This model is an electric boiler with a pump with ideal mass flow control to get a given outlet temperature. It can be chosen if the outlet set temperature is constant or given by an input.
The efficiency is constant.
The mass flow is calculated based on a heat flow rate and a given constant outlet temperature. There is no volume considered.
There are no pressure losses included (pressures at inlet and outlet are given from the outside).
Overheating, i.e. exceeding the set outlet temperature, can be turned on or off.
The model calculates any mass flow that is necessary to reach the given temperature but limits the mass flow so that no flow reversal occurs and that the given maximum mass flow is not exceeded.
If the specific enthalpy at the inlet exceeds the set specific enthalpy, two cases will be distinguished:
The heat flow rate is always calculated according to the actual specific enthalpies and the mass flow rate.
For more details see the equations.
This model is only valid for ideal controls, i.e. ideally tuned controls with no control errors.
T_out_set: set point for outlet temperature
Q_flow_set: set point heat flow rate (negative for producers)
fluidPortIn: inlet for fluid
fluidPortOut: outlet for fluid
(no elements)
if inStream(fluidPortIn.h_outflow)>fluidOut.h then
if -Q_flow_set<Q_flow_small or not allowOverheat then
fluidPortOut.m_flow=0;
fluidPortOut.h_outflow=inStream(fluidPortIn.h_outflow);
else
fluidPortOut.h_outflow=Q_flow_set/fluidPortOut.m_flow+inStream(fluidPortIn.h_outflow);
fluidPortOut.m_flow=-m_flow_max; //maximum mass flow to keep the temperature increase at a minimum
end if;
else
fluidPortOut.h_outflow=fluidOut.h;
fluidPortOut.m_flow=-max(0,min(m_flow_max,-Q_flow_set/(fluidPortOut.h_outflow-inStream(fluidPortIn.h_outflow))));
end if;
Q_flow=fluidPortOut.m_flow*(fluidPortOut.h_outflow-inStream(fluidPortIn.h_outflow));
The model is only working properly in design flow direction. Reverse flow is not supported!
(no validation necessary)
(none)
Model created by Carsten Bode (c.bode@tuhh.de), Nov 2018
Model modified by Jan Westphal (j.westphal@tuhh.de), Jul 2019 ( added power port)