First, the phenomenon of cavitation liquid at a certain temperature, reduce the pressure to the temperature of the vaporization pressure, the liquid will produce bubbles. The phenomenon of bubbles is called cavitation. Cavitation bubble generated when flowing to high pressure Department, the volume decreases so as to burst. This phenomenon of bubble disappearing in liquid due to pressure increase is called cavitation collapse. When the pump is in operation, if the localized area of ​​the overcurrent portion (usually somewhere later in the impeller vane inlet) for some reason causes the absolute pressure of the pumped liquid to drop to the liquid vaporization pressure at the current temperature, Began to vaporize, produce a lot of steam, the formation of bubbles, when the liquid containing a lot of bubbles forward through the high-pressure area within the impeller, the bubbles around the high-pressure liquid bubbles so sharply reduced to rupture. At the same time as the bubble is broken and condensed, the liquid particles fill the cavity at a very high speed, causing a very strong water hammer moment at this moment, and striking the metal surface with a high impact frequency with an impact stress of several hundreds to several thousands Atmospheric pressure, the impact frequency of up to tens of thousands of times per second, will be severe wall breakdown. Cavitation in a pump is the process by which bubbles in the pump and rupture of the bubble damage the overcurrent component. Pump cavitation in addition to the over-current components will have a damaging effect, but also produce noise and vibration, and lead to the decline in the performance of the pump, serious pump liquid will be interrupted, can not work properly. Second, the basic relationship between pump cavitation Pump cavitation conditions are caused by the pump itself and the inhalation device determined in two ways. Therefore, to study the conditions of cavitation should be considered both on the pump itself and the inhalation device, the basic equation for the pump cavitation NPSHc ≤ NPSHr ≤ [NPSH] ≤ NPSHa NPSHa = NPSHr (NPSHc) - pump start cavitation NPSHa NPSHa > NPSHr (NPSHc) - No Cavitation in Pumps NPSHa - Equivalent NPSHa, also known as effective NPSH, is more difficult to cavitate; NPSHr - NPSHr, also known as required cavitation NPSHc - Critical NPSH, which is the NPSH corresponding to the drop in pump performance; [NPSH] - Allowable cavitation The margin, is used to determine the conditions of use of the pump NPSH, usually take [NPSH] = (1.1 ~ 1.5) NPSHc. Third, the device calculates the NPSHa = Ps / Ïg + Vs / 2g-Pc / Ïg = Pc / Ïg ± hg-hc-Ps / Ïg Fourth, to prevent cavitation measures To prevent cavitation must improve NPSHa , So that NPSHa> NPSHr prevent cavitation measures are as follows: 1. Reduce the geometric suction height hg (or increase the geometric inversion height); 2. Reduce the suction loss hc, for which you can try to increase the diameter, minimize pipe length, elbows and accessories, etc .; Prevent long run at high flow rate; 4. In the same speed and flow, the use of double suction pump, due to reduce the inlet flow rate, the pump is not prone to cavitation; Cavitation occurs when the pump, the flow should be reduced or reduced speed operation; 6. Pump suction pump cavitation has a significant impact; 7. For pumps operating under harsh conditions, cavitation-resistant materials may be used to avoid cavitation damage.
Hydrofluorocarbons (HFCs), organic compounds that contain fluorine and hydrogen atoms,
are the most common type of organofluorine compounds. They are commonly used in air conditioning and as Refrigerants [4] in place of the older chlorofluorocarbons such as R-12 and hydrochlorofluorocarbons such as R-21. They do not harm the ozone layer as much as the compounds they replace; however, they do contribute to global warming. Their atmospheric concentrations and contribution to anthropogenic greenhouse gas emissions are rapidly increasing, causing international concern about their radiative forcing.
Fluorocarbons with few C-F bonds behave similarly to the parent Hydrocarbons, but their reactivity can be altered significantly. For example, both uracil and 5-fluorouracil are colourless, high-melting crystalline solids, but the latter is a potent anti-cancer drug. The use of the C-F bond in pharmaceuticals is predicated on this altered reactivity.[5] Several drugs and agrochemicals contain only one fluorine center or one trifluoromethyl group.
HFCs(hydro-fluorocarbon)
Hfcs(Hydro-Fluorocarbon),High Fructose Corn Syrup,Fructose Corn Syrup Hfcs,High Fructose Syrup
Quzhou Xiecheng Chemical Co., Ltd. , http://www.xcrefrigerant.com