Interface for ApacheSim

ApacheSim is a dynamic thermal simulation program based on first-principles mathematical modelling of the heat transfer processes occurring within and around a building.

 

Results from ApacheSim are viewed using the programs Vista, OutView and Apache Review.

 

For an account of calculation methods used in ApacheSim see ApacheSim Calculation Methods.

 

 

Specify the dates for the first and last days of the simulation. The user can choose 29^th February as a start or end date, if the ‘Treat simulation as leap year’ checkbox in the ‘Simulation Calendar’ tab of ApLocate is checked. See the ApLocate documentation for further details.

 

Specify the time step to be used in the simulation. A time step of 10 minutes is suitable for most building simulations. Smaller time steps may be necessary to capture the detail of control operation in simulations involving ApacheHVAC.

 

Specify the time interval at which you require results to be recorded. The reporting interval must be greater than or equal to the time-step and not less than 6 minutes. A reporting interval of 1 hour is satisfactory for most simulations. A shorter interval allows you to examine simulation results in more detail.

 

A period of preconditioning is necessary to ensure that the building enters the simulation period in a realistic thermal state. Preconditioning is necessary because of heat storage in the building fabric. For lightweight buildings a preconditioning period of 10 days is sufficient. For heavyweight buildings as much as 30 days or more may be needed. The appropriate period of preconditioning may be established by increasing the number of preconditioning days until the effect of further increments produces a negligible change in the first day’s simulation results.

 

Save the simulation settings.

 

Run the simulation.

 

Exit the ApacheSim interface.

 

The Results File (which has extension *.aps) is used to store simulation results for later viewing in Vista. By choosing a name for this file you will be able to keep it separate from results from other simulation runs.

The estimated size of the results file is shown at the lower right of the dialogue.

 

Tick this box to include the effects of solar shading, as calculated by SunCast in the simulation.

It is important to ensure that the shading data is kept up to date with any changes to the building geometry. The shading calculations should be repeated after any such changes.

 

Tick this box to couple the simulation to MacroFlo or MacroFlo Lite natural ventilation analysis.

 

Tick this box to couple the building simulation to ApacheHVAC system simulation, and select a  system file from the list.

 

Tick this box to couple the building simulation to Radiance lighting simulation results.

Air exchanges specified in Space Data are divided into three categories: infiltration, auxiliary ventilation and natural ventilation. Any infiltration air exchanges are included unconditionally, but auxiliary and natural ventilation air exchanges may be switched on or off at simulation time.

Tick this box if you wish to include Space Data auxiliary ventilation air exchanges in the simulation. Note the setting system outside air supply is not disabled by this mechanism.

If ApacheHVAC is coupled to ApacheSim it is important that any mechanical ventilation air exchanges are represented either in the Space Data or in ApacheHVAC but not both. It is permissible to use these different specification mechanisms in different rooms, but if they are applied in the same room they will be superimposed.

 

Tick this box if you wish to include Space Data natural ventilation air exchanges in the simulation.

If MacroFlo is coupled to ApacheSim it is important that any natural ventilation air exchanges are represented either in the Space Data or in MacroFlo but not both. It is permissible to use these different specification mechanisms in different rooms, but if they are applied in the same room they will be superimposed.

 

These options specify modelling techniques used in the simulation and the output variables to be recorded for viewing in Apache’s Internal Results Review facility.

 

The following internal convection models are available in ApacheSim:

Fixed coefficients specified by CIBSE

Variable coefficients calculated according to CIBSE methods

Variable coefficients calculated from the relations proposed by Alamdari &Hammond

User-specified fixed convection coefficients

 

The first three options may be selected from the list-box. The fourth option will apply to any constructions for which fixed internal surface coefficients are set in the constructions database program APcdb. For such constructions the fixed value will override the method selected in the Simulation Options interface.

A brief account of the convection models follows. For more detail see ApacheSim Calculation Methods.

 

This setting specifies fixed internal convection coefficients as used in the CIBSE ‘Simple Model’ for Heat Loss and Heat Gain calculations.

 

This setting specifies varying convection coefficients dependent on surface orientation, air-surface temperature difference and mean room air velocity, calculated by the procedure described in CIBSE Guide C.

 

This setting specifies varying convection coefficients dependent on surface orientation, room geometry and air-surface temperature, calculated using correlations established by Alamdari & Hammond.

 

This option allows you to select the solar radiation model to be used in the simulation. The settings are:

 

This model treats the diffuse component of solar radiation as radiating with equal intensity from all parts of the sky vault.

 

This model applies an anisotropic diffuse radiation model in which the intensity of the radiation is greater in the region near the sun. The degree of anisotropy is greatest under clear sky conditions.

 

This setting turns off all solar radiation. This can be useful in heat loss studies based on zero heat gains.

 

At the start of the preconditioning period the building fabric will be initialised to this temperature. Selecting a value that approximates the long-term average temperature inside the building will minimise the amount of preconditioning required.

 

This option relates to HVAC simulation results generated by ApacheHVAC that may later be viewed using Apache’s Internal Results Review facility. Select the days of the week for which you wish to record details of the psychrometric state of air at nodes in the air conditioning system.

 

By default, the energy results available in the Apache Review program are available as monthly totals. Select Detailed Loads File to record hourly energy totals, and Half Hourly Loads File to record half-hourly energy totals. These settings do not affect results available in Vista.

 

These options allow you to specify which simulation outputs will be available for viewing in Vista. They also allow you to select alternative modes for viewing simulation results. These parts of the interface appear on separate tabs.

 

This tab deals with output to be written to the results (.aps) file for display in Vista, and allows you to specify which outputs will appear there.

 

By ticking one or more of the following boxes you can specify the simulation outputs to be written to the results file for all rooms:

Standard outputs : the basic set of room outputs

Sensible casual gain breakdown : a detailed breakdown of casual gains

Latent casual gain breakdown : a detailed breakdown of latent gains

Latent ventilation gain breakdown : a detailed breakdown of latent gains

 

By ticking one or more of the following boxes you can specify the simulation outputs to be written to the results file for a subset of rooms selected in the list appearing at the bottom of the dialogue:

Outputs required by MicroFlo : the outputs required for MicroFlo boundary conditions

Standard outputs : the basic set of room outputs

Sensible casual gain breakdown : a detailed breakdown of casual gains

Latent casual gain breakdown : a detailed breakdown of latent gains

Latent ventilation gain breakdown : a detailed breakdown of latent gains

Convective portion of plant & casual gains : the portion of plant and casual gains that is input to the room air. This is one of the variables required by MicroFlo.

Surface temperatures : the temperatures of room surfaces. These are required by MicroFlo.

External incident solar flux : the solar irradiance on the external surfaces of room elements.

Internal incident solar flux : the solar irradiance on the internal surfaces of room elements.

 

The ‘detailed outputs for selected rooms’ specified above will be written to the results file for rooms selected from this list. Select rooms by clicking, holding the control key down to add further rooms to the list.

 

 

This tab deals with output display modes other than Vista.

 

Tick this box to run the Apache Review program on completion of the simulation. This provides options for displaying detailed results from ApacheHVAC. Apache Review will shortly be superseded by facilities in Vista. In the interim it provides the means for viewing surface temperatures and detailed psychrometric results generated by ApacheHVAC. To view these results in Apache Review you will need to set Psychrometric Results to ‘All Week’ in Simulation Options.

 

Tick this box to run the OutView program on completion of the simulation. OutView provides a summary of the input data for the ApacheSim run and monthly energy totals. This data is stored in the simulation output file (a text file with extension .out). OutView provides facilities for browsing and printing this file.