Industrial cooling basics – which solution fits your plant?

4. Adiabatic cooler

Operating principle

An adiabatic cooler is a combination of a dry cooler and an evaporative system. It essentially operates as a dry cooler, but when the ambient air is too warm for efficient cooling, adiabatic pads (wetted filter panels) are activated.

The air passing through the wetted panels cools down (through the heat-absorbing effect of evaporation), and this pre-cooled air then flows across the finned coil. With this method the summer performance of the dry cooler improves significantly, while in winter and the transitional seasons the unit operates as a pure dry cooler.

The adiabatic cooler approaches the wet-bulb temperature — but it cannot guarantee a stable 15–20 °C leaving temperature at summer peak. In a Hungarian summer (35 °C, 50% humidity) the leaving water is around 28–33 °C.

Comparison – Dry cooler vs. adiabatic vs. cooling tower

Period	Humidity	Dry / wet bulb	Dry cooler	Adiabatic	Cooling tower	Note
Spring	45%	20 °C / 13 °C	~27 °C	~20 °C	~18 °C	All good
Summer, dry	30%	33 °C / 20 °C	~40 °C	~26 °C	~24 °C	DC poor!
Summer, humid	60%	33 °C / 26 °C	~40 °C	~33 °C	~30 °C	Humidity hurts!
Heatwave	40%	35 °C / 23 °C	~42 °C	~30 °C	~28 °C	Tower wins
Autumn	55%	15 °C / 10 °C	~22 °C	~16 °C	~15 °C	All good
Winter	75%	2 °C / 0 °C	~9 °C	~7 °C	~5 °C	Min. difference

Tip: The best compromise for many industrial applications is the adiabatic dry cooler: closed loop (no Legionella), F-gas-free, and even in summer it delivers 25–33 °C water — perfect for oil cooling and condenser cooling. But if you need a guaranteed water temperature of 15–25 °C → a chiller is required.

5. Air-cooled chiller

Operating principle

The air-cooled chiller is the most common industrial liquid-cooling type. It contains a compressor refrigerant circuit in which refrigerant (e.g. R-410A, R-454B, R-134a) is circulated. The compressor compresses the refrigerant, which gives off heat to the air in the condenser (using fan-equipped heat exchangers); after passing through the expansion valve the refrigerant undergoes a pressure drop and absorbs heat from the process fluid in the evaporator.

This technology can produce a leaving fluid temperature as low as 5 °C, or even below freezing point, regardless of the outdoor temperature.

Advantages

• Precise temperature control – accurate to within ±0.5 °C
• Independent of ambient temperature – cools steadily even in summer
• Compact, all-in-one unit – no cooling tower required
• Quick installation – plug & play (water + electrical connection)
• Closed loop – no water consumption, no Legionella

Disadvantages

• Higher energy consumption due to the compressor (COP 2.5–3.5)
• Contains refrigerant → F-gas obligations, leak testing, registration
• Noise emission from the compressor and fans (65–85 dB)
• On hot summer days the COP decreases (the condenser releases heat less easily)
• Higher maintenance demand (compressor, refrigerant circuits, electronics)

6. Water-cooled chiller

Operating principle

The water-cooled chiller is based on the same compressor refrigerant circuit as the air-cooled chiller, but the condenser heat is removed not by air but by water. This requires a separate water circuit between the condenser and a cooling tower (or other heat-rejection device).

The water-cooled condenser (shell-and-tube or plate heat exchanger) provides significantly more efficient heat transfer than the air-cooled version, so the COP of the water-cooled chiller is higher: typically 4.5–6.0. The price, however, is also higher because of the cooling tower's installation and operation.

Advantages

• Highest energy efficiency among chillers (COP 4.5–6.0)
• Excellent at high capacities (>200 kW)
• Stable operation even on hot summer days

Disadvantages

• Complex system – chiller + cooling tower + two water circuits + water treatment
• High capital cost (cooling tower, pipework, pumps)
• Cooling-tower maintenance: water treatment, Legionella prevention
• F-gas obligations because of the refrigerant

7. Comparison matrix

The table below summarises the most important characteristics of the five main cooling technologies side by side:

Aspect	Cooling tower	Dry cooler	Adiabatic	Air-cooled chiller	Water-cooled chiller
Leaving temp. (summer)	28–32 °C	40–45 °C	25–30 °C	5–20 °C	5–15 °C
Leaving temp. (winter)	5–15 °C	5–15 °C	5–15 °C	5–20 °C	5–15 °C
COP / EER	20–40	20–40	15–30	2.5–3.5	4.5–6.0
Capital cost	Medium	Low	Medium-High	Medium	High
Operating cost	Low	Very low	Low	Medium-High	Medium
Water consumption	High	Zero	Moderate	Zero	High
F-gas obligation	None	None	None	YES!	YES!
Legionella risk	YES!	None	Minimal	None	YES! (tower)
Noise level	Medium	Medium	Medium	High	Low (indoor)
Maintenance	High	Low	Medium	Medium	High
Installation	Medium	Simple	Medium	Simple	Complex
Typical size	50 kW – MW	10 kW – 2 MW	20 kW – 2 MW	5 kW – 1.5 MW	100 kW – 10 MW

Legend: COP = coefficient of performance (higher is better)

8. Decision aid – Which one should I choose?

The choice of the right cooling system depends on the answers to the following key questions:

What temperature do you need?

• If a stable temperature of 5–15 °C is required even in summer → chiller (air-cooled or water-cooled)
• If 25–35 °C is acceptable → cooling tower, adiabatic or dry cooler
• If cooling is sufficient in winter/autumn and not critical in summer → dry cooler

How important is energy efficiency?

• Maximum savings → dry cooler or cooling tower (but limited summer temperature!)
• Good compromise → hybrid chiller with free cooling (e.g. ECO series) — 30–60% savings!

Is being F-gas-free important?

• If you want to avoid F-gas registration → cooling tower, dry cooler, adiabatic
• If it is not a concern → air- or water-cooled chiller (or hybrid)

But what if you want both: a guaranteed water temperature in summer AND low energy costs in winter?

The answer is a hybrid chiller — and within that, the ECO series.

9. ECO Series – The best of both worlds

What is a hybrid chiller?

The hybrid (free-cooling) chiller combines two technologies in a single unit: a compressor refrigerant circuit and an integrated free-cooling (dry-cooler) section. The control system automatically selects the operating mode based on the ambient temperature.

Winter mode (approximately November – March)

When the outdoor temperature is low (<10–15 °C), the compressor SWITCHES OFF. The unit cools using only its fans, like a dry cooler. The energy consumption is then limited to that of the fans: a fraction of the consumption of compressor mode.

Transitional mode (spring, autumn)

The free cooler and the compressor work TOGETHER. The free-cooling section pre-cools the water, and the compressor only removes the residual heat. This significantly reduces the load on, and consumption of, the compressor.

Summer mode (approximately June – August)

On hot days the compressor takes the leading role, but the free cooler still helps — particularly at night and during cooler hours. The leaving water temperature is stable and guaranteed, in contrast to an adiabatic cooler.

Advantages of the ECO series

• Guaranteed leaving water temperature: 5–20 °C, regardless of season
• 30–60% annual energy savings compared with a conventional air-cooled chiller
• A single unit – no need for separate dry cooler + chiller + control system
• Automatic mode switching – no human intervention required
• Extended compressor life – it does not run in winter, so fewer operating hours
• Plug & play installation – water and electrical connection, ready
• Closed loop – no water consumption, no Legionella

Payback calculation – Example

The example below compares the annual energy costs of a plastics-processing plant with a 200 kW cooling demand for a conventional air-cooled chiller and an ECO hybrid chiller. The plant operates 16 hours a day, 250 days a year.

Input data

Cooling demand	200 kW
Operating time	16 hours/day × 250 days = 4,000 hours/year
Electricity price	HUF 60/kWh (Hungarian industrial average, 2025)
Conventional chiller COP	3.0 (average; 2.5–3.5 depending on season)
ECO hybrid chiller COP (annual average)	5.5–7.0 (free-cooling share ~50–65% in the Hungarian climate)

Annual energy-cost comparison

	Conventional chiller	ECO hybrid
Electrical input	200 / 3.0 = ~67 kW	200 / 6.0* = ~33 kW
Annual consumption	67 × 4,000 = 268,000 kWh	33 × 4,000 = 132,000 kWh
Annual electricity cost	268,000 × 60 = HUF 16,080,000	132,000 × 60 = HUF 7,920,000
ANNUAL SAVINGS	~HUF 8,160,000/year

* The annual average COP takes into account the share of free cooling: in winter COP 15–30, in transitional seasons COP 5–8, in summer COP 2.5–3.5. In the Hungarian climate the annual average is approximately 6.0.

Payback time

The price premium of an ECO hybrid chiller over a conventional air-cooled chiller is typically 25–40%. For a 200 kW unit this represents an additional capital investment of approximately HUF 3–6 million. With annual savings of around HUF 8 million, this means the premium can pay back within 6–10 months.

When does the ECO series pay off?

• Plastics injection moulding, blow moulding – where stable cooling is needed all year round
• If the existing dry cooler / adiabatic cooler cannot cope with the summer peak (water at 30 °C+)
• If energy efficiency and reduction of operating costs are important
• If you would prefer a single, compact unit instead of two (chiller + dry cooler)

10. Frequently asked questions

What is COP?

COP (Coefficient of Performance) measures cooling efficiency. A COP of 3.0 means that the unit produces 3 kW of cooling capacity from 1 kW of electrical energy. The higher the COP, the better.

What are wet-bulb and dry-bulb temperatures?

The dry-bulb temperature is the ordinary air temperature. The wet-bulb temperature also takes humidity into account – it is always lower than or equal to the dry bulb. In dry climates the difference is large; in humid climates it is small. In a Hungarian summer the wet bulb is typically 20–24 °C, while the dry bulb is 30–38 °C.

Is F-gas registration required for a dry cooler?

No. The dry cooler, the cooling tower and the adiabatic cooler do not contain refrigerant, so no F-gas obligations apply to them.

Why does my existing adiabatic cooler not maintain 25 °C in summer?

An adiabatic cooler physically cannot cool below the wet-bulb temperature + 5–8 °C. In a Hungarian summer (35 °C air, 40–50% humidity) the wet bulb is around 24–26 °C, so the best achievable water temperature is 29–34 °C. If you want stable water at 15–25 °C → the solution is a hybrid chiller (ECO series).

How much does an ECO hybrid chiller cost?

The price of the ECO series depends on capacity and configuration. Contact CIS for a tailored quotation and a payback calculation.

We help you choose the right solution

Every project is unique. CIS experts offer a free consultation to help you choose the cooling technology best suited to your application and climatic conditions, and present a concrete payback calculation.