考证试题（Textual research questions）.docVIP

考证试题（Textual research questions） 1. fluid is a general term for liquids and gases. These include fluid flow, inertia, compressibility, expansion and viscosity. 2., the quality of the object refers to the amount of matter contained in the object, the object contains more material, the greater its quality, the less material contained, the smaller its quality. 3. when the pressure is constant, the density of the fluid decreases with the increase of the temperature. When the temperature is constant, the density of the fluid increases with the increase of the pressure. 4. the specific volume is the volume of a unit mass. The specific volume of gas is greatly affected by temperature and pressure. When the temperature is constant, the pressure increases and the volume decreases. When the pressure is constant, the temperature increases and the volume increases. 5., the dry saturated steam will continue to be heated by constant pressure, and the steam temperature will rise above the saturation temperature. Such steam is called superheated steam. The temperature of superheated steam is higher than the saturated temperature under the steam pressure. This is called superheat. The heat absorbed by a unit mass during superheated steam is called superheated heat. 6. water hammer means a mixture of steam or soda entering a water at a temperature lower than its saturation temperature, producing a knock and vibration when steam suddenly condenses. 7. on the pipe, because of the rapid closing of the valve or the sudden stop of the water pump, the water flow speed decreases rapidly and the pressure rises sharply. It is called positive water hammer. Because of the rapid opening of the valve and the rapid increase of the flow velocity, the water hammer is called negative water hammer because of the sharp decrease of the pressure in the pipeline. Prevention is: to extend the opening and closing time of the valve, as much as possible to shorten the length of the pipeline, set up safety val