Industrial heat pump drying system – Classification, Applications

Industrial heat pump drying system

Industrial heat pump drying system is an advanced drying technology, widely applied in industries. Operating based on the principle of pump heat cycle, this system offers many outstanding advantages.

Introduction to industrial heat pump drying system

Industrial heat pump drying system concept

Industrial heat pump drying system is an advanced drying equipment that uses heat pump technology to create hot and dry air, serving the drying process of industrial products. This system combines the principles of refrigeration and heating to create an efficient and energy-efficient drying environment.

Importance in production and processing:

  • Save energy: Use 3-4 times more effectively than traditional drying methods.
  • Quality control: Allows precise control of temperature and humidity, ensuring stable product quality.
  • Environmental protection: Reducing CO2 emissions due to energy efficiency.
  • Diverse applications: Suitable for many different types of products such as food, wood, pharmaceuticals, chemicals…
  • Improve productivity: Shorten drying time, increase production capacity.
  • Operational safety: Do not use excessive heat, reduce the risk of fire and explosion.

Operating principle

Heat pump mechanism:

  • The heat pump system operates based on the principle of compression and expansion of the refrigerant.
  • Main components include: compressor, condenser, throttle, and evaporator.

The process goes as follows:

  • The refrigerant is compressed, increasing pressure and temperature.
  • The hot medium passes through the condenser, radiating heat to the environment.
  • The medium is expanded through the throttle valve, reducing pressure and temperature.
  • The refrigerant passes through the evaporator, absorbing heat from the environment.

Drying process in industrial heat pump drying system:

  • The moist air from the drying chamber is drawn through the evaporator of the heat pump.
  • Here, the air is cooled to the dew point, and moisture condenses and is removed.
  • The dehumidified air then passes through the condenser, where it is heated up.
  • This hot and dry air is returned to the drying chamber.
  • This process is repeated continuously, creating a closed drying cycle.
Significant energy savings through reuse of heat from exhaust air
Significant energy savings through reuse of heat from exhaust air

Advantages of this process:

  • Heat reuse: Heat from refrigeration is reused to heat the air.
  • Humidity control: Can accurately adjust the humidity of the drying air.
  • Low temperature: Dry at lower temperature than traditional method, protecting product quality.

Industrial heat pump drying systems are increasingly widely applied in many industries due to their efficiency and energy savings.

Classification of industrial heat pump drying system according to heat source

Air-air industrial heat pump drying system

Detailed operating principle:

  • The outdoor evaporator absorbs heat from the environmental air.
  • The refrigerant in the evaporator changes from a liquid to a vapor state, absorbing heat.
  • The compressor compresses the medium vapour, increasing the pressure and temperature.
  • The hot medium vapor passes through the condenser in the drying chamber, transferring heat to the drying air.
  • The medium condenses into liquid, passes through the throttle valve and returns to the evaporator, starting a new cycle.

Efficiency and capacity:

  • The COP (Coefficient of Performance) coefficient usually ranges from 3.0 to 4.5.
  • Drying capacity can range from a few kW to hundreds of kW, depending on the scale.

Specific applications:

  • Drying wood, agricultural products, pharmaceuticals, seafood.
  • Suitable for areas with temperate or tropical climates.

Factors affecting performance:

  • Environmental air temperature and humidity.
  • Wind speed and air flow through the evaporator.
  • Required temperature of drying process.

Water-air industrial heat pump drying system

Water-air industrial heat pump drying system
Water-air industrial heat pump drying system
Detailed operating principle:
  • Water from the source (such as boreholes, lakes, rivers) is pumped through the evaporator.
  • The refrigerant in the evaporator absorbs heat from the water, entering a vapor state.
  • Compression, condensation and throttling processes are similar to air-to-air systems.
  • Water after heat exchange is discharged or recirculated (depending on design).
Efficiency and capacity:
  • The COP coefficient can reach 4.0 to 6.0, higher than air-to-air systems.
  • Capacity can be up to MW for large industrial applications.
Special technical requirements:
  • Water treatment systems are needed to avoid scaling and corrosion.
  • Design suitable pumping systems and pipes to ensure stable water flow.
Specific applications:
  • Large-scale drying in food, textile, paper industries.
  • Suitable for areas with abundant water sources and stable temperatures.

Classification of industrial heat pump drying systems by structure

Integrated industrial heat pump drying system

Detailed structure:

  • Heavy-duty steel frame contains all components.
  • The compressor is usually centrally located to balance the weight.
  • The condenser and evaporator are arranged to optimize air flow.
  • Integrated control panel with user interface.

Control technology:

  • PLC (Programmable Logic Controller) system to manage the entire process.
  • Built-in temperature, humidity, and pressure sensors.
  • Can connect to SCADA system for remote monitoring.

Power range:

  • Usually from 5 kW to 100 kW per unit.
  • Multiple units can be coupled to increase capacity.

Additional advantages:

  • Short installation time, can be operated immediately after connecting electricity and air ducts.
  • Easy to move when needing to change production location.

Separate industrial heat pump drying system

Detailed structure:
  • Outboard outdoor units (compressors and condensing units).
  • The indoor unit (evaporator unit) is located near or in the drying chamber.
  • Environmental piping connects components.
  • The central control cabinet can be conveniently located.

Design flexibility:

  • Multiple evaporators can be used for one outdoor unit.
  • Easily integrated with heat or solar recovery systems.
  • Allows optimization of installation space in the factory.

Power range:

  • Can reach hundreds of kW to several MW.
  • Suitable for large and continuous production lines.

Special technical requirements:

  • Careful calculation of the pipeline is needed to avoid pressure losses.
  • Requires high quality insulation system for pipes.
  • Professional technicians are needed to balance the system.
Operates at low temperatures, usually below 80°C
Operates at low temperatures, usually below 80°C

Factors to consider when choosing an industrial heat pump drying system

Production capacity and scale

Capacity Production scale Suitable system type
5 – 50 kW Small (50-500 kg/batch) Integrated, air-to-air
50 – 200 kW Average (500-2000 kg/batch) Integrated or separate, air-air or water-air
> 200 kW Large (> 2000 kg/batch) Separate, water-air

When considering production capacity and scale, it should be noted:

  • Forecast future production demand to avoid early upgrades.
  • Consider the scalability of the system (e.g. modular system).
  • Assessment of capacity flexibility to meet peak production seasons

Type of product to be dried

Product characteristics greatly influence system selection:

  • Heat sensitivity: Products susceptible to damage by high temperatures require systems capable of precise temperature control.
  • Size and shape: Affects the design of the drying chamber and air circulation system.
  • Initial humidity and end humidity requirements: Decide on drying time and required capacity.
  • Homogeneity: Heterogeneous products may require more complex drying systems to ensure even drying.

Specific examples:

  • Pharmaceuticals: Requires precise temperature and humidity control, often using small-scale integrated systems.
  • Wood: Long drying time is required, usually using large capacity decoupling system.
  • Agricultural products: Diverse in size and humidity, may need flexible systems with multiple drying modes.

Environmental conditions

Environmental factors affecting system performance and selection:

Environmental temperature and humidity:

  • Hot and humid climate: Prioritize water-air systems to ensure stable performance.
  • Temperate climate: Air-to-air systems can be more efficient and cost-effective.

Air quality:

  • Dusty environment: Need an efficient air filtration system, with separation system preferred for ease of maintenance.
  • Corrosive environments (e.g. near the sea): Requires anti-corrosion materials, which can affect costs.

Water availability:

  • Abundant: Water-air systems can be a good choice.
  • Limitations: Priority is given to air-to-air systems or water reuse systems.

Installation space:

  • Limitations: Priority is given to integrated systems.
  • Wide: Separate system can be used to optimize performance.

Investment and operating costs

System type Investment costs Operating costs Estimated payback period
Integrated air-air Low Medium 2-3 years
Air-air separation Medium Medium-Low 3-4 years
Integrated water-air Medium-high Low 3-5 years
Water-air separation High Low 4-6 years

Taking all of the above factors into consideration, decision makers need to balance technical performance and financial feasibility. Choosing the most suitable industrial heat pump drying system will depend on which factors are prioritized and the long-term goals of the business.

Please contact us immediately to receive professional advice and optimal solutions for your needs.

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