Essay: Lamination

1.1 Problem Summery
In packaging industries, flexible packaging and lidding seal materials are manufactured by dry bond lamination process. This dry bond lamination is done by heat seal coating machine. In heat seal coating machine dry bond lamination is achieved by blow of dry hot air, which is provided by gas fired furnace. Aim of the project is to increase the temperature of delivered air by means of minimizing the heat loss occurring in duct and also making necessary changes in gas fired furnace. This will result in improved quality of dry bond lamination which ultimately leads to better productivity. Solution for the problem may be achieved with the help of theoretical understanding.
1.2 Aim and objectives of the project
The hot air delivery is divided into two parts (i) ducts and (ii) furnace.
First part includes the study of heat loss from galvanised iron duct carrying heated air and to determine the resulting drop in temperature in the air flowing in the ducts. The study correlates heat loss to different factors like velocity of air in ducts, coefficient of insulation material, temperature of the air in the duct, temperature of the ambient air, humidity of the ambient air, covering of the duct, length of the duct and its dimensions (height and width). The study was confined to ducts without any interference from other nearby surface.
Second part includes study of forced draft gas fired furnace which is capable of generating temperature of 2500C.Under this study includes air fuel ratio, flame formation, air temperature produced, cogeneration of heat, air filters, gas burners, combustion process. Design of furnace plays significant role in achieving favourable temperature. Thus this part concentrates more on design aspects for the furnace.
1.3 PROBLEM SPECIFICATION
As per the teams observations following parameters for ducting system were found as follows,
· Temperature of air entering the duct: 240o C
· Temperature of air at the end of duct: 140o C
· Length of run: 22m 20cm
· Outside Perimeter of duct: 2.20m
· Insulation material: Glass Wool
· Duct (pipe) material: Galvanized-iron
· Covering on insulation material: Aluminium foil
For furnace part, specifications are as follows
· Forced Draft
· Gas Fired
· Fuel: Liquefied Petroleum Gas (10,997 Kcal/kg)
· Fuel Consumption: 4.045mmbtu per day(12 hours working)
for heat seal coating machine,
· Dry bond lamination process.
· Favourable working temperature: 180oC.
· Number of stations: 5
The temperature difference between actual and required by the Heat Seal Coting machine results in poor quality of lamination.
1.4 literature
FURNACE
Furnaces are used throughout the industry to provide the heat, using the combustion of fuels. These fuels are solid, liquid or gaseous like coal, LPG gas, natural gas,etc. Furnaces consist essentially of an insulated chamber containing tubes. Tubes carry the process fluid to be heated, and sizes are device for burning the fuel in air to generate hot gases. A great variety of geometries and sizes are used, and much the design is based on experience of the skill employers.
Furnaces that work on gas typically have some common gas furnace parts:
A gas manifold
gas burners
heat exchanger
vents
ignition controls
safety controls
and blower motor.
The appliance itself resembles a large box that absorbs cold air and cleans it by means of an air filter. The air heated by the gas burner is distributed by the blower motor through the ductwork.
Gas Manifold
The gas manifold connects the main burners with the gas valve. The burners are connected to the manifold via brass fittings, known as spuds. The size of the holes drilled in the fitting mainly depends on two things the type of fuel used (natural gas, propane,etc) and the amount of gas passing to the gas burners. Most furnaces have spuds for natural gas and liquid propane. In general, the gas manifold requires little maintenance, unless it is exposed to the elements.
Gas Burners
The gas burners are ignited by a pilot flame or electronic ignition that is installed in most of the modern gas furnaces. The main function of the gas burners is to heat up cold air using heat exchangers that are made of stainless steel. The warm air is then distributed through the ductwork by a blower motor.
The burner in the vertical, cylindrical furnace, is located in the floor and fires upward. Some furnaces have side fired burners, such as in train locomotives. The burner tile is made of high temperature refractory and is where the flame is contained. Air registers located below the burner and at the outlet of the air blower are devices with movable flaps or vanes that control the shape and pattern of the flame, whether it spreads out or even swirls around. Flames should not spread out too much, as this will cause flame impingement. Air registers can be classified as primary, secondary and if applicable, tertiary, depending on when their air is introduced. The primary air register supplies primary air, which is the first to be introduced in the burner. Secondary air is added to supplement primary air. Burners may include a pre-mixer to mix the air and fuel for better combustion before introducing into the burner. Some burners even use steam as premix to preheat the air and create better mixing of the fuel and heated air. The floor of the furnace is mostly made of a different material from that of the wall, typically hard castable refractory to allow technicians to walk on its floor during maintenance.
A furnace can be lit by a small pilot flame or in some older models, by hand. Most pilot flames nowadays are lit by an ignition transformer (much like a car’s spark plugs). The pilot flame in turn lights up the main flame. The pilot flame uses natural gas while the main flame can use both diesel and natural gas. When using liquid fuels, an atomizer is used, otherwise, the liquid fuel will simply pour onto the furnace floor and become a hazard. Using a pilot flame for lighting the furnace increases safety and ease compared to using a manual ignition method (like a match).
The burner is a part that delivers and burns gas under the furnace, in order to warm it. This isn’t that much different from the burners on your stove top. Once the pilot light ignites the burner, it will proceed to warm the air in the heat exchanger until the heating cycle is over.
Heat Exchanger
The heat exchanger is made of heavy gauge metal mixed with alloys that resist temperatures above 2000° F. Such high temperatures are reached inside the combustion chamber. It is important, therefore, to perform annual inspections and examine the integrity of the heat exchanger. Over time, cracks develop in the heat exchangers and carbon monoxide may leak into the air. Premises with gas furnaces that burn solid or fossil fuels need to be equipped with carbon monoxide detectors. Although heat exchangers are safe, accidents happen and prompt reaction is required.
Venting
Vents are usually made of stainless steel or PVC. The latter is used more often due to its lower price and higher durability. The vent pipe carries the exhaust gasses that are formed with combustion out of the premises. The standard venting that is recommended for gas furnaces is type B gas vent pipes.
Ignition Controls
Modern furnaces use integrated circuit boards to monitor the furnace’s operations. Light emitting diodes show failure codes if the gas furnace is malfunctioning. These codes are typically listed on the door of the furnace and the Owner’s manual.
Safety Controls
The thermocouple is a safety control device that shuts off gas in case the ignitor fails or the pilot light goes out. The thermocouple has two metal wires that are placed in a protective case. Upon heating up, the thermocouple sends a signal to the valve by means of a solenoid, which is operated by a volt transformer. The thermocouple converts heat into an electrical signal that allows the valve to close or open.
Blower Motor
The blower motor works to distribute warm air through the ductwork, which is then cooled down and returned back to the furnace. Air enters the air filters and a new heating loop begins.
Other than above component one of the notable component is,
Air Filter
The air filter is a fiber mesh stretched over a metal frame installed in front of the return blower of your furnace. It’s there to prevent dust particles and other contaminants from getting into the system and causing damage. It does get dirty over time, so you should regularly clean or replace it.
DUCTING AND INSULATION
Ducting means a tube, pipe, or canal by means of which a substance, esp a fluid or gas, is conveyed or a tube or passageway in a building or machine for air, liquid, cables, etc.
Metal ducts often use fiberglass insulation having an attached metal foil vapor barrier. The duct insulation should be at least R-6, and the vapor barrier should be installed to the outside of the insulation – facing away from the duct. The seams in the insulation are usually stapled together around the duct and then taped.
Thermal insulation is the reduction of heat transfer (the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.
Heat flow is an inevitable consequence of contact between objects of differing temperature. Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body.
CATEGORIES OF INSULATION MATERIALS
Insulation materials may be categorized (Turner and Malloy, 1981) into one of five major types
1) Cellular,
2) Fibrous,
3) Flake,
4) Granular, and
5) Reflective.
Cellular insulations
Cellular insulations are composed of small individual cells either interconnecting or sealed from each other to form a cellular structure. Glass, plastics, and rubber may comprise the base material and a variety of foaming agents are used.
Cellular insulations are often further classified as either open cell (i.e. cells are interconnecting) or closed cell (cells sealed from each other). Generally, materials that have greater than 90% closed cell content are considered to be closed cell materials.
Fibrous insulations
are composed of small diameter fibers that finely divide the air space. The fibers may be organic or inorganic and they are normally (but not always) held together by a binder. Typical inorganic fibers include glass, rock wool, slag wool, and alumina silica.
Fibrous insulations are further classified as either wool or textile-based insulations. Textile-based insulations are composed of woven and non-woven fibers and yarns. The fibers and yarns may be organic or inorganic. These materials are sometimes supplied with coatings or as composites for specific properties, e.g. weather and chemical resistance, reflectivity, etc.
Flake insulations
are composed of small particles or flakes which finely divide the air space. These flakes may or may not be bonded together. Vermiculite, or expanded mica, is flake insulation.
Granular insulations
are composed of small nodules that contain voids or hollow spaces. These materials are sometimes considered open cell materials since gases can be transferred between the individual spaces. Calcium silicate and molded perlite insulations are considered granular insulation.
Reflective Insulations
and treatments are added to surfaces to lower the long-wave emittance thereby reducing the radiant heat transfer to or from the surface. Some reflective insulation systems consist of multiple parallel thin sheets or foil spaced to minimize convective heat transfer. Low emittance jackets and facings are often used in combination with other insulation materials.
Another material sometimes referred to as “thermal insulating coatings” or paints is available for use on pipes, ducts, and tanks. These paints have not been extensively tested and additional research is needed to verify their performance.
Insulation materials or systems may also be categorized by service temperature range.
There are varying opinions as to the classification of mechanical insulation by the service temperature range for which insulation is used. As an example, the word cryogenics means “the production of freezing cold”; however the term is used widely as a synonym for many low temperature applications. It is not well-defined at what point on the temperature scale refrigeration ends and cryogenics begins. The National Institute of Standards and Technology in Boulder, Colorado considers the field of cryogenics as those involving temperatures below -180 C. They based their determination on the understanding that the normal boiling points of the so-called permanent gases, such as helium, hydrogen, nitrogen, oxygen and normal air, lie below -180 C while the Freon refrigerants, hydrogen sulfide and other common refrigerants have boiling points above -180 C.
Understanding that some may have a different range of service temperature by which to classify mechanical insulation, the mechanical insulation industry has generally adopted the following category definitions:
Category
Definition
Cryogenic Applications
-50 F & Below
Thermal Applications:
Refrigeration, chill water and below ambient applications
Medium to high temperature applications
-49 F to + 75 F
+76F to +1,200 F
Refractory Applications
+1,200 F & Above
PHYSICAL PROPERTIES OF INSULATION MATERIALS
Selecting an insulation material for a particular application requires an understanding of the physical properties associated with the various available materials.
Use Temperature is often the primary consideration in the selection of an insulating material for a specific application. Evidence of warping, cracking, delamination, flaming, melting, or dripping are indications that the maximum use temperature of the material has been exceeded. There is currently no industry accepted test method for determining the minimum use temperature of an insulation material, but minimum temperatures are normally determined by evaluating the integrity and physical properties of the material after exposure to low temperatures.
Thermal Conductivity is defined as the time rate of steady state heat flow through a unit area of a homogeneous material induced by a unit temperature gradient in a direction perpendicular to that unit area. The term apparent thermal conductivity is used for many insulation materials to indicate that additional non-conductive modes of heat transfer (i.e. radiation or free convection) may be present.
In the insulation industry, thermal conductivity is typically expressed as the symbol k, in units of Btu·in/(h ft² °F) or λ, in units of W/(m·°C)
The apparent thermal conductivity of insulation materials is a function of temperature.
A number of other terms related to thermal conductivity are sometimes used. These are not material properties, but are used to describe the thermal performance of specific products or systems.
Thermal Conductance, or C-value, is the time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces. Or a flat board or blanket insulation, C is calculated as the thermal conductivity divided by the thickness (C=k/t).
Thermal Resistance, or R-value, is the quantity determined by the temperature difference, at steady state, between two defined surfaces of a material or construction that induces a unit heat flow rate through a unit area. For a flat board or blanket insulation, R is calculated as the thickness divided by the thermal conductivity (R=t/k). Thermal resistance is the inverse of thermal conductance.
The thermal transmittance, or U-factor, is the heat transmission rate through unit area of a material or construction and the boundary air films, induced by a unit temperature difference between the environments on each side. Units of U are typically Btu/(h·ft²·°F)
Density is the mass per unit volume of a material. For insulation we are normally concerned with the “bulk” or the “apparent” density of the product. Bulk density is the mass of the product divided by the overall volume occupied, and is an average of the densities of the individual materials making up the product. Density is denoted by the symbol ρ and expressed in units of lb/ft³ or kg/m³. Historically, density was used as a proxy for other properties of insulation (e.g. compressive resistance), and is still found in various insulation specifications. It is useful in the design of support/hanger systems where the overall weight of the system must be considered. It also becomes important in transient heat flow situations.
Specific Heat is the amount of thermal energy required to raise the temperature of a unit mass of a material by one degree. Normally expressed in units of Btu/lb·°F or kJ/kg·°K.
Thermal Diffusivity is the ratio of the conductivity of a material to the product of its density and specific heat. It is an important property in transient situations. Units are ft²/h or m²/s.
Compressive Resistance is defined as the compressive load per unit of area at a specified deformation. When the specified deformation is the start of complete failure, the property is called Compressive Strength. Compressive strength is measured in lb/in² or lb/ft² and is important where the insulation material must support a load without crushing (e.g. insulation inserts used in pipe hangers and supports). When insulation is used in an expansion or contraction joint to take up a dimensional change, lower values of compressive resistance are desirable.
Linear Shrinkage is a measure of the Dimensional Change that occurs in an insulation material under conditions of soaking heat. Most insulation materials will begin to shrink at some definite temperature. Usually the amount of shrinkage increases as the exposure temperature becomes higher. Eventually, a temperature will be reached at which the shrinkage becomes excessive, and the material has exceeded its useful temperature limit.
Water Vapor Permeability is defined as the time rate of water vapor transmission through unit area of flat material of unit thickness induced by unit vapor-pressure difference between two specific surfaces, under specified temperature and humidity conditions. For insulating materials, water vapor permeability is commonly expressed in units of perm-in. A related and often confused term is water vapor permeance (in perms), which describes the water vapor flux through a material of specific thickness and is generally used to define the performance of a vapor retarder. In below ambient applications, it is important to minimize the rate of water vapor flow to the cold surface. This is normally accomplished by using vapor retarders with low permeance, insulation materials with low permeability, or both in combination.
Water Absorption is generally measured by immersing a sample of material under a specified head of water for a specified time period. It is a useful measure when considering the amount of liquid water that may be absorbed due to water leaks in weather barriers or during construction.
Water Vapor Sorption
Wicking
Mineral Fiber (Fiberglass and Mineral Wool)
Mineral Fiber insulations are defined by ASTM as insulations composed principally of fibers manufactured from rock, slag, or glass, with or without binders. Fiberglass and Mineral Wool products fall in this category. There is some confusion concerning the nomenclature used for these materials. Fiberglass products (sometimes called “fibrous glass” or “glass wool”) and mineral wool products (sometimes called “rock wool” or “slag wool”) are covered by the same ASTM “Mineral Fiber” specifications, and sometimes by the same type and grade. Specifiers are cautioned to call out both the specific material and the ASTM Type and Grade when specifying these products. For example “Fiberglass pipe insulation meeting the requirements of ASTM C 547 Type I, Grade A” or “Mineral Wool pipe insulation meeting the requirements of ASTM C 547 Type II, Grade A”.
Insulation materials
Rock Wool:
Rock wool materials based on selected basalt as main raw material. Through
melting of high temperature, they became abio-fibre manufactured by high-speed centrifugal
equipments. After special adhibitor and dust-prevention oil adding and fibreformed
structure changing, they finally formed a newly light quality warm-keeping
material. According to different purposes, they can be processed rock wool slab, rock
wool felt and rock wool pipe section etc.
They can be broadly used in the heat preservation projects in architecture-building,
industry and shipbuilding because of the best heat-insulation, sound-insulation, stable
chemical capability,causticity-resistance and incombustibility.
The whole equipments were imported from foreign countries with advanced
technology, high automatization. Now, the company has 2 production lines with annual
output of 40 thousand ton. It is the largest rock wool materials manufacturer in the
country.
Advantages
Small coefficient of heat conductivity and good capability of heating preservation,
outstanding effect of energy-saving
BNBM rock wool fiber is slender and tender, the average diameter is 4-7 m and the coefficient of heat
conductivity is between 0.035 and 0.043W/mk. The product has good capability of heating preservation
and outstanding effect of energy-saving.
Excellent fireproofing capability
BNBM rockwool materials have been identified the incombustibility by Tianjin Fire Control Department
of National Public Security Ministry. The product achieved authentication certifications of ship’
classification from CCS in China, Laos in Britain, DNV in Norway, BV in France, ABS in U.S. etc.
Excellent sound absorption and sound insulation capability
BNBM rock wool fiber was equally distributing. Its multihole outside and high-spacing rate inside
made it have good effect in sound absorption. This was identified by Physics Graduate School of
China National Architecture science Academe.
Stable capability of chemisty chenmistry may keep the long-term using
Ensure better materialization and catamorphism-resistance because of stable chemical elements and
high acidity coefficient (the highest can reach about 2.0).
No causticity effects the heat preservation materials
The product will not corrode heat presevation materials because of less chlorin hydronium containing.
It fits for ASTM C795 standard and GB/T 17393-1998 standard.
Green building materials and no harm for the boby
BNBM rock wool materials are no harm to the boby because of low organism containing and no
asbestos containing. The product is fit for A’-level fitment materials’ of GB6566-2001 of ‘National
Building Material Radio Element Limits’. At the same time it can be used as the carrier of no-earth
planting and planting base of vegetables, fruits and flowers.
Broad using range
BNBM rock wool materials highest using temperature can reach 650 and it can broadly using in
architecture, industry, shipmaking or reprocess etc.
glass wool:
Made from bonded glass fibres. For thermal and acoustic insulation, available with or without AI.foil.
Idea for under deck Insulation, over the false ceiling and for Ducting.
Size: Rolls in standard width of 1.2 m
Density: 16, 24, 32 & 48Kg/m3
Thickness : 25, 40, 50mm Aslo R.P.Tissue and Reigid Boards etc.,
Glass wool Insulation is one of the most widely used forms of insulations world-wide because of its
thermal and acoustic properties, light weight, high tensile strength and exceptional resilience. Glass
wool is one of the most dominant types of insulations preferred in applications with service
temperatures ranging upto 250C.
Glass wool consist of fine, long, inorganic fibers bonded together by high temperature binder. These
fibers (each of approx. 6 – 7 microns diameter) are distributed to trap millions of tiny pockets of air
in it thereby creating it an excellent thermal and acoustic insulation. The light weight of Glass wool
also offers significant advantages during transport and installation. In addition, Glass wool is
chemically inert and has no impurities such as iron shots, sulphur and chloride. The product is non
corrosive to metal and does not support mold grow. It is manufactured from renewable raw materials
and is environmental friendly in every stage.
Glass wool is formed into products with various thickness and densities. It comes in the form of rolls
and slabs with or without Alumminum foil.
Types of facings: Aluminum Foil, Black Glass Tissue, Glass Cloth.
Product Range: Density 12 Kg/Cubic m to 100 Kg/Cubic m and thickness 12mm to 100mm
Temperature RanGlass wool is rot proof and odorless.
Fire Safety: Glass wool is non-combustible in accordance with BS 476 incombustible, extremely low
spread of flame, non emission of dense smoke and toxic gases, on depletion of oxygen (high oxygen
index 70%).
Biological: Glass wool is inorganic. Does not encourage growth of fungi and vermin.
ge: Glass wool is suitable for applications ranging from minus 195 degree Celsius
to plus 230 degree Celsius. For special applications up to 450 degree. Alumminum foil facing is
suitable up to 120 degree Celsius.
Chemical Stability: Glass wool is chemically inert. Application does not cause or accelerate corrosion.
Fibreglass
Rockwool
Composition
KIMMCO Fiber Glass insulation products are made of thermally and acoustic efficient fiberized glass bounded with thermosetting resin.
made from basalt, dolomite, limestone.
Contains up to 25% of unfiberized materials, which means dust, fiber migrations.
Shot contents
ASTM C1335
Nil
Up to 25%
Surface Finish & Feel
As no unfiberised parts (SHOTS) and the fibers are FINE, fiberglass insulation products is having SMOOTH finish and feel
Rock wool comprises of COURSE fiber and due to the SHOT content, it has a ROUGH finish and feel.
Thermal Performances
Thermal Conductivity (k value)
Thermal Resistance (R value)
2-3 times less density of rock wool products required to achieve same thermal performances
2-3 times more density of rock wool products required to achieve same thermal performances of Glass wool products
Acoustic performances
Noise Reduction Coefficient (NRC value)
2-3 times less density of rock wool products required to achieve same acoustical performances;
2-3 times more density of rock wool products required to achieve same acoustical performances of Glass wool products
Resistance to low frequencies
(20 to 185 HZ), generated by
HVAC equipments
Excellent
No damage
Shots are slowly breaking out from the rock fibers, under the effects of low frequency vibrations that leads to sagging of products, and weight losses.
Fire rating ASTM E136
non combustible
non combustible
Flame spread
Smoke developed
ASTM E84/UL723
Not over 25
Not over 50
UL 723 file R 9703
Not over 25
Not over 50
Corrosion
Fiberglass insulation products do not cause or accelerate corrosion
Since it contains leachable Chloride and Sulphide any contact to metal with wet or moist condition may cause and accelerate corrosion. So it is not advisable to use on metal surface if the temp. is less than 150 ºC
Vibration Resistance
( sample assembly is vibrated for 96 hours at a frequency of 20Hz with an amplitude of 0.9 inch )
The weight loss observed for fiberglass of 12 kg/m3 density – less than 0.2%
With NILL sagging
The weight loss observed for Rockwool of 30 kg/m3 density – more than 20.0%
With 5 Inch sagging
PRIOR ART SEARCH (PAS)
While Learning about different patents,one of the patent for a gas fired furnace capable of operating. In the past, attempts have been made to design furnaces of this type that are capable of variable outputs depending on the heating requirement as sensed by temperature sensors in the duct. It has been found that furnaces and burners of this type are generally limited to a maximum 2:1 turndown ratio, i.e., the furnace can operate at either 50% or full output. Generally, as the furnace output is reduced, CO emissions increase and flame instability may also result. Attempts have been made to provide duct-type furnaces capable of operating at less than 50% of maximum output, but these attempts have not been totally successful.
While the other patent application was about recognizing the disadvantages of previous fuel-fired furnaces, provides a novel baffle arrangement within a combustion chamber which is economical, easy to fabricate and yet improves the efficiency of combustion within the chamber by increasing the circulation of the products of combustion within the combustion chamber.The present invention advantageously provides a straight-forward arrangement for the preparation of a fuel-fired furnace.The present invention further provides a novel heat exchanger for use in fuel-fired furnaces including baffle means therein spaced from and aligned with the flue gas combustion outlet to increase the circulation of the products of combustion within the combustion chamber and increase the heat output of all primary heating surfaces.
PLAN OF WORK
JUNE-INDUSTRIAL SHODH YATRA
Before getting started with INDUSTRIAL SHODHYATRA, the team listed out the field of interest. This includes design, automobiles and thermal. Team with reference of professors visited various industries like Windsor Machines Limited (Ahmedabad), Prashant Group of Companies (Ahmedabad), Indo-German Tool Room (Ahmedabad), Green Pack Foil Pvt.Ltd (Satej), Inductotherm India Pvt.Ltd (Ahmedabad), Navrang Industries (Ahmedabad), Hindustan Dorr-Oliver Limited (Ahmedabad), Arham Polymers (Ahmedabad).
JULY