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service 7 th Semester,BachelorofArchitecture ed S ACHARYA NAGARJUNA UNIVERSITY College of Architecture & Planning

Heating Ventilation & Air Conditioning (HVAC)

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A brief outline of HVAC systems related to Architecture & Building Construction

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Page 1: Heating Ventilation & Air Conditioning (HVAC)

service

7th Semester, Bachelor of Architecture

edS

ACHARYA NAGARJUNA UNIVERSITY

College of Architecture & Planning

Page 2: Heating Ventilation & Air Conditioning (HVAC)

HVAC (heating, ventilation, and air conditioning) is the technology

of indoor and vehicular environmental comfort.

HVAC system design is a sub discipline of mechanical engineering,

based on the principles of Thermodynamics, Fluid Mechanics,

and Heat transfer.

HVAC systems use ventilation air ducts installed throughout a

building to supply conditioned air to a room through outlet vents,

called diffusers; and ducts to remove air through return-air grilles.

HVAC is important in the design of medium to large industrial and

office buildings such as skyscrapers and in marine environments

such as aquariums, where safe and healthy building conditions are

regulated with respect to temperature and humidity, using fresh air

from outdoors.

The three central functions of heating, ventilating, and air-

conditioning are interrelated, especially with the need to

provide thermal comfort and acceptable indoor air quality within

reasonable installation, operation, and maintenance costs.

PROLUSION02

Page 3: Heating Ventilation & Air Conditioning (HVAC)

HVAC systems can provide ventilation, reduce air infiltration, and maintain pressure

relationships between spaces.

The means of air delivery and removal from spaces is known as room air distribution.

The starting point in carrying out an estimate both for cooling and heating depends

on the exterior climate and interior specified conditions.

In modern buildings the design, installation, and control systems of these functions

are integrated into one or more HVAC systems.

For very small buildings, contractors normally capacity engineer and select HVAC

systems and equipment.

For larger buildings, building services designers and engineers, such as

mechanical, architectural, or building services engineers analyze, design, and

specify the HVAC systems.

Basing HVAC on a larger network helps provide an economy of scale that is often

not possible for individual buildings, for utilizing renewable energy sources such as

solar heat.

PROLUSION02

Page 4: Heating Ventilation & Air Conditioning (HVAC)

Thermodynamics is a branch of natural science concerned with heat and its relation

to energy and work. It defines macroscopic variables (such as temperature, internal

energy, entropy, and pressure) that characterize materials and radiation, and

explains how they are related and by what laws they change with time.

Fluid Mechanics : Fluid mechanics is the branch of physics that studies fluids (liquids, gases, and plasmas) and the forces on them. Fluid mechanics

can be divided into fluid statics, the study of fluids at rest; fluid kinematics, the study

of fluids in motion; and fluid dynamics, the study of the effect of forces on fluid

motion.

Heat transfer is a discipline of thermal engineering that concerns the generation,

use, conversion, and exchange of thermal energy and heat between physical

systems. As such, heat transfer is involved in almost every sector of the

economy. Heat transfer is classified into various mechanisms, such as thermal

conduction, thermal convection, thermal radiation, and transfer of energy by phase

changes

INTRODUCTION02

Page 5: Heating Ventilation & Air Conditioning (HVAC)

02 TERMINOLOGY

In heat transfer, conduction is the transfer of heat energy

by microscopic diffusion and collisions of particles or

quasi-particles within a body due to a temperature

gradient.

Convection is the concerted, collective movement of groups or aggregates

of molecules within fluids(e.g., liquids, gases) and rheids,

either through advection or through diffusion or as a

combination of both of them.

Thermal radiation is electromagnetic radiation generated

by the thermal motion of charged particles in matter. All

matter with a temperature greater than absolute

zero emits thermal radiation.

Page 6: Heating Ventilation & Air Conditioning (HVAC)

HEATING

The invention of central heating is often credited

to the ancient Romans, who installed systems of

air ducts called Hypocausts in the walls and floors

of public baths and private villas.

The use of water as the heat transfer medium is

known as Hydronics. These systems also contain

either duct work for forced air systems or piping

to distribute a heated fluid to radiators to transfer

this heat to the air.

The radiators may be mounted on walls or

installed within the floor to give floor heat.

Most modern hot water boiler heating systems

have a circulator, which is a pump, to move hot

water through the distribution system.

. This distribution system can be via radiators,

convectors (baseboard), hot water coils (hydro-

air) or other heat exchangers.

02

Page 7: Heating Ventilation & Air Conditioning (HVAC)

VENTILATION

Ventilation is the process of changing or

replacing air in any space to control

temperature or remove any combination

of moisture, odors, smoke, heat, dust,

airborne bacteria, or carbon dioxide, and

to replenish oxygen.

Ventilation includes both the exchange of

air with the outside as well as circulation of

air within the building

"Mechanical" or "forced" ventilation is

provided by an air handler and used to

control indoor air quality. Excess humidity,

odors, and contaminants can often be

controlled via dilution or replacement with

outside air. However, in humid climates

much energy is required to remove excess

moisture from ventilation air.

02 VENTILATION

Page 8: Heating Ventilation & Air Conditioning (HVAC)

In warm or humid months in many climates

maintaining thermal comfort solely via natural

ventilation may not be possible so conventional air

conditioning systems are used as backups.

An important component of natural ventilation

is air changes per hour: the rate of ventilation

through a room with respect to its volume.

For example, six air changes per hour means that

the entire volume of the space is theoretically

replaced with new air every ten minutes.

For human comfort, a minimum of four air

changes per hour is usually targeted.

The highest recommended replacement rates are

for crowded spaces like bars, night clubs, and

commercial kitchens at around 30 to 50 air

changes per hour

VENTILATION02 VENTILATION

Page 9: Heating Ventilation & Air Conditioning (HVAC)

AIR CONDITIONING02

Air conditioning and refrigeration are provided through the removal of

heat.

Heat can be removed through Radiation, Convection, or Conduction.

A refrigerant is employed either in a heat pump system in which

a compressor is used to drive Thermodynamic refrigeration cycle, or ina free cooling system which uses pumps to circulate a cool refrigerant

(typically water or a glycol mix).

Free cooling systems can have very high efficiencies, and are

sometimes combined with seasonal thermal energy storage so the cold

of winter can be used for summer air conditioning.

Common storage mediums are deep aquifers or a natural

underground rock mass accessed via a cluster of small-diameter, heat

exchanger equipped boreholes.

Some systems with small storages are hybrids, using free cooling early in

the cooling season, and later employing a heat pump to chill the

circulation coming from the storage.

Page 10: Heating Ventilation & Air Conditioning (HVAC)

During the hot days of

summer, the air

conditioning kicks in,

providing much-needed

cool air.

In the frigid days of winter,

the system supplies heat.

An HVAC system is responsible for moderating the temperature of a building’s

interior and maintaining it at a comfortable level for the inhabitants. 02

Page 11: Heating Ventilation & Air Conditioning (HVAC)

CO

MPO

NEN

TS

02

Page 12: Heating Ventilation & Air Conditioning (HVAC)

THE FURNACE

The furnace unit is typically fairly

large, requiring its own space within

a building.

It is often installed in the basement,

in the attic, or in a closet.

The furnace pushes the cold or hot

air outward into the ducts that run

through every room in the building.

Throughout the ducts, there are

vents that allow the warm or cool air

to pass into rooms and change their

interior temperature.

02

Page 13: Heating Ventilation & Air Conditioning (HVAC)

THE HEAT EXCHANGER

Heat exchangers reside in the housing of

every furnace unit. When the furnace is

activated by the thermostat, the heat

exchanger begins to function as well.

Air is sucked into the heat exchanger, either

from the outside or from a separate duct

that pulls cool air out of the building’s rooms.

This type of duct is called a cold air return

chase.

When the cool air comes into the heat

exchanger, it is quickly heated and blown

out through the ducts to be dispersed into

the building.

If the furnace operates on gas, the heating is

accomplished by gas burners.

If it uses electricity, it is done via electric coils.

02

Page 14: Heating Ventilation & Air Conditioning (HVAC)

02

Page 15: Heating Ventilation & Air Conditioning (HVAC)

THE EVAPORATOR COIL

Like heat exchangers, evaporator coils are also

part of the furnace unit. However, they serve the

opposite function to that of heat exchangers.

They are also attached to a different part of the

furnace.

Instead of being within the furnace housing, they

are installed inside a metal enclosure that is

affixed to the side or the top of the furnace.

Evaporator coils are activated when cool air is

needed. When triggered, the evaporator coil

supplies chilled air, which is then picked up by the

furnace blower and forced along the ducts and

out through the vents.

The internal design of an evaporator coil

resembles that of a car’s radiator.

Evaporator coils are connected to the HVAC

system’s condensing unit, which is typically

located on the exterior of the building.

02

Page 16: Heating Ventilation & Air Conditioning (HVAC)

THE CONDENSING UNIT

The condensing unit is installed outside the

building, separate from the furnace.

Inside the condensing unit, a special kind

of refrigerant gas is cooled through the exchange

of heat with the air outside.

Then, it is compressed and condensed into liquid

form and sent through a tube or a line made of

metal.

This tube runs straight to the evaporator coil. When

the liquid reaches the coil, a series of small nozzles

spray the liquid, lowering its pressure and allowing

it to resolve back into gaseous form.

During the evaporation of liquid to gas, heat is

absorbed, causing a sudden drop in temperature

and supplying cold air for the furnace blowers.

The refrigerant gas is then sent back outside to the

condensing unit, and the process is repeated

again to generate additional cold air.

02

Page 17: Heating Ventilation & Air Conditioning (HVAC)

THE REFRIGERANT LINES

The refrigerant lines are the metal tubes that carry the liquid to the evaporating

coil and return the gas to the condensing unit.

Refrigerant lines are usually made from aluminium or copper.

They are designed to be durable and functional under extreme temperatures.

02

Page 18: Heating Ventilation & Air Conditioning (HVAC)

THE THERMOSTAT

The thermostat controls the function of the furnace.

It is directly connected to the furnace and includes

temperature-sensing technology as well as user

controls.

A thermostat is usually positioned somewhere within the

building where it can easily discern temperature and

remain accessible to users.

A large building may have more than one thermostat

to control different areas of the structure.

The inhabitants of the building can manually set the

thermostat to a certain temperature.

If the air in the room or building is too cold, the heat

exchanger kicks in and blows heat through the vents.

If the room is too warm, the condensing unit and

evaporator coil start to function, and the air

conditioning system sends cool air throughout the

building or to one particular section of the building.

02

Page 19: Heating Ventilation & Air Conditioning (HVAC)

THE DUCTS

Heating ducts are put in during the construction of a home

or a building.

They are often run through the ceiling.

In each room, at least one rectangular opening is cut into

the duct so that a vent or vents can be installed.

02

Page 20: Heating Ventilation & Air Conditioning (HVAC)

THE VENTS

Vents are usually rectangular in shape. They

are placed in the ceiling, with their edges

corresponding to the opening in the duct

above.

As warm or cool air pours through the ducts,

vents allow it to disperse into the rooms below.

Vents are usually made of metal, which can

handle a wide range of temperatures.

The vent is comprised of a rectangular edge or

frame, within which is a series of thin metal

slats.

The slats are angled to channel the air

downward.

Some vents also include a manual control that

lets users angle the air toward a different part

of the room depending on their preference.

02

Page 21: Heating Ventilation & Air Conditioning (HVAC)

Efficiency

RatingMeaning

80% efficiency Ducts collect and reuse 80 percent of the

generated heating or cooling energy

92% efficiency

or higher

Ducts collect and redistribute 90 percent of the

energy created by the furnace unit

TYPES OF FURNACES

Furnaces can be divided into two main categories:

Single stage furnaces

Two-stage furnaces.

Both types of furnaces are further distinguished by their performance ratings.

The chart below explains the function of performance ratings.

In furnaces with 80% or +92%efficiency, any energy that is not captured by

the ducts is lost, usually through the furnace housing or through vents

leading to the outside of the building.

02

Page 22: Heating Ventilation & Air Conditioning (HVAC)

DEFINITIONS

The Coefficient of performance or COP of a heat pump is a ratio of heating or cooling provided to electrical energy consumed.

COP = 𝑄

𝑊

Q is the heat supplied to or removed from the pump

W is the work consumed by the heat pump

Energy Efficiency Ratio : The EER is the ratio of output cooling energy (in BTU) to electrical input

energy (in Watt-hour)

EER = 𝑜𝑢𝑡𝑝𝑢𝑡 𝑐𝑜𝑜𝑙𝑖𝑛𝑔 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝐵𝑇𝑈

𝑖𝑛𝑝𝑢𝑡 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝑊

Seasonal Energy Efficiency Ratio : It is the ratio of output cooling energy (in BTU) to electrical input

energy (in Watt-hour).

SEER is a representative measurement of how the system behaves over a season where the

outdoor temperature varies

SEER = 𝑂𝑈𝑇𝑃𝑈𝑇 𝐶𝑂𝑂𝐿𝐼𝑁𝐺 𝐸𝑁𝐸𝑅𝐺𝑌 𝑂𝐹 𝐴 𝐵𝑇𝑈 𝐼𝑁 𝐴 𝑆𝐸𝐴𝑆𝑂𝑁

𝐼𝑁𝑃𝑈𝑇 𝐸𝐿𝐸𝐶𝑇𝑅𝐼𝐶𝐴𝐿 𝐸𝑁𝐸𝑅𝐺𝑌 𝐼𝑁 𝑊ℎ

02

Page 23: Heating Ventilation & Air Conditioning (HVAC)

DEFINITIONS

Kilo-Watt per Ton (kW/ton)

The efficiencies of large industrial air conditioner systems, especially chillers, are given in kW/ton to specify the amount of electrical power that is required for a certain power of cooling. In this case, a smaller value represents a more efficient system.

Horse Power

Another unit in use in the US is the horse power (HP). This is a unit of power and typically is used to specify the size of motors. It may also be used to specify the input power of an air conditioning system. One HP is approximately 746 W.

Energy Star :

In the US, Energy Star is the Environmental Protection Agency’s (EPA’s) indication for products that have high energy efficiency. it makes it easy for consumers to identify and purchase products that have higher energy efficiency than those products without such designation.

02

Page 24: Heating Ventilation & Air Conditioning (HVAC)

BIBLIOGRAPHY

http://en.wikipedia.org/wiki/HVAC

http://www.powerknot.com/how-efficient-is-your-air-conditioning-system.html

http://newikis.com/km/%E1%9E%AF%E1%9E%80%E1%9E%9F%E1%9E%B6%E1%9E%9A:Air_conditioning_unit.svg.html

http:// www.google.com/images (Image courtesy)

http:// www.edcmag.com/articles/hvac-systems-how-they-work

Page 25: Heating Ventilation & Air Conditioning (HVAC)

Thank you..!!

Joel.T.J.,Y10AP0116

B.Arch. (IV/V)

Pratheek.P.A.,Y10AP0103

B.Arch. (IV/V)