heating system.ppt

Expansion tank Cubage calculation and installation piping of expansion tanks 溢流管 （Oberflow Pipe） 排污管 （Blow－off Pipe） 膨胀管 （Expansion Pipe） 循环管 （Circulation Pipe） 补水管 （feedwater Pipe） Cubage calculation equation: V——The cubage of the tank a——?expansion coefficient of water 0.0006 1/0C Vc——water capacity of the system ——Maximal temperature difference Sizing the gravity system pipe General Consideration: Every foot of pipe, every fitting ,every valve offers some more or less effective objection to the passage of water through it. The maximum available force for the arrangement must total more than all resistances if we are to obtain circulation. The first step in sizing the piping is to find out how much water we need for each radiator. Sizing the gravity system piping Water Velocities: The next problem is to decide how fast the water shall move. Experience warns against designing for high velocities, because with gravity circulation velocities are likely to be beyond us. The effect of the fitting: For various kinds of specialties, we must obtain the friction loss direct from the manufacturer. Resistance calculation: ?frictional resistance and local resistance. Check calculation: total resistance and Gravity force. Forced Circulation System 2 Compared with the force system and gravity system Typical system of force hot water system Compared with the force system and gravity system Using a pump to circulate hot water in stead of thermal head, we obtain several definite benefits: The circulation is independent of temperature It gives a quicker response Pump circulation allows the use of smaller bore pipes, thus saving in the first cost and enabling pipes to be fitted inconspicuously more easily, the thermal capacity of a system using smaller pipes is naturally less than one with large pipes, and this again affects the rate of heating up and response to controls. 4. Many forms of heat emitter are now suitable only for pump circulation, such as forced air