New integrated model for chilled ceilings

A chilled ceiling model has been integrated in the multi-zone building model (Type 56). The integrated model allows adding a chilled ceiling to a room quickly and easily. This model is similar to the existing model of thermally-active building elements (so-called "active layers" in Type 56).

The model is based on a new resistance model developed by EMPA, Switzerland. Unlike a concrete core heating or cooling system, a chilled ceiling is practically thermally decoupled from the wall. The characteristic constant resistance associated with a particular model of chilled ceiling is determined by data measured under given test conditions (e. g. DIN4715-1). This data is typically supplied by the manufacturer. All other resistances are time-varying and are calculated during the simulation.

The main advantages of the new model are:

• Easy definition as an active layer within the TRNBuild interface (^ no additional external links, etc.)

• Measured data supplied by the manufacturer is used to initialize the model

• Ability to handle different types of chilled ceilings

• Variable flow rates

• Fast simulation

New features of TRNBuild — automatic segmentation of active layers

The thermally-active layer model assumes a linear temperature profile over the pipe length. In general, this requires the use of 3 segments to obtain a good approximation of the real temperature profile and the segments must be coupled to each other. In TRNSYS 15, this had to be done manually. The subdivision and the coupling of wall segments is now done automatically. The figure here below illustrates the approximation of a temperature profile (black line) with one segment (red line, x) and with 4 segments (green line, V).

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