Working principle

Compressed air passes through a Venturi tube and vertically impacts a stream of water, atomizing the water into tiny droplets. These droplets, traveling at an ultra-high speed close to the speed of sound, then directly strike—again in a straight line—the ultrasonic resonance amplifier positioned at the nozzle’s front end, thereby inducing an ultrasonic resonance phenomenon. Leveraging the principle of sound wave reflection, the enhanced ultrasonic energy overcomes the cohesive forces within the water droplets, causing them to break apart into numerous smaller, finer microdroplets. Moreover, these microdroplets transform from spherical particles into thin, film-like structures, increasing their surface area in contact with air by hundreds of times. As a result, the microdroplets not only absorb into the air rapidly but also more easily, achieving both cooling and humidification effects.

 

Without an ultrasonic resonance amplifier, it is generally impossible to generate large quantities of tiny water droplets measuring between 0.1 and 10 micrometers. Typically, upon impact, a significant number of tiny water droplets are produced, along with a small fraction of larger droplets. Moreover, no matter how minuscule these droplets may be, they remain in liquid form. To transform them into vapor, a smooth enthalpy conversion is required—this energy conversion demands both sufficient time and a specific amount of enthalpy; neither can be lacking. Therefore, before humidification begins, the air must first be preheated to increase the available thermal energy for conversion. The higher the desired humidity level of the supplied air, the longer the evaporation time and the greater the absorption distance required. Consequently, it is essential to install a water-blocking baffle at the rear section of the humidifier to filter out any unevaporated water, thereby preventing condensation from occurring.

 

The total humidification capacity of a two-fluid ultrasonic spray humidification system is unlimited. Multiple nozzles and valve groups can be connected in parallel, and the water source pressure can also be increased to achieve higher per-unit spray volume and efficiency.

 

Product Features

1. Mist humidification

Also known as isenthalpic humidification, it can both humidify and cool.

 

2. Ultrasonic atomizing nozzle

The specially designed dual-fluid ultrasonic atomizing nozzle made of stainless steel not only boasts high-pressure resistance and corrosion resistance with an extended service life, but also features a uniquely designed front-mounted adjustable bullet-shaped ultrasonic resonator that effectively enhances spray quality by producing finer water droplets that more readily blend with the air. Moreover, this nozzle offers excellent atomization performance even under a wide range of gas-liquid pressure differentials. The front-mounted adjustable bullet-shaped ultrasonic resonator allows for easy adjustment of the distance between the nozzle outlet and the resonator. Thanks to its ability to effortlessly fine-tune both the spray diffusion angle (arc) and atomization quality, the required humidification distance is significantly shorter compared to non-adjustable nozzles.

3. Proportional Control

Through both experimental testing and practical application, it has been found that for a two-fluid ultrasonic spray nozzle to achieve optimal atomization performance, the pressure differential between the air pressure and water pressure must be precisely maintained at around 1.0 to 1.5 kg/cm². To address this requirement, we have specially designed a differential-pressure system that ensures a fixed pressure difference relative to the air pressure, regardless of fluctuations in water pressure. By integrating high-quality pneumatic proportional flow control valves, pneumatic on-off control valves, and a specially engineered two-fluid ultrasonic spray nozzle, and employing a fully integrated and rigorously timed automatic control system, we can naturally regulate both water and air pressures under all operating conditions, thereby delivering the best possible atomization effect. Consequently, among all types of mist humidifiers, the two-fluid ultrasonic spray humidification system is the only one capable of achieving true proportional control. Thanks to its precise control capability, when the water flow rate is low, the air flow rate also decreases accordingly; and as the water flow rate increases, the air flow rate rises in tandem. As a result, air consumption is reduced by more than half, truly realizing energy-saving objectives.

 

 

As for ON-OFF control, it uses the full volume of compressed air regardless of the actual water demand. Not only does this result in poor atomization performance and wasteful consumption of compressed air, but it also makes it more difficult to maintain stable humidity control. This is because, in most “spatiotemporal environments,” the actual humidification requirement is often less than the design capacity. Moreover, the optimal atomization conditions require a pressure differential between the two stages of 1.0 to 1.5 kg/cm². When the system deviates from this operating point, the outcome is either poor atomization efficiency or unnecessary waste of air energy, leading to low overall efficiency.

Compressed air pressure and water pressure:

(1) When the compressed air pressure exceeds the water pressure by 1.0 to 1.5 kg/cm², the atomization efficiency and effect are excellent. The component that enables easy control of this critical parameter is a specialized differential-pressure system.

(2) When the compressed air pressure exceeds the water pressure by 2.0 kg/cm², the water flow gradually decreases and may even stop altogether, resulting in low efficiency, wasteful use of valuable compressed air energy, and increased costs.

(3) The operating water pressure should exceed 3 kg/cm²—and the higher the pressure, the better—since it is directly proportional to the efficiency of compressed air usage. This is because, as the water pressure increases, the water flow rate also increases; however, the air flow rate does not increase proportionally. In fact, after careful calculation, the unit air consumption actually decreases, resulting in even greater efficiency.

 

4. Virtually maintenance-free

If pure water is used in conjunction with purified compressed air, this product requires virtually no maintenance—simply perform a brief cleaning and inspection when restarting the unit after an extended period of inactivity to ensure optimal humidification performance.

 

5. The economic benefits are exceptionally favorable, enabling significant savings in costs associated with equipment procurement, installation, operation, and maintenance.

(1) Equipment procurement cost: The structure is relatively simple, and under high-flow demand, the cost is comparatively low.

(2) Easy installation: The quick-connect coupling design makes installation and maintenance remarkably simple. This can significantly reduce costs associated with installation, inspection, maintenance, and upgrades.

(3) Reducing the cooling load (saving energy): In high-temperature, low-humidity environments, direct misting into the air for humidification has a cooling effect that lowers the air temperature. Therefore, when used in such environments, it can reduce the amount of cooling water required and extend the service life of the cooling equipment, thereby saving significant related costs—such as expenses for chilled water, electricity, and the extended time between replacements.

(4) Low Power Consumption: Compared to electric-heating or electrode-type humidifiers, the mist-based humidifier consumes significantly less power—just 220VAC/50W. Regardless of the humidification capacity, it requires only 0.05 kW of power, thus enabling substantial savings on electricity bills. Moreover, by operating at lower voltage and load levels and utilizing air pressure as the driving force for its control components, this humidifier offers relatively higher safety.

(5) Operating costs: A large amount of medium-pressure compressed air is required for atomization, which constitutes the primary energy consumption.

(6) Structural Differences: Compared to electric-heating or electrode-type steam humidifiers, this model has simpler component parts, consisting of a control unit and a low-voltage, low-power operating system.

 

Valve Group: Fully pneumatically controlled with automatic gas/liquid differential pressure control, offering excellent safety and high operational efficiency. It can be designed for parallel connection of multiple units, meeting large-scale humidification demands with flexibility.

 

Two-fluid ultrasonic atomizing nozzle: The actual working unit responsible for performing atomization.

 

6. Highly scalable

The humidification capacity is highly flexible, making it suitable for a wide range of applications—from large-scale industrial central air conditioning systems to direct humidification in spacious areas. The capacity can range from 8 kg/hr all the way up to virtually unlimited, as the nozzles and valve groups are controlled in parallel, allowing for virtually unrestricted expansion.

 

7. Automatic cleaning function

Automatic Cleaning Function upon Power-On or Power-Off: Upon power-on and upon receiving a stop signal, the system automatically removes any residual water remaining in the pipeline and cleans the nozzles, thereby preventing scale buildup and bacterial growth inside the pipeline. This also enhances the nozzle’s efficiency and extends its service life. (See timing control diagram.)

 

8. Equipped with an LCD display and a microprocessor controller featuring programmable settings, this device can be adjusted to meet varying environmental conditions. It eliminates compatibility issues and is fully compatible with building’s central control systems. It accepts 2–10V or 4–20mA signals, making centralized control and management convenient.

 

9. Optional wind-speed safety switch: If the air volume is insufficient, the water mist cannot fully mix with the air, leading to condensation and compromising the humidification quality. Therefore, when this device detects that the wind speed falls below the preset lower limit, it will automatically shut down the humidification function to prevent potential hazards caused by excessive humidification in the air-conditioning unit or ductwork—for example, excessive condensation causing water dripping from the ducts, fostering the growth of harmful bacteria that pose health risks to employees, and shortening the service life of machinery and equipment...

 

Scope of application

Since the two-fluid ultrasonic spray humidification system uses water mist for humidification, it is an isenthalpic humidification process. As shown on the psychrometric chart, when water mist humidification is employed, the dry-bulb humidity drops rapidly. Therefore, this two-fluid ultrasonic spray humidification system is particularly well-suited for outdoor conditions characterized by high temperatures and low humidity. Not only does it effectively increase the relative humidity in the air, but it also helps lower the temperature, thereby significantly reducing the thermal load or power consumption of chillers and creating a more comfortable working environment—achieving multiple benefits in one go. Consequently, the two-fluid ultrasonic spray humidification system is ideally suited for a wide range of humidification applications, including low-temperature, high-humidity environments such as synthetic fiber spinning plants; low-temperature refrigerated fruit and vegetable preservation facilities; high-temperature, high-humidity tropical rainforest experimental stations; constant-temperature and constant-humidity semiconductor or cleanrooms; low-temperature, high-humidity art conservation facilities... and many other environments requiring humidification. Additionally, special applications such as artistic landscaping and artificial snowmaking are also ideal scenarios for utilizing the two-fluid ultrasonic spray humidification system.

 

Humidification methods

In summer, when temperatures and humidity levels are high, a two-fluid ultrasonic humidification system can be used to significantly lower the temperature. Alternatively, air conditioning can be employed to cool the air and reduce the temperature, thereby enhancing both the comfort of occupants and the quality of work. However, prolonged use of air conditioning to cool and dehumidify indoor air also leads to a reduction in relative humidity within the room. In settings such as hospitals or offices, this can result in people needing to drink more water or directly applying water to their lips and skin to prevent chapping or dehydration. In winter, on the other hand, conditions may become cold and dry—especially when a cold high-pressure system moves southward, bringing with it dry, frigid air. Under these circumstances, air conditioning systems must incorporate humidification functions. From an engineering perspective, when using a two-fluid ultrasonic humidification system in winter, the outdoor air should first be preheated to 26–35ºC or higher. After being humidified by water mist, the air is then reheated a second time before being introduced into the cleanroom, thus meeting the cleanroom’s requirements for constant temperature and humidity. For detailed instructions on the winter air humidification process, please refer to the attached “Humidification Procedure Table” and “Water Mist Humidification Curve Diagram.”

 

Humidification Schedule	Instructions
5°C DB, 50% RH	1. Assume outdoor air conditions
↓ Air preheating: 26–35ºC	2. Raising the dry-bulb temperature of the air increases its enthalpy, thereby reducing its relative humidity while keeping its moisture content unchanged.
↓ Water mist humidification: 14.5ºC, 72% RH	3. The fine mist produced by the water-mist humidifier is directly dispersed into the air to provide humidification. Water molecules absorb a large amount of latent heat and vaporize, then fully mix with the air, thereby increasing the air’s moisture content while significantly lowering the air temperature.
↓ Reheat the air and deliver it to the cleanroom. Cleanroom design conditions: 22ºC, 45% RH.	4. Heat the low-temperature, high-humidity air once again to reach the set temperature, facilitating constant-temperature control.

Design Example

1. Design Conditions

External air volume	100,000 CMH
Assume outdoor air conditions	5°C DB, 50% RH
Cleanroom Design Conditions	22ºC, 45% RH
Air conditioning unit dimensions	3000mm (w) × 3800mm (h)
Airflow velocity	2.5m/sec

 

2. Humidification Capacity Calculation

Outdoor air moisture content	5ºC, 50% RH = 0.00270 kg/kg DA
Cleanroom air humidity	22ºC, 45% RH = 0.00742 kg/kg DA
Difference in air humidity	= 0.00742 - 0.00270 = 0.00472 kg/kg DA
Air volume	= 100,000 m³/hr ÷ [(0.79 + 0.85) ÷ 2] m³/kg/DA = 121,951 kg/hr DA
Humidification capacity	= 121.951 kg/hr DA × 0.00472 kg/hr DA = 575.6 kg/hr

 

3. Design of a Two-Fluid Ultrasonic Spray Humidification System

Cleanroom Design Conditions	At 22ºC and 45% RH, the moisture content of the air is approximately equivalent to 73.79% RH at 14.13ºC DB (as shown by point 3 in the figure).
Preheating of outside air and water mist humidification	Outdoor air at 5°C DB and 50% RH (as shown by point 1 in the figure) The outdoor air is first preheated to 26ºC DB (as shown by point 2 in the figure). Mist humidification increases the moisture content to 73.79% RH and 14.13ºC DB (as shown by point 3 in the figure).
After the air is humidified	The air is reheated and then sent to the cleanroom, where the dry-bulb temperature rises to 22ºC DB. The relative humidity then drops to 45% RH (as shown by point 4 in the figure).

 

4. Product Selection

(1) Nozzle requirement: Divide the calculated humidification demand by a divisor obtained based on the air pressure and water pressure to determine the required number of nozzles.

(2) Nozzle requirement = Humidification demand ÷ Humidification capacity per nozzle = 575.6 kg/hr ÷ 8 kg/nozzle = 72 nozzles.

(3) Valve assembly requirements: To achieve optimal atomization performance, a single valve assembly can be paired with up to 20 nozzles.

(4) Valve group demand = Nozzle demand ÷ 20 nozzles per valve group = 72 ÷ 20 = 4 valve groups (if fewer than 20 nozzles are available, allocate 1 valve group).

(5) Selection

 

Example: UFP04072 – UF stands for ultrasonic spray humidification system; P stands for proportional control; 04 indicates the number of valve groups; 072 indicates the number of nozzles required.

(6) Supply water demand: Calculated based on the total number of nozzles and their humidification capacity.
The water supply demand exceeds 72 animals × 8 kg/hr = 576 kg/hr.

(7) Required air supply: Calculated based on the total number of nozzles and their individual demand rates.
Assuming the air pressure is 4 kg/cm² and the water pressure is 3 kg/cm², according to the table, the required air supply rate is greater than 72 × 80 L/min = 5.76 m³/min.

(8) Water baffle dimensions: Determined based on the cross-sectional area of the air-conditioning unit.

(9) Humidification Absorption Distance: This refers to the straight-line distance from the nozzle to the first obstacle. After water is atomized and sprayed from the nozzle, it takes a certain amount of time to absorb the sensible enthalpy from the air, transform into water vapor, and then diffuse into the surrounding air. Multiplying this time by the wind speed yields the required absorption distance. This distance is closely related to the outlet air humidity—specifically, the higher the relative humidity, the longer the absorption distance needed. If the distance is insufficient, large amounts of condensation will occur in the mist, preventing the humidity from rising effectively; therefore, careful attention must be paid to this issue.

(10) Nozzle installation space requirements (see installation diagram):
A. Distance between nozzles: Minimum parallel spacing of 300 mm
B. Distance between the nozzle and the ground (bottom of the air conditioning unit): A minimum of 600 mm is recommended.
C. Distance between the nozzle and the top of the air conditioning unit: A minimum of 400 mm is recommended.
Please adhere to the spacing requirements above to ensure humidification quality and prevent condensation and dampness on the inner walls.
The number of nozzles is directly proportional to the required humidification capacity, and the air velocity in typical designs is based on certain guidelines. By evenly distributing the nozzles throughout the air handling unit, satisfactory humidification levels can generally be achieved.

 

Terms of Use

1. Sufficient enthalpy

The two-fluid ultrasonic spray humidification system is a type of water-mist humidification that employs isenthalpic humidification and requires sufficient enthalpy. See the preceding instructions on the humidification process.

 

2. Water supply

Water quality: Deionized water (pure water) or municipal tap water; using pure water virtually eliminates maintenance requirements for the equipment.

Water temperature: 4–40 ºC

Water pressure: The required operating pressure must be greater than 3 bar; the higher the water pressure, the better.

Water Volume: Replenishment water demand = Number of nozzles × Humidification capacity per nozzle (8 kg/hr per nozzle); in actual use, pipeline pressure loss must be taken into account.

 

3. Gas supply

Filtration rating: 5 microns

Pressure: The required pressure must be greater than 4 bar.

Air Volume: Supply Air Demand = Number of Nozzles × Air Consumption per Nozzle: 80 liters/minute (assuming air pressure is 4 kg/cm² and water pressure is 3 kg/cm²)