HK1224359B - Exhaust ventilation system - Google Patents

Description

Exhaust ventilation system

This application claims to be a divisional application of the invention patent application with application number 200980156063.3. The application date of the original application is December 3, 2009, and the name of the invention is "Exhaust flow control system and method".

field

Embodiments of the present invention generally relate to controlling exhaust air flow in ventilation systems. More specifically, embodiments relate to controlling the exhaust air flow rate in exhaust ventilation systems based on the status of cooking appliances.

background

Exhaust ventilation systems can be used to remove fumes and air pollutants generated by cooking appliances. These systems are typically equipped with an exhaust hood positioned above the cooking appliance, which includes an exhaust fan that removes fumes from the area where the cooking appliance is in use. Some systems also include manual or automatic dampers that can be opened or closed to vary the exhaust flow in the system.

To reduce or eliminate smoke and other air pollutants produced during cooking, it may be helpful to extract some of the air from the ventilated space. This can increase the energy consumption of the cooking appliance or stove. Therefore, it is important to control the exhaust flow rate to maintain an airflow sufficient to eliminate smoke and other air pollutants while reducing or minimizing energy losses.

Overview

One or more embodiments include a method for controlling an exhaust flow rate in an exhaust ventilation system including an exhaust hood positioned above a cooking appliance. The method may include measuring an exhaust temperature in the vicinity of the exhaust hood, measuring a radiant temperature of the exhaust in the vicinity of the cooking appliance, determining an appliance status based on the measured exhaust temperature and the radiant temperature, and controlling the exhaust flow rate in response to the determined appliance status.

One or more embodiments may include controlling the exhaust flow rate in the exhaust ventilation system, wherein the exhaust temperature in the vicinity of the exhaust hood is measured using a temperature sensor. Embodiments may also include controlling the exhaust flow rate in the exhaust ventilation system, wherein the radiant temperature in the vicinity of the cooking appliance is measured using an infrared (IR) sensor. Embodiments may also include controlling the exhaust flow rate in the exhaust ventilation system, wherein the appliance state includes a cooking state, an idle state, and an off state. In the cooking state, it may be determined that the radiant temperature and the average radiant temperature of the cooking appliance fluctuate, or that the exhaust temperature is above a minimum exhaust temperature. In the idle state, it may be determined that there are no radiant temperature fluctuations for the duration of the cooking time and that the exhaust temperature is less than a predetermined minimum exhaust temperature. In the off state, it may be determined that the average radiant temperature is less than a predetermined minimum radiant temperature and that the exhaust temperature is less than a predetermined ambient air temperature plus the average ambient air temperature of the space in the vicinity of the cooking appliance.

Embodiments may further include controlling an exhaust flow rate in an exhaust ventilation system positioned above the cooking appliance, wherein the exhaust flow is controlled by turning a fan on or off or by varying fan speed and damper position based on the determined appliance status.

Embodiments may further include controlling an exhaust flow rate in an exhaust ventilation system positioned above the cooking appliance, wherein the exhaust flow rate is varied based on a change in the state of the appliance.

Embodiments may further include controlling an exhaust flow rate in an exhaust ventilation system positioned above a cooking appliance, wherein the exhaust flow rate is varied between a predetermined design exhaust flow rate, a predetermined idle exhaust flow rate, and an off exhaust flow rate in response to a detected change in the appliance status.

Embodiments may further include controlling an exhaust flow rate in an exhaust ventilation system positioned above the cooking appliance, wherein the system is calibrated prior to controlling the exhaust flow rate. Embodiments may further include controlling an exhaust flow rate in an exhaust ventilation system positioned above the cooking appliance, wherein a difference between an exhaust temperature and a temperature of an ambient space proximate the ventilation system is measured to determine an appliance status.

Embodiments may further include controlling an exhaust flow rate in an exhaust ventilation system positioned above a cooking appliance, wherein the cooking appliance is in a cooking state when the radiant temperature fluctuates and the radiant temperature is greater than a predetermined minimum radiant temperature, the cooking appliance is in an idle state when the radiant temperature does not fluctuate, and the cooking appliance is in an off state when the radiant temperature does not fluctuate and the radiant temperature is less than a minimum predetermined radiant temperature.

Embodiments may further include controlling an exhaust flow rate in an exhaust ventilation system positioned above a cooking appliance, wherein the cooking appliance is in a cooking state when the exhaust temperature is greater than or equal to a maximum predetermined ambient temperature, the cooking appliance is in an idle state when the exhaust temperature is less than the predetermined maximum ambient temperature, and the cooking appliance is in an off state when the exhaust temperature is less than the predetermined ambient temperature. Embodiments may further include measuring the radiant temperature using an infrared sensor.

Embodiments may further include an exhaust ventilation system including an exhaust hood mounted above the cooking appliance, the exhaust ventilation system having an exhaust fan for removing exhaust gas generated by the cooking appliance, at least one sensor for measuring a radiant temperature of the cooking appliance, at least one temperature sensor attached to the exhaust hood for measuring a temperature of the exhaust gas, and a control module that determines a status of the cooking appliance based on the measured radiant temperature and the exhaust gas temperature and controls an exhaust gas flow rate based on the appliance status.

Embodiments may also include an infrared sensor for measuring radiant temperature, a temperature sensor for measuring exhaust temperature in the vicinity of the exhaust hood, and a control module that may include a processor to determine the status of the cooking appliance and control the exhaust flow rate based on the appliance status.

Embodiments may further include a control module that controls the exhaust flow rate by controlling the speed of the exhaust fan, at least one motorized balancing damper attached to the exhaust hood to control the amount of exhaust entering the hood duct.

In various embodiments, the control module may also control the exhaust flow rate by controlling a position of at least one motorized balancing damper.

In addition, the control module can determine the appliance state, wherein the appliance state includes a cooking state, an idle state, and an off state. The embodiment can also include a control module for controlling the exhaust flow rate by changing the exhaust flow rate between a design exhaust flow rate (Qdesign), an idle exhaust flow rate (Qidle), and an off exhaust flow rate (0) based on the change in the appliance state.

The embodiment may further include a control module that changes the exhaust flow rate to a design exhaust flow rate (Qdesign) when the appliance is determined to be in a cooking state, changes the exhaust flow rate to an idle exhaust flow rate (Qidle) when the appliance state is determined to be in an idle state, and changes the exhaust flow rate to an off exhaust flow rate when the appliance is determined to be in an off state.

Embodiments may further include a control module that may further determine fluctuations in the radiant temperature.

Embodiments may further include a control module that may determine that the cooking appliance is in a cooking state when the radiant temperature fluctuates and the radiant temperature is greater than a predetermined minimum radiant temperature, determine that the cooking appliance is in an idle state when the radiant temperature does not fluctuate, and determine that the cooking appliance is in an off state when the radiant temperature does not fluctuate and the radiant temperature is less than a minimum predetermined radiant temperature.

Embodiments may further include a temperature sensor for measuring the ambient temperature of the air in the vicinity of the ventilation system, and the control module may further determine a difference between the exhaust temperature in the vicinity of the exhaust hood and the ambient temperature in the vicinity of the ventilation system.

Embodiments may further include a control module that determines that the cooking appliance is in a cooking state when the exhaust temperature is greater than or equal to a maximum predetermined ambient temperature, that the cooking appliance is in an idle state when the exhaust temperature is less than a predetermined maximum ambient temperature, and that the cooking appliance is in an off state when the exhaust temperature is less than a predetermined ambient temperature. Embodiments may further include a control module that controls the exhaust flow rate after the system is calibrated.

Embodiments may include a control module for controlling an exhaust flow rate in an exhaust ventilation system including an exhaust hood positioned above a cooking appliance, the control module including a processor for determining a status of the cooking appliance and controlling the exhaust flow rate based on the appliance status.

In various embodiments, the control module may further include controlling the exhaust flow rate, wherein the appliance state comprises one of a cooking state, an idle state, and an off state. The control module may further include controlling the exhaust flow rate, wherein the exhaust flow rate comprises one of a design exhaust flow rate (Qdesign), an idle exhaust flow rate (Qidle), and an off exhaust flow rate. The control module may further include functionality for changing the exhaust flow rate from the design exhaust flow rate to the idle exhaust flow rate and to the off exhaust flow rate. The control module may further include controlling the exhaust flow rate, wherein in the cooking state, the control module changes the exhaust flow rate to the design air flow rate, in the idle cooking state, the control module changes the exhaust flow rate to the idle exhaust flow rate, and in the off state, the control module changes the exhaust flow rate to the off exhaust flow rate.

In various embodiments, the control module may further include controlling the exhaust flow rate, wherein the processor determines the appliance status by measuring an ambient temperature of the exhaust gas generated by the cooking appliance and by measuring a radiant temperature of the cooking appliance.

The control module may further include controlling the exhaust flow rate, wherein the processor determines a cooking state when the exhaust temperature is greater than or equal to a predetermined maximum ambient temperature, determines an idle state when the exhaust temperature is less than the predetermined maximum ambient temperature, and determines an off state when the exhaust temperature is less than the predetermined ambient temperature.

The control module may further include controlling the exhaust flow rate, wherein the processor determines a cooking state when the radiant temperature fluctuates and the radiant temperature is greater than a predetermined minimum radiant temperature, determines an idle state when the radiant temperature does not fluctuate, and determines an off state when the radiant temperature does not fluctuate and the radiant temperature is less than a predetermined minimum radiant temperature.

The control module may also include controlling the exhaust flow rate by controlling the speed of an exhaust fan attached to the exhaust hood for removing exhaust gas generated by cooking appliances, controlling the exhaust flow rate by controlling the position of at least one balancing damper attached to the exhaust hood, and controlling the exhaust flow rate where the control module also calibrates the system before the controller controls the exhaust flow rate.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a perspective view diagrammatically illustrating an exhaust ventilation system positioned above a cooking appliance and having an exhaust flow control system according to various embodiments;

FIG2 is a perspective view diagrammatically illustrating an exhaust ventilation system having a motorized damper;

FIG3 is a block diagram of an exemplary exhaust flow rate control system according to the present disclosure;

4 is a flow chart illustrating an exemplary exhaust flow rate control method according to various embodiments;

5 is a flow chart of an exemplary startup routine for at least one embodiment with or without automatic dampers;

6 is a flow chart of an inspection procedure for at least one embodiment having a single hood and no dampers;

7 is a flow chart of an inspection procedure for at least one embodiment having multiple hoods, a fan, and motorized dampers;

8 is a flow chart of a calibration procedure for at least one embodiment having a single shroud, a single fan, and no motorized dampers;

9 is a flow chart of a calibration procedure for at least one embodiment having multiple hoods, a fan, and no motorized dampers;

10 is a flow chart of a calibration procedure for at least one embodiment having one or more hoods, a fan, and a motorized damper;

FIG11 is a flow chart of the operating procedure of at least one embodiment without a motorized balancing damper;

FIG12 is a flow chart of an operating procedure for at least one embodiment having a motorized balancing damper;

FIG13 is a block diagram of an exemplary exhaust flow control system according to the present disclosure;

FIG. 14 is a block diagram of an exemplary exhaust flow control system according to the present disclosure; and

FIG. 15 is a block diagram of an exemplary exhaust flow control system according to the present disclosure.

Detailed description

1 , an exemplary exhaust ventilation system 100 is shown that includes an exhaust hood 105 positioned above a plurality of cooking appliances 115 and arranged to communicate with an exhaust assembly 145 via an exhaust duct 110. The bottom opening of the exhaust hood 105 can be generally rectangular, but can have any other desired shape. The walls of the hood 105 define an interior volume 185 that communicates with a downwardly facing bottom opening 190 at the end of the hood 105 positioned above the cooking appliances 115. The interior volume 185 can also communicate with the exhaust assembly 145 via the exhaust duct 110. The exhaust duct 110 can extend upward through the exhaust assembly 145 toward the external ventilation environment.

Exhaust assembly 145 may include a motorized exhaust fan 130, which draws exhaust air generated by cooking appliances 115 into exhaust duct 110 and expel it into the external ventilation environment. When the motor of exhaust fan 130 is running, an exhaust flow path 165 is established between cooking appliances 115 and the external ventilation environment. As air is drawn away from the cooktop area, smoke, air pollutants, and other airborne particles are expelled through exhaust duct 110 and exhaust assembly 145 into the external ventilation environment.

The exhaust ventilation system 100 may also include a control module 302, which preferably includes a programmable processor 304 operatively coupled to and receiving data from a plurality of sensors and configured to control the speed of the motorized exhaust fan 130, which in turn regulates the exhaust flow rate within the system 100. The control module 302 controls the speed of the exhaust fan 130 based on the output of a temperature sensor 125 positioned on or within the exhaust duct 110 and the output of an infrared (IR) radiant temperature sensor 120 positioned facing each surface of the cooking appliance 115. In at least one embodiment, three IR sensors 120 may be provided, each positioned above a respective cooking appliance 115, such that each IR sensor 312 faces a respective cooking surface 115. However, any number and type of IR sensors 120 and any number of cooking appliances 115 may be used, as long as the radiant temperature of each cooking surface is detected. The control module 302 communicates with the sensors 125 and 120 and identifies the status of the cooking appliance based on the sensor readings. The status of the cooking appliance 115 is determined based on the exhaust temperature and the radiant temperature sensed using these multiple detectors.

The control module 302 communicates with the motorized exhaust fan 130 and includes a speed control module, such as a variable frequency drive (VFD), that controls the speed of the motor, as well as one or more motorized balancing dampers (BDs) 150 positioned proximate to the exhaust duct 110. The control module 302 can determine the state (AS) of the cooking appliance based on the outputs of the exhaust temperature sensor 125 and the IR radiation temperature sensor 120, and vary the speed of the exhaust fan 130 and the position of the motorized balancing dampers 150 in response to the determined state (AS) of the cooking appliance. For example, the cooking appliance 115 can have a cooking state (AS=1), an idle state (AS=2), or an off state (AS=0). The state of the cooking appliance 115 can be determined based on the temperature detected by the exhaust temperature sensor 125 and the IR sensor 120. According to various embodiments, methods for determining the appliance state (AS) are illustrated in FIGS. 4-12 and discussed in detail below. Based on the determined appliance state (AS), the control module 302 selects a fan speed and/or a position of a balancing damper in the system such that the exhaust flow rate corresponds to a predetermined exhaust flow rate associated with the specific appliance state (AS).

Referring to FIG2 , a second embodiment of an exhaust ventilation system 200 is shown, having multiple exhaust hoods 105′ that can be positioned above one or more cooking appliances 115 (depending on the size of the cooking equipment). System 200 can include at least one exhaust temperature sensor 125 for each corresponding hood 105′ and at least one pressure sensor 155 connected to each corresponding hood boss opening (TAB). Each exhaust hood duct 110 can include a motorized balancing damper 150. Balancing damper 150 can be positioned at the corresponding hood duct 110 and can include an actuator that provides damper position feedback. System 200 can also include at least one IR sensor 312 positioned so that it detects the radiant temperature of the corresponding cooking surface. An exhaust fan 130 can be connected to exhaust assembly 145 to allow exhaust air to move from the cook-top into the surrounding external ventilation environment. Additional pressure sensors 140 may be included to measure static pressure in the main exhaust duct as part of the exhaust assembly 145 , and a plurality of grease removal filters 170 may be included at the bottom opening 190 of the exhaust hood 105 to remove grease and soot particles from entering the hood duct 110 .

FIG3 shows a schematic block diagram of an exhaust flow control system 300 that can be used with any of the systems shown above (e.g., 100 and 200). As shown in FIG3, the exhaust flow control system 300 includes a control module 302. The control module 302 includes a processor 304 and a memory 306. The control module 302 is coupled to and receives input from a plurality of sensors and devices, including an IR sensor 312, which may be positioned on the exhaust hood canopy 105 so that the IR sensor 312 faces the surface of the cooking appliance 115 and detects the radiant temperature emanating from the cooking surface; an exhaust temperature sensor 125, which is mounted adjacent to the hood duct 110 to detect the temperature of the exhaust gas drawn into the hood duct 110; an ambient air temperature sensor 160, which is positioned proximate to the ventilation system (100, 200) to detect the temperature of the air surrounding the cooking appliance 115; and a pressure sensor 155, which may be positioned proximate to the hood boss opening (TAB) to detect the pressure developed in the hood duct 110. Inputs from the sensors 308-314 and the operator console 311 are communicated to the control module 302, which then processes the input signals and determines the appliance status (AS) or condition. The control module processor 304 can control the speed of the exhaust fan motor 316 and/or the position of the motorized balancing damper 318 (BD) based on the appliance state. Each cooking state is associated with a specific exhaust flow rate (Q), as discussed below. Once the control module 302 determines that it is in a certain state, it can adjust the speed of the exhaust fan 316 and the position of the balancing damper 318 to achieve the predetermined air flow rate associated with each appliance state.

In various embodiments, sensors 308-314 can be operably coupled to processor 304 using conductive wires. The sensor output can be provided in the form of an analog signal (e.g., a voltage, current, or the like). Alternatively, the sensors can be coupled to processor 304 via a digital bus, in which case the sensor output can include one or more words of digital information. The number and location of exhaust temperature sensors 314 and radiant temperature sensors (IR sensors) 312 can be varied depending on the number of cooking appliances and associated hoods, hood rings, and hood ducts present in the system, as well as other variables such as hood length. The number and location of ambient air temperature sensors 310 can also be varied, as long as the temperature of the ambient air surrounding the ventilation system is detected. The number and location of pressure sensors 308 can also be varied, as long as they are installed in the hood duct adjacent to the exhaust fan 130 to measure the static pressure (Pst) in the main exhaust duct. All sensors are exemplary, and thus any known type of sensor can be used to achieve the desired functionality. Generally, the control module 302 may be coupled to the sensors 308 - 314 and the motor 316 and damper 318 via any suitable wired or wireless links.

In various embodiments, there may be multiple control modules 302. The type and number of control modules 302 and their location in the system may also vary depending on the complexity and size of the system, which may involve the number of sensors listed above and their location within the system.

As mentioned above, the control module 302 preferably includes a processor 304 and a memory 306, which can be configured to perform the control functions described herein. In various embodiments, the memory 306 can store a list of appropriate input variables, process variables, process control set points, and calibration set points for each hood. These stored variables can be used by the processor 304 during various stages of the check, calibration, and startup functions, as well as during operation of the system.

In various embodiments, the processor 304 can execute a sequence of program instructions stored on a computer-readable medium (e.g., electronic memory, optical or magnetic storage, or the like). The instructions, when executed by the processor 304, cause the processor 304 to perform the functions described herein. The instructions can be stored in the memory 306, or they can be embedded in another processor-readable medium, or a combination thereof. The processor 304 can be implemented using a microcontroller, a computer, an application-specific integrated circuit (ASIC), or discrete logic components, or a combination thereof.

In various embodiments, the processor 304 may also be coupled to a status indicator or display device 317, such as a liquid crystal display (LCD), for outputting alarm and error codes and other information to a user. The indicator 317 may also include an audible indicator, such as a buzzer, bell, alarm, or the like.

4 , an exemplary method 400 according to various embodiments is shown. Method 400 begins at S405 and proceeds to S410 or S425 to receive exhaust temperature input or pressure sensor input, and proceeds to S415 and S420 to receive ambient air temperature input and infrared sensor input. Control proceeds to S430.

At S430 , the current exhaust flow rate (Q) is determined. Control proceeds to S435 .

At S435, the current exhaust flow rate is compared with the desired exhaust flow rate. If the exhaust flow rate determined at S430 is the desired exhaust flow rate, the control process restarts. If the exhaust flow rate determined at S430 is not the desired exhaust flow rate, the control process proceeds to S440 or S450 based on the system configuration (e.g., if a motorized damper is present, the control process proceeds to S450, but if a motorized damper is not present, the control process proceeds to S440).

Based on the configuration, the damper position is determined at S450 or the exhaust fan speed is determined at S440. Based on the different options at S440 and S450, the control process proceeds to output a damper position command to the damper at S455 or output a speed command to the exhaust fan at S445. The control process can then proceed to determine whether the power to the cooking appliance is turned off at S460, in which case the method 400 ends at S465, or if the power is determined to be still on at S460, the method begins again.

Prior to operation, the system 100, 200 may be checked and calibrated by the control module 302 during startup to balance each hood to a preset design and idle exhaust flow rate, to purge and recalibrate sensors, if necessary, and to assess each component in the system for possible failure or damage. Appropriate alarm signals may be displayed on the LCD display in the event of a fault in the system to notify the operator of the fault and, optionally, how to recover from the fault.

For example, in an exemplary embodiment where the system 100 includes a single or multiple hoods connected to a single exhaust fan 130 and no motorized balancing damper (BD) 150, the control module 302 may include the following example listing of variables for each hood, as listed in Tables 1-4 below:

Table 1 List of hood setting points (can be pre-set)

Table 2 List of process control set points

Parameter Name & Unit default value Notes IRl_Derivative_Max_SP -1℃/second Derivative for flash set point 1R l_De rivative_Min_SP 300 seconds Derivative for IR exponential drop set point IRl_Drop_SPl 1℃ IR index drop set point IRl_Filter_Time 10 seconds IR signal filter time set point IRl_Jump_SP 1℃ IR signal jump set point (for flashing) IRl_Start_SP 30℃ IR signal activates cooking equipment set point IR2_Cooking_Timerl 420 seconds Cooking timer set points for IR1 field of view IR2_Derivative_Max_SP 1℃/second Derivative for flash set point 1R2_De rivative_Min_SP -1℃/second Derivative for IR exponential drop set point IR2_Drop_SPl 1℃ IR index drop set point IR2_Filter_Time 10 seconds IR signal filter time set point IR2Jump_SP 1℃ IR signal jump set point (for flashing) PID_Cal_K 0.5%/CFM PID scaling factor in calibration mode PID_Cal_T 100 seconds PID integral coefficient in calibration mode PIDJC 0.5%/CFM PID proportional coefficient in cooking mode PID_T 100 seconds PID integral coefficient in cooking mode

Table 3 List of set points obtained during calibration for each hood

Parameter Name & Unit Notes VFDdesign, 0 to 1 VFDidle, 0 to 1 dTIRcah, ℉ Recording for each IR sensor in the hood Qdesignl,cfm Only records are made for multiple shrouds connected to a single fan

Table 4 List of process variables

For example, in an exemplary embodiment where the system 100 includes multiple hoods connected to a single exhaust fan 130 and where the hoods are equipped with motorized balancing dampers (BDs) 150, the control module 302 may include the following example listing of variables for each hood, as listed in Tables 5-8 below:

List of input variables for each mask

Table 5: List of hood setting points (can be pre-set)

Table 6 List of process control set points

Table 7 List of set points obtained during calibration

Table 8 List of process variables

Parameter Name & Unit Notes Qj，cfm For each hood Qtot, cfm See Equation A1.1 for calculating airflow For each hood (one balancing damper per hood) kAirflowDesign One for the system. See Error! Reference source not found. For each IR sensor in the hood Tex,℉ For each hood Tspace，℉ One for the entire space VFD, 0 to 1 One for the system

In various implementations, the control module processor 304 may be configured to calculate the exhaust flow (Q) at the exhaust temperature Tex using the following equation:

in:

_Kf is the hood coefficient.

dp is the static pressure measured at the hood boss port in inches WC.

Dens _exh is the density of the exhaust gas in lb. mass per cubic foot.

Dens _std is the standard density of air (at 70°F and 29.921 inches of mercury at atmospheric pressure = 0.07487 lb/ft ³ ).

in:

Tex - Exhaust gas temperature in °F.

Patm - atmospheric pressure in inches of mercury.

Patm = 29.92 (1 - 0.0000068753 h) ^5.2559 Equation 3

in:

h - height above mean sea level, ft

When reporting kAirflowDesign, the mass flow rate of exhaust air Mtot [lb/ft ³ ] through all hoods in a kitchen equipped with a DCV system needs to be calculated and divided by the total design mass airflow for those hoods Mtot_design [lb/ft ³ ].

Where Mtot and Mtot_design are calculated according to Equation 4, and Dens _exh is calculated according to Equation 2 using the actual temperature and design temperature of the exhaust gas.

FIG5 illustrates a flow chart of a startup procedure 500 that can be executed by the control module 302 of an embodiment having a single or multiple hoods connected to a single exhaust fan and no motorized balancing dampers at the hood level. The startup procedure 500 begins at S502 and can include one of the following three options for starting the exhaust fan 316:

1) Automatically, when any appliance under the hood is opened (500):

In block S505, the infrared sensor 120 may measure the radiant temperature (IRT) of the cooking surface of any one of the at least one cooking appliance 115, the ambient air temperature sensor 160 may measure the temperature of the space surrounding the cooking appliance (Tspace), and another temperature sensor may measure the cooking temperature (Tcook). If the processor 304 in the control module 302 determines that the radiant temperature (IRT) exceeds the minimum temperature reading (IRTmin) (IRTmin=Tspace+dTcook) (block S510), the control module 302 may start the fan (block S515) and set the exhaust air flow (Q) to (Qidle) (block S520). If the processor 304 determines that the radiant temperature (IRT) does not exceed the minimum temperature (IRTmin) (block S510), the control module keeps the fan off (block S525).

The control module 302 may also analyze a second reading before system operation begins: at block S530, the exhaust temperature (Tex) may be measured by the exhaust temperature sensor 125. If the exhaust temperature exceeds a minimum preset exhaust temperature (Texmin) (block S535), the control module 302 may start the fan and set the exhaust flow (Q) to (Qidle) (block S545). If the exhaust temperature (Tex) does not exceed the minimum exhaust temperature (Texmin), the control module 302 may turn the fan off (block S550). The startup procedure may be terminated after these steps are performed (block S550).

2) According to the schedule:

The exhaust hood is turned on and off according to a pre-programmable (e.g., 1 week) schedule. When the schedule is followed, the hood exhaust flow (Q) is set to (Qidle).

3) Manually, using the override button on the hood:

In various embodiments, activating an override button on the hood may set the hood exhaust airflow (Q) to (Qdesign) for a preset period of time (TimeOR).

The flowchart for the startup procedure implemented by the control module 302 of the second embodiment of the system 200 having multiple hoods connected to a single exhaust fan and having motorized balancing dampers at the hood level follows substantially the same steps as those illustrated in Figure 5, except that at each step the balancing damper BD can be kept open so that a suitable exhaust flow (Q) can be maintained in conjunction with the exhaust fan.

6 , a flow chart illustrating a process 600 that can be executed by the control module 302 to check the system 100 before the flow rate control operation begins is provided. The process 600 can begin at S602 and continue to the control module self-diagnostic process (block S605). If the self-diagnostic process is OK (block S610), the control module 302 can set the variable frequency drive (VFD) that controls the exhaust fan speed to a preset frequency (VFDidle) (block S615). The static pressure can then be measured by a pressure sensor positioned at the hood boss port (block S620) and the exhaust flow can be set to (Q) calculated using the formula of Equation 1 (block S625). If the self-diagnostic process fails, the control module 302 can verify whether (VFD) is the preset frequency (VFDidle) and whether the exhaust flow (Q) is less than or exceeds (Qidle) a threshold airflow coefficient (blocks S630, S645). Based on the exhaust flow readings, the control module 302 generates and outputs an appropriate error code, which may be shown or displayed on an LCD display or other suitable indicator 317 attached to the exhaust hood or coupled to the control module 302 .

If the exhaust flow (Q) is less than (Qidle) by a filter missing coefficient (Kfilter missing) (block S630), then an error code "check filters and fans" can be generated (block S635). On the other hand, if the exhaust flow (Q) exceeds (Qidle) by a blocked filter coefficient (Kfilter clogged) (block S645), then a "clean filter" alarm can be generated (block S650). If the exhaust flow (Q) is actually the same as (Qidle), then no alarm is generated (blocks S650, S655), and the program ends (S660).

7 , a flow chart illustrating another routine 700 that can be executed by the control module 302 to check the system 200 is provided. The routine 700 can begin at S702 and continue to the control module 302 self-diagnostic process (block S705). If the result of the self-diagnostic process is OK (block S710), the control module 302 can maintain the exhaust flow (Q) at (Qidle) by maintaining the balancing dampers in their initial or current positions (block S715). The static pressure (dp) is then measured by the pressure sensor positioned at the hood boss port (block S720), and the exhaust flow is set to (Q) calculated using Equation 1 (block S725). If the self-diagnostic process fails, the control module can set the balancing dampers (BD) to the open position and set (VFD) to (VFDdesign) (block S730).

The control module 302 may then check whether the balancing damper is faulty (block S735). If there is a faulty balancing damper, the control module 302 may open the balancing damper (block S740). If there is no faulty balancing damper, the control module 302 may check whether there is a faulty sensor in the system (block S745). If there is a faulty sensor, the control module 302 may set the balancing damper to (BDPdesign), the (VFD) to (VFDdesign), and the exhaust flow to (Qdesign) (block S750). Otherwise, the control module 302 may set the (VFD) to (VFDidle) until the cooking appliance is turned off (block S755). This step terminates the program (block S760).

In various embodiments, the hood 105 is automatically calibrated to the design airflow (Qdesign). The calibration step procedure 800 is illustrated in Figure 8. The procedure begins at S802 and can be activated so that all ventilation systems are running and cooking appliances are in the off state (blocks S805, S810). The calibration procedure 800 can begin with the fan off (blocks S810, S870). If the fan is off, the hood can be balanced to the design airflow (Qdesign) (block S830). If the hood is not balanced (block S825), the control module 302 can adjust the VFD (block S830) until the exhaust flow reaches (Qdesign) (block S835). The procedure 800 then waits until the system stabilizes. The hood 105 can then be balanced to (Qidle) by reducing the (VFD) speed (blocks S840, S845). The procedure 800 waits again until the system 100 stabilizes.

The next step is to calibrate the sensors (block S850). Calibration of the sensors can be performed during the first calibration mode and performed on cold cooking appliances and when no one is under the hood. The radiant temperature (IRT) can be measured and compared to the thermostat reading (Tspace), and the difference for each of the sensors can be stored in the memory 306 of the control module 302 (block S855). In subsequent calibration procedures or when the exhaust system is turned off, the change in radiant temperature is measured again and compared to the calibrated value stored in the memory 306 (block S855). If the reading is higher than the maximum allowable difference, a warning is generated in the control module 302 to purge the sensor (block S860). Otherwise, the sensor is considered calibrated (block S865) and the process 800 terminates (block S875).

9 illustrates a calibration procedure 900 for a system having multiple hoods, one fan, and no motorized balancing dampers. Procedure 900 may follow substantially the same steps as those shown above for a system with a single hood, a single fan, and no motorized dampers, except that each hood is calibrated for procedure 900. Procedure 900 begins with hood 1 and follows the hood balancing steps (blocks S905-S930 and S985) as shown above, and the sensor calibration steps (blocks S935-S950) as shown above.

Once the first hood is calibrated, the airflow for the next hood is verified (block S955). If the airflow is at the set point (Qdesign), the sensor calibration is repeated for the second (and any subsequent) hoods (blocks S960, S965). If the airflow is not at the set point (Qdesign), the airflow and sensor calibration can be repeated for the current hood (block S970). Procedure 900 can be followed until all hoods in the system are calibrated (block S965). The new design airflow for all hoods can be stored in memory 306 (block S975), and the control process ends at S980.

FIG10 illustrates an automated calibration procedure 1000 that may be performed by the second embodiment 200. During the calibration procedure 1000, all hoods are calibrated to a design airflow (Qdesign) at a minimum static pressure. The calibration procedure 1000 may be activated at a time when the cooking equipment is not scheduled to be used with all hood filters in place, and repeated regularly (e.g., once a week). The procedure 1000 may be activated at block S1005. The exhaust fan may be set to a maximum speed VFD=1 (VFD=1 - full speed; VFD=0 - fans off), and all balancing dampers may be fully opened (BDP=1 - fully open; BDP=0 - fully closed) (block S1010). The exhaust flow of each hood may be measured using a hood boss port pressure sensor (PT) (block S1015). In various embodiments, each hood may be balanced using a balancing damper to achieve the design airflow (Qdesign). At this point, each BDP may be less than 1 (less than fully open). There may also be a waiting period for the system to stabilize.

If the exhaust flow is not at (Qdesign), then the VFD setting is reduced until one of the balancing dampers is fully opened (block S1030). In at least one embodiment, this procedure can be performed step-by-step by gradually reducing the VFD setting by 10% at each repetition until one of the dampers is fully opened and the airflow is (Q) = (Qdesign) (blocks S1020, S1030). On the other hand, if the airflow is Q = (Qdesign) at block S1020, then the pressure sensor setting (Pstdesign), fan speed VFDdesign, and balancing damper position BDPdesign in the main exhaust duct can be stored (block S1025). At this point, calibration is complete (block S1035).

FIG11 is a flow chart of a method 1100 for controlling exhaust airflow, implemented in various embodiments according to system 100. As shown in FIG11 , individual hood exhaust airflow (Q) can be controlled based on appliance status (AS) or conditions, such as AS=1, indicating that the corresponding appliance is in a cooking state, AS=2, indicating that the corresponding appliance is in an idle state, and AS=0, indicating that the corresponding cooking appliance is off. Exhaust temperature sensor 125 and radiant IR sensor 120 can detect the appliance status and provide the detected status to processor 175. Based on the readings provided by the sensors, control module 302 can vary the exhaust airflow (Q) in system 100 to correspond to a predetermined airflow (Qdesign), a measured airflow (Q) (see below), and a predetermined airflow (Qidle). When the detected cooking state is AS=1, control module 302 can adjust the airflow (Q) to correspond to the predetermined airflow (Qdesign). When the cooking state is AS=2, control module 302 can adjust the airflow (Q) to a value calculated according to the following equation:

In addition, when the detected cooking state is AS=0, the control module 302 may adjust the air flow (Q) to Q=0.

11 , the control process begins at S1102 and continues to block S1104, where the appliance state can be determined based on inputs received from the exhaust temperature sensor 125 and the IR temperature sensor 120. The exhaust temperature (Tex) value and the ambient space temperature (Tspace) value can be read and stored in the memory 306 (block S1106) to calculate the exhaust flow (Q) in the system (block S1108). The exhaust flow (Q) can be calculated, for example, using Equation 6. If the calculated exhaust flow (Q) is less than a predetermined value (Qidle) (block S1110), the cooking state can be determined to be AS=2 (block S1112) and the exhaust flow (Q) can be set to correspond to (Qidle) (block S1114). In this case, the fan 130 can be maintained at a speed (VFD) that maintains (Q)=(Qidle) (block S1116). If it is determined in block S1110 that the airflow (Q) exceeds the preset (Qidle) value, the appliance state can be determined to be AS=1 (cooking state) (block S1118) and the control module 302 can set the fan speed (VFD) at (VFD)=(VFDdesign) (block S1120) to maintain the airflow (Q) at (Q)=(Qdesign) (block S1122).

At block S1124, the average radiant temperature (IRT) and the fluctuation in radiant temperature (FRT) emanating from the appliance cooking surface can be measured using the IR detector 120. If the processor 304 determines that the radiant temperature is increasing or decreasing more rapidly than a predetermined threshold (block 1128) and the cooking surface is hot (IRT > IRTmin) (block S1126), then the appliance status is reported as AS = 1 (S1132) and the fan 130 speed (VFD) can be set to (VFDdesign) (block S1134). When the exhaust hood 105 is equipped with multiple IR sensors 120, by default, if any of the sensors detects fluctuations in radiant temperature (block S1128), then a cooking status (AS = 1) is reported. When a cooking status is detected, the hood exhaust airflow (Q) can be set to the design airflow (Q = Qdesign) (S1136) for a preset cooking time (TimeCook) (e.g., 7 minutes). In at least one embodiment, this is overridden by the exhaust temperature signal (Tex) (block S1130). Additionally, if the IR sensor 120 detects another temperature fluctuation within the cooking time (TimeCook), the cooking timer is reset.

On the other hand, if the IR sensor 120 detects no temperature fluctuation within the preset cooking time (TimeCook), the appliance state is reported as idle AS=2 (S1138) and the fan 130 speed can be modulated (block S1140) to maintain the exhaust flow at (Q)=(Q) calculated according to Equation 6 (block S1142). When all IR sensors 120 detect (IRT<IRTmin) (block S1126) and (Tex<Tspace+dTspace) (block S1144), the appliance state is determined to be off (AS=0) (block S1146) and the exhaust fan 130 is turned off (block S1150) by setting VFD=0 (block S1148). Otherwise, the appliance state is determined to be cooking (AS=2) (block S1152) and the fan 130 speed (VFD) is modulated (block S1154) to maintain the exhaust airflow (Q) at the level calculated according to Equation 6 (described above) (block S1156). Operation 1100 may end at block S1158, where the control module 302 sets the airflow (Q) at the airflow level based on the determined appliance state (AS).

12A-12C illustrate an exemplary method 1200 for controlling exhaust flow in a system 200 having a motorized balancing damper at each exhaust hood 105. Method 1200 may follow substantially similar steps to those of method 1100 described above, except that when a fluctuation in radiant temperature (FRT) is detected by the IR sensor 120 (block S1228) or when the exhaust temperature (Tex) exceeds a minimum value (Tmin) (block S1230), the appliance state is determined to be AS=1 (block 1232), and the control module 302 also checks whether the balancing damper is in a fully open position (BDP)=1 and whether the fan 130 speed (VFD) is below a predetermined design fan speed (block S1380). If the above conditions are true, the fan 130 speed (VFD) is increased (block 1236) until the exhaust flow Q reaches the design airflow (Qdesign) (block S1240). If the above condition is not true, then the fan 130 speed (VFD) is maintained at (VFDdesign) (block 1238), and the airflow (Q) is maintained at (Q) = (Qdesign) (block S1240).

On the other hand, if there is no radiant temperature fluctuation (block S1228) or the exhaust temperature (Tex) does not exceed the maximum temperature (Tmax) (block S1230), then the appliance state is determined to be the idle state AS=2 (block S1242). In addition, the control module 302 can check whether the balancing damper is in the fully open position (BDP)=1 and whether the fan 130 speed (VFD) is lower than the design fan speed (block S1244). If the answer is yes, the fan 130 speed (VFD) is increased (block S1246) and the balancing damper is modulated (block S1250) to maintain the airflow (Q) at (Q)=(Q) (calculated according to Equation 6) (block S1252).

If no radiant temperature is detected (block S1226) and the exhaust temperature is (Tex<Tspace+dTspace) (block S1254), the appliance state is determined to be AS=0 (off) (block S1256), the balancing damper is fully closed (BDP=0) (block S1258), and the fan 130 is turned off (S1260). The appliance state can be stored. On the other hand, if the exhaust temperature exceeds the ambient temperature, the appliance state is determined to be AS=2 (block S1262) and the balancing damper is modulated (block S1264) to keep the fan 130 on to maintain the airflow (Q)=(Q) calculated based on Equation 6 (block S1266). The operation can then end and the exhaust flow is set according to the determined appliance state (block S1268).

FIG13 is a block diagram of an exemplary exhaust flow control system according to the present disclosure. Specifically, system 1300 includes multiple control modules (1302, 1308, and 1314) and outputs (1306, 1312, and 1318, respectively), as described above (e.g., motor control and damper control signals). Each of the multiple control modules (1302, 1308, and 1314) is coupled to a corresponding one of the sensors (1304, 1310, and 1316, respectively), as described above (e.g., temperature, pressure, etc.). The control modules can control their respective exhaust flow systems independently or in conjunction with one another. Furthermore, the control modules can communicate with one another.

Figure 14 is a block diagram of an exemplary exhaust flow control system according to the present disclosure. In particular, system 1400 includes a single control module 1402 coupled to multiple interfaces 1404-1408, each of which is then coupled to corresponding sensors (1410-1414) and control outputs (1416-1420). Control module 1402 can monitor and control the exhaust flow rate of multiple hoods adjacent to multiple appliances. Each appliance can be monitored individually and a suitable exhaust flow rate can be set as described above. In the configuration shown in Figure 14, it may be feasible to upgrade the software in control module 1402 once to effectively upgrade the exhaust flow control system in each hood. In addition, single control module 1402 can reduce costs and simplify the maintenance of the exhaust flow control system and allow existing systems to be upgraded or modified to include the exhaust flow control method described above.

FIG15 is a block diagram of an exemplary exhaust flow control system according to the present disclosure. Specifically, system 1500 includes a control module 1502 coupled to a sensor 1504 and a control output 1506. Control module 1502 is also coupled to an alarm interface 1508, a fire suppression interface 1512, and an appliance communication interface 1516. Alarm interface 1508 is coupled to an alarm system 1510. Fire suppression interface 1512 is coupled to a fire suppression system 1514. Appliance communication interface 1516 is coupled to one or more appliances 1518-1520.

In operation, the control module 1502 can communicate and exchange messages with the alarm system 1510, the fire suppression system 1514, and the appliances 1518-1520 to better determine appliance status and appropriate exhaust flow rates. Furthermore, the control module 1502 can provide messages to the various systems (1510-1520) so that their functions can be coordinated for a more efficient operating environment. For example, the exhaust flow control module 1502, through its sensors 1504, can detect a fire or other hazardous condition and send this message to the alarm system 1510, the fire suppression system 1514, and the appliances 1518-1520 so that each device or system can take appropriate action. Furthermore, messages from the appliances 1518-1520 can be used by the exhaust flow control system to more accurately determine appliance status and provide more precise exhaust flow control.

Embodiments of the method, system, and computer program product for controlling exhaust flow rate can be implemented on a general-purpose computer, a special-purpose computer, a programmable microprocessor or microcontroller and peripheral integrated circuit components, an ASIC or other integrated circuit, a digital signal processor, hard-wired electronic or logic circuits such as discrete component circuits, a programmable logic device such as a PLD, PLA, FPGA, PAL, or the like. Generally, any process capable of performing the functions or steps described herein can be used to implement embodiments of the method, system, or computer program product for controlling exhaust flow rate.

In addition, embodiments of the disclosed methods, systems, and computer program products for controlling exhaust flow rate can be readily implemented, in whole or in part, in software using, for example, an object or object-oriented software development environment that provides portable source code that can be used on a variety of computer platforms. Alternatively, embodiments of the disclosed methods, systems, and computer program products for controlling exhaust flow rate can be implemented, in part or in whole, in hardware using, for example, standard logic circuits or VLSI designs. Other hardware or software may be used to implement the embodiments, depending on the speed and/or efficiency requirements of the system, the specific functionality, and/or the specific software or hardware systems, microprocessors, or microcomputer systems utilized. Embodiments of the methods, systems, and computer program products for controlling exhaust flow rate can be implemented in hardware and/or software using any known or later developed system or structure, device, and/or software by one skilled in the art from the functional description provided herein and based on general basic knowledge in the fields of computers, exhaust flow, and/or cooking appliances.

Furthermore, embodiments of the disclosed methods, systems, and computer program products for controlling exhaust flow rate can be implemented in software that is executed on a program-controlled general-purpose computer, a dedicated computer, a microprocessor, or the like. Furthermore, the exhaust flow rate control methods of the present invention can be implemented as a program embedded on a personal computer, such as a CGI script, as a resource resident on a server or graphics workstation, as a program embedded in a dedicated processing system, or the like. The methods and systems can also be implemented by physically incorporating the methods for controlling exhaust flow rate into a software and/or hardware system, such as the hardware and software systems of an exhaust vent cover and/or appliance.

It is therefore apparent that methods, systems, and computer program products for controlling exhaust flow rate are provided according to the present invention. While the present invention has been described with reference to a number of embodiments, it is apparent that many alternatives, modifications, and variations are or will be apparent to those skilled in the art. Applicants therefore intend to encompass all such alternatives, modifications, equivalents, and variations as fall within the spirit and scope of the present invention.

Appendix A

Abbreviations, abbreviations and terminology

AS - Appliance Status (e.g., AS=1 - Cooking, AS=2 - Idle, AS=0 - Off)

BD-Balanced Damper

BDP - Balance Damper Position (e.g., BDP = 0 - closed; BDP = 1 - open)

BDPdesign - Balanced damper position corresponding to hood design airflow Qdesign. When VFD = VFDdesign is achieved

DCV - Controlled Ventilation Required

dTcook - the preset temperature above Tspace when the IR sensor interprets the appliance as being in idle state, AS = 2.

dTIR - the temperature difference between IRT and Tspace (eg, dTIR = IRT - Tspace).

dTIRcal - dTIR stored in memory during the first calibration procedure for each IR sensor.

dTIRmax - a preset threshold of the absolute difference |dTIR - dTIRcal| that indicates the IR sensor needs cleaning and recalibration

dTspace - The preset temperature difference between Tex and Tspace when the cookware status is interpreted as "all appliances under hood off" (eg, AS = 0). An exemplary default value is 9°F.

FRT - Fluctuations in the radiant temperature of the cooking surface of an appliance.

i - index, corresponding to the number of hoods.

IRT - Infrared sensor temperature reading, °F

IRTmin - minimum temperature reading above which the IR sensor detects that the appliance is in idle state (eg AS = 2). IRTmin = Tspace + dTcook.

kAirflowDesign - Ratio of mass exhaust airflow. Ratio of total actual airflow to total design airflow for a hood equipped with a DCV

Kf - hood coefficient, used to calculate hood exhaust flow

kFilterClogged - threshold airflow coefficient used to detect clogged filters, default value is 1.1

kFilterMissing - threshold airflow coefficient used to detect filter missing, default value is 1.1

Kidle-idle counterflow coefficient, Kidle＝1-Qidle/Qdesign

M - hood exhaust flow, lb/h

Mdesign_tot - Total design exhaust mass airflow for all hoods in a kitchen equipped with a DCV system, lb/h

n - index corresponding to the number of IR sensors in the housing.

Patm - atmospheric pressure, inches of mercury.

PstDesign, inches of water column - Minimum static pressure in the main exhaust duct when all hoods are calibrated and running at design airflow Qdesign.

Q - hood exhaust flow, cfm

Qdesign - hood design airflow, cfm

Qdesign_tot - total design exhaust flow for all hoods in a kitchen equipped with a DCV system, cfm

Qdesigni - New hood design airflow obtained in the calibration procedure for multiple hoods connected to a single exhaust fan, cfm

Qidle - the preset hood airflow in idle state when all appliances under the hood are in idle state (by default Qidle = 0.8 Qdesign)

Qtot - total design exhaust flow for all hoods in a kitchen equipped with a DCV system, cfm

TAB - Test and balancing port in the hood. A pressure sensor is connected to the TAB port to measure the pressure difference and calculate the hood exhaust flow.

Tex - hood exhaust temperature

Tex_min - minimum exhaust temperature when the appliance status is detected as idle, AS = 2

Tfire - pre-set limit for exhaust gas temperature, close to the temperature of the fusible link, °F. When Tex>Tfire - fire alarm is generated.

TimeCook - pre-set cooking time, by default TimeCook = 7 minutes.

TimeOR - Override time. The time the hood airflow is kept at the design level Q = Qdesign when the override button on the hood is pressed. By default, TimeOR = 1 min

Tmax - The preset maximum hood exhaust temperature at which the hood operates at the design exhaust flow.

Tspace-space temperature, °F

VFDdesign - VFD setting, corresponding to Qdesign (VFD = 1 - fan full speed; VFD = 0 - fan off)

VFDidle-VFD setting, corresponding to Qidle

Claims (6)

1. An exhaust ventilation system suitable for cooking utensils, the exhaust ventilation system comprising an exhaust hood, the exhaust ventilation system comprising: A control module coupled to a motor controller and adapted to determine the state of the cooking appliance based on a measured radiant temperature and a measured exhaust temperature, and adapted to control the exhaust flow rate based on the determined state of the cooking appliance; An exhaust fan, used to remove exhaust generated by the cooking appliance; A motor controller, coupled to the control module and the exhaust fan; At least one sensor, coupled to the control module and adapted to measure the radiant temperature of the surface of the cooking utensil; At least one temperature sensor, coupled to the control module and attached to the exhaust hood, is provided to measure the temperature of the exhaust gas. An ambient temperature sensor is used to measure the ambient temperature near the exhaust hood. The status of the cooking utensil includes cooking status, idle status, and off status; The control module controls the exhaust flow rate Q by varying the exhaust flow rate between the designed exhaust flow rate Qdesign, the idle exhaust flow rate Qidle, and the closed exhaust flow rate based on changes in the appliance status. The idle exhaust velocity is determined according to formula (a). Wherein, Tex is the exhaust temperature, Tspace is the ambient temperature, dTspace is the temperature difference between the exhaust temperature and the ambient temperature when the cooking appliance is in the closed state, Tmax is the determined maximum exhaust temperature, and Qdesign is the predetermined design exhaust flow rate for the exhaust hood. 2. The system according to claim 1, wherein the control module determines the variation of the radiant temperature, and when the radiant temperature varies, the control module determines whether the cooking appliance is in a cooking state or an idle state by calculating Q according to formula (a); then, when the radiant temperature varies and the radiant temperature is greater than a predetermined minimum radiant temperature, the control module determines that the cooking appliance is in a cooking state; when the radiant temperature does not vary, the control module determines that the cooking appliance is in an idle state; when the radiant temperature does not vary and the radiant temperature is less than or equal to a predetermined minimum radiant temperature, the control module determines that the cooking appliance is in an off state. 3. In the system of claim 2, the cooking appliance is switched to cooking when the exhaust temperature is greater than the determined maximum exhaust temperature Tmax and a change in radiation temperature is detected, or when the timer has not expired since the controller previously determined the cooking state. 4. In the system according to claim 3, the cooking appliance is first determined to be in a cooking state or an idle state, and then the controller determines the cooking state based on the variation of radiant temperature. 5. The system according to claim 1, wherein the control module controls the exhaust flow rate by controlling the rotational speed of the exhaust fan. 6. In the system according to claim 1, when the radiation temperature changes and is greater than a predetermined minimum radiation temperature, the control module determines that the cooking appliance is in a cooking state; when the radiation temperature does not change, the control module determines that the cooking appliance is in an idle state; when the radiation temperature does not change and is less than or equal to a predetermined minimum radiation temperature, the control module determines that the cooking appliance is in a closed state.