Refrigeration and Air conditioning PPT

1. INTRODUCTION

This section briefly describes the main features of the refrigeration and air conditioning

system.

1.1 What is Refrigeration and Air Conditioning

Refrigeration and air conditioning is used to cool products or a building environment. The

refrigeration or air conditioning system (R) transfers heat from a cooler low-energy reservoir

to a warmer high-energy reservoir

There are several heat transfer loops in a refrigeration system as shown in Figure 2. Thermal

energy moves from left to right as it is extracted from the space and expelled into the

outdoors through five loops of heat transfer:

§ Indoor air loop. In the left loop, indoor air is driven by the supply air fan through a

cooling coil, where it transfers its heat to chilled water. The cool air then cools the

building space.

§ Chilled water loop. Driven by the chilled water pump, water returns from the cooling coil

to the chiller’s evaporator to be re-cooled.

§ Refrigerant loop. Using a phase-change refrigerant, the chiller’s compressor pumps heat

from the chilled water to the condenser water.

§ Condenser water loop. Water absorbs heat from the chiller’s condenser, and the

condenser water pump sends it to the cooling tower.

§ Cooling tower loop. The cooling tower’s fan drives air across an open flow of the hot

condenser water, transferring the heat to the outdoors.

1.2 Air-Conditioning Systems

Depending on applications, there are several options / combinations of air conditioning,

which are available for use:

§ Air conditioning (for space or machines)

§ Split air conditioners

§ Fan coil units in a larger system

§ Air handling units in a larger system

1.3 Refrigeration Systems (for processes)

The following refrigeration systems exists for industrial processes (e.g. chilling plants) and

domestic purposes (modular units, i.e. refrigerators):

§ Small capacity modular units of the direct expansion type similar to domestic

refrigerators.

§ Centralized chilled water plants with chilled water as a secondary coolant for a

temperature range over typically 5 oC. They can also be used for ice bank formation.

§ Brine plants, which use brines as a lower temperature, secondary coolant for typically

sub- zero temperature applications, which come as modular unit capacities as well as large

centralized plant capacities.

§ The plant capacities up to 50 TR (tons of refrigeration) are usually considered as small

capacity, 50 – 250 TR as medium capacity and over 250 TR as large capacity units.

A large company may have a bank of units, often with common chilled water pumps,

condenser water pumps, cooling towers, as an off site utility. The same company may also

have two or three levels of refrigeration and air conditioning such as a combination of:

§ Comfort air conditioning (20 – 25 oC)

§ Chilled water system (80 – 100 C)

§ Brine system (sub-zero applications)

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