PROJECT REPORT ONICE CUBE MAKING MACHINESubmitted in partial fulfillment for the award of the Degree of BACHELOR OF ENGINEERING INMECHANICAL ENGINEERINGBYSAGAR REVALESURESH CHOUDHARYRISHITOSH BHANDARYROSHVEL BARRETTO NIPUN BHATIA

UNDER THE GUIDANCE OF Prof Mrs K.H DHANAVDE

LOKMANYA TILAK COLLEGE OF ENGINEERINGKOPARKHAIRANE NAVI MUMBAI 400 709UNIVERSITY OF MUMBAI 2014-15ICE CUBE MAKING MACHINEDissertationSubmitted by SAGAR REVALESURESH CHOUDHARYROSHVEL BARRETTONIPUN BHATIARISHITOSH BHANDARYIn partial fulfillment for the award of the Degree of BACHELOR OF ENGINEERING IN MECHANICAL ENGINEERINGUnder the guidance of Prof Mrs K.H DHANAVDELOKMANYA TILAK COLLEGE OF ENGINEERING,NAVI MUMBAI

DEPARTMENT OF MECHANICAL ENGINEERING LOKMANYA TILAK COLLEGE OF ENGINEERINGKOPARKHAIRANE, NAVI MUMBAIMAHARASHTRA, INDIA 400709 2014-15

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This is to certify that the project report on, ........... submitted by ........, Bachelor of Engineering student of Lokmanya Tilak College Of Engineering, Navi Mumbai, towards partial fulfillment of the requirements for the award of the Degree of Bachelor of Engineering in Mechanical Engineering as prescribed by the University Of Mumbai, is a bona fide record of the work carried out by him under my supervision and guidance. The matter contained in this dissertation has not been submitted to any other University for award of any Degree or Diploma.

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APPROVAL OF PROJECT REPORTThis is to certify that the thesis entitled project title, submitted by student name in partial fulfillment of the requirements for the award of the Degree of Bachelor of Engineering in Mechanical Engineering , as prescribed by University Of Mumbai is approved.

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ICE CUBE MAKING MACHINE

INTRODUCTIONS:Ice cube makers use more water than just the water contained in the ice. This equipment can often be very inefficient in water use. The typical icemaker uses 2 or 3 times more water than needed to make the ice we consume. These water using machines can be found everywhere; hospitals account for 39.4 percent of all commercial ice-maker purchases, followed by hotels (22.3 percent), restaurants (13.8 percent), retail outlets (8.5 percent), schools (8.5 percent), offices (4.3 percent) and grocery stores (3.2 percent).There are two basic equipment designs: air-cooled refrigeration units and water cooled refrigeration units. The air-cooled units are usually more water efficient; while the water cooled units are usually more energy efficient. Both types vary greatly in water efficiency, even within its own design type. The water efficiency is measured by the industry in gallons of water per 100 lbs (45.36 kg) of ice. Perfect water efficiency would equate to 11.97 gallons (45.3 L) of water to produce 100 lbs (45.36kg)of ice. Most ice makers water use ranges between 18 to 200 gallons (68 L to 756.9 L) of water per 100 lbs (45.36 kg) of ice. This represents a water efficiency range of 66% to only 5%. Thus, 34% to 95% of the water used is dumped down the drain. The water varies for several reasons.As the ice is formed in the freezing trays, minerals in the water collect in the equipment. These minerals must be occasionally rinsed off the freezing trays and the water reservoirs. Ice makers have a variable setting to initiate a rinse cycle at desired frequencies. The frequency of rinse is to be determined by local water quality and site requirements. Some new model actuate the rinse cycles based on sensor readings of minerals. Often the ice maker is set to rinse more often than necessary, resulting in water waste.The quality of the ice can also affect water use. Some ice makers are designed to produce clearer and smoother ice by using a repeated freezing and partial thawing cycle while the ice is produced. This results in ice cubes that are smoother, without air bubbles and more crystalline like. Unfortunately, this aesthetic quality wastes a lot of water and serves no useful purpose; frosty ice cools just as well as clear ice.Water cooled ice makers are often the most inefficient in water use, although sometimes providing significant energy savings at the point of use. Itis important to note that there are many air-cooled ice machinesmoreenergy efficient than some water-cooled ice machines.Water cooled machines generally use potable water to remove heat from the refrigeration equipment. In years past, most of these machines used single-pass cooling dumping the water into the sewer as it exited the machine.Fortunately, many manufacturers are started to abandon thiswasteful design. Some newer designs re-circulate the water after it passes through a cooling tower or heat exchanger, but these still require large amounts of make up water. While air-cooled machines generally have a water efficiency of 40% to 66%, water cooled machines are usually less than 15% water efficient.

Problem Statement:Nickel- or tin-plated copper is most commonly used for the ice forming pockets in cube ice machines today. Such pockets may be formed by fitting notched strips of copper together in an "egg crate" relationship to form a grid of four sided pockets. The strips are then soldered to a backing pan. At the same time a serpentine piece of copper tubing (forming the evaporator section of the refrigeration system) can be soldered to the back of the pan. The entire evaporator/ice forming assembly is then nickel or tin plated. The plating is required by National Sanitation Foundation (NSF) codes, which prohibit the use of copper parts in contact with food products.While plated copper assemblies work well in cube ice machines, they have several drawbacks. One of the primary problems is that the plating operation itself is costly, and typically produces sludge that is costly to dispose of in an environmentally safe manner. Also, copper is relatively expensive. Further, though it has very good heat conduction properties, copper is dense, so that it has a high heat capacity per unit volume. The duration of the production/harvest cycle is thus longer than desired because, at each change in the cycle, the copper ice forming pockets have to be either heated or cooled.Another disadvantage of assemblies made from bonded parts, including plated copper assemblies, is that structures made from bonding different parts together usually suffer a heat transfer impediment. Usually, two elements may not be perfectly joined because the elements are not perfectly flat or otherwise matched in profile, and the presence of dust particles or oxides may cause surface irregularities decreasing thermal conduction at those locations. Further, because air has poor conducting properties, the presence of air pockets in two bonded elements may also reduce thermal conduction.In attempting to overcome these disadvantages, a cast aluminum grid was experimented with. Cast aluminum was found to present several drawbacks. Primarily, even though the ice cube pockets could easily be formed in the casting, the evaporator system tubing had to be attached after the casting operation. This proved to be unworkable because the cast aluminum was so porous that the tubing could not suitably be brazed to the casting

VAPOUR COMPRESSION REFRIGERATION CYCLE: Most of the modern refrigerators work on this cycle. In its simplest form there are four fundamental operations require to complete one cycle. Compression Condensation Expansion Vaporization

Compression: The low pressure vapors in dry state are drawn from the evaporator during the suction stroke of the compressor. During Compression stroke the pressure and temperature increase until vapour temperature is greater than the temperature of condenser cooling medium.

Condensation : When the high pressure refrigerant vapour enters the condenser heat flows from condenser to cooling medium thus allowing the vapourized refrigerant to return to liquid state.

Expansion : After condenser the liquid refrigerant is stored in the liquid receiver until needed. From the receiver it passes through an expansion valve where the pressure is reduced sufficiently to allow the vapourization of liquid a low temperature of about -10C.

Vaporization : The low pressure refrigerant vapour after expansion in the expansion valve enters the evaporator or refrigerated space where a considerable amount of heat is absorbed by it and refrigeration is furnished.

Vapour-compression cycle for Refrigeration system

Vapour-compression cycle with T-S Diagram & P-V Diagram

Components of Compression cycle requires four components :The vapour compression cycle requires four components : Compressor : To raise the pressure of low-pressure low temperature gas to high-pressure high temperature gas. The Condenser : To change the state of high-pressure, high temperature gas to high-pressure, high temperature LIQUID. This is achieved by passing ambient air (known as air-cooled) or water (known as water-cooled) over the condenser tubes. The Expansion Device : The purpose of the device is to change the state of the refrigerant from high-pressure, high temperature liquid to low pressure low temperature saturated liquid. This is achieved by passing the liquid through an orifice. The Evaporator : To absorb the heat from room air or water, which in the case of a chiller is circulated around the evaporator coil. This will change the state of low-pressure, low temperature saturated liquid to low pressure, low/medium temperature gas .

COMPRESSORSIntoduction : A refrigerator compressor is the center of the refrigerator cycle . Compressor may be called as a heart of any vapour compression system . It works as a pump to control the circulation of the refrigerant, and it adds pressure to the refrigerant, heating it up . The compressor also draws vapour away from the evaporator to maintain a lower pressure and lower temperature before sending it to the condenser.

CLASSIFICATION OF COMPRESSORS :According to the method of compression : Reciprocating compressors Rotary compressors Centrifugal compressors

HERMATICALLY SEALED :A small hermatically sealed compressor in a common consumer refrigerator or freezer; it typically has a rounded steel outer shell that is permanentaly welded shut, and which seals operating gases inside the system. There is no route for gases to leak, such as around motor shaft seals. On this model, the plastic top section is part of an auto-defrost system which uses motor heat to evaporate the water. Compressers are often described as being either open , hermatic, or semi-hermatic, to describe how the compressor and motor drive is situated in relation to the gas or vapour being compressed. The industry name for hermatic is hermatically sealed compressor, while a semi- is commonly called a semi-hermatic compressor. In hermatic and most semi-hermatic compressors, the compressor and motor driving the compressor are integrated, and operate within the pressurized gas envelope of the system. The motor is designed to operate and be cooled by the gas or vapour being compressed. The difference between the hermatic and semi-hermatic, is that the hermatic uses a one-piece welded steel casing that cannot be opened for repair; if the hermatic fails it is simply replaced with an entire new unit . A semi-hermatic uses a large cast metal shell with gasketed covers that can be opened to replace motor and pump components. The primary advantage of a hermatic and semi-hermatic is that there is no route for the gas to leak out of the system. Open compresser rely on either natural leather or synthetic rubber seals to retain the internal pressure, and these seals require a lubricant such as oil to retain their sealing properties. An open pressurized system such as an automobile air conditioner can leak its operating gases, if it is not operated frequently enough. Open systems rely on lubricant in the system to splash on pump components and seals. If it is not operated frequently enough, the lubricant on the seals slowly evaporates, and the seals begin to leak until the system is no longer functional and must be recharged. By comparison, a hermatic system can sit unused for years, and can usually be started up again at any time without requiring maintenance or experiencing any loss of system pressure.The disadvantage of hermatic compressors is that the motor drive cannot be repair or maintained, and the entire compressor must be removed if a motor fails. A further disadvantage is that burnt out windings can contaminate whole systems requiring the system to be entirely pumped down and the gas replaced. Typically hermatic compressors are used in low-cost factory-assembled consumer goods where the cost of repair is high compared to the value of the device , and it would be more economical to just purchase a new device.An advantage of open compressors is that they can be driven by non-electric power sources, such as an internal combustion engine or turbine. However, open compressors that drive refrigeration systems are generally not totally maintenance free throughout the life of the system, since some gas leakage will occur over time.

Compressor Lubrication In order to lubricate the moving parts of the compressor, an oil is added to the refrigerant during installation or commissioning. The type of oil may be mineral or synthetic to suit the compressor type, and also chosen so as not to react with the refrigerant type and other components in the system. In small refrigeration systems the oil is allowed to circulate throughout the whole circuit, but care must be taken to design the pipework and components such that oil can drain back under gravity to the compressor. In larger more distributed systems, especially in retail refrigeration, the oil is normally captured at an oil separator immediately after the compressor, and is in turn redelivered, by an oil level management system, back to the compressor(s). Oil separators are not 100% efficient so system pipework must still be designed so that oil can drain back by gravity to oil separator or compressor.Some newer compressor technologies use magnetic bearings and require no lubrication, for example the Danfoss Turbocor range of centrifugal compressors. Avoiding the need for oil lubrication and the design requirements and ancillaries associated with it, simplifies the design of the refrigerant system and reduces maintenance requirements.

APPLICATION: Refrigerators Deep freezer Water cooler Bottle coolers Room air conditioners

CONDENSOR

Introductions :Condensors and evaporators are basically heat exchangers in which the refrigerant undergoes a phase change. Next to compressors, proper design and selection of condensers and evaporators is very important for satisfactory performance of any refrigeration system. Since both condensers and evaporators are essentially heat exchangers, they have many things in common as far as the design of these components is concerned. In condensers the refrigerant vapour condenses by rejecting heat to an external fluid, which acts as a heat sink. Normally, the external fluid does not undergo any phase change, except in some special cases such as in cascade condensers, where the external fluid (another refrigerant) evaporates. In evaporators, the liquid refrigerant evaporates by extracting heat from an external fluid (low temperature heat source). The external fluid may not undergo phase change, for example if the system is used forsensibly cooling water, air or some other fluid. There are many refrigeration and air conditioning applications, where the external fluid also undergoes phase change. For example, in typical summer air conditioning system, the moist air is dehimidised by condensing water vapour and then, removing the condensed liquid water. In many low temperature refrigeration applications freezing or frosting of evaporators takes place. These aspects have to be considered while designing condensers and evaporators.

Classification of condensers:Condensers may be classified on the following basis: On the basis of cooling medium used:(a) Air cooled condenser(b) Water cooled condenser(c) Evaporative condenser

On the basis of construction:(a) Shell type condenser(b) Shell and coil condenser(c) Double pipe condenser(d) Finned condenser

Purpose of a Condenser:The purpose of a condenser in the cycle of compression refrigeration is to change the hot gas being discharged from the compressor to a liquid prepared for use in the evaporator. The condenser accomplishes this action by the removal of sufficient heat from the hot gas, to ensure its condensation at the pressure available in the condenser. The heat is shifted to another medium, like water or air, to cool the condenser.

AIR COOLED FIN TYPE CONDENSER

Air-cooled finned condenser is widely used in refrigeration and air conditioning application. For same amount of heat transfer, the operation of air cooled condenser is more economic as compared with water cooled condenser typically air cooled condenser are of the round tube and fin type. To improve the performance of air cooled condensers multiple techniques can be achieved such as enhancement on inner pipe surface, changing the tube geometry from round to flat shape and external fins. A micro-channel flat tubes that heat exchanger is one of the potential alternatives for replacing the conventional finned tube heat exchanger. This kind of heat exchanger is made of a flat tube with several independent passages in the cross section and formed into a serpentine or a parallel flow arrangement. In these heat exchangers, a multitude of corogated fins with louvers are inserted into the gaps between the flat tubes. The flat tube design offers higher thermal performance and lower pressure drop then the finned round heat exchangers.

EXPANSION DEVICES Introduction: An expansion device is another basic component of a refrigeration system. The basic functions of an expansion device used in refrigeration system are to:1. Reduce pressure from condenser pressure to evaporator pressure, and2. Regulate the refrigerant flow from the high-pressure liquid line into the evaporator at a rate equal to the evaporation rate In the evaporator.

The expansion devices used in rerfrigeration system can be divided into fixed opening type or variable opening type. As the name implies, in fixed opening type in the flow area changes with changing mass flow rates. There are basically seven types of refrigerant expansion devices. These are:1. Hand (manual) expansion valves 2. Capillary Tubes 3. Orifice 4. Constant pressure or Automatic Expansion Valve (AEV)5. Thermostatic Expansion Valve 6. Float type Expansion Valvea) High Side Float Valveb) Low Side Float Valve7. Electronic Expansion Valve

Capillary Tube:A capillry tube is long narrow tube of constant diameter. The word capillry is a misnomer since surface tension is not important in refrigeration application of capillary tubes. Typical tube diameters of refrigerab=nt capillary tubes range from 0.5mm to 3 mm and the length ranges from 1.0m to 6m. The pressure reduction in capillary tube occurs due to the following two factors:1. The refrigerant has to overcome the frictinal resistance offered by the walls. This leads to some pressure drop, and2. The liquid refrigerant flashes (evaporates) into mixture of liquid and vapours its pressure reduces. The density of vapour is less than that of the liquid. Hence, the average density of refrigerant decreases as it flows in the tube. The mass flow rate and the tube diameter (hence area) being constant, the velocity of refrigerant increases since. The increse in velocity or acceleration of the refrigerant also requires pressure drop. Several combinations of length and bore are available for the same mass flow rate and pressure drop. However, once a capillary tube of some diameter and length has been installed in a refrigeratin system, the mass flow rate through it will vary in such a manner that the total pressure drop through it matches with the pressure difference between condenser and the evaporator. Its mass flow rate is totally dependent upon the pressure difference across it; it cannot adjust itself to variation of load effectively.

Selection of Capillary Tube: For any new system, the diameter and the lenghth of capillary tube have to be selected by the designer such that the compressor and the capillary tube achieve the balanced point at the desired evaporator temperature. There are analytical and graphical methods to select the capillary tube. The fine-tuning of the length is finally done by cut-andtry method. Atube longer than the design (calculated) vaue is installed with the expected result that evaporating temperature will be lower than expected. The tube is shortened until the desired balance point is achieved. This is done for mass production. If a single system is to be designed then tube of slightly shorter length than the design length is chosen. The tube will usually result in higher temperature than the design value. The tube is pinched at a few apots to obtain the required pressure and temperature.

Advantages and disadvantages of capillary tube: Some of the advantages of a capillary tube are:1. It is Inexpensive.2. It does not have any moving parts hence it does not require maintenance.3. Capillary tube provides an open connection between condenser and the evaporator hence during off-cycle, pressure equalization occurs between condenser ans evaporator. This reduces the starting torque requirement of the motor starts with same pressure on the two sides of the compressor. Hence, a motor with low starting torque (squirrel cage Induction motor) can be used.4. Ideal for hermatic compressor based systems, which are critically charged and factory assembled.Some of the disadvantages of the capillary tube are:1. It cannot adjust itself to changing flow conditions in response to daily and seasonal variation in ambient temperature and load. Hence , COP is usually low under off design conditions.2. It is susceptible to clogging because of narrow bore of the tube, hence, utmost care is required at the time of asembly. A filter-drier should be used ahead of the capillary to prevent entry of moisture or any solid particles.3. During off-cycle liquid refrigerant flows to evaporator because of pressure difference between condenser and evaporator. The evaporator may get flooded and refrigerant may flow to compressor and damage it when starts.Therefore critical charge is used in capillary tube based compressor systems. Further, it is used only with hermatically sealed compressors where refrigerant does not leak so that critical charge can be used. Normally an accumulator is provided after the evaporator to prevant slugging of compressor.

EVAPORATORSIntroductions:An evaporators, like condenser is also a heat exchanger. In an evaporator, the refrigerant boils or evaporates and in doing so absorb heat from the substance being refrigerated. The name evaporator refers to the evaporation process occuring in the heat exchanger.Copper Condenser CoilsThe most common use of copper alloy tube bundles are for condensers and auxiliary heat exchangers. If you need to turn steam into water minimal back flow and high efficiency, then copper tubing is one of your best bets.Reaching your particular fluids dew point is not hard with copper and a moderate amount of air moving over the coil. Coppers high thermal transfer rate makes it ideal for condensing operations.Copper Evaporator CoilsWhen intense heat is required for your application or pressurized fittings are needed. CTCG has you covered! Our end tube manipulation services allows you to customize your any way you want. Cannot find the end fixture you need? We can buil it in house for you.When pressurized gas is depressurized at the expansion valve, it becomes far cooler than it was before. In other words, as pressurized gas is able to expand in an evaporator coil, its temperature decreases and it becomes a colling agent. Usually, this process is used either to cool the air outside the coil or to turn a pressurized or liquid medium into gas. Refrigeration technician choose copper because of its thermal conductivity, which is eight times greater than aluminium tube. The lightweight and durable properties of copper make it easy to work with during and after installation. Coppers long life span and resistance to corrosion make it a maintenance free choice that will likely last the lifetime of the building.Removing heat is a process greately helped by coppers highly heat sensitive nature. Using tubing with fluid is a very efficient way to transfer haet, and can be utilized in diverse ways to accommodate your projects needs.Unlike other industries, copper tubes used for air conditioning and refrigeration purposes are designated by their outside diameter. Other industries use the inside diameter of the tube.

REFRIGERANTSA refrigerants is a substance used in heat cycle usually including, for enhanced efficiency, a reversible phase change from a liquid to a gas.Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as refrigerants, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various applications are ammonia, sulphur dioxide, and non- halogenated hydrocarbons such as methane.

Introductions: The thermodynamic efficiency of a refrigeration system depends mainly on its operating temperatures. However, important practical issues such as the system design, size, initial and operating costs, safety, reliability, and servicebility etc. depend very much on the type of refrigerant selected for a given application. Due to several envirnment issues such as ozone layer depletion and global warming and their relation to the various refrigerants used, the selection of suitable refrigerant by a completely new refrigerant, for whatever reason, is an expensive proposition as it may call for several changes in the design and manufacturing of refrigeration system. Hence it is very important to understand the issues related to the selection and use of refrigerants. In principle, any fluid can be used as a refrigerant. Air used in an air cycle refrigeration system can also be considered as a refrigerant. However, in this lecture the attention is mainly focused on those fluids that can be used as refrigerants in vapour compression refrigeration systems only.

Physical properties:The ideal refrigerant has a favorable thermodynamic properties, is unrective chemically, and is safe. The desired thermodynamic properties are boiling point somewhat below the target temperature, a high heat of vaporization, a moderate density in liquid form, a relatively high density in gaseous form, and a high critical temperature. Since boiling point and gas density are affected by pressure, refrigerants may be made more suitable for a particular application by choice of operating pressure. These properties are ideally met by the chlorofluorocarbons, but environmental science regards stability as being an undesirable property of a refrigerant, leading to recommendations such as Supercritical carbon dioxide as a possible future cooling agent for use in vehicles.Corrosion properties are a matter of materials compatibility with the mechanical components: compressor, piping, evaporator, and condenser. Safety considerations include toxicity and flammability.

Primary and Secondary refrigerants:Fluids suitable for refrigeration purposes can be classified into primary and secondary refrigerants. Primary refrigerants are those fluids, which are used directly as working fluids, for example in vapour compression and vapour absorption refrigeration systems. When used in compresson or absorption systems, these fluids provide refrigeration by undergoing a phase change process in the evaporator. As the name implies, secondary refrigerants are those liquids, which are used for transporting thermal energy from one location to other. Secondary refrigerants are also known under the name brines or antifreezes. Of course, if the oprating temperatures are above 0oc, then pure water can also be used as secondary refrigerant, for example in large air conditioning systems. Antifreezes or brines are used when refrigerantion is required at sub-zero temperatuers. Unlike primary refrigerants, the secondary refrigerants do not undergo phase change as they transport energy from one location to other.

Refrigerant selection criteria:Selection of refrigerant for a particular application is based on the following requirements:i. Thermodynamic and thermo-physical propertiesii. Enviromental and safety properties, and iii. Economics

Refrigerant R-134a:

Refrigerant R134a is a hydrofluorocarbon (HFC) that has zero potential to cause the depletion of the ozone layer and very little greenhouse effect. Let us see the various properties of this refrigerant and how it replaces R12.Refrigerant R134aThe refrigerant R134a is the chemical compound tetrafluoroethane comprising of two atoms of carbon, two atoms of hydrogen and four atoms of fluorine. Its chemical formula is CF3CH2F. The molecular weight of refrigerant R134a is 133.4 and its boiling point is -15.1 degree F.Refrigerant R134a is a hydrofluorocarbon (HFC) that has zero potential to cause the depletion of the ozone layer and very little greenhouse effect. R134a is the nonflammable and non-explosive, has toxicity within limits and good chemical stability. It has somewhat high affinity for the moisture. The overall physical and thermodynamic properties of refrigerant R134a closely resemble with that of refrigerant R12. Due to all the above factors, R134a is considered to be an excellent replacement for R12 refrigeran

INSULATIONInsulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature. The means to stem heat flow may be especially engineered methods or processes, as well as suitable static objects and materials.

Purpose of Insulation:A thermal insulator is a poor conductor of heat and has a low conductivity. Insulation is used in buildings and in manufacturing processes to prevent heat loss or heat gain. Although its primary purpose is an economic one, it also provides more accurate control of process temperatures and protection of personnel. It prevents condensation on cold surfaces and the resulting corrosion. Such materials are porous, containing large number of dormant air cells. Thermal insulation delivers the following benefits: Reduces over-all energy consumption. Offers better process control by maintaining process temperature. Prevents corrosion by keeping the exposed surface of a refrigerated system above dew point. Provides fire protection to equipment. Absorbs vibration.

Insulation material:Insulation materials can also be classified into organic and inorganic types.Inorganic insulation is based on Siliceous/Aluminous/Calcium materials in fiberous, granular or powder forms. Example: Mineral wool, Calcium silicate etc.Organic insulations are based on the hyocarbon polymers, which can be expanded to obtain hogh void structures. Example Thermocol (Expanded Polystyrene) and Poly Urethane Foam (PUF).Puf stands for poly Urethene Foam. Polyurethane (PUF) is used extensively in applications of lower temperatures.

BRAZINGBrazing is metal-joining process whereby a filler metal is heated above melting point and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquids) temperature while protected bya suitable atmosphere, usually a flux. It then flows over the base metal (known as wetting) and is then cooled to join the work pieces together. It is similar to soldering, except the temperatures used to melt the filler metal are higher.

Fundamentals:In order to obtain high-quality brazed joints, parts must be closely fitted, and the base metals must be exceptionally clean and free of oxides. In most cases, joint clearances of 0.03 to 0.08mm (0.0012 to 0.0031in) are recommended for the bestcapillary actionand joint strength.However, in some brazing operations it is not uncommon to have joint clearances around 0.6mm (0.024in). Cleanliness of the brazing surfaces is also important, as any contamination can cause poor wetting (flow). The two main methods for cleaning parts, prior to brazing, are chemical cleaning and abrasive or mechanical cleaning. In the case of mechanical cleaning, it is important to maintain the proper surface roughness as wetting on a rough surface occurs much more readily than on a smooth surface of the same geometry.Another consideration that cannot be overlooked is the effect of temperature and time on the quality of brazed joints. As the temperature of the braze alloy is increased, the alloying and wetting action of the filler metal increases as well. In general, the brazing temperature selected must be above the melting point of the filler metal. However, there are several factors that influence the joint designer's temperature selection. The best temperature is usually selected so as to: (1) be the lowest possible braze temperature, (2) minimize any heat effects on the assembly, (3) keep filler metal/base metal interactions to a minimum, and (4) maximize the life of any fixtures or jigs used.In some cases, a higher temperature may be selected to allow for other factors in the design (e.g. to allow use of a different filler metal, or to control metallurgical effects, or to sufficiently remove surface contamination). The effect of time on the brazed joint primarily affects the extent to which the aforementioned effects are present; however, in general most production processes are selected to minimize brazing time and the associated costs. This is not always the case, however, since in some non-production settings, time and cost are secondary to other joint attributes (e.g. strength, appearance).

Torch brazingTorchbrazing is by far the most common method of mechanized brazing in use. It is best used in small production volumes or in specialized operations, and in some countries, it accounts for a majority of the brazing taking place. There are three main categories of torch brazing in use:manual, machine, and automatic torch brazing.Manual torch brazingis a procedure where the heat is applied using a gas flame placed on or near the joint being brazed. The torch can either be hand held or held in a fixed position depending on whether the operation is completely manual or has some level of automation. Manual brazing is most commonly used on small production volumes or in applications where the part size or configuration makes other brazing methods impossible.The main drawback is the high labor cost associated with the method as well as the operator skill required to obtain quality brazed joints. The use of flux or self-fluxing material is required to prevent oxidation. Torch brazing of copper can be done without the use of flux if it is brazed with a torch using oxygen and hydrogen gas, rather than oxygen and other flammable gases.Machine torch brazingis commonly used where a repetitive braze operation is being carried out. This method is a mix of both automated and manual operations with an operator often placing brazes material, flux and jigging parts while the machine mechanism carries out the actual braze.The advantage of this method is that it reduces the high labor and skill requirement of manual brazing. The use of flux is also required for this method as there is no protective atmosphere, and it is best suited to small to medium production volumes.Automatic torch brazingis a method that almost eliminates the need for manual labor in the brazing operation, except for loading and unloading of the machine. The main advantages of this method are: a high production rate, uniform braze quality, and reduced operating cost. The equipment used is essentially the same as that used for Machine torch brazing, with the main difference being that the machinery replaces the operator in the part preparation.

ELECTRIC MOTORAn electric motor is an electromechanical device that converts electrical energy to mechanical energy. In normal motoring mode, most electric motors operate through the interaction between an electric motor'smagnetic fieldandwinding currentsto generate force within the motor. In certain applications, such as in the transportation industry withtraction motors, electric motors can operate in both motoring andgenerating or brakingmodes to also produce electrical energy from mechanical energy.Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered bydirect current (DC)sources, such as from batteries, motor vehicles or rectifiers, or byalternating current (AC)sources, such as from the power grid,invertersor generators. Small motors may be found in electric watches. General-purpose motors with highly standardized dimensions and characteristics provide convenient mechanical power for industrial use. The largest of electric motors are used for ship propulsion, pipeline compression andpumped-storageapplications with ratings reaching 100 megawatts. Electric motors may be classified by electric power source type, internal construction, application, type of motion output, and so on.Electric motors are used to produce linear or rotary force (torque), and should be distinguished from devices such as magnetic solenoids and loudspeakers that convert electricity into motion but do not generate usable mechanical powers, which are respectively referred to as actuators and transducers.

Parts of an Electric Motor:

RotorIn an electric motor the moving part is the rotor which turns the shaft to deliver the mechanical power. The rotor usually has conductors laid into it which carry currents that interact with the magnetic field of the stator to generate the forces that turn the shaft. However, some rotors carry permanent magnets, and the stator holds the conductors.

StatorThe stationary part is the stator, usually has either windings or permanent magnets. The stator is the stationary part of the motors electromagnetic circuit. The stator core is made up of many thin metal sheets, called laminations. Laminations are used to reduce energy losses that would result if a solid core were used.

Air gapIn between the rotor and stator is the air gap. The air gap has important effects, and is generally as small as possible, as a large gap has a strong negative effect on the performance of an electric motor.

Windings Windings are wires that are laid in coils, usually wrapped around a laminated soft ironmagnetic coreso as to form magnetic poles when energized with current.Electric machines come in two basic magnet field pole configurations:salient-polemachine andnonsalient-polemachine. In the salient-pole machine the pole's magnetic field is produced by a winding wound around the pole below the pole face. In thenonsalient-pole, or distributed field, or round-rotor, machine, the winding is distributed in pole face slots.Ashaded-pole motorhas a winding around part of the pole that delays the phase of the magnetic field for that pole.Some motors have conductors which consist of thicker metal, such as bars or sheets of metal, usuallycopper, although sometimesaluminumis used. These are usually powered byelectromagnetic induction.

CommutatorAcommutatoris a mechanism used toswitchthe input of most DC machines and certain AC machines consisting of slip ring segments insulated from each other and from the electric motor's shaft. The motor's armature current is supplied through the stationarybrushesin contact with the revolving commutator, which causes required current reversal and applies power to the machine in an optimal manner as therotorrotates from pole to pole.In absence of such current reversal, the motor would brake to a stop. In light of significant advances in the past few decades due to improved technologies in electronic controller, sensorless control, induction motor, and permanent magnet motor fields, electromechanically commutated motors are increasingly being displaced by externally commutated induction andpermanent-magnet motors.

WELDING

Weldingis afabricationorsculpturalprocessthat joins materials, usuallymetalsorthermoplastics, by causingcoalescence. This is often done bymeltingthe workpieces and adding a filler material to form a pool of molten material (theweld pool) that cools to become a strong joint, withpressuresometimes used in conjunction withheat, or by itself, to produce the weld. This is in contrast withsolderingandbrazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them, without melting the work pieces. It is often used in construction engineering.Many differentenergy sourcescan be used for welding, including a gasflame, anelectric arc, alaser, anelectron beam,friction, andultrasound. While often an industrial process, welding may be performed in many different environments, including in open air,under water, and inouter space. Welding is a hazardous undertaking and precautions are required to avoidburns,electric shock, vision damage, inhalation of poisonous gases and fumes, and exposure tointense ultraviolet radiation.Until the end of the 19th century, the only welding process wasforge welding, whichblacksmithshad used for centuries to join iron and steel by heating and hammering.Arc weldingandoxyfuel weldingwere among the first processes to develop late in the century, andelectric resistance weldingfollowed soon after. Welding technology advanced quickly during the early 20th century as World War I and World War II drove the demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including manual methods like SMAW, now one of the most popular welding methods, as well as semi-automatic and automatic processes such as GMAW, SAW, FCAW and ESW. Developments continued with the invention oflaser beam welding, electron beam welding,magnetic pulse welding(MPW), andfriction stir weldingin the latter half of the century. Today, the science continues to advance.Robot weldingis commonplace in industrial settings, and researchers continue to develop new welding methods and gain greater understanding of weld quality.

CORE WIREAwireis a single, usuallycylindrical, flexible strand or rod of metal. Wires are used to bear mechanicalloads orelectricityand telecommunications signals. Wire is commonly formed bydrawingthe metal through a hole in adieordraw plate.Wire gaugescome in variousstandardsizes, as expressed in terms of agauge number. The termwireis also used more loosely to refer to a bundle of such strands, as in 'multistranded wire', which is more correctly termed awire ropein mechanics, or acablein electricity.Wire comes in solid core, stranded, or braided forms. Although usually circular in cross-section, wire can be made in square, hexagonal, flattened rectangular, or other cross-sections, either for decorative purposes, or for technical purposes such as high-efficiencyvoice coils inloudspeakers. Edge-wound coil springs, such as theSlinkytoy, are made of special flattened wire.

Uses:Wire has many uses. It forms the raw material of many importantmanufacturers, such as thewire nettingindustry, engineered springs,wire-clothmaking andwire ropespinning, in which it occupies a place analogous to atextilefiber. Wire-cloth of all degrees of strength and fineness of mesh is used for sifting and screening machinery, for draining paper pulp, for window screens, and for many other purposes. Vast quantities ofaluminium,copper,nickelandsteelwire are employed for telephone anddata cables, and as conductors inelectric power transmission, andheating. It is in no less demand for fencing, and much is consumed in the construction ofsuspension bridges, and cages, etc. In the manufacture of stringed musical instruments and scientific instruments wire is again largely used. Carbon and stainless spring steel wire have significant applications for engineered springs for critical automotive or industrial manufactured parts/components. Among its other sources of consumption it is sufficient to mention pin andhairpinmaking, the needle andfish-hookindustries, nail, peg and rivet making, and carding machinery; indeed there are few industries into which it does not enter.Not all metals and metallicalloyspossess the physical properties necessary to make useful wire. The metals must in the first place beductileand strong in tension, the quality on which the utility of wire principally depends. The metals suitable for wire, possessing almost equal ductility, areplatinum,silver,iron,copper, aluminium andgold; and it is only from these and certain of theiralloyswith other metals, principallybrassandbronze, that wire is prepared (For a detailed discussion oncopper wire, see main article:Copper wire and cable.).By careful treatment extremely thin wire can be produced. Special purpose wire is however made from other metals (e.g.tungstenwire forlight bulbandvacuum tubefilaments, because of its high melting temperature). Copper wires are also plated with other metals, such as tin, nickel, and silver to handle different temperatures, provide lubrication, provide easier stripping of rubber from copper.

INNOVATIONS:

WORKING PRINCIPLE:

In this system, the metal ice tray is connected to a set of coiledheat-exchanging pipeslike the ones on the back of your refrigerator. If you've readHow Refrigerators Work, then you know how these pipes work. A compressor drives a stream of refrigerant fluid in a continuous cycle of condensation and expansion. Basically, the compressor forces refrigerant through a narrow tube (called thecondenser) to condense it, and then releases it into a wider tube (called theevaporator), where it can expand.Compressing the refrigerant raises its pressure, which increases its temperature. As the refrigerant passes through the narrow condenser coils, it loses heat to the cooler air outside, and itcondensesinto a liquid. When the compressed fluid passes through theexpansion valve, it evaporates -- it expands to become a gas. This evaporation process draws in heat energy from the metal pipes and the air around the refrigerant. This cools the pipes and the attached metal ice tray.The icemaker has a water pump, which draws water from acollection sumpand pours it over the chilled ice tray. As the water flows over the tray, it gradually freezes, building up ice cubes in the well of the tray. When you freeze water layer by layer this way, it forms clear ice. When you freeze it all at once, as in the home icemaker, you get cloudy ice . After a set amount of time, the icemaker triggers asolenoid valveconnected to the heat-exchanging coils. Switching this valve changes the path of the refrigerant. The compressor stops forcing the heated gas from the compressor into the narrow condenser; instead, it forces the gas into a widebypass tube. The hot gas is cycled back to the evaporator without condensing. When you force this hot gas through the evaporator pipes, the pipes and the ice tray heat up rapidly, which loosens the ice cubes.Typically, the individual cube cavities areslantedso the loosened ice will slide out on their own, into a collection bin below. Some systems have acylinder pistonthat gives the tray a little shove, knocking the cubes loose.This sort of system is popular in restaurants and hotels because it makes ice cubes with a standard shape and size. Other businesses, such as grocery stores and scientific research firms, need smallerice flakesfor packing perishable items