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Swiss nuclear power and the case for long-term operation
Designed for 40 years but built to last far longer, Switzerland’s nuclear power plants have all entered long-term operation. Yet age alone says little about safety or performance. Through continuous upgrades, strict regulatory oversight, and extensive aging management, the country’s reactors are being prepared for decades of continued operation, in line with international practice.
Piyush Sabharwall, Vivek Utgikar, Fred Gunnerson
Nuclear Technology | Volume 166 | Number 2 | May 2009 | Pages 197-200
Technical Note | Thermal Hydraulics | doi.org/10.13182/NT09-A7406
Articles are hosted by Taylor and Francis Online.
The effect of the mass flow rate at constant velocity on the convective heat transfer coefficient of an incompressible fluid in a turbulent flow regime is presented with the help of dimensional analysis. The heat transfer coefficient decreases by ~10% with a threefold increase in the mass flow rate under these conditions, based on the commonly used Dittus-Boelter correlation for estimation of the heat transfer coefficient. On the other hand, an increase in the heat transfer coefficient is observed if the area is maintained constant. Doubling the mass flow rate will result in a 92% increase in the heat transfer coefficient. However, there is a concomitant increase in the pressure drop, proportional to the mass flow rate raised to 0.95. The pressure drop is predicted to decrease for the constant velocity case with an inverse dependence on the mass flow rate. The pressure drop considerations may be critical in certain situations (elevation of boiling point in case of a boiling heat transfer medium), and any benefit derived from the higher heat transfer coefficient may be lost because of the higher pressure drop across the heat exchanger in the constant area case.