Control valves are used to control the hydronic system. They regulate the flow in function of the load. Therefore, control valves must always be connected with an actuator. Without control valves, only the static designed (peak) flow rates could be provided.
In the Hysopt Optimiser, the controlling ports of control valves are symbolised with a black triangle. In essence, there are two different types of control valve mechanisms: 2 & 3-way control valves.
2 & 3-way control valves
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2-way control valves vary the secondary flow rate while keeping the flow temperature constant. In contrast, 3-way control valves keep the secondary flow rate constant while varying the flow temperature. Using this difference in behavior, both valves will be the cornerstone for a large variety of distribution circuits that can be created.
Both control valves have the following parameters:
Valve type: a list containing three types of valves: 'Equi-percentile, ‘linear’ and ‘mixed’. More information on the importance of the valve type can be found below.
Control valve KVS-value: The KVS value expresses the amount of flow in a regulating valve at a fully open valve position that creates a pressure drop of 1 bar. This parameter will be calculated by the Optimiser or can be filled in & locked manually. Typically, the KVS value of a control valve is linked with the (DN) size of the valve.
KVS-value on the bypass gate: This is an optional parameter only found on a 3-way valve. It can be used when you wish to use a different KVS value than the one on the primary gate.
Continuous KVS-range: By default, the Optimiser uses a list of discrete variables when calculating the KVS value. If preferred, flipping the node allows you to use a continuous rage.
Control valve rangeability: KVS/KV0. The theoretical range between the maximal (KVS) and minimal (KV0) controllable flows. By default, the parameter is set at 30.
Control valve real rangability: KVS/KVr. The real controllable range between the maximal (KVS) and minimal (KVr) controllable flows. This value is always smaller than the theoretical range. By default, the parameter is set at 25.
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The greater the rangability values, the better the control action of the valve. When you notice in the software that the lift of a control valve is cycling continuously (usually between small values), it might be useful to increase the rangeabilities from 30 & 25 to 100 & 95 or even 500 & 495. This usually leads to a more stable control output, which can drastically reduce simulation times, but it might make the theoretical simulation to perfect. |
Minimal authority: The lower limit that is imposed to the Optimiser while running the ‘Optimise components’ step. By default, the parameter is set at 0.3. More information on a valve’s authority can be found here: https://hysopt.atlassian.net/wiki/spaces/HRM/pages/3089204794/Control+valve+authority.
Actual authority: The computed authority of the valve after running the ‘Optimise components' step. This value cannot be changed manually.
Full load valve position: The computed maximal opening position of the main gate on a 3-way valve. This restriction is used to protect the flow downstream against too high temperatures. An example can be found here: https://hysopt.atlassian.net/wiki/spaces/HRM/pages/3089204854/Active+mixing+circuit. This value cannot be changed manually.
Special types of control valves
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A (thermostatic) radiator valve and is a 2 way control valve typically used to control the flow going to a ‘radiator/convector’ end unit BC. The ‘radiator valve’ BC models the pressure drops over the valve much more in detail. This block is therefore mainly used in a technical/detail study. For conceptual studies, it's rather adviced to use a ‘throttle circuit’ BC. This is especially true whenever the ‘radiator/convector’ BC is used to represent a larger group of radiator end units, as the ‘radiator valve’ BC will generate very large pressure drops. It has the following parameters:
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