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Refrigeration and air conditioning are used for the purpose of cooling products or cooling the environment of a building. The transfer of heat is done form a cooler reservoir of low energy to a warmer high energy reservoir y the refrigeration or air conditioning system (R. A refrigeration system contains several heat transfer loops. Thermal energy is extracted form the loop and then is expelled to the outdoors by using five loops of heat transfer and moves from left to right in the process.

1. Indoor air loop. Indoor air is driven by the supply air fan by using a cooling coil, and the heat contained in it is transferred to the chilled water, in the left part of the loop. The building space is then cooled by the building air.

3 Chilled water loop water which is driven by the chilled water pump, returns from the cooling coil to the chiller’s evaporator for the process of re-cooled.

4 Refrigerant loops. By the use of a phase-change refrigerant, the chiller’s compressor is used to pump heat which is contained in the chilled water into the condenser water.

5 Condenser water loop the heat from the chiller’s condenser is absorbed by water, which is then sent by the condenser water pump to the cooling tower.

6 Cooling tower loop here the heat is transferred to the outdoors by the fans of the cooling tower which drive the air across an open flow of the hot condenser water.

Air-Conditioning Systems

There are several combinations and options for the process of air conditioning, which can be selected on the basis of application they are to be used in.

Split air conditioning

Air conditioning (for machines and space)

large systems air handling units

Fan coil units in a larger system

Refrigeration Systems (for processes)

Some air conditioning refrigeration systems which are widely used for industrial processes for example chilling plants) and for domestic cooling purposes for example in modular units or refrigerators are:

1. The direct expansion type small capacity modular units which are similar to domestic refrigerators.

2. The Centralized chilled water plants using chilled water as a secondary coolant. The temperature ranges typically over 5 oC. They are also used for the purposes of ice bank formation.

TYPES OF REFRIGERATION AND AIR CONDITIONING

The two most widely used refrigeration and air conditioning systems

The Vapor Absorption Refrigeration (VAR) and the Vapor Compression Refrigeration (VCR) and

In the vapor compression refrigeration method, VCR, the driving force for refrigeration is the mechanical energy whereas in the vapor absorption refrigeration, VAR uses thermal energy acts as the driving force for the process of refrigeration.

Vapor Compression Refrigeration System

The Compression refrigeration cycles take advantage of the acknowledge fact that highly compressed fluids, which are at a certain temperature, often tend to get colder when allowed to expand. If the pressure change provided is high enough to the system, then the compressed gas will be even hotter than the source of cooling

(Which can be outdoor air) and the gas which is expanded will be cooler than the cold temperature which is desired. Therefore, for these cases, fluid is used for cooling an environment which is at low temperature while rejecting the heat to an environment at high temperature. The Vapor compression refrigeration cycles have two major advantages over other processes. The primary advantage is that since a large amount of thermal energy is required for changing the liquid contained to its vapor state, a lot of heat can be actually removed from the air-conditioned space by the process. Secondly, since the vaporization is of isothermal nature, the extraction of heat is allowed and there is no need to raise the temperature of the working fluid to the temperature of whatever is being cooled y the refrigeration and air conditioning processes. Therefore the closer the working fluid temperature approaches to the temperature of the surroundings, the lower is the rate of heat transfer. Hence the hat transfer rate is always high.

Vapor Absorption Refrigeration System

The components of the vapor absorption refrigeration system are:

The Absorber: the Absorption of refrigerant vapor is done by using a suitable absorbent or adsorbent.

The Pump: the rich solution is pumped and raised its pressure is then raised to the pressure of the condenser.

The Generator: it is used for the distillation of the vapor from the rich solution and the poor solution is left for recycling

The absorption chiller is a machine which is used for producing chilled water by using heat from the sources like gas, oil, hot water, steam. The production of chilled water is based on the principle that the liquid or the refrigerant, evaporating at a low temperature, absorbs heat from its surroundings while evaporating. Pure water is often used as refrigerant whereas the absorbent is lithium bromide solution in any cases. Heat for the vapor absorption refrigeration system is provided by the waste heat which extracted from the process itself, by diesel generator sets etc. In such cases, electricity is required by absorption systems for running pumps only. Many a times it is economical to generate heat / steam for operating the absorption system and the production depends on factors like power cost and temperature required.

System Design Features

The adoption of good practices improves the energy efficiency levels significantly and are considered and adopted in the overall plant design. Some areas which are emphasized upon are:

1. Optimizing of the lighting loads indeed the air conditioning areas. Number of air changes is also optimized.

2. Design of cooling towers is done by using PVC drift eliminators FRP impellers and film fills etc. Softened water is used for condensers in place of raw water.

3. Economic insulation thickness is used in heat exchangers, cold lines thereby considering and reducing the cost of heat gains. Other practices adopted are infrared thermograph for monitoring which is applicable especially in the fertilizer, large chemical and the process industry.

4. Roof coatings for cooling systems and false ceilings applicable are adopted for minimizing the refrigeration load.

5 Adoption of energy efficient heat recovery devices are used for precooking the fresh air by the process of indirect heat exchange to precool the fresh air by indirect heat exchange for example air to hear exchangers.

6 The relative humidity is controlled through indirect heat exchangers rather than use of duct heaters after chilling.

7 Variable air volume systems are adopted along with adopting of sun film application for heat reflection