HeatedZone

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The Heated Zone model simulates various influences on the internal temperature of a building. It additionally includes and considers the behavior of persons inside a building which have effect on the electricity and heat demand of the energy system. A zone model can be coupled with other zone models via the temperature interface. This enables the modeling of complex buildings with different rooms or zones and different heat and electricity demand. Apposed to the 'BuildingZone'-model the 'HeatedZone' has the ability to simulate a buildings internal heating system (e.g. floor heating). Therefore a heating system can be directly connected to the model via a flow and return pipe (if 'LoadCalculation' and 'Heat' are 'true').

The zone temperature depends on various influences:

• Heat transmission through walls, windows and other boundaries (e.g. doors) (qtrans)

• Heat bridge losses (qHB)

• Solar yields (qsol)

• Ventilation losses (qvent)

• Internal yields and losses via persons as well as electricity and water usage (qel, qpers)

• Internal heat storage (air, walls, inner masses) (Q)

• Heating via heating system (qHT)

To simulate the temperature characteristic in a building zone various system parameters must be defined before simulation. Firstly, the model parameter dialog and the model itself, have to be configured:

• Zone number visualizes the parameterized zone model in a complex simulation model. If the zone is coupled with other neighboring building zones, the number of zones in the desired simulation model must be specified.

• Number of boundaries (max: 9, min: 1) defines how many boundaries (wall etc.) should be modeled. Number of inner masses (max: 4, min: 0) defines the number of internal additional heat storages (e.g. inner walls and ceilings).

• To initialize the simulation system the initial indoor temperature and return temperature of the heating system must be defined.

• LoadCalculation specifies, if the zone model should only be used to calculate heating and cooling depending on outer influences (i.e. the zone temperature follows reference zone temperature level - TZoneRef has to be connected) or if the zone temperature should be simulated taking heat yields, losses and heating into consideration.Note that the flow and return pipe of the heating system must be connected.

• useDayTime configures what time format is used. If the input data sets (i.e. for the persons' behavior and electricity demand) are only defined for a day, the parameter should be set to 'true.' If input data sets are defined for specific times in a year (i.e. 0 to 8760h) the parameter should be set to 'false.'

• useWindowShading offers the functionality of considering the shading of windows in each boundary, using an external signal (i.e. 0: fully irradiated, 1: fully shaded). If this value is set to 'true' the external WindowShading signal vector (dimension is number of boundaries) has to be defined with external data for each vector component. Otherwise, numerical problems could occur. This feature is mostly used in combination with building energy management systems.

• DINcalc in the parameter dialog 'Heat and Cool Factors I,' defines if internal heat loads, electrical power demand and the presence of persons in the zone should be modeled using DIN standards (DIN 2078) or external free-parameterizable input data sets.

If the heated zone is not to be heated by a heating system, the parameter 'Heat' should be set to 'false'. If set to 'true' the heating system must be parameterized in the parameter dialog. Note that volume specifications of the heating medium are required to avoid numerical problems. Depending on the selected heating system, it should be set between 100 to 150l per 100m2 of the net floor space of the zone (equal to floor heating system). The installed normal heating power is defined as heat power per m2 of the net floor space area. Most often this value lies between 20W to 200W. The type of heating system (e.g. floor heating system) is defined via the heating system exponent (n):

• n=1.1: floor heating

• n=1.2-1.3: panel radiator

• n=1.25: ribbed radiator

• n=1.3: radiator

• n=1.25-1.45: convector

This exponent defines the share of heat convection and radiation dependent on the heating system design.

Internal heat yields per person have to be parameterized (e.g. heat of body, heat losses due to cold water usage, heat yields due to usage of electric devices). The ventilation losses are defined via air leakage through boundaries. To assure an acceptable CO2-level and an adequate humidity, in the zone, further ventilation is needed. The losses are thus defined by an additional air volume flow between the zone and atmosphere (LComfortVentilation, normally 25m3/h per person). This air volume flow can be ensured through window or active ventilation. An active ventilation system causes additional electricity demand depending on the resulting volume flow. Note that a heat recovery rate of the system can be defined.

Inner masses can be seen as additional heat storages within the building zone. To simplify the simulation process it is assumed that these masses always stay at room temperature level.

Each boundary has to be parameterized separately. Therefore boundary specific surface area (e.g. walls, windows etc.), heat transmission factors (U-value) and material constants (i.e. heat capacity and density) must be defined. To configure the building zones, the alignment of each boundary must be determined via inclination and orientation angle:

• Inclination angle: 90° vertical wall, 0° flat ceiling or floor.

• Orientation angle: 0° - boundary normal points towards north, 90° - east, 180° - south, 270° west.

Additional correction factors allow for a more detailed description of the solar radiation absorption. Note that the frame and dirt correction factors are only used to reduce solar radiation absorption of the windows. The shading correction factor is additionally used to variate the heat absorption of the walls. Note that internal building boundaries (i.e. internal wall or ceiling) are not irradiated by the sun and thus the associated shading correction factor should be set to 1. Generally, these correction factors reduce solar yields (i.e. maximum shading: 1).

If a building consists of several building zones and heat should be interchanged between these zones during a simulation process, it is necessary to connect neighboring zones within the simulation model. To enable this the maximum number of zones should be set to greater than 1. This in turn allows for the parameter 'contactBound' to be set to the number of the neighboring zones of each boundary (1, 2, 3 ....). If this parameter is set to zero, the boundary is connected to the atmosphere.

If the boundary of a zone is to be the ground surface, the parameter 'groundContact' must be set to 'true' and the depth of the connected ground surface defined. For vertical walls with ground contact, use the average depth of the wall. If a boundary is connected to the ground, main heat transmission takes place via heat conductance. So, the outer heat transmission factor is not relevant. Normally for outer walls, this factor is set to a value of about 20W/m2. For inner walls, the heat transmission factors are normally set to a value of about 7.5W/m2. The additional absorption coefficient describes the influence of the outer wall color regarding solar heat absorbency (white 0.2, dark grey 0.8).

Overall, a reduced set of result characteristics can be visualized via the corresponding result dialog. Additional output characteristics, like solar gains, ventilation losses, etc., can be enabled via the TypeDesigner by setting corresponding and predefined output variables from protected, to public.