Experimental and numerical studies on the flow and heat transfer characteristics of low heat flux natural circulation under the rolling condition were conducted in this paper.
The flow loop applied in the experiment is fixed on a rolling platform and the test fluid is deionized water. The testing channel made of stainless steel is narrow rectangular with the cross section of 2×40 mm2 and the heat length is 1100 mm. Enough experimental data points are obtained for a system pressure range of 0.1–0.3 MPa and an inlet temperature range of 50°C∼80°C. The testing channel is heated by electric, and the heat flux is less than 60 kW/m2. The rolling platform is driven by the crank rocker mechanism, and the rolling angle of the experimental loop varies with sine function. Driven by low pressure head, the low heat flux natural circulation has a negative flow value in the trough because of the effect of additional pressure drop under rolling condition. The experimental results show that the temperature fluctuation of the coolant is more severe because of intermittent reverse of the flow, and the parameter of outlet water will turn high under the effect of repeated heating. At the same time the amplitude of the temperature fluctuation in the outlet and inlet increase sharply compared with the condition that the flow doesn’t reverse. Under this condition the temperature of water increases as the additional inertia force raises because the level of flow reverse is improved and the working fluid is heated for more than once.
The heat transfer of low power natural circulation under rolling condition is discussed in this paper. The analysis finds that the rolling condition doesn’t strengthen the heat transfer absolutely when the heat power is low. The average heat transfer coefficients of the natural circulation under rolling conditions increase faster than those under steady state when strengthening the power of heat. Considering the flow will reverse periodically, the reason why the heat transfer is weakened at low power condition is given.