Mango Processing HVAC Systems

Technical Overview

Mango processing facilities require specialized HVAC design to accommodate multiple temperature zones ranging from hot water treatment at 46°C to cold storage near the critical chilling injury threshold. The primary challenge in mango handling is maintaining temperatures above 10°C to prevent irreversible chilling damage while controlling decay organisms through thermal treatment and controlled atmosphere storage.

The HVAC system must support distinct operational zones: receiving and hot water treatment, cooling and temporary storage, ripening rooms with ethylene injection, and distribution holding areas. Each zone requires precise temperature and humidity control with minimal cross-contamination.

Hot Water Treatment Facility Design

Hot water treatment remains the primary post-harvest disease control method for mangoes, requiring dedicated HVAC support for high-temperature, high-humidity environments.

Treatment Room Environmental Control

Hot water treatment facilities generate substantial latent and sensible heat loads requiring dedicated exhaust and makeup air systems. Treatment rooms typically operate at 35-40°C ambient temperature with relative humidity exceeding 90% during operation.

Ventilation Requirements:

• Minimum 15 ACH during treatment operations
• Exhaust air handling to remove steam and moisture
• Makeup air preheated to 25-30°C to minimize thermal shock
• Corrosion-resistant ductwork and terminals (stainless steel or epoxy-coated)
• Pressure relief to prevent excessive positive pressure

Heat Recovery Considerations

Hot water treatment generates recoverable thermal energy through both the treatment water heat loss and the humid exhaust air stream.

Recovery Strategies:

• Water-to-water heat exchangers for treatment tank makeup water heating
• Run-around coil systems between exhaust and makeup air streams
• Heat pump systems extracting energy from 40-50°C exhaust air
• Expected energy recovery: 40-60% of treatment heat input

Chilling Injury Prevention

Mango cultivars exhibit extreme sensitivity to chilling injury at temperatures below 10-13°C, depending on maturity and variety. Chilling injury manifests as uneven ripening, increased decay susceptibility, and surface pitting.

Critical Temperature Control

Temperature control systems for mango storage must maintain temperatures within ±0.5°C of setpoint to prevent any exposure below the chilling injury threshold.

Control System Requirements:

• High-accuracy RTD or thermistor sensors (±0.1°C accuracy)
• Multiple temperature monitoring points throughout storage volume
• Rapid response refrigeration capacity (2-3 times calculated load)
• Fail-safe controls preventing temperature undershoot
• Alarm systems for any temperature below 9°C

Airflow Management

Excessive air velocity across mango surfaces increases moisture loss and can cause surface temperature depression below safe limits even when bulk air temperature is acceptable.

Design Parameters:

• Air velocity at fruit surface: 0.15-0.25 m/s maximum
• Supply air temperature differential: 2-3°C below space temperature
• Large duct systems with multiple low-velocity diffusers
• Indirect cooling through building structure where feasible

Ripening Room Specifications

Controlled ripening rooms convert green mature mangoes to market-ready fruit through precise temperature, humidity, and ethylene concentration control.

Environmental Conditions

Ripening rooms require significantly higher temperatures than storage areas, with enhanced ventilation to distribute ethylene uniformly and remove respiration products.

Ethylene Distribution System

Uniform ethylene distribution requires dedicated circulation systems independent of the primary HVAC airflow to ensure even exposure across all fruit.

System Components:

• Dedicated ethylene injection points at multiple locations
• High-velocity circulation fans (50-100 ACH internal circulation)
• Ethylene concentration monitoring at supply and return
• Catalytic ethylene scrubbers for exhaust air treatment
• Pressure-independent flow control for consistent distribution

HVAC Design Requirements

Ripening rooms operate as batch processes with varying heat loads as fruit respiration increases during ripening.

Cooling Capacity:

• Base load: 150-200 W/m³ of room volume
• Peak respiration load: Additional 100-150 W/tonne of fruit
• Lighting and fan heat: 50-75 W/m³
• Safety factor: 1.25-1.5 times calculated load

Dehumidification:

• Moisture removal capacity: 0.5-1.0 kg/h per tonne of fruit
• Reheat capacity to maintain temperature during dehumidification
• Desiccant systems for precise humidity control in smaller installations

Air Distribution

Proper air distribution prevents temperature stratification and ensures uniform ripening across the entire fruit load.

Design Criteria:

• Supply air temperature differential: 1-2°C below room temperature
• Air changes per hour: 20-30 ACH
• Horizontal airflow pattern preferred over vertical
• Return air near floor level to capture CO₂-rich air
• Perforated wall or ceiling diffusers for even distribution

Controlled Atmosphere Options

Controlled atmosphere storage extends mango shelf life by reducing respiration rates and delaying ripening, though application remains limited compared to temperate fruits.

CA Storage Conditions

Modified atmosphere storage for mangoes typically employs oxygen reduction and CO₂ elevation within tolerable limits.

CA System Design

Mango CA storage requires gas-tight construction with atmosphere modification equipment and continuous monitoring.

System Components:

• Nitrogen generation system (PSA or membrane type)
• CO₂ scrubbing system (lime or chemical absorption)
• O₂ and CO₂ analyzers with continuous monitoring
• Humidity control to maintain 90-95% RH
• Circulation fans for atmosphere uniformity

Construction Requirements:

• Gas-tight door seals with inflatable gaskets
• Vapor-impermeable insulation system
• Pressure relief valves (±250 Pa operating range)
• Personnel safety monitoring and alarms
• Emergency ventilation system

Processing Line Environmental Control

Processing areas where mangoes are sorted, graded, and packed require environmental conditions balancing worker comfort with product quality maintenance.

Processing Room Conditions

Processing spaces must prevent fruit temperature rise while maintaining acceptable conditions for manual labor.

Load Calculations

Processing line loads include equipment heat, lighting, personnel, and product respiration throughout the handling process.

Heat Gain Sources:

• Personnel: 120-150 W per person (moderate work)
• Lighting: 15-20 W/m² (LED high-bay systems)
• Conveyors and equipment: 50-75 W/m of line length
• Fruit respiration: 50-100 W/tonne (temperature dependent)
• Building envelope: Calculate per ASHRAE fundamentals

Ventilation Strategy

Processing areas require substantial outdoor air for odor control and latent load management while maintaining positive pressure relative to non-conditioned spaces.

Design Approach:

• Outdoor air: 15-20 L/s per person minimum
• Total air changes: 10-15 ACH
• Positive pressure: 12-25 Pa relative to adjacent spaces
• Exhaust at washing and treatment stations
• Air filtration: MERV 8-11 for particulate control

Mango Cultivar-Specific Requirements

Different mango cultivars exhibit varying temperature sensitivity and storage characteristics requiring HVAC system flexibility.

Refrigeration System Considerations

Mango processing refrigeration systems must provide stable capacity at the relatively high evaporator temperatures required to prevent chilling injury.

Evaporator Design

Higher evaporator temperatures reduce available temperature differential, requiring larger heat transfer surface area.

Design Parameters:

• Evaporator temperature: 7-9°C (avoiding <5°C approach)
• Temperature differential: 3-5°C below room temperature
• Coil surface area: 1.5-2.0 times standard cold storage
• Defrost cycles: Time-initiated, minimized to reduce temperature fluctuation
• Multiple small coils preferred over single large units

Refrigerant Selection

Refrigerant choice impacts system efficiency at the moderate temperature lift conditions in mango storage.

Suitable Refrigerants:

• R-404A: Good capacity, moderate efficiency
• R-134a: Lower capacity, better efficiency at high suction temperatures
• R-290 (Propane): Excellent efficiency, flammability considerations
• R-717 (Ammonia): Industrial facilities, highest efficiency
• CO₂ cascade: Suitable for hot climates, complex controls

Quality Control Integration

HVAC monitoring systems should integrate with quality control programs tracking fruit condition throughout processing.

Monitored Parameters:

• Temperature at multiple points in each storage zone
• Relative humidity in storage and ripening areas
• Ethylene concentration in ripening rooms
• CO₂ levels in CA storage
• Air velocity at critical locations
• Refrigeration system performance metrics

Data Logging:

• Minimum 15-minute intervals for all critical parameters
• Alarm generation for out-of-spec conditions
• Trending analysis for quality correlation
• Export capability for quality system documentation

Energy Efficiency Strategies

Mango processing facilities in tropical climates face high cooling loads requiring attention to energy efficiency.

Efficiency Measures:

• Night sky radiation cooling during low-load periods
• Thermal storage for demand shifting
• Variable speed compressors and fans
• High-efficiency motors (IE3 or better)
• LED lighting throughout
• Heat recovery from hot water treatment
• Building envelope optimization (high R-value insulation)
• Evaporative cooling for makeup air pre-cooling

Conclusion

Mango processing HVAC systems require careful integration of thermal treatment capabilities, chilling injury prevention, ripening control, and processing environment maintenance. The narrow acceptable temperature range near the chilling injury threshold demands high-precision control systems and conservative design approaches prioritizing temperature stability over first cost optimization. Successful installations balance these technical requirements with energy efficiency and operational flexibility across varying product volumes and cultivar specifications.