Views: 207 Author: Wendy Publish Time: 2023-04-23 Origin: Site
Through the working conditions of the control device, the temperature of the hot and dry air in the drying chamber is between 20 and 80 °C, which can meet the high quality drying requirements of most thermal materials. The closed cycle of the drying medium can also avoid the impurity contamination caused by the gas exchange with the outside world, which is especially important for food, medicine, or biological products. In addition, when the material is sensitive to the oxygen in the air (easy to oxidation, combustion, and explosion), the inert medium can also be used instead of air as a drying medium to achieve anaerobic drying.
The heat pump dryer in the heating air heat drying mainly from the recovery chamber wet air contained in show heat and latent heat, input energy only the heat pump compressor power consumption, heat pump and consume a small amount of work can produce a lot of heat, so heat pump drying device SMER (consumption of unit energy to remove the water component in the wet material) is usually 1.0–4.0 kg/kWh, and the traditional convection dryer SMER value is about 0.2–0.6 kg/kWh.
When the material has high requirements for the temperature and humidity of the air entering the drying room (such as wood, etc.), the evaporation temperature and condensation temperature of the working medium in the evaporator and condenser can be adjusted to meet the requirements of the material for its qualitative structure and appearance.
Some materials contain volatile components (such as fragrance and other volatile components), and using a heat pump dry, volatile components and moisture gasification into the air, containing volatile air after the evaporator is cooled, the volatile components is also liquefied, together with condensate, collect condensate containing volatile components, and appropriate volatile separation methods will be useful.
The drying medium in the heat pump drying device is closed, and there is no material dust, volatile substances, or odor with the dry exhaust gas. The waste heat in the drying chamber exhaust is directly recovered by the heat pump to heat the cold dry air, and there is no unit heat pollution to the environment.
The heat pump in the heat pump drying device also has a refrigeration function. It can use the refrigeration function to realize the low-temperature processing of various materials (such as quick-freezing or refrigeration) or preservation in the season with fewer drying tasks, and also expand the heating function of the heat pump for heating in the planting (such as a greenhouse) or breeding site in the cold season.
The materials suitable for drying are mainly a large class of materials with a tolerance temperature between 20 and 80 °C in the drying process, or although the materials can withstand a high temperature, use a heat pump to dry more energy-saving or safe materials. More materials have been studied and applied, such as wood (such as oak), grains, seeds, edible fungi (such as mushrooms, fungus), medicinal materials (such as ginseng, etc.), seafood (such as fresh oysters, scallops, etc.), bioactive products (such as cells, enzymes), tea, paper, and so on.
Compared with other low-temperature (air temperature into the drying room 40 °C) drying devices (such as microwave drying, vacuum drying, and freeze drying), the heat pump dryer device has obvious economic advantages due to the small initial investment of the equipment and the low operation cost. The equipment cost of the heat pump drying device is mainly the heat pump part and the drying room part, in which the drying room part is the same as the ordinary convection drying room without special air tightness and pressure bearing requirements.
Compared with ordinary drying devices (into the drying room air temperature> 40 °C), the heat pump dryer's initial investment is generally higher than that of an electric heating device, a gas furnace, or a coal-fired hot air furnace. The initial investment of a drying device is generally higher than that of an ordinary drying device.