Types of ac and humidity control

TYPES OF AIR CONDITIONING SYSTEMS

BASED ON ARRANGEMENT

CENTRAL ZONED UNITARYUNITARY-CENTRAL

PURPOSE

INDUSTRIAL COMFORT/DOMESTIC

CENTRAL SYSTEMCentral AC Systems serve several rooms, the entire system is monitored centrally

using a thermostat

The condenser, compressor, cooling a humidifying coils are located outside the area that has to be air conditioned.

Air is circulated through ducts. Central air conditioning system follow a combination of open and closed cycles of operation. Some of the air is exhausted to the atmosphere while some portion is re-used

PRIMARY AIR FILTER

SECONDARY AIR FILTER (ELECTROSTATIC/FABRIC)

PREHEATER COIL

TEMPERATURE AND HUMIDITY

CONTROL

RECIRCULATED AIR

CONDENSOR COIL

DEHUMIDIFIER

FAN

APPLICATIONS

Big factory spaces

Movie Theatres

Restaurants

Auditoriums

Homes

CENTRAL SYSTEM

ADVANTAGES

The temperature of a very large space can be regulated.

Noise is less as operating equipment is placed outside

Low investment cost when compared to individual units

The exhaust air can be re-used

Though the cost to set-up the unit, the running cost per unit of refrigeration is less

DISADVANTAGES

Very large set-up, occupies plenty of space.

Cost of components like compressors, cooling tubes, ducts are high.

UNIT SYSTEMIn this system, equipment and control mechanisms are packed into a single unit

These are generally used for room air conditioning, as attic fans and remote units

They are generally installed in or near the vicinity of the space that has to be cooled.

ATTIC FAN

UNIT SYSTEMADVANTAGES:

Cost of installation is low

Individual room temperature control is possible

Failure of a unit affects only the area that was served by that unit

It is sufficient to install units in only the rooms where cooling is essential.

HUMIDITY CONTROL

WHAT IS HUMIDITY?Humidity is the amount of water vapour in the atmosphere.

Humidity is measured using a

Psychrometer or Hygrometer

WHY CONTROL HUMIDITY?

Comfort-This is why air conditioners were introduced in the first place.

Storage and Preservation

1. To prevent corrosion

2. Mildew and Mould prevention

3. To prevent condensation

HOW IT HAPPENSThe process of humidity control can be classified as

Mechanical dehumidification

Desiccant dehumidification

MECHANICAL DE-HUMIDIFICATION

MECHANICAL DEHUMIDIFIER

DISADVANTAGES OF MECHANICAL DEHUMIDIFIERS

Very noisy operation

Economical only when used in regions where humidity and temperature are high (above 40% RH)

The compressor unit consumes a large amount of electric power

DESICCANT DEHUMIDIFIER

DESICCANT DEHUMIDIFIER

MATERIALS USED IN DESICCANT DEHUMIDIFIERSZeolites:

-Silica Gel

-Clinitilophite

-Chabazite

APPLICATIONS

PHARMACEUTICAL & BIOMEDICAL INDUSTRY

Any substance has affinity for moisture.

Moisture absorption can affect critical

parameters such as chemical concentration,

thermal expansion

Desiccant dehumidification is generally used.

APPLICATIONSINDUSTRIAL PLANTS, MILITARY AND ELECTRONICS INDUSTRY

One of the primary functions of de-

humidification is to prevent corrosion

Moisture acts as a catalyst

Moisture on PCBs and electronic

components can severely impact their

operation.

APPLICATIONSFOOD AND TEXTILE INDUSTRIES

Moisture and damp conditions are ideal

conditions for the growth of mildew and

mold

Desiccant dehumidifiers are generally

used as the temperature and humidity

in food storage units are generally low.

INDUSTRIAL DEHUMIDIFIER