Cooling System – Chiller TechnologiesBy Husain Baqer – Engineering (Tahleeq)

Outside Design Conditions

Dry Bulb 46

Wet Bulb 30.9

Based on the heat load, the chilled water temperatures shall be as follows:

Chilled Water Temperatures

Leaving Temperature 5.5

Return Temperature 14.5

Design Criteria

The selected Chiller System shall satisfy the Design Criteria.

Husain Baqer – Engineering

What do we want from an air-conditioning system?

Production of chiller water

Durability

Reliability

Efficiency

Controllability

Power

Maintenance

Network

Allocation of Space

Initial cost

Equipment (Accessories)

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What do we want from a Chiller System?

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Main Types of Chiller Systems1) Air-Cooled Chiller

Condenser

Fan

Evaporator

Compressor

Expansion Valve

What do we want from a Chiller System?

Husain Baqer – Engineering

Main Types of Chiller Systems1) Air-Cooled Chiller

Air cooled chillers

Primary pumpCHWR CHWS

Main Types of Chiller Systems

2) Water-Cooled Chiller

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Main Types of Chiller Systems

3) Absorption Chiller

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1) Air-Cooled VS Water-Cooled Chillers (Pros and Cons)

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Air-Cooled Water-Cooled• Lower installation cost• Less maintenance (depending on

application)• Cooling tower not needed• Condenser pump not required• Require less space

• Usually have a longer life• Higher efficiency• Indoor placement • Larger tonnage capabilities • Refrigeration containment• LEED points

• Generally less efficient• Life span is not as long• Noisy• No LEED points

• Additional maintenance costs• Water treatment cost• Mechanical room needed• Large consumption of water• Require larger space• 3 storey CUC in lieu of 2

Central Utility Complex-Chillers Layout (Original Design)

Air-Cooled Chillers(on the roof)

24 Air-cooled chillers capacity 435 TR.

Husain Baqer – Engineering

Husain Baqer – Engineering

1A) Closed Loop Dry Cooling System (Similar to BIA current cooling system):

Water-Cooled Chiller Types

• Is similar to the radiator in your car.• The system uses an air-cooled fluid cooler to transfer

the heat from the closed-loop coolant fluid pumped through rows of finned tubes that have ambient air blown/drawn across them

Description

Basic Components

• Fluid Cooler (Contains air-to-liquid heat exchanger with the fan(s).

• Pump• Control Skid• Coolant• Piping

Strengths

Very simple and relatively easy to install.

Energy requirement are relatively low and it’s easily controlled.

Maintenance is normally low requiring and periodic inspection, lubrication, and testing of the fluid.

Weaknesses

Dependent on the atmospheric dry bulb temperature.

1A) Closed Loop Dry Cooling System

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The fluid cooler must be placed in a location that is not affected by the prevailing winds, not too close to a building that will allow the warm exhaust air from the fluid cooler to be recirculated back to the fluid cooler, and finally not in a location that has heavy concentration of dust, dirt, leaves or seeds.

Husain Baqer – Engineering

1A) Closed Loop Dry Cooling System

Requirements:

• The system requires free clear air to work efficiently. Why?

same as the closed-loop dry system but adds a supplemental fluid cooler.

This system is typically used in a location that has too high temperature of a dry bulb in the summer to provide the proper coolant temperature to the load.

With an added liquid-to-liquid trim cooler the customer can use a water source to trim the temperature to the desired set point.

Many times closed-loop dry system with a trim cooler are used to reduce the reliance on city water as a coolant.

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1B) Closed-loop Dry System with Trim Cooling

Description:

• Uses the design Wet Bulb (i.e. 30.9) as the basis of the outlet temperature of the cooling water.

• During the evaporation, the remaining water is cooled to as close as 7F or higher above the wet bulb temperature

• The evaporated water is replaced with some type of make-up water system like a float valve

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2A) Open-loop Evaporative Cooling System

Description

Components• Chiller (Evaporator & Condenser)• Condenser Pump• Cooling Tower• Piping

Strengths

Equipment is typically inexpensive

Simple to employ in warmer climates

Maintenance is normally low requiring and periodic inspection, lubrication, and testing of the fluid.

2A) Open-loop Evaporative Cooling System

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RequirementsA drain will be required for blow-down of the water to

keep the conductivity in check from the constant evaporating and concentrating of the dissolved solids.

Make-up water is continually required from external source such as city water or treated well water, etc. Biological control of bacteria, slime, and mold are major concerns for proper operation of an open evaporative tower system.

2A) Open-loop Evaporative Cooling System

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2A) Open-loop Evaporative Cooling System (Highlights)

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• Typical open loop cooling towers have been called “air scrubbers,” because airborne dust and other contaminants inevitably end up in the process water loop.

• In addition, they also suffer from algae, bacterial/legionella, and microbiological build-up, as well as scale accumulation

• This results in the need for constant testing of the water and injection of replacement chemicals.

To achieve one ton of cooling, a tower must evaporate around 0.03 gallon (3.8 Liter) of process water each minute.

The following example of evaporative loss is based on 8,760 operating hours per year (24 hours per day, 365 days per year) with tower operating at full capacity:

2A) Open-loop Evaporative Cooling System

100 Ton Tower 3 GPM 1,576,800 GPY (5,968,837 LPY)

Highlights

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Is a hybrid system with an open tower and a closed-loop heat exchanger built into the tower. The tower water stays outside in the tower and does not circulate through the coolant

piping. The coolant piping is a closed loop, with a glycol/water solution flowing from the tower to

the load and back

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2B) Closed-loop Evaporative Cooling System

Description:

Refrigerant vapor in

Refrigerant liquid out

Strengths

it can deliver closed loop coolant to the load at approximately 7 to 10 F above the wet bulb temperature

The closed-loop coolant remains free of contaminates and allows the equipment heat exchanger and piping to remain clean

Any contaminates from the atmosphere will stay outside with the tower

Fewer water treatment chemicals will be used because they are only treating the open water in the tower and not the coolant in the piping and system heat exchangers

2B) Closed-loop Evaporative Cooling System

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New Technology (Eco-friendly, closed-loop dry-cooling system

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• Eco-friendly, closed-loop, dry-cooling system. This intelligent process cooling system provides economic and environmental advantages that are particularly important to industry today.

• These closed-loop systems are designed to dramatically reduce water use and keep water clean while minimizing costly chemicals.

Description

Components

• Fluid Cooler (Contains air-to-liquid heat exchanger with the fan(s).

• Pump• Control Skid• Coolant• Piping

Closed-loop design ensures that the process water is never exposed to outside elements and never disposed of into ground water.

Water returning from a process is pumped into a heat exchanger and cooled with ambient air, providing clean water at the right temperature year-round.

Intelligent control systems maintain the desired water temperatures, even during extreme hot and cold weather conditions.

Eco-friendly, closed-loop dry-cooling system

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Highlights

• closed-loop systems are designed to dramatically reduce water use and keep water clean while minimizing costly chemicals.

• these systems save up to 95 percent of water consumption typically associated with conventional tower/central chiller systems.

• In the quest for greater efficiency, sustainability and competitiveness, such potential results should not be overlooked by any processor.

Conclusion

Energy Saving Cost Effective Efficient Sustainable Adaptable

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Questions and Answers

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