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Copy of HVAC Final Project

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mushtaq shah

on 30 January 2013

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Transcript of Copy of HVAC Final Project

Group15 HVAC Graduation Project HVAC Introduction to HVAC Boilers Heat Exchangers Air Handling Unit Fan Cooling Coil CFD Analysis Building Management System Introduction To HVAC Heating, ventilating, and air conditioning is based on inventions and discoveries made by Nikolay Lvov, Michael Faraday, Willis Carrier, Reuben Trane, James Joule, William Rankine, Sadi Carnot, and many others.
The starting point in carrying out a heat estimate both for cooling and heating will depend on the ambient and inside conditions specified. However before taking up the heat load calculation, it is necessary to find fresh air requirements for each area in detail, as pressurization is an important consideration.
The HVAC industry was historically regulated by the manufacturers of HVAC equipment, but Regulating and Standards organizations such as ASHRAE. Background Ashrae Comfort zone: For millennia, people have used fire for heating. Initially, the air required to keep the fire going ensured adequate ventilation for the occupants.
By the 1880s, refrigeration became available for industrial purposes.
Initially, the two main uses were freezing meat for transport and making ice.
However, in the early 1900s there was a new initiative to keep buildings cool for comfort. Cooling the New York Stock Exchange, in 1902, was one of the first comfort cooling systems. Comfort cooling was called “air conditioning.”
Our title, “HVAC,” thus captures the development of our industry. The term “air conditioning” has gradually changed, from meaning just cooling, to the total control
of:
• Temperature
• Moisture in the air (humidity)
• Supply of outside air for ventilation
• Filtration of airborne particles
• Air movement in the occupied space Historical review to the HVAC systems Carrier, The Father of Air Conditioning. The textbook Principles of Heating, Ventilating, and Air Conditioning, starts with a concise and comprehensive history of the HVAC industry.
HVAC evolved based on:
• Technological discoveries, such as refrigeration, that were quickly adopted for food storage.
• Economic pressures, such as the reduction in ventilation rates after the 1973
energy crisis.
• Computerization and networking, used for sophisticated control of large
complex systems serving numerous buildings.
• Medical discoveries, such as the effects of second hand smoke on people, which influenced ventilation methods. Historical review to the HVAC systems Before starting to design a system, it is critical that you know what your system is to achieve.
Often, the objective is to provide a comfortable environment for the human occupants, but there are many other possible objectives: creating a suitable environment for farm animals; regulating a hospital operating room; maintaining cold temperatures for frozen food storage; or maintaining temperature and humidity to preserve wood and fiber works of art. What is your system to achieve? 1) Heating 2) Ventilation 3) Air Conditioning For the last 20 to 30 years, manufacturers of HVAC equipment have been making an effort to make the systems they manufacture more efficient. This was originally driven by rising energy costs, and has more recently been driven by increased awareness of environmental issues. In the USA, the EPA has also imposed tighter restrictions. There are several methods for making HVAC systems more efficient. 4) Energy Effeciency Geothermal heat pumps are similar to ordinary heat pumps, but instead of using heat found in outside air, they rely on the stable, even heat of the earth to provide heating, air conditioning and, in most cases, hot water. The heat extracted through a geothermal heat pump can come from any source, despite the temperature. However, the warmer the source of heat, the more energy efficient it will be. [11] From Montana's −70 °F (−57 °C) temperature to the highest temperature ever recorded in the U.S.—134 °F (56.7 °C) in Death Valley, California, in 1913—many parts of the country experience seasonal temperature extremes. A few feet below the earth's surface, however, the ground remains at a relatively constant temperature. Although the temperatures vary according to latitude, at 6 feet (1.83 m) underground, temperatures only range from 45 to 75 °F (7.2 to 23.9 °C).
While they may be more costly to install than regular heat pumps, they can produce markedly lower energy bills—30 to 40 percent lower, according to estimates from the U.S. Environmental Protection Agency. 5) Geothermal Heating Pump Energy recovery systems sometimes utilize heat recovery ventilation or energy recovery ventilation systems that employ heat exchangers or enthalpy wheels to recover sensible or latent heat from exhausted air. This is done by transfer of energy to the incoming outside fresh air. 6) Ventilation energy Recovery Air cleaning and filtration is an important factor of our indoor environment because cleaning the air filters out what the lungs cannot by removing particles, contaminants, vapors and gases from the air. The filtered and cleaned air then is used in heating, ventilation and air conditioning. Air cleaning and filtration should be taken in account when protecting our building environments 7) Air Filtration and Cleaning Boilers Boiler definition A cast-iron, steel or copper pressure vessel heat exchanger, designed with and for fuel burning devices and other equipment to:
Burn fossil fuels (or use electric current)
Transfer the released heat to boilers (in water boilers) or to water and steam
(in steam boiler). Classification of Boilers Fire tube Boilers Is a boiler in which the products of combustion pass through the tubes, which are surrounded by water, the body of the boiler is called shell and it contains water.
Boilers are classified according to the:
Position of the furnace
Layout position
Flue gas travel
Type of firebox Water tube Boilers Water tube boilers are classified according to:
Tube and drum configuration
Water circulation
Working pressure and temperature
The state of the output medium (steam or water)
Fuel used Boiler Selection Boiler Type
Fire tube boiler
Water tube boiler
Cast iron boiler
Electric boiler
Steam or hot water
Size
Fuels
Number of Boilers
Payback Analysis The Most common Heating Boilers Fire tube boilers are often the choice for HVAC applications for heating. These boilers are used mainly for steam or water heating systems. Fire tube boilers are generally of the low pressure type , either 30 psi (2 bar) hot water or 15 psi (1 bar) steam with a maximum working temperature of 250 f (121 C). The efficiencies of modern fire tube designs have increased to about 80-85%.
The most popular type is the scotch marine boiler in which the combustion furnace is in the shape of a cylinder surrounded by water.

Scotch boilers come in two, three and four gass pass designs. Advantages of the scotch boiler include the ability to respond to rapid load swings due to the large volume of stored water/steam in the shell, low initial cost, low maintenance costs, and general ease of control. Disadvantages include the difficulty of producing superheated steam and pressure and capacity limitations. Boiler losses GCV Loss
There is a difference in the gross calorific valve (GCV) - theoretical ; and
Nett Calorific Valve (NCV) - actual of fuel. This is because of two reasons.
The fuel contain moisture and when burnt, first the heat, makes the
moisture in fuel evaporate and then the heat is used to heat water.
The fuel contains hydrogen, which also has to be burnt In furnace oil
(FO) the difference (loss) between GCV and NCV is 6.25%
(typically).

Stack Loss
The flue gases lost to the atmosphere from chimney is called the stack loss.
(The chimney is called stack as earlier bricks were stacked to make a
chimney). It is a function of the _T between the temperature of the flue
gases (Tg) and the ambient temperature (Ta). Stack loss is dependent on the
difference (Tg – Ta). Stack losses can be as high as 10%, or be optimized to
about 5%.

Radiation Loss
Even though the boiler surface is insulated with 3''- 4'' of insulation material,
there is still a radiation loss taking place. In a lot of older boilers, in fact, the
insulations may be old & not working. Typically, based on boiler loading,
radiation loss is 1-4%. Common Problems The empty tank problem which usually it is the initiate indication that the
machine will not run properly.
A clogged up burner filter is another boiler burner problem, In which case the
heating system can no longer serve the purpose it was bought.
A loosened burner is another major problem. When this happens, the flame
from the burner changes its color from blue to orange.
If the boiler burner trips can't be reset Common precautions Clean the filter
Check the valves Heat Exchanger • Definition :


A heat exchanger is a device that is used to transfer thermal energy (enthalpy) between two or more fluids, at different temperatures and in thermal contact


• Purpose :

1-it used as evaporative or a condenser


2-it is used as a heat recovery Examples :

a- No heat source
Condenser
Automobile radiator
Vaporator
Air pre heaters
Cooling towers
b-with heat source
Boilers
Fired heaters Main components of heat exchangers 1. Core
2. Matrix containing the heat transfer surface
3. Fluid distribution elements such as headers
4. Manifolds
5. Tanks
6. Inlet and outlet nozzles or pipes or seals


According to:

1. Transfer Processes
2. Number of Fluids
3. Surface Compactness
4. Construction features
5. Heat Transfer Mechanisms
6. Flow arrangement Classifications

Heat exchangers are classified according to transfer processes into indirect- and
direct contact
types.








A-Indirect-Contact Heat Exchangers
B-Direct-Contact Heat Exchangers
In a direct-contact exchanger, two fluid streams come into direct contact,
exchange heat, and are then separated.


A-Two fluids
B-Three fluids
C-Greater than three fluids 2.Classification According to Number of Fluids: 1.Classification according to transfer processes: 3.Classification According to Surface Compactness: 4.classification According to Flow Construction Features: Plate type heat exchangers 6.Classification According to Flow Arrangements: 5.Classification According to Heat Transfer Mechanisms: Fouling Fouling effects:

A-Increased capital investment
B-Additional operating costs
C-Loss of production

Types of fouling:
A-Particulate fouling
B-Chemical reaction fouling Heat Exchanger typeShell and tube Hex.
Number of Passes 3
Number of tubes Ntot 66
Tube length Ltube m 1.2
Tube outer diameter dout m 0.018
Tube inner diameter din m 0.0162
BWG 20
Shell length Lshell m 1.5
Shell Diameter dshell m 0.425
Shape factor 3.48
Tube Material. K=180.25 w/m2k
Al 2024 – T6 (4.5 % Cu, 1.5 % Mg, 6 % Mn)
Pressure drop in Hex. 0.50 bar Heat Exchanger Calculation Results Air Handling Unit Air Handling Unit AHU Is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. An air handler is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers Thermal Comfort Thermal comfort is primarily controlled by a building’s heating, ventilating and airconditioning systems, though the architectural design of the building may also have
significant influences on thermal comfort. Factors Influencing Thermal Comfort Seven factors that affect thermal comfort:-
Activity Level
Clothing
Occupant’s Expectations
Air Temperature
Radiant Temperature
Humidity
Air Speed Ventilation and Indoor Air Quality In this part we will be discussing additional factors that affect comfort and activity.
Indoor Air Quality, IAQ. The maintenance of indoor air quality (IAQ) is one of the
major objectives of air-conditioning systems because IAQ problems are a significant
threat to health and productivity.
The factors that influence pollutant and contaminant levels in buildings :
• The sources of pollutants.
• The ways pollutants can be absorbed and re-emitted into the building spaces.
Ways of maintaining good IAQ by :
• Controlling the source of pollutants within the space.
• Using filters to prevent pollutants and contaminants from entering the space.
• Diluting the pollutants and contaminants within the space. Indoor Air Quality Effects on Health and Comfort It is useful to think of contaminants in terms of the following classes of effect
Fatal in the short term
Carcinogens
Health Threatening
Annoying, with an Impact on Productivity and Sense of Well-Being Zones A space is a part of a building that is not necessarily separated by walls and floors.
A space can be large, like an aircraft hanger, or small, like a personal office.
A zone is a part of a building whose HVAC system is controlled by a single sensor.
The single sensor is usually, but not always, a thermostat. Zoning Design
Zoning Design Considerations
Interior and Roof Zones
Thermal Variation
Ventilation with Outside Air
Time of Operation
Pressure
Controlling the Zone The Thermostat Location In the following we will discuss the effect of location of the thermostat.
• Mounting the thermostat in a location where the sun can shine on it will cause
it to overcool the zone when the sun shines on it. The sun provides
considerable radiant heat to the thermostat.
• In many hotels, the thermostat is mounted by the door to the meeting room. If
the door is left open, a cold or warm draft from the corridor can significantly,
and randomly, influence the thermostat.
• In some conference or assembly rooms, the thermostat is mounted above
lighting dimmer switches. These switches produce heat that rises up into the
thermostat. This makes the thermostat think that the room is warmer than it
actually is.
• Mounting a thermostat on an outside wall can also cause problems. If the wall
becomes warm due to the sun shining on it, the thermostat will lower the air
temperature to compensate. This offsets the increased radiant temperature of
the wall on the occupants, but usually the effect is far too much and the room
becomes cool for the occupants. In a similar way, in the winter the wall
becomes cool and a cool draft will move down the wall over the thermostat,
causing it to raise the air temperature to compensate.
• If the thermostat is mounted where it is directly affected by the heating or the
cooling of the space, it will likely not maintain comfortable conditions.
For example, let us imagine that the air-conditioning system air-supply blows
directly onto the thermostat. In the heating mode, the thermostat will warm up
quickly when the hot air stream blows over it. Therefore, it will quickly
determine that the room is warm enough and turn off the heat. The result will
be rapid cycling of the thermostat and the room will be kept cooler than the
set-point temperature.
• Lastly, mounting a thermostat near an opening window can also cause random
air temperature variations as outside air blows, or does not blow, over the
thermostat Air Handling Unit Calculation INTRODUCTION
Here ,we have an operation room which should be maintained at a certin temperture and relative humiddity with a totally fresh air for that propose we shall use an air handling unit .

Objective
An air handling unit with full dimension is our out put from the calculation as to determine
•Number of tubes per pass
•Number of rows
•Lenth , width and heigth of the air handling unit .
Coditions of our operation room Out side temperature Inside temperature
Dry bulb temperature (C) 40 21
Relative humidity 50 % 50 % Diameter of the tubes is 5/8 '' (commercially)
Operation on psychometric chart Results
Number of tube per pass 13 tube
Number of tubes per row 26 tube
Total number of tubes 156 tube
Total nuber of rows 6 rows
Height (m) 0.558
Width (m) 0.889
Lenth per pass (m) 1.647025 Fan coil Introduction:
•Definition.
•Types.
•Capacity control.
•Thermostats. Operating Systems:

1.Hot water fan coil

•For heating purpose at entrance.

2.Changeover system

•Same fan coil for heating & cooling.
•While cooling condensation occurs so condensate drain of specific slope is needed, filters are needed to reduce dust buildup.
•Timing is the main challenge.

3.Four-pipe systems

•2 coils one for cooling, the other for heating.
•More expensive but more efficient.
•Ideal for places like hotels, where rooms may be unoccupied for long
periods. The temperature can be allowed to drift well above or below the comfort level, since the fan coil has enough output on full-speed to quickly bring the room to a comfortable temperature. Types and location:

1. Low vertical units

•Are available for use under windows with low sills. However, in some cases, the low silhouette is achieved by compromising features such as filter area, motor serviceability, and cabinet style.

2.Floor to ceiling chase-enclosed units

•These units are used extensively in hotels and other residential buildings. For units serving multiple rooms, the supply and return air paths must be isolated from each other to prevent air and sound interchange between rooms.

3.Vertical and chase-enclosed models at the perimeter

•Give better results in climates or buildings with high heating requirements.

4.Horizontal overhead units

•May be fitted with ductwork on the discharge to supply several outlets.
•Units must have larger fan motors designed to handle the higher static pressure resistance of the connected ductwork.
•They can create problems such as condensate collection and disposal, mixing return air from other rooms, leaky pans damaging ceilings, and difficult access for filter and component removal. Selection:
•Designed based on medium speed for quieter operation, all loads should be considered especially when air is introduced directly through apertures and safety factors should be taken into consideration.

Capacity control:
•Coil water flow.
•Fan speed.

Maintenance:
•Condensate pans and a drain system that must be cleaned and flushed periodically to prevent overflow and microbial build-up.
•Fan-coil unit motors require periodic lubrication. Components:
1. Structure. 6. Standard coil.
2. Fixing brackets (2 or 3 row). 7. Condensate tray.
3. Filter. 8. Fan deck access panel.
4. Fan deck. 9. Electrical connector.
5. Auxiliary coil. 10. Filter access panel.
11. Electrical panel

1.Structure
•Galvanized steel , manufacturing methods are selected to reduce noise , vibration and is composed of:
oCondensate tray.
oFan deck.
oAir filter.
2.Coils
3.Air filter
4.Fan deck
5.Condensate tray
6.Electrical panel

Advantages:
1. System can economically provide many temperature control zones
2. The system conserves space and is useful where ceiling heights are restricted
3. Suitable for low-water-temperature heating, such as with heat recovery.

Disadvantages:
1. Some fans and motors are very inefficient
2. Dehumidification can be a problem where high latent loads are present
3. Fan coils are maintenance intensive and require regular filter replacement and
fan and motor lubrication; condensate drain pans are subject to clogging.
4. Fans can be noisy.
5. Fan coil systems can have high first cost. w 0.254 m
Free flow area/ frontal area 0.534
Fin area / total area 0.893
Hydraulic diameter 0.0003028 m
Afrontal 0.1 m2
L 1 m
H 0.1
Npass 3
N row 3
N total 9
Z 3 CFD Analysis Analysis Components Analysis Results Building Management Systems Definition : A Building Management System is a computerized system which helps the user to facilitate the area around. A BMS is used a monitoring system or a control system. There are two types:
1- Monitoring BMS :
It composed from many sensors and connected to the
equipment (for example humidifiers, temperatures, lights on/off, fan on/off )

2- Control BMS :
it composed as the monitoring system but added with outputs to it. This will have control of these equipment (switches on or off devices) and have scheduled tasks (switch on light on different times of the day). Types of BMS : In a Hotel : a BMS will have the function of monitoring the chillers and control of any valves installed. Apart that a hotel will have various rooms and this can give the BMS software whether the client is in the room or not with some intelligent controller (with the use of sensors).
In a School : the BMS will be need to make control of the PA system, Alarms and scheduled ring bells which will give more facility to the headmaster.
In Home : Some of the functions in the home are; Control of lighting, HVAC and security in one system, Monitoring of energy, water and gas consumption throughout the building. Areas of use : Applications A- Building occupants
1. Good control of internal comfort conditions
2. Possibility of individual room control
3. Increased staff productivity
4. Effective monitoring and targeting of energy consumption
5. Improved plant reliability and life
6. Effective response to HVAC-related complaints
7. Save time and money during the maintenance
  Benefits of a BMS : B- Building owner
1. Higher rental value
2. Flexibility on change of building use
3. Individual tenant billing for services facilities manager
4. Central or remote control and monitoring of building
5. Increased level of comfort and time saving
C- Maintenance Companies
 
1. Ease of information availability problem
2. Computerized maintenance scheduling
3. Effective use of maintenance staff
4. Early detection of problems
5. More satisfied occupants Boiler Calculations Gas Oil Operated Boiler Calculations Natural Gas Operated Boiler Calculations
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