![]() ![]() Nuclear Systems Volume I: Thermal Hydraulic Fundamentals, Second Edition. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer 4th edition, 1994, ISBN: 978-0412985317 Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 8-1. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983). It must be noted, the change in density is not linear with temperature because the volumetric thermal expansion coefficient for water is not constant over the temperature range. It has a maximum density of 11.6 o C (1106 kg/m 3), whereas its solid form ice density is 1017 kg/m 3. Also, heavy water differs from most liquids in that it becomes less dense as it freezes. Pure heavy water (D 2O) has its highest density of 1106 kg/m 3 at a temperature of 11.6 o C (52.9 o F). The molar mass of water is M(H 2O) = 18.02, and the molar mass of heavy water is M(D 2O) = 20.03 (each deuterium nucleus contains one neutron in contrast to the hydrogen nucleus). Since about 89% of the molecular weight of water comes from the single oxygen atom rather than the two hydrogen atoms, the weight of a heavy water molecule is not substantially different from that of a normal water molecule. The fact causes this difference, and the deuterium nucleus is twice as heavy as the hydrogen nucleus. Pure heavy water (D 2O) has a density about 11% greater than water but is otherwise physically and chemically similar. Due to the different relative power of fuel assemblies in a core, these fuel assemblies have different hydraulic resistance and this may induce local lateral flow of primary coolant and it must be considered in thermal-hydraulic calculations. The pressure loss due to the coolant acceleration in an isolated fuel channel is then: channel outlet flow velocity is equal to 5.69 m/s.channel inlet flow velocity is equal to 5.17 m/s.Pressure loss due to the coolant acceleration in an isolated fuel channel.The flow is reversed up through the core from the bottom of the pressure vessel, where the coolant temperature increases as it passes through the fuel rods and the assemblies formed by them. Inside the reactor pressure vessel (RPV), the coolant first flows down outside the reactor core (through the downcomer). Each loop comprises a steam generator and one main coolant pump. The primary circuit of typical PWRs is divided into 4 independent loops (piping diameter ~ 700mm). The water (coolant) is heated in the reactor core to approximately 325☌ (⍴ ~ 654 kg/m 3) as the water flows through the core. The inlet temperature of the water is about 290☌ (⍴ ~ 720 kg/m 3). At this pressure, water boils at approximately 350☌ (662☏). Pressurized water reactors are cooled and moderated by high-pressure liquid water (e.g., 16MPa). Data do not represent any reactor design. It is an illustrative example, and the following data do not correspond to any reactor design. See also: Fluid Acceleration – Pressure Loss ![]() It differs by about 9% and therefore ice floats on liquid water It has a maximum density of 3.98 ☌ (1000 kg/m 3), whereas the density of ice is 917 kg/m 3. For example, water differs from most liquids in that it becomes less dense as it freezes. It must be noted and there are exceptions to this rule. Where ∆T is the temperature change, V is the original volume, ∆V is the volume change, and α V is the coefficient of volume expansion. The change in volume of a material that undergoes a temperature change is given by the following relation: This phenomenon is known as thermal expansion. However, the amount of expansion or contraction varies, depending on the material. Most substances expand when heated and contract when cooled. The effect of temperature on the densities of liquids and solids is also very important. Compressibility measures the relative volume change of a fluid or solid as a response to a pressure change. On the other hand, the density of gases is strongly affected by pressure. The effect of pressure on the densities of liquids and solids is very small. Increasing the pressure always increases the density of a material. If you remember that the density of water is very close to 1.0 g/ml or 1.0 oz/fluid ounce ("a pint's (16 oz) a pound (16 oz) the world around"), you may notice that if a cup is 236.6 ml, as given, it should weigh 236.6 g, not the 226 g given above.In general, density can be changed by changing either the pressure or the temperature. The fruit has a density of 1.045 g/ml, while the syrup has a density of 1.15 g/ml, so the fruit will float, being less dense. ![]()
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