Operation modes and structure of heat-circulation heat pump drying unit

Abstract

The invention discloses operation modes and a structure of a heat-circulation heat pump drying unit. The structure is characterized in that the drying unit comprises a heat recovery air duct which forms a sealed air flow circulation loop with the inner cavity of the drying oven, an evaporator is installed in the air duct, and an air regulator for regulating and controlling the air flowing through the evaporator is arranged in the unit. The operation modes are a heating mode and a heat-circulation dehumidification mode. In the early operation stage of the unit, the heating mode is started, the heat pump system absorbs heat from the atmosphere, so that the air in the drying oven is heated to achieve the preset temperature; and then, the unit operates the heat-circulation dehumidification mode, the high-temperature high-humidity gas in the drying oven flows through the evaporator in the air duct to be cooled and dehumidified and then flows back to the drying oven, the sensible heat and latent heat absorbed by the evaporator are released into the drying oven by a condenser, and the air regulator enables the ratio of the condensation air quantity to evaporation air quantity to be greater than 2 and controls the inlet / outlet air temperature difference of the evaporator to be 10-25 DEG C. The unit has the advantages of high average COP and high latent heat ratio in the heat absorbed by the evaporator; and the dehydrating amount per kilowatt-hour is 5 kilograms or above, so that the efficiency is enhanced by 70-130% as compared with the conventional heat pump drying.

Description

technical field [0001] The invention discloses the operation mode and structure of a heat circulation heat pump drying device. The scope of application is: high and medium temperature heat pump drying and dehumidification. The range of drying and drying items is grain, vegetables and fruits, tobacco leaves, bacon, aquatic products, clothing fabrics, Chinese medicinal materials, wood, peat, various industrial and agricultural raw materials and products, etc. Background technique [0002] The types of material drying are extremely wide and the quantity is huge, and the energy consumption of the whole society for material drying is very huge. According to some data, the energy consumption for drying and drying materials in developed countries accounts for between 7% and 15% of the total energy consumption, with an average of 12%. Now China's annual power generation is about 5 trillion kWh. If the electricity consumption for drying is estimated to be 8% of the total power gene...

AI Technical Summary

Problems solved by technology

The disadvantage is that the temperature of the air in the oven rises very slowly, and the heat obtained by the inner cavity of the oven is only the heat converted by the energy consumed by the heat pump device. The gas temperature of the evaporator is low, the ratio of latent heat / sensible heat in the heat absorbed by the evaporator is very low, the drying and dehumidification effect is poor, and the drying speed is slow

Especially because the condenser and the evaporator share a fan, when the condensing air volume is the same as the evaporating air volume, if the latent heat absorbed by the evaporator is greater than the sensible heat, the temperature difference between the inlet and outlet air of the condenser is more than 2.5 times the temperature difference between the inlet and outlet air of the evaporator, making the condenser If the air outlet temperature of the condenser is too high, the condensation temperature of the refrigerant is too high, resulting in a decrease in the energy efficiency ratio of the heat pump system; if the latent heat absorbed by the evaporator is less than the sensible heat, although the disadvantage of too high air outlet temperature of the condenser can be avoided, the latent heat / sensible heat is less than 1, Reduce the conversion rate between latent heat and sensible heat of the air in the oven, resulting in poor dehydration effect

The overall effect is equivalent to that of Class A open devices: Class B closed heat pump drying devices can save energy by more than 50% compared with electric heating drying, and the SMER is about 2 to 2.5, and it is difficult to exceed 3, especially in winter. When the temperature is very low, the drying effect is worse

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