In this comparative study, we demonstrated the superior oxidation resistance and ‘longer than average’ service life of Relatherm Heat Transfer Fluids compared to seven other competitor industry thermal fluids. We applied the IP48 test method to all samples. This method was used to measure the tendency of the heat transfer fluid samples to oxidize in a simulated oxidative environment. A comparison of the oxidative degradation of each sample was made by comparing the increases in their Kinematic Viscosity and the resultant Total Acid Numbers (TAN). When compared with the common industry fluids, Relatherm Heat Transfer Fluids were found to have the highest resistance to oxidation and the longest fluid life by virtue of their low Total Acid Number and minimal to no viscosity increase.
SAMPLE COLLECTION & PREPARATION
We collected approximately 100ml/3-4 oz. of fourteen common heat transfer fluid products. Seven of those virgin samples were drawn from the inventory of Relatherm Heat Transfer Fluids. They include virgin samples of the following products – Relatherm HT-1, Relatherm HT-2, Relatherm HT-3, Relatherm MT, Relatherm FG-1 and Relatherm FG-2 (Lot# 441838-1/6).
Virgin samples (approximately 100ml/3-4 oz. each) of seven competitor heat transfer fluid products were obtained from end-user inventory and retail distributors. The following heat transfer fluid samples were collected – Sample A, manufactured by a major Canadian lubricant manufacturer based in Ontario (Lot#25532-18); Sample B, manufactured by an Illinois-based heat transfer fluid manufacturer (Lot#351/A/12); Sample C, manufactured by a global chemical manufacturing company headquartered in Michigan (Lot#450001223); Sample D, supplied by an Ontario/New York-based Heat Transfer Fluid supplier (Lot#2019/4488); Sample E, manufactured by a major Pennsylvania-based Heat Transfer Fluid manufacturer (Lot#K/923387); Sample F, supplied by a mid-size Pennsylvania-based Heat Transfer Fluid manufacturer (Lot#11234873) and Sample G, manufactured by a global energy company headquartered in Texas (Lot# EXM-75423).
All the samples were transferred into clearly labeled glass beakers.
Oxidation test vessels were first cleaned by soaking them in concentrated Sulphuric Acid overnight and then washed with tap water and distilled water repeatedly. Afterward, they were dried in a glassware oven operating at 100°C/212OF for at least two hours and then allowed to cool to room temperature before use. Empty test vessels with ground glass heads were then weighed to the nearest 0.1 gm weight.
Approximately 40 ml / 1-2 oz. of each sample was then charged into the empty oxidation test vessels from the labeled glass beakers. Thereafter, we weighed the test vessels containing the virgin samples to the nearest 0.1 gm. We placed the test vessels in an oil bath at 200 ± 0.5 °C/ 392 ± 32°F.
We introduced air supply into the vessels at a flow rate 15 ± 0.25 l/h using a compressor. As soon as the fluid sample reached the test temperature, we adjusted the air flow, and maintained the test conditions for 6 hours ± 10 minutes. Afterward, we removed the oxidation tube from the baths and allowed them to cool to room temperature. We repeated the heating procedure after 12 hours with air flow. After A second 6-hour cycle, we removed the oxidation tubes from bath and then cooled to room temperature.
The heat transfer fluid samples are thereafter tested for oxidative degradation by measuring changes in their Kinematic Viscosity with a Herzog Multi-Range Viscometer (HVM 472) in accordance with ASTM D44512 . The TAN of the samples oxidized in the IP48 test were analyzed in accordance with ASTM D 66413. We utilized acid-base titration method using standardized Potassium Hydroxide (KOH) as titrant. TAN is expressed in mg of KOH required per gm of the sample. Since the heat transfer fluid samples are the non-aqueous type, they were diluted in a mix of Toluene and Isopropyl Alcohol. To obtain the TAN of the samples, we weighed approximately 1 g of heat transfer fluid to nearest 0.1 mg in a 100-mL beaker and added 75 mL of solvent.
The TAN and percentage increases in Kinematic Viscosity of each sample is presented in Table 1.0 below. Relatherm Heat Transfer Fluids had the lowest TAN and percentage increases in viscosity while Sample C was found to have the highest resultant TAN and viscosity increase.
Heat Transfer Fluid
Total Acid Number after Exposure to Air
Percentage Increase in Kinematic Viscosity
|Relatherm HT-1, HT-2. HT-3, MT, FG-1, FG-2||0.2||1%|
Table 1.0: TAN and % Increase in Kinematic Viscosity of Samples Measured after Air Exposure
In this study, we demonstrated the superior oxidation resistance and longer service life of Relatherm Heat Transfer Fluids compared to seven other common industry thermal fluids. By virtue of its low TAN and low viscosity increase, Relatherm Heat Transfer Fluids were found to have the highest resistance to oxidation and the longest fluid life.