ELECTRIC HEATER - model over view

Model Overview

Author / organization: Benedikt Leitner / AIT

Domain: Energy conversion device

Intended application: Return-supply connections in district heating networks or in combination with thermal storage tanks

Modelling of spatial aspects: Lumped (single device)

Model dynamics: Dynamic

Model of computation:

  • Time-continuous
  • The model avoids the use of events if possible

Functional representation: Explicit

ELECTRIC HEATER - input and output

Input and Output

Input variables :

  • Real m_flow_set: mass flow setpoint for pump [kg/s]
  • Modelica.Fluid.Interfaces.FluidPort port_a (acausal): fluid port at return side

Output variables:

  • Real P: current electric load [W]
  • Modelica.Fluid.Interfaces.FluidPort port_b (acausal): fluid port at supply side

ELECTRIC HEATER - related document

ELECTRIC HEATER - description

Short Description

A model of an electric heater including a pump. The pump controls the mass flow through the heater which heats the fluid to a set temperature. The electric heater has a constant power-to-heat efficiency and a nominal heat flow rate.

The electric heater takes water from the cold source (corresponding to the nominal return temperature value of the electric heater TemRet_nominal). The mass flow is set by the pump which is controlled through a ramping function. The heater increases the temperature of the fluid. In case the mass flow is below the nominal mass flow, the fluid temperature equals the nominal temperature TemSup_nominal. In case the mass flow is higher the heater is operating with full capacity Q_flow_nominal but is not able to reach the nominal temperature TemSup_nominal.

Present use / development status

A ramping function is used to control the mass flow of the pump m_flow_set of the electric heater. The function starts at zero. After one hour the ramp starts and increases to 0.1 within two hours. It stays at 0.1 till the end of the simulation.

The model is part of AIT’s internal Modelica library for district heating and is usable for co-simulation with electric network models. The Modelica library uses the Modelica standard library and the IBPSA library as a core.

ELECTRIC HEATER

Model Details