AixLib.Fluid.Movers.Compressors.BaseClasses.PartialCompression

# .AixLib.Fluid.Movers.Compressors.BaseClasses.PartialCompression

Partial model for compression that contains basic definitions used in various compressor models

## Information

This is a base model for compression processes that are used, for example, in rotary or scroll compressors.

#### Definition needed for completion

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

- Calculation of the mass flow rate `ṁ`.
- Calculation of the power consumed by the refrigerant Q̇ref.
- Calculation of the compressor's power consumption `Pel`.
- Definition of input and output pressures `pInl and pOut`.
- Definition of input and output specific enthalpies `hInl and hOut`.
- `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.

#### Efficiency modeling approaches

Actually, three different efficiency models are suggested and the modelling approaches of these efficiencies are shortly characterised below:

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

Efficiency | Formula | Comment
--- | --- | ---
Engine | `ηeng = Q̇ref / Pel` | Used for calculation of compressor's power consumption
Isentropic | `ηise = (houtIse - hinl) / (hout - hinl)` | Used for calculation of thermodynamic change of state
Volumetric | `ηvol = V̇ide / V̇rea` | Used for calculation of mass flow rate

These efficiency models are stored in AixLib.Fluid.Movers.Compressors.Utilities.EngineEfficiency, AixLib.Fluid.Movers.Compressors.Utilities.IsentropicEfficiency and AixLib.Fluid.Movers.Compressors.Utilities.VolumetricEfficiency. Therefore, the calculation procedure of the efficiencies are introduced as replaceable models and must be defined by the User.

#### Transient behaviour

The base model has a parameter `useInpFil` that is used to model the compressors's transient behaviour while changing rotational speed. 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 compressor's rotational speed. Thus, a step change in the input signal causes a step change in the rotational speed.
2. If `useInpFil=true`, which is the default, then the rotational speed is equal to the output of a filter. This filter is implemented as a 2nd order differential equation. Thus, a step change in the compressor's input signal will cause a gradual change in the rotational speed. 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 rotational speed, or, if the compressor is shut-down, to reach a rotational speed of 0.4%.

#### References

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

W. Eifler, E. Schlücker, U. Spicher and G. Will (2009): Küttner Kolbenmaschinen: Kolbenpumpen, Kolbenverdichter, Brennkraftmaschinen (in German). Publisher: Vieweg + Teubner

H. Qiao, R. Radermacher and V. Aute (2010): A review for numerical simulation of vapor compression systems. In: International Refrigeration and Air Conditioning Conference

P.C. Hanlon (2011): Compressor Handbook. Publisher: McGraw-Hill

V. A. Cara Martin and R. Radermacher (2015): AHRI Project 8013: A Study of Methods to Represent Compressor Performance Data over an Operating Envelope Based on a Finite Set of Test Data. Publisher: Air-Conditioning, Heating, and Refrigeration Institute (AHRI)

## Contents

Name | Description
--- | ---
EngineEfficiency | Model that describes the calculation of the overall mechanic efficiency
VolumetricEfficiency | Model that describes the calculation of the overall volumetric efficiency
IsentropicEfficiency | Model that describes the calculation of the overall isentropic efficiency
CompressorStates | Record that contains compressor's thermodynamic states at inlet and outlet
CompressorQualities | Record that contains compressor's qualities at inlet and outlet

## Revisions

- October 20, 2017, by Mirko Engelpracht:
  First implementation (see issue 467).

Generated at 2026-05-12T20:19:03Z by OpenModelicaOpenModelica 1.26.7 using GenerateDoc.mos