Valve stem control of the lowest price

The use of a straight valve and three-way valve control valve under what circumstances? Generally speaking, the lowest price, three through the mixed valve, the three pass valve is the highest. If you use a straight through valve to control a number of coil, when the load is reduced, the system flow will fall. Because there is only one flow of water between the water supply and the return line, it is necessary to pass through the valve and the coil. When using any type of three-way valve, flow system basically unchanged. Under load, return water temperature rise and close to the temperature of the water supply.
At low load to maintain the basic flow of the system is not good, depending on the stainless steel valve stem system. If the water flow is too small, due to the constant flow of water to the small flow of mechanical energy, the pump may overheat. The use of several pumps in parallel can be avoided in this case, when the flow down, you can turn off some of the pump. Another disadvantage of small flow chilled water is that the velocity in the evaporator is too small, the distribution is very uneven, may cause the water to freeze and expand the pipe.
For some large equipment, such as frozen water center, three-way valve for flow remain unchanged is not good, because all of the pump must be continuous operation, so that all the water chiller are to maintain a lot of traffic.