# Custom flash
This function calculates equilibrium condition with any number of fixed and freed system parameters.
## custom
`POST` `https://api.olisystems.com/engine/flash/{dbs_file_id}/custom`
run a custom equilibrium calculation
#### Headers
| Name | Type | Description |
| ------------- | ------ | ---------------------- |
| Authorization | string | Bearer {access\_token} |
| Content-Type | string | application/json |
{% tabs %}
{% tab title="200 Please look at "API call blueprint" page on how to obtain results" %}
```
{
"code": 200,
"data": {
"file_id": "dee854a6-59db-487d-ad08-a20dee691133",
"jobId": "f6b3375e-cd0f-4ace-a5ee-71e047b76754",
"resultsLink": "https://api.olisystems.com/result/flash/f6b3375e-cd0f-4ace-a5ee-71e047b76754?context=engine",
"status": "IN PROGRESS"
},
"message": "Process execution started Successfully",
"status": "SUCCESS"
}
```
{% endtab %}
{% endtabs %}
### Request payload
```json
{
"params": {
"temperature": {
"value": 40.0,
"unit": "°C"
},
"pressure": {
"value": 1.5,
"unit": "atm"
},
"fixedVars": [
{
"type": "vaporPhaseComposition",
"name": "BENZENEVAP",
"value": 16.0,
"unit": "mole %"
},
{
"type": "property",
"name": "volume",
"value": 440.0,
"unit": "L"
}
],
"freedVars": [
{
"type": "inflow",
"name": "BENZENE",
"value": 0.0,
"unit": "mol"
},
{
"type": "state",
"name": "temperature",
"value": 0.0,
"unit": "°C"
}
],
"inflows": {
"unit": "mol",
"values": {
"H2O": 50.0,
"BENZENE": 10.0,
"CH4": 20.0,
"NACL": 35.0
},
"totalAmount":
{
"value": 115.0,
"unit": "mol"
}
}
}
```
| **params** | type | description |
| ----------- | -------------------------------------------------------------- | ------------------------------------------------------------------------------------------------- |
| temperature | [valueObject](https://devdocs.olisystems.com/terms-definition) | specified or initial guess temperature with [unit](https://devdocs.olisystems.com/input-unit-set) |
| pressure | [valueObject](https://devdocs.olisystems.com/terms-definition) | specified or initial guess pressure with [unit](https://devdocs.olisystems.com/input-unit-set) |
| fixedVars | array of objects | list of objects to describe fixed flash output variables |
| freedVars | array of objects | list of objects to describe freed flash input variables |
{% hint style="danger" %}
The sizes of the object arrays, **params.fixedVars** and **params.freedVars** must be equal
{% endhint %}
#### Here is a description of the **type** and **name** attributes for the **params.fixedVars** array
| **params.fixedVars\[*****index\_number*****].type** | **params.fixedVars\[*****index\_number*****].name** |
| --------------------------------------------------- | --------------------------------------------------- |
| property | volume, enthalpy, pH |
| liquid1PhaseComposition | species name of liquid phase |
| liquid2PhaseComposition | species name of liquid phase |
| vaporPhaseComposition | species name of vapor phase |
| solid | species name of solid phase |
{% hint style="info" %}
species name can be retrieved from [chemistry information call](https://devdocs.olisystems.com/group1/api-functions/chemistry-info) under **result.species(trueName)**, respectively.
{% endhint %}
#### Here is a description of the **unit** attribute for the **params.fixedVars** array
| **params.fixedVars\[*****index\_number*****].type or .name** | **params.fixedVars\[*****index\_number*****].unit** |
| ----------------------------------------------------------------------- | ------------------------------------------------------------- |
| liquid1PhaseComposition, liquid2PhaseComposition, vaporPhaseComposition | mol/mol, mole %, ppm (mole) |
| solid | mol, kgmol, lbmol, mmol, µmol, (mol/100) |
| volume | L, ml, cm3, m3, E3m3, E6m3, ft3, Mft3, MMft3, gal, MMgal, bbl |
| enthalpy | cal, E3cal, E6cal, J, kJ, MJ, Btu, MMBtu |
#### This section explains the available flash input variables can be freed for this calculation
| **params.freedVars\[*****index\_number*****].type** | **params.freedVars\[*****index\_number*****].name** | **params.freedVars\[*****index\_number*****].unit** |
| --------------------------------------------------- | --------------------------------------------------- | ------------------------------------------------------------------------------- |
| state | temperature | °C, K, °F, R |
| state | pressure | atm, bar, barg, mbar, Pa, kPa, MPa, mmHg, Torr, inHg, psia, psig, inH2O, kg/cm2 |
| inflow | inflow name | mol, kgmol, lbmol, mmol, µmol, (mol/100) |
{% hint style="info" %}
in addition to the inputs shown above some optional properties may also be specified. They can be viewed [here](https://devdocs.olisystems.com/optional-inputs)
{% endhint %}
### JSON output (status = PROCESSED)
```javascript
{
"code": 200,
"data": {
"result": {
......
"calculatedVariables": [
{
"name": "BENZENE",
"value": 4.048793029736938,
"unit": "mol"
},
{
"name": "temperature",
"value": 45.5766850916292,
"unit": "°C"
}
]
}
},
"message": "Results returned successfully",
"status": "PROCESSED"
}
```
The output of this calculation is the [stream output ](https://devdocs.olisystems.com/stream-output-json)which is common result output for all OLI's flash calculations or an [error](https://devdocs.olisystems.com/error-output). In addition to this output the result also contains the values of the free variables which can be conveniently retrieved from the **result.calculatedVariables** array
| result.calculatedVariables [\[{}\]](https://devdocs.olisystems.com/terms-definition) | type | description |
| ------------------------------------------------------------------------------------ | ------ | ------------------------------- |
| name | string | name of calculated variable |
| value | number | value of calculated variable |
| unit | string | unit of the calculated variable |
### Survey Calculation
Survey calculation is supported for the variables below. Please refer to [Survey calculation](https://devdocs.olisystems.com/survey-calculation) for explained input schema.
| supported **params.surveyInputs\[{}].field** |
| ------------------------------------------------------------------------------------------------------------- |
| "/params/temperature/value" |
| "/params/pressure/value" |
| "/params/fixedVars/***i***/value" where ***i*** is the index (0 based) of **params.fixedVars** to be surveyed |
| "/params/freedVars/***i***/value" where ***i*** is the index (0 based) of **params.freedVars** to be surveyed |
---
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```
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