UNIT 7: SMOKE/HEAT DETECTOR AND SPRINKLER MODELING

1. UNIT 7:SMOKE/HEAT DETECTOR AND SPRINKLER MODELING

2. TERMINAL OBJECTIVE • Given a sample scenario, explain the related concepts of smoke/heat detector and sprinkler modeling and be able to use and evaluate such modeling with regard to the effectiveness of active fire protection systems and tenability for that scenario.

3. ENABLING OBJECTIVES The student will: • Create FDS data files that use various smoke/heat detector and sprinklers from various sets of input scenarios. • Use the FDS model and relate to the visual output of Smokeview. • Evaluate the tenability conditions affected by smoke/heat detectors and sprinkler operation.

4. DEVICES AND CONTROL LOGIC • Sprinklers, smoke detectors, heat flux gauges, and thermocouples may seem to be completely unrelated, but from the point of view of FDS, they are simply devices that operate in specific ways depending on the properties assigned to them.

5. DEVICES AND CONTROL LOGIC (con.) • They can be used to record some quantity of the simulated environment, like a thermocouple, or they can represent a mathematical model of a complex sensor, like a smoke detector, and in some cases they can trigger events to happen, like a timer.

6. DEVICES AND CONTROL LOGIC (con.) • Past versions of FDS used device specific namelist groups, like SPRK, HEAT, SMOD, and THCP, but the number and variety of fire-specific sensing and measurement devices continues to expand, and the data structures in FDS could not easily accommodate all possibilities.

7. DEVICES AND CONTROL LOGIC (con.) • In addition, the logic associated with sensor activation and subsequent actions, like a vent opening, had become too complicated and prone to bugs. Devices are now specified with a new format that streamlines and expands the possibilities of sensor profiles.

8. DEVICES AND CONTROL LOGIC (con.) • Starting in FDS 5, all devices, in the broadest sense of the word, are designated via the namelist group DEVC. In addition, advanced functionality and properties are accommodated via additional namelist groups called CTRL (Control) and PROP (Properties).

9. DEVICE LOCATION AND ORIENTATION: THE DEVC NAMELIST GROUP (TABLE 13.4) • Regardless of the specific properties, each device needs to be sited either at a point within the computational domain, or over a span of the domain, like a beam smoke detector. For example, a sprinkler is sited within the domain with a line like: • &DEVC XYZ=3.0,5.6,2.3, PROP_ID='Acme Sprinkler 123', ID='Spk_39' /

10. DEVC NAMELIST GROUP • The physical coordinates of the device are given by a triplet of real numbers XYZ. The properties of the device are contained on the PROP line PROP_ID, which will be explained below for each of the special devices included in FDS. The character string ID is merely a descriptor to identify the device in the output files, and if any action is tied to its activation.

11. DEVC NAMELIST GROUP (con.) • Not all devices need to be associated with a particular set of properties via the PROP_ID. For example, pointwise output quantities are specified with a single DEVC line, like • &DEVC ID='TC-23', XYZ=3.0,5.6,2.3, QUANTITY='TEMPERATURE' / • Which tells FDS to record the temperature at the given point as a function of time. The ID is a label in the output file.

12. DEVC NAMELIST GROUP (con.) • Some devices have a particular orientation which can be specified with various parameters; IOR, ORIENTATION, ROTATION. IOR or the Index of Orientation, is necessary for any device that is placed on the surface of a solid. The values ±1 or ±2 or ±3 indicate the direction that the device “points”, where 1 is parallel to the X axis, 2 is parallel to the Y axis, and 3 is parallel to the Z axis.

13. DEVC NAMELIST GROUP (con.) • ORIENTATION is used for devices that are not on a surface and require a directional specification, like a sprinkler. ORIENTATION is specified with a triplet of real number values that indicate the components of the direction vector. The default value of ORIENTATION is (0,0,-1).

14. DEVC NAMELIST GROUP (con.) • For example, a default downward-directed sprinkler spray can be redirected in other direction. If you were to prescribe, • &DEVC XYZ=3.0,5.6,2.3, PROP_ID='...', ID='...', ORIENTATION=1,0,0 / • The sprinkler would point in the positive x direction. For other devices, the ORIENTATION would only change the way the device is drawn by Smokeview.

15. SPECIAL DEVICES AND THEIR PROPERTIES: THE PROP NAMELIST GROUP (TABLE 13.16) • Many devices are fairly easy to describe, like a point measurement, with only a few parameters which can be included on the DEVC line. However, for more complicated devices, it is inconvenient to list all of the properties on each and every DEVC line.

16. SPECIAL DEVICES AND THEIR PROPERTIES: THE PROP NAMELIST GROUP (TABLE 13.16) • For example, a simulation might include hundreds of sprinklers, but it is tedious to list the properties of the sprinkler each time the sprinkler is sited. For these devices, use a separate namelist group called PROP to store the relevant parameters.

17. SPECIAL DEVICES AND THEIR PROPERTIES: THE PROP NAMELIST GROUP (TABLE 13.16) • Each PROP line is identified by a unique ID, and invoked by a DEVC line by the string PROP_ID. The ID might be the manufacturer’s name, like ‘ACME Sprinkler 123’, for example. The best way to describe the PROP group is to list the various special devices and their properties.

18. SPECIAL DEVICES AND THEIR PROPERTIES: THE PROP NAMELIST GROUP (TABLE 13.16) • Here is a very simple example of sprinkler: • &PROP ID='K-11', QUANTITY='SPRINKLER LINK TEMPERATURE', RTI=148., C_FACTOR=0.7, • ACTIVATION_TEMPERATURE=74., OFFSET=0.10,PART_ID='water drops', FLOW_RATE=189.3, • DROPLET_VELOCITY=10., SPRAY_ANGLE=30.,80. / • &DEVC ID='Spr_60', XYZ=22.88,19.76,7.46, PROP_ID='K-11' / • &DEVC ID='Spr_61', XYZ=22.88,21.76,7.46, PROP_ID='K-11' /

19. 11.3.3 HEAT DETECTORS • &DEVC ID='HD_66', PROP_ID='Acme Heat', XYZ=2.3,4.6,3.4 / • &PROP ID='Acme Heat', QUANTITY='LINK TEMPERATURE', RTI=132., ACTIVATION_TEMPERATURE=74. / • QUANTITY=’LINK TEMPERATURE’, as in this example, defines a heat detector, which uses essentially the same activation algorithm as a sprinkler, without the water spray.

20. 11.3.3 HEAT DETECTORS (con.) • &DEVC ID='HD_66', PROP_ID='Acme Heat', XYZ=2.3,4.6,3.4 / • &PROP ID='Acme Heat', QUANTITY='LINK TEMPERATURE', RTI=132., ACTIVATION_TEMPERATURE=74. / • Like a sprinkler, RTI is the Response Time Index in units of √m·s. ACTIVATION_TEMPERATURE is the link activation temperature in degrees C (Default 74 C). INITIAL_TEMPERATURE is the initial temperature of the link in units of C (Default TMPA).

21. Smoke Detectors/Alarms • FDS contains capabilities for ionization, photoelectric and beam detectors • General practice for spot detectors/alarms is to input both ionization and photoelectric

22. 11.3.4 SMOKE DETECTORS • A smoke detector is defined in the input file with an entry similar to: • &DEVC ID='SD_29', PROP_ID='Acme Smoke Detector', XYZ=2.3,4.6,3.4 / • &PROP ID='Acme Smoke Detector', QUANTITY='spot obscuration', LENGTH=1.8, ACTIVATION_OBSCURATION=3.28 / for the single parameter Heskestad model

23. 11.4 BASIC CONTROL LOGIC • Devices can be used to control various actions, like creating and removing obstructions, or activating and deactivating fans and vents. Every device has an associated QUANTITY, whether it is included directly on the DEVC line or indirectly on the optional PROP line.

24. 11.4 BASIC CONTROL LOGIC (con.) • Using the DEVC parameter SETPOINT, you can trigger an action to occur when the QUANTITY value passes above, or below, the given SETPOINT. The choice is dictated by the given TRIP_DIRECTION, which is just a positive or negative integer.

25. 11.4 BASIC CONTROL LOGIC (con.) SETPOINT • The value of the device at which its state changes. For a detection type of device (e.g. heat or smoke) this value is taken from the device’s PROP inputs and need not be specified on the DEVC line.

26. 11.4 BASIC CONTROL LOGIC (con.) TRIP_DIRECTION • A positive integer means the device will change state when its value increases past the setpoint and a negative integer means the device will change state when its value decreases past the setpoint. The default value is +1.

27. 11.4 BASIC CONTROL LOGIC (con.) LATCH • If this logical value is set to .TRUE. the device will only change state once. The default value is .TRUE..

28. 11.4 BASIC CONTROL LOGIC (con.) INITIAL_STATE • This logical value is the initial state of the device. The default value is .FALSE. For example, if an obstruction associated with the device is to disappear, set INITIAL_STATE=.TRUE.

29. EXAMPLE • &DEVC XYZ=1.2,3.4,5.6, ID='my clock', QUANTITY='TIME', SETPOINT=30. / • Anything associated with the device via the parameter, DEVC_ID=’my clock’, will change its state at 30 seconds. For example, if the text were added to an OBST line, that obstruction would change from its INITIAL_STATE of .FALSE. to .TRUE. after 30 s. In other words, it would be created at 30 s instead of at the start of the simulation. This is a simple way to open a door or window.

30. 11.4.1 CREATING AND REMOVING OBSTRUCTIONS • In many fire scenarios, the opening or closing of a door or window can lead to dramatic changes in the course of the fire. Sometimes these actions are taken intentionally, sometimes as a result of the fire. Within the framework of an FDS calculation, these actions are represented by the creation or removal of solid obstacles, or the opening or closing of exterior vents.

31. 11.4.1 CREATING AND REMOVING OBSTRUCTIONS (con.) • Remove or create a solid obstruction by assigning the character string DEVC_ID the name of a DEVC ID on the OBST line that is to be created or removed. This will direct FDS to remove or create the obstruction when the device changes state to .FALSE. or .TRUE., respectively.

32. EXAMPLE • &OBST XB=..., SURF_ID='...', DEVC_ID='det2' / • &DEVC XYZ=..., PROP_ID='...', ID='det1' / • &DEVC XYZ=..., PROP_ID='...', ID='det2', INITIAL_STATE=.TRUE. / • Will cause the given obstruction to be removed when the specified DEVC changes state.

33. 11.4.1 CREATING AND REMOVING OBSTRUCTIONS (con.) • Creation or removal at a predetermined time can be performed using a DEVC that has TIME as its measured quantity. • The following instructions will cause the specified HOLEs and OBSTstructions to appear/disappear at the various designated times:

34. 11.4.1 CREATING AND REMOVING OBSTRUCTIONS (con.) &HOLE XB=0.25,0.45,0.20,0.30,0.20,0.30, COLOR='RED', DEVC_ID='timer 1' / &HOLE XB=0.25,0.45,0.70,0.80,0.70,0.80, COLOR='GREEN', DEVC_ID='timer 2' / &OBST XB=0.70,0.80,0.20,0.30,0.20,0.30, COLOR='BLUE', DEVC_ID='timer 3' / &OBST XB=0.70,0.80,0.60,0.70,0.60,0.70, COLOR='PINK', DEVC_ID='timer 4' / &DEVC XYZ=..., ID='timer 1', SETPOINT= 1., QUANTITY='TIME', INITIAL_STATE=.FALSE./ &DEVC XYZ=..., ID='timer 2', SETPOINT= 2., QUANTITY='TIME', INITIAL_STATE=.TRUE. / &DEVC XYZ=..., ID='timer 3', SETPOINT= 3., QUANTITY='TIME', INITIAL_STATE=.FALSE./ &DEVC XYZ=..., ID='timer 4', SETPOINT= 4., QUANTITY='TIME', INITIAL_STATE=.TRUE. /

35. ACTIVITY 6_11ADDING SMOKE AND HEAT DETECTORS (DEVC)

36. ACTIVITY 6_12ADDING SPRINKLERS (DEVC)

37. ATRIUM EXAMPLE Using the atrium space you built in Unit 6 Evaluate smoke detector and sprinklers as proposed

38. SUMMARY