Soft Drink Production

Soft drink production requires precise refrigeration control for carbonation, syrup preparation, and product quality maintenance. The refrigeration system must deliver consistent cooling across multiple process stages while maintaining strict temperature tolerances that directly affect CO2 solubility, flavor stability, and production efficiency.

Process Cooling Requirements

Soft drink manufacturing involves three primary refrigeration loads:

Syrup Preparation

• Initial cooling of hot syrup from pasteurization (85-95°C) to storage temperature (4-10°C)
• Continuous cooling to maintain syrup at dispensing temperature
• Heat load from sugar dissolution and mixing operations

Carbonation Water Chilling

• Primary cooling requirement for maximizing CO2 absorption
• Target water temperature: 0.5-4°C for optimal carbonation
• Continuous process cooling under varying production rates

Product Cooling

• Final beverage temperature reduction post-mixing
• Packaging line temperature maintenance
• Quality assurance cooling for laboratory samples

CO2 Solubility and Temperature Relationship

Carbon dioxide solubility in water follows Henry’s Law, with temperature exerting dominant control over gas absorption capacity. The relationship is inversely proportional - lower temperatures dramatically increase CO2 solubility.

Temperature Control Criticality Each 1°C increase above optimal chilling temperature reduces CO2 absorption capacity by approximately 3%. For high-volume production lines operating at 1,000 bottles per minute, temperature variations of ±0.5°C can affect carbonation consistency across thousands of units per hour.

Carbonation Water Chilling Systems

Plate Heat Exchanger Configuration

The dominant cooling method for carbonation water uses brazed or gasketed plate heat exchangers operating with glycol or ammonia refrigerant.

Design Parameters

• Approach temperature: 1-2°C
• Water inlet temperature: 10-20°C (seasonal variation)
• Water outlet temperature: 0.5-4°C
• Glycol supply temperature: -3 to 0°C
• Heat exchanger effectiveness: 0.85-0.92

Cooling Load Calculation

Q = ṁ × cp × ΔT

Where:

• Q = cooling load (kW)
• ṁ = water mass flow rate (kg/s)
• cp = specific heat of water (4.18 kJ/kg·K)
• ΔT = temperature difference (K)

For a production line processing 10,000 L/h of carbonated water:

• Mass flow rate: 2.78 kg/s
• Temperature reduction: 15°C to 2°C (ΔT = 13 K)
• Cooling load: 2.78 × 4.18 × 13 = 151 kW

Shell-and-Tube Chiller Systems

Large production facilities often employ shell-and-tube chillers for carbonation water, particularly when integrating with central ammonia refrigeration plants.

Syrup Cooling Systems

Syrup cooling presents unique challenges due to high viscosity and sugar content affecting heat transfer characteristics.

Syrup Physical Properties at 65°Brix

• Density: 1,320 kg/m³
• Viscosity: 50-150 cP (temperature dependent)
• Specific heat: 2.8 kJ/kg·K
• Heat transfer coefficient: 60-75% of water

Scraped Surface Heat Exchangers

High-viscosity syrups require mechanical enhancement of heat transfer through scraped surface exchangers.

Operating Characteristics

• Rotor speed: 100-400 rpm
• Product residence time: 30-120 seconds
• Heat transfer coefficient: 500-1,200 W/m²·K
• Temperature reduction: 85°C to 10°C in single pass

Heat Load Components

1. Sensible cooling from pasteurization temperature
2. Sugar dissolution heat (for in-line mixing systems)
3. Agitation heat input from mixing equipment
4. Ambient heat gain from piping and vessels

Syrup Storage Tank Cooling

Post-process syrup storage requires continuous cooling to prevent microbial growth and maintain viscosity for accurate dispensing.

Carbonation Process Parameters

Pressure-Temperature-Volume Relationships

Carbonation level is specified in volumes of CO2, where one volume equals the amount of CO2 gas (at 0°C and 1 atm) dissolved per unit volume of liquid.

Typical Carbonation Levels by Product Type

Henry’s Law Application

C = kH × P

Where:

• C = CO2 concentration in liquid (mol/L)
• kH = Henry’s constant (temperature dependent)
• P = partial pressure of CO2 (bar)

At 2°C, kH = 0.066 mol/(L·bar) At 10°C, kH = 0.044 mol/(L·bar)

This 33% reduction in kH between 2°C and 10°C directly translates to reduced CO2 absorption capacity, requiring either higher pressures or longer contact times to achieve target carbonation levels.

Refrigeration System Design

Glycol Loop Configuration

Most modern soft drink facilities use secondary glycol loops for process cooling, providing temperature stability and eliminating direct ammonia contact with product.

Glycol System Specifications

• Glycol concentration: 30-35% propylene glycol
• Supply temperature: -3 to 0°C
• Return temperature: 3 to 8°C
• Temperature differential: 5-8 K
• Freezing protection: -15°C minimum
• System pressure: 3-5 bar

Distribution Design

• Main supply header: 150-300 mm diameter
• Branch circuits: 50-100 mm diameter
• Flow velocity: 1.0-2.0 m/s
• Pressure drop limit: 100 kPa total system
• Isolation valves at each process connection

Chiller Plant Sizing

Total refrigeration capacity must account for all simultaneous cooling loads plus safety factors.

Load Components

1. Carbonation water chilling: 150-800 kW (primary load)
2. Syrup cooling: 50-200 kW
3. Product cooling: 30-150 kW
4. Cold storage rooms: 20-100 kW
5. Laboratory and QC: 5-20 kW
6. Distribution system losses: 10-15% of total

Design Example for 20,000 L/h Production Facility

Temperature Control and Monitoring

Critical Control Points

Regulatory compliance and quality assurance require continuous monitoring of specific temperature points throughout production.

Mandatory Monitoring Locations

1. Carbonation water supply (±0.5°C tolerance)
2. Syrup storage tanks (±1.0°C tolerance)
3. Final product temperature (±1.0°C tolerance)
4. Glycol supply and return (±0.5°C tolerance)
5. CO2 storage area ambient (±2.0°C tolerance)

Control System Architecture

• PLC-based central control
• RTD sensors (Pt100, Class A accuracy)
• Analog output: 4-20 mA signals
• Data logging: 1-minute intervals
• Alarm thresholds: ±0.3°C from setpoint
• Response time: < 30 seconds to full correction

Carbonation Quality Control

CO2 Volume Measurement Direct measurement uses pressure-temperature relationships and corrects for water vapor pressure:

V = (P - Pw) / (Patm × kH(T))

Where:

• V = volumes of CO2
• P = total pressure in beverage (absolute)
• Pw = water vapor pressure at temperature T
• Patm = atmospheric pressure
• kH(T) = Henry’s constant at temperature T

Inline Monitoring Parameters

• CO2 content: ±0.1 volumes accuracy
• Temperature: ±0.2°C accuracy
• Pressure: ±0.05 bar accuracy
• Flow rate: ±2% accuracy
• Sampling frequency: Continuous or per batch

Energy Efficiency Optimization

Heat Recovery Opportunities

Soft drink production generates significant waste heat that can offset refrigeration loads through heat recovery.

Integrated Heat Recovery System A 20,000 L/h production facility can recover 150-250 kW of waste heat, reducing overall energy consumption by 15-25% compared to conventional systems without heat recovery.

Variable Speed Drive Implementation

Carbonation water flow varies with production rate, making variable speed pumps and refrigeration compressors highly effective for energy savings.

VFD Applications

• Glycol circulation pumps: 30-50% energy reduction
• Chiller compressors: 20-40% energy reduction at partial load
• Cooling tower fans: 40-60% energy reduction
• Carbonation pumps: 25-35% energy reduction

Operating at 70% production capacity with VFD control typically reduces refrigeration energy consumption by 25-30% compared to constant-speed operation with capacity control.

System Maintenance Requirements

Weekly Tasks

• Verify carbonation water temperature and CO2 levels
• Check glycol concentration and pH
• Inspect heat exchanger approach temperatures
• Monitor refrigerant charge indicators

Monthly Tasks

• Clean carbonation system filters
• Inspect syrup cooling coils for fouling
• Calibrate temperature sensors
• Test emergency shutdown systems

Quarterly Tasks

• Heat exchanger cleaning (CIP or disassembly)
• Glycol system water analysis
• Refrigerant leak detection survey
• Compressor oil analysis

Annual Tasks

• Complete refrigeration system inspection
• Heat exchanger pressure testing
• Control system calibration verification
• Thermal insulation condition assessment

Proper maintenance ensures carbonation consistency, prevents product quality issues, and maintains energy efficiency throughout the facility lifecycle.

Sections