Energy Systems Research UnitESP-r Glossary


Air balance refers to the energy balance on an air node. The only method of heat transfer to an air node is via convection (e.g. from surfaces, ventilation casual gains or from heating).
Air flow is the movement of air within or between zones and can be quantified as :
  • ACH (air changes per hour) with respect to the volume of a zone;
  • A mass flow network entailing a more detailed analysis with defined components of flow rate and direction within and between zones; and
  • A CFD (computational fluid dynamics) network of even higher resolution within zones where they are split into many nodes, pressures and momentums.
Air Changes per Hour - unit used for quantifying default infiltration and ventilation rates, as well as a reporting unit of the mass flow analysis.
boundary condition
These are the temperature, flux and other environmental conditions that pertain on either side of a surface. According to the particular surface, they may be obtained from the climate data file, from the calculated values in an adjacent zone, or from user-specified values.
composite construction
This refers to a type of database and its contents which are made of one or more layers of primitive materials. A composite construction may be opaque or transparent. In the latter case additional information on its optical properties is incorporated. Sample composite databases are supplied in /usr/esru/esp-r/databases which the user may wish to copy and extend. Depending on the type of simulations carried out the user may wish to build a different composite database for each project or develop one which contains a variety of constructions and is useful for a range of simulations.
The topology of a problem is defined via the boundary conditions defined for each surface. These may be defined via two mechanisms: firstly, as a surface attribute (which can be imported into the overall problem description) or secondly, as a connection (located in the problem description file, which may then the exported as a surface attribute). The networks which define plant and mass flow networks also contain connection lists.
control law
A number of items which are subject to control (depending on time, temperature, radiation etc) can exhibit specific characteristics via the use of control laws. For example lighting casual gains may be switched ON/OFF, step, proportional and proportional with constant ballast loads.
Controller type
In ESP-r, the controller type controls the actuated property sensed by the sensor and actuated by the actuator.
control function
Generally, this term is used for the operations carried out by an automatic control system. However, in ESP-r, the BUILDING control strategy is comprised of one or more control functions. They are then associated with the building zones to define the time-dependent control objectives. A PLANT system, on the other hand, is governed by one or more control loops. In essence, control functions and and control loops are the same, differing only in the types of control laws used to link the sensorand actuator.
control law
In ESP-r, this defines a control algorithm which represents the logic or "control action" of a controller. For example, the control law implemented may be PID control.
control loop
Generally, this term means any control network consisting of the control elements required for automatic control. However, in ESP-r, this term is reserved for those control loops which govern the PLANT network control system - the BUILDING control strategy comprising of one or more control functions. The control loop comprises of three control elements:- a sensor, a controller, and an actuator. For example, a plant network may consist of an air-handling unit supplying hot air to one zone, and cold air to a second zone. An ESP-r control loop for this system could be:- a SENSOR located i n the centre of the zone to measure the air temperature; a CONTROLLER (with PID control action) to determine a correction signal such as to reduce the magnitude of the error signal (measured value - desired value); and an ACTUATOR to receive this signal, and operate the final control element (in this case, a throttling valve in the heating/cooling coil's hot/cold water supply line). Thus, if the measured zone temperature is not equal to the desired value, the air supplied to the zone will receive an increase in energy from the coil in accordance with the PID algorithm.
default insolation
User supplied static insolation distribution (as opposed to dynamic shading and insolation patterns found via the shading and insolation program).
default window
A default window is a simplified treatment of glazing which is retained as a pragmatic expedient.
diffusion resistance factor (DRF)
Within the ESP-r materials database, the "diffusion res." is the diffusion resistance factor (DRF), a dimensionless number :
  • DRF = permeability of air / permeability of material. Permeability is also referred to as "vapour diffusivity". The DRF values are converted internally into vapour resistances by :
    vapour resistance = (DFR * thickness)/19.2e-11 where air permeability is 19.2e-11 kg/(m.s.Pa).
  • Materials which have a very low or zero permeability (e.g. glass, metal, etc.) are represented in the database with the value 19200.
Infiltration is the movement of air from the outside.
leakage distribution
Term used in the past for network description of mass flows.
mass flow component
Mass flow resistance (duct, opening, valve) or inducer (fan, pump, constant volume) defined and used within a mass flow network.
mass flow connection
Topology of the network in the form of:.
mass flow node
A point within a mass flow network, normally associated with a thermal zone or a boundary orientation.
mean radiant temperature
Sensors may be set to MRT which is equivalent to the reading from a black body globe thermometer.
Obstruction introduces time-varying shading and insolation which must be taken into consideration when calculating the building thermal and lighting performance. In shading calculations the effects of fins, trees, other buildings and walls are approximated by one or more obstruction blocks. There are several rules for the composition and placement of obstruction blocks :
  1. they should not be in the same plane as the surface being obstructed (a few mm of clearance is required)
  2. it is best not to cross the plane of a surface which might be shaded; use 2 blocks in such cases.
  3. the blocks should be named so that they can be tracked more easily.
Casual gains, ventilation and infiltration patterns for a thermal zone are held in a zone operation file in the form of diary entries with an associated control syntax. A mass flow simulation will take precedence over the infiltration and ventilation specifications. A timestep casual gain file will take precedence over the diary specification.
plant component
Device within a plant network such as a boiler or pump.
plant connection
Topology of plant network.
plant containment
Boundary conditions of a plant component which may or may not interact with a thermal zone.
preconditioning period
One or more days of simulation before the requested simulation period. These are required to remove any effects that may result from the assumed initial conditions of the simulation. Calculated values during the preconditioning period (or start-up period) are not saved.
predicted percentage dissatisfied (PPD)
Comfort rating derived from the work of Fanger.
predicted mean vote (PMV)
Comfort rating derived from the work of Fanger.
primitive materials
This is a type of database which holds the thermophysical properties of basic materials such as aluminium, limestone, and concrete which can be combined to form composite constructions. One database (/usr/esru/esp-r/databases/constr.db1) is supplied with the system, but the user may wish to copy this to form custom versions.
problem configuration
This is the core description of a problem which contains references to the various geometry, scheduling, mass flow network, plant and thermophysical property files which constitute the description of a problem. It is often referred to as the system configuration file in the ESP-r user manual.
This includes the latitude, longitude, average ground reflectance as well as an index to the exposure of a specific location. Site information resides in the problem configuration file. Climatic patterns are taken from one or several climate databases which are representative of particular regions.
A surface is a polygon with associated attributes such as emissivity, area, orientation and a specific composite construction. Surfaces have two sides, one facing the zone (inside) and the other connected to a boundary condition (another zone, ground, outside). It interacts both radiantly and convectively with its environment. A surface may be opaque or transparent. It may also include "default" windows, which are simplified treatments of glazing but which a user may find convenient to use. The description of the layers of the composite construction associated with a surface is from the outside to the inside. If the surface is a partition composed of a non-symmetrical composite construction, the user will need to define two composites, with one defined in reverse order to the other.
system control
This file contains the definition of the controls which act on the building and the plant.
thermal zone
This is a volume of air which is assumed to be well mixed and bounded by closed polygons. This is the primary reporting and descriptive unit of ESP-r and may be used to represent a range of spaces which are a direct mapping from reality, e.g. a room, a portion of a room or a concatenation of several rooms. This concept is often confusing to novice users, however, because the user defines what a zone is. The part of a building (or other space) represented by a zone may vary according to the aims of the particular simulation study, and it requires experience to determine how a particular problem might best be abstracted.
TMC / transparent composite
Glazing may be described as a composite construction with full accounting of radiant exchange, thermal storage and the like. Each composite construction which is tagged as being transparent will have an associated set of optical properties. It is possible to change optical properties as a function of time and radiation level. The ability to alter thermophysical properties will be available in the near future.
Ventilation refers to air movement between zones.