Elimination of Condensation

Jens Michael Würtz

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Condensation in chillers is a challenge

Elimination of Condensation

The modern methodology for chilling of pig carcasses was developed by DMRI more than 30 years ago. The aim is to remove heat from the carcass as quickly and gently as possible.
Since then, we have - through research - improved the process to the standards we have today, thus ensuring a minimal weight loss, improved quality and improved shelf life.

Prevent the occurrence of condensation
A part of designing the optimal process is to prevent the occurrence of condensation. In that matter we have quite extensive knowledge of the issue of condensation in older processing facilities. We have taken part in several projects with the aim of rectifying the problem by replacing existing air handling units and/or evaporators with units combining cooling and heating, thus changing the partial pressure of the water vapor in the moist air leaving the air handling unit.

Air sock system with benefits
Our experience, in cases with only minor condensation problems, is that problems can be solved by placing or replacing air sock systems with a type of incorporating nozzles in strategic places to allow the problem area to be swept with a steady flow of air.
At a recent audit in a slaughterhouse in North America we managed to design an assisting sock chilling system to the existing air handling units in the batch chillers for carcasses. This system will, besides the more evenly distributed air, ensure that the dew point temperature of the moist air can be designed slightly lower than the temperature of the surrounding surfaces. The moist air will then mainly deposit the moisture in the air handling unit.

The benefits are:

  • Better and more even chilling of products
  • Less condensation forming (savings in manpower)
  • Chill loss level may be decreased

We usually describe the problem as follows
When unsaturated, saturated or supersaturated air interact with a surface, the surface temperature determines the amount of condensation. During cleaning or during the initial chilling process of hot carcasses, the air is usually supersaturated and warmer than the room's boundary surfaces, hence it will be depositing a great deal of condensation on the colder surfaces.
The degree of supersaturation is determined by the air temperature in the room when the hot water cleaning starts, or when hot carcasses enter a carcass cooler.
The visible condensation quantity, which is seen as droplets, is determined by the surface temperatures, material porosity and volume of the room, as well as emerging from any splashes.

Drying air
Air is used to dry out or keep the moisture level low. The air's capacity to absorb moisture depends on the water vapor pressure in the air and the dry bulb temperature. If the water vapor pressure in the drying air is below the saturation pressure when sweeping and leaving a wet surface the surface will dry up. This may be accomplished in several ways: by increasing the temperature of the surfaces, or by keeping the surface temperature above the dew point temperature by forced ventilation with heated air, or by supplying air with a lower water vapor pressure during the drying period.

Uniquely designed solutions
We can design a process to avoid critical condensation issues, which combines the possible and relevant drying techniques from an economic point of view. The process is usually from one slaughterhouse to another and includes analyses of the moisture load, procedures, schedules, the configuration of the current air system and possible options for the use of heated ambient air and forced ventilation.