2.0 Introduction
2.1 Simulation strategy
2.2 General outline of program operation
2.3 Data file management
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Section Two

A guide to effective system use

2.0 Introduction

In use ESP-r can be divided into two distinct parts.

The first is concerned with establishing a valid data model (description of the building and/or plant configuration) for simulation. This will involve the use of the Project Manager. The support modules can then be used to increase the detail of the simulation to follow, if this is deemed necessary.

The second part is concerned with the simulation processing and subsequent results analysis. This will involve the use of the Simulator and the Results Analyser. Note that all ESP-r modules are invoked from the Project Manager.

In using ESP-r it is not important to know all the relationships between the ESP-r program modules and the system’s data structures. However for a deeper appreciation these relationships are shown in Figure 2.1.
To work with ESP-r you need to be able to cope with a range of technical concepts relating to material properties, control systems, and the like. Information on the data requirements of ESP-r is held on-line and is accessible through the Project Manager (via its tutorial facility). Additional details are given in a separate document "Summary of ESP-r’s Data Model".

Image FIGS/fig2.1.epsi.png

Figure 2.1 Relationship between the ESP-r application modules and databases.

For each zone in the building a geometry, construction and operations file must be established. Then, optionally and to increase simulation rigour, one or more of the following zone files can be set up to replace the default schemes implied by the data of the essential files: a shading/insolation file, a blind/shutter control file, a view factor file, an air flow file, a casual gain (control) file and a convection coefficients file. The existence of these optional files is indicated by the entries of a zone utilities file created for the purpose. The system configuration file is now set up to define the zones and, perhaps, the plant components which will participate in a simulation. Following this, the configuration control file is established to define the control to be imposed on building zones and plant components. All of these files are created and/or edited via the Project Manager. This program module can also be used to establish the data sets as required by the Fluid Flow Simulation Module and the Insolation and Shading Prediction Module; namely, a configuration leakage distribution file, a pressure coefficients file and a site obstructions file. Note that some of the optional zone files can also be created directly from the support modules - for example the View Factor Prediction Module can create a zone view factor file. This is a powerful feature of ESP-r.

There are other files active in the system. These include the primitives and composite construction databases, the event profiles database, the plant components database, the windows database and the climate database. In addition: the Simulator will produce two databases, for building- and plant-side, for transmission to the Results Analyser; the Simulator can also produce a fluid flow results file for analysis and archival purposes; and many of the modules can produce detailed computation trace files for fault finding and highly focused appraisals. Figure 2.1 summarises these possibilities and indicates the file types involved.

The next section of the documentation set outlines a strategy for effective use of these modules. Interactive operation, by means of hierarchical menu drivers or function button protocols, is also explained and advice is given on managing the file structures which result from the data preparation and simulation activities.

2.1 Simulation strategy

The following step-by-step procedure should be closely followed by a novice. On the other hand, an experienced user may prefer an alternative strategy which bypasses some steps or changes their order.

1.

Analyse the design problem in hand and decide on the performance features to be appraised by ESP-r. Perhaps zone comfort levels are to be determined, the consequences of alternative design options assessed, or an optimum control regime formulated. This is an important task since it will influence the time and expense incurred thereafter.

2.

Now decide on the minimum number of building zones and plant components which will yield the performance measures required. For example, a one zone building model will allow an appraisal of summer overheating in the absence of cooling and against any number of design hypotheses. The same model, combined with a six plant component air conditioning plant (a mixing box, humidifier, fan, cooler, heater and supply duct, say), will allow a study of plant energy consumption against several control options. Avoid, in the first instance, any attempt to simulate large, complex building/plant systems. It is, of course, possible to undertake such an exercise, but only at the expense of time (data preparation) and cost (simulation). Very often good design insight can be obtained from simulations directed at portions of the overall system. It is important not to be merely led by the system but to give careful thought to the problem composition. Perhaps small multi-zone building problems, with specified zone conditions maintained, can be used to study several building design options. Then, at some later stage, a plant systems can be progressively added. In ESP-r terminology, the final system for simulation, irrespective of size or composition, is termed the system configuration.

3.

A computer model of the system configuration must now be created via the Project Manager. The underlying procedure is as follows. Firstly, each building zone in the configuration is described in terms of its geometry, construction and operation. This results in the creation of three mandatory disk files per zone. A system configuration file is then built. This contains a reference to these zone files, information defining zone interaction, and a description of the plant network (if one exists) in terms of individual components, their inter-connections and building associations. At the appropriate point, any of the constructions databases, the event profiles database, the plant components database or the optics database can be accessed and an item contained therein extracted to define a zone property or plant component.

The designer is simply required to answer a series of questions concerning the system configuration. Control of this interactive dialogue, along with validity checking and automatic disk file building, is the principal function of the Project Manager.

4.

At this stage, additional model details can be added.

An air flow file containing time-series infiltration and zone-coupled air flow for use during a simulation. If present, these air flows supersede the design air change profiles specified in the corresponding zone operation file. Note that if a building leakage description is active (see later) then calculated flows will supersede both design air change profiles and time-series air flow data.

A casual gains file containing time-series heat gains for use during a simulation. Again, if specified, the casual gains will supersede any casual gain profiles defined in the corresponding zone operation file.

A casual gains control file containing information on scheduling of casual gains in order to simulate, for example, various switching strategies for artificial lighting based on the availability of daylight.

A view factor file containing inter-surface view factors for use in a simulation to improve longwave radiation calculations.

A shading/insolation file containing time-series data on external surface shading and/or internal surface insolation.

A convection coefficients file allowing the specification of zone surface convection values to supersede those values which are computed at simulation time on the basis of natural convection considerations.

A transparent multi-layered constructions file allowing elected zone multi-layered constructions to be declared transparent.

A flow domain file specifying a 1-, 2- or 3-D grid and related parameters in support of a CFD simulation.

Each of these optional zone files can be created by terminal input directed by the Project Manager.

The time taken to reach this stage can vary greatly. An experienced user will require about 20 minutes per zone if the required data is readily available. On the other hand a beginner can take substantially longer. The only rule is to omit complexity in cases where its inclusion cannot significantly influence the performance aspect to be tested. For example, the omission of wall vapour barriers will have little effect on summer cooling loads but will completely alter winter interstitial condensation profiles.

5.

A plant network can now be defined, component-by-component, and connected to the established building model. It is normal practice to bypass this step at an early design stage. Instead ideal control statements are associated with each zone to allow a study of the effects of the various design parameters. At some later time the plant is added to allow a study of the control issues. Of course, if the relationship between the building-side design issues and the plant characteristics are strong, and the plant details are known, then a combined building/plant study can be undertaken from the outset.

6.

Simulations can now be commissioned from within the Project Manager against the assumption that the configuration is not subjected to control (a free-floating simulation). However, in most cases, some control will be required. From the Project Manager the control regime can be specified in terms of sensors, actuators and control laws. The control specification is stored in the configuration control file which is then invoked from the Simulator. This configuration control file, together with the system configuration file (which references the basic zone files and the active plant components), and a climate file are the only files required by the Simulator to completely describe the problem for simulation processing.

7.

If air flow within the building configuration is to be simulated by the Simulator in tandem with the energy simulation (and perhaps a zone CFD simulation), it is necessary to define the distributed building leakage and to ensure that the required pressure coefficient sets are located in a related database. Both operations are directed by the Project Manager, resulting in two further disk files: the fluid flow network and pressure coefficients files. The names of these files are given to the Simulator at the time of configuration file creation. The Simulator will now assess the pressure and temperature driven air flows for the defined zones and disregard any air change profiles (located in the corresponding zone operations file) or active zone air flow file.

8.

From within the Project Manager it is possible to check configuration geometry by computing area and volume quantities or by generating perspective displays. At this stage, it is possible to create a description of surrounding site obstructions to define the objects which will cause target zone shading.

Throughout the entire data preparation process, the Project Manager offers editing and listing operations so that mistakes can be easily rectified and hard copy records can be kept.

9.

The climate analysis module can now be used to analyse the climatic collections held on disk in the format required by ESP-r. By this mechanism, one collection is selected, and typical sequences identified, to provide boundary conditions which best stress the performance attribute to be tested.

10.

Simulations are now performed from within the Project Manager against one or more system configuration and configuration control files. Changing either of these files, or the climate file, allows different design options and control regimes to be tested under different weather influences.

11.

All results recovery and analysis is then undertaken with the help of the Results Analyser (invocable from within the Project Manager), with the principal objective of understanding the cause and effect relationships implied by the energy flowpath magnitudes and directions.

12.

Appropriate design modification can now be implemented via the Project Manager by editing a mandatory or optional zone file, the system configuration file or the configuration control file. In this way constructions can be changed, operational schemes modified, plant layout re-configured, shading devices added or removed, and so on.

2.2 General outline of program operation

A session with ESP-r might adhere to the following sequence.

Log on to the computer offering ESP-r.

Start ESP-r by issuing the command esp-r. This will start ESP-r in its default graphics mode. You can specify an alternative mode from the following list:

esp-r -mode text (text only mode with no pauses)
esp-r -mode graphic (default)

It is also possible to start up ESP-r directly with a configuration file. For example esp-r -file xxx.cfg will start ESP-r with the problem specified in the system configuration file xxx.cfg already loaded into the Project Manager.

The start-up window size can also be controlled: type esp-r -help for the required syntax.

Select commands as required from the menus displayed and thereby pick a path through the program.

Answer the questions posed at each interaction.

Eventually terminate the program by returning to the main menu and selecting the Exit command.

Delete any unwanted files; for example, zone files no longer required or results files (usually large) which have been fully analysed.

Log off after checking that any disk quotas have not been exceeded.

All program menus are hierarchical so that each menu pick will result in a particular processing option (with control returning to the same menu level), or will lead to a lower level command menu. In graphics mode, menu picks are initiated by the left mouse button. In text mode selection is by an identifier.

To questions requiring a yes/no response a user may type 1, Y, y, YES or yes and 0, N, n, NO or no. Also, after some output sequences, the program will pause to allow examination of the displayed page. The pause state is indicated by a more button at the bottom screen position. To continue click the left mouse button over the "more" button.

2.3 Data file management

In addition to the database structures essential to ESP-r’s operation (containing primitive and composite constructions, event profiles, plant components and climatic collections), the following file types may be produced in a typical session.

A mandatory geometry, construction and operation file for each zone.

An optional air flow, casual gains, shading/insulation, view factor, surface convection and transparent multi-layered construction file for some or all zones.

A mandatory system configuration file and, perhaps, a configuration control file.

Optionally, a fluid flow network description file (i.e. a leakage distribution file in the case of a building air flow network), a pressure coefficients file and a fluid flow results file (i.e. air flow results in the case of an air-only flows problem).

One or more simulation results files.

Image FIGS/grohtml-118001.png

Table 2.1 Filename convention

Effective file management can only follow from a file naming convention (largely automated by the Project Manager) in which the name itself yields information about the project and file type. In ESP-r the file type is reflected in the filename extension as indicated in Table 2.1.

Image FIGS/grohtml-118002.png

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