Category: Dehumidification

Ice formation on evaporator coils and floor surfaces is one of the most costly and persistent problems in cold storage operations — yet it’s almost entirely preventable with the right dehumidification strategy. This guide covers the moisture ingress cycle, the real cost of unmanaged frost, and how purpose-built dehumidification prevents it.

Why Ice Forms in Cold Storage Facilities

Every time a dock door opens in a cold store, a volume of warm, humid ambient air rushes into the refrigerated space. As this air cools to the chamber temperature, its ability to hold water vapour drops dramatically — and the excess moisture is deposited on every surface inside the facility. Over time, this accumulates on evaporator coils, structural racking, and floor surfaces as frost and ice.

The rate of moisture ingress depends on several factors: the temperature differential between ambient and storage conditions, the frequency and duration of door openings, and the ambient humidity at the time. In hot, humid Australian summers — particularly in coastal regions — the ingress rate can be two to three times higher than in cooler months.

A single large dock door opening in a 35°C, 80% RH Sydney summer day can introduce up to 2–3 litres of water vapour into the cold store — before any product movement has occurred.

The Operational Consequences

Ice build-up creates a cascade of problems that compound over time. Most facility operators are managing individual symptoms without addressing the underlying moisture cause:

• Evaporator coil icing: Frost on evaporator coils acts as an insulating layer, reducing heat transfer efficiency. Every millimetre of frost can raise the required refrigerant temperature by 3–5°C, significantly increasing energy consumption and compressor wear.
• Increased defrost cycles: To clear frost from coils, refrigeration systems run electric or hot-gas defrost cycles — during which the facility temperature rises, creating additional product risk.
• Floor and racking ice: Ice on warehouse floors creates a serious slip and forklift hazard, while icing on racking can compromise structural integrity over time.
• Product moisture exposure: Produce, nuts, grains, and pharmaceuticals exposed to moisture fluctuations are susceptible to mould, spoilage, and compliance failures.

The Dehumidification Solution

The correct approach to ice prevention is moisture removal before it enters the cold store — not after. A purpose-built desiccant dehumidifier positioned at or near the dock door area removes moisture from incoming ambient air, reducing the dew point of the air entering the refrigerated space and eliminating the condensation and frost cycle at source.

Unlike refrigerant dehumidifiers, desiccant units perform effectively at low temperatures — making them the preferred choice for cold store dock areas where ambient conditions are themselves often cold. They can be integrated into the facility’s building management system for automated operation, activating when dock doors open and ramping down during quieter periods.

What to Expect from a Well-Designed System

A correctly specified and installed desiccant dehumidification system in a cold storage facility will typically deliver a 60–80% reduction in evaporator defrost frequency, eliminate floor and racking ice formation in treated zones, and reduce overall refrigeration energy consumption by 15–25%.

The return on investment depends on the scale of the facility, the frequency of dock operations, and the ambient climate — but for most cold stores operating in coastal NSW, the payback period on a dehumidification system is typically 2–4 years.

Nut storage, grain processing, and fresh produce handling all require tightly controlled humidity environments to prevent spoilage, mould growth, and compliance failures. Humidity is the single most important variable in post-harvest storage quality.

The Spoilage Mechanism

Moulds and bacteria require moisture to grow. At relative humidity above 70%, most food storage environments become hospitable to spoilage organisms. For high-value products like macadamia nuts, almonds, and dried fruits, even brief exposure to high humidity can lead to aflatoxin contamination — a serious food safety issue.

Dehumidification Specifications

Most nut and dried fruit storage targets 50–60% RH at ambient temperatures. Achieving this consistently requires refrigerant-based or desiccant dehumidification, depending on the required dew point. Desiccant systems are preferred when storage temperatures are below 15°C, as conventional refrigerant dehumidifiers lose efficiency at low temperatures.

Controlling Moisture During Processing

The processing environment introduces additional moisture challenges — blanching, washing, and roasting all add humidity to the air. Each production zone requires individual humidity analysis and control strategy to maintain product quality through the entire value chain.