Basics of HVACPrepared by,

Jitendra Jha

What is HVAC….????

• H

• V

• AC

HVAC brief description:• HVAC stands for heating, ventilation, and air conditioning.• HVAC systems control the ambient environment (temperature,

humidity, air flow, and air filtering)• Mechanical intervention to condition air to a preferred temperature

and relative humidity.

By HVAC System:• Temperature can be Raised or Lowered • Humidity can be Raised or Lowered • Filtration can Occur • Proper Air Movement• Outside Air can be Added and Removed • To hold the air contamination within acceptable limits.

Application of HVAC system:• Residential• Commercial• Industrial• Educational• Pharmaceuticals• Hospitals• Malls/Offices• And many more….

Heat Transfer:

Heat

Tra

nsfe

r

Conduction

Convection

Radiation

Refrigeration Cycle:

Major Component of Air conditioning system:• Compressor:This Component is the heart of the system.Pump refrigerant & oil through system.Separates the high pressure side of the system from low pressure side. If its fail, no cooling is takes place.

• Condenser:Condenser coil is what gets rid of the heat in the system.Can be water cooled( located inside, cooled with cooling tower water) or air cooled(located in

outside open to atmosphere) type.Traps dirt & require preventive maintenance & cleaning.

• Evaporator:Provide cooled air to the space.Located after the system air filters.Removes moisture from air(condensate).Traps inside dirt's/dust in filters, so require preventive maintenance.

• Evaporator fan:Located behind condenser coil.Draw ambient air across condenser coil.

• Thermal expansion valve:Located at the evaporator coil.Provide the correct amount of refrigeranet to the evaporator coil for proper cooling..Separates the high pressure side of the system from low pressure side.Failure could cause compressore failure & loss of cooling capacity.

How moisture removed by AC:

• As hot air is blown over the evaporator coils in your air conditioning system, moisture is removed from the air as it condenses. The condensate is the collected in a pan and drained from the system.

• Damp, humid air does maintain heat more than dry air. That is why, during the air conditioning process, your AC removes humidity from the air as it operates. As hot air is blown over the evaporator coils in your air conditioning system, moisture is removed from the air as it condenses

Unit of Refrigeration:

• TR: 1 TR is amount of heat to be extracted from the atmosphere for Melting one metric ton of ice in 24 Hrs.

• 1TR: 12000 btu/hr

• 1TR: 3000kcal/hr=50 kcal/min

System Selection……

Steps for deciding the system:

• Calculation of cooling load requirement• Selection of techno-economical system• Equipment selection.• Designing Air distribution system• Designing Water distribution system• Designing Refrigerant distribution system• Evaluation of system to be used.

Imp. Factors to be considering during Cooling load requirement:• Building detailed layout.• Use of Space• Physical dimension of space• Inside room design condition• Filtration level required• Ambient condition• Glass area exposed to sun• Occupancy• Lighting load• Equipment load• Fresh air requirement• Infiltration of outside air

Factor affecting system selection:

• Budget of Client• Need/Requirement of client• Use of Space• Outside condition• Aesthetic• Floor layout• Location and dimension of beam/Column• Power availability• Space availability• And many more…

Types Of Air Conditioning System:

Various AC system:

• Split AC• Cassette AC• Window AC• Ductable AC• Package AC• VRF System• Chiller System• Dx-System

Split AC

A split air conditioner consists of two main parts: the outdoor unit and the indoor unit. The outdoor unit is installed on or near the wall outside of the room or space that you wish to cool. The unit houses the compressor, condenser coil and the expansion coil or capillary tubing.Available capacity: 1 TR to 3 TR

Cassette ACA ceiling- mounted or suspended air conditioner, for when space is limited, because there is no available walls to mount a split system or where there is limited ceiling space for a ducted system.Available Capacity: 1 TR to 4 TR

Window ACThe term “Window AC" describes a type of AC in which a single unit contains all the components of the air conditioning unit; it is installed in a window of the room.

Available capacity: 1 TR to 2.5 TR

Ductable ACIt is one in which you can run ducting form the inside cooling unit to locations you need a cooling outlet.

Available Capacity: 1 TR to 18.5 TR single unit

Package ACIn the packaged air conditioners all the important components of the air conditioners are enclosed in a single casing like window AC.

Available capacity: 3 TR to 25 TR and more.

VRF System:VRF stand for variable refrigerant flow.In the VRF system, multiple indoor units of multiple room/area/floors are combined in single outdoor unit which shall be placed in open to atmosphere.

Available capacity:6 Hp to 30 Hp (single ODU) and connected upto 100 Hp. (Its changes from company to company)

Maximum distance from IDU to ODU : 200 mtr (approx., its changes from company to company)

Chiller System:Ch

iller Air Cooled

Water Cooled

ScrollCompressor

Centrifugal Compressor

Screw Compressor

Dx- SystemA direct expansion air conditioning (DX) system uses a refrigerant vapour expansion/compression (RVEC) cycle to directly cool the supply air to an occupied space. ... Expansion refers to the treatment of the refrigerant (a valve reduces its pressure and temperature) prior to it entering the evaporator.

Chiller Working Philosophy:

Cooling Tower Working Principle:

What is AHU???

• An air handler is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system.

• Air Handling Unit is a large metal box containing a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators, and dampers.

• Air handlers usually connect to ductwork that distributes the conditioned air through the building, and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served, without ductwork.

AHU Details:

AHU GA:

Air Conditioning system with Water cooled chiller:

Ducting:Ducts are conduits or passages used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air.

Air Distribution Items:

Important Thumb-Rules For AC system:

What is ventilation…???

• Ventilation moves outdoor air into a building or a room, and distributes the air within the building or room. The general purpose of ventilation in buildings is to provide healthy air for breathing by both diluting the pollutants originating in the building and removing the pollutants from it.

Elements of ventilation.....!!!

i)Ventilation rate:The amount of outdoor air that is provided into the space, and

the quality of the outdoor air.ii)Airflow direction:

The overall airflow direction in a building, which should be from clean zones to dirty zones.

iii)Air distribution or airflow pattern:The external air should be delivered to each part of the space in an efficient manner and the airborne pollutants generated in

each part of the space should also be removed in an efficient manner.

Types of Ventilation System:• Forced Ventilation:

A building ventilation system that uses powered fans or blowers to provide fresh air to rooms when the natural forces of air pressure and gravity are not enough to circulate air through a building.

• Natural ventilation:Natural ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural forces.

• Hybrid ventilation:Hybrid (mixed-mode) ventilation relies on natural driving forces to provide the desired (design) flow rate. It uses mechanical ventilation when the natural ventilation flow rate is too low

Various Forced Ventilation System:

• Evaporative Cooling Unit• Fresh Air Fan unit• Exhaust Unit• Exhaust Fans• And many more….

What is Evaporative Cooling Unit…???

• An evaporative cooler is a device that cools air through the evaporation of water.

• Evaporative cooling works by exploiting water's large enthalpy of vaporization.

• The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapour (evaporation). This can cool air using much less energy than refrigeration.

• The cooling potential for evaporative cooling is dependent on the wet bulb depression, the difference between dry-bulb temperature and wet-bulb temperature.

Principle of ECU:

Types of Fans:

Centrifugal Axial

Centrifugal Fan

• Centrifugal fans use the kinetic energy of the impeller to increase the volume of the air stream, which in turn moves them against the resistance caused by ducts, dampers and other components.

• Centrifugal fans displace air radially, changing the direction (typically by 90°) of the airflow. They are sturdy, quiet, reliable, and capable of operating over a wide range of conditions.

• Types of Centrifugal fans:Radial CurvedForward CurvedBackward Curved

Axial Fan:

• The blades of the axial flow fans force air to move parallel to the shaft about which the blades rotate.

• Axial fans are typically used for exhausting dirty air or fumes from processes (such as paint spray booths), supplying fresh air, and general spot cooling of people, rooms or machinery.

• Types of Axial Fans:Tube axialVane axialPropeller fans

Jitendra Jha