Monday, 27 February 2017

Principles of Thermodynamics for Engineering Applications

Introduction

Thermodynamics is a branch of science that explains energy and its transformation based on the physical state of the matter. The analysis of thermal activities is derived by means of energy conservation equations, which are based on the conservation of mass or the conservation of energy. Thermodynamic principles mainly depend either on the law of conservation of energy or the law of conservation of mass. Law of conservation of mass and energy equations and calculations are thoroughly reviewed in our FE exam review courses. 

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Thermodynamics Principles or Laws

· Thermodynamics First Principle: The most important law of physics is the conservation of energy. The first law of thermodynamics states that energy can move from one physical state to another during molecular interaction, but the total energy remains the same and cannot be destroyed. 

· Thermodynamics Second Principle: The second law of thermodynamics states that the entropy of any independent or isolated system always increases, and the actual process of work moves in the direction of low energy quality.

· Thermodynamics Third Principle: The third law of thermodynamics states that as the temperature reaches absolute zero, the entropy of a system tends to reach constant value. Therefore, the entropy of a system is zero at absolute zero temperature. 

· Thermodynamics Fourth Principle: The fourth law of thermodynamics states that if any two objects are in thermal equilibrium with the third object at the given time, then the heat transfer among the objects is “zero.” This principle is often referred to as the “zeroth principle.”

Working Principles of Thermodynamics

· System: a predefined medium to analyze thermodynamic activities; the complexity depends on the nature of the industry. The work is based on the quantity of matter and shape of the system. The boundary surface of the system is the layer between the system and its surroundings. 

· Systems are classified as the following:

1)Open System: If material or matter can navigate through the boundary surface to its surroundings, then it is considered an open system.

2)Closed System: If material or matter cannot pass through the boundary surface to its surroundings, then it is said to be a closed system. Isolated systems are considered a type of closed system where there is no interaction with a material’s surroundings.

The physical state of a system is defined by its properties and its values. The properties of a system change due to the working process of energy inputs and outputs during the period of transformation energy. Thermodynamic cycles have a series of processes that start and stop at the fixed state. It is necessary to understand the above-mentioned systems and laws for the Fundamentals of Engineering exam.

Energy Inputs and Outputs


Thursday, 23 February 2017

Economic Analysis for Sustainable Development of Professional Engineering Services

Introduction

Engineering economics is the process of forecasting the expenses or operating costs that must be incurred to manufacture a product or to provide a service. A cost analysis takes into consideration all the expenses that are involved in designing and manufacturing a product. A professional design engineer manages manufacturing costs, which requires physical data, whereas a cost estimate engineer compiles and applies the costing data to determine the final cost of the product. Engineers preparing for the FE exam should be familiar with engineering economic equations and calculations.

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Purpose of Cost Analyses 

Cost analyses play a significant role in the decision-making process that an engineer makes in selecting materials, methods, tools, and facilities. An understanding of the cost-estimation process is essential to ensure that decisions are based on reliable cost analyses. 

Quantity takeoff and unit costs must be reasonably accurate to finalize the actual product cost. If a product is overpriced, it will negatively affect business. It is always better to analyze competitor pricing strategies for the cost assessment of the product. Our FE exam review courses provide accounting principles and cost analyses for selecting the best alternative. 

Detailed cost estimates are prepared to:

· Determine the selling price of a product to ensure profit margin

· Examine the vendor’s quotations

· Check whether the product can be manufactured in house 

· Determine the most economical process to manufacture a product

· Initiate means of cost reduction in existing production facilities

· Determine standards of production performance to control costs

Cost Estimating or Costing

Costing is the process of listing all expenses incurred in various functional departments during product development. Accounting systematically records all expenses to determine the final cost of a manufactured product. The work of costing begins at the pre-planning stage and ends only after the product has been sold out or has been handed over to the project owner. 

Purpose of costing:

· To compare the actual cost with the estimated cost to understand whether the estimate had been realistic or not

· To find undesirable expenses that require corrective measures 

· To change the selling price due to variations in material cost or labor cost

· To find the reasons for a loss or profit 

· To formulate policies and plans for bidding on a new job

Differences between estimating and accounting:

· Estimating is the determination of the anticipated or probable cost of a product before production, whereas accounting is done only after production of the product has been completed

· Estimating is a highly technical job since the estimator should be well versed in factory methods, operation times etc. Costing consists of compiling data by an accountant

· Estimating provides predicted or standard costs; accounting gives actual costs

The above topics are covered in undergraduate engineering courses, but there is an opportunity to review the basics of estimating and accounting with School of PE’s Fundamentals of Engineering exam review courses.

Monday, 20 February 2017

Environmental Pollution: An Overview of Problems and Control Measures

Environmental Pollution 

Environmental pollution is the process of contaminating physical, chemical, and biological characteristics of natural air, land, and water resources. It is important for professional environmental engineers to understand the concept of environmental pollution.

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Causes of Environmental Pollution

It is public responsibility to care for and to sustain a healthy environment. An imbalanced environment creates numerous problems. The most common environmental problems generally include air or water pollution, soil erosion due to storm water runoff, depletion of natural resources, land fillings, and deforestation. 

Visualizing Environmental Problems 

Environmental problems are visualized in terms of intensity and growth of pollution, industrialization, and unplanned urbanization. Migration of populations to urban areas has also led to air, water, and noise pollution. Our PE Environmental exam review course recaps various sections of environmental engineering principles and practices to prevent pollution or contamination.

Classification of Pollutants

Pollutants are classified into two types:

· Biodegradable: breaks down by the activity of bacteria and enters biogeochemical cycles. Some examples of such pollutants include domestic household waste, sewage, and agricultural waste.

· Non-biodegradable: does not break down into simple and harmless products by bacteria. Examples include industrial chemicals, pesticides, metals (mercury, lead, arsenic), plastics, and radioactive substances.

Environmental Pollution Control Measures

· Flammable strong wastes must be burned in incinerators because strong waste is being changed into vaporous waste. Without an incinerator, the air would become contaminated. 

· Strong natural wastes, including fecal matter, must be changed over into fertilizer. The composting should be done in pits or in stacks of soil no less than 8-10 cm thick to prevent fly reproduction and rodent threats. 

· Materials that are not combustible, including cinder and glass pieces, should be discarded via landfills in low-lying ranges.

· Extreme and undesirable destruction of vegetation must be halted. Wipes and fabric towels should be used in place of paper towels. 

Topics related to environmental pollution control measures and methods are extensively covered on the PE Environmental exam. It is important for all engineers registered for the PE Exam to review environmental pollution concepts prior to the exam.

Tuesday, 14 February 2017

Wastewater Treatment Process for Public Health and Safety

Professional engineers who work with water resources are mainly concerned about water pollution due to the discharge of wastewater. To help prevent water pollution, the wastewater discharged from households and industries is treated. It is extremely important for environmental engineers preparing for their PE exam to understand the wastewater treatment process.

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The process of wastewater treatment consists of the following steps: 
1)Pre-treatment 
2)Preliminary treatment 
3)Primary treatment 
4)Secondary treatment 

Pre-Treatment Step

The pre-treatment process occurs prior to the discharge of wastewater into the treatment plant. It prevents the toxic chemicals or excess nutrients from being discharged into the wastewater. In this treatment method, water discharged from homes, commercial places, and industries enters the sanitary sewers, and water from rainwater enters the storm water sewers. The combined sewer system carries both sanitary waste and the storm water. In the pre-treatment method, the water moves toward the wastewater plant primarily by gravity flow. Therefore, it prevents sediment and suspended material.

Preliminary Treatment Step

In this treatment method, wastewater treatment is done by using bar screens and grit chambers, which remove large objects and nondegradable materials. 
  • Bar Screen 

The bar screen prevents large particles that have the entered sewer system from continuing in the flow of treatment. Such objects include bottles, pieces of wood, and any solid materials. 

Bar Screen 
  • Grit Chamber 

The grit chamber is a narrow tank that is designed to slow down the flow of the wastewater, so that solids, such as sand, will settle out of the water. Grit causes excessive wear and tear on pumps and other plant equipment, and therefore, it is recommended to remove grit periodically from the collection trap.

Grit Chamber
  • Mesh Screen Method 

Mesh screens collect diapers, towels, and plastic material. The size of a mesh screen varies and is optimized to remove solids. If the solids are not removed, then they enter the pipes of the treatment plant and cause damage and inefficiency to the process. 

Mesh Screen
The above methods are thoroughly discussed in principles and practice of engineering (PE) exam review courses for environmental engineers and water resources engineers.

Primary Treatment of Wastewater

The sewage water enters the plant for treatment and first flows through a screen for removing large floating materials. Large materials may clog pipes or damage treatment equipment. The water passes through the grit chamber where cinders, sand, and small stones settle at the bottom. 

The grit chamber is mostly used in plants having combined sewer systems where sand or gravel may wash into sewers along with storm water. The flow meter continuously records the volume of water entering the treatment plant. Biochemical oxygen demand (BOD) is a measure of the amount of oxygen required to aerobically decompose organic matter in the water. 

In this physical process, the wastewater flow is slowed down and allows suspended solids to settle at the bottom of the sedimentation tank. The suspended solids that settle at the bottom are called sludge or bio solids. 



The sludge from the primary sedimentation tanks is pumped into the sludge thickener. The primary treatment tank water is pumped to the trickling filter for secondary treatment. 

Secondary Treatment of Wastewater

This process utilizes the bacteria and algae to metabolize organic matter in the wastewater. It removes about 85% of the organic matter in the sewage by use of bacteria. The secondary treatment involves activation of sludge and a filtering process.

The effluent leaves the sedimentation tank and then flows or is pumped to the trickling filter. A trickling filter is a bed of stones from three to six feet deep through which primary treated water passes.


The sludge process rapidly speeds up the work of the bacteria by combining air and sludge with bacteria. After the sewage leaves the settling tank in the primary stage, it is pumped into an aeration tank. It is then further mixed with air and sludge loaded with bacteria and is left to set for several hours to break down the organic matter into harmless byproducts. The sludge is now activated with billions of additional bacteria and other tiny organisms. They can be used again by returning the bacteria to the aeration tank to be mixed with air and new sewage. To complete secondary treatment, the effluent from the sedimentation tank is then disinfected with chlorine before being discharged into receiving waters. Chlorination will kill more than 99 percent of the harmful bacteria in the effluent. Many states now require the removal of excess chlorine before discharging to surface waters by a process called dechlorination. Most of the above topics are covered in undergraduate environmental engineering courses. Wastewater treatment is an important exam topic for the PE Exam, so it is recommended to review the topic before taking the exam.

Monday, 6 February 2017

Computer Architecture and Organization Details

The Brief History of Computers

The Electronic Numerical Integrator and Computer (ENIAC) was the world’s first general-purpose digital computer. Because of the basic programming of the computer, the chore of entering and altering programs for the ENIAC was very difficult. To fix this problem, the Electronic Discrete Variable Computer (EDVC) was created to make programming much easier. These computers stored data instructions in their memory, making directions for various tasks easily obtainable when needed. The EDVCs followed the concept of stored-programs. The architecture of these computers included general purpose registers, the status word, the instruction set, and the address space. Today’s computers use multiple registers rather than a single accumulator and cache memory, which improves the performance of the CPU and enhances computer organization. Some of the registers used in CPUs are as followed: 

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Memory buffer register (MBR): Stores the data to be transferred to and from the immediate access memory. MBR stores copies of allotted memory locations specified by the memory address register. 

Memory address register (MAR): MAR is a CPU register that holds the address for the memory location of data. 

Program counter (PC): A register that holds the address of the next instruction that is to be executed. 

Instruction register (IR): Stores the location of the instruction being executed. 

Accumulator (AC): Holds the temporary operands and results in ALU operations. 

Instruction buffer register (IBR): Used to hold the temporary right-hand instructions from a word in memory. 

The above information is reviewed in the Computational Tools and Techniques topic in FE exam review courses.

Working Principle of Pipeline Processors

The pipeline is an effective way of organizing the parallel execution of an instruction into a computer system. When using a pipeline process, the processor receives its first instruction from its memory, performs the execution, and then moves to the next instruction to be executed from memory. This process is repeated until the task is complete. While fetching an instruction, the arithmetic fragment of the processor is idle. While using a pipeline in the processor, the processor allows the next instruction to be fetched while the CPU is performing arithmetic operations, holding the process data in a buffer until each operation is performed. The fetching of the next instruction is a continuous process. Flowcharts and simple programming techniques are discussed in our Fundamentals of Engineering exam review courses.

The Role of Cache Memory in Pipeline Process

Cache memory is an additional memory system that temporarily stores frequently-accessed instructions and data for faster processing by the CPU of a computer. Both the main memory and cache are internal and randomly-accessed memories that use semiconductor-based transistor circuits. The cache holds a copy of frequently-used data or program codes that are stored in the main memory. The key purpose of cache memory is to store program instructions that are frequently referenced by software during specific processes. This process and concept of computational tools and techniques is important for FE exam preparation. Most of the topics related to spreadsheets and calculations are also reviewed in our FE exam review courses.

Monday, 30 January 2017

Pros and Cons of Using Water and Steam as a Heating Medium in Heat Exchangers

Although water is abundantly available for commercial use, it contains various minerals that create corrosion and scaling in heat exchangers. The process of scaling adversely affects heat transfer and can lead to equipment failure. Chemical treatment is required to prevent corrosion and scaling deposits. Microbiological fouling is also an important factor when selecting water as a heating medium in heat exchangers. Properties of water and the functionality of heat exchangers are reviewed in PE exam prep courses.

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Steam is used as a heating medium in heat exchangers. Pressure steam is classified as low pressure steam and high pressure steam. Low pressure (LP) steam carries more latent heat, is normally of higher quality, reduces scaling, and reduces the fouling factor. LP steam typically requires pressure reducing values, which require more space and require large pipes for condensation. The space requirement and size of the pipes add maintenance and operational costs. High pressure (HP) steam requires smaller pipes and has a lower installation cost than LP steam piping. Professional Mechanical engineers design and create drawings of piping systems prior to installation. Our PE Mechanical exam review course offers a thorough refresher of HVAC principles and topics related to heat exchangers.

Water vs. Steam as a Heating Medium 

  1. Water does not change state while it is being used as a heating medium. As it gives up heat energy to the secondary medium, its temperature drops. If one pound of water drops one degree Fahrenheit in temperature, it produces approximately 1 British thermal unit (BTU) of heat. 
  2. Steam also does not change state while it is used as a heating medium, and it gives up heat energy to the secondary medium. During the process, its temperature drops, but the fluid condensate remains at the same temperature. One pound of steam at a pressure of 30 psi gives up approximately 929 BTUs of heat. Steam gives up more energy per unit mass than water. 

Factors That Influence Heat Transfer Rates

The following factors influence heat transfer rates: 
  1. Surface area 
  2. Temperature 
  3. Flow characteristics 
  4. Fouling/Scaling 
  5. Film coefficient of fluid 
  6. Thermal conductivity of metal 

How to Find Rate of Heat Transfer

For fluids that change state, the rate of heat transfer “Q” is given by:
Q = W*C* Temperature change of the fluid (∆T) + W* Latent heat of vaporization (∆H) 
W = Flow rate of fluid (kg/hr.)
C = Specific heat of fluid (BTU/kg/degrees C)
∆T=Temperature change of the fluid (degrees C)
∆H = Latent heat of vaporization (Btu/kg)

For fluids that do not change state, the rate of heat transfer “Q” is given by:
Q = W*C * Temperature change of the fluid (∆T)

If the rate of heat transfer is higher, then the heat exchanger’s efficiency is higher and vice versa.

The above equations are important for engineers who plan to take the Principles and Practice of Engineering (PE) exam for their career advancement.

Tuesday, 24 January 2017

An Introduction to Welding from a Structural Engineering Perspective

Introduction

Welding is the process of joining metals in which the parent metals are fused together to form a single piece. Welding is used wherever strength is required, whereas soldering and brazing are primarily employed to handle only light loads. Structural engineers require knowledge of the welding process because many structural frames require field welding during assembling operations. Professional structural engineers preparing for their SE exam certification need the technical knowledge of various welding procedures. 

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Uses of Welding

Welding is: 
  1. A substitute for castings and forgings 
  2. A fabrication medium to join parts permanently and to form built up members 
  3. A connecting medium, in lieu of nuts and bolts 
  4. A repair medium to replace broken and worn out sections of members 

Types of Welded Joints

Welded joints are classified based on the welding method needed. Some examples include the following: butt, lap, strapped, tee, fillet, square butt, single and double V butt, single and double U butt, single and double bevel butt, single and double J butt, and corner joints. Technical and functional aspects of each joint are reviewed in SE exam review courses


Comparison of Riveted Joints and Welded Joints

When compared to riveted joints, welded joints are: 
  1. Lighter in weight 
  2. Stronger as there is no weakening of section due to punching or drilling 
  3. Laborless as several operations, such as punching, drilling, riveting, fullering, or caulking are replaced by a single operation, namely welding. 


Properties of Welding Materials

Many materials can be welded, but the ease of welding varies depending on the material. At a high temperature, the structure of a material changes, as well as the physical properties and corrosion resistance of the material. Gaseous oxides cause blow holes, soluble oxides in the molten metal reduce the strength of the weld, and insoluble oxide causes slag inclusion in the weld. 
  1. Metals, such as zinc, may vaporize and cause the weld to be more porous 
  2. Metals of high thermal expansion and low thermal conductivity are subjected to high cooling stress as the metal cools after welding 
  3. All carbon steels, except for spring steel and tool steel, can be welded satisfactorily, but the low carbon steels are most readily welded 
  4. Cast iron is difficult to weld, but satisfactory welds can be produced if due care is taken while pre-heating prior to welding 


Welding Processes for Different Metals

Arc welding, submerged arc welding, and electro-slag welding methods are employed for welding ferrous metals, as the gas welding process is used for welding metal alloys such as brass and bronze.

Types of welding processes, welding joints dimensions, and welding angle specifications are very important for professional engineers who plan to take the structural engineering certification exam.