What is the k-value and how is it measured?

The k-value (heat transfer coefficient) indicates how much heat is transferred per unit area and Kelvin of temperature difference between heat source and coolant. It is determined through measurements or thermal simulation and expressed in W/m²K. COOLTEC offers thermal simulations to predict the k-value of your cooler.

Which coolant medium is suitable for which application?

Water offers the highest heat capacity and is cost-efficient. Water-glycol mixtures are frost-resistant and preferred in applications with temperature changes. For aggressive environments or pure water requirements, corrosion-resistant materials (stainless steel, coated aluminium) or special media are used.

What is the maximum allowable pressure drop?

This depends on your pump capacity and pipe cross-sections. Typical values range between 0.1 and 1.0 bar depending on the cooler design. COOLTEC provides pressure drop curves as a function of flow rate for each cooler, enabling precise system design planning.

Which materials are suitable for aggressive media?

Stainless steel is the first choice for aggressive media, acids, or alkalis. For pure water systems (deionised water), special coatings or stainless steel are required, as DI water can attack aluminium. Copper also offers high corrosion resistance for many media.

Liquid Cooling at High Power Density: Important Design Criteria

When air cooling is no longer sufficient, the correct design of a liquid cooler is critical. From k-value to pressure drop: the most important parameters.

When Does Liquid Cooling Become Necessary?

Liquid cooling is used when power density is high, installation space is limited, or precise component temperatures must be maintained reproducibly. The coolant medium (usually water or a water-glycol mixture) transports heat far more efficiently than air. The following key parameters are critical for reliable design:

1
k-Value (Heat Transfer Coefficient)
The k-value (in W/m²K) describes how much thermal power is transferred per area and temperature difference between component and coolant. The higher the k-value, the more efficient the cooler, and the smaller it can be at the same cooling capacity. Internally structured coolers (Structureflow) achieve significantly higher k-values than pressed-in tube coolers.
2
Pressure Drop in the Cooling Circuit
A higher k-value is generally associated with a higher pressure drop, since narrower channels or structures increase flow resistance. The pressure drop determines the requirements for pump and piping. It must be taken into account in the system design.
3
Material Selection: Aluminium, Copper or Stainless Steel
Aluminium is lightweight, easy to machine, and sufficiently thermally conductive for most applications. Copper transfers heat almost twice as well, but is heavier and more expensive, making it ideal for very high power densities. Stainless steel offers excellent corrosion resistance for aggressive media or pure water applications.
4
Manufacturing Process: Pressed-in Tubes or Internal Structures
Pressed-in tubes (Monopress, Interpress) transfer heat very reliably and are ideal for many standard applications. Milled or inserted channel and pin structures (Structureflow) enable maximum heat transfer through turbulent flow, while also resulting in higher pressure drop.
5
Tightness and Quality Assurance
Every COOLTEC liquid cooler is tested for tightness: from standard pressure tests to high-precision helium leak tests. Tightness is especially business-critical in sensitive environments such as electronics, food technology, or medical technology.

Suitable Liquid Cooler Designs

These three designs are particularly suited for demanding power densities:

Single-sided pressed Monopress

Single-sided pressed-in copper, aluminium, or stainless steel tubes. Proven, reliable, and available in many material variants. Ideal for high power dissipation with standardised cooling circuits.

Internally structured Structureflow

Internally structured cold plates with milled or inserted channel or pin structures. Highest k-value, ideal for hotspot cooling and maximum power densities.

Internally pressed Interpress

Internally pressed-in tubes for uniform bilateral component cooling. Particularly suitable when components on both sides of a base plate need to be thermally connected.