Circular current of water of conflicting tides form vortex shapes. Turbulent flow makes many vortices. A good example of a vortex is the atmospheric phenomenon of a whirlwind or a tornado or dust devil. This whirling air mass mostly takes the form of a helix, column, or spiral. Tornadoes develop from severe thunderstorms, usually spawned from squall lines and supercell thunderstorms, though they sometimes happen as a result of a hurricane.
In atmospheric physics, a mesovortex is on the scale of a few miles (smaller than a hurricane but larger than a tornado).  On a much smaller scale, a vortex is usually formed as water goes down a drain, as in a sink or a toilet. This occurs in water as the revolving mass forms a whirlpool. This whirlpool is caused by water flowing out of a small opening in the bottom of a basin or reservoir. This swirling flow structure within a region of fluid flow opens downward from the water surface.
• In the hydrodynamic interpretation of the behaviour of electromagnetic fields, the acceleration of electric fluid in a particular direction creates a positive vortex of magnetic fluid. This in turn creates around itself a corresponding negative vortex of electric fluid.
• Smoke ring : A ring of smoke which persists for a surprisingly long time, illustrating the slow rate at which viscosity dissipates the energy of a vortex.
• Lift-induced drag of a wing on an aircraft.
• The primary cause of drag in the sail of a sloop.
• Whirlpool : a swirling body of water produced by ocean tides or by a hole underneath the vortex, where water drains out, as in a bathtub. A large, powerful whirlpool is known as a maelstrom. In popular imagination, but only rarely in reality, can they have the dangerous effect of destroying boats.
• Tornado : a violent windstorm characterized by a twisting, funnel-shaped cloud. A less violent version of a tornado, over water, is called a waterspout.
• Hurricane : a much larger, swirling body of clouds produced by evaporating warm ocean water and influenced by the Earth's rotation. Similar, but far greater, vortices are also seen on other planets, such as the permanent Great Red Spot on Jupiter and the intermittent Great Dark Spot on Neptune.
• Polar vortex : a persistent, large-scale cyclone centered near the Earth's poles, in the middle and upper troposphere and the stratosphere.
• Sunspot : dark region on the Sun's surface (photosphere) marked by a lower temperature than its surroundings, and intense magnetic activity.
• The accretion disk of a black hole or other massive gravitational source.
• Spiral galaxy : a type of galaxy in the Hubble sequence which is characterized by a thin, rotating disk. Earth's galaxy, the Milky Way is of this type
Some other examples .
• Rankine vortex
• Cyclonic separation
• Helmholtz's theorems
• Horseshoe vortex
• Viktor Schauberger
• Shower-curtain effect
• Strouhal number
• Vile Vortices
• Von Kármán vortex street
• Vortex engine
• Vortex ring
• Vortex tube
• Vortex cooler
• Vortex shedding
• Vortex Induced Vibration
• Wingtip vortices
• Quantum vortex
• REFER"Weather Glossary"' The Weather Channel Interactive, Inc.. 2004.
• "Glossary and Abbreviations". Risk Prediction Initiative. The Bermuda Biological Station for Research, Inc.. St. George's, Bermuda. 2004.
• Loper, David E., "An analysis of confined magnetohydrodynamic vortex flows". Case Institute of Technology. Washington, National Aeronautics and Space Administration]; for sale by the Clearinghouse for Federal Scientific and Technical Information, Springfield, Va. 1966. (NASA contractor report NASA CR-646) LCCN 67060315
Batchelor, G. K. (1967), An Introduction to Fluid Dynamics, Cambridge Univ. Press, Ch. ENCES
|Popular Searches: semi porous jugs, ex play nano projector, seminar report cover page, poject topics on vortex tube, whirlpool mi, vortex tube refrigeration system pdf, compound vortex controlled combustion ppt,|