Q & A with Dr. Bergemann
Dr. Marco Bergemann, head of sales and marketing, answers some of the most common questions about thermal transfer fluids.
Dr. Bergemann: A refrigerant is a product that changes phase from liquid to gas to remove heat energy and cool the environment. That’s how it refrigerates. Natural refrigerants include ammonia, carbon dioxide, water, and hydrocarbons. These substances occur in nature. In contrast, chlorine and hydrofluorocarbons are artificial refrigerants.
Cooling brine is another somewhat older term for coolant. A traditional cooling brine is a water-based sodium chloride solution. Cooling brines are thus nothing more than water-based salt solutions. Due to their ability to be chilled far below the freezing point of water, they are used to cool equipment.
Coolants and heat transfer fluids, from a purely physical standpoint, are both doing the same thing—they’re transporting heat energy. Depending on whether the goal is to increase or decrease temperatures at a specific location, we call them either a coolant or a heat transfer fluid. They serve to move heat or cold (the absence of heat) from one place to another. But they don’t generate any heat themselves.
Dr. Bergemann: Typical filling mistakes include using the wrong product, using the wrong concentration, and mixing one product with another.
Dr. Bergemann: Products that are based on different fluids such as ethylene glycol and propylene glycol should not be mixed. That’s not because of any physical or chemical reasons. The problem is, once you’ve mixed the two, you are no longer able to easily calculate anti-freeze or cooling properties. Corrosion inhibitors and stabilizers that are not compatible with one another should also not be mixed because this can lead to corrosion. Using different corrosion inhibitors does not result in the substances complementing one another because they are based on different technologies.
Dr. Bergemann: Concentrates are never filled in concentrated form. These products are ordered purely for logistical reasons. This way, the customer saves on freight and storage costs. But then they also have to invest more time and effort, and they bear the responsibility for ensuring that the proper concentrations are achieved. For operations that don’t have that capability, pre-mixed products are the answer.
Dr. Bergemann: Nearly all TYFO concentrates can be mixed with clean drinking water if the following requirements are met:
- The concentration of chloride ions cannot exceed 100 ppm
- The water hardness must not exceed 40 degrees of general hardness (°GH)
Water hardness can vary internationally. The water hardness stabilizers contained in TYFO concentrates can form complexes with hardening constituents to prevent the formation of limescale up to exactly this degree of water hardness.
Only TYFOCOR® LS should not be mixed with other heat transfer fluids or diluted with drinking water because of its special formulation, which does not include any water hardness stabilizers.
Dr. Bergemann: The color is used for identification. It allows the user to distinguish one product from another so they can avoid unintentional mixing.
Dr. Bergemann: If you exceed the recommended concentration, the freezing point can drop, the heat transfer performance gets worse, the viscosity increases, and the thermal capacity of the liquid decreases.
If you go below the minimum concentration, antifreeze properties and corrosion protection will no longer be sufficient. Bacterial contamination can also occur.
Dr. Bergemann: Bacteria require warmth, nutrients, and a non-toxic environment to grow. These conditions exist when the liquid contains less than 20 percent concentrate. Glycols in general can serve as a nutrient source for bacteria at concentrations below 20 percent.
Dr. Bergemann: You can identify low-quality coolants and heat transfer fluids by the fact that the concentration is not high enough or they do not contain enough corrosion inhibitors and stabilizers. Poor products have practically no inhibitors. These problems are easy to identify in the laboratory.
Dr. Bergemann: Corrosion inhibitors are additives that prevent or slow the corrosion of materials. They are present in heat transfer fluids in low concentrations and they ensure that materials such as metals and polymers do not corrode or age—metals keep their shine; plastics don’t become porous or develop cracks. Depending on the metals and materials you want to protect, specific bundles of corrosion inhibitors need to be used.
Dr. Bergemann: Corrosion inhibitors work best in a slightly alkaline environment (around pH 8). The thermal degradation of heat transfer media is often characterized by the occurrence of acidic components. These acidic components shift the pH value into the neutral or slightly acidic range. This, in turn, drastically reduces the effectiveness of corrosion inhibitors. That’s why buffering agents are added to heat transfer fluids. These buffering agents can deal with a certain quantity of acidic components without a noticeable change in the pH value.
Dr. Bergemann: Reserve alkalinity is a value that describes a fluid’s capacity to compensate for acidic components. To measure reserve alkalinity, hydrochloric acid is added to the product up to a specified pH value. The more acid the product can handle, the better. This is an indication of how much acid the fluid can compensate for by itself. A high alkaline reserve indicates good inhibition and a high-quality thermal transfer fluid. Lower-quality products often only have an alkaline reserve of 0.5 mL of hydrochloric acid. Most TYFOCOR products can handle well over 10 ml.
Dr. Bergemann: Inadequate inhibition happens when the heat transfer fluid does not contain enough corrosion inhibitors. The relationship of corrosion inhibitor concentration to corrosion protection is non-linear. If the quantity of inhibitors is not sufficient, corrosion protection suffers. But corrosion can also result when concentrations of corrosion inhibitors are too high. A product with a very small quantity of added corrosion inhibitors can exhibit lower corrosion protection than one without any inhibitors at all.
Dr. Bergemann: Heat transfer fluid should be replaced when its pH value drops below 7. That’s an indication that the reserve alkalinity has been used up and the corrosion inhibitors have degraded. If the freezing point has shifted or you can see the liquid is damaged because it is discolored or exhibits clouding, it should also be replaced.
Dr. Bergemann: There are two ways to determine the amount of antifreeze contained in a known thermal transfer medium.
- By measuring the refractive index with a refractometer. TYFOROP supplies refractometers with scales that have been specially designed for the TYFO range of products.
- With density measurements to determine the correlation between density and freezing point. The density correlates with the amount of anti-freeze.
Dr. Bergemann: The refractive index, also known as the index of refraction or optical density, is an optical property of a material. This non-dimensional physical property tells us by what factor the wavelength and the phase velocity of light are smaller inside the substance than they would be in a vacuum. The refractive index depends on the wavelength of light, which is why it has been standardized on what is known as the sodium D line (589 nm).
Dr. Bergemann: The pH value is a good way to get an overall impression of the condition a heat transfer fluid is in. The thermal degradation of heat transfer media is often characterized by acidic components being created. These acidic components shift the pH value into the neutral or slightly acidic range. That, in turn, drastically reduces the effectiveness of the corrosion inhibitors. The heat transfer fluid should be replaced when the pH value drops below 7.
Dr. Bergemann: Zink dissolves when it comes into contact with glycols. Components with a high percentage of galvanized steel pipes are therefore not appropriate for coolant and heat transfer systems.
Dr. Bergemann: Heat transfer fluids, if they are sealed and stored in a dry, dark place, can be kept for at least three years.
Dr. Bergemann: TYFOROP offers its customers free analytical fluid testing of heat transfer fluids.
- The status of the existing fluid is tested. In this case we assess to what extent the liquid still fulfills the requirements for protection against freezing and corrosion and long-term stability to determine whether replacement is necessary.
- We analyze the reliability of systems and conduct testing to determine whether corrosion has taken place and, if so, what type of corrosion. For older systems with unknown thermal fluids, we determine the composition and suggest an appropriate alternative for refilling. If the system is experiencing leaks or malfunctions, we can use fluid analysis to help troubleshoot the source of the problem. For these types of tests, we normally require a 500-ml sample and provide results within 10 business days, depending on the testing required.
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