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Research Papers: Evaporation, Boiling, and Condensation

# Subcooled Boiling Heat Transfer for Turbulent Flow of Water in a Short Vertical Tube

[+] Author and Article Information
Koichi Hata1

Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japanhata@iae.kyoto-u.ac.jp

Suguru Masuzaki

National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan

1

Corresponding author.

J. Heat Transfer 132(1), 011501 (Oct 30, 2009) (11 pages) doi:10.1115/1.3194768 History: Received December 09, 2008; Revised June 06, 2009; Published October 30, 2009

## Abstract

The subcooled boiling heat transfer and the critical heat flux (CHF) due to exponentially increasing heat inputs with various periods ($Q=Q0 exp(t/τ)$, $τ=22.52 ms–26.31 s$) were systematically measured by an experimental water loop flow and observed by an infrared thermal imaging camera. Measurements were made on a 3 mm inner diameter, a 66.5 mm heated length, and a 0.5 mm thickness of platinum test tube, which was divided into three sections (upper, mid, and lower positions). The axial variations of the inner surface temperature, the heat flux, and the heat transfer coefficient from nonboiling to critical heat flux were clarified. The results were compared with other correlations for the subcooled boiling heat transfer and authors’ transient CHF correlations. The influence of exponential period $(τ)$ and flow velocity on the subcooled boiling heat transfer and the CHF was investigated and the predictable correlation of the subcooled boiling heat transfer for turbulent flow of water in a short vertical tube was derived based on the experimental data. In this work, the correlation gave 15% difference for subcooled boiling heat transfer coefficients. Most of the CHF data (101 points) were within 15% and −30 to $+20%$ differences of the authors’ transient CHF correlations against inlet and outlet subcoolings, respectively.

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## Figures

Figure 1

Schematic diagram of experimental water loop

Figure 2

Vertical cross-sectional view of 3 mm inner diameter test section

Figure 3

Result of SEM photograph of platinum test tube

Figure 4

Measurement and data processing system

Figure 5

Typical time variations in measured heat input per unit volume, Q, average temperature, T¯, calculated heat flux, q, and inner surface temperature, T¯s, on the platinum test tube of d=3 mm and L=66.5 mm for the exponential period of 7.52 s, with the flow velocity of 4.0 m/s

Figure 6

Typical heat transfer processes on the platinum test tube of d=3 mm and L=66.5 mm for the exponential period of around 8 s with the flow velocities of 4.0 m/s, 6.9 m/s, 9.9 m/s, and 13.3 m/s

Figure 7

Inner surface temperatures, heat fluxes, and heat transfer coefficients for first, second, and third positions of three sections, and inlet and outlet liquid temperatures with the exponential period of 8 s at the flow velocity of 13.3 m/s

Figure 8

Inner temperatures of platinum test tube at the critical heat fluxes of 15.1 MW/m2, 21.2 MW/m2, and 28.3 MW/m2 for the exponential periods of 7.5 s, 77.6 ms, and 7.9 s with the flow velocities of 4 m/s, 4 m/s, and 13.3 m/s, respectively

Figure 9

Axial variations in outer surface temperature of the test tube observed by an infrared thermal imaging camera for the exponential period of 7.9 s, with the flow velocity of 13.3 m/s

Figure 10

Time variations in measured heat input per unit volume, Q, average temperature, T¯, calculated heat flux, q, and inner surface temperature, T¯s, on the platinum test tube of d=3 mm and L=66.5 mm for the exponential period of 77.57 ms with the flow velocity of 4.0 m/s

Figure 11

Typical heat transfer processes on the platinum test tube of d=3 mm and L=66.5 mm for the exponential periods of 26 ms, 78 ms, and 759 ms, and 7.5 s with the flow velocity of 4.0 m/s

Figure 12

Inner surface temperatures, heat fluxes, and heat transfer coefficients for first, second, and third positions of three sections, and inlet and outlet liquid temperatures with the exponential period of 77.6 ms at the flow velocity of 4 m/s

Figure 13

The qcr,sub on the platinum test tube of d=3 mm and L=66.5 mm, with the commercial finish of inner surface at ΔTsub,in=150 K for τ=22.52 ms–26.31 s

Figure 14

Ratios of qcr,sub for the platinum test tube of d=3 mm and L=66.5 mm, with the commercial finish of inner surface (101 points) to corresponding values calculated by Eq. 1 versus ωpu/{σ/g/(ρl−ρg)}0.5

Figure 15

Ratios of qcr,sub for the platinum test tube of d=3 mm and L=66.5 mm, with the commercial finish of inner surface (101 points) to corresponding values calculated by Eq. 2 versus ωpu/{σ/g/(ρl−ρg)}0.5

Figure 16

Time variations in Pipt, Popt, Pin, Pout, q, and T¯s for Pout=933 kPa, ΔTsub,out=63.13 K, and u=4 m/s

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