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.

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.

Table of Contents

1. Water vs. Steam as a Heating Medium

2. Factors That Influence Heat Transfer Rates

3. How to Find Rate of Heat Transfer

1. 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.

2. 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

3. 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.

An Introduction to Welding from a Structural Engineering Perspective

Table of Contents

1. Introduction

2. Uses of Welding

3. Types of Welded Joints

4. Comparison of Riveted Joints and Welded Joints

5. Properties of Welding Materials

6. Welding Processes for Different Metals

1. 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.

2. 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 

3. 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. 

4. 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. 

5. 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 

6. 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.

Corrosion Protection for Steel in RCC Bridge Structures

Table of Contents

1. Introduction

2. Corrosion Control Measures

3. Corrosion Control Methods

4. How to Prevent Corrosion of Steel in Concrete

5. Techniques Used for Protection of Reinforced Steel Against Corrosion

1. Introduction

Corrosion is the wearing of a metal due to a chemical or an electro-chemical reaction by its surroundings that indicates the damage and loss of material due to a chemical attack. In this process, metal is converted into an oxide, salt, or some other compound that may lead to the development of rust. 

The implementation of corrosion protection is a new construction technique to avoid the loss of materials through corrosion. Corrosion protection uses corrosion inhibitors, low-permeability concrete, and coated reinforced steel that considerably reduces the amount of reinforced steel corrosion in new bridges.

2. Corrosion Control Measures 

Concrete provides a protective environment for steel to avoid corrosion. Due to high alkalinity, the thin passive film of ferric-oxide (Fe2O3) is automatically formed on the surface of steel. This layer effectively protects the steel from corrosion and will stay effective as long as the material maintains a high alkalinity. Therefore, by preserving an alkaline environment, the corrosion of steel can be effectively prevented, and the durability of the structure can be ensured. The alkaline medium must be maintained for a longer period by making the concrete impermeable. The factors that impact the corrosion of reinforcing steel bars that are embedded in concrete depend on the amount of chloride ions in the concrete, the resistivity of the concrete, temperature, and the concrete microstructure. Structural material characteristics of rebars and cement concrete topics are reviewed in SE exam review courses. 

3. Corrosion Control Methods

Mechanical Methods: The physical barriers that prevent the access of chlorides, oxygen, and moisture to the reinforcing steel.

Electro-Chemical Methods: This method forces the steel reinforcing bars to be cathodic. It includes chloride extraction and protection.

The above methods are widely used for preventing corrosion; a qualified structural engineer with their structural engineering exam certification will recommend the implementation method for each project.

4. How to Prevent Corrosion of Steel in Concrete

A major issue of a reinforced concrete structure is deterioration. The cost of repairing deteriorated structures has become a major liability for highway agencies. The primary cause of deteriorations is cracking, spalling, and delamination. To minimize the development of corrosion of steel in concrete, the following steps should be taken: 

• Avoid heavily congested reinforcements at the intersection of beams and columns 
• Avoid the use of materials that speed up the process of corrosion 
• Clean rebars to remove rust scales before placing concrete 
• Provide cathodic protection to the steel 
• Use high quality and impermeable concrete, as well as an accurate water-cement ratio 

The above quality control and assurance measures are refreshed in SE exam review courses for engineers who are interested in becoming a certified professional structural engineer.

5. Techniques Used for Protection of Reinforced Steel Against Corrosion 

Protection techniques are used to improve the adhesion of epoxy coatings to steel. One method involves pretreatment of uncoated steel with zinc chromate. This procedure is used for all epoxy-coated reinforcement. Epoxy-coated reinforcement steel is one of the protection systems for new bridge deck construction. Calcium nitrite [Ca(NO2)2] is the most popular inorganic corrosion inhibitor, and it is used to prevent chloride ion reactions on steel surfaces. The use of a corrosion-inhibitor admixture in the concrete provides adequate corrosion protection.

The Importance of Networking and Communication Systems in Electrical Engineering

Table of Contents

1. Routing and Transmit Design in Computer Networks Terms

2. Network Protocol Used for Data Transmission

3. Advantages of Computer Networking

4.Challenges of Networking

1. Routing and Transmit Design in Computer Networks Terms 

A router is defined as a network connected with two or more computers to share resources. These networks can be linked through cables, radio waves, satellites, or infrared light beams. 

Network topology is the arrangement of a network, how the nodes are connected to each other, and their communication methods with other nodes in the same network. 

Network optimization problems include routing restrictions, traffic load, overall reliability, and cost. The electrical industry is focused on network development and optimization. 

Routing and network topologies topics are refreshed in PE review courses for electrical engineers. 

2. Network Protocol Used for Data Transmission 

Protocol is a set of rules that manages the communication between computers on a network. These rules provide the guidelines that regulate the access, allowed physical topologies, speed of data transfer, and types of cabling used for transmission. The most common protocols are: 

Ethernet: Carrier sense multiple access/collision detection (CSMA/CD) access method is used in Ethernet protocol. This protocol listens to the network cable before sending any transmission through the network to avoid collision. When a computer knows that the network is free and there is no traffic on the network, data will then be transmitted. Otherwise, each system waits until the cables are clear before transmitting data. 

Local Talk: This protocol was developed by Apple and is considered carrier sense multiple access/collision avoidance (CSMA/CA). Local Talk adapters and a twisted pair cable is used to connect a series of computers through the serial port. 

Token Ring: In the mid-1980s, IBM developed this protocol. This protocol uses the token-passing method, where computers are connected through network so that the tokens travel around the network from one computer to another in a ring. If a computer does not have the information to transmit, it simply passes the token. If the computer needs to transmit the data, it attaches the data to the token. 

Asynchronous Transfer Mode (ATM): ATM is a universal networking technology that handles audio, video, and data transmission. It creates a virtual channel (VC) and utilizes the channel for communication and then terminates it. This can be implemented by one or more ATM switches; it places an entry for the VC in its forwarding table. 

3. Advantages of Computer Networking 

1. When using a network, people can communicate efficiently with a group of people through instant messaging, video conferencing, social media, chat rooms, etc. 
2. It is easy to share files, data, and information. This can be beneficial for large organizations to maintain their data in an organized manner and easily sort based on preference. 
3. The files and programs on a network can be protected using passwords. The protected files cannot be accessed by any unauthorized users.

4. Challenges of Networking 

1. Networks may sometimes crash or breakdown due to an issue with the server. When this kind of issue becomes frequent in networks, it could cause a loss of funds as well as a decline in productivity. It is necessary to maintain the network properly to prevent disastrous breakdowns. 
2. It is very expensive to build a network in large scale organizations. Cables and other hardware costs are very costly to buy and replace. 
3. Security threats are a major issue in large networks. Careful measures must be taken to facilitate the required security.

Professional electrical and computer engineers may have studied topics related to computer networks, communications, computer systems, and software development during their undergraduate studies. PE exam review courses recap these topics once again for engineers who are preparing for their professional engineer exam certification.

Geotechnical Investigation Methods and their Importance in Civil Engineering

In spite of differences in using various geotechnical testing methods and equipment by geotechnical engineers around the globe, there are set of acceptable standards and the required number of tests and testing procedures that are recommended prior to the construction at the project site. Project site investigation and inspection is one the major project management tasks. Soil boring methods, material testing, and ASTM standards and procedures are important in PE exam preparation.

In civil engineering professional practice, compromising with short cut methods of investigation procedures can maximize the risk of structural durability and life. Therefore, it is always recommended to perform appropriate and accurate soil investigations to reduce the risks and failures. Department standards and quality assurance investigation procedures required to be followed for minimizing the risks and improving the overall engineering performance of the structure. It is an engineer's responsibility to implement the ASTM specified standards and testing codes along with skills and techniques for adopting the best engineering practices to meet the emerging needs of construction activities in the engineering environment. The geotechnical engineers and their engineering skills ensure better foundations, good transportation facilities and safe infrastructure for public facilities.

Geotechnical engineering is an important and critical topic for the Professional Engineering exam in civil engineering. This engineering section requires application techniques and testing skills, recommended equipment and qualified personnel. The above mentioned key areas are necessary to fulfill the requirements of geotechnical engineering attributes for the economical design and construction, for maximum life of the structure, environment friendly infrastructure that could serve for generations. 

The employment of an enormous amount of resources for adopting the geo-technical challenges are the major essentials in the construction engineering industry. Many big projects require all sub disciplines of civil engineering for better outcome. However, the implementation of selective geotechnical investigative methods in designing major projects in seismic zones, high-rise structures in sandy soils, atomic power stations and for projects requiring 100% disaster-free facilities. 

The geo technical engineering area has huge scope to provide the safe, and quality projects for public and also for infrastructure advancement. Business developments, public and economic growth in all countries across the globe compounded with a shortage of quality procedures and standards Therefore, the need of implementing quality assurance and quality control procedures by professional civil engineers with a PE exam certification than ever before.

Digital Signal Processing in Electrical Engineering

Table of Contents

1. An Introduction to Signal Processing

2. Digital Signal Processing Applications

3. Digital Signal Processing Applications - Engineering Devices

4. The Components of Digital Signal Processing

5. Digital Signal Processor Performance

An Introduction to Signal Processing

Signal processing is an emerging technology that incorporates the fundamental theory, algorithms, processing, and transferring information in different patterns, which is broadly designated as signals. Transmission of information, or signals, is done through a channel. The digital signal processor consists of anti-aliasing filter and analog to digital and digital to analog converters. Analog, frequency, and digital modulations are various aspects of transmission. The concept of signal processing is a part of the FE exam syllabus, and it is reviewed in most FE exam prep courses. The main goal of signal processing applications is to be efficient and perform reliable transmission, display of information, and storage. 

Digital Signal Processing Applications

Audio compression, digital image processing, compression of videos, speech processing and recognition, digital communications, radio detection and ranging systems, seismology, and sound navigation and ranging systems are examples of digital signal processing applications. The implementation of digital signal processing is based on the requirements of the application. 

Digital Signal Processing Applications - Engineering Devices 

Radar is an object-detection system; it uses radio waves to control the range, angle, or velocity of objects. Radar is used to transmit radio signals at distant objects and analyze the reflection. Radar is used for air-traffic control to avoid mid-air collision and to predict weather conditions. Radar is also used in meteorology to aid in forecasting the weather. 

Sonar is an application of digital signal processing (DSP); sonar uses sound propagation to navigate and communicate with or detect an object under the surface of the water. Generally, two types of technologies are used in sonar: passive sonar and active sonar technologies. Passive sonar is used to listen to the sound of the vessels; active sonar is used to release pulses of sounds and to listen to echoes. Sonar may also be used for acoustic measurements.

The Components of Digital Signal Processing 

Computation: performs mathematical operations and processes by accessing the program from the program memory and the information stored in the data memory.

Data Memory: stores the information to be processed and works with program memory.

Program Memory: stores the programs; the processor uses the program memory to compress or manipulate data.

Input/Output Ports: used for data processing and analysis.

Digital Signal Processor Performance 

The most important challenge in executing DSP algorithms is transferring the data from the memory. The goal of digital signal processing is to measure, filter, and compress analog signals. General-purpose microprocessors can execute digital signal processing algorithms successfully. DSPs use a special memory architecture that can fetch multiple data and instructions at a time. DSP processors execute one instruction per clock cycle in complex or multi-operation type of instructions. These processors include a single multiplier or MAC unit and ALU unit. DSP processors show good performance even at the modest power and memory usage. Digital signal processing is one of the courses taught in undergraduate electrical engineering, and it is reviewed in fundamentals of engineering exam prep courses for those taking the FE exam.

Significance of Solar Energy in Power Generation for Mechanical Engineering Operations

Table of Contents

1. Introduction

2. Arrangement of Solar Power Panels

3. Utilization of Solar Power Panels for Mechanical Engineering Applications

1. Introduction

The sun emits very high, intensive energy in the form of solar radiation. The energy emitted by the sun in three minutes is equal to the world's energy consumption during a year. Most of the energy we receive from the sun is in the form of light by short-wave radiation, which is visible light to the human eye. When this radiation strikes a solid or liquid, it is transformed into heat energy. Within the past several years, solar panels have become increasingly popular as energy-saving devices that use this ideology. Solar panels are flat plate collectors that are used to collect solar energy. Solar energy has many uses including water pumping, solar heaters, solar driers, and solar power generation. 

2. Arrangement of Solar Power Panels 

In a flat-plate collector, radiation energy from the sun falls on the flat surface coated with a solar film. This surface has a high absorbing capacity and is placed toward the general direction of the sun for maximum efficiency. The materials used for the plates are copper, steel, or aluminum, and the thickness of the plate is approximately 1 to 2 mm. When evaluating the mechanics of a copper plate, thermal energy is transformed from the absorber plate to a fluid, which is then distributed in the copper tubes through the flat-plate collector. Panels are designed to have thermal insulation, with the preferred material being fiber glass behind the absorber plate to prevent heat loss from the rear surface. Engineering materials and their properties are important for the PE exam. Many PE review courses stress this topic.

3. Utilization of Solar Power Panels for Mechanical Engineering Applications

The solar panel collector reflecting surface is considered parabolic. The solar energy falling on the collector surface is focused on the absorber tube. When a large quantity of energy falls on the collector surface, it results in the temperature of the absorber liquid being higher than the flat plate collector. The flat-plate collectors may be used to heat water up to 80 degrees Celsius; the concentrators are designed to heat water from a medium temperature to high temperatures. The heated water in the flat plate solar collector is used for boiling butane under high pressure in the butane boiler; the boiling point of butane is about 50 degrees Celsius. The butane vapor, which is part of solar power plant arrangement, is used to run the steam turbine. This results in electricity. 

PE mechanical engineering review courses cover the principles of turbines and boilers. Qualified mechanical or electrical power plant engineers with professional engineering licenses can install and setup solar power plants for mechanical engineering applications.

Advantages of Solar Energy

1. The sun is an infinite source of energy, so solar energy is inexhaustible and renewable and available all over the world. 
2. It is environmentally clean and pollution free. 
3. It is the best alternative for the rapid depletion of fossil fuels. 

Disadvantages of Solar Energy 

1. The intensity of solar energy on sunny days is approximately 1.1 KW/square meter area. Therefore, a very large collecting area is required. 
2. Collecting solar energy creates a need for a large amount of land. 
3. Solar energy is not available at night or on cloudy or rainy days.