Counterflow vs Crossflow Cooling Towers: How They Compare
Counterflow and crossflow are the two basic ways to bring air and water together inside a cooling tower. Both work well. They make different trade-offs on footprint, pumping, maintenance access, and winter operation.
Our main product line, the CTS Model T-2, is a counterflow tower. We also build crossflow towers for larger jobs. This page explains each design on its own terms first, then explains why we use counterflow for the applications most of our customers have.
The difference in one picture
The names describe the direction of the air relative to the falling water.
Counterflow: air moves up, water moves down. They meet head on.
Crossflow: air moves sideways across water falling from basins above.
How a counterflow tower works
Water enters near the top and is spread over the fill by spray nozzles or a rotating sprinkler. The fan, usually at the top in an induced-draft design, pulls air in through louvers near the base. The air rises through the fill against the falling water, picks up heat through evaporation, and leaves through the fan stack.
Because the coldest air meets the coldest water at the bottom, and the warmest air meets the hottest water at the top, counterflow gets a lot of cooling out of a given volume of fill. That is its main strength.
Where counterflow does well
- Compact footprint. It typically needs less plan area for the same duty, which matters on tight sites, rooftops, and plant yards.
- Factory-built packages. Its compact shape suits towers that ship assembled or nearly assembled.
- Enclosed water. The fill and distribution system sit inside the casing, out of direct sunlight, which helps limit algae growth.
- Winter operation. Water stays inside the casing and away from the air inlet, which tends to make icing easier to manage than at open crossflow louvers.
Where counterflow has trade-offs
- Pump head. Water has to reach the distribution system at the top of the tower, and pressurized nozzles add pressure drop. That means more pump head than a gravity-fed crossflow basin, unless the distribution is designed for low pressure.
- Air resistance. Air travels up through the full depth of the fill, so fan selection matters.
- Access to distribution. Nozzles and sprinklers sit above the fill and under the fan, so they take more effort to inspect than open crossflow basins.
How a crossflow tower works
Hot water is pumped into open basins at the top of the tower. It flows by gravity through holes or nozzles in the basin floor and falls through fill packs on one or both sides. Air enters through louvers on the sides, moves horizontally across the falling water, turns into a central plenum, and leaves through the fan at the top.
Crossflow is a common choice for large commercial HVAC and for big rectangular, multi-cell installations.
Where crossflow does well
- Low pump head. Gravity distribution from open basins needs little pressure, which can save pump energy.
- Easy distribution maintenance. You can see and clean the hot-water basins and nozzles from the top, often while the tower is running.
- Internal access. Many larger crossflow towers have a walkable plenum for inspecting the fill and drift eliminators.
- Large and modular. Rectangular cells line up side by side, which suits big systems built in stages.
Where crossflow has trade-offs
- Larger footprint. It typically needs more plan area for the same duty.
- Exposed hot-water basins. Sunlight on open basins encourages algae unless the basins are covered.
- Winter icing. Ice can form on the air-inlet louvers and fill face in freezing weather, so cold-climate operation needs more attention.
Side by side
| Counterflow | Crossflow | |
|---|---|---|
| Air path | Vertical, straight up against falling water | Horizontal, across falling water |
| Water distribution | Pressurized spray nozzles or rotating sprinkler | Gravity-fed open hot-water basins |
| Footprint for the same duty | Smaller | Larger |
| Pump head | Usually higher | Usually lower |
| Distribution access | Inside the tower, under the fan | Open from the top |
| Sunlight on water | Shielded inside casing | Exposed unless basins are covered |
| Winter icing | Generally easier to manage | Louvers and fill face need attention |
| Typical use | Packaged towers, industrial process cooling, tight sites | Large HVAC, multi-cell and field-erected systems |
Thermal performance is not one of the differences. A properly selected tower of either type will deliver its rated water temperatures. Overall energy use depends on the specific selection, not on the configuration alone.
Why CTS builds counterflow
Most of our customers run process cooling and HVAC loads from 3 to a few hundred tons. They need a tower that fits the space they have, installs quickly, and keeps running with a small maintenance team. For that work, a round counterflow tower is the better fit. Here is why the Model T-2 is built the way it is.
It is compact and ships ready to set
The counterflow layout fits a lot of cooling into a small, round FRP casing. Most models through the mid range ship completely assembled. The 60-ton Model T-260, for example, is 78.75 inches in diameter and arrives ready to set and pipe. Larger models ship as modular components for site assembly.
The round shape is not sensitive to wind
Air enters evenly around the full circumference of a round counterflow tower. Prevailing wind direction does not affect performance, so there is no need to orient the tower on site or worry about which face points where.
Low-pressure distribution fixes counterflow's usual weakness
Counterflow towers often need extra pump head for pressurized nozzles. The T-2 uses a rotating sprinkler head instead. It spreads water evenly over round fill with little head pressure loss, and it has few parts to clog. Models T-23 through T-260 use an ABS sprinkler head with a stainless steel shaft; T-270 and above use an aluminum alloy head.
Simple drives, few moving parts
Models T-23 through T-2200 use a direct-drive fan motor, so there are no belts or gearboxes to maintain. Models T-2225 and larger use a low-noise belt drive, with gear drives as an option. Models T-240 and above include a ladder for access to the fan and sprinkler.
Enclosed water stays cleaner
The fill and distribution sit inside the FRP casing, out of the sun. That limits algae growth on the distribution system. The fill is honeycomb heat-embossed PVC rated for inlet water up to 130°F.
It scales in steps
The T-2 line runs from the 3-ton T-23 to the 1,500-ton T-3500. Larger loads, or loads that swing with the season, can use multiple towers. Shutting one down at light load saves fan energy and keeps you running if one tower is down for service.
When we recommend crossflow instead. CTS also builds rectangular crossflow towers: the LRC-N square crossflow, the RLC CTI-certified crossflow, and the LCC closed-circuit tower. These are a better fit for large HVAC plants, projects that need CTI-certified performance data, jobs where low pump head matters most, and sites that need walk-in access for maintenance. If one of those fits your project, we will tell you.
Popular T-2 counterflow models
| Model | Nominal tons | Heat rejection (BTU/hr) | Approx. flow (GPM) |
|---|---|---|---|
| T-23 | 3 | 45,000 | 9 |
| T-210 | 10 | 150,000 | 30 |
| T-225 | 25 | 375,000 | 74 |
| T-250 | 50 | 750,000 | 148 |
| T-260 | 60 | 900,000 | 177 |
| T-2100 | 100 | 1,500,000 | 296 |
| T-2150 | 150 | 2,250,000 | 444 |
| T-2200 | 200 | 3,000,000 | 592 |
| T-2300 | 300 | 4,500,000 | 888 |
| T-2500 | 500 | 7,500,000 | 1,481 |
| T-3000 | 1,000 | 15,000,000 | 3,011 |
| T-3500 | 1,500 | 22,500,000 | 4,516 |
Ratings at 60 Hz and 95°F / 85°F / 75°F wet bulb. See the sizing guide for the full T-2 range and how to pick a model.
Frequently asked questions
Is counterflow more efficient than crossflow?
Counterflow usually gets more cooling from a given volume of fill, so it needs a smaller footprint for the same duty. Total energy use depends on the specific fan and pump selection. A well-selected tower of either type will hit its rated temperatures.
Which is easier to maintain?
Crossflow distribution basins are easier to reach because they are open at the top. Counterflow distribution sits inside the tower. The T-2 reduces this difference with a simple rotating sprinkler, direct-drive fans through the T-2200, and bolted FRP panels that come off for cleaning.
Can I replace a crossflow tower with a counterflow tower?
Often, yes. A counterflow tower usually needs less plan area. Check the inlet height and pump head, since water enters higher on most counterflow towers. Send us your flow, temperatures, and current layout and we will confirm the fit. See our replacement and retrofit guide.
Which handles cold weather better?
Counterflow towers keep the falling water inside the casing, away from the air inlet, which generally makes icing easier to manage. Either type needs a winter plan in freezing climates. See our freeze protection guide.
Does CTS only build counterflow towers?
No. The T-2 counterflow line is our core product, and it covers most packaged applications. We also build LRC-N and RLC crossflow towers and the LCC closed-circuit tower for larger or specialized jobs.
For more background, see types of cooling towers and our comparison of FRP vs galvanized steel towers.
Not sure which design fits your project?
Send us your flow rate or heat load, entering and leaving water temperatures, location, and available space. We will recommend the right tower type and model.
Call 800-752-1905 or request a quote online.