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The Transient Hot Wire Liquid Thermal Conductivity Meter (THW-L1) is a precision analytical instrument for directly measuring the thermal conductivity of liquids and low viscosity pastes, from (THW-L1) -50 °C / 10 °C to 200 °C and (THW-L1E) -50 °C to 300 °C.
The Thermtest Transient Hot Wire (THW-L1) Liquid Thermal Conductivity Meter is an advanced measurement system for direct determination of the thermal conductivity liquids and pastes in accordance with ASTM D7896-19 – Standard Test Method for Thermal Conductivity of Engine Coolants and Related Fluids by Transient Hot Wire Liquid Thermal Conductivity Method.
The THW-L1 Meter was designed with speed and operational simplicity in mind. With a single measurement of 1 second in duration, small volumes of liquids and low viscosity pastes can be accurately and precisely measured for thermal conductivity, thermal diffusivity and specific heat. The THW-L1 Meter uses a non-stationary measurement approach and rapid test times limiting convective effects for samples with a wide range of viscosities (0.1 to 10,000,000 mPas).
The Engine oil Castrol Edge SAE 5W-30 measured with the THW-L1 device from 5 °C to 195 °C without any back pressure applied to the fluid. Three tests performed at each temperature step and the repeatability was better than 1 %.
In Figure 2, the Engine oil samples can be seen. The left vial is a fresh sample, vial in the middle is after a full temperature run, and the right vial is a sample of used oil from a car engine after 6,000 km.
Tables 1-3 show the thermal conductivity, thermal diffusivity and volumetric specific heat of both the fresh and the used oil samples, while these data are plotted in Figures 2-4.
It was noticed the thermal conductivity of the used oil is around 2 % lower than the thermal conductivity of the fresh oil sample, while the thermal diffusivity and the volumetric specific heat of the used oil sample was around 1 % lower than the properties of the fresh oil sample. The decrease in repeatability above 170°C is due to a little movement of the liquid and could be improved with use of back-pressure.
Table 1. Thermal Conductivity Measurements of the Fresh and the Used Engine Oil.
T (°C) | λ (W/m·K) Fresh |
λ (W/m·K) Used |
5.1 | 0.139 | 0.136 |
10.0 | 0.138 | 0.135 |
14.9 | 0.137 | 0.135 |
19.8 | 0.137 | 0.134 |
24.6 | 0.136 | 0.133 |
29.5 | 0.136 | 0.133 |
34.4 | 0.135 | 0.132 |
39.3 | 0.135 | 0.132 |
44.2 | 0.134 | 0.131 |
49.2 | 0.133 | 0.131 |
54.1 | 0.133 | 0.130 |
59.1 | 0.132 | 0.130 |
64.0 | 0.131 | 0.129 |
69.9 | 0.131 | 0.128 |
74.9 | 0.130 | 0.127 |
79.8 | 0.129 | 0.127 |
84.7 | 0.129 | 0.126 |
89.6 | 0.128 | 0.126 |
94.5 | 0.127 | 0.125 |
99.5 | 0.127 | 0.125 |
T (°C) | λ (W/m·K) Fresh |
λ (W/m·K) Used |
104.4 | 0.126 | 0.124 |
109.3 | 0.125 | 0.123 |
114.2 | 0.125 | 0.123 |
119.1 | 0.124 | 0.122 |
124.0 | 0.124 | 0.122 |
129.9 | 0.122 | 0.121 |
134.9 | 0.122 | 0.121 |
139.8 | 0.121 | 0.120 |
144.8 | 0.121 | 0.119 |
149.7 | 0.121 | 0.119 |
154.7 | 0.120 | 0.119 |
159.7 | 0.119 | 0.119 |
164.7 | 0.119 | 0.117 |
169.7 | 0.119 | 0.117 |
174.7 | 0.118 | 0.117 |
179.7 | 0.120 | 0.118 |
184.8 | 0.118 | 0.118 |
189.7 | 0.120 | 0.117 |
194.6 | 0.120 | 0.116 |
Table 2. Thermal Diffusivity Measurements of the Fresh and the Used Engine Oil.
T (°C) | α (mm2/s) Fresh |
α (mm2/s) Used |
5.1 | 0.077 | 0.076 |
10.0 | 0.077 | 0.076 |
14.9 | 0.076 | 0.075 |
19.8 | 0.075 | 0.075 |
24.6 | 0.075 | 0.074 |
29.5 | 0.074 | 0.073 |
34.4 | 0.073 | 0.073 |
39.3 | 0.073 | 0.072 |
44.2 | 0.072 | 0.071 |
49.2 | 0.072 | 0.070 |
54.1 | 0.071 | 0.070 |
59.1 | 0.070 | 0.070 |
64.0 | 0.070 | 0.069 |
69.9 | 0.069 | 0.069 |
74.9 | 0.068 | 0.068 |
79.8 | 0.067 | 0.067 |
84.7 | 0.067 | 0.067 |
89.6 | 0.066 | 0.066 |
94.5 | 0.065 | 0.065 |
99.5 | 0.065 | 0.065 |
T (°C) | α (mm2/s) Fresh |
α (mm2/s) Used |
104.4 | 0.064 | 0.064 |
109.3 | 0.064 | 0.063 |
114.2 | 0.063 | 0.063 |
119.1 | 0.062 | 0.062 |
124.0 | 0.062 | 0.061 |
129.9 | 0.061 | 0.061 |
134.9 | 0.060 | 0.060 |
139.8 | 0.060 | 0.059 |
144.8 | 0.059 | 0.059 |
149.7 | 0.059 | 0.059 |
154.7 | 0.059 | 0.058 |
159.7 | 0.058 | 0.057 |
164.7 | 0.058 | 0.056 |
69.9 | 0.069 | 0.069 |
74.9 | 0.068 | 0.068 |
169.7 | 0.056 | 0.056 |
174.7 | 0.056 | 0.055 |
179.7 | 0.057 | 0.055 |
184.8 | 0.055 | 0.055 |
189.7 | 0.056 | 0.054 |
194.6 | 0.055 | 0.053 |
Table 3. Calculated Volumetric Specific Heat of the Fresh and the Used Engine Oil.
T (°C) | vCp (MJ/m3.K) Fresh |
vCp (MJ/m3.K) Used |
5.1 | 1.795 | 1.778 |
10.0 | 1.803 | 1.783 |
14.9 | 1.804 | 1.795 |
19.8 | 1.818 | 1.797 |
24.6 | 1.819 | 1.804 |
29.5 | 1.834 | 1.815 |
34.4 | 1.837 | 1.824 |
39.3 | 1.845 | 1.837 |
44.2 | 1.853 | 1.840 |
49.2 | 1.860 | 1.854 |
54.1 | 1.871 | 1.852 |
59.1 | 1.881 | 1.866 |
64.0 | 1.880 | 1.876 |
69.9 | 1.899 | 1.872 |
74.9 | 1.905 | 1.879 |
79.8 | 1.916 | 1.886 |
84.7 | 1.923 | 1.894 |
89.6 | 1.932 | 1.908 |
94.5 | 1.943 | 1.913 |
99.5 | 1.951 | 1.932 |
T (°C) | vCp (MJ/m3.K) Fresh |
vCp (MJ/m3.K) Used |
104.4 | 1.959 | 1.940 |
109.3 | 1.968 | 1.947 |
114.2 | 1.989 | 1.959 |
119.1 | 1.993 | 1.965 |
124.0 | 1.997 | 1.981 |
129.9 | 2.002 | 1.988 |
134.9 | 2.030 | 1.999 |
139.8 | 2.022 | 2.019 |
144.8 | 2.040 | 2.027 |
149.7 | 2.035 | 2.040 |
154.7 | 2.046 | 2.048 |
159.7 | 2.069 | 2.082 |
164.7 | 2.071 | 2.089 |
169.7 | 2.107 | 2.090 |
174.7 | 2.109 | 2.128 |
179.7 | 2.109 | 2.130 |
184.8 | 2.148 | 2.149 |
189.7 | 2.138 | 2.163 |
194.6 | 2.173 | 2.186 |