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Valve selection basics
First, the flow of the valve Kvs Kvs valve reflects the ability to pass the valve, which is defined as the pressure across the valve when the two ends of the flow rate, Kvs is a valve characteristic parameters and valve structure is a constant value . Formula known valve design flow and valve Kvs value, can calculate the pressure drop through the formula, to provide the basis for the selection of pumps and valves. Known design flow of 5, the valve Kvs 20, the pressure drop of the valve, by the formula Second, the valve selection Note: the network provides the minimum capital pressure head for three, the ideal electric flow control valve flow curve of any valve Has its inherent flow characteristics, which reflect the relative flow of the valve and relative stroke between the relationship. When the valve pressure is fixed before and after the resulting flow characteristics, known as the ideal flow characteristics of the valve. Common valve ideal flow characteristics are mainly the following four categories, shown in Figure 2: 1. Straight type: unit stroke changes caused by changes in flow equal. Small flow changes in traffic, not easy to fine-tune and control, with poor will produce oscillation. 2. Parabolic: The flow characteristic is a quadratic parabola, between the straight line and equal percentage characteristics. 3. Equal percentage: the same trip in a small opening small changes in flow, opening large flow changes, suitable for large load changes in the system, also known as logarithmic characteristics. (Air-conditioning system for more than the electric control valve) 4. Quick-open type: stroke smaller, the flow is relatively large, with the increase of flow to reach the maximum flow. Valve effective stroke