Module 1 HVAC

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Module 01

HVAC SystemInstructor:

Engr. Haris Alam

Department of Civil Engineering

CECOS University, Peshawar.


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What is HVAC System??

CECOS University, Peshawar. 2

H V A C S y s t e m H- Heating

V- Ventilation

AC – Air Conditioni


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Few people think that HVAC is allLuxury, Waste of money &

Valuable Energy.

But…….!!!

HVAC System

3CECOS University, Peshawar.


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Of Course,

It is Right of Every Individualto live in Comfort & HVAC

Serves the industrial segment

to great extent.

HVAC System



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• Control of Air Temperature.

• Control of Moisture Content in Air.

• Proper Air Movement.

• To Hold the Air Contamination Within Acceptable limits

Functions of HVAC



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6CED, CECOS University, Peshawar.

Humidity & Temperature:

• Humidity:

• Humidity is the amount of water vapor in the air. Water vapor is th

gaseous state of water and is invisible.

• There are three main measurements of humidity:

• Absolute humidity is the water content of air.

• Relative humidity , expressed as a percent, measures the current absolut

humidity relative to the maximum for that temperature.

• Specific humidity is a ratio of the water vapor content of the mixture to th

total air content on a mass basis.


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• Electrical Hygrometers• Hygroscopic films detect atmospheric moisture

• Dew point impedance from partial pressure of water vapor

• Chilled mirror

• Optically sense presence of dew or frost on mirror

• Measure temperature of mirror for dew point or frost point

• Recent optical sensing improvements

Humidity Instruments:

CED, CECOS University, Peshawar.e 7


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Problems due to Humidity:

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• Electrical: . High voltage short-circuit occurs when the insulation is moist.

• Archive: Films and papers will stick together if stored in moist place. Paper turn

yellow and disintegrates.

• Metal: A lot of metals are free from corrosion if the environment is dry.

• Food: Drying is usually part of food processing. Food exposed to moisture are

subject to fungal growth.

• Military: A lot of military gears must be stored at low RH to keep away from rus

forming. Gun powder and explosive are particularly sensitive to moisture.

• Batteries production: Extremely low RH is required to batteries production.

• Photography material: Most films are moisture sensitive.


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Humidity Levels:


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Humidity & Temperature:

• Temperature:

• A temperature is a comparative measure of hot and cold.

• It is measured, typically by a thermometer, through the bulk behavior o

a thermometric material, detection of heat radiation, or by particl

velocity or kinetic energy.


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Electrical Thermometers

•

Thermocouple: A Thermocouple is a sensor used to metemperature. Thermocouples consist of two wire legs made from different metalswires legs are welded together at one end, creating a junction. This junction is whetemperature is measured.

• Resistance temperature detector (RTD):RTD are devices used to metemperature by correlating the resistance of the RTD element with temperature. Moselements consist of a length of fine coiled wire wrapped around a ceramic or glass cor

element is usually quite fragile, so it is often placed inside a sheathed probe to protect• Thermistor :A thermistor is a type of resistor whoseresistance varies significantly with temperature, more so

than in standard resistors.

Temperature Instruments

CED, CECOS University, Peshawar. 11


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Manual Thermometers:

• Liquid in glass thermometers

• Bi-metallic sensor

Temperature Instruments



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Comfort Levels:



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• The Cooling load calculation begins with the determination of he

loss through a variety of building envelope components an

situations.

• Walls , Roofs , Windows, Doors, Exposed Floors, Slab-on-Grade , Baseme

Walls, Infiltration Ventilation ,Duct Loss , Electric Appliances, Humans & other

Cooling Load Calculation:



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Cooling Load Calculation:



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16CED, CECOS University, Peshawar.

Temperature & Humidity Controls:


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Components….

CED, CECOS University, Peshawar.


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• Source Components

• Distribution Components

• Delivery Components

Components of HVAC System:



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• Source Components:

Heating :• Combustion of some flammable material (a fuel)

• Conversion of Electrical energy to heat

• Solar radiation or other renewable energy resources

• Removal of Heat from material on site and transferred into a building

Cooling:• Natural Heat Sinks (Outside air, the night sky, on-site water bodies,

and on-site soil)

• Artificial Heat Sinks (Vapor compression (mechanical) refrigeration, ,absorption (chemical) refrigeration, evaporative cooling)




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• Natural Heat Sink




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• Artificial Heat Sink:




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• Commonly used Heating & Cooling system for active control

• Fireplace:• Wood Strove:

• Furnace:

• Boilers

• Solar Thermal Collector

• Vapor Compression Refrigeration Unit• Absorption Refrigeration Unit.

• Chillers

• Cooling towers




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• Distribution Component:

•

Heating or cooling effect produced must be transmitted to thevarious spaces in a building

• Three transmission media are commonly used in central systems:

air, water, and steam.

• Air & Steam Based System

Two Ducts are required one for Conveying the air & Other for taking theair back to the system

• Water Based System:

Minimum of 3 pipe system is required.

• High Pressure & Low Pressure System




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• Distribution Component:

• Dampers are used to control air flow ,they balance

flows throughout a system

• Specialized fire dampers and smoke dampers are

used to reduce the spread of fire and smoke through

the building air distribution system.

• Splitters and turning vanes are used to reduce

friction losses by reducing turbulence within the

ductwork; they also can reduce noise generated

within the ducts.




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• Delivery Component:

• Devices designed to provide the interface between

occupied building spaces and distribution

components are collectively termed delivery

devices.

Diffusers.

Registers.

Grille.




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Assignment #01

Climatic Control System



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Ventilation….



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•

Process of "processing" or replacing air in any space to providhigh indoor air quality.

• Used to remove unpleasant smells and excessive moisture, introduc

outside air, to keep interior building air circulating, and to preven

stagnation of the interior air.

• Ventilation includes both the exchange of air to the outside as well a

circulation of air within the building.

Ventilation System:



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• Maintain human comfort and health.

• Provide sufficient oxygen (approx. 21%) for human during overcrowding inoffice (Remove Heat generated).

• Remove products of respiration and bodily odor.

• Remove contaminants or harmful chemicals.

• Create air movement (feeling of freshness/comfort)

• Moisture problems, as indicated by visible fungal growth in corners.

• Staining and discoloration of false ceilings, walls or carpets.

• Smoking in the office..

Purpose of Ventilation:



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• Basic elements of Ventilation system:

• Ventilation Rate: The amount of outdoor air

that is provided into the space.

• Airflow direction: From clean zones to dirty zones

• Air distribution or Airflow pattern: Deliverance of air to each part of

the space in an efficient manner ----- Airborne pollutants removed in

an efficient manner.

Ventilation System:



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Natural Ventilation:

•

Natural movement of air enteringand leaving openings such aswindows, doors, wind towers, roofventilators.

• Heated air rises, cool air below.( wind

towers/ high ventilators)

• Mainly rely on pressure difference----placement of Openings to circulatewind.

Types of Ventilation:



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Mechanical Ventilation:

• Alternative to Unreliable Natural Source. Also known as Forc

• Usually accepted as being the use of ducted air distributed to

centrally located fans with the addition of air filtration, heatin

cooling, humidification or heat recovery.

• Case of Hospital ----- Need Sterilized places ----- Can’t provid

opening like windows.

• Components involves: Exhaust Fans , Filters, Ductworks & Diffu




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Propeller inside to enhance up-flowair movement

Some without propeller and some install it in wrong orientation


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Hybrid Ventilation:

•

Introduction of outdoor air ventilation into a building bmechanical and Natural.

• It is sometimes called mixed-mode ventilation.

• The Changeover Type

• The Concurrent (or zoned) Type:

• Changeover variant, controls could switch between mechanipassive ventilation seasonally, diurnally, or based on a meparameter.

• Concurrent variant, appropriate controls are needed to p“fighting” between the two ventilation methods.




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Module 1 HVAC

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