Abstract:
This study examines the unique thermophysical properties of aqueous glycerol solutions with a focus on their application in heating systems. By examining variables such as density, viscosity, thermal conductivity, and specific heat capacity at various glycerol concentrations and temperatures, we offer insight into the potential applications and limitations of Master BIO products in thermal engineering.

Introduction:
Aqueous glycerin solutions are known for their diverse applications, owed largely to their distinct physical properties. This research provides a comprehensive analysis of these properties, particularly in the context of heating systems.

Methodology:
We analyzed glycerin-water mixtures with glycerin concentrations ranging from 10% to 70% by mass, at temperatures between 0°C and 100°C. Data was collected on density, dynamic viscosity, thermal conductivity, and specific heat capacity.

Results:
Freezing and Boiling Points: The freezing point shows a sharp decrease at higher glycerin concentrations, beneficial for low-temperature applications.

Glycerine and water solution – Freezing and Boiling Points

Density and Viscosity: Increasing glycerin concentration leads to higher density and viscosity, impacting flow and heat transfer.

Density of aqueous glycerol solution
The density of a mixture of glycerin and water is given in the table for glycerin concentrations from 10 percent to 70 percent by weight in the temperature range from zero to one hundred degrees Celsius.

Dynamic viscosity of an aqueous glycerol solution

The viscosity of an aqueous solution of glycerin is given in the table in the range of mixture temperatures from zero to one hundred degrees Celsius and glycerin concentration from 10% to 70%. It is noteworthy that adding only 10% (by weight) glycerol to water can increase the dynamic viscosity of the solution by ~30%.

Viscosity of aqueous glycerol solution (content in percent by weight)

Thermal Conductivity: Higher glycerin concentrations result in lower thermal conductivity, suggesting limitations in heat transfer applications.

The thermal conductivity values of an aqueous glycerol solution are shown in the table for a temperature range from 20 to 80 degrees Celsius and glycerol concentration from 10% to 70%. With increasing glycerol concentration, the thermal conductivity of the aqueous solution decreases. With a glycerol content of 50%, the thermal conductivity of the mixture is ~30% less than that of pure water.

Specific Heat Capacity: The capacity decreases with increased glycerin concentration, affecting the energy efficiency of heating systems.

Estimates of the heat capacity of an aqueous glycerol solution are given in the table for temperatures from 20 to 80 degrees Celsius and glycerol concentrations from 10 to 70 percent. With increasing glycerol concentration, the thermal conductivity of the solution decreases. Under normal conditions and a content of 10% glycerol, the heat capacity of the mixture is ~2 times less than the heat capacity of pure water.

Heat capacity of a mixture of glycerin with water (content in percent by weight)

Discussion:

The study highlights the trade-offs between glycerin concentration and thermophysical properties. While higher concentrations offer lower freezing points, they also reduce thermal conductivity and specific heat capacity, potentially limiting efficiency in certain heating applications.

Conclusion:

Aqueous glycerin solutions present a viable option for specialized heating systems, particularly in environments with varying temperatures. However, careful consideration of glycerin concentration is crucial to balance between antifreeze properties and heat transfer efficiency.

Procedure in case of emergency shutdown of the heating system.

Solutions of glycerin and water at zero temperatures and below have a high level of viscosity. Therefore, if the system has cooled down, it is advisable to first turn on the heating elements themselves, and then start circulation. This will reduce the load on the pumps.

© 2024 Sergei Vesselkov. All rights reserved.
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Aqueous solution of propylene glycol – aqueous solution of coolant and antifreeze for heating and cooling systems

Dependence of propylene glycol concentration on the freezing point of aqueous solution (onset of crystallization). Solution density values at 20 ° C.

As the price of electricity has risen significantly, many owners of country houses and cottages are thinking about saving. One possibility is, for example, switching off geothermal heating. However, many are unaware that the system needs to be prepared for this. If the system is filled with heat transfer fluid with a freezing point below -10 ° C, it may freeze during shutdown and cause serious damage.

To avoid this problem, ethylene glycol or propylene glycol concentrate must be added to the system. In this way, it is possible to lower the freezing temperature to -36 ° C, for example, which eliminates freezing and allows the heating system to be restarted without any problems when electricity prices return to normal.

Many are probably at a loss – why did the glass cleaner and its strong odor rise in price in stores! Because on May 9 a directive was adopted, according to which the sale of methanol-based glass cleaning liquid to consumers is prohibited in the EU!

The initiative is Poland, so that people do not get poisoned with methanol liquid. Again they “worried” about the people, now they will buy an expensive, almost harmless product. It turned out to be forbidden – easier than raising the level of awareness and well-being in society.

And what can I say, it is politically more profitable to use Brazilian bioethanol than cheap methanol from its eastern neighbor.

And now how to pay the average consumer, let’s understand. Immediately make a reservation – this is not an advertising article, but an informative one. Not advertising because the author of the article produces all types of glass cleaning liquid and which one the client chooses can be sold as well. We have been manufacturing glass cleaning fluid for 25 years and have good knowledge. I have identified the main points by which we consider all the advantages and disadvantages of a liquid, depending on the type of alcohol.

The main alcohols are ethanol, methanol (wood alcohol) and isopropyl alcohol. We do not consider the latter, since in the European market it occupies about 1% of the total liquid. Compare non-freezing based on methanol and ethanol.

1. Smell

Deliberately put this item in first place, based on what is important to the client.

The concept of smell is also considered by the layman, because even methanol has a “natural” smell of methanol. So, the odorless glass cleaner is based on methanol. With a smell – based on ethanol. A liquid with a lower freezing point will smell stronger (-40 smell is stronger than -15 because -40 has a higher alcohol content).

Many manufacturers add perfumes – organic compounds that give the smell of apple, lemon, frosty freshness. What they do is clog or smell stronger than alcohol to clog the smell of alcohol. That is, the smell of alcohol does not disappear, and we breathe in additional chemistry. Everyone decides whether to inhale it (in our allergic age).

To summarize – the smell leader – methanol liquid.

2. Toxic / harmful.

Methanol is a poison. Even a small amount if swallowed can cause death. Contact with eyes is also harmful. Most importantly, keep out of the reach of children. And best of all, enter a habit – open the canister and completely pour it into the tank.

Ethanol-based windshield wipers are also prohibited. The ethanol used is all denatured – with ketones, isopropyl and bitrex, which gives bitterness.

3. Cost.

Methanol is about 2 times cheaper than ethanol. As a result, ethanol-based fluid is more expensive.

4. Detergent properties.

In addition to surfactants (surfactants), the non-freezing properties of detergents depend on alcohol. And here methanol liquid wins again – menalol is better at washing glass and treats rubber wipers more carefully.

5. Alcohol concentration and economy when diluting the wiper.

I will scatter another myth. Suppose you bought a wiper with a freezing point of -40C. Outside the window there is no such frost and you dilute the -40 wiper with water in a proportion of 50/50. Now the freezing temperature is -20? – Not! – if on the basis of ethanol, then -15, if on the basis of methanol -18! The dependence of the freezing temperature / content of the sprint is not direct. And in order to produce -21 freezing point, it is necessary to use ethanol more than methanol – with the same -21 degrees. At this point, methanol liquid wins.