Parts of Chiller System

Chiller components are categorized based on their roles:

1. Refrigeration Cycle Components: For operation and control of the refrigeration cycle.
2. Water Distribution Components: Parts involved in distributing chilled water.

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Main components of chiller

Component	Types
Compressor	Piston, Scroll, Screw, Centrifugal
Evaporator	Shell-and-Tube (Flooded), Shell-and-Tube (Dry), Shell and Coil, Double Tube, Baudelot, Plate
Condenser	Shell-and-Tube, Brazed Plate, Coaxial Tube, Tubular
Expansion Valve	Bulb Valve, Electronic Time-Controlled Valve, Variable-Flow Electronic Valve
Refrigerant Control Valves	Solenoid, Pressure-Regulating, Check
Refrigerant Receiver	Liquid receiver at the condenser outlet, Liquid accumulator before the compressor
Filter-Drier	Positioned before the expansion valve
Pressure Switch	High-pressure, Low-pressure
Pressure Sensors	Low-pressure sensor, High-pressure sensor
Temperature Sensors	NTC/PTC, PT100, PT1000

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Water Distribution Components

Component	Types
Heat Exchangers (Air/Water)	Fan Coil, Air Handling Unit
Flow Switches	Paddle
Flow Control Valves	Solenoid, Check, Ball, Flow-Regulating Valves
Water Filter	Y-Strainer
Primary Pump	Centrifugal, VFD Centrifugal
Secondary Pump	Centrifugal, VFD Centrifugal
Cooling Tower Pump	Centrifugal, VFD Centrifugal
Cooling Towers	Induced Draft, Forced Draft, Crossflow

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Key Components of a Chiller

1. Evaporator: Removes heat from water, transferring it to the refrigerant to generate chilled water.
2. Compressor: Transfers the refrigerant with absorbed heat from the evaporator to the condenser under high pressure.
3. Condenser: Releases heat absorbed by the refrigerant to the environment.
4. Expansion Valve: Reduces refrigerant pressure, lowering its temperature before returning to the evaporator.
5. Cooling Towers: Cools water circulating to the chiller’s condenser.
6. Control System: Optimizes and manages the refrigeration cycle.

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Evaporators in Detail

1. Flooded Shell-and-Tube Evaporator:

• Contains liquid refrigerant in a shell where heat from the chilled water evaporates the refrigerant.
• Features: Constant refrigerant level via float valve, high heat transfer efficiency, and robust design for fluids of low viscosity (~6 cP).

2. Dry Shell-and-Tube Evaporator:

• Refrigerant flows inside tubes; chilled water flows outside.
• Includes deflectors to increase turbulence, enhancing heat transfer.
• Requires less refrigerant charge and ensures positive oil return.

3. Shell-and-Coil Evaporator:

• Spiral-shaped coils enclosed in a shell, suited for low-capacity needs.
• Often used for potable water cooling and specific industrial processes.

4. Double-Tube Evaporator:

• Uses concentric tubes, with refrigerant in the annular space and liquid in the inner tube.
• Efficient heat transfer through counterflow design.

5. Baudelot Evaporator:

• Horizontal tubes with liquid flowing over their surface.
• Frequently used in food and beverage industries for milk and wine cooling.

6. Plate Evaporator:

• Stainless steel plates facilitate heat exchange through counterflow of fluids.
• Common in breweries and dairies due to easy cleaning and reduced refrigerant usage.

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Key Considerations for Evaporator Types

• Flooded Evaporators: High efficiency, suitable for process fluids with low viscosity, but require large refrigerant loads.
• Dry Evaporators: More compact, require less refrigerant, but slightly lower efficiency.
• Plate Evaporators: Ideal for close temperature approaches and hygienic applications.

Optimized Description of Water-Cooled Chiller Components

A water-cooled chiller consists of various essential components for proper operation. Key parts include the condensers, cooling tower, compressor, and expansion valve. Below is a detailed description of each:

1. Condensers in Water-Cooled Chillers

Condensers are crucial for transferring heat from the refrigerant to the water. There are three main types:

• Shell and Tube Condenser
  • The most common type used in water-cooled chillers.
  • Refrigerant is contained in the shell, while water flows through copper tubes.
  • Advantages: high efficiency, easy maintenance and cleaning, low likelihood of fouling.
  • Disadvantages: not ideal for limited space applications, higher cost.
• Brazed Plate Condenser
  • Compact design, ideal for space-constrained environments.
  • Non-ferrous construction resistant to corrosion and highly efficient in heat transfer.
  • Advantages: cost-effective, thermal efficiency.
  • Disadvantages: prone to clogging, complex cleaning if fouled.
• Coaxial Tube Condenser
  • Compact with a counterflow design for maximum heat transfer.
  • Advantages: anti-fouling characteristics, effective under high pressure and temperature conditions.
  • Disadvantages: chemical cleaning required for fouling, higher cost.

2. Cooling Tower

A critical component for releasing heat into the environment. This system operates independently of the chilled water circuit, transferring heat from the hot water coming from the condenser to the surrounding air.

• Operation: Cold water is pumped from the cooling tower to the condenser, raising its temperature by approximately 10°F after absorbing the refrigerant’s heat.

3. Chiller Compressor

The compressor is the heart of the chiller, with various types suited for different capacities and applications:

• Piston Compressor: Less commonly used due to lower energy efficiency.
• Scroll Compressor: Ideal for low-capacity chillers; multiple units can increase cooling capacity.
• Screw Compressor: Suitable for medium to high-capacity chillers, known for low vibration and long service life.
• Centrifugal Compressor: Exclusively used in high-capacity chillers with water-cooled condensers.

4. Expansion Valve

Regulates the refrigerant flow into the evaporator, ensuring the low pressure needed for the cooling process. Two main types are available:

• Bulb Expansion Valve
  • Operates using a special fluid in the bulb to regulate pressure.
  • Maintains a 10°F temperature difference (superheat) for optimal performance.
• Electronic Expansion Valve
  • More precise, using temperature and pressure sensors connected to a controller.
  • Types:
    • Time-based opening and closing control (e.g., Danfoss AKV series).
    • Variable step, with precise positioning via stepper motor (e.g., Danfoss ETS series).

Electronic Controller for Chillers

The electronic controller in chillers plays a critical role in managing various operations. It is designed with advanced features to ensure optimal performance, efficiency, and reliability. Below is an overview of its components and functionalities:

Features of the Chiller Electronic Controller

1. Controller Configuration:
   • The controller can consist of multiple electronic boards.
   • In smaller capacity chillers, all functions can be integrated into a single board.
   • Larger chillers often use a main board and several slave boards.
     • Slave boards handle specific controls, such as compressors, fans, or pumps.
   • Communication between the main and slave boards occurs via an internal communication bus.
2. Compressor Control:
   • The compressor board manages individual compressors or compressor stations under the main board’s command.
   • Electronic control ensures proper compressor operation, including:
     • Adjusting runtime and minimum off time to prevent irregular operation.
     • Balancing compressor runtime across all units to equalize usage.
   • Allows for:
     • Delayed engagement of multiple compressors.
     • Selection of operation modes, such as sequential (first-on, last-off) or cyclic (equal runtime).
3. Evaporator Control:
   • Can manage an electronic expansion valve, optimizing suction pressure to reduce energy consumption.
   • Ensures the lowest possible superheat, approaching the performance of a flooded evaporator system.
4. Additional Control Modules:
   • Manages components such as condenser or cooling tower fans, water pumps, oil pumps, or additional motor cooling valves.
   • Includes functionality to adjust water pump speeds to match system capacity with demand.
5. Sensor Integration:
   • Reads data from various sensors, including:
     • Oil pressure.
     • Economizer pressure.
     • Condensation and recovery temperatures.

Sensors in the Chiller Control System

1. Temperature Sensors:
   • Detect temperatures at critical points and send data to the microprocessor.
   • Common placements:
     • Evaporator outlet.
     • Compressor outlet.
     • Condenser.
     • Cooler water outlet and inlet.
     • Compressor motor.
   • Types of temperature sensors:
     • RTD Sensors:
       • Examples: PT100, PT1000.
       • Feature high accuracy and reliability, with resistance changing linearly with temperature.
       • Made of platinum, calibrated for stable operation.
       • Failures typically trigger open-circuit alarms in the control module.
     • Thermistor Sensors:
       • Examples: NTC and PTC.
       • Non-linear resistance changes with temperature, less precise than RTDs.
       • NTC: Resistance decreases with rising temperature.
       • PTC: Resistance increases with rising temperature.
2. Pressure Sensors:
   • Provide voltage or current signals that vary linearly with measured pressure.
   • Common models:
     • AKS32/AKS32R: Voltage signals.
     • AKS33: Current signals.

Hydraulic Circuit Components

1. Water Flow Switch:
   • Installed to protect the evaporator from reduced chilled water flow, preventing freezing risks.
   • Typically placed in a straight pipe section following manufacturer guidelines.

By combining these features, the electronic controller ensures smooth operation, energy efficiency, and enhanced reliability for water chillers.