AG VLSI Design and Architecture

SFB 501 - Project D1: Application System "Buildings"

PSiGene Pattern Catalog

Intent

The ThermalMass pattern computes the temperature of a mass depending on the amount of heat affecting the mass. For example, the air in a room is a thermal mass, and also walls or layers may be seen as a thermal mass.

Also Known As

Simulation thermischer Masse [RIE96] ( http://wwwagz.informatik.uni-kl.de/projects/SFB501/D1/PSiGene/publications.shtml#Rie96.0 ).

Motivation

A volume has to act as a thermal mass to compute its temperature. This pattern works on the assumption that the temperature is always the same in every spot inside a thermal mass. Usually, rooms of a building are modelled as thermal masses. But also walls, ceilings and floors may act as a thermal mass. Decisive for a thermal mass is it stores a specific amount of heat, and (probably) delivers this heat to its surroundings. Exchange of heat between single masses can be direct (see ThermalExchange ) or indirect (via layers, see ThermalConnection ).

Applicability

This pattern can be bound to any thermal mass. Typical this is a room or a thick wall. But also a night-storage heater may be modelled as a thermal mass. An important property of a mass is its ability to store a specific amount of heat. This storage ability depends on the specific heat capacity of the material (or gas) the mass consists of, and its volume. Additionally the amount of heat flowing into or from the mass must be known or calculable.

Structure

This pattern only contains functionality for one class: namely, the thermal mass itself.

Participants

Collaborations

The computation relies on the calculation of the amount of heat flowing into or out of the mass. Usually these are: the amount of heat caused by transmission (through walls etc.), the amount of heat caused by radiation (radiators and sunlight), and direct exchange of heat (e.g., open windows). All influencing amounts of heat have to be modelled separately.

Consequences

On application the volume and the heat capacity of the mass must be known. On binding to a model-class all influencing elements must exist. Usually, the depending objects will be bound to the thermal mass via an Indirection Pattern (SimpleIndirection , ComplexIndirection , etc.).

Implementation

    self {amountOfHeat}:
        (self {temperature} * self {volume}
         * self {getHeatCapacity}).
    self {timeOfLastComputation}:
        Scheduler simSched simMillisecondClockValue.

    | heatCapacity collectedHeatFlows timeNow |
    timeNow:= Scheduler simSched simMillisecondClockValue.
    heatCapacity := self {getHeatCapacity}.
    collectedHeatFlows := self {getHeatFlowsFor}: self.
    self {calculateTemperature}WithCapacity: heatCapacity
        withHeatFlows: collectedHeatFlows
        while: ((timeNow - self {timeOfLastComputation}) / 1000).
    self {timeOfLastComputation}: timeNow.

        withHeatFlows: heatFlows
        while: passedTime
    self {amountOfHeat}:
        (self {amountOfHeat} + (heatFlows * passedTime)).
    self {temperature}:
        (self {amountOfHeat} / (self {volume} * capacity)).

Related Patterns

ThermalExchange

PEdit description

Pattern ThermalMass Category simulation
    ObjectType use target
    Attribute use temperature
    Attribute use amountOfHeat
    Attribute use volume
    Attribute use preset timeOfLastComputation
    SingleMethod implement preset init
    SingleMethod implement compute
    SingleMethod implement preset calculateTemperature
    SingleMethod use getHeatCapacity
    SingleMethod use getHeatFlowFor
End