1. What is heat pump drying?

Answer: The heat pump dryer is a device that uses electricity to drive the fan to absorb the heat in the air and drive the compressor to do work to achieve heating and drying with four times the power consumption of one kilowatt-hour of electricity. It is an extended product of air energy heat pump.

The heat pump drying system is a device that uses a heat pump to provide a heat source to heat materials with high moisture content, thereby increasing the temperature and dryness of the air, and achieving material drying (drying). The air-energy high-temperature heat pump drying unit uses the reverse Carnot principle to absorb heat from the surrounding environment and transfer it to the object to be heated (the object with a higher temperature).

2. What are the components of the heat pump drying system?

The heat pump drying system includes the heat pump main engine, the circulating fan in the drying room, the air duct and the uniform air plate, the material rack and the tray.

A. The heat pump host is the core part of the main equipment of the entire system. It provides heat source and dehumidification functions for the system. Its working principle is the same as that of the heat pump host in the field of hot water heating.

B. Material racks and material trays are devices that carry materials.

C. The internal circulation fan ensures the air flow in the drying room to ensure that the water vapor generated during the drying process of the material can be taken away in time. If the moisture is not discharged in time, it may cause the material to become moldy or deteriorate. The common built-in high temperature and high humidity axial flow fan , External long-axis axial fans, centrifugal fans (can be installed outside), etc., currently the most used is the built-in high-temperature and high-humidity axial fan, which is placed indoors for the appearance of the entire system.

D. Electric auxiliary heating, which is mainly used for emergency response when the temperature rises quickly and the equipment temporarily fails, as a backup. Some materials require high temperature in a short time, or when the energy efficiency ratio of the heat pump is reduced in low temperature weather, electric heating is required. During the drying process, the temperature requirements of the materials in different stages are different. Some stages require high temperature, and there are two ways to increase the temperature. One is to increase the configuration of the heat pump host, and the other is an auxiliary heat source. Electric heating is used.

E. The main purpose of the design of the air duct and the uniform air plate is to ensure the uniformity of the air flow in the drying room, and the temperature and humidity differentiation of each area in the drying room reach the minimum, thereby improving the uniformity and quality of the material drying And drying efficiency.

F. The storage body of the drying room ensures that the entire system runs in a confined space and provides space for material placement.

3. What are the types of heat pump drying?

Heat pump drying equipment can be divided into high-efficiency dehumidification heat pump dryers, high-temperature air energy split dryers, and high-temperature air energy integrated drying and dehumidification integrated machines according to different heat sources and moisture removal methods.

The principle of the high-efficiency dehumidification heat pump dryer is to use the phase change of water to absorb and release heat energy to realize the recycling and utilization of heat energy in the enclosed space during the process of removing the moisture of the material. Its advantages are after the moisture of the material is removed, The dry air is left behind, and the water vapor is discharged through the condensed water. The whole drying process does not need to exchange heat with the outside air, so it is basically not affected by the ambient temperature, especially in the autumn and winter seasons where the use environment is very low (below 0°C) And there is an advantage in drying materials with lower temperature drying requirements (the temperature in the drying room is lower than the ambient temperature).

The split high temperature air energy heat pump drying system uses a small amount of electric energy to drive the equipment to transport the heat energy in the air to the drying room to heat the material to heat the material and evaporate the water in the material into water vapor. The exclusion is to use a strong row type. The split high-temperature air-energy heat pump drying system simply replaces the original heat source equipment to achieve partial energy-saving effects. The investment cost is low. It is suitable for customers with high ambient temperature, low investment capacity and low requirements. Because the entire dehumidification is completed by forced exhaust, the system has a forced exhaust window and a fresh air window. The exhausted high temperature and high humidity air and the supplied low-temperature air from the outside have a large heat loss and are not suitable for long-term dehumidification. It is suitable for materials with low humidity and slow water output. The energy consumption is very high in winter, and the energy efficiency ratio is between 1.0 and 2.0.

The integrated air energy heat pump drying and dehumidification integrated machine is an improved version on the basis of the split high temperature heat pump dryer. It is simpler to install, and the air energy heat pump product. The fresh air is first mixed with the high temperature water discharged before entering the drying room. The steam exchanges heat to increase the base temperature of the fresh air. The temperature of the waste heat has dropped after the heat exchange of the fresh air. The cooled hot air has to undergo two heat recovery by the regenerator and the evaporator before being discharged at the end. The air temperature is already very low, and the heat recovery can achieve more than 70%.

4. What are the advantages of heat pump drying?

Answer: The advantages of heat pump dryers compared to other types of dryers:

High efficiency and energy saving, low operating cost. The operating cost of heat pump drying is only 30% of electric heating dryers, 40% of fuel dryers, and 60% of coal-fired dryers. In addition, heat pump dryers do not consume any fuel, which saves transportation and storage fuel costs. The economic benefits are even more obvious.

Safe and environmentally friendly. The heat pump dryer achieves the purpose of drying by transferring the heat in the air to the drying room, so it only consumes the electricity to carry the heat. There is no need to consume other fuels, that is, to avoid the safety and environmental pollution problems that occur in the transportation and storage of fuels. No pollutants are produced during operation.

Good drying effect. Because the heat pump dryer adopts automatic control, the operating state of the unit can be automatically adjusted according to the set mode, the temperature is stable, the temperature is uniform, and the temperature difference is less fluctuating, avoiding the influence of human factors on the drying quality during the operation of the fuel dryer.

Energy efficiency is high. The heat pump has a more efficient heating capacity than direct energy supply, which is reflected in its heating energy consumption ratio (COP) is always higher than 1, and in the heat pump drying system, in addition to the electric energy from the compressor, the drying hot air The heat energy also comes from the heat energy contained in the dry exhaust gas absorbed by the evaporator. Researchers have found that compared with steam drying, the energy saving rate can still reach about 40%-70%.

5. What are the common drying room structures?

According to the state of the material in the drying room, it can be divided into two types: static drying system and dynamic drying system.

The static drying system is a common material that enters the drying room in the form of a cart (material rack) and pallets. The material does not move during the whole drying process (except for the reversing of the tray), and the material is loaded and unloaded manually. Applicable For materials with long drying time, slow water output, and small drying capacity, the disadvantage is that the labor cost is high;

The dynamic drying system is commonly referred to as a drying assembly line. The incoming and outgoing materials are completed by a lifting device or a discharging device. The materials are dried in a dynamic manner on the conveyor belt. It is suitable for materials with large drying capacity and short drying time. The disadvantage is that the investment is high and the size of the installation location is large.

6. What factors will affect the drying of materials?

The essence of material drying is to remove the moisture of the material, and the factors that affect the removal of moisture include the temperature in the drying room, wind speed (circulating air volume), surface area, relative humidity (air in the drying room), the moisture speed of the material itself, and the shape of the material.

The main function of temperature is to evaporate the water inside the material. Generally speaking, the higher the temperature, the faster the water will come out. Different materials require different drying temperatures. Another function is to ensure the shape and color of the finished product after drying.

The main function of the wind speed is to bring heat to the material and take away the moisture on the surface of the material. Enough air volume can ensure the complete circulation of the air inside the warehouse. It needs to be designed according to the characteristics of the material and the parameters of the unit.

The surface area is the paving thickness of the material. The greater the surface area of the material in contact with the air, the faster the moisture will be taken away. Relative humidity. The lower the relative humidity of the air in the drying room, the faster the material will flow out, but not all The material or different drying stages are suitable for rapid water discharge. Some people may think that the thinner the material, the better, but in fact, the larger the surface area, the faster the wind flow rate, and the heat absorbed by the material will decrease.

The material's own moisture dissipation speed is determined by the material's own characteristics, and it is also one of the important factors that affect the drying time and equipment selection. Generally speaking, the rapid moisture dissipation takes a small amount of short time to dry, and the slow moisture dissipation uses an increase in quantity to extend Drying in time; the main forms of materials include strips, blocks, flakes, powder, etc. Generally speaking, the drying efficiency of flake materials is faster, and the drying efficiency of lump or rhizomes is slower. The shape of the material determines the material. The way of placing and the design of the air duct.

7. What are the ways to design the air duct in the drying room?

The air duct design of the drying room plays a vital role in the uniformity and efficiency of drying. In the air duct of the drying room, it is mainly necessary to avoid and reduce the dead angle of heat and air volume as much as possible, and in a simple and economical way , In the drying tunnel design, the through-flow and flat-flow are generally adopted.

The so-called through-flow type is the wind-up or bottom-up air duct structure form through the material. The through-flow type is widely used in the drying of suspended materials, such as bacon, sausages, duck, and other meat products and noodles, Noodles, tobacco leaves and other materials that can keep their shape better when hung.

The advection type refers to the air duct structure form where the wind passes through the material and the surface of the pallet uniformly from the horizontal direction. The advection type is mainly used for flat materials, such as flakes, blocks, flowers, fine particles and other materials. The common ones are: Bergamot slices, banana slices, apple slices, fungi, chrysanthemums, roses, starch, etc., advection is the most widely used, suitable for most types of objects, and the wind blows evenly and parallel across the surface of each layer. Theory The effect is the best, and the versatility of the shelf pallet is the best.

Generally speaking, the air outlet of the main engine is relatively small. If the air volume is not enough, you can add a fan at the front end. In order to make the air volume difference in each area not large, you can add a uniform air plate to the air outlet to make a return zone and increase the heat dissipation area. .

8. How to select the type of heat pump drying unit and design the warehouse body?

It is necessary to understand the characteristics of the materials when designing the warehouse body and selecting the unit. Generally, the backward method is adopted, that is, the pallets and material racks are planned and designed according to the amount of material to be baked and the discharge requirements, and then the warehouse body is carried out according to the required position of the material rack. Design and host configuration.

The configuration of the host should be selected according to the moisture content of the material, the speed of the water output, and the required drying time. For example, how much space is needed for 1000 kg of materials, I can calculate the size of the drying room, and the configuration of the host depends on how much water needs to be removed.