CN106777591A - Prediction model for predicting response time of closed sprinkler head or temperature-sensitive detector - Google Patents
Prediction model for predicting response time of closed sprinkler head or temperature-sensitive detector Download PDFInfo
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Abstract
The invention relates to a prediction model for predicting response time of a closed sprinkler head or a temperature-sensitive detector, and belongs to the technical field of fire prevention. The method comprises the steps of basic assumption, model basic principle setting, fire design, response time prediction and the like, a prediction model is established for the response time of the sprinkler head or the temperature-sensitive detector under different fire conditions, a technical means is provided for building fire protection design to carry out evacuation starting time prediction and fire scale prediction, the prediction of the response time of the closed sprinkler head or the temperature-sensitive detector under the fire condition can be completed, the method is suitable for different types of fires, the nationalization of the prediction model is realized, software designed by adopting the model principle can be operated on a Chinese WIDOWS interface, and the usability and the comparison correctness of a prediction model tool are realized.
Description
Technical field
The present invention relates to a kind of forecast model, during the response of particularly a kind of prediction sealed sprinkler head or heat detector
Between forecast model, belong to fireproofing technique field.
Background technology
Automatic sprinkler system has the history of more than 100 years so far from being born, and it protects human life in a fire
And property safety aspect played an important role.The purpose of automatic sprinkler system is set primarily to effectively putting out a fire to save life and property just
Phase fire or control fire scale.For sprinkler tip for the automatic sprinkler system of enclosed will realize that quick startup controls fire
With stamp out a fire, it is a key factor that can sprinkler tip act in time, for whole automatic sprinkler system fire extinguishing control fire effect
It is most important.Sealed sprinkler head can not such as be heated opening in time, then the watering after shower nozzle is opened may not cover model on fire
Enclose, fire spreads outside spray field, do not reach design effect.
The factor that influence sprinkler tip starts the time is a lot, including shower nozzle response time index (RTI), response temperature, peace
Dress height, fire development speed etc., the change of these factors may all influence the actuation time of sprinkler tip.
With the application and development of special fire protection design method, show for prediction shower nozzle response time and prediction fire scale
Must be even more important.Foreign countries have carried out developmental research, such as DETACT-QS to sprinkler tip or detector response time model,
DETQCT-T2 and LAVENT etc., these models can be used to calculate the response of the sprinkler tip for being exposed to fire hazard environment or detector
Time, it can also be used between predicting at the beginning of fire scale and evacuating personnel.
Generally, sprinkler tip or detector RTI, response temperature, setting height(from bottom) and shower nozzle are made apart from the radius etc. of burning things which may cause a fire disaster
It is |input paramete.Fire scale and the relation of time and fire sustainable development time must be provided by user, generally started and spilt
The thermal source of sprinkler head or detector comes from ceiling jet, does not consider the formation of hot layer in compartment.It is the same with other programs,
The hypothesis situation of inherence is not known about such as, and these programs may be misapplied.
Have been set up in the world with fire modeling, automatic sprinkler heat sensitivity energy and thermal conduction study etc. as theoretical foundation, in advance
The method that shower nozzle starts the time is surveyed, its method has turned into the important component of special fire protection design technology.On automatic sprinkler
The research of startup time, China is same in terms of predicting means, Forecasting Methodology and data analysis and utilization etc. all also to deposit in the world
In a certain distance.Special fire protection design and Fire danger assessment are also just progressively being applied and are developing in China, equally urgently
Similar applicable forecast model need to be developed.
The content of the invention
Based on drawbacks described above, the present invention proposes a kind of response time for predicting sealed sprinkler head or heat detector
Forecast model is fire protection design and Fire danger assessment work, carry out the prediction of evacuation time started and fire scale prediction
There is provided corresponding technological means, efficiently solve the problems, such as that the fire response time is predicted.
Technical scheme is as follows：
A kind of forecast model of the response time for predicting sealed sprinkler head or heat detector, comprises the following steps：
Step one：Basic assumption
The forecast model is based on following 3 basic assumption conditions：
(1) shower nozzle or heat detector are in one piece of large space and are arranged on flat ceiling by related specifications requirement
Under；
(2) in the initial period of fire development, radiations heat energy transmittance process is ignored, convective heat transfer speed qconvIt is influence
Shower nozzle or the principal element of heat detector response；
(3) convection heat carry-over factor with flow through the gas velocity of heat-sensitive element in shower nozzle or heat detector into than
Example；
Step 2：MODELSRationale
The fire plume temperature and speed for flowing through shower nozzle are predicted using flame and ceiling jet model, wherein, shower nozzle or
Heat transfer between heat detector and surrounding environment is using the total heat transfer rate q of unittotalExpression, qtotalUnder
Row relational expression is represented：
In above formula：
qcond--- conduction heat transfer speed；
qconv--- convective heat transfer speed；
qrad--- radiation heat transfer rate
Heat is stated by the transfer rate that advection heat reaches shower nozzle or heat detector using following formula：
In above formula：
H --- convection heat carry-over factor, unit kW/ (m2DEG C) or Btu/ (sft2·℉)；
A --- heat transfer area (m2)；
Td--- shower nozzle or heat detector temperature (DEG C)；
Tδ--- the maximum (DEG C) of fire gases temperature near ceiling；
Shower nozzle or heat detector heat-sensitive element are regarded as the entirety that one piece of quality is m, its temperature change can be under
Formula draws：
In above formula：
The specific heat of c --- heat-sensitive element, unit is kJ/ (kg DEG C) or Btu/ (1bm ℉)；
The relational expression that shower nozzle or heat detector heat-sensitive element temperature are changed over time can be derived by above-mentioned equation：
If
Wherein, τ is the convection heat of the heat-sensitive element for reaching given；
So,
The fire gases temperature given for one, speed and specific heat-sensitive element, quality increase, the increase of τ values；τ
Value shows that more greatly temperature-sensing element heat transfer rate is slower；
Convection heat carry-over factor h is the function relevant with the gas velocity and component shape by heat-sensitive element, right
One given heat-sensitive element, h is proportional to the gas velocity for flowing through heat-sensitive element, and this relation is to use heat-sensitive element
Distinctive response time index --- RTI is represented：
In above formula：
The maximum of fire gases speed near u --- ceiling；
uo--- gas reference speed under laboratory condition；
The convection heat of τ --- heat-sensitive element；
τo--- corresponding τ values during gas reference speed；
Using insertion experiment it is used for determining the RTI values of shower nozzle or heat detector, it is known that RTI values, fire gases is led to
The temperature change for crossing similar heat-sensitive element any time can learn that its heat diffusivity equation is as follows by calculating：
Above-mentioned formula 8 is used for the temperature of constant temperature heat detector or shower nozzle of the predicted exposure in fire gases, Huo Zheyong
To determine that temperature-sensing element reaches the time of its operating temperature；
Step 3：Designing peak flow
Designing peak flow is divided into the fire and the constant fire of HRR that HRR increases with the time；
(1) fire that HRR increases with the time
At the initial stage and rise period of actual fire, HRR constantly increases with the passage of time, it is most of it is common can
When combustion things are caught fire, heat release rate increases the square law of the time that follows, so be also called time square fire, i.e.,：
Q=at2(formula 9)
In formula：
Q --- heat release rate (kW)；
A --- time constant；
T --- the time (s)
(2) the constant fire of HRR
Also assumed using the fire that HRR is constant when Building Fire Protection security evaluation is carried out and smoke evacuation system is designed
HRR is to be maintained at a certain numerical value since on fire, and this numerical value is taken as peak value HRR during combustible combustion
Or the HRR of burning things which may cause a fire disaster during water sprinkler system startup, the growth bound of fire is have ignored due to the constant fire of HRR
Section, thus used when conservative design need to be compared；
Step 4：Response time is predicted
(1) shower nozzle under stable state fire fire conditions or the prediction of heat detector response time
For stable state fire, using a series of following calculating fire gases temperature and speed in ceiling injection stream
Equation, as the heat rate of release and the function of position of stable state fire：
Work as r/H>When 0.18：
When r/H≤0.18：
Work as r/H>When 0.15：
When r/H≤0.15：
Wherein, Tδ--- the maximum (DEG C) of fire gases temperature near ceiling；
Ta--- ambient temperature (DEG C)；
Q --- total fire heat release rate (kW)；
R --- apart from the horizontal range (m) of flame axis；
H --- the height (m) above ignition point；
The maximum (m/s) of fire gases speed near u --- ceiling；
Assuming that the fire gases temperature and speed of leaving ignition point somewhere are relevant with the moment heat release rate of burning things which may cause a fire disaster, suddenly
Time slightly needed for temperature-sensing element to fire gases flowing between burning things which may cause a fire disaster, while, it is considered to total heat release rate and not only
It is convection heat rate of release；
For the gas temperature constant to and gas velocity, basic heat transfer equation is：
Or obtain RTI substitution formula 15：
It is constant ceiling injection stream for gas temperature and speed, or reaction of the heat detector to fire can make
It is simulated with equation above 14-16 and is analyzed；
Shower nozzle response time trPrediction can use below equation：
(2) fire or half stable state fire fire conditions lower nozzle or the prediction of heat detector response time are developed
One fire for developing by assuming that its by a series of continuous increases stabilization heat release rate fire
Constitute and simulate, using this model as semisteady-state model, be first by heat release rate curve be divided into it is a series of very
Short time interval, to each interval, with this it is intersegmental every average HRR come calculate fire produce gas temperature
And speed, can so calculate shower nozzle or heat detector here every temperature and speed；
Step 5：Forecast model completes the prediction to automatic sprinkler or heat detector response time in case of fire.
Further, in the step 3 (1), the time constant that different combustible fire increases is different, is discharged by heat
Time square fire is divided into four classes, i.e., ultrafast, quick, middling speed and at a slow speed fire by the speed that speed increases.
Further, the typical time constant of the four classes time square fire is as follows：
The typical time constant of 1 time square of table fire
Technical scheme achieves following technique effect：
The sprinkler tip response time is to be directly connected to whether initial fire disaster can be subject to by effectively putting out with fire spread
One important factor in order of control, the present invention has filled up domestic and has lacked exploitativeness side on the prediction sprinkler tip response time
The blank of method.
The present invention sets up forecast model to the response time of sprinkler tip or heat detector under different fire conditions, to build
Build fire protection design and the prediction of evacuation time started and fire scale prediction offer technological means are provided, can complete to automatic sprinkler
Or the prediction of heat detector response time in case of fire, it is adaptable to different types of fire, realize forecast model
Nationalization, the software designed using the modular concept is operable at Chinese WIDOWS interfaces, and realizes the easy of forecast model instrument
The property used.
One aspect of the present invention helps to improve scientific research level of the means of testing to improve product, and it is special on the other hand to contribute to
The development of fire protection design work, can meet supervision and the demand for services of manager, user and product development person, with larger
Application space.
Brief description of the drawings
Fig. 1 is fire development rule sketch；
Fig. 2 is the software operational flowchart using forecast model of the present invention design；
Fig. 3 is to start surface chart using the software of forecast model of the present invention design；
Fig. 4 is the software |input paramete surface chart using forecast model of the present invention design；
Fig. 5 is the output result surface chart using forecast model of the present invention design；
Fig. 6 is on surface chart using forecast model of the present invention design；
The output result surface chart of Fig. 7 examples 1；
The |input paramete surface chart of Fig. 8 examples 2；
The output result surface chart of Fig. 9 examples 2；
The output result surface chart of Figure 10 examples 3；
The output result surface chart of Figure 11 examples 4.
Specific embodiment
The present invention will be further described below in conjunction with the accompanying drawings.
As shown in figures 1 to 6, a kind of prediction mould of the response time for predicting sealed sprinkler head or heat detector of the present invention
Type, comprises the following steps：
Step one, basic assumption
Automatic sprinkler system automatic sprinkler has the dual-use function of heat detection and cloth above-water method, heat detector
Forecasting Methodology is identical with the response time Forecasting Methodology of automatic sprinkler.The forecast model that the present invention sets up is based on following 3
Individual basic assumption condition：
(1) shower nozzle or heat detector are in one piece of large space and are arranged on flat ceiling by related specifications requirement
Under.Ceiling high can bring the more surrounding airs, this situation will to make gas cooling when meaning that flame rises.Beam,
Stringer, wall or inclined ceiling can all change the flowing of heat smoke, and this situation will suppress or accelerate the dynamic of heat-sensitive element
Make.
(2) in the initial period of fire development, radiations heat energy transmittance process is ignored.Temperature-sensitive element passes through heat transfer by heat
The thermal loss at other positions and ceiling for reaching shower nozzle is inappreciable, therefore convection current compared with the heat of convection current
Heat transfer speed (qconv) turn into the principal element that influence shower nozzle or heat detector are responded.
(3) convection heat carry-over factor is proportional to the gas velocity for flowing through heat-sensitive element.
Step 2, general principle
The shower nozzle given for one, problems faced is just to determine the set location that shower nozzle can be responded by design requirement
(from the maximum distance of ignition point).This needs a kind of according to fire size, fire development situation, heights of ceilings and shower nozzle
Thermo-responsive characteristic is come the method for predicting its actuation time.
Flame and ceiling jet model can be used to predict the fire plume temperature for flowing through shower nozzle and speed, shower nozzle or temperature-sensitive
Heat transfer between detector and surrounding environment can be using the total heat transfer rate q of unittotalExpression, qtotalCan be with following
Relational expression is represented：
In above formula：
qcond--- conduction heat transfer speed；
qconv--- convective heat transfer speed；
qrad--- radiation heat transfer rate
In the initial period of fire development, radiations heat energy transmission can be ignored.Meanwhile, the thermo-responsive unit of most of commercialization shower nozzle
Part is heat-insulated with unit remainder, and heat is reached heat-sensitive element the heat of shower nozzle other parts and ceiling by conduction
Amount loss is insignificant compared with the heat of convection current, therefore convection heat transfer' heat-transfer by convection transfer rate (qconv) turn into influence shower nozzle temperature-sensitive
The principal element of sensing unit.Heat can be stated by the transfer rate that advection heat reaches shower nozzle with following formula：
In above formula：
H --- convection heat carry-over factor, unit kW/ (m2DEG C) or Btu/ (sft2·℉)；
A --- heat transfer area (m2)；
Td--- shower nozzle or heat detector temperature (DEG C)；
Tδ--- the maximum (DEG C) of fire gases temperature near ceiling
Shower nozzle or heat detector heat-sensitive element are regarded as the entirety that one piece of quality is m, its temperature change can be under
Formula draws：
In above formula：
The specific heat of c --- heat-sensitive element, unit is kJ/ (kg DEG C) or Btu/ (1bm ℉)
The relational expression that shower nozzle or heat detector heat-sensitive element temperature are changed over time can be derived by above-mentioned equation：
The convection heat of the heat-sensitive element for describing to reach given using a constant time, relational expression is as follows：
So,
The fire gases temperature given for one, speed and specific heat-sensitive element, quality increase, the increase of τ values；τ
Value shows that more greatly temperature-sensing element heat transfer rate is slower.
Convection heat carry-over factor is the function relevant with the gas velocity and component shape by heat-sensitive element.To one
Individual given heat-sensitive element, h is substantially proportional to the gas velocity for flowing through heat-sensitive element, and this relation is to use thermo-responsive unit
The distinctive response time index of part --- RTI is represented.
In above formula：
The maximum of fire gases speed near u --- ceiling；
uo--- gas reference speed under laboratory condition；
The convection heat of τ --- heat-sensitive element；
τo--- corresponding τ values during gas reference speed
It is worth noting that, RTI is used as a heat transfer function being simplified, that is, assume that τ is
Square root to gas velocity is proportional, and air-flow passes through right and wrong during the object of this irregular shape of such as detector and shower nozzle
Often complicated.
Another hypothesis is that nozzle temperature sensing element does not occur heat transfer with body in heat transfer model, one
In individual insertion experiment, because speed is higher, the thermal loss of heat transfer can be ignored.Under actual Fire Conditions, this
Planting conduction thermal loss will cause certain error.
Insertion experiment (is techniques well known, referring to GB 5135.1-2003《Automatic sprinkler system part 1
Sprinkler tip》) may be used to determine the RTI values of heat detector or shower nozzle, it is known that RTI values, to fire gases by similar unit
The temperature change of part any time can be learnt by calculating.Heat diffusivity equation is as follows：
This equation is used for the temperature of constant temperature heat detector or shower nozzle of the predicted exposure in fire gases, it is also possible to
For determining that temperature-sensing element reaches the time of its operating temperature.
To calculate the response time of shower nozzle, the gas flow temperature and speed that acquisition flows through shower nozzle are necessary, can be utilized
Flame model or ceiling jet model obtain temperature and speed.
The height of temperature and velocity variations same distance ceiling is not constructed function by most of flame and ceiling jet model.
This hypothesis may cause the uncertainty of result.
Step 3, designing peak flow
Another input condition related to the prediction of shower nozzle response time is designing peak flow situation.Designing peak flow is generally divided into
Fire and the constant fire of HRR that HRR increases with the time.
(1) fire that HRR increases with the time (referring to Fig. 1)
At the initial stage and rise period of actual fire, HRR constantly increases with the passage of time, it is most of it is common can
When combustion things are caught fire, HRR increases the square law of the time that follows, so be also called time square fire, i.e.,：
Q=at2(formula 9)
In formula：
Q --- HRR (kW)；
A --- time constant；
T --- the time (s)
The time constant that different combustible fire increases is different, and the speed increased by HRR will generally be put down the time
Square fire is divided into four classes, i.e., ultrafast, quick, middling speed and at a slow speed fire.The fire of the flammable liquids such as usual gasoline shows as ultrafast fire, one
As the fire that occurs of the more place of the upholstered furniture such as hotel guest room be quick fire, office's fire can be with middling speed is fiery or quick fire
Characterize.The typical time constant of this four classes time square fire is as follows：
The typical time constant of 1 time square of table fire
(2) the constant fire of HRR
It is when Building Fire Protection security evaluation is carried out and smoke evacuation system is designed also frequently with the fire that HRR is constant, i.e., false
The fixed HRR since on fire is to be maintained at a certain numerical value.This numerical value is often taken as peak heat release during combustible combustion
The HRR of burning things which may cause a fire disaster when speed or water sprinkler system start.The increasing of fire is have ignored due to the constant fire of HRR
Stage long, thus Chang Xu used when being compared conservative design.
Step 4, response time prediction
(1) shower nozzle under stable state fire fire conditions or the prediction of heat detector response time
For stable state fire, using a series of following calculating fire gases temperature and speed in ceiling injection stream
Equation, as the heat rate of release and the function of position of stable state fire.
Work as r/H>When 0.18：
When r/H≤0.18：
Work as r/H>When 0.15：
When r/H≤0.15：
In a series of equation above：
Tδ--- the maximum (DEG C) of fire gases temperature near ceiling；
Ta--- ambient temperature (DEG C)；
Q --- total fire heat release rate (kW)；
R --- apart from the horizontal range (m) of flame axis；
H --- the height (m) above ignition point；
The maximum of fire gases speed, unit m/s near u --- ceiling；
This model hypothesis leaves the fire gases temperature and speed in ignition point somewhere and the moment heat release speed of burning things which may cause a fire disaster
Rate is relevant.This hypothesis have ignored temperature-sensing element to the required time of fire gases flowing between burning things which may cause a fire disaster, meanwhile, consider in formula
Total heat release rate and not exclusively convection heat rate of release.
For the gas temperature constant to and gas velocity, basic heat transfer equation is：
Or obtain RTI substitution equations：
It is constant ceiling injection stream for gas temperature and speed, reaction of the shower nozzle to fire can use above
Equation is simulated analysis.Shower nozzle response time trPrediction can use below equation.
(2) fire or half stable state fire fire conditions lower nozzle or the prediction of heat detector response time are developed
One fire for developing can with by assuming that its by a series of continuous increases stabilization heat release rate
Fire constitutes to simulate, using this model as semisteady-state model.First it is that heat release rate curve is divided into one to be
The very short time interval of row, to each interval, with this it is intersegmental every average HRR calculate the gas that fire is produced
Temperature and speed, can so calculate shower nozzle here every temperature and speed.
Step 5：Forecast model completes the prediction to automatic sprinkler or heat detector response time in case of fire.
Corresponding software is programmed and designed using the forecast model
1) function
Forecast model can complete the prediction to automatic sprinkler or heat detector response time in case of fire, be applicable
In different types of fire：
Automatic sprinkler or the prediction of heat detector response time in the case of stable state fire；
Different T2Automatic sprinkler or heat detection in the case of development fire (developing fire, middling speed, quick, supper-fast etc. at a slow speed)
The device response time is predicted.For development fire, predicted time interval is optional.
2) contrast test
The external existing shower nozzle response time computation model being widely recognized as have DETACT-QS, DETACT-T2, LAVENT,
ASET-B and Sprink 1.0.DETACT-QS is used for the softwares such as FIREFORM, FPETOOL and HAZARD.
Forecast model of the invention predicts the outcome will be contrasted with predicting the outcome for DETACT-QS, check its reliability.
3) main feature
Forecast model is set up using the developing instruments of VISUAL BASIC 6.0, and using WINDOWS interfaces, strong applicability makes
With simple, it is easy to operate, control.
File record is carried out using to data file, it is ensured that the security of initial data.
Predicted time interval is optional, the flexibility that increase is used.
Realize encryption handling：User into prognosis modelling function must be legal, each validated user pair
Only one user cipher is answered, therefore user need to provide user cipher, can use the forecast model.
Work of the invention and calculating process, are described as follows with example：
1) constant fiery application example
A 4m below one piece of 6m flat smallpox high2Oil sump just in ignition, the temperature of surrounding is 20 DEG C.One
The individual heat detector on plate of blooming, its RTI is 55m1/2·s1/2, temperature rating is 57 DEG C.If it be located at from
Ignition point 6m remote place, predicts the response time of detector.
Answer：The chemical heat of oil firing is 40.3kJ/g, and the convection heat of burning is 26.2kJ/g, account for total amount of heat
65%.To Alpert relational expressions, it is necessary to use total heat release rate, that is, the total amount of heat burnt.Oil firing speed is about
67g/m2·s.Therefore total HRR is about 10800kW.It is t to predict the outcomer=12s, is shown in Fig. 7.
2) the quick square of fiery application example of development
The a pile plank ignition below one piece of 6m flat smallpox high, the rate of release of heat presses quick T2Fire hair
Exhibition, the temperature of surrounding is 20 DEG C.The shower nozzle under ceiling is installed on, its RTI value is 55m1/2·s1/2, desired temperature is 68
DEG C, the positive square of shower nozzle is installed, and spacing is 3.6m, predicts the shower nozzle response time.
Answer：It is predicted with 10s intervals, |input paramete is shown in Fig. 8, and it is 180s to predict the outcome, fire hazard thermal release now
Speed is 1519kW, predicts the outcome and sees Fig. 9 and Biao 2.
The example 2 of table 2 predicts the outcome table
The above results obtain following result by the prediction of FPETOOL (DETECT-QS models) instrument：The shower nozzle response time is
180s, fire heat release rate is 1510kW, and gas temperature is 84 DEG C.
Understand by contrast, in addition to fire heat release rate slightly has difference, other data fit like a glove above-mentioned data.
3) the fiery application example of middling speed square development
A furniture ignition below one piece of 6m flat smallpox high, the rate of release of heat presses middling speed T2Fire development,
The temperature of surrounding is 20 DEG C.The shower nozzle under ceiling is installed on, its RTI value is 55m1/2·s1/2, desired temperature is 68 DEG C, spray
The positive square of head is installed, and spacing is 3.6m, predicts the shower nozzle response time.
Answer：It is predicted with 10s intervals, it is 320s to predict the outcome, fire heat release rate now is 1200kW, in advance
Survey result and see Figure 10 and Biao 3.
The example 3 of table 3 predicts the outcome table
The above results obtain following result by the prediction of FPETOOL (DETECT-QS models) instrument：The shower nozzle response time is
320s, fire heat release rate is 1198kW, and gas temperature is 75 DEG C.
Understand by contrast, above-mentioned data are coincide substantially.
4) the at a slow speed square fiery application example of development
A small-sized furniture ignition below one piece of 6m flat smallpox high, the rate of release of heat is by T at a slow speed2Fire hair
Exhibition, the temperature of surrounding is 20 DEG C.The shower nozzle under ceiling is installed on, its RTI value is 55m1/2·s1/2, desired temperature is 68
DEG C, the positive square of shower nozzle is installed, and spacing is 3.6m, predicts the shower nozzle response time.
Answer：It is predicted with 10s intervals, it is 610s to predict the outcome, fire heat release rate now is 1090kW, is surveyed
Test result is referring to Figure 11 and Biao 4.
The example 4 of table 4 predicts the outcome table
The above results obtain following result by the prediction of FPETOOL (DETECT-QS models) instrument：The shower nozzle response time is
610s, fire heat release rate is 1091kW, and gas temperature is 71 DEG C.
Understand by contrast, above-mentioned data fit like a glove, it was demonstrated that the correctness and validity of the application forecast model.
Claims (3)
1. a kind of forecast model of the response time for predicting sealed sprinkler head or heat detector, it is characterised in that including such as
Lower step：
Step one：Basic assumption
The forecast model is based on following 3 basic assumption conditions：
(1) shower nozzle or heat detector are in one piece of large space and are arranged on flat ceiling by related specifications requirement；
(2) in the initial period of fire development, radiations heat energy transmittance process is ignored, convective heat transfer speed qconvIt is influence shower nozzle
Or the principal element of heat detector response；
(3) convection heat carry-over factor is proportional to the gas velocity for flowing through heat-sensitive element in shower nozzle or heat detector；
Step 2：MODELSRationale
The fire plume temperature and speed for flowing through shower nozzle are predicted using flame and ceiling jet model, wherein, shower nozzle or temperature-sensitive
Heat transfer between detector and surrounding environment is using the total heat transfer rate q of unittotalExpression, qtotalUsing following pass
It is that formula is represented：
In above formula：
qcond--- conduction heat transfer speed；
qconv--- convective heat transfer speed；
qrad--- radiation heat transfer rate
Heat is stated by the transfer rate that advection heat reaches shower nozzle or heat detector using following formula：
In above formula：
H --- convection heat carry-over factor, unit kW/ (m2DEG C) or Btu/ (sft2·℉)；
A --- heat transfer area (m2)；
Td--- shower nozzle or heat detector temperature (DEG C)；
Tδ--- the maximum (DEG C) of fire gases temperature near ceiling；
Shower nozzle or heat detector heat-sensitive element are regarded as the entirety that one piece of quality is m, its temperature change can be obtained by following formula
Go out：
In above formula：
The specific heat of c --- heat-sensitive element, unit is kJ/ (kg DEG C) or Btu/ (1bm ℉)
The relational expression that shower nozzle or heat detector heat-sensitive element temperature are changed over time can be derived by above-mentioned equation：
If
Wherein, τ is the convection heat of the heat-sensitive element for reaching given；
So,
The heat-sensitive element given to one, h is proportional to the gas velocity for flowing through heat-sensitive element, and this relation is to use temperature-sensitive
The distinctive response time index of sensing unit --- RTI is represented：
In above formula：
The maximum of fire gases speed near u --- ceiling；
uo--- gas reference speed under laboratory condition；
The convection heat of τ --- heat-sensitive element；
τo--- corresponding τ values during gas reference speed；
The RTI values of shower nozzle or heat detector are determined using insertion experiment, fire gases is appointed by similar heat-sensitive element
The temperature change of one time can learn that its heat diffusivity equation is as follows by calculating：
Above-mentioned formula 8 is used for the temperature of constant temperature heat detector or shower nozzle of the predicted exposure in fire gases, or for true
Determine the time that temperature-sensing element reaches its operating temperature；
Step 3：Designing peak flow
Designing peak flow is divided into the fire and the constant fire of HRR that HRR increases with the time；
(1) fire that HRR increases with the time
At the initial stage and rise period of actual fire, HRR constantly increases with the passage of time, and HRR increases abides by
The square law of time is followed, so be also called time square fire, i.e.,：
Q=at2(formula 9)
In formula：
Q --- heat release rate (kW)；
A --- time constant；
T --- the time (s)
(2) the constant fire of HRR
Also assumed using the fire that heat release rate Q is constant when Building Fire Protection security evaluation is carried out and smoke evacuation system is designed
HRR is to be maintained at a certain numerical value since on fire, and this numerical value is taken as peak value HRR during combustible combustion
Or the HRR of burning things which may cause a fire disaster during water sprinkler system startup；
Step 4：Response time is predicted
(1) shower nozzle under stable state fire fire conditions or the prediction of heat detector response time
For stable state fire, using a series of following sides that fire gases temperature and speed are calculated in ceiling injection stream
Formula, as the heat rate of release and the function of position of stable state fire：
Work as r/H>When 0.18：
When r/H≤0.18：
Work as r/H>When 0.15：
When r/H≤0.15：
Wherein, Tδ--- the maximum (DEG C) of fire gases temperature near ceiling；
Ta--- ambient temperature (DEG C)；
Q --- total fire heat release rate (kW)；
R --- apart from the horizontal range (m) of flame axis；
H --- the height (m) above ignition point；
The maximum (m/s) of fire gases speed near u --- ceiling；
Assuming that the fire gases temperature and speed of leaving ignition point somewhere are relevant with the moment heat release rate of burning things which may cause a fire disaster, ignore sense
Time needed for warm element to fire gases flowing between burning things which may cause a fire disaster, while, it is considered to total heat release rate and it is not exclusively right
Stream heat release rate, then for the gas temperature constant to and gas velocity, basic heat transfer equation is：
Or obtain RTI substitution formula 15：
Be constant ceiling injection stream for gas temperature and speed, or reaction of the heat detector to fire can use it is upper
The equation 14-16 in face is simulated analysis；
Shower nozzle response time trPrediction can use below equation：
(2) fire or half stable state fire fire conditions lower nozzle or the prediction of heat detector response time are developed
One fire for developing is by assuming that it is made up of a series of heat release rate fire of the stabilization of continuous increases
First it is that heat release rate curve is divided into a series of very short using this model as semisteady-state model to simulate
Time interval, to each interval, with this it is intersegmental every average HRR come calculate fire produce gas temperature and speed
Degree, can so calculate shower nozzle or heat detector here every temperature and speed；
Step 5：Forecast model completes the prediction to automatic sprinkler or heat detector response time in case of fire.
2. it is according to claim 1 prediction sealed sprinkler head or heat detector response time forecast model, its
It is characterised by：In the step 3 (1), the time constant that different combustible fire increases is different, increases by HRR
Speed time square fire is divided into four classes, i.e., ultrafast, quick, middling speed and at a slow speed fire.
3. it is according to claim 2 prediction sealed sprinkler head or heat detector response time forecast model, its
It is characterised by：The typical time constant of the four classes time square fire is as follows：
The typical time constant of 1 time square of table fire
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| CN110516331A (en) * | 2019-08-15 | 2019-11-29 | 哈尔滨工程大学 | Marine personnel's emergency escape departure time calculation method under a kind of fire condition |
| CN110516331B (en) * | 2019-08-15 | 2021-06-08 | 哈尔滨工程大学 | Method for calculating emergency escape and evacuation time of marine personnel under fire condition |
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