Abstract
Natural ventilation can help maintain thermal comfort during summer periods. In simulation models for thermal comfort analysis, occupant behaviour related to natural ventilation is often included through definition of ventilation rule sets. For example, windows are opened when room temperature exceeds a given limit while outside temperatures remain below a threshold. Such rules are included in building codes, such as DIN 4108-2 [1]. However, these rules are defined with respect to fixed step time integration methods, often using hourly step sizes. Straight-forward implementation of such rules in error controlled adaptive time step integration solvers (including drivers for Modelica models) fails. The article discusses strategies and model variants that work with such modern solvers and discusses new model parameters such as the delay time or dead-band size. The impact of these parameter choices is illustrated with sensitivity studies using the thermal room model THERAKLES [3-5].
Highlights
The importance of calculating summer heat protection has increased in recent years
This may be due to architecture with ever larger glass facades, smaller storage masses or higher internal loads
Though, no comment is made in the standard on the minimum/maximum length of fixed steps used in such simulators
Summary
The importance of calculating summer heat protection has increased in recent years This may be due to architecture with ever larger glass facades, smaller storage masses or higher internal loads. Numerical methods have been known for a long time, but have only recently been used more widely. This is mainly due to the fact that these procedures are taken into account in the standards. There are methods with constant time steps and those with variable time step size adjustment. The former are easier to implement and account for the largest share of the procedures used. Small time steps used only if necessary, otherwise larger time steps – shorter calculation times
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