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The outstation
Published in G.J. Levermore, Building Energy Management Systems, 2013
The communications port in Fig. 2.5 is the electrical access point for communications. A port is a connection point in an electronic circuit where a signal may be input or output. Inside the outstation would be an additional small circuit board (not shown in Fig. 2.5) to interface with a modem or a LAN. This board is often known as a communications node controller (CNC). For communication purposes, each outstation would have its individual identification number and name. If the outstation did not have a keypad and display, there would be an additional communications port for connecting to a portable PC for local programming and reconfiguration.
Simplifications for hydronic system models in modelica
Published in Journal of Building Performance Simulation, 2018
F. Jorissen, M. Wetter, L. Helsen
Modelica models declare a number of variables and contain a number of equations from which the variables are solved. For pressure drop elements, these equations require boundary conditions from outside the considered model, and conversely the variables that are defined in a model may become boundary conditions in a different model. To enable this exchange of information, Modelica models use ports. Different types of ports exist, e.g. a RealInput, HeatPort or FluidPort. A RealInput is used to input a real variable into a model. A HeatPort is used to exchange heat. It consists of one potential variable, the temperature T, and one flow variable, the heat flow rate . A FluidPort represents a fluid connection and consists of variables representing the pressure at the port, which is a potential variable, the mass flow rate entering the model, a flow variable, and a stream variable representing the specific enthalpy of the fluid. A port may declare optional stream variables such as glycol concentrations and water vapour fractions. For each stream variable, two associated numerical values exist: one value assuming the fluid exits the model, which we denote by s and one value assuming the fluid enters the model, which is denoted using inStream(s). See Franke et al. (2009) for more information regarding stream variables.