Plum Storage

Plum storage requires precise environmental control to prevent physiological disorders while maintaining fruit quality throughout the storage period. The refrigeration system must accommodate variety-specific temperature requirements, maintain high relative humidity, and provide uniform air distribution to prevent both chilling injury and desiccation.

Storage Temperature Requirements by Variety

Temperature management represents the critical control parameter for plum storage. Variety-specific requirements determine refrigeration system setpoints and control strategies.

Japanese Plums (Prunus salicina)

Japanese plums require the lowest storage temperatures among plum varieties but exhibit variable chilling injury susceptibility.

Control Strategy: Maintain setpoint at variety-specific optimum with ±0.3°C (±0.5°F) tolerance. Install RTD sensors with 0.1°C resolution for precise control.

European Plums (Prunus domestica)

European plums tolerate slightly higher storage temperatures and generally exhibit lower chilling injury susceptibility.

Control Strategy: European plums permit wider temperature tolerance (±0.5°C) compared to Japanese varieties, reducing refrigeration system cycling frequency.

Humidity Control Requirements

Plums require high relative humidity to prevent moisture loss while avoiding surface condensation that promotes fungal growth.

Target Humidity Parameters

Optimal Range: 90-95% RH Absolute Minimum: 88% RH Vapor Pressure Deficit: 0.06-0.15 kPa

Psychrometric Relationships

The saturation vapor pressure at typical plum storage temperatures:

For temperature T in °C: $$e_s = 0.6108 \exp\left(\frac{17.27T}{T + 237.3}\right) \text{ kPa}$$

At 0°C storage temperature: $$e_s(0°C) = 0.6108 \text{ kPa}$$

For 90% RH: $e_a = 0.90 \times 0.6108 = 0.550$ kPa For 95% RH: $e_a = 0.95 \times 0.6108 = 0.580$ kPa

Vapor pressure deficit (VPD): $$VPD = e_s - e_a$$

At 90% RH: $VPD = 0.6108 - 0.550 = 0.061$ kPa At 95% RH: $VPD = 0.6108 - 0.580 = 0.031$ kPa

Moisture Loss Rate

Weight loss rate depends on vapor pressure deficit and fruit surface characteristics:

$$\frac{dm}{dt} = k \cdot A \cdot VPD$$

Where:

• dm/dt = moisture loss rate (kg/h)
• k = mass transfer coefficient (0.8-1.2 × 10⁻⁶ kg/(m²·h·kPa) for plums)
• A = total fruit surface area (m²)
• VPD = vapor pressure deficit (kPa)

Example Calculation: For 10,000 kg plums (average diameter 55 mm, surface area 95 cm²/fruit, 133 fruits/kg):

Total surface area: $A = 10,000 \times 133 \times 0.0095 = 12,635$ m²

At 90% RH (VPD = 0.061 kPa): $$\frac{dm}{dt} = 1.0 \times 10^{-6} \times 12,635 \times 0.061 = 0.77 \text{ kg/h}$$

Daily moisture loss: $0.77 \times 24 = 18.5$ kg/day (0.185% per day)

At 85% RH (VPD = 0.092 kPa): $$\frac{dm}{dt} = 1.0 \times 10^{-6} \times 12,635 \times 0.092 = 1.16 \text{ kg/h}$$

Daily moisture loss: $1.16 \times 24 = 27.8$ kg/day (0.278% per day)

Conclusion: Reducing RH from 90% to 85% increases moisture loss by 50%, demonstrating the critical importance of humidity control.

Humidification System Design

Ultrasonic Humidifiers: Preferred for plum storage due to minimal heat input and fine droplet size (1-5 μm) that evaporates before settling on fruit surfaces.

Humidification capacity requirement: $$Q_h = \frac{dm}{dt} + L_{inf}$$

Where:

• Q_h = required humidification capacity (kg/h)
• dm/dt = calculated moisture loss from fruit
• L_inf = moisture loss through infiltration

Infiltration moisture loss: $$L_{inf} = \frac{V \cdot n \cdot \rho_{air} \cdot (W_{out} - W_{in})}{3600}$$

Where:

• V = storage room volume (m³)
• n = air change rate (0.5-1.0 ACH for sealed cold storage)
• ρ_air = air density (1.29 kg/m³ at 0°C)
• W_out, W_in = humidity ratio outside and inside storage (kg water/kg dry air)

Chilling Injury Prevention

Chilling injury represents a complex physiological response to low-temperature storage that varies significantly among plum varieties.

Chilling Injury Mechanisms

Primary Symptoms:

• Internal flesh browning (oxidation of phenolic compounds)
• Gel breakdown (pectin depolymerization)
• Mealiness (loss of cell-to-cell adhesion)
• Surface pitting (localized tissue collapse)
• Failure to ripen (ethylene perception impairment)
• Off-flavor development (fermentative metabolism)

Temperature-Time Relationship:

Chilling injury accumulates according to temperature-time exposure:

$$CI_{index} = \sum_{i=1}^{n} t_i \cdot f(T_i)$$

Where:

• CI_index = cumulative chilling injury index
• t_i = time period at temperature T_i (days)
• f(T_i) = temperature sensitivity function

For susceptible Japanese plums: $$f(T) = \begin{cases} 0 & T \geq 5°C \ 0.5(T-5)^2 & 0 < T < 5°C \ 12.5 + 0.2T & T \leq 0°C \end{cases}$$

Example: Santa Rosa plums stored at 0°C for 21 days: $$CI_{index} = 21 \times 12.5 = 262.5$$

Critical threshold for visible symptoms: CI_index > 200

Conditioning Treatments

Pre-storage Conditioning: Exposure to 15-20°C for 1-2 days before cold storage reduces subsequent chilling injury by 30-50%.

Intermittent Warming: Periodic warming cycles interrupt chilling injury development.

Recommended protocol:

• Store at optimal temperature for 7-10 days
• Warm to 10-15°C for 1-2 days
• Return to storage temperature
• Repeat cycle as needed

Temperature Cycling Refrigeration Load:

Warming load from 0°C to 15°C: $$Q_{warm} = m \cdot c_p \cdot \Delta T$$

For 10,000 kg plums (c_p = 3.8 kJ/kg·K): $$Q_{warm} = 10,000 \times 3.8 \times 15 = 570,000 \text{ kJ} = 158 \text{ kWh}$$

Warming at 1°C/hour requires: 158 kWh / 15 hours = 10.5 kW heating capacity

Internal Breakdown Considerations

Internal breakdown manifests as translucent flesh, gel formation, and loss of structural integrity without external symptoms.

Breakdown Mechanisms

Gel Formation: Pectin degradation enzymes (polygalacturonase, pectin methylesterase) remain active at low temperatures, progressively degrading cell wall structure.

Enzyme activity temperature relationship (Arrhenius): $$k = A \cdot e^{-E_a/(RT)}$$

Where:

• k = enzyme reaction rate
• A = pre-exponential factor
• E_a = activation energy (typically 50-70 kJ/mol for pectinases)
• R = gas constant (8.314 J/mol·K)
• T = absolute temperature (K)

At 0°C (273 K): Enzyme activity reduced to approximately 10-15% of activity at 20°C, but not completely inhibited.

Monitoring and Detection

Non-Destructive Methods:

1. Near-Infrared Spectroscopy (NIRS)

   • Wavelength range: 700-2500 nm
   • Penetration depth: 5-10 mm
   • Detects changes in soluble solids and moisture distribution

2. Acoustic Firmness Testing

   • Frequency response: 100-1000 Hz
   • Correlates with tissue integrity
   • Non-contact measurement

3. X-ray CT Imaging

   • Resolution: 0.5-1.0 mm
   • Identifies internal cavities and gel pockets
   • Batch sampling protocol

Controlled Atmosphere Benefits

Modified atmosphere storage reduces internal breakdown incidence by 40-60%.

Target Gas Composition:

• O₂: 1-3%
• CO₂: 3-5%
• N₂: Balance

Respiratory Gas Exchange:

Oxygen consumption rate at 0°C: $$R_{O_2} = 2-5 \text{ mg CO}_2/\text{kg·h}$$

For 10,000 kg plums: $$R_{O_2} = 10,000 \times 3.5 \times 10^{-3} = 35 \text{ g CO}_2/\text{h}$$

At 0°C, 1 atm: 1 mole CO₂ = 44 g occupies 22.4 L

Volume flow rate: $\frac{35}{44} \times 22.4 = 17.8$ L/h = 0.30 L/min

CA System Sizing:

Nitrogen generator capacity: $$Q_{N_2} = \frac{V_{room} \cdot (0.21 - x_{O_2})}{t_{pulldown}}$$

For 500 m³ room, target 2% O₂, 24-hour pulldown: $$Q_{N_2} = \frac{500 \times (0.21 - 0.02)}{24} = 3.96 \text{ m}^3/\text{h}$$

Add 20% safety factor: Required capacity = 4.75 m³/h N₂ at 95-99% purity

Storage Duration by Variety

Maximum storage duration depends on cultivar, harvest maturity, and pre-storage handling.

Expected Storage Life

Quality Degradation Kinetics

Firmness loss follows first-order kinetics:

$$F(t) = F_0 \cdot e^{-kt}$$

Where:

• F(t) = firmness at time t (N)
• F_0 = initial firmness (N)
• k = rate constant (day⁻¹)
• t = storage time (days)

At 0°C: k = 0.015-0.025 day⁻¹ for Japanese plums At 2°C: k = 0.025-0.040 day⁻¹ for Japanese plums

Temperature coefficient (Q₁₀): 1.8-2.2

Rate constant temperature relationship: $$k(T_2) = k(T_1) \cdot Q_{10}^{(T_2-T_1)/10}$$

Example: Plums with initial firmness 60 N stored at 0°C (k = 0.020 day⁻¹):

After 28 days: $$F(28) = 60 \cdot e^{-0.020 \times 28} = 60 \cdot e^{-0.56} = 60 \times 0.571 = 34.3 \text{ N}$$

Minimum acceptable firmness for most markets: 25-30 N

Refrigeration System Design

Plum storage refrigeration systems must provide precise temperature control, high evaporator efficiency to maintain humidity, and uniform air distribution.

Cooling Load Components

Product Load:

Field heat removal from 20°C to 0°C: $$Q_{product} = \frac{m \cdot c_p \cdot \Delta T}{t_{cool}}$$

For 10,000 kg plums, 24-hour cooling period: $$Q_{product} = \frac{10,000 \times 3.8 \times 20}{24 \times 3600} = 8.80 \text{ kW}$$

Respiration Heat: $$Q_{resp} = m \cdot r$$

Where r = specific heat of respiration at 0°C = 0.010-0.015 W/kg

$$Q_{resp} = 10,000 \times 0.012 = 120 \text{ W} = 0.12 \text{ kW}$$

Transmission Load (well-insulated room, U = 0.20 W/m²·K, 300 m² surface area, 20°C ambient): $$Q_{trans} = U \cdot A \cdot \Delta T = 0.20 \times 300 \times 20 = 1,200 \text{ W} = 1.20 \text{ kW}$$

Infiltration Load (0.5 ACH, 500 m³ room volume):

Volumetric flow: $V = 500 \times 0.5 / 3600 = 0.0694$ m³/s

Sensible load: $$Q_{sens} = \rho \cdot c_p \cdot V \cdot \Delta T = 1.29 \times 1.005 \times 0.0694 \times 20 = 1.79 \text{ kW}$$

Latent load (outdoor air at 20°C, 60% RH, W = 0.0088 kg/kg; storage air W = 0.0038 kg/kg): $$Q_{lat} = \rho \cdot h_{fg} \cdot V \cdot \Delta W = 1.29 \times 2500 \times 0.0694 \times (0.0088 - 0.0038) = 1.12 \text{ kW}$$

Lighting, Motors, Personnel: 0.50 kW (minimal during storage period)

Total Design Load: $$Q_{total} = 8.80 + 0.12 + 1.20 + 1.79 + 1.12 + 0.50 = 13.53 \text{ kW}$$

Add 15% safety factor: Design capacity = 15.6 kW (4.4 tons)

Evaporator Selection

Coil Temperature Differential (TD):

Standard practice: TD = 4-6°C for standard humidity storage Plum storage requirement: TD = 2-3°C to maintain 90-95% RH

Evaporator temperature: $T_{evap} = T_{room} - TD = 0 - 2.5 = -2.5°C$

Surface Area Calculation:

$$Q = U_{coil} \cdot A_{coil} \cdot LMTD$$

For U_coil = 25 W/m²·K (finned coil, forced convection):

LMTD with refrigerant at constant -2.5°C, air entering 0.5°C, leaving -0.5°C: $$LMTD = \frac{(0.5-(-2.5)) - (-0.5-(-2.5))}{\ln\frac{0.5-(-2.5)}{-0.5-(-2.5)}} = \frac{3.0 - 2.0}{\ln(1.5)} = 2.46°C$$

Required coil area: $$A_{coil} = \frac{15,600}{25 \times 2.46} = 254 \text{ m}^2$$

Coil Configuration: 6-8 rows deep, 2.5-3.0 mm fin spacing, aluminum fins on copper tubes

Defrost Strategy:

Low coil temperature (-2.5°C) combined with high humidity promotes frost accumulation.

Expected frost accumulation rate: $$\dot{m}{frost} = \frac{Q{latent}}{h_{fg,ice}} = \frac{1,120}{334} = 3.35 \text{ kg/h} = 80 \text{ kg/day}$$

Defrost Frequency: Every 8-12 hours Defrost Method: Hot gas defrost (minimize temperature disruption) Defrost Duration: 20-30 minutes Drain Pan Heating: Required to prevent ice buildup

Refrigerant Selection

Recommended Refrigerants:

System Selection Criteria:

• Small facilities (<50 kW): R-448A or R-449A with DX expansion
• Medium facilities (50-200 kW): R-448A/R-449A with liquid overfeed or NH₃
• Large facilities (>200 kW): NH₃ or CO₂ cascade systems

Compressor Sizing

For R-448A at evaporating temperature -2.5°C, condensing temperature 35°C:

From refrigerant tables:

• h₁ (evaporator outlet, saturated vapor) = 405 kJ/kg
• h₂ (compressor discharge, isentropic) = 435 kJ/kg
• h₃ (condenser outlet, saturated liquid) = 249 kJ/kg
• h₄ (evaporator inlet, after expansion) = 249 kJ/kg

Refrigeration effect: $q_e = h_1 - h_4 = 405 - 249 = 156$ kJ/kg

Compressor work: $w_c = h_2 - h_1 = 435 - 405 = 30$ kJ/kg

COP: $\frac{q_e}{w_c} = \frac{156}{30} = 5.2$

Mass flow rate: $\dot{m} = \frac{Q_{evap}}{q_e} = \frac{15.6}{156} = 0.100$ kg/s = 360 kg/h

Compressor power (isentropic): $P_{comp} = \dot{m} \cdot w_c = 0.100 \times 30 = 3.0$ kW

Actual power (assuming 70% isentropic efficiency, 90% mechanical efficiency): $$P_{actual} = \frac{3.0}{0.70 \times 0.90} = 4.76 \text{ kW}$$

Select scroll or screw compressor with 5.5 kW motor for adequate reserve capacity.

Air Circulation Patterns

Proper air distribution prevents temperature stratification and ensures uniform cooling across the entire storage volume.

Air Velocity Requirements

Over Fruit: 0.25-0.50 m/s (50-100 fpm) Between Bins: 0.50-1.0 m/s (100-200 fpm) At Evaporator Face: 2.0-2.5 m/s (400-500 fpm)

Rationale: Higher velocities increase heat transfer but also accelerate moisture loss. Optimum balances cooling rate with humidity maintenance.

Temperature Uniformity

Target Variation: ±0.5°C throughout storage volume

Air Change Rate: $$ACR = \frac{Q_{air}}{V_{room}}$$

Required air flow for 15.6 kW cooling load, 1°C temperature rise: $$Q_{air} = \frac{Q_{cooling}}{\rho \cdot c_p \cdot \Delta T} = \frac{15,600}{1.29 \times 1.005 \times 1} = 12.0 \text{ m}^3/\text{s}$$

For 500 m³ room: $$ACR = \frac{12.0 \times 3600}{500} = 86.4 \text{ changes/hour}$$

Fan Power Requirement:

Assuming 150 Pa static pressure (typical for low-velocity distribution): $$P_{fan} = \frac{Q \cdot \Delta P}{\eta_{fan}} = \frac{12.0 \times 150}{0.65} = 2,769 \text{ W} = 2.77 \text{ kW}$$

Distribution System Design

Top Air Delivery Configuration:

Evaporator mounted at ceiling level, discharge air directed along ceiling, returns through floor-level intakes or through product mass.

Advantages:

• Natural temperature stratification assists air circulation
• Condensate drainage simplified
• Accessibility for maintenance

Disadvantages:

• Potential for short-circuiting if not baffled properly
• Upper storage layers receive coldest air

Bottom Air Delivery Configuration:

Evaporator at floor level or in plenum beneath slatted floor, upward air flow through product mass.

Advantages:

• More uniform temperature distribution
• Efficient use of floor space
• Reduced short-circuiting

Disadvantages:

• Condensate management challenges
• Higher static pressure requirements

Recommended: Top air delivery with vertical baffles to direct air down along walls, return through central aisle.

Bin Stacking Patterns

Pallet Configuration:

• Bin dimensions: 1.2 m × 1.0 m × 0.6 m (typical wooden bin)
• Fruit depth: 0.4-0.5 m (limit to reduce compression damage)
• Void space: 15-25% for air circulation
• Stack height: 3-4 bins maximum (without refrigerated air circulation through bins)

Air Flow Path:

Horizontal air flow requires minimum 100 mm gaps between bin stacks and walls.

Vertical air flow (if using perforated bins): Size perforations for 0.5 m/s upward velocity.

Perforation area: 10-15% of bin floor area

Pressure drop through 0.4 m depth of plums at 0.5 m/s superficial velocity: $$\Delta P = 150 \times d = 150 \times 0.4 = 60 \text{ Pa}$$

(Coefficient 150 Pa/m empirically determined for spherical fruit, moderate packing)

Pre-Cooling Requirements

Rapid removal of field heat before storage entry prevents condensation on fruit surfaces and reduces total refrigeration load.

Cooling Methods

Forced-Air Cooling:

Air drawn through stacked bins by pressure differential.

Cooling time estimation (half-cooling time): $$t_{1/2} = \frac{c_p \cdot \rho_{fruit} \cdot D}{2 \cdot h}$$

Where:

• c_p = specific heat of plums = 3.8 kJ/kg·K
• ρ_fruit = bulk density = 550 kg/m³
• D = characteristic dimension (fruit diameter) = 0.055 m
• h = surface heat transfer coefficient = 40-60 W/m²·K at 2 m/s air velocity

$$t_{1/2} = \frac{3,800 \times 550 \times 0.055}{2 \times 50} = 1,149 \text{ s} = 19.1 \text{ minutes}$$

Seven-eighths cooling time (99.2% of temperature difference removed): $$t_{7/8} = 3 \times t_{1/2} = 57 \text{ minutes}$$

Hydrocooling:

Immersion or spray cooling with near-freezing water (0.5-1°C).

Advantages:

• Very rapid cooling (10-15 minutes to near water temperature)
• Minimal weight loss
• Removes field dirt and debris

Disadvantages:

• Water disposal requirements
• Fruit wetting may promote decay if not properly dried
• Requires chlorination (50-100 ppm) to prevent cross-contamination

Heat transfer coefficient in water: 500-800 W/m²·K

Half-cooling time in water (h = 650 W/m²·K): $$t_{1/2} = \frac{3,800 \times 550 \times 0.055}{2 \times 650} = 88 \text{ s} = 1.5 \text{ minutes}$$

Room Cooling:

Slowest method, acceptable only for small volumes or non-perishable varieties.

Natural convection heat transfer coefficient: 5-10 W/m²·K

Half-cooling time: $$t_{1/2} = \frac{3,800 \times 550 \times 0.055}{2 \times 7.5} = 9,393 \text{ s} = 2.6 \text{ hours}$$

Seven-eighths cooling time: 7.8 hours (unacceptably slow)

Pre-Cooling System Capacity

For 10,000 kg daily throughput, cooling from 20°C to 2°C in 1 hour:

$$Q_{precool} = \frac{m \cdot c_p \cdot \Delta T}{t} = \frac{10,000 \times 3.8 \times 18}{3600} = 190 \text{ kW}$$

Add respiration heat during cooling (average 0.030 W/kg at 10°C): $$Q_{resp} = 10,000 \times 0.030 = 300 \text{ W} = 0.3 \text{ kW}$$

Total pre-cooling load: 190.3 kW

With 20% safety margin: Design capacity = 228 kW (65 tons)

Pre-cooling systems typically operate intermittently, sized for peak harvest periods.

Quality Monitoring Protocols

Systematic quality assessment ensures timely intervention before unmarketable deterioration occurs.

Temperature Monitoring

Sensor Placement:

• Warmest location (typically near door, upper level): Critical control point
• Product center: Representative of average conditions
• Evaporator return air: System performance indicator
• Multiple depths within bins: Thermal lag assessment

Sensor Specifications:

• Type: Platinum RTD (Pt100 or Pt1000)
• Accuracy: ±0.1°C
• Resolution: 0.01°C
• Response time: <30 seconds in air
• Calibration frequency: Annually against NIST-traceable standard

Data Logging:

• Sampling interval: 5-15 minutes
• Alarm setpoints: ±1°C from setpoint
• Historical trending: Identify patterns and system degradation

Humidity Monitoring

Sensor Type: Capacitive RH sensor with Pt1000 temperature sensor

Specifications:

• Range: 0-100% RH
• Accuracy: ±2% RH (10-90% range)
• Temperature compensation: Integrated
• Drift: <1% per year

Placement: Return air stream, away from direct evaporator discharge

Firmness Assessment

Penetrometer Testing:

• Probe diameter: 8 mm (5/16 inch)
• Penetration depth: 8 mm
• Measurement location: Equatorial region, two opposite sides
• Sample size: Minimum 20 fruits per lot
• Frequency: Weekly during storage

Acceptance Criteria:

• Initial firmness: 55-70 N
• Minimum marketable: 25-30 N
• Reject threshold: <20 N

Visual Inspection

Inspection Protocol:

• Frequency: Weekly for first month, bi-weekly thereafter
• Sample size: 1% of lot, minimum 50 fruits
• Assessment parameters:
  • Surface defects (scuffs, bruises, decay)
  • Chilling injury symptoms (pitting, browning)
  • Shriveling (moisture loss >5%)
  • Decay incidence

Documentation: Photographic records of representative samples, defect incidence rates, trend analysis.

Respiration Rate Measurement

Respiration monitoring indicates physiological status and predicts remaining storage life.

Measurement Method: Sealed chamber CO₂ accumulation

Sample 5-10 kg fruit in sealed container, measure CO₂ concentration change over 2-4 hours.

$$RR = \frac{\Delta CO_2 \cdot V_{chamber}}{m_{fruit} \cdot t}$$

Where:

• RR = respiration rate (mg CO₂/kg·h)
• ΔCO₂ = CO₂ concentration change (mg/L)
• V_chamber = chamber volume (L)
• m_fruit = fruit mass (kg)
• t = measurement duration (h)

Normal Values at 0°C: 2-5 mg CO₂/kg·h

Elevated Respiration (>8 mg CO₂/kg·h): Indicates:

• Chilling injury progression
• Pathogen infection
• Over-maturity at harvest
• Excessive mechanical damage

Action: Prioritize affected lots for immediate marketing or processing.

System Integration and Control

Automated control systems optimize energy consumption while maintaining critical environmental parameters.

Control Strategy

Temperature Control:

• Primary: Modulating refrigerant flow via electronic expansion valve (EEV)
• Secondary: Variable-speed compressor or hot gas bypass for capacity modulation
• Tertiary: Evaporator fan cycling (use cautiously to avoid stratification)

Humidity Control:

• Ultrasonic humidifier with on/off or modulating control
• Setpoint: 92% RH (midpoint of 90-95% range)
• Deadband: ±1% RH to prevent excessive cycling

Defrost Control:

• Time-initiated, temperature-terminated
• Initiation: Every 8-12 hours based on frost accumulation monitoring
• Termination: Coil temperature reaches +8 to +10°C
• Post-defrost fan delay: 2-5 minutes (allow condensate drainage, prevent warm air discharge)

Energy Optimization

Night Setback: Not recommended for plum storage due to narrow acceptable temperature range and chilling injury risk.

Variable Capacity Operation:

Compressor energy at partial load (variable speed drive, 60% capacity): $$P_{60%} = 0.60^{0.7} \times P_{100%} = 0.68 \times P_{100%}$$

Energy savings compared to on/off cycling: 15-25%

Evaporator Fan Control:

Continuous operation preferred for humidity maintenance and temperature uniformity.

If cycling is necessary (during very light load periods):

• Minimum on-time: 10 minutes per hour
• Maximum off-time: 20 minutes
• Monitor temperature deviation; resume continuous operation if exceeds ±0.3°C

Heat Recovery:

Desuperheater or hot gas condenser can provide:

• Domestic hot water
• Floor heating (loading dock, processing areas)
• Pre-heating ventilation air

Available heat from desuperheater (15-20% of total heat rejection): $$Q_{desup} = 0.18 \times (Q_{evap} + P_{comp}) = 0.18 \times (15.6 + 4.8) = 3.67 \text{ kW}$$

Troubleshooting Common Issues

References and Standards

ASHRAE Standards:

• ASHRAE Handbook - Refrigeration, Chapter 37: Deciduous Tree and Vine Fruit
• ASHRAE Standard 15: Safety Standard for Refrigeration Systems

Industry Guidelines:

• USDA Agricultural Handbook 66: The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks
• University of California Postharvest Technology Center: Stone Fruit Recommendations

Psychrometric Calculations:

• ASHRAE Fundamentals, Chapter 1: Psychrometrics

System Design:

• ASHRAE Handbook - Refrigeration, Chapter 13: Refrigerant System Chemistry
• ASHRAE Handbook - Refrigeration, Chapter 2: Refrigeration Load Calculations