Temperature-aware time-varying convection over a duty cycle for a given system thermal-topology

Fakoor-Pakdaman, M.; Ahmadi, Mehran; Bahrami, Majid

doi:10.1016/j.ijheatmasstransfer.2015.04.011

Cited by 9 publications

(3 citation statements)

References 21 publications

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“…Taking the aforementioned heat conduction contribution in the transient turbulent heat transfer process into consideration, it is reasonable to assume that the transient turbulent heat transfer characteristics could be described by introducing the non-denmensional time, Fo. As stated earlier, Fakoor-Pakdman [7,8] employed Fo to analyse the transient laminar forced convection heat transfer inside a circular tube under time-dependent heat flux. Kakaç [9] also numerically analyzed transient heat transfer for turbulent flow using Fo.…”

Section: Transient Nusselt Numbermentioning

confidence: 99%

“…The results demonstrated that the slug assumption did reveal the essential physical behavior of the systems considered, although the numerical results were somewhat in error. Fakoor-Pakdaman et al [7,8] analytically and experimentally studied the transient laminar forced convection heat transfer inside a circular tube under time-dependent heat flux. They expressed the transient Nusselt number as a function of dimensionless space and time.…”

Section: Introductionmentioning

confidence: 99%

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Transient heat transfer due to exponentially increasing heat inputs for turbulent flow of FC-72 in small diameter tubes

Fukuda

Liu

2017

International Journal of Heat and Mass Transfer

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The transient heat transfer process due to exponentially increasing heat inputs for turbulent flow of FC-72 was schematically investigated for different combinations of parameters such as flow velocity, inlet liquid temperature and period of exponentially increasing heat inputs. The ranges of Reynolds number, Red, and Prandtl number, Pr, were 23,400 to 81,800 and 8.4 to 10.8, respectively. The test heaters used in this study were circular SUS304 tubes with small inner diameters of 1, 1.8 and 2.8 mm, wall thickness of 0.5 mm, and heated lengths around 30, 40 and 50 mm. The effects of flow velocity, exponential period and tube inner diameter on transient turbulent heat transfer process were discussed in detail. It was clarified that the transient turbulent heat transfer due to exponentially increasing heat inputs could be analyzed by introducing a dimensionless time, Fourier number, Fo. An empirical correlation for transient turbulent heat transfer caused by exponentially increasing heat inputs on small diameter tubes was developed based on the effects of Fo, flow velocity and tube inner diameter. The empirical correlation presents the experimental data within ±25%.

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Section: Transient Nusselt Numbermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transient heat transfer due to exponentially increasing heat inputs for turbulent flow of FC-72 in small diameter tubes

Fukuda

Liu

2017

International Journal of Heat and Mass Transfer

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“…Knowledge of transient forced convection heat transfer of water is important for the design of cooling devices such as the divertor of fusion reactors and hybrid/electric/ fuel cell vehicles [1,2]. For fusion reactors, there is high heat flux at the divertor on plasma disruption.…”

Section: Introductionmentioning

confidence: 99%

Steady and transient forced convection heat transfer for water flowing in small tubes with exponentially increasing heat inputs

et al. 2016

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d Inner diameter of the test tube (m) d h Hydraulic diameter Fo = aτ/d 2 , Fourier number h Heat transfer coefficient (W/m 2 K) I Current flowing through a standard resistance (A) L Heated length (m) L e Entrance length (m) Nu d Nusselt number P Pressure (kPa) P in Pressure at inlet of heated section (kPa) P ipt Pressure measured by inlet pressure transducer (kPa) P out Pressure at outlet of heated section (kPa) P opt Pressure measured by inlet pressure transducer (kPa) Pr = c p μ/λ, Prandtl numbeṙ Q Heat input per unit volume (W/m 3 ) Q 0 Initial exponential heat input (W/m 3 ) q Heat flux (W/m 3Confidence level (-) ΔT L = (T s − T L ), temperature difference between heater inner surface temperature and average bulk liquid temperature (K)Abstract Steady and transient heat transfer coefficients for water flowing in small tubes with exponentially increasing heat inputs were measured. Platinum tubes with inner diameters of 1.0 and 2.0 mm were used as test tubes, which were mounted vertically in the experimental water loop. In the experiment, the upward flow velocity ranged from 2 to 16 m/s, and the corresponding Reynolds numbers ranged from 4.77 × 10 3 to 9.16 × 10 4 at the inlet liquid temperatures ranged from 298 to 343 K. The heat generation rate exponentially increased with the function. The period of the heat generation rate ranged from 24 ms to 17.5 s.Experimental results indicate that steady heat transfer coefficients decreased with the increase in the inner diameter of the small tube. Moreover, the ratio of bulk viscosity to near-wall viscosity of water increased with the rise in surface temperature of the vertical tube. From the experimental data, correlations of steady-state heat transfer for inner diameters of 1.0 and 2.0 mm were obtained. The heat transfer coefficient increased with decreasing the period of the heat generation rate as the flow velocity decreased. Moreover, the Nusselt number under the transient condition was affected by the Fourier number and the Reynolds number. List of symbolsA Surface area (m 2 ) a Thermal diffusivity (m 2 /s) BBasis limit (-) c Specific heat (J/kg K) c p

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Transient forced convection heat transfer for nitrogen gas flowing over plate heater with exponentially increasing heat input

Shibahara

Liu

Fukuda

2016

International Journal of Heat and Mass Transfer

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Temperature-aware time-varying convection over a duty cycle for a given system thermal-topology

Cited by 9 publications

References 21 publications

Transient heat transfer due to exponentially increasing heat inputs for turbulent flow of FC-72 in small diameter tubes

Transient heat transfer due to exponentially increasing heat inputs for turbulent flow of FC-72 in small diameter tubes

Steady and transient forced convection heat transfer for water flowing in small tubes with exponentially increasing heat inputs

Transient forced convection heat transfer for nitrogen gas flowing over plate heater with exponentially increasing heat input

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