I. Immediate Effects: Continuous Decline in Heat Exchange Efficiency (First Symptom)

Water has a much higher thermal conductivity than insulation material. In damp areas, the insulation layer loses its thermal insulation capability, causing significant heat loss from the heat pump’s heating side and the outer wall of the evaporator.

The heat pump must continuously increase its power output to compensate for the heat loss. As a result, evaporation capacity decreases while energy consumption per unit of water produced increases, even with the same feed volume.

The area of low-temperature condensation on the outer wall expands, and water vapor continuously carries away heat, creating a vicious cycle: “moisture penetration into insulation → accelerated heat leakage → more severe condensation on the outer wall → increased water absorption.”

If the insulation layer covers the low-temperature sections of the condenser or heat exchanger cylinder, moisture penetration causes cold energy to escape from the cylinder’s exterior. This results in incomplete condensation of secondary steam, an increase in non-condensable gases in the system, and vacuum fluctuations, further reducing evaporation efficiency.

II. Medium- to Long-Term Irreversible Damage: Corrosion of Equipment Casing and Base Materials (Hidden and More Destructive)

Water trapped in the insulation cavity is sealed off and cannot dry naturally. In a long-term damp, oxygen-deprived environment, closed-circuit corrosion cells form on the steel cylinder and the outer walls of the carbon steel casing, causing corrosion at a rate several times faster than that caused by rain exposure in open air.

Water carries chlorine ions from the air, as well as alkaline and acidic leachates from the insulation material. Continuous immersion of the metal outer walls leads to initial pitting and rust spots, which gradually develop into rust pits and reduced wall thickness.

Long-term condensation inside the metal shell of the insulation layer causes the metal to corrode from the inside out. While no external damage is visible, the interior has long since perforated, resulting in leaks of water and vacuum.

Water tends to accumulate and seep into the welds and flange corners of PTFE-lined or stainless steel cylinders, leading to progressive crevice corrosion. In severe cases, this results in weld leaks and delamination of the lining.

III. Distinguishing Primary and Secondary Issues

Operational Performance: Moisture in the insulation is the first and most obvious factor to impair heat exchange efficiency; insufficient evaporation and increased energy consumption are immediately apparent upon startup.

Equipment Lifespan: If accumulated water is not removed, it will continue to corrode the shell, causing permanent structural damage; subsequent repair costs will far exceed the losses from reduced heat exchange efficiency;

Cascading Effects: Reduced heat exchange efficiency forces the unit to operate at high loads for extended periods, causing continuous overloading of the compressor and circulation pumps, which accelerates the aging of the entire unit’s components.