Peeping into the Cold Storage

Refrigeration is the process of removing heat from a space or substance to lower its temperature, enabling the preservation of perishable goods, maintaining comfortable environments, and supporting industrial processes. Cold storage refers to specialized facilities that use refrigeration to store goods (e.g., food, pharmaceuticals) at controlled low temperatures. These technologies are vital in industries like hospitality, retail, healthcare, and agriculture, particularly in hot climates like Delhi-NCR, where maintaining low temperatures is challenging.

Principles of Refrigeration

Refrigeration works by transferring heat from a low-temperature area to a high-temperature area
using a refrigeration cycle. The key components and principles are:

Refrigeration Cycle

The most common refrigeration method is the
vapour-compression cycle, used in 90% of commercial systems (e.g., VRV, cold storage units). It involves four main components:

• Compressor: Compresses refrigerant gas (e.g., R134a, R410A), raising its pressure and temperature.
• Condenser: Releases heat from the hot, high-pressure gas to the environment (e.g., 40°C ambient in Delhi), condensing it into a liquid.
• Expansion Valve: Reduces the liquid refrigerant’s pressure, lowering its temperature.
• Evaporator: Absorbs heat from the cold storage space (e.g., 0°C), evaporating the refrigerant back into a gas, cooling the space.

Example: In a cold storage room at 0°C, the evaporator absorbs heat (20-30 kW for a 10 TR system), cooling the air, while the condenser rejects heat (25-35 kW) outside at 40°C.

Refrigerants

Refrigerants are the working fluids in the cycle, absorbing and releasing heat. Common refrigerants include:

• R134a, R410A: Used in commercial cold storage.
• Ammonia (NH3): Preferred in industrial cold storage (e.g., food warehouses) for efficiency but toxic, requiring safety measures.
• CO₂ (R744): Eco-friendly, gaining popularity for Delhi’s green building trends (e.g., IGBC for Bhutani).

Types of Refrigeration Systems

Refrigeration systems vary based on application, scale, and temperature requirements. Here are the main types relevant to cold storage:

Vapour-Compression Systems

• Description: Most common, as described above. Used in small (e.g., hotel freezers) to large-scale cold storage (e.g., warehouses).
• Temperature Range: -40°C to 5°C (e.g., -18°C for frozen foods, 0-5°C for fresh produce).
• Capacity: 1 TR to 100 TR (e.g., 10 TR for a 500 m³ cold room).
• Applications: Hotel kitchens, retail, and food warehouses.

Absorption Refrigeration

• Description: Uses heat (e.g., gas, waste heat) instead of a compressor to drive the cycle, with ammonia-water or lithium bromide-water as the working pair.
• Temperature Range: 0-10°C, less suited for deep freezing.
• Applications: Industrial setups with waste heat.
• Efficiency: Lower COP (0.5-1) vs. vapour-compression (3-4), but reduces electricity costs.

Cascade Systems

• Description: Uses two refrigeration cycles (e.g., R404A for high stage, CO₂ for low stage) to achieve ultra-low temperatures.
• Temperature Range: -40°C to -80°C (e.g., for vaccine storage).
• Applications: Pharmaceuticals.

Evaporative Cooling (for Pre-Cooling)

• Description: Not true refrigeration but cools air using water evaporation, often paired with cold storage for pre-cooling fresh produce.
• Temperature Range: 10-20°C, limited by Delhi’s humidity (60-80% RH).
• Applications: Pre-cooling vegetables before cold storage.

Cold Storage Design

Cold storage facilities require careful design to maintain temperature, humidity, and energy efficiency. Key aspects include:

Insulation

• Materials: Polyurethane Foam (PUF) sandwich panels.
• Purpose: Prevents heat gain (e.g., ~500-1,000 BTU/h for a 500 m³ room without insulation), maintaining 0°C inside at 40°C outside.

Refrigeration Equipment

• Evaporators: Ceiling-mounted, with defrost systems (e.g., hot gas, electric) for -18°C rooms to prevent ice build-up.
• Condensers: Air-cooled or water-cooled (e.g., for large warehouses). Air-cooled units struggle at 45°C, reducing efficiency.

Temperature and Humidity Control

• Temperature: 0-5°C for fresh produce, -18°C for frozen goods, -40°C for specialized storage (e.g., seafood).
• Humidity: 85-95% RH for fresh produce, 50-60% for frozen goods to prevent frost.
• Control Systems: BMS or standalone controllers to monitor and adjust conditions.

Structural Design

• Flooring: Insulated concrete with vapour barriers to prevent ground heat gain.
• Doors: Insulated sliding doors with air curtains to minimize air leakage.
• Airtight Seals: Silicone gaskets to prevent humid air ingress.

Sizing and Capacity

• Volume: A 500 m³ cold room stores ~50-100 tons of produce (e.g., vegetables at 0°C).
• Cooling Load: ~10-20 TR for 500 m³, depending on product (e.g., potatoes at 0°C, ~0.02 TR/ton).

Applications of Refrigeration and Cold Storage

Cold storage is essential across industries, with direct relevance to your projects:

Hospitality

• Application: Walk-in freezers/refrigerators for kitchens (e.g., 0-5°C for vegetables, -18°C for meat).
• Capacity: 2-5 TR for a 50 m³ room, serving 500 guests.

Retail

• Application: Cold rooms for perishables (e.g., dairy, fruits) in mall supermarkets, 0-5°C.
• Capacity: 10-20 TR for 200-500 m³, serving daily sales.
• Green Trend: CO₂ systems meet IGBC standards, though costlier.

Food Supply Chain

• Application: Large warehouses (e.g., 5,000 m³) for fruits, vegetables, and frozen goods in NCR.
• Capacity: 50-100 TR, storing 500-1,000 tons.

Pharmaceuticals

• Application: Vaccine storage (2-8°C) or deep-freeze (-40°C) for biologics.
• Capacity: 1-10 TR for 50-200 m³

Challenges in Refrigeration and Cold Storage

Energy Efficiency

• Issue: High energy use (~50-100 kW for 20 TR, ~`5-10 lakh/year at `8-10/kWh).
• Solution: Use high-efficiency compressors, saving ~10-15%. Add VFDs for load modulation.

Condensation and Humidity

• Issue: Delhi’s 70-80% RH causes condensation if insulation is poor (R <2.5).
• Solution: Use 100 mm PUF (R 5), nitrile insulation on pipes (10 mm, R ~0.29) and dehumidifiers, per your fixes.

Refrigerant Regulations

• Issue: HFC phase-down (e.g., R410A, GWP 2088) under India’s Kigali Amendment commitments (post-2025).
• Solution: Transition to low-GWP refrigerants (e.g., R32, CO₂), though CO₂ systems cost more. Plan for retrofits.

Maintenance and Downtime

• Issue: Compressor failures or coil frosting disrupt operations, critical for hotels/malls.
• Solution: Regular AMC, checking refrigerant levels, and stocking spares.

Initial Costs and Budget

• Issue: High setup costs strain small businesses.
• Solution: Start with smaller units.

Aman Taluja is a dedicated professional in the HVAC industry. He is currently involved in operations at Brightflow Engineers Pvt. Ltd. Based in Kundli, Haryana, the company specializes in manufacturing Air Handling Units, Evaporative Cooling Units, Dry Scrubbers, and Fan Coil Units. With a proven track record, Aman has successfully contributed to various prestigious projects, including installations at NTPC Dadri, Deloitte Gurugram, Le Meridien Hyderabad, Marriott Amritsar, and Ambience Creacions Gurgaon. His expertise in delivering high-quality air management solutions underscores his commitment to enhancing indoor air quality and operational efficiency.