AixLib.Fluid.Actuators.Valves.ExpansionValves.BaseClasses.PartialExpansionValve

# .AixLib.Fluid.Actuators.Valves.ExpansionValves.BaseClasses.PartialExpansionValve

Base model for all expansion valve models

## Information

This is a base model for simple expansion valves that are used, for example, in close-loop systems like heat pumps or chillers.

#### Equations needed for completion

Three equations need to be added by an extending class using this component:

- The momentum balance specifying the relationship between the pressure drop dp and the mass flow rate m_flow. Therefore, different modeling approaches are suggested that can be easily expanded.
- `port_b.h_outflow` for flow in design direction.
- `port_a.h_outflow` for flow in reverse direction.

Moreover, appropriate values shall be assigned to the following parameters:

- `dp_start` for a guess of the pressure drop
- `m_flow_small` for regularization of zero flow.
- `dp_nominal` for nominal pressure drop.
- `m_flow_nominal` for nominal mass flow rate.

#### Modeling approaches

Actually, three different modelling approaches are suggested and saved as enumeration in AixLib.Fluid.Actuators.Valves.ExpansionValves.Utilities.Choices.CalcProc. In the following, these modeling approaches are characterised shortly:

"Modelling approaches" border="1" cellspacing="0" cellpadding="2" style="border-collapse:collapse;">

Approach | Formula | Comment
--- | --- | ---
Linear | `ṁ = C Avalve dp` | Used for testing or initialisation
Nominal | `ṁ = ṁnominal / dpnominal Avalve dp` | Used mainly for initialisation
Flow coefficient | `ṁ = C Avalve sqrt(2 ρinlet dp)` | Chosen by default and follows from Bernoulli's law

For the third approach (i.e. flow coefficient), different calculation models are stored in AixLib.Fluid.Actuators.Valves.ExpansionValves.Utilities.Choices.FlowCoefficient. Therefore, the calculation procedure of the flow coefficient C is introduced as replaceable model and must by defined by the User.

#### Transient behaviour

The base model has a parameter `useInpFil` that is used to model the valve's transient behaviour while opening or closing. Generally, this approach uses the same modeling attempt as the stat-up and shut-down transients introtuced for flow machines (see AixLib.Fluid.Movers.UsersGuide). Therefore, just the parameter's affections are presented here:

1. If `useInpFil=false`, then the input signal `opeSet.y` is equal to the valve's opening degree. Thus, a step change in the input signal causes a step change in the opening degree.
2. If `useInpFil=true`, which is the default, then the opening degree is equal to the output of a filter. This filter is implemented as a 2nd order differential equation. Thus, a step change in the fan input signal will cause a gradual change in the opening degree. The filter has a parameter `risTim`, which by default is set to 1 second. The rise time is the time required to reach 99.6% of the full opening degree, or,if the ventil is closed, to reach a opening degree of 0.4%.

#### References

In the following, some general references are given for information about modelling expansion valves. The modelling approach presented here is alligned to the modelling approaches presented in the literature:

Li, W. (2013): Simplified modeling analysis ofmass flow characteristics in electronic expansion valve. In: Applied Thermal Engineering 53(1), S. 8–12

X. Cao, Z.-Y. Li, L.-L. Shao and C.-L. Zhang (2016): Refrigerant flow through electronic expansion valve: Experiment and neural network modeling. In: Applied Thermal Engineering 92, S. 210–218

## Contents

Name | Description
--- | ---
FlowCoefficient | Model that describes the calculation of the flow coefficient

## Revisions

- October 16, 2017, by Mirko Engelpracht, Christian Vering:
  First implementation (see issue 457).

Generated at 2026-05-09T18:18:56Z by OpenModelicaOpenModelica 1.26.7 using GenerateDoc.mos