What Is Heat Transfer

[caption id="attachment_198" align="alignright" width="300" caption="what is heat transfer"][/caption]

Heat transfer is considered as one of the most basic discipline of chemical engineering & technology. It generally concerns with generation, consumption and conversion of heat energy in the system. Heat transfer; it self plays a very important role in process industries, and it is always better for the process industries, to optimize their heat transfer processes [may include furnaces, evaporators, distillation units, dryers, reaction vessels etc] by the selection of proper heat exchangers, preventing heat losses and controlling the heat flow rate.

Heat transfer under normal conditions always flows from a hotter region to a cooler region, i.e. heat transfer follows the temperature gradient between the two systems [or system and surrounding], until a thermal equilibrium is maintained between the two systems.  However, according to the “Clausius statement of second law of thermodynamics”, if the work is done on the system, the heat can flow from a colder region to a hotter region. This Clausius statement is the basic principle behind the working of refrigerators.

Now how to calculate heat transfer :

\[Q=UAΔT\]

Where,

Q = transfer of heat per unit time
A = heat transfer area
ΔT = temperature difference between two systems

This is the most basic expression to define heat transfer, there are several other heat transfer formulas derived from this expression. Picture at the right side is taken from images by dan.

There are three forms of heat transfer:

1) Conduction

Conduction is generally considered as the heat transfer phenomena for the solids, however conduction can also occur in fluids too [in microscopic level, like diffusion phenomena]. In solids, Conduction is the result of transfer of vibration energy from one molecule to other, while in fluids, it occurs in addition as a result of transfer of kinetic energy. Conduction follows the Fourier Law of Heat Conduction:

\[Q=-kAΔT\]

Where,

Q = transfer of heat per unit time
k = conductive heat transfer coefficient
A  = heat transfer area
ΔT = temperature difference between two systems

  The thermal conductivity units in SI system is W/mK.

2) Convection

Convective heat transfer occurs when the heat is transferred from a solid surface to a moving fluid owing to the temperature difference between the solid and the fluid. Convection follows the Newton’s Cooling Law of Heat Convection:

\[Q=hA(T-T_{'})\]

Where,

Q = transfer of heat per unit time
h = convection heat transfer coefficient
A  = heat transfer area
T = temperature of fluid
T'= temperature of solid

3) Radiation

All materials radiate thermal energy in the form of electromagnetic waves. So radiation is the transfer of heat by the emission of electromagnetic waves. When they fall on the body, they may partially be reflected, transmitted or absorbed. Radiation is that fraction which falls and absorbed by the body.

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What Is Heat Transfer

Heat transfer is considered as one of the most basic discipline of chemical engineering & technology. It generally concerns with generation, consumption and conversion of heat energy in the system. Heat transfer; it self plays a very important role in process industries, and it is always better for the process industries, to optimize their heat transfer processes (may include furnaces, evaporators, distillation units, dryers, reaction vessels etc) by the selection of proper heat exchangers, preventing heat losses and controlling the heat flow rate.

Heat transfer under normal conditions always flows from a hotter region to a cooler region, i.e. heat transfer follows the temperature gradient between the two systems (or system and surrounding), until a thermal equilibrium is maintained between the two systems.  However, according to the “Clausius statement of second law of thermodynamics”, if the work is done on the system, the heat can flow from a colder region to a hotter region. This Clausius statement is the basic principle behind the working of refrigerators.

Now how to calculate heat transfer :
                                                           Q = UAΔT

Where,
  Q = transfer of heat per unit time
  A = heat transfer area
  ΔT = temperature difference between two systems

This is the most basic expression to define heat transfer, there are several other heat transfer formulas derived from this expression.

There are three forms of heat transfer:

1) Conduction

Conduction is generally considered as the heat transfer phenomena for the solids, however conduction can also occur in fluids too(in microscopic level, like diffusion phenomena). In solids, Conduction is the result of transfer of vibration energy from one molecule to other, while in fluids, it occurs in addition as a result of transfer of kinetic energy.

Conduction follows the Fourier Law of Heat Conduction:

                                                          Q = -kAΔT

Where,
  Q = transfer of heat per unit time
   k = conductive heat transfer coefficient
  A  = heat transfer area
 ΔT = temperature difference between two systems

  The thermal conductivity units in SI system is W/mK.

2) Convection

Convective heat transfer occurs when the heat is transferred from a solid surface to a moving fluid owing to the temperature difference between the solid and the fluid.

Convection follows the Newton’s Cooling Law of Heat Convection:

                                                        Q = hA(T – T')
Where,
  Q = transfer of heat per unit time
   h = convection heat transfer coefficient
  A  = heat transfer area
  T = temperature of fluid
  T'= temperature of solid

3) Radiation

All materials radiate thermal energy in the form of electromagnetic waves. So radiation is the transfer of heat by the emission of electromagnetic waves. When they fall on the body, they may partially be reflected, transmitted or absorbed. Radiation is that fraction which falls and absorbed by the body.

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What Are Fertilizers

[caption id="attachment_217" align="alignright" width="300" caption="what are fertilizers"][/caption]

Fertilizer industry is one of the most important industries. To study that what are fertilizers, the basics of chemical engineering are required. Types of fertilizer depend on the thorough study of the nature of the soil, and the type of the plants. So first, it is important to review the plants physiology and needs then we can move on to what are fertilizers.

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Plants have the natural ability to convert carbon dioxide from the atmosphere and inorganic components of the earth directly into the fats, proteins and high energy carbohydrates. So the plants are the essential elements for the nutrition and growth of humans as well as the animals too. For a plant to grow properly, it needs sun light, air, water and minerals. As discussed above, the plant takes these minerals from the earth, but some times the soil has the deficiency of the certain minerals so these minerals are added manually, and are named as fertilizers. So,

.

“The fertilizers are the minerals [nutrients], which are added to soil to improve its fertility”.

Some decades before, the agriculture was totally based on the empirically developed agricultural practices. But now, the plant physiology, and its nutrition involves a general process engineering knowledge, as scientific study leads a chemical engineer to required fertilization or photosynthesis level.

The plant needs approximately 22 different chemical elements for proper growth. The three primary nutrients of fertilizers are nitrogen [N – helps in the growth of plants], phosphorous [P – encourages blooming, rooting and fruit production], or potassium [K – resists plant diseases and resist in winter hardness, the 3 secondary nutrients are Magnesium (Mg) , Calcium (Ca) and Sulfur (S), while the 3 essential elements are Carbon (C), Hydrogen (H) and Oxygen (O). Plants obtain these elements from carbon dioxide (CO_2) and water (H_2O).

Types Of Fertilizers

The types of fertilizer are:

1) Organic/natural fertilizers

These fertilizers are derived from the organic / naturally occurring sources. The human or animal wastes, slurry [needs to be metal free], bones, fish meal, blood and similar substances are the main content of the fertilizer. Normally these types of nutrients are not chemically treated. The mineral content of these fertilizers is comparatively lower than the synthetic one, but has the benefit of being natural, increase biological and physical nutrient storage of the soil; increases soil moisture content, and also mitigate the risk of over fertilization.

2) Synthetic fertilizer

These fertilizers are composed of synthetic minerals or chemicals, so these are also named as synthetic fertilizer or inorganic fertilizers. As all the minerals used for the production of these fertilizers are synthetic, so we use several other processes to prepare the raw materials. A process engineer normally recommends using the Haber-Bosch process for the production of synthetic ammonia. This synthetic ammonia is generally used in other nitrogen fertilizers like urea or anhydrous ammonium nitrate. These synthetic fertilizers are generally used to treat maze, barley, soy, sunflower fields. Also the studies show that nitrogen fertilizers can increase the bio mass of these crops, along with the beneficial effect on the nitrogen level of the soil. Unlike the organic fertilizers, they don’t take too much time for the growth of the plant, but synthetic fertilizer provides the appropriate actions for plant growth in required time frame.

Forms Of Fertilizers:

Mostly, fertilizers are used in the granular [powder] form, however liquid fertilizers are also widely produced and used.

Environmental Concerns Of Fertilizers

There are several environmental concerns with the poor handling of fertilizers. The general environmental problems are

Eutrophication – i.e. Phosphorous is contaminated on the soil, is bound to soil particles and can not be washed out. It indirectly stimulates the growth of algae. These types of algae die, decompose and remove oxygen from the water causing harm to water life.

Contamination of water with phosphates and nitrates. The general process engineering practice describes that the higher level of nitrates in drinking water is hazardous for human health.

Nitrogen remaining in the soil is converted into nitrates by bacteria. These nitrates can be washed out from the surface into river streams, or can be leached into the ground water.

Read More

What Are Fertilizers

Fertilizer industry is one of the most important industries. To study that what are fertilizers, the basics of chemical engineering are required. Types of fertilizer depend on the thorough study of the nature of the soil, and the type of the plants. So first, it is important to review the plants physiology and needs then we can move on to what are fertilizers.

Plants have the natural ability to convert carbon dioxide from the atmosphere and inorganic components of the earth directly into the fats, proteins and high energy carbohydrates. So the plants are the essential elements for the nutrition and growth of humans as well as the animals too. For a plant to grow properly, it needs sun light, air, water and minerals. As discussed above, the plant takes these minerals from the earth, but some times the soil has the deficiency of the certain minerals so these minerals are added manually, and are named as fertilizers. So,

           “The fertilizers are the minerals (nutrients), which are added to soil to improve its fertility”.

Some decades before, the agriculture was totally based on the empirically developed agricultural practices. But now, the plant physiology, and its nutrition involves a general process engineering knowledge, as scientific study leads a chemical engineer to required fertilization or photosynthesis level.

The plant needs approximately 22 different chemical elements for proper growth. The three primary nutrients of fertilizers are nitrogen (N – helps in the growth of plants), phosphorous (P – encourages blooming, rooting and fruit production), or potassium (K – resists plant diseases and resist in winter hardness, the 3 secondary nutrients are Magnesium (Mg) , Calcium (Ca) and Sulfur (S), while the 3 essential elements are Carbon (C), Hydrogen (H) and Oxygen (O). Plants obtain these elements from carbon dioxide (CO2) and water (H2O).

The types of fertilizer are:

1) organic/natural fertilizers

These fertilizers are derived from the organic / naturally occurring sources. The human or animal wastes, slurry (needs to be metal free), bones, fish meal, blood and similar substances are the main content of the fertilizer. Normally these types of nutrients are not chemically treated. The mineral content of these fertilizers is comparatively lower then the synthetic one, but has the benefit of being natural, increase biological and physical nutrient storage of the soil; increases soil moisture content, and also mitigate the risk of over fertilization.

2) Synthetic fertilizer

These fertilizers are composed of synthetic minerals or chemicals, so these are also named as synthetic fertilizer or inorganic fertilizers. As all the minerals used for the production of these fertilizers are synthetic, so we use several other processes to prepare the raw materials. A process engineer normally recommends using the Haber-Bosch process for the production of synthetic ammonia. This synthetic ammonia is generally used in other nitrogen fertilizers like urea or anhydrous ammonium nitrate. These synthetic fertilizers are generally used to treat maze, barley, soy, sunflower fields. Also the studies show that nitrogen fertilizers can increase the bio mass of these crops, along with the beneficial effect on the nitrogen level of the soil. Unlike the organic fertilizers, they don’t take too much time for the growth of the plant, but synthetic fertilizer provides the appropriate actions for plant growth in required time frame.

Forms Of Fertilizers:

Mostly, fertilizers are used in the granular (powder) form, however liquid fertilizers are also widely produced and used.

Environmental Concerns Of Fertilizers

There are several environmental concerns with the poor handling of fertilizers. The general environmental problems are

Eutrophication – i.e. Phosphorous is contaminated on the soil, is bound to soil particles and can not be washed out. It indirectly stimulates the growth of algae. These types of algae die, decompose and remove oxygen from the water causing harm to water life.

Contamination of water with phosphates and nitrates. The general process engineering practice describes that the higher level of nitrates in drinking water is hazardous for human health.

Nitrogen remaining in the soil is converted into nitrates by bacteria. These nitrates can be washed out from the surface into river streams, or can be leached into the ground water.

Read More

Types of catalysis

In my last post, I have discussed about the general catalysis phenomena, and its most basic types. But the homogeneous and heterogeneous catalysis are not the only types of the catalysis. The chemical engineer also classifies catalysis on the basis of the nature of species responsible for the catalytic activity. These types are mostly inter-related with other types of the same nature. E.g. molecular catalysts can be used as homogeneous, as well as heterogeneous catalysts, Surface catalysts are heterogeneous catalysts etc. Some of the types are:

1) Molecular Catalysis:

This term is used for the systems, where identical molecular species are the catalytic entity. Many of these catalysts are used as homogeneous catalysts, but these can also be used in heterogeneous (multi-phase) catalysis.

2) Surface Catalysis:

Surface catalysis takes place on the surface atoms of the extended solid. It depends on the different properties of the surface atoms, and different types of the molecular sites. Surface catalysts are solid, so these are heterogeneous catalysts by nature.

3) Enzyme Catalysis:

Enzymes are proteins, polymers of amino acids, so this type of catalysis is used to catalyze reactions in living organism, biological and biochemical reactions. The enzyme catalysis is usually molecular catalysis.

4) Auto Catalysis:

In autocatalysis, there is no need to use a separate catalysis, but in a reaction one of the products acts as a catalyst it self. Some biochemical reactions are experimentally observed as the auto catalysis reactions.

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Types of catalysis

In my last post, I have discussed about the general catalysis phenomena, and its most basic types. But the homogeneous and heterogeneous catalysis are not the only types of the catalysis. The chemical engineer also classifies catalysis on the basis of the nature of species responsible for the catalytic activity. These types are mostly inter-related with other types of the same nature. E.g. molecular catalysts can be used as homogeneous, as well as heterogeneous catalysts, Surface catalysts are heterogeneous catalysts etc. Some of the types are:

1) Molecular Catalysis:

This term is used for the systems, where identical molecular species are the catalytic entity. Many of these catalysts are used as homogeneous catalysts, but these can also be used in heterogeneous (multi-phase) catalysis.

2) Surface Catalysis:

Surface catalysis takes place on the surface atoms of the extended solid. It depends on the different properties of the surface atoms, and different types of the molecular sites. Surface catalysts are solid, so these are heterogeneous catalysts by nature.

3) Enzyme Catalysis:

Enzymes are proteins, polymers of amino acids, so this type of catalysis is used to catalyze reactions in living organism, biological and biochemical reactions. The enzyme catalysis is usually molecular catalysis.

4) Auto Catalysis:

In autocatalysis, there is no need to use a separate catalysis, but in a reaction one of the products acts as a catalyst it self. Some biochemical reactions are experimentally observed as the auto catalysis reactions.

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Catalysis

Catalysis is the key to optimized and efficient process engineering. Catalysis is the major problem for the chemical engineer while understanding the basic chemical reaction engineering. Catalysis is used in most of the industrial and biological processes, and the products of these processes include food, drugs, clothing, plastics, fuels or detergents.

To understand the phenomena of the catalysis, a chemical engineer must understand that what is catalyst? Catalyst is the substance, which changes the rate of the chemical reaction, with out being consumed in the reaction it self. But practically after the completion of the process, the catalyst transforms (not consumed), so mostly, the catalysts needed to be regenerated and can be used again.

These catalysts may be in any state of matter, i.e. liquid, gas or solids. There can be two types of a catalyst:

• positive catalysts : increases the rate of the reaction.

• negative catalysts : decreases the rate of the reaction. These are also called as inhibitors.

Catalysis is the phenomena of change in the rate of a chemical reaction in presence of a catalyst. There can be two types of the catalysis.

1) Homogeneous catalysis:

The catalysts are in the same phase as the reactants are. I.e. the homogeneous catalysts are co-dissolved substances in the solvent, with the reagents. The acid catalysis can be taken as an example of the homogeneous catalysis. In which the water, after self ionization forms protons (most penetrating homogeneous catalyst).

2) Heterogeneous catalysis:

The catalysts are in different phase, as that of the reactants. Most heterogeneous catalysts are solids (in a liquid or gaseous reaction mixture). But as the surface area of the catalyst (especially in solid catalyst case) has important effect on the rate of reaction. So the catalysts are generally crushed into the smaller particle size, as the smaller the particle size, the more will be the surface area of the catalyst.

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Catalysis

Catalysis is the key to optimized and efficient process engineering. Catalysis is the major problem for the chemical engineer while understanding the basic chemical reaction engineering. Catalysis is used in most of the industrial and biological processes, and the products of these processes include food, drugs, clothing, plastics, fuels or detergents.

To understand the phenomena of the catalysis, a chemical engineer must understand that what is catalyst? Catalyst is the substance, which changes the rate of the chemical reaction, with out being consumed in the reaction it self. But practically after the completion of the process, the catalyst transforms (not consumed), so mostly, the catalysts needed to be regenerated and can be used again.

These catalysts may be in any state of matter, i.e. liquid, gas or solids. There can be two types of a catalyst:

• positive catalysts : increases the rate of the reaction.

• negative catalysts : decreases the rate of the reaction. These are also called as inhibitors.

Catalysis is the phenomena of change in the rate of a chemical reaction in presence of a catalyst. There can be two types of the catalysis.

1) Homogeneous catalysis:

The catalysts are in the same phase as the reactants are. I.e. the homogeneous catalysts are co-dissolved substances in the solvent, with the reagents. The acid catalysis can be taken as an example of the homogeneous catalysis. In which the water, after self ionization forms protons (most penetrating homogeneous catalyst).

2) Heterogeneous catalysis:

The catalysts are in different phase, as that of the reactants. Most heterogeneous catalysts are solids (in a liquid or gaseous reaction mixture). But as the surface area of the catalyst (especially in solid catalyst case) has important effect on the rate of reaction. So the catalysts are generally crushed into the smaller particle size, as the smaller the particle size, the more will be the surface area of the catalyst.

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Rheology

Rheology is the study of deformation and flow behavior of materials. Rheology is generally associated with the behavior of the fluids, but the semi-solids materials (under specific conditions) some times also possess the rheological properties.

Rheology normally accounts for the flow of unusual materials, generally non-Newtonian fluids, as rheological properties are the parameters in any quantitative functional relation between the stress and strain.And as we have already discussed that the Newtonian fluids have the linear relationship between the stress and strain.

All non Newtonian fluids do not possess same properties. For example paints, blood, custard, ketchup etc do not fall in the same category of the non Newtonian fluids. So these fluids are divided according to their rheological properties. i.e.

1) Non Newtonian fluids with Time independent viscosity:

1.1)          Shear thinning (Pseudo plastic) fluids

In pseudo plastic fluids, the viscosity decreases with the increase in stress or disturbance. i.e. these fluids are also named as shear thinning fluids. The most common examples of these pseudo plastic fluids are paint, blood, syrups, molasses etc.

           

1.2)          Shear thickening (dilatant) fluids

Like the name, the dilatant fluids are those, whose viscosity increases with the increase in the stress. The most common example is the corn syrup, or the sand in water.

1.3)          Bingham plastic fluids

The bingham plastic fluids are also named as the generalized Newtonian fluids. These fluids have the constant viscosity, but unlike non Newtonian fluids, the stress is dependent on the strain rate and the pressure applied on the fluid. Blood plasma and custard are the common examples of these fluids.

2) Non Newtonian fluids with Time dependent viscosity:

2.1)      Rheopectic

The viscosity of the fluid increases with the increase in the duration of stress,

2.2)          Thixotropic

The viscosity of the fluid decreases with the increase in the duration of stress,

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Rheology

Rheology is the study of deformation and flow behavior of materials. Rheology is generally associated with the behavior of the fluids, but the semi-solids materials (under specific conditions) some times also possess the rheological properties.

Rheology normally accounts for the flow of unusual materials, generally non-Newtonian fluids, as rheological properties are the parameters in any quantitative functional relation between the stress and strain.And as we have already discussed that the Newtonian fluids have the linear relationship between the stress and strain.

All non Newtonian fluids do not possess same properties. For example paints, blood, custard, ketchup etc do not fall in the same category of the non Newtonian fluids. So these fluids are divided according to their rheological properties. i.e.

1) Non Newtonian fluids with Time independent viscosity:

1.1)          Shear thinning (Pseudo plastic) fluids

In pseudo plastic fluids, the viscosity decreases with the increase in stress or disturbance. i.e. these fluids are also named as shear thinning fluids. The most common examples of these pseudo plastic fluids are paint, blood, syrups, molasses etc.

           

1.2)          Shear thickening (dilatant) fluids

Like the name, the dilatant fluids are those, whose viscosity increases with the increase in the stress. The most common example is the corn syrup, or the sand in water.

1.3)          Bingham plastic fluids

The bingham plastic fluids are also named as the generalized Newtonian fluids. These fluids have the constant viscosity, but unlike non Newtonian fluids, the stress is dependent on the strain rate and the pressure applied on the fluid. Blood plasma and custard are the common examples of these fluids.

2) Non Newtonian fluids with Time dependent viscosity:

2.1)      Rheopectic

The viscosity of the fluid increases with the increase in the duration of stress,

2.2)          Thixotropic

The viscosity of the fluid decreases with the increase in the duration of stress,

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types of fluid

Fluid mechanics is one of the major sciences involved in chemical engineering, so a chemical engineer is mostly interested in many aspects of the problems involved in the fluid flow. To understand the fluid mechanics, a chemical engineer must have to understand that what is fluid, and the types of the fluid.

The simplest definition of the fluid is that “Any substance which can flow under pressure is fluid”. Fluid can also be defined as “any substance that has no fixed structure, shape or size, and yields easily to the external pressure”.

There are generally two ways to classify the fluids, i.e.

> Compressible and Incompressible Fluids

> According to viscosity change

Compressible And Incompressible Fluids

The nature of the fluid is said to be compressible or incompressible according to its behavior under applied pressure, i.e.

The incompressible fluid is the one, whose volume is independent of its temperature and pressure, i.e. its volume will not be affected by the change of its temperature and pressure. There is no real fluid, which is completely incompressible, however liquids are assumed to be the incompressible fluids, as they sustain the change of temperature and pressure, more then gases.

The compressible fluids change their volume according to the change in their temperature or pressure. The gases are real example of such type of fluid. However, if the percent change is small, then for practical purposes, a gas may be treated as the compressible fluid.

Classification Of Fluids According To Viscosity Change

The fluids can also be classified according to the effects produced on the fluid by the action of the shear stress. This classification is important, as it determines the way in which the fluid will flow. This classification is based on a most important physical property “viscosity”.

Then main two types under this classification are:

> Newtonian fluid

> Non Newtonian fluid

A Newtonian fluid is the fluid, whose viscosity remains constant regardless of any applied stress. That’s why these fluids are also named as “linear viscous fluids”. The most common example of Newtonian fluid is water. The flow of water remains same, whether it flows alone, or in vigorously agitation condition. Its simplest meaning is that, the fluid will continue to flow, regardless of the forces acting on it. The Newtonian fluids behave according to following equation:

                                                            τ = µ (du/dy)

τ is the shear stress exerted by fluid

µ is fluid viscosity, constant for Newtonian fluids

(du/dy) is the velocity gradient, or the strain.

So for Newtonian fluid, according to the equation, the ratio of stress to strain is constant, there fore, the viscosity is constant.

The viscosity of the non Newtonian fluid is variable, and is dependent upon the applied stress on the fluid. These type of fluids also exhibits the rheological properties .The common examples of non Newtonian fluids are solution of corn starch and water, paints, ink, tooth paste, etc.

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types of fluid

Fluid mechanics is one of the major sciences involved in chemical engineering, so a chemical engineer is mostly interested in many aspects of the problems involved in the fluid flow. To understand the fluid mechanics, a chemical engineer must have to understand that what is fluid, and the types of the fluid.

The simplest definition of the fluid is that “Any substance which can flow under pressure is fluid”. Fluid can also be defined as “any substance that has no fixed structure, shape or size, and yields easily to the external pressure”.

There are generally two ways to classify the fluids, i.e.

> Compressible and Incompressible Fluids

> According to viscosity change

Compressible And Incompressible Fluids

The nature of the fluid is said to be compressible or incompressible according to its behavior under applied pressure, i.e.

The incompressible fluid is the one, whose volume is independent of its temperature and pressure, i.e. its volume will not be affected by the change of its temperature and pressure. There is no real fluid, which is completely incompressible, however liquids are assumed to be the incompressible fluids, as they sustain the change of temperature and pressure, more then gases.

The compressible fluids change their volume according to the change in their temperature or pressure. The gases are real example of such type of fluid. However, if the percent change is small, then for practical purposes, a gas may be treated as the compressible fluid.

Classification Of Fluids According To Viscosity Change

The fluids can also be classified according to the effects produced on the fluid by the action of the shear stress. This classification is important, as it determines the way in which the fluid will flow. This classification is based on a most important physical property “viscosity”.

Then main two types under this classification are:

> Newtonian fluid

> Non Newtonian fluid

A Newtonian fluid is the fluid, whose viscosity remains constant regardless of any applied stress. That’s why these fluids are also named as “linear viscous fluids”. The most common example of Newtonian fluid is water. The flow of water remains same, whether it flows alone, or in vigorously agitation condition. Its simplest meaning is that, the fluid will continue to flow, regardless of the forces acting on it. The Newtonian fluids behave according to following equation:

                                                            τ = µ (du/dy)

τ is the shear stress exerted by fluid

µ is fluid viscosity, constant for Newtonian fluids

(du/dy) is the velocity gradient, or the strain.

So for Newtonian fluid, according to the equation, the ratio of stress to strain is constant, there fore, the viscosity is constant.

The viscosity of the non Newtonian fluid is variable, and is dependent upon the applied stress on the fluid. These type of fluids also exhibits the rheological properties .The common examples of non Newtonian fluids are solution of corn starch and water, paints, ink, tooth paste, etc.

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Bleaching agents

Bleaching agents are the materials, which are used for the lightening, decolorizing or whitening of a substrate by the chemical reactions.  The color producing materials are generally organic in nature, containing“chromophores” (Chromophore is that portion of molecule that absorbs light photons).

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The bleaching action is normally based on the oxidation or reduction processes that degrade the color systems. Chemical bleaches works in one of two ways:

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Oxidizing bleach breaks the chemical bonds that make up the chromophores. Thus the molecule either does not contain the chromophore, or the chromophore does not absorb visible light.

.

Reducing bleach converts double bonds of the chromophoric carbonyl groups into textiles or pulp.

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The bleaching agents are mostly used for the following purposes:

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Textile bleaching: In textile process industries, these agents are used to remove the remaining unwanted materials (e.g. soil, colored compounds,etc) before dying and finishing. In textile process industries, the bleaching of the fabrics is generally named as “Scouring”, in which the washing of the fabric is carried out in hot alkali solutions.

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Pulp bleaching: bleaching agents are used to decrease the color of the pulp. The main use of this pulp bleaching is to make white paper from the pulp.

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Laundering purposes: normally alkaline aqueous solution of sodium hypochlorite is used for this purpose. This bleach is highly effective for fabrics whitening and germicidal activity, however not suitable for all fabrics.

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Cleaning purpose: Bleaching agents have extensive uses as hard surface cleaners, to remove strains, and also for the disinfection of the surfaces(industrial use). Sodium hypochlorite, hydrogen peroxides or many other alkaline solutions along with surfactants and auxiliaries are used for the purpose.

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Bleaching agents are also used for the bleaching of pulp and paper, hair, fur, foodstuff and oils.

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Bleaching agents are not considered as the environment damaging substances, as most of them are organic substances, however bleaching of the chemical substances or conventional bleaching using elemental chlorine produces large amount of chlorinated organic compounds such as chlorinated dioxins etc. Chlorinated dioxins are highly toxic, and have bad influence on human health.

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Bleaching agents

Bleaching agents are the materials, which are used for the lightening, decolorizing or whitening of a substrate by the chemical reactions.  The color producing materials are generally organic in nature, containing “chromophores” (Chromophore is that portion of molecule that absorbs light photons).

The bleaching action is normally based on the oxidation or reduction processes that degrade the color systems. Chemical bleaches works in one of two ways:

Oxidizing bleach breaks the chemical bonds that make up the chromophores. Thus the molecule either does not contain the chromophore, or the chromophore does not absorb visible light.

Reducing bleach converts double bonds of the chromophoric carbonyl groups into textiles or pulp.

The bleaching agents are mostly used for the following purposes:

Textile bleaching: In textile process industries, these agents are used to remove the remaining unwanted materials (e.g. soil, colored compounds, etc) before dying and finishing. In textile process industries, the bleaching of the fabrics is generally named as “Scouring”, in which the washing of the fabric is carried out in hot alkali solutions. 

Pulp bleaching: bleaching agents are used to decrease the color of the pulp. The main use of this pulp bleaching is to make white paper from the pulp.

Laundering purposes: normally alkaline aqueous solution of sodium hypochlorite is used for this purpose. This bleach is highly effective for fabrics whitening and germicidal activity, however not suitable for all fabrics.

Cleaning purpose: Bleaching agents have extensive uses as hard surface cleaners, to remove strains, and also for the disinfection of the surfaces (industrial use). Sodium hypochlorite, hydrogen peroxides or many other alkaline solutions along with surfactants and auxiliaries are used for the purpose.

Bleaching agents are also used for the bleaching of pulp and paper, hair, fur, foodstuff and oils.

Bleaching agents are not considered as the environment damaging substances, as most of them are organic substances, however bleaching of the chemical substances or conventional bleaching using elemental chlorine produces large amount of chlorinated organic compounds such as chlorinated dioxins etc. Chlorinated dioxins are highly toxic, and have bad influence on human health.

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Air Pollution because of process industries

[caption id="attachment_175" align="alignright" width="300" caption="Air pollution because of process industries"][/caption]

Being a chemical engineer, you must be aware of the hazards and outcomes of the un-managed and poorly handled processes in process industries. One of the major disadvantages of these poorly handled chemical processes is the Air Pollution. However energy generation is also considered as the major source of the air pollution.

In air pollution, the air is contaminated with several unwanted substances, which produces direct measurable effect on receptors [receptor may be humans, animals, plants or environment]. This situation becomes more dangerous when these substances react with other contents in the atmosphere and form other hazardous compounds, causing harmful phenomena like depletion of ozone layer, petrochemical smog, acid rains, or green house gases [generally known as global warming]. We will discuss these phenomena later, in detail.

The original six criteria pollutants, documented by EPA [environmental protection agency] are SO2 [sulfur dioxide], NO2 [Nitrogen dioxide], CO [carbon monoxide], O3 [ozone], suspended particles and VOC [volatile organic compounds]. As this is a serious issue against the global environmental protection, so EPA is trying to implement and make several changes in the clean air act.

The clean air act was first passed in 1956 by the parliament of UK,in response of the London smog 1952. This clean air act 1952 was used and effective till 1964, then there were several modifications in this act.

The 1970 clean air act required that EPA provide a safety margin to protect against hazardous air pollutants by establishing national emissions standards for certain sources.

This act was last amended in 1990,which contains national ambient air quality standards for pollutants which are harmful to receptors. This act identifies two types of national ambient air quality standards:

• Primary standards      : for public health protection.


• Secondary standards  : for public welfare protection.

However, it is also the duty of the process industries / organizations, to take serious steps to control air pollution. They must focus on the reduction of contaminant discharge

• by installing control equipments [scrubbers, gravity settling chambers, etc]


• by changing raw materials, operations, or modes of operations


• by diluting the discharge


• by dispersion of sources locations.

Out of all above, the installation of the pollution control equipments is the best option to go for.This is quite an expensive technique, but is very efficient and most of the industries are using these equipments to regenerate the chemicals from the waste stream, so that their process is highly optimized causing very less pollution.

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Air Pollution because of process industries

Being a chemical engineer, you must be aware of the hazards and outcomes of the unmanaged and poorly handled processes in process industries. One of the major disadvantages of these poorly handled chemical processes is the Air Pollution. However energy generation is also considered as the major source of the air pollution.

In air pollution, the air is contaminated with several unwanted substances, which produces direct measurable effect on receptors (receptor may be humans, animals, plants or environment). This situation becomes more dangerous when these substances react with other contents in the atmosphere and form other hazardous compounds, causing harmful phenomena like depletion of ozone layer, petrochemical smog, acid rains, or green house gases (generally known as global warming). We will discuss these phenomena later, in detail.

The original six criteria pollutants, documented by EPA (environmental protection agency) are SO2 (sulfur dioxide), NO2 (Nitrogen dioxide), CO (carbon monoxide), O3 (ozone), suspended particles and VOC (volatile organic compounds). As this is a serious issue against the global environmental protection, so EPA is trying to implement and make several changes in the clean air act.

The clean air act was first passed in 1956 by the parliament of UK, in response of the London smog 1952. This clean air act 1952 was used and effective till 1964, then there were several modifications in this act.

The 1970 clean air act required that EPA provide a safety margin to protect against hazardous air pollutants by establishing national emissions standards for certain sources.

This act was last amended in 1990, which contains national ambient air quality standards for pollutants which are harmful to receptors. This act identifies two types of national ambient air quality standards:

• Primary standards      : for public health protection.
• Secondary standards  : for public welfare protection.

However, it is also the duty of the process industries / organizations, to take serious steps to control air pollution. They must focus on the reduction of contaminant discharge

• by installing control equipments (scrubbers, gravity settling chambers, etc)
• by changing raw materials, operations, or modes of operations
• by diluting the discharge
• by dispersion of sources locations.

Out of all above, the installation of the pollution control equipments is the best option to go for. This is quite an expensive technique, but is very efficient and most of the industries are using these equipments to regenerate the chemicals from the waste stream, so that their process is highly optimized causing very less pollution.

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chloro-floro-carbons

[caption id="attachment_178" align="alignright" width="268" caption="cfc ozone"][/caption]

Chloro-floro carbons are member of halo alkanes [or alkyl halides], which belongs to the group of chemical compound, derived from alkanes, containing one or more halogens. These are generally used as refrigerants, solvents, fire extinguishers, and as pharmaceuticals.

Many haloalkanes, including chlorofluorocarbons are considered as the serious pollutants and toxins to the environment. In actual, CFC's are the hydrocarbons, fully halogenated with chlorine and fluorine, and in the presence of sun light, the chloro-floro carbon molecule breaks into chlorine and chlorodifloromethyl radical. I.e.

.

CCl₂F₂              ----------->        Cl             +            CClF₂

    _{dichlorodifloromethane                 chlorine atom}        chlorodifloromethyl redical   

.

Now this chlorine atom will react with ozone layer, causing ozone depletion, by converting ozone molecule to oxygen.

Cl         +            O₃      ----------->        ClO           +            O₂

_{chlorine atom           ozone                   chlorine monoxide         oxygen}  

_.

This depleted ozone phenomena is a serious issue to environment as well as human health considerations, because less ozone means lesser production towards the highly hazardous ultraviolet sun rays. That’s why; a ban was imposed on the use of CFC’s. However, these gases are still found in refrigerators and in some types of foam packaging.

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chloro-floro-carbons

Chloro-floro carbons are member of halo alkanes ( or alkyl halides), which belongs to the group of chemical compounds , derived from alkanes, containing one or more halogens. these are generally used as refrigerants, solvents, fire extiguishants, and as pharmaceuticals.

Many haloalkanes, including chloro-floro carbons are considered as the serious pollutants and toxins to the environment. In actual, CFC's are the hydrocarbons, fully halogenated with chlorine and fluorine, and in the presence of sun light, the chloro-floro carbon molecule breaks into chlorine and chlorodifloromethyl redical. i.e.

                                     CCl₂F₂               ----------->        Cl             +            CClF₂

                                 _{dichlorodifloromethane                               chlorine atom}             chlorodifloromethyl redical   

 Now this chlorine atom will react with ozone layer, causing ozone depletion, by converting ozone molecule to oxygen.

                                    Cl         +            O₃       ----------->        ClO           +            O₂

                                       _{chlorine atom                 ozone                            chlorine monoxide                    oxygen}  

_{This depleted ozone phenomena is a serious issue to environment as well as human health considerations. because less ozone means lesser protection towards the highly hazardous ultraviolet sun rays. That's why, a ban was imposed on the use of CFC's . however,} these gases are still found in refrigerators and in some types of foam packaging.

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coal, expected alternative fuel in future

Although, it is not a newer trend, to use coal as a fuel. There are many industries, which are using several technologies like gasification or the liquification of coal, to fulfill their fuel or energy needs. However, there are several environmental hazards in handling of coal , because of the high ash , or sulfur content of the coal.

The experts are trying to find the safe handling procedures for the safe use of this black gold. Recently, an Australian based team of researchers, including CSIRO and the university of new castle, has developed a way, to produce highly ash free coal, which can be used as a fuel for diesel engines.

for the purpose, the coal is slurried and micronized into fine sizes, less then 30 µm, to release the minerals from the coal, then by ultra fine flotation, the minerals are removed from the coal. The remaining coal slurry is called micronized refined coal (MRC).

After the study of the range of Australian coals, the team verified that for finely grounded coals, the flotation gives consistent low ash products with greater recovery of coal, then previous researches.

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coal, expected alternative fuel in future

Although, it is not a newer trend, to use coal as a fuel. There are many industries, which are using several technologies like gasification or the liquification of coal, to fulfill their fuel or energy needs. However, there are several environmental hazards in handling of coal , because of the high ash , or sulfur content of the coal.

The experts are trying to find the safe handling procedures for the safe use of this black gold. Recently, an Australian based team of researchers, including CSIRO and the university of new castle, has developed a way, to produce highly ash free coal, which can be used as a fuel for diesel engines.

for the purpose, the coal is slurried and micronized into fine sizes, less then 30 µm, to release the minerals from the coal, then by ultra fine flotation, the minerals are removed from the coal. The remaining coal slurry is called micronized refined coal (MRC).

After the study of the range of Australian coals, the team verified that for finely grounded coals, the flotation gives consistent low ash products with greater recovery of coal, then previous researches.

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what is heat exchanger

Heat transfer is considered as the basics of chemical engineering, and most important heat transfer equipment is the heat exchanger. A chemical engineer knows it very well that what is heat exchanger. Heat exchanger is the equipment used for effective transfer of heat between two fluids. These fluids are separated by means of solid wall, to avoid their mixing. The heat exchangers are the widely used equipments in chemical and process industries, So why a chemical engineer must have firm grip on heat exchangers designs, and their working. Most common application areas of them are boilers, condensers, intercoolers, preheaters , etc.

The heat exchanger performance is calculated by

                                                                                                 n = Q / Qmax 

  

where,
           n        =   performance or efficiency

           Q       =   actual rate of heat transfer

           Qmax    =   maximum rate of heat transfer

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what is heat exchanger

Heat transfer is considered as the basics of chemical engineering, and most important heat transfer equipment is the heat exchanger. A chemical engineer knows it very well that what is heat exchanger. A heat exchanger is the equipments used for effective transfer of heat between two fluids. These fluids are separated by means of solid wall, to avoid their mixing. The heat exchangers are the widely used equipments in chemical and process industries, So why a chemical engineer must have firm grip on heat exchangers designs, and their working. Most common application areas of them are boilers, condensers, intercoolers, preheaters , etc.

The heat exchanger performance is calculated by

                                                                     n = Q / Qmax 

  

where,
           n        =   performance or efficiency

           Q       =   actual rate of heat transfer

           Qmax    =   maximum rate of heat transfer

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Prepare stearic acid at home

Stearic acid is a usually a most common chemical, used in process industries , and it is quite expensive too. So it is not a difficult task for a a chemical engineer to prepare stearic acid locally at a very cheap cost.

• Just buy a natural soap bar ( try to get the most cheapest among all), this reaction will only work with the natural soap bar, so try to do the reaction on a little piece of soap initially.


• Dissolve the natural soap bar in hot water completely.


• Add food vinegar (but the food vinegar is needed in higher volume, so you can add any other acid , having PH less then 6).


• The stearic acid will precipitate as a layer of impurities on the surface of the mixture(scum). When the  scum settles down, then filter it, and drain the remaining liquor.

The best part of this reaction is that you will get the maximum quantity of stearic acid , i.e for every 100 gm of soap, you will get around 80 gm of stearic acid.

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Prepare stearic acid at home

Stearic acid is a usually a most common chemical, used in process industries , and it is quite expensive too. So a chemical engineer can try to prepare stearic acid at a very cheap cost. Just buy a natural soap bar ( try to get the most cheapest among all), this reaction will only work with the natural soap bar, so try to do the reaction on a little piece of soap initially. Dissolve the natural soap bar in hot water completely, and add food vinegar (but the food vinegar is needed in higher volume, so you can add any other acid , having PH less then 6). The stearic acid will precipitate as a layer of impurities on the surface of the mixture(scum). When the  scum settles down, then filter it, and drain the remaining liquor.
The best part of this reaction is that you will get the maximum quantity of stearic acid , i.e for every 100 gm of soap, you will get around 80 gm of stearic acid.

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a new safety course

I have just enrolled in the newer occupational safety course, starting from tomorrow for the five days, Its is a certified course named OHSAS 18001, which is definitely a beneficial course for a chemical engineer. So I am very much excited for that. Let's see what newer stuff of chemical engineering I am going to learn from there. I will definitely share my experience with you friends.

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