ASTM D7896-19,Standard Test Method for Thermal Conductivity, Thermal Diffusivity, and Volumetric Heat Capacity of Engine Coolants and Related Fluids by Transient Hot Wire Liquid Thermal Conductivity Method.ASTM D7896-19 pdf free download.
ASTM D7896-19 covers the use of a transient hot wire liquid thermal conductivity method and associated equipment (the System) for the determination of thermal conductivity, thermal diffusivity and volumetric heat capacity of aqueous engine coolants, non-aqueous engine coolants, and related fluids. The System is intended for use in a laboratory.
This test method excludes fluids that react with platinum.
This test method requires a sample of approximately 40 mL.
4. Summary of Test Method
4.I A fluid to be tested is placed inside the sampling cel assembly that is part of the system apparatus. The temperature within the sampling cell assembly is regulated by the use of a temperature control peripheral. Regardless of the test temperature, the sample and the System sensor are allowed to equilibrate to approximately the same temperature. The sam pling cell assembly may be pressurized by up to a gauge pressure of 241 kPa(35 psig).The sensor, a thin platinum wire. is immersed in the liquid test sample. A current is introduced into the wire over the short test time of 0.8s that heats both the wire and the liquid sample. The temperature of the wire and the resistance of the wire decay rapidly once the current is removed. The resistance of the wire is measured with respect to time and a temperature versus time profile for the liquid sample is created. From the temperature versus time profile, the thermal conductivity and thermal diffusivity of the liquid.
7 Speciman and Test Preparations
7.1 The sampling cell must be clean and dry before the liquid to be tested is introduced into it.
7.2 If the liquid to be tested is aqueous and dilutions are required, follow the procedures of Practice D1176 for proper sample preparation.
7.3 If the liquid to be tested is non-aqueous,the liquid specimen is tested directly, without any changes or dilutions Shake or stir the liquid to assure that it is homogeneous.
7.4 If the liquid to be tested is non-aqueous, it should be assumed to be hygroscopic and its exposure to ambient air should be as brief as possible.
8.1 An ambient temperature measurement should be made prior to proceeding with actual sample measurements. Once complete the controller is balanced and ready for use.
8.2 When testing at other than ambient temperature, follow the instructions in the operating manual provided with the temperature control equipment.
8.3 Perform ten repetitive measurements of the thermal properties of the test specimen.
8.3.1 Set the measurement temperature and specify ten thermal property measurements to be made at that temperature.