The following article by Simon Khaled P.Eng., Director of Sales, North America for FabricAir looks at the formation of frost on the evaporator surface.
Left: Arrows show how warm air leaves the air cooling unit when the system is in the defrost cycle; Right: Fabric duct covers the unit when the system is in the defrost cycle preventing heat from escaping the unit. Supplied by FabricAir
In the carefully controlled environment of a cold storage facility, the formation of frost on the evaporator surface is a common occurrence. Frost can impede the conduction and distribution of cooling capacity, ultimately affecting the efficiency of the entire refrigeration system. Addressing this challenge is crucial, not only for operational effectiveness but also for substantial energy savings. According to the Energy Trust of Oregon, electric defrost can account for 21% of the energy usage in a cold storage facility.
Improper management of frost in a cold storage facility can lead to the formation of thick layers, impacting system efficiency. Effective defrosting becomes paramount for several reasons:
- Improving cooling system efficiency
- Reducing energy usage through fewer defrost cycles
- Ensuring product quality with a low temperature gradient
- Extending the life of cold storage system components by minimising wear and tear
A significant challenge faced by these facilities is the escape of heat from air coolers, resulting in substantial energy waste. Inefficient defrosting compounds the issue, increasing the frequency of defrost cycles and consequently, operational costs.
Heat saving, water repellant solutions
Efficient defrosting is not only an essential function but also a substantial contributor to energy usage in cold storage facilities. The market offers various solutions, with a focus on reducing defrosting time to enhance the efficiency of cold storage air coolers. Some solutions may involve intricate techniques or specialised tools, but those that prevent heat from escaping the air cooler prove most effective.
The integration of a short fabric duct can increase air throw and promotes air mixing to create a uniform temperature distribution within the space. This solution increases defrost cycle efficiency by reducing cycle frequency and minimising equipment impact. When the evaporator reaches the defrost cycle, the duct collapses, effectively sealing the unit and preventing heat from escaping. Water-repellant fabric prevents water droplets caused by the defrosting cycle from freezing on the fabric surface, further increasing the efficiency of a fabric-based solution.
Implementing solutions to increase cold storage efficiency can result in potential energy savings of up to 75% (contingent on equipment and operating conditions). The consequential reduction in defrosting time, ranging from 10% to 50%, results in heightened operational efficiency and diminished energy expenses.
Additionally, the use of fabric ducts not only limits heat loss but also improves air throw, fostering superior air mixing. This establishes a consistent and even temperature environment, ensuring the quality of stored goods.
Addressing frost-related challenges in cold storage facilities is not merely about resolving a surface issue but involves a strategic approach that significantly impacts energy consumption, operational costs and the overall longevity of the facility’s components.
Source
https://www.energytrust.org/wp-content/uploads/2016/12/ind_fs_guide_coldstorage.pdf
FabricAir.
