The Cold Chain 35 Choosing the best option
When specifying these systems it is important to strike a balance that provides the best value for that particular application. For example, the dehumidification process without heat recovery will deliver significant improvements in energy efficiency simply by preventing icing of the coils. The additional investment in heat recovery will certainly improve the overall energy efficiency of the system but may also extend the payback period. In either case, the selection of the humidifier will have an influence on overall life-cycle costs. For instance, it is important that the desiccant rotors use a high-performance desiccant that does not change behaviour in the low humidity conditions.
Synthesised silica gel has proved to be a chemically and thermally stable material that does not deliquesce like some other desiccant materials. This means that its performance over time is constant, while its chemical resistance means that it can be washed with water, making for a low maintenance solution.
For these reasons it makes sense to engage with specialists that are able to offer all options without being tied in to a particular manufacturer when considering options in the context of performance, lifecycle management and return on investment.
When high moisture levels are best
THERE ARE OCCASIONS where it is desirable to increase the humidity in a cold store by using a humidification system to maintain the right conditions for the products being stored. For example, J&A Growers is one of the UK’s leading wholesale growers of mostly native species of seedlings, trees and hedging for a wide range of purposes – including forest, hedgerow & roadside planting and landscaping. Here, a temperature of 2°C with a relative humidity of around 95% is necessary to keep the plants dormant after they have been harvested in the winter.
This helps to extend the planting season and ensures that plants arrive on the planting site in optimal condition. As the refrigeration process dries the air, humidification is essential to avoid desiccating the dormant plants. However, it is equally important to avoid condensation in these low-temperature conditions, as this can lead to fungal attacks.
This is achieved with a high-pressure adiabatic humidification system supplied by Humidity Solutions. The system maintains very close control of humidity, while using high
efficiency atomisers to ensure a short evaporative distance, thereby avoiding condensation.
A further benefit is that the adiabatic cooling effect of the system when the water evaporates helps to reduce the energy consumption of the refrigeration plant by providing 0.6kW of cooling per litre of water atomised.
Frimatec
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ACR News May 2015
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