Series-HXVB
HXV Series Operation Modes & Water-Saving Strategies
Based on the CTI-certified FXV closed-circuit cooling tower platform, the HXV series integrates BAC’s patented hybrid flow technology. A dry finned coil section is added at the discharge area, delivering enhanced heat transfer efficiency with lower fan energy consumption.
Three Modes of Operation – HXV
| Operation Mode | Dry Coil Flow | Wet Coil Flow | Spray Pump | Fan(s) |
|---|---|---|---|---|
| Hybrid Wet/Dry Mode | 100% | Modulating | ON | ON |
| Adiabatic Mode | 100% | 0% | ON | ON |
| Dry Mode | 100% | 100% | OFF | ON |
Maximize Water Savings
Hybrid Wet/Dry Mode
In this mode, the process fluid first flows through the dry finned coil for initial cooling and then enters the main evaporative coil section for further cooling. Spray water is pumped from the cold water basin to the top of the evaporative coil. As the water flows over the coil surface, evaporative cooling occurs. The water then falls onto the fill layer beneath, where it is further cooled by the airflow before returning to the basin.
The air that flows through the coil and fill surfaces absorbs heat and moisture, becoming saturated. However, the discharge air remains relatively cool, allowing the finned coil located above the fan to extract additional heat from the process fluid.
By combining sensible heat transfer in the dry coil with latent heat exchange in the evaporative section, this mode dramatically reduces visible plume formation—even under peak operating conditions—while significantly saving water compared to conventional evaporative systems.
As thermal load and/or ambient temperature decrease, the evaporative demand and water usage naturally decline. This is controlled by an automatic bypass valve that modulates the fluid flow to the evaporative coil, maintaining the required leaving fluid temperature.
The control strategy ensures that the dry coil is used to its fullest capacity before increasing evaporative load, minimizing water consumption and reducing visible plume by heating discharge air through the dry coil section.
Adiabatic Mode
In adiabatic mode, the process fluid completely bypasses the evaporative coil—no heat transfer occurs within the wet coil section. Instead, spray water is used solely to saturate the incoming air, pre-cooling it through adiabatic cooling.
Even in most climates, ambient air has enough capacity to absorb moisture, and the resulting pre-cooled air significantly enhances the sensible heat transfer rate in the dry coil.
Compared to traditional evaporative systems, adiabatic mode drastically reduces both water consumption and visible plume, while maintaining the required fluid temperature and maximizing system efficiency.
Dry Mode
In dry mode, the spray water system is turned off, saving pump energy. The process fluid flows in series through both the dry finned coil and the evaporative coil, with the control valve fully open to ensure the full heat transfer surface is utilized.
This mode eliminates both evaporation and visible plume entirely.
HXV units can be configured to switch to dry operation at dry bulb temperatures between 50°F (10°C) and 60°F (15°C) or higher, depending on the project’s specific needs.
If dry mode is expected to run for extended periods, it is recommended to drain the cold water basin, eliminating the need for antifreeze protection and water treatment.
