Vacuum cooler & Hydro-vacuum cooler brief introduce（part A）
Vacuum cooling involves reducing the pressure inside a sealed chamber. The water inside the vegetables turns into steam, absorbing thermal energy. Vacuum refrigeration works best for products that lose water easily, such as lettuce and baby leaf crops.
Hydraulic vacuum coolers add a fogging system to prevent moisture loss from the product. At the same time, hydraulic cooling can help cool down more quickly and make some compact vegetables suitable for the vacuum cooling process.
Vacuum cooling is a fast and efficient method of energy saving.
What is vacuum cooling? (In detail)
Vacuum cooling removes heat from vegetables by boiling some of the water they contain.
The product is loaded in a sealed strong vacuum chamber and the air is pumped. This reduces the normal air pressure to a virtual vacuum (<1KPa). Under these conditions, the water boils at <7 ° C.
As the water in the vegetables changes from liquid to gas, it absorbs the thermal energy of the product and cools it. This steam is removed by passing it through the cooling coils, which condenses it again in liquid water.
For vacuum cooling to cool vegetables quickly, they should be able to lose moisture easily. For this reason, vacuum cooling is very suitable for leaf products, such as lettuce, Asian vegetables and freshly cut flowers. Products such as broccoli, celery and sweet corn can also be cooled effectively with this method. Vacuum cooling is not suitable for products with waxy skins or with a low surface / volume ratio, e.g. Eg Carrots, potatoes, tomatoes or zucchini.
For every 5 ° C reduction in temperature, approximately 1% of the weight of the product must be converted to water vapor. However, modern water vacuum chillers address this problem by spraying water on the product during the vacuum process. This can reduce the loss of moisture to negligible levels.