Changing the properties of water to improve energy efficiency.

Water is used in heating systems as it is a good heat transfer medium that is abundant and low-cost.
EndoTherm optimises water to influence heating system performance.


Although water is abundant and low cost, its thermophysical properties can be improved upon.

EndoTherm interacts with water’s hydrogen bond network to improve its thermophysical properties to maximise the ability of heating systems to deliver heat to the locations required at the times it is needed.

These changes can increase the rates at which rooms reach temperature and improve the ability of the heating system to respond to changes in demand.

This allows heating systems to better deliver heat to the right places, and at the right times to maximise system efficiency.

How much energy it takes to heat the buildings in which we live and work depends not only on how efficiently we can convert the energy source into heat, but also on how and when that heat is delivered to the spaces in which it is needed.

To better utilise the heat, a system needs to be able to move the heat effectively and responsively around the system.

Fluid properties play an important role in how well hydronic heating systems can meet the heat demands of buildings and their occupants.

Andrew Williams
PhD, M Eng

Manager of Research & Development

Dr Andrew Williams holds a first class Masters degree in Mechanical Engineering and PhD from Loughborough University.

Dr Williams has been an active researcher in the areas of energy and thermofluids since 2001, including co-leading a UK Fluids Network Special Interest Group and academic advisor for the Energy Technologies Institute.

In roles as Senior Lecturer at Loughborough University and Visiting Research Fellow at University of Chester he applied his expertise in energy and thermofluids to the challenge of heating system de-carbonisation and hydronic heat transfer modifiers.

Many thermophysical properties of water relate to the network of hydrogen bonds between the individual molecules.

EndoTherm interacts with this hydrogen bonding network influencing both the amount of bonds and how they alter with changing temperature, thereby improving a number of properties of the fluid such as rheology and specific heat capacity.

These changes can impact on rates of warmup and energy required to heat the hydronic fluid, the response behaviour of the system to controls such as thermostats and TRVs, and the amount of wasted energy once demand is met.

Such changes have cumulative effects throughout the system which contribute to improving the ability of the heating system to deliver heat at the right time and right place, maximising system efficiency as well as component efficiency.



Using EndoTherm we can influence water systems in the following ways…

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Bubble Behavior: Surface &

Bubbles within the fluid can occur because of entrained gases as well as degassing during heating or pressure changes. The presence of surface bubbles can inhibit heat transfer significantly. The presence of entrained air bubbles changes the flow behaviour, pump performance and heat transfer.

Surface bubbles are more easily removed with EndoTherm, and entrained bubbles tend to be significantly smaller. Internal surfaces remain clear during degassing as surface scratches are no longer preferential nucleation sites.

Changing Heat Capacity

The specific heat capacity of a liquid is the amount of heat required to raise the temperature of a given amount of the liquid by on degree.

Changing heat capacity affects fluid temperatures, fluid embedded energy and warmup rates and durations.

Thermal imaging has been used to compare and measure warmup rates and durations of EndoTherm dosed and non-dosed heating systems.

Improving Rheology

The rheology of a liquid refers to the study of its flow and deformation characteristics. It is the science that deals with the behavior of liquids under the influence of applied stresses or strains.

Rheology helps us understand how a liquid responds to changes in its environment, such as temperature, pressure, and shear rate.

Changing the rheology of heating system fluid can improve heat transfer and change pipe system flows.


Nucleate Boiling Enhancements

Nucleate boiling is a type of boiling that occurs when small bubbles of vapor form at nucleation sites on a heated surface. These nucleation sites can be imperfections or irregularities on the surface of the heated material, such as scratches or pits. As the heat is transferred to the liquid, pockets of vapor form at these nucleation sites, which grow and rise to the surface of the liquid as bubbles.

Creating smaller bubbles with a more frequent departure from internal surfaces enhances surface mixing and therefore heat transfer.

Surface Affinity

Liquid surface affinity, also known as surface wetting, refers to the degree to which a liquid spreads out or adheres to a surface.

It is determined by the balance between the adhesive forces between the liquid and the surface, and the cohesive forces between the liquid molecules.

EndoTherm molecules can be better thermally coupled with surfaces than water alone.

Better thermal coupling improves heat transfer and efficiency.

Temperature Dependent Bi-phasic Behaviour

Liquid temperature-dependent bi-phasic behavior is observed in some liquids where their physical properties change abruptly with temperature, leading to the formation of two distinct phases at a critical point.

At temperatures below the critical point, the liquid behaves uniformly as a single phase. However, above or below this temperature, the liquid separates into two phases with different physical properties such as density and viscosity.

This influences turbidity and rheology. Careful additive design can make use of such critical points to deliver optimised properties at specific temperatures.

More details on the scientific effects revealed by our testing can be seen on the Independent Testing page.

As a company, Endo Enterprises (UK) are committed to continue the development of the product, our scientific understanding of the product and the development of new applications in different environments including heat pumps, cooling and other thermal applications.

EndoTherm is produced and manufactured in the UK & US and has been installed in thousands of commercial and domestic applications worldwide.

Independent Testing

EndoTherm has been extensively tested for performance, corrosion and longevity by a number of leading independent R&D facilities.