HVAC For Beginners

HVAC-For Beginners

Heat, Ventilation and Air Conditioning

Contents

I.  VCRS - Basic Refrigeration Cycle

II. Basic Components of AC

III. Classification of AC System

I. VCRS - Basic Refrigeration Cycle

VCRS stands for Vapour Compression Refrigeration Cycle. This is the basic cycle on which our    refrigerator or air-conditioner works. It consists of evaporator, compressor, condenser and expansion  valve. 

Evaporator is the coil which absorbs the heat from the space which needs to be cooled. 

Compressor compresses the vapour refrigerant and create high pressure for the movement of refrigerant throughout the cycle. 

Condenser is the coil which rejects the absorbed heat to the atmosphere withe the help of fins and fan cobination. 

Expanison valve regulates the amount of refrigerant need to pass through the evaporator coil as per the cooling load requirement.

High pressure side and low pressure side:
High Side - After compressor and before expansion valve.
Low Side - Before compressor and after expansion valve.

II. Basic components of air-conditioner

Evaporator Coil - Receives the low temp. liquid refrigerant and absorb the heat from room and vaporizes.

Evaporator Fan – Sucks the room air via evaporator coil where it absorb coolness from the coil and throws sucked air after cooling back into the room.Condenser Coil - Rejects heat from the high temp. refrigerant to the atmosphere.Condenser Fan – Blows atmospheric air on the condenser tubes so that it can make the heat transfer faster and efficient.

Expansion/Throttle valve - regulates refrigerant flow into the evaporator as per the cooling load.

Compressor - A pump that compresses the refrigerant after it leaves the evaporator.

Oil Separator – It separates the lubricating oil of compressor from refrigerant, which is mixed with the refrigerant while compression inside the compressor.

III. Classification of air-conditioner

1. Window AC (0.5 TR to 2 TR)

2. Split AC

  i. Wall mounted AC (1 TR to 5 TR)

  ii. Ceiling Mounted AC ( 1 TR to 5 TR)

  iii. Floor stand AC ( 1 TR to 5 TR)

  iv. Cassette type AC (1 TR to 5 TR)

  v. Duct able Split AC ( 1 TR to 7 TR)

3. Package AC  ( 1 TR to 25 TR)

4. VRV system (Variable Refrigerant Volume) (6.5 TR to 24 TR)

5. Chilled Water System ( 20 TR to 1500 TR)

1. Window AC (0.5 TR to 2 TR)

This type of AC is used for small spaces like our single room in our house. It sucks the indoor air using the evaporator fan and throws the air on the evaporator coil where it absorbs coolness from the cold liquid refrigerant flowing inside the evaporator coil. After passing through the coils cool air goes to the room to cool and at the same time liquid refrigerant vaporizes and move to the compressor where it get compressed and pass to the condenser coils. While passing through condenser coil it rejects its heat to the to the atmospheric/outdoor air and gets condensed to liquid form and pass to the expansion valve and then to evaporator to complete the further cycle.

2. Split AC

i. Wall mounted AC (1 TR to 5 TR)

This type is called split because the one single window AC is split into two parts indoor and outdoor unit. Indoor unit consists of expansion valve, evaporator coil, fan and air filter. Outdoor unit consists of compressor, condenser coil and fan.

ii. Ceiling mounted AC (1 TR to 5 TR)

This type is another variation of split AC. As per the space available we are selecting split AC. Indoor unit consists of expansion valve, evaporator coil, fan and air filter. Outdoor unit consists of compressor, condenser coil and fan.

iii. Floor stand AC (1 TR to 5 TR)

The places where there is constraint that we cannot mount the indoor unit on the wall at that place we are using floor mounted AC. Indoor unit consists of expansion valve, evaporator coil, fan and air filter. Outdoor unit consists of compressor, condenser coil and fan.

iv. Cassette Type AC (1 TR to 5 TR)

The places where there is constraint that we cannot mount the indoor unit on the side wall and the airflow needs to be equally divide towards all four directions at that place we are using cassette type AC. Indoor unit consists of expansion valve, evaporator coil, fan and air filter. Outdoor unit consists of compressor, condenser coil and fan.

v. Ductable split AC (1 TR to 5 TR)

The places where we have to cool more than one room with a single AC at that time we are using ductable split type AC. The cool air from indoor unit is distributed to different rooms through duct. Indoor unit consists of expansion valve, evaporator coil, fan and air filter. Outdoor unit consists of compressor, condenser coil and fan.

3. Package AC (1 TR to 25 TR)

Package AC does not have indoor and outdoor unit. It contains all the components in one unit which can be mounted on the roof  and the cold air coming from the unit is taken to different rooms through duct. The places where the cooling area is big having more cooling load and also there are many rooms to cool at that place we are using package AC. 

4. VRV/VRF system (6.5 TR to 24 TR)

VRV/VRF stands variable refrigerant volume/flow. This type of AC system is having many indoor units and there is common outdoor for all the indoor units thats why it is called variable refrigerant flow/volume system because the different indoor units can be of different capacity and needs variable amount of refrigerant to pass through it as per their tonnage or capacity.

5. Chilled Water System (20 TR to 1500 TR)

I. Water Cooled Chiller  – Refrigerant in condenser is cooled by cold water in a shell and tube type heat exchanger(condenser). The cold water from cooling tower enters the heat exchanger(condenser) and absorb the heat from the refrigerant.

II. Air Cooled Chiller – Refrigerant in condenser is cooled by atmospheric air.