This package contains a basic flow model that is used by the various models that compute pressure drop.
Because the density does not change signficantly in heating, ventilation and air conditioning systems for buildings, the flow models compute the pressure drop based on the mass flow rate and not the volume flow rate. This typically leads to simpler equations because it does not require the mass density, which changes when the flow is reversed. Although, for conceptual design of building energy system, there is in general not enough information available that would warrant a more detailed pressure drop calculation. If a more detailed computation of the flow resistance is needed, then a user can use models from the Modelica.Fluid library.
All functions have an argument m_flow_turbulent
that determines where the
flow transitions to fully turbulent flow. For smaller mass flow rates,
the quadratic relation is replaced by a function that has finite slope
near zero pressure drop. This is done for numerical reasons, and to approximate
laminar flow, although the implementation does not use a linear function.
The two main functions are
IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp
and
IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow
that compute the mass flow rate or the pressure drop, respectively.
Both functions are two times continuously differentiable.
First and second order derivatives are provided
in the function that have the suffix _der
and _der2
.
Name | Description |
---|---|
basicFlowFunction_dp | Function that computes mass flow rate for given pressure drop |
basicFlowFunction_dp_der | 1st derivative of function that computes mass flow rate for given pressure drop |
basicFlowFunction_dp_der2 | 2nd derivative of flow function2nd derivative of function that computes mass flow rate for given pressure drop |
basicFlowFunction_m_flow | Function that computes pressure drop for given mass flow rate |
basicFlowFunction_m_flow_der | 1st derivative of function that computes pressure drop for given mass flow rate |
basicFlowFunction_m_flow_der2 | 2nd derivative of function that computes pressure drop for given mass flow rate |
Validation | Collection of validation models |