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  • saurabhjain

    Calling Mechanical Engineers to collaborate on Twitter

    By saurabhjain

    If you are a mechanical engineering professional and have a twitter account .. we invite you in our mechanical engineering  campaign to collaborate on twitter.. Retweet the following status on https://twitter.com/mechportal/status/646544243649961985 Look forward for your presence. Regards Mechanical Engineeirng forum
    • 5 comments
    • 1,561 views
  • DrD

    A Question for Readers

    By DrD

    Many of you have asked me various questions, so now it is my turn. Let me lay a bit of background first, and then the questions.   I have had some conversations recently with JAG (one of the other writers here at ME Forums) regarding the choice of software for 3D modeling and analysis. JAG has made some excellent suggestions, specifically a cloud based program called Onshape. Unfortunately, for reasons that are unclear, my computer cannot run Onshape; I have worked with their help people for several hours, all to no avail. JAG recommends this in part because there is a "free version for the hobbyist" and a relatively inexpensive "full version for the professional." That is pretty attractive, but since I can't run it, I'm stuck.   I gather that virtually all engineering colleges these days are teaching some sort of 3D modeling and analysis software, but that raises a few questions in my mind. 1. If your college teaches brandX 3D software, what will you do when you go to work for a small company that cannot afford anything more than 2D drafting (simple CAD), with no analysis capability at all? How will you do your job then? You probably have your own pocket calculator, but will you have your own copy of ANSYS or Pro-E? 2. What software does your school teach (every students should have an answer to this question, so I expect lots of replies on this one!)? 3. If you have used software extensively for analysis of engineering problems (beam deflections, stress analysis, fluid flow, heat transfer, etc), are you confident  that you will be able to work all of those problems if there is no such software available to you on the job?   I might add, as sort of a postscript, most of you know that I am older than dirt (I just had another birthday, so the situation is even worse!), so I tend to look at things from an elderly perspective. One of my great fears as a working engineer was "What will happen when I'm ask to do something that I don't know how to do?" It happened more than once, and it usually resulted in a flurry of intense research to come up to speed on whatever topic was involved. I could usually do that because I have a pretty good library, and I knew how to use a university library as well. But in terms of software, I was always concerned that I had no FEA program, so how could I do problems that others were doing by FEA? I have come up with some interesting work-arounds, including writing my own FEA for some problems, but I never wanted to be dependent on software that I could not afford to own. So, back to my questions about: How are you going to buy your own copy of ANSYS? DrD
    • 28 comments
    • 2,919 views
  • DrD

    #20 -- A Question of Stability (Revised)

    By DrD

    Mechanics Corner
        A Journal of Applied Mechanics and Mathematics by DrD, #20
        © Machinery Dynamics Research, 2015
    A Question of Stability Introduction     The word stability in its several forms is widely used in nontechnical communication. A person whose life it highly consistent from day to day is said to have a stable life. When the political situation in a particular area appears to be unlikely to change, it is said to be stable. A person who is well balanced and unlikely to be easily provoked to anger is said to be a stable person. When the medical condition of a sick or injured person ceases to get worse, the person is said to be stabilized. A company on the verge of bankruptcy is said to be an unstable company. But what does the word stability mean in a technical context? Each of the foregoing examples hints at the technical meaning without really being explicit about it.   A factor g = accel of gravity was missing in the potential energy expression. That is now corrected.
        
     
        Stability.pdf
    • 16 comments
    • 5,736 views
 

Three-position synthesis with specific fixed pivots

======================================================================== Adapted from: Kinematics and Dynamics of Machinery by Robert L. Norton. ======================================================================== Download the much better formatted .PDF version from here: LINK ======================================================================== At times the designer would like to design a mechanism that would have to go through three positions. In this case the designer would start with the required three positions of the coupler and would work his way to decide on the location of the two pivot points for the ground link. The location of the two pivot points is not the result of the designer’s choice, but is decided by the geometry of the three positions required. This is not practical; often times the designer is constrained to work with specific pivot points to form the ground link while still achieving the required three positions by the coupler motion. This article discusses one of the simplest methods to go about doing that.     Let’s talk a look at this problem: Figure1: Problem Statement Design fourbar linkage to move the link CD shown between the positions C1D1 to C2D2 and then to C3D3. Use specified fixed pivots O2 and O4.  The first thing we need to do is to “invert” the problem. The way to do this is to think about the coupler (C1D1) as the ground instead and the ground (O2O4) as the coupler. For now we have one ground, (C1D1), and we have only one position for the coupler (O2O4). We are going to find two more positions for the now coupler (O2O4) that would correspond to the two other positions (C2D2). To do this we need to define the relation between The coupler and the ground.  Draw construction arcs from point C2 to O2 and from point D2 to O2 whose Radii define the sides of triangle C2O2D2. This defines the relationship of the fixed pivot O2 to the coupler line CD in the second coupler position. Draw construction arcs from C2 to O4 and from point D2 to O4 to define the triangle C2O4D2. This defines the relationship  of the fixed pivot O4 to the coupler line CD in the second position.   After locking the relative location of O2O4 in relation to the second position C2D2, it is  time to slide this ground, now coupler, to its new location as if it wasn’t the ground but the coupler. That’s to say, we are trying to answer the question: if C1D1 is the ground, where would the coupler, O2O4, be in the second position?   You can imagine this happening by sliding the triangle along the two lines C2C1 and D2D1. This results in a new position for O2’O4’. By doing this, we have pretended that the ground link moved from O2O4 to O2’O4’ instead of the coupler moving from C1D2 to C2D2. We have effectively inverted the problem.  Now we have two positions for the now coupler, O2O4; O2O4 and O2’O4’. We need another third position to correspond with the third position C3D3. To do this, we need to repeat the same process again by defining the relation of the link O2O4  in relation to C3D3 after that we need to shift it back to C1D1 as if the link O2O4 was the coupler not the ground.  Performing this will result in the third position O2’’O4’’. This is the relative location of the link O2O4 in its third position as a coupler in relation to the new ground link C1D1. Now we have three positions for the pretended coupler O2O4. O2O4, O2’O4’ and O2’’O4’’ Right now the problem is fully redefined; we have three positions for the newly decided coupler O2O4 and the link CD in the first location C1D1. We can now rename those three positions O2O4, O2’O4’ and O2’’O4’’ to E1F1, E2F2 and E3F3. We can now deal with the three positions as we would normally solve for three position coupler problem.  First we need to draw the lines E1E2 and E2E3. Then we have to draw the perpendicular bisectors of these lines. The bisectors will intersect in point G. We repeat the same process for point F; draw lines F1F2 and F2F3 then draw the perpendicular bisector of these lines. These two bisectors will intersect in point H. Now we have a fourbar linkage, GEFH, in which the coupler, EF, goes through three positions.  If you recall, EF is not actually our coupler. EF represents our ground O2O4. What we need to do now is to re-invert the problem again to its original form. By switching EF to be the ground link and GH to be the coupler link we reach at this linkage. Now we have our coupler, link GH, that should be connected back to the first position that we wish to achieve; C1D1. By extending link 3, GH, to reach to C1D1 we form our final mechanism that guides the coupler, link 3 (HGCD) through the three required positions. The final thing we need to do is to add a driver Dyad to drive the link O4H. This is simply done by treating O4H as rocker in a crank rocker design problem. The rocker, now O4H, has to pass through H2 and H3 to result in the required motion. Afterwards, the final mechanism is checked for toggle positions and that it can reach the required positions smoothly and in orderly fashion. In conclusion, the designer is not limited to the resulting fixed pivots for the solution of three positions coupler problems. By using the illustrated method, the design can specify the required fixed pivots and the required coupler motion and work his way around to getting those two requirements achieved. Adapted from: Kinematics and Dynamics of Machinery by Robert L. Norton.

M.Shehata91

M.Shehata91

 

LightSail Energy

LightSail Energy is one of the most eminent startups that hails from Silicon Valley founded by Danielle Fong, Steve Crane, and Ed Berlin in 2009. LightSail Energy has the concept of low-cost grid-scale energy storage solution in order to optimise power grids, democratizing access to energy and adhere on sustainable development. Investors such as Khosla Ventures, Innovacorp, Triple Point Capital, Peter Thiel, Bill Gates have invested in LightSail Energy. LightSail Energy produces one of the world cleanest and economical storage systems.The website of the startup is http://www.lightsail.com/  They have designed an excellent method of capturing heat energy and regenerating useful energy from compressing air. The process involves injecting fine, a dense mist of water spray which rapidly absorbs heat energy of compression and provides it during expansion. The system is fully reversible. To store energy, the system draws electricity from the grid and converts it into compressed air and heat. To deliver energy, compressed air and heat are turned back into electricity using the same system. The system has 300+ hours of operation, 10 degrees Celcius temperature difference, 1000 rpm reciprocating piston compressor/expander and 250 KW highest power achieved. For low-cost storage, air is packed in a convenient shipping container and for large storage, underground caverns are used. This way of storing energy could be helpful in transforming intermittent wind and solar power into baseload energy.     

Shalini Chakraborty

Shalini Chakraborty

 

VOXEL8

Voxel8 was founded in 2014 by scientists and engineers from Harvard University. This company was supported by Braemar Energy Ventures and ARCH Venture Partners. This company aims at developing digital footwear manufacturing systems which revolutionalize how footwear products are designed, manufactured and sold to the customers. In July, the company raised funding of $12 million to which Autodesk also contributed.It has also been named as one of the MIT Technology Reviews of 50 smartest companies in 2015. Voxel8's engineering grade polyurethanes are printed using ActiveMix system which enables programmable control of composition, geometry, mechanical properties of printed features on upper and 3D shapes. Voxel8 printer can pause automatically during a print to allow for electronic components to be placed inside specially printed cavities. Then the same machine can print the conductive traces connecting those components before completing the project. The ability to smoothening the printing process is done through innovative silver ink. Also, AutoDesk developed a new piece of software Project Wire from the ground to top in order to print 3D electronic devices. The digital manufacturing system of Voxel8 has short design and production cycle; utilizes zero tooling; is compact, flexible, scalable enabling localized production and distribution to minimize warehousing and shipping cost.  

Shalini Chakraborty

Shalini Chakraborty

 

can centrifugal pump handle gas with liquid?

Triple-volute centrifugal pump can handle up to 20 percent entrained air, where a typical centrifugal pump can only deal with air entrainment levels of 5 to 8 percent. Along with entrained air, cavitation is a top candidate for causing pump problems. Cavitation occurs when the pump’s internal pressures are lower than the vapor pressure of the liquid which results in rapid vapor formation within the pump which collapse as the liquid is swept into the higher pressure regions of the pump. The cavitation effect may cause material damage to the impeller and possibly casing, which is resultant of the sudden formation and implosion of vapor bubbles. The frequencies recorded of cavitation “hammering” are from 1,000 cycles per second up to 25,000 cycles per second and the resultant damage is generally termed pitting. The noise (sand, gravel, rumbling) heard outside the pump during cavitation, is caused by the collapse of the vapor bubbles. The energy expended in accelerating the liquid to high velocity in filling the void left by the bubble is a loss, and causes the drop in head associated with cavitation. The loss in capacity is the result of pumping a mixture of vapor and liquid instead of liquid. Even a slight amount of cavitation will reduce the capacity significantly. Entrained air gets into a pump, the lower-pressure bubbles become larger. If an air bubble gets big enough to cover the impeller eye, the pump becomes airbound.   A generality to keep in mind when evaluating entrained air vs. cavitation is this: 1) If it’s entrained air, the liquid entering the pump already has liquid and air. In the pump it’s liquid and air. And it comes out liquid and air. 2) With most traditional cavitation, the liquid coming into the pump is fully liquid. As soon as it hits the inlet of the pump, it starts to vaporize and comes out as liquid. Only about 75 percent of cavitation creates pump noise but the material damage is always there. In cavitation, the pitting damage on the impeller. Three rules of thumb for determining whether cavitation is causing pump performance problems: 1) Throttle the discharge and check the noise – Throttle back the pump on the discharge (not the suction) to lower the flow rate. If the pump noise goes away, it’s about an 80 percent probability that cavitation is the problem. 2) Raise the liquid level and check for noise – If you raise the liquid level in the supply tank and the pump noise goes away, it’s about an 80 percent probability of cavitation. 3) Cool the liquid and check for noise – If the process liquid is normally at 200°F and you cool it to 180°F and the pump noise goes away, it’s probably cavitation.  

parsottam

parsottam

 

Pneumatic or air braking system in automobile | Construction and working of pneumatic braking system

A brake which uses air as a working fluid is known as pneumatic brake. The system actuated to apply this phenomenon is know as pneumatic brake system. An pneumatic brake system or a compressed air brake system is a type of friction brake for vehicles in which compressed air pressing on a piston is used to apply the pressure to the brake pad needed to stop the vehicle. Construction of pneumatic braking system   The simplest air brake system consists of An air compressor A brake valve series of brake chambers at the wheels unloader valve A pressure gauge and a safety valve and an air reservoir. These are all connected by tubes. Some air braking systems may have additional components such as stop light switch low pressure indicator An air supply valve to supply air for tyre inflation A quick release air quickly from the front brake chambers when the brake pedal is released A limiting valve for limiting the maximum pressure in the front brake chambers and a relay valve to help in quick admission and release of air from the rear brake chambers. Working of pneumatic braking system The air compressor operated by the engine forces air at a pressure of 9-10 kscm (kilo standard cubic meters) through the water and oil separator to the air reservoir. The air pressure in the reservoir is indicated by a pressure gauge. The reservoir contains enough compressed air for several braking operations. From the reservoir the air is supplied to the brake valve. As long as brake pedal is not depressed, brake valves stop the passage of air to brake chambers and there is no braking effect.   When the brake pedal is depressed, the brake valves varies its position and compressed air is admitted into the wheel brake chambers. In the chambers the air acts upon flexible diaphragms, moves them the pushes out the rods connected with the levers of the brake gear cams. The cams turn and separate the shoes thus braking the wheels. When the brake pedal is released, the supply of compressed air is cut off from the brake chambers and they are connected to the atmosphere. The pressure in the chambers drops, the brake shoes are returned to their initial position and the wheels run free. The brake valve is equipped with a servo mechanism which ensures that the braking force on the shoes is proportional to the force applied to the pedal. Besides the valve imparts a relative reaction to the movement of the pedal so that the driver can sense the degree of brake application. IMAGE SOURCE :- google  

Rishabh Pandey

Rishabh Pandey

 

#44 Mouse Trap / Pendulum Dynamics Challenge

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 44
      Machinery Dynamics Research, 2017
     Mouse Trap / Pendulum Dynamics Challenge - Part I
Introduction     Mice are a problem all over the world, and as a result, I'm sure that there are mouse traps of various sorts found everywhere. It would be utterly amazing if this were not true! In the USA, there is a very common type of mouse trap that I have seen used all my life, the sort of system shown below in Figure 1. I want to spend a few minutes discussing this mouse trap, to be certain that all readers understand how it works, before moving on to the main part of the post. MouseTrapPendulumDynamics-1.pdf

DrD

DrD

 

#43 Four-Bar / Toggle Linkage Mechanism

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #43 (c) Machinery Dynamics Research, 2017   Four-Bar / Toggle Linkage Mechanism Introduction   I believe that it would be correct to say that all of the single degree of freedom mechanisms that I have discussed on ME Forums have involved only a single loop. This might lead a reader to conclude that a single degree of freedom implies only a single loop, and vice versa, that a single loop implies only a single degree of freedom. Neither of these statements is true. In this note, I want to discuss a counter example, a mechanism called the four-bar / toggle linkage; it is shown in Figure 1. TogglePress.pdf

DrD

DrD

 

Triple Rocker

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD July 31, 2017 Triple Rocker Over at the Kinematics of Machines club, I recently ask if anyone could show me an example of a four-bar linkage that would be classed as a triple rocker. In the terminology of four-bar linkages, a link is classed as either a crank or a rocker: Crank - can rotate in a complete circle Rocker - cannot rotate in a complete circle] Thus my question was for an example of a four-bar linkage where no link is able to rotate around a full circle. My request has not generated any answers, but fortunately, I stumbled onto one. Since the definition of a rocker is a link that cannot rotate completely, it is evident that the linkage shown is in fact a Triple Rocker. None of the links is able to move through a complete revolution. If we try to rotate the input (left) link further down, it cannot happen without stretching the combination of the coupler and the output (right) links. When the input link (left side) gets to the top, again its motion is stopped by the need to stretch the coupler and output link. Thus, a figure I drew as an illustration for something else turns out to be a Triple Rocker, the item I was looking to find. In connection with four-bar linkages, some readers will have heard of Grashof's theorem. Let s = length of shortest link L = length of the longest link p, q = lengths of the two intermediate links Grashof's theorem says that a necessary and sufficient condition for at least one link to be a crank (able to rotate entirely around), it is necessary that s + L < p + q This inequality is not satisfied for the four-bar that I drew by chance, so Grashof's theorem says that none of the links can be a crank. That is precisely the condition required for a Triple Rocker (a ground link plus three moving but not fully rotating links). So, there you have it. That is an example of a Triple Rocker, and we now have the criteria for identifying such as a four-bar linkage that does not satisfy Grashof's Theorem.    

DrD

DrD

 

Engine

About engine;                          An engine or motor is a machine,designed to convert one form of energy into mechanical energy.Heat engine burn a fuel to create heat, which is then used to create a force. Electric motors convert electrical energy into mechanical motion; pneumatic motors use compressed air and clockwise motors in wind up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and eventually motion.  TYPES OF ENGINE (i). External combustion engine: In external combustion engine, the combustion of fuel takes place outside the engine. Example: steam engine.(ii). Internal combustion engine: In internal combustion engine, the combustion of fuel takes place inside the engine. Two stroke and four stroke petrol and diesel engine are the examples of internal combustion engine. 1.The I.C. engines are classified on the following basis: (i). Reciprocating engine: In reciprocating engine, there is a piston and cylinder, the piston does reciprocating (to and Fro) motion within the cylinder. Due to the reciprocating motion of the piston, it is called reciprocating engine. 2 stroke and four stroke engines are the common examples of reciprocating engine. (ii). Rotary engine: In rotary engine, the rotor does rotary motion to produce power. There is no reciprocating motion. A rotor is present in the chamber which does rotary motion inside a chamber. Wankel rotary engine , turbine engines are the rotary types of engine. 2. Types of Fuel Used On the basis of types of fuel used, the engine is classified as petrol engine, diesel engine and gas engine. (i). Petrol engine: The engine which uses petrol for its working is called petrol engine. (ii). Diesel engine: The engine which uses diesel for its working is called diesel engine. (iii). Gas engine: An engine using gas fuel for the working is called gas engine. 3.Cycle of Operation On the basis of cycle of operation the engine types are: (i). Otto cycle engine: These types of engine works on Otto cycle. (ii). Diesel cycle engine: The engine working on diesel cycle is called diesel cycle engine. (iii). Dual cycle engine or semi-diesel cycle engine: The engine that works on both diesel as well as Otto cycle is called dual cycle engine or semi diesel cycle engine. 4.Number of Strokes On the basis of number of stroke, the types of engine are: (i). Four Stroke Engine: It is an engine in which the piston moves four times i.e.2 upward (form BDC to TDC) and 2 downward (from TDC to BDC) movement in one cycle of power stroke is called four stroke engines. (ii). Two Stroke Engine: The engine in which the piston does two times motion i.e. one from TDC to BDC and other from BDC to TDC to produce a power stroke is called two stroke engines. (iii). Hot spot ignition engine: This type of engine is not in practical use. 5. Type of Ignition On the basis of ignition, the engines are classified as: (i). Spark ignition engine (S.I. engine): In spark ignition engine there is a spark plug which is fitted at the engine head. The spark plug produces spark after the compression of the fuel and ignites the air fuel mixture for the combustion. The petrol engines are spark ignition engine. (ii). Compression ignition engine (C.I. engine): In Compression ignition engine there is no spark plug at the cylinder head. The fuel is ignited by the heat of the compressed air. The diesel engines are compression ignition engine. 6. Number of Cylinders On the basis of number of cylinders present in the engine, the types of engine are: (i). Single cylinder engine: An engine which consists of single cylinder is called single cylinder engine. Generally the single cylinder engines are used in motorcycles, scooter, etc. (ii). Double cylinder engine: The engine which consists of two cylinders is called double cylinder engine.  (iii). Multi cylinder engine: An engine which consists of more than two cylinders is called multi cylinder engine. The multi cylinder engine may have three, four, six, eight, twelve and sixteen cylinder. 7. Arrangement of Cylinders On the basis of arrangement of cylinders the engines classification is: (i). Vertical engine: in vertical engines, the cylinders are arranged in vertical position as shown in the diagram. (ii). Horizontal engine: In horizontal engines, the cylinders are placed horizontal position as shown in the diagram given below. (iii). Radial engine:  The radial engine is reciprocating type internal combustion engine configuration in which the cylinders radiate outward from a central crankcase like the spokes of a wheel. When it is viewed from the front, it resembles a stylized star and is called a ‘star’ engine. Before the gas turbine engine is not become predominant, it is commonly used for aircraft engines. (iv). V-engine: In v types of engine, the cylinders are placed in two banks having some angle between them. The angle between the two banks is keep as small as possible to prevent vibration and balancing problem. (v). W type engine: In w type engines, the cylinders are arranged in three rows such that it forms W type arrangement. W type engine is made when 12 cylinder and 16 cylinder engines are produced. (vi). Opposed cylinder engine: In opposed cylinder engine, the cylinders are place opposite to each other. The piston and the connecting rod show identical movement. It is runs smoothly and has more balancing. The size of the opposed cylinder engine increase because of its arrangement. 8. Valve Arrangement  According to the valve arrangement of the inlet and exhaust valve in various positions in the cylinder head or block, the automobile engines are classified into four categories. These arrangements are named as ‘L’, ‘I’, ‘F’ and ‘T’.  It is easy to remember the word ‘LIFT’ to recall the four valve arrangement. (i). L-head engine: In these types of engine, the inlet and exhaust valves are arranged side by side and operated by a single camshaft. The cylinder and combustion chamber forms and inverted L. (ii). I-head engine: In I-head engines, the inlet and exhaust valves are located in the cylinder head. These types of engine are mostly used in automobiles. (iii). F-head engine: It is a combination of I-head and F-head engines. In this, one valve usually inlet valve is in the head and the exhaust valve lies in the cylinder block. Both the sets of valve are operated by the single camshaft. (iv). T-head engine: In T-head engines, the inlet valve located at one side and the exhaust valve on other side of the cylinder. Here two camshafts are required to operate, one for the inlet valve and other one is for the exhaust valve. 9. Types of cooling On the basis of types of cooling, the engines are classified as: (i). Air cooled engines: In these engines, the air is used to cool the engines. In air cooled engines the cylinder barrels are separated and metal fins are used which provides radiating surface area that increase cooling. The air cooled engines are generally used in motorcycles and scooters. (ii). Water cooled engines: In water cooled engines, the water is used for the cooling of engine. Water cooled engines are used in cars, buses, trucks and other four wheeled vehicles, heavy duty motor vehicles. An anti-freezing agent is added in the water to prevent it from freezing during cold weather. Every water cooled engines has radiator for the cooling of hot water from the engine. Beside above types of engine, the internal combustion engine is also classified on the basis of the following. 1. Speed:  On the basis of speed, the types of engines are: (i). Low speed engine (ii). Medium speed engine (iii). High speed engine 2. Method of Fuel Injection On the basis of method of fuel injection the engines are classified as: (i). Carburetor engine (ii). Air injection engine (iii). Airless or solid injection engine 3. Method of Governing (i). Hit and miss governed engine: It is an engine type in which the entry of the fuel is controlled by the governor. It controls the speed of the engine by cutting off the ignition and fuel supply of the engine at very high speed. (ii).Quantitative governing: In this system of governing, the quality of charge (i.e. air-fuel ratio of the mixture) is kept constant. But the quantity of mixture supplied to the engine cylinder is varied by means of a throttle valve which is regulated by the centrifugal governor through rack and pinion arrangement. the part load efficiency of SI engine is poor because air fuel ratio remains constant even if we need low power (iii).Qualitative governing: In this system of governing, a control valve is fitted in the fuel delivery pipe, which controls the quantity of fuel to be mixed in the charge. The movement of control valve is regulated by the centrifugal governor through rack and pinion arrangement. part load efficiency of I C engine is good because we can use lean mixture and rich mixtures easily according to our requirement 4. Application (i). Stationary engine: Stationary engine is an engine in which its framework does not move. It is used to drive immobile equipment like pump, generator, mill or factory machinery etc. (ii). Automotive engine: These are the types of engines which are used in automobile industries. For example: petrol engine, diesel engine, gas engine are internal combustion engines falls in the category of automotive engine. (iii). Locomotive engine: The engines which are used in trains are called locomotive engines. (iv). Marine engine: The engines which are used in marines for boat or ship propulsion is called marine engine. (v). Aircraft engine: Types of engine which are used in aircraft is called aircraft engine. Radial and gas turbine engines are used in aircraft propulsion.

Sijo

Sijo

 

#42 Gear Pair Problem

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 42
    © Machinery Dynamics Research, 2017
Gear Pair Problem     
Introduction     In this post, I want to discuss a seemingly simple problem currently being discussed at Physics Forums (PF). The original question, posed by someone, perhaps a student but perhaps not, is quoted below:
     
So, we have a pinion and a gear. I give an input torque Tp in the clockwise direction. Therefore, the pinion will rotate with ωp angular velocity in clockwise and the gear ωg in counter-clockwise. There is a load TL against the gear motion. The bearing friction both in pinion and gear are considered by means of linearly-viscous damping coefficients cp and cg for pinion and gear, respectively. The friction between the gear mesh is neglected at this point. The moments of inertia of the pinion and the gear are Ip and Ig, respectively. Moreover, the radii of the pinion and the gear are rp and rg, respectively. My question is what the output torque To is because I want to find the efficiency of this gear pair.
I have tried four options for To and simulated them in MATLAB, but I have not found the correct results yet. Followings are the explanation of each option I tried for To.     The sketch in Figure 1 and the two paragraphs following are exactly as posted by the original questioner. There follows on PF a long sequence of responses and more questions, but he still seems no closer to understanding what is going on. Let us see what we can do to help him.
    Before someone thinks badly of me for not helping him, let me say that I did give several hints, but the rules of PF forbid me to actually post an analysis. I have been severely scolded in the past for doing just that. 42 Gear Pair Problem.pdf

DrD

DrD

 

Sickle Innovations

Agriculture is the backbone of the strong economy. Agriculture is demographically the broadest sector and plays an important role in the overall economic development in India since India ranks second worldwide in farm outputs. So, this is another Mechanical Startup Story from the Agriculture based start-up Sickle Innovations. Sickle Innovations started in 2014 by the encouragement of Centre for Product Design and Manufacturing and Indian Institute of Science Bangalore. Since in Indian demographic scenario, not the availability of farm labors, low profits and labor drudgery problems are encountered frequently, the aim of the startup involves developing innovative mechanization solutions through Design Thinking. The startup's website goes as follows http://www.sickle.in/ The mango stem and transport it safely to the ground with the product name Hectare. The Cotton Picking Machine; being the second largest producer of cotton, challenges such as manual labor, intensive labor health problems have to be tackled by cotton producers. This handheld machine was developed by the company with patented technology that can double labor efficiency and enhances farmer income by 50%. The design eliminates injuries from cotton bur pricks and is self-powered fully automatic harvesting machine. Being the world's largest producer of milk and bovine population 3 times larger than USA, milk production per cow/buffalo is lower.Imported machines cannot suffice the need of country environments and cow breeds.Hence, the design of the company's machine keeps full potential with the local scenario.  Hence, startups are equally important when it comes to tackling small or huge problems in day to day scenario with innovative simple solutions. Keep Going Ahead and Keep Bringing Innovative Ideas!!!

Shalini Chakraborty

Shalini Chakraborty

 

ATHER ENERGY

Holla People!!!! Since it has been a long time I was waiting for starting the blog on Mechanical Startups, my first entry to the new blog starts with the few hardware startups in India. ATHER ENERGY is a privately owned founded by Swapnil Jain and Tarun Mehta in 2013 headquartered in Bangalore Karnataka.  This budding startup has received fundings from Hero Motocorp, Tiger Global & Flipkart. Profoundly being a part of Automotive industry and producing electric vehicles, in the in-house designed Lithium-ion battery pack design. The Ather S340 has a touchscreen dashboard connected to the cloud, host of smart features and offers a top speed of 72 kph. The scooter is designed in-house by Ather and will be manufactured in India. Their website is known as  www.atherenergy.com   The Ather S340 features from remote diagnosis to onboard navigation and rider behavior. The S340 stands for S (Scooter), 3 for 3KWH, 4 for 40 Amp-Hour Battery Capacity.  It has lightweight aluminum chassis and can reach speeds of 72 kph and a range of up to 60 km. The vehicle can charge up to 80% in 50 minutes in fast charging mode.  The Ather S340 has a Linux based dashboard with the 7-inch touch screen that integrates with cloud-based data through a 3G SIM card to enable constant data transfer and updates.The rider can create his user profile on the scooter, access onboard navigation and use the touch screen to switch between two modes - Sports and Economy. Different sensors installed in the scooter allow it to send all the information about rider behavior and riding pattern like braking, acceleration, mileage, efficiency to the cloud.Ather energy can also carry out upgrades on the scooter over the air due to 24X7 internet connectivity, without the need to bring the scooter to the manufacturer. The vehicles produced by ATHER ENERGY are covered under FAME (Faster Adoption and Manufacturing of (Hybrid &)Electric Vehicles) scheme that offers incentives to the electric and hybrid vehicles ranging from Rs.1,800 to Rs.29,000 for scooters and motorcycles and Rs.1.38 Lac for cars. FAME is a part of National Electric Mobility Mission Plan by Government of India. As per the scheme, the customer can get the incentive in form of lower cost of the hybrid or electric vehicles at the time of purchase and the manufacturer can claim the incentive from the government at the end of each month.

Shalini Chakraborty

Shalini Chakraborty

 

Modeling Hysteresis

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #41 (c) Machinery Dynamics Research, July 2017   Modeling Hysteresis 1. Introduction What do you know about hysteresis? Many Mechanical Engineers will associate this term with the magnetization curve of a piece of magnetic material, and quickly conclude, "I don't have to worry about that!" But that would be wrong. While hysteresis does occur in magnetic systems, it happens in many other situations as well, many of them situations of concern to mechanical engineers. Figure 1 Typical Hysteresis Curve   Figure 1 shows a typical hysteresis curve, and it makes no difference as to what physical phenomena are involved. The red curve is the actual hysteresis curve. The blue curve is called the "spine." Read more at 41 Modeling Hysteresis.pdf  

DrD

DrD

 

Two Short Math Problems

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #40 July, 2017   Two Short Math Problems Do you ever read the ads that appear on ME Forum? I try to avoid them as much as possible, but an organization called BRILLIANT has put up some interesting math problems of late that have caught my eye. Two of them are the subject of today's post. The first problem that I want to discuss is actually more recent than the other, but it gives us a good place to start. Following that, we'll go on to the second problem. Along the way, I want to talk about philosophy as well as simply how to solve tow specific problems. The main lessons to be learned here are in regard to how we use mathematics in the practice of Mechanical Engineering. 40 Two Short Math Problems.pdf

DrD

DrD

 

Comments on a Textbook - Khurmi & Gupta

Mechanics Corner
A Journal of Applied Mechanics and Mathematics by DrD, #39
(c) Machinery Dynamics Research, 2017
Comments on a Textbook
Theory of Machines
by
R.S. Khurmi & J.K. Gupta
1 Introduction
Recently, through the wonders of the Internet, I have come across a copy of the textbook Theory of Machines by R.S. Khurmi and J.K. Gupta (S.Chand & Co., Ltd., 2005). Since theory of machines has been my primary technical interest since the early 1980s, I was interested to see what would be in this book, particularly in view of the many favorable comments posted in regard to it. Many people seem to think that this is a most excellent book, and I’m always interested to see what brings forth comments of that sort.
As I looked through the Table of Contents, I saw that one of the last chapters was given to the topic of Torsional Vibrations (Ch. 24). Since the area of torsional vibrations has been a topic of intense personal interest for 40+ years, I was naturally drawn to this chapter. The comments that follow are based on what I found in that chapter; I have not reviewed the remainder of the book at all. In my comments below, I will refer to the authors, Khurmi and Gupta, simply as K&G to avoid writing their names out repeatedly.
One of the things I think is necessary in a textbook is that it should be directed toward teaching students to solve real problems, not simply textbook examples. Certainly, textbook examples should be simple so that they can be easily understood, but they should also be as general as possible. Where they involve special, limiting assumptions that may likely not be true in actual practice, this should be made clear. Failure to do that marks an author as one who has never actually done engineering in the real world. If the assumptions are not made clear, there is a tendency for students to later want to simply apply directly the results from the textbook problem, not realizing that they may not apply at all. So, what did I find? Comments on Textbook - Khurmi.pdf

DrD

DrD

 

Rocket Homework Problem

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, #38
      Machinery Dynamics Research, 2017
Rocket Homework Problem Introduction     Most engineers find problems involving rockets to be exciting. There is something about a rocket that fires our imagination, whether we think of going to the moon or one of the planets, or simply of shooting down an incoming missile. The subject of this post involves a rocket on a mobile launcher. The rocket is intended to be transported in a horizontal position, but it must be elevated in order to be fired. Both positions are shown in the accompanying figure. Read the attached PDF for more on this problem. RocketHWProblem.pdf   Addendum:  One reader has posted a proposed solution for this problem as a comment. It was not my intent that solutions be posted in the comments at all. I only want solutions sent to me by the personal message system. DO NOT POST YOUR SOLUTION IN THE COMMENTS!! Regarding the solution that has been posted, let me say the following: 1. Some of the answers are correct, while others are not. Do not be misled into following this solution because there are errors therein. 2. Even where the results are correct, there are a number of methods that I would not recommend using. Thus again, I say to all other readers, do not follow this solution, but work it out for yourself. 3. Be sure to document your solution, so that if someone else were to ask how you obtained a particular result, you would be able to explain it in a clear and reasonable manner.      

DrD

DrD

 

Where Would You Publish It?

Mechanics Corner Where Would You Publish It? Since long before my time, there has been a desire to have important results published where they become accessible to many others. Some of the great names, such as Newton, Euler, Bernoulli, and others, we know primarily because of what they published. Their work formed the fundamentals upon which modern engineering and science is built. Publication of research results has long been particularly important to faculty members; it is often taken as a measure of just how intelligent and useful they are (there is a lot of doubt about the validity of this measurement, but that has not prevented it use). When I was a young faculty member (many, many years ago), there was the mantra "Publish or Perish." This referred to the idea that those faculty members that did not publish research work would not receive tenure, and would be out of employment after several years. Agencies that funded research were eager to see publication of results that they had funded; it was considered evidence of the importance of the work supported by the agency. This was particularly true of the National Science Foundation (NSF) and other governmental funding sources in the USA. It was not too long before publication was replaced as the measure of academic value, to be replaced by funding. A faculty member was expected to write research grant proposals, and the Dean's Office expected a significant cut of the proceeds, ostensibly for their role in "supervision." In practical terms, Dean's Offices almost never contributed anything of value to research efforts, but this was a form of graft to assure their cooperation. But publication remained essential as well. Any research that could not be published in a reputable journal was considered to be unworthy, a waste of time. So the criteria for success became, get money and publish, a tougher goal that simply publishing. More recently, the goal posts have been moved again. Today the big cry is for "undergraduate research." To my mind, this is the height of absurdity. For folks who are just beginning to learn a profession, how can anyone think that they are capable of fundamental new discoveries? For undergraduates that are still struggling with Mechanics of Materials, do we really expect them to discover new understanding of fatigue or fracture mechanics? For a student laboring to understand dynamics, do we really expect them to come up with breakthroughs in orbital mechanics, seismic shock resistance, or multidegree of freedom models for gear box noise? But, rest assure, there is no place more insane than a university!! The utterly absurd is treated as absolutely essential!! Thus far, I've talked a lot about academia, but we must not neglect industry. Publication is important to industrial firms as well, although for different reasons. Published research, done by your firm, is a way of establishing the technical excellence of your company. If you want to be known as an industry leader in your area, you want your employees to publish work that makes the company look like it is on the cutting edge of new technology. Often industry imposes constraints on what can be published; they do not want proprietary information to be put into the public domain. But they really like to have results published that make them look sophisticated, ahead of the pack, so to speak. For consulting engineers, publication can be important as a means to establish your expertise in an area. If you publish a lot in a particular subject area, people begin to think you kow something about the area and come to you when they have problems. New work is the life blood of consulting engineers, so this can be very important. You will also be asked to review the work of others and to sit on panel discussions and other public appearances that can upgrade your image and bring in more work. I hope that it is evident that most engineers will need to publish some work at some point in their career. It may be a central matter of those in more research oriented areas, or it may be only occasional for those in less cutting edge business sectors, but everyone will eventually need to publish something. So, back to the original question: Where Would You Publish It? Most professional societies publish research work, and there are also a vast number of trade magazines. Fifty years ago, when the volume of "research" was much less, it was not too difficult to publish through any number of venues. I have published articles through the various Transactions of the American Society of Mechanical Engineers (ASME), through the Transactions of the Society of Automotive Engineers (SAE), and the Journal of Mechanism and Machine Theory. I have also published through some much less well known venues such as Machine Design magazine, and most recently through IPTEK Journal, a small journal headquartered in Indonesia (that was an experience!) and other places. But the game is ever changing! When I first began to publish papers back in the 1960s, it was a fairly simple process. You wrote up your text, with figures and equations, and mailed it to the editor in type written form (this before the days of word processing). After a few months, you would get something back from the editor. It might be an outright acceptance (rare), a conditional acceptance which meant that the paper would be accepted with certain modifications/corrections that were described in the letter (fairly common), or it might be a flat rejection (not extremely uncommon). If you got a conditional acceptance, you made the revisions, and about 6 months later, it would be published in whatever journal you were dealing with. The classier the journal, the higher the standards were, but all worked about the same. Many of these organizations that publish papers also hold meetings, and they want people to come to the meetings. I have presented papers at the ASME Winter Annual Meeting (always in New York), at various SAE meetings, etc. But, there is a problem. It is expensive to go to these meetings. There is the travel expense (transportation, hotel, food, etc), and there is usually an admission fee (you have to pay money to present your own paper, an absurdity, but very real). Often the papers is only accepted for publication if you agree to come to the meeting to present it and pay the admission fee. Now if your paper is the result of funded research, or if your employer will pay the expenses, this is usually not a personal burden. If neither of these apply, the burden of the costs fall of the individual, and it is often prohibitive, often approaching $1000. The publisher then sell your work for a subscription fee, usually several hundred dollars per year. Libraries are the principal subscribers (university, municipal, and industrial libraries), along with a few individual. In recent years, there has been a glut of material offered for publication, and everybody thinks that their paper is extremely important for the world to see. The volume of publications have increased drastically, but so has the cost. Who will pay for all the paper, printing, etc.? For years, it has been common to impose what are called "page charges," typically around $100 per page, to publish in most journals. Funded research usually included a line item for page charges, so that paid those bill. In the past, any unfunded research, if it was accepted, would usually be published with the page charges waived. Today, that is not longer true, and page charges are usually mandatory. But it gets worse. We all know the Internet is a wonderful thing, but it does have some downsides as well. One of those downsides is in the area of publication. There is a relatively recent trend in publication called "Open Access," and it is particularly popular with a number of on-line journals. These journals are free to all on the internet, but the journals charge the authors a very steep price to publish their work. Thus you, as an author, must prepare the article according some very demanding rules about formatting, style, etc, then you must pay several thousand dollars, just so the world can see your work. It means that your work becomes available to all for free (which is a good thing), but it means that you the author must bear the full cost of supporting the publishing operation. I know that I, as an individual, cannot afford this, and thus it is almost impossible for me to publish anything now. It means that those with money will get their work published, and those without money will not. The quality of the published work is virtually certain to decline, but that is modern life. What can you do? As a closing note, I'm currently writing another technical paper that I would like to publish, preferably where folks who work with IC engines will read it. I think I have something of real value to present, but I have no idea where I will publish it, or if I will be able to find a publisher at all. If any readers have a suggestion for an appropriate journal, I would certainly appreciate a suggestion in the comments. DrD    

DrD

DrD

 

The True Value of Certification

The link below is an article about the value of certification for manufacturers. It is a heavy sell for certification. In my opinion it misses the most basic benefit of certification, which is the path to getting certified. http://www.machinedesign.com/industrial-automation/why-do-manufacturing-certifications-matter?NL=MACD-001&Issue=MACD-001_20170523_MACD-001_398&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000005789847&utm_campaign=11223&utm_medium=email&elq2=ac7bbf3354354d12ba54569ff985ae31 When people ask me about ISO 9000, the simple explanation I give, “the process of certification requires you to write down your process and demonstrate that you follow the process.” The certification system does not dictate your process. The mere action of writing down and maintaining the written procedure is the real value. In one of my blogs “Dumbest Guy in the Room", written in two parts, http://www.jagengrg.com/blog, I touch on the value of the written word and the perils of oral communication.  Writing it down allows everyone to see exactly what the author thinks is being done or should be done. Others can read the written word and identify ambiguous sections, missing information, or errors that can easily be overlooked using oral communication. When everyone is carrying the information in their head’s via oral direction I can guarantee there is more than one interpretation. I would venture to say you will have as many interpretations as you have people involved. When written procedures do exist but do not come under the scrutiny of a certification body, it is very common for procedures to become stale, be incomplete, rely on undocumented knowledge, and for steps in the process to be missed from time to time. The subject article closes with a realistic assessment of the value for certification. “Is having a certification the end-all-be-all of manufacturing? No. However….” You reach the "however" stage, not my hanging the certification on the wall, but the process for obtaining it. 
 

The Exponential Age

This came to me via e-mail. I am sure little of this is 100% correct. But just think if just 50% are 50% correct.   The Exponential Age?  Just a few things for us all to ponder, especially the younger ones amongst us.  Did you think back in 1998 that 3 years later you would never take pictures on film again?        In 1998 Kodak had 170,000 employees and sold 85 % photo paper worldwide. Within just a few years their business model disappeared and they went bankrupt. What happened to Kodak will happen in a lot of industries in the next 10 years and, most people  won't see it coming.   Yet digital cameras were invented in 1975. The first ones only had 10,000 pixels, but followed Moore's law.  So as with all exponential technologies, it was a disappointment for a time, before it became way superior and became mainstream in only a few short years. It will now happen  again with Artificial Intelligence, health, autonomous and  electric cars, education, 3D printing, agriculture and jobs.  Welcome to the  4th Industrial Revolution.  Welcome to the Exponential Age.                       Software will disrupt most traditional industries in the next 5-10 years.          Uber is just a software tool, they don't own any cars, and are now the biggest taxi company in the  world.                   Airbnb is now the biggest hotel company in the world, although they don't own any properties.                     Artificial  Intelligence:  Computers become exponentially better in understanding the world. This year, a computer beat the best Go-player in the world, 10 years  earlier than expected.                       In the US , young lawyers already don't get jobs. Because of IBM's Watson you can get legal advice (so far for more or less basic stuff) within seconds. With 90% accuracy compared with 70% accuracy when done by humans.                                  So if you study law, stop  immediately. There will be 90 % less lawyers in the future. Only specialists will remain.              Watson already helps nurses diagnosing cancer,  which is 4 times more accurate than human nurses.             Facebook now has a pattern recognition software that can recognize faces better than humans. In 2030 computers will become more intelligent than humans. (NEVER says Albert)         Autonomous cars: In 2018  the first self driving cars will appear for the public. Around 2020 the complete industry will  start to be disrupted. You won't want to own a car anymore.  You will call a car with your phone, it will show up at your location and drive you to your destination. You will not need to park it, you only pay for the driven distance and can be productive while being driven.                              Our kids will never need to get a  driver's licence and will never own a car.                   It will change the cities,  because we will need 90-95% less cars for that. We can transform former parking spaces into parks.                             1.2  million people die each  year in car accidents worldwide. We now have one accident every 60,000 miles  ( 100,000  km), with autonomous driving that will drop to 1 accident in 6 million miles (10 million km). That will save  a   million  lives each  year.                       Most car companies will probably become bankrupt. Traditional car companies try the evolutionary approach and just build a better car, while tech companies like Tesla, Apple, Google will do the revolutionary approach and build a computer on  wheels.                                  Many engineers from  Volkswagen and Audi are completely terrified of Tesla.                             Insurance  companies  will have massive trouble  because without accidents, the insurance will become 100x cheaper. Their car insurance business model will disappear.                            Real Estate will change.  Because if you can work while you commute, people  will move further away to live in a more beautiful neighbourhood.                                   Electric cars will become  mainstream about 2020.  Cities will be less noisy  because all new cars will run on electricity.                           Electricity will become  incredibly cheap and clean. Solar production has been  on an exponential curve for 30 years, but you can now see the burgeoning impact.                           Last year, more solar energy was installed worldwide than fossil.  Energy companies are desperately trying to limit access to the grid to prevent competition from home solar installations, but that can't last.  Technology will take care of that strategy.                               With cheap electricity comes cheap and abundant water.   Desalination of salt water now only needs 2k Wh per cubic meter at 0.25 cents). We don't have  scarce water in most places, we only have scarce drinking water. Imagine what will be possible if anyone can have as much clean water as he wants, for nearly no cost.                    Health: The Tricorder X price will be announced this year. There are companies who will build a medical device (called the " Tricorder " from Star Trek) that works  with your phone, which takes your retina scan, your blood sample  and you simply  breath into it.                             It then analyses 54 bio-markers  that will identify nearly  any   disease.  It will be cheap, so in a  few years everyone on this planet will have access to world class medical analysis, nearly for free. Goodbye medical  establishments.               3 D printing: The price of the cheapest 3D  printer came down from  $18,000 to $400 within 10 years. In the same time, it  became 100 times faster. All major shoe companies have already started 3D printing  shoes.               Some spare airplane parts  are already 3D printed in remote airports. The space station now has a printer that eliminates the  need for the large amount of spare parts they used to have in the past.                             At the end of this year, new  smartphones will have 3D scanning possibilities. You can then 3D scan your feet and print  your perfect shoe at home.                              In China they have already 3D printed and built a complete 6 storey office building.  By 2027 10% of everything that's being produced will be 3D printed.                                      Business  Opportunities: If you think of a niche you want to go in, first ask yourself, "In the future, do I think we will have that?" If the answer is yes, how can you make that happen sooner? If it doesn't work with your phone, forget the idea.  And any idea designed for success in the 20th century is doomed to failure in the 21st century. Work:   70-80 % of jobs will disappear in the next 20 years. There will be a lot  of new jobs, but it is not clear if there will be enough new  jobs in such a short time.  This will require a rethink on wealth distribution. Agriculture: There will be a $100  agricultural robot in the future.  Farmers in 3rd world countries can then become managers of their field instead of working all day on their  fields.  Aeroponics: Will need much less water. The first Petri dish produced veal, is now available and will be cheaper than cow produced veal in 2018. Right now, 30 % of all agricultural surfaces is used for cows.  Imagine if we don't need that space  anymore. The Times They Are A Changing!
 

Two Balls Rolling On An Incline

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 37
    29 April 2017
Two Balls Rolling On An Incline
A Problem Where I Learned Something New
Introduction     In previous articles, I have mentioned another web site called Physics Forums (PF) where people post problems for which they need help. In this note, I want to present to you one such problem and it solution, along with a new insight that came from another commenter at PF, one of the advisory folk on that site. At first, I thought the adviser was wrong, but it turns out that he was correct and had something new that I had never seen before. Here is the problem. Problem Statement     A thin wall spherical shell with a mass of 0.605 kg and a radius of 0.0402 m is released from rest at the top of an incline. The spherical shell rolls down the incline without slipping. The spherical shell takes 7.49 s to get to the bottom of the incline.
    A solid sphere with mass of 0.127 kg and a radius of 0.1123 m is released from rest at the top of the same incline. The solid sphere rolls down the incline without slipping. How much time does it take for the solid sphere to reach the bottom of the incline.
    Note that ---
Thin spherical shell        I=(2/3)MR^2
Solid sphere        I=(2/5)MR^2 Discussion     The original problem statement is above. Note what is given, and perhaps more importantly, what is not given. In particular, we are not given 1.The time for the solid sphere to reach the bottom -- this is the item to be determined;
2.The angle of the incline;
3.The length of the incline;
4.The local value of g, the acceleration of gravity.     The last three items are things that we might expect to have given in such a problem, but here they are not. This is the major difficulty in this problem, and the solution must find a way to work around this missing information. TwoBallsRollingOnAnIncline.pdf

DrD

DrD

 

Difference between refrigeration and air conditioning

what is the difference between refrigeration and air conditioning? A major difference between refrigeration and air conditioning is the point of supply for the gases. Refrigeration systems have gas installed in a series of tubes. In old refrigerators, this gas was chloro-flouro-carbon, or CFC, but this has harmful effects on people, so refrigerators not contain HFC-134a. HFC-134a is the sole gas used as a coolant in refrigeration systems. Air conditioning systems use built-in chemicals, but also air from the room or rooms being heated. Gases built into air conditioning units cool air that circulates through the unit; the unit then redistributes the cooled air through the room. Air conditioners have circulation systems designed to project cool air away from the units while refrigeration units have circulation systems designed to retain coolant in a confined space. Refrigeration systems circulate cool liquids and gases through a series of tubes and vents. Cool air from within a refrigerator is sucked into a compressor that recycles the gas through the tubes. Air conditioners, while also employing tubes in the coolant system, have fans for the dispersal of air. Unlike refrigeration systems, which keep gases contained to a pre-determined space, air conditioning systems disperse cool air throughout areas of unknown volume. Refrigeration refers to processes that take thermal energy away from a place and gives off that energy to a place with a higher temperature. Naturally, thermal energy flows from a place with a higher temperature to a place with a lower temperature. Therefore, refrigeration runs against the natural heat flow and so it requires work to be done.Refrigerator is a name that we use for devices that are used to keep food at low temperatures. A refrigerator consists of a fluid called refrigerantwhich gets expanded and compressed in a cycle:  

AFZALKHAN

AFZALKHAN

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