In-situ thermal transport measurement of flowing fluid using modulated photothermal radiometry

Journal Article · Sat Jul 31 00:00:00 EDT 2021 · International Journal of Heat and Mass Transfer

DOI:https://doi.org/10.1016/j.ijheatmasstransfer.2021.121767· OSTI ID:1977188

Zeng, Jian ^[1]; Chung, Ka Man ^[1]; Adapa, Sarath Reddy ^[1]; Feng, Tianshi ^[1]; Chen, Renkun ^[1]

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1. Univ. of California, San Diego, CA (United States)

In situ thermal transport measurement of flowing fluid could be useful for the characterization and diagnosis of practical thermal systems such as fluid heat exchangers and thermal energy storage systems. Despite abundant reports on the ex-situ thermal conductivity measurement of stagnant fluids, a suitable technique for the thermal conductivity measurement of flowing fluid has been rarely reported. Here, this paper presents the thermal conductivity measurement of flowing fluid within a pipe using a non-contact modulated photothermal radiometry (MPR) technique, where the surface of the pipe is heated by an intensity-modulated laser and the heat diffuses into the fluid with suitable modulation frequency. We design a tube section with small wall thickness suitable for the MPR measurements to maximize the sensitivity of the thermal response to the fluid properties while minimizing the lateral heat spreading effect. Intrinsic thermal conductivity of different fluids was obtained within a proper range of frequency and flow velocity where the forced convection effect is negligible. The forced convection effect became prominent at high flowing velocity and at low modulation frequency, leading to higher effective thermal conductivity of the fluid. It is found that the intrinsic thermal conductivity could be obtained when the flow velocity is less than 100 mm/sec and Re_D^1/2Pr^1/3 < 100 for DI water and Xceltherm oil under the specified experimental conditions, where Re_D is the Reynolds number and Pr is the Prandtl number.

• Research Organization: Univ. of California, San Diego, CA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: EE0008379
• OSTI ID: 1977188
• Alternate ID(s): OSTI ID: 1815142
• Journal Information: International Journal of Heat and Mass Transfer, Vol. 180, Issue C; ISSN 0017-9310
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
photothermal radiometry
thermal conductivity
flowing fluid
in-situ measurement
convection heat transfer