Preheating time control of heat pump drying process for bamboo shoot dryer

- May 03, 2019 -

Preheating time control of heat pump drying process of bamboo shoot dryer is discussed. Taking bamboo shoot drying as an example, the pre-heating stage is about two hours, and the preheating temperature is set to 45 C. After the pre-heating stage, the temperature will gradually rise to about 60 C. If the preheating stage temperature is too high, the bamboo shoot will burst pulp. There are also some materials that need to be heated rapidly in the early stage. The temperature in the preheating stage is also very high, and the drying room is in a high humidity state. Preheating is the first step for most materials before drying, because the temperature requirement of heat pump drying is higher than the ambient temperature, especially in the low temperature or northern area, preheating is more important. In the preheating stage, because the initial temperature of the drying room is lower and the moisture evaporation of the material is less, the humidity is relatively low. Generally, only heating does not drain the humidity, so as to ensure that the material rapidly warms up and reaches the temperature balance inside and outside the material. The higher the air humidity, the higher the enthalpy value and the better the thermal conductivity effect.

Preheating time needs to be determined according to material properties, material quantity and environmental temperature, usually two to three hours, preheating temperature can not be too high, preferably slightly lower than the material drying temperature requirements, if the temperature is too high, it may lead to changes in the appearance and color of materials and loss of nutrients, such as fragmentation, blackening and so on.

This article is from the microwave drying equipment

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