The DH Series Combined Compressed Air Dryer is designed for compressed air systems that require reliable low-dew-point performance in a compact, integrated configuration.
It combines an AH Series refrigerated air dryer with an HH Series regenerative adsorption dryer, allowing the system to first remove a large portion of moisture through refrigeration and then use adsorption drying for deeper moisture removal.
The DH Series Combined Compressed Air Dryer is available with different cooling and regeneration configurations, making it suitable for industrial users who need a pressure dew point of ≤−40°C while keeping installation and system integration relatively straightforward.
How Does the DH Series Combined Dryer Work?
The DH Series uses two drying stages.
In the first stage, compressed air enters the refrigerated dryer section. The air is cooled so that water vapor condenses into liquid moisture, which can then be separated and discharged.
After this pre-drying stage, the compressed air enters the adsorption section. The HH Series adsorption dryer uses activated alumina and high-performance molecular sieve to remove the remaining water vapor.
This two-stage treatment reduces the moisture load reaching the adsorption bed and allows the system to achieve a much lower pressure dew point than a refrigerated dryer alone.
Depending on the selected configuration, the adsorption section can use:
- Heatless regeneration
- Heated purge regeneration
The refrigeration section can also be configured as:
- Air-cooled
- Water-cooled
This makes the DH Series adaptable to different plant layouts, operating conditions, and compressed air requirements.
DH Series Operating Conditions
The standard DH Series operates under the following conditions:
- Applicable Medium: Compressed air / non-corrosive air
- Rated Inlet Pressure: 0.7 MPa
- Operating Pressure Range: 0.6–1.0 MPa
- Rated Inlet Temperature: 50°C
- Maximum Inlet Temperature: ≤80°C
- Regeneration Method: Heatless / heated purge regeneration
- Cooling Method: Air-cooled / water-cooled
- Outlet Pressure Dew Point: ≤−40°C
- Desiccant: Activated alumina + high-performance molecular sieve
- Rated Ambient Temperature: 35°C
- Ambient Operating Range: 2–45°C
- Standard Maximum Airflow: 45 m³/min
For airflow above 45 m³/min or applications involving unusual materials, temperatures, pressures, or other technical requirements, a custom-engineered configuration should be evaluated.
Why Use a Combined Refrigerated and Adsorption Dryer?
A combined dryer allows the refrigeration and adsorption stages to share the moisture-removal workload.
The refrigerated section removes bulk moisture first. This reduces the amount of water vapor that reaches the adsorption section.
The adsorption stage then performs the deeper drying needed to reach a pressure dew point of ≤−40°C.
This arrangement can provide several practical advantages:
- Lower moisture load on the adsorption bed
- Stable low-dew-point performance
- More compact equipment layout
- Simplified installation
- Reduced interconnecting pipework
- Better coordination between pre-drying and adsorption stages
- Improved protection for downstream equipment
For users comparing different drying technologies, Lingyu also provides a broader range of compressed air treatment products for different pressure, dew-point, and airflow requirements.
How to Choose the Right DH Series Dryer
Correct selection should be based on actual operating conditions rather than compressor nameplate capacity alone.
Determine Peak Airflow
The dryer should be sized according to the maximum airflow expected during production.
Standard DH Series capacities extend up to 45 m³/min.
A reasonable capacity margin can help accommodate short-term demand increases, but excessive oversizing should be avoided because it increases equipment cost without necessarily improving system performance.
Check Operating Pressure
The standard rated inlet pressure is 0.7 MPa, with an operating range of 0.6–1.0 MPa.
Actual dryer capacity changes with pressure, so systems operating significantly above or below the rated condition should be evaluated before final model selection.
Consider Inlet Temperature
The DH Series has a rated inlet temperature of 50°C and a maximum inlet temperature of 80°C.
Higher inlet temperatures increase both the heat load and moisture load entering the dryer.
The refrigerated section is therefore particularly important because it cools the compressed air before adsorption drying.
Define the Required Pressure Dew Point
The standard DH Series is designed for an outlet pressure dew point of ≤−40°C.
This level of dryness is appropriate for processes where moisture can interfere with pneumatic equipment, instruments, electronics, production quality, or downstream gas treatment.
If the application only requires moderate drying, a standalone refrigerated air dryer may be sufficient.
Heatless vs. Heated Purge Regeneration
The regeneration method has a direct effect on system simplicity and compressed air consumption.
Heatless Regeneration
Heatless regeneration uses part of the dry product air to regenerate the saturated desiccant.
Its main advantages are a simple operating structure and fewer heating-related components.
It can be appropriate when:
- Straightforward maintenance is a priority
- System capacity is moderate
- Purge-air consumption is acceptable
- Simple regeneration control is preferred
Heated Purge Regeneration
Heated purge regeneration uses external heat to help release moisture from the desiccant.
This generally reduces the amount of dry compressed air required for regeneration compared with a conventional heatless process.
It may be more suitable for facilities where:
- The dryer operates continuously
- Compressed air cost is significant
- Purge-air reduction is important
- Long operating hours justify a more energy-conscious regeneration strategy
The most suitable option should be selected according to total operating conditions rather than assuming one regeneration method is always more efficient.
Air-Cooled vs. Water-Cooled Configuration
The cooling method should also be matched to the installation environment.
Air-Cooled
Air-cooled systems reject heat directly to the surrounding air.
They are generally easier to install because they do not require a cooling-water system.
They are often suitable where:
- Cooling water is unavailable
- Installation simplicity is important
- Ambient temperature is controlled
- Adequate ventilation is available
Water-Cooled
Water-cooled configurations transfer heat through a cooling-water circuit.
They may be preferable where ambient temperature is high or where the facility already has stable cooling-water infrastructure.
Cooling-water temperature, pressure, quality, and flow should all be considered during system design.
Integrated Design and Installation Advantages
The DH Series combines major drying stages into one integrated system rather than requiring users to install separate refrigerated and adsorption dryers as independent equipment packages.
This can reduce:
- Equipment footprint
- Installation complexity
- Interconnecting pipework
- On-site assembly work
- Coordination between individual dryer sections
The standard combined dryer also includes one intermediate filter, while additional intermediate filters can be added when required by the application.
Typical Industrial Applications
The DH Series is suitable for processes where compressed air must remain consistently dry and where a refrigerated dryer alone cannot meet the required dew point.
Electronics and Semiconductor Manufacturing
Moisture can interfere with sensitive manufacturing equipment, pneumatic systems, and process stability.
In electronics and precision manufacturing, low-dew-point compressed air can support automation systems, testing equipment, pneumatic controls, and moisture-sensitive production processes.
For semiconductor and PCB manufacturing, deeper moisture removal can be valuable where compressed air quality is closely linked to process stability.
Laboratory and Analytical Equipment
Analytical instruments and laboratory processes can require stable, dry compressed air.
The DH Series can support laboratory and analytical equipment applications where moisture-sensitive instruments or pneumatic systems are used.
Medical and Dental Systems
Medical and dental compressed air systems may require carefully controlled air quality.
For medical and dental applications, a combined dryer can form part of a broader compressed air purification system configured according to the required final air quality.
Automotive and General Manufacturing
Dry compressed air helps protect pneumatic components, actuators, control valves, tools, and production equipment.
The DH Series can therefore support automotive and general manufacturing where a low pressure dew point is required.
Other potential uses include robotic systems, air bearings, instrument air, dry sprinkler systems, pneumatic automation, testing equipment, and other moisture-sensitive processes.
Why the DH Series Uses Two Adsorbents
One key difference between the DH and DC Series is the adsorption material.
The DH Series uses activated alumina together with high-performance molecular sieve.
Activated alumina provides strong moisture adsorption and good mechanical durability, while molecular sieve supports deeper moisture removal under demanding low-dew-point conditions.
The combined adsorbent system is therefore well suited to applications that require a consistent pressure dew point of ≤−40°C.
The Importance of Filtration
Compressed air can contain oil aerosols, particles, rust, condensed water, and other contaminants.
If these contaminants reach the adsorption bed, they can reduce adsorption capacity and shorten desiccant life.
Proper upstream treatment is therefore essential.
The refrigerated section and intermediate filtration help reduce the contamination load before the air reaches the adsorption stage.
Where additional filtration is needed, a suitable precision compressed air filter can be integrated into the treatment system.
Downstream filtration may also be used where fine desiccant particles must be prevented from reaching sensitive equipment.
Maintenance Tips for Long-Term Reliability
The integrated design simplifies installation, but both drying stages still require regular inspection.
Monitor Outlet Dew Point
A rising dew point can indicate:
- Increased airflow
- Excessive inlet temperature
- Refrigeration-stage problems
- Insufficient regeneration
- Desiccant contamination
- Valve leakage
- Filter restriction
Monitoring dew-point trends provides an early indication that the system is moving away from normal operation.
Check Refrigeration Performance
The refrigerated section should maintain stable cooling and effective condensate separation.
If this stage does not remove enough moisture, the adsorption section must handle a much higher water load.
This can shorten adsorption cycles and reduce desiccant life.
Inspect Condensate Drains
Condensed water should be discharged reliably.
Blocked or malfunctioning drains can allow liquid water to move downstream and overload the adsorption stage.
Check Filters
The standard intermediate filter and any external filters should be inspected regularly.
A clogged filter increases pressure drop, while a damaged or saturated filter may allow contaminants to enter the adsorption bed.
Verify Regeneration Cycles
For heatless configurations, check purge flow, vessel switching, depressurization, and repressurization.
For heated purge configurations, heating and regeneration functions should also be inspected as part of the maintenance schedule.
Monitor Desiccant Condition
Activated alumina and molecular sieve should be checked for contamination, dusting, or declining adsorption performance.
Replacement timing should reflect actual operating conditions, inlet air quality, and dryer performance rather than relying only on a fixed calendar interval.
How to Improve Energy Efficiency
The DH Series should be evaluated as part of the complete compressed air system.
Several operating practices can improve overall efficiency.
Keep the refrigerated section operating correctly. Effective pre-drying reduces the regeneration burden on the adsorption stage.
Maintain clean filters. Excessive pressure drop increases compressor energy consumption.
Choose the correct regeneration method. Heatless regeneration favors simplicity, while heated purge regeneration can reduce compressed air consumption in suitable applications.
Avoid excessive compressor pressure. Higher-than-required pressure increases energy demand throughout the system.
Repair leaks. Air leaks increase compressor loading and the total amount of air that the dryer must process.
Monitor dew point. Stable dew-point data helps operators identify problems early and avoid unnecessary adjustments.
DH Series vs. DC Series
The DH and DC Series both combine refrigerated and adsorption drying, but their adsorption sections are different.
The DH Series combines an AH refrigerated dryer with an HH Series adsorption dryer and uses activated alumina plus high-performance molecular sieve.
The DC Series Combined Compressed Air Dryer combines the refrigerated stage with a CH Series adsorption dryer and uses activated alumina.
For applications where deeper moisture adsorption and a multi-adsorbent configuration are preferred, the DH Series may be the more suitable choice.
A Practical Solution for Low-Dew-Point Compressed Air
The DH Series Combined Compressed Air Dryer integrates refrigerated drying with HH Series adsorption technology to provide a pressure dew point of ≤−40°C.
With air-cooled or water-cooled configurations, heatless or heated purge regeneration, activated alumina plus high-performance molecular sieve, and standard capacities up to 45 m³/min, the DH Series can be adapted to a wide range of industrial compressed air systems.
Correct selection should consider airflow, pressure, inlet temperature, target dew point, regeneration method, cooling method, filtration, and actual production demand together.
For larger capacities or special operating conditions, contact Lingyu with your airflow, pressure, inlet temperature, required dew point, cooling conditions, and preferred regeneration method.
