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Study of Flow and Heat Transfer Characteristics under Flow Fluctuation Condition

Author: WangChang
Tutor: GaoZuoZhen
School: Harbin Engineering University
Course: Nuclear Energy Science and Engineering
Keywords: Flow fluctuate Flow characteristic Heat transfer characteristic
CLC: TK124
Type: Master's thesis
Year: 2010
Downloads: 43
Quote: 0
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Abstract


Experimental research and theoretical analysis on flow and heat transfer characteristics under flow fluctuation periodic condition are carried out. The experiment is concentrated on turbulent fluctuation flow. Using de-ionized water as the working fluid in a vertical heated pipe with constant heat flux, the fluctuating period, amplitude and average flow rate are changed to investigate the effect of all the parameters on flow and heat transfer characteristics.The experimental results show that when the flow rate fluctuates periodically, the pressure drop and the velocity change with the same period except for a phase difference. This phase lag changes with the cycle-average flow rate, but the fluctuation period and amplitude produce no effect on the phase lag. The difference of instantaneous friction factor between the acceleration phase and deceleration phase has been studied and an empirical equation is obtained for the cycle-average friction factor as a function of dimensionless fluctuation frequency, amplitude and cycle-average Reynolds number. For heat transfer characteristic under fluctuation condition, with the increase of fluctuation period, the heat transfer is decreased when Reta<10000 and is enhanced when Reta>10000, respectively. With the relative fluctuation amplitude increases, the heat transfer will decrease. When the fluctuation period is 20s、25s or 30s, the whole of heat transfer is in the decrease condition but has an increase tendency when the Reynolds number increases, the heat transfer does not change linearly with the change of Reynolds number when the fluctuation period is 10s and 15s. In addition, the turbulent bursting model is used to analyze the heat transfer.The theoretical analysis is directed mainly at the laminar fluctuation flow, the mathematic model for flow and heat transfer characteristics in fully developed fluctuation laminar flow was built based on the N-S equation with rationally hypothesis. The fluctuation flow is treated as a composition of oscillation flow on a steady flow, and special stress is laid on analyzing the effect of oscillation flow parameters on flow and heat transfer.

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Thermal Engineering Theory > Heat Transfer
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