Exhaust flow control system and method
A system and method for controlling the exhaust flow rate in an exhaust ventilation system including an exhaust hood positioned above a cooking appliance. The method can include measuring a temperature of the exhaust air in the vicinity of the cooking appliance, and measuring a radiant temperature of a surface of the cooking appliance, and determining an appliance status based on the measured exhaust air temperature and radiant temperature, and controlling the exhaust flow rate in response to the determined appliance status.
1. An exhaust ventilation system adapted for use with a cooking appliance that generates exhaust air, the exhaust ventilation system, comprising:
an exhaust hood positioned above the cooking appliance;
at least one temperature sensor attached to the exhaust hood and measuring temperature of exhaust air in a vicinity of the exhaust hood;
a radiant temperature sensor measuring radiant temperature of a surface of the cooking appliance;
a control module receiving a signal indicating the temperature of the exhaust air from the at least one temperature sensor and receiving a signal indicating the radiant temperature from the radiant temperature sensor,
the control module being coupled to a motor controller and configured to determine a status of the cooking appliance as at least one of
a cooking state,
an idle state, and
an off state based on
a mean of the radiant temperature, the temperature of the exhaust air, and fluctuation in the radiant temperature,
the control module further configured to determine the status as the cooking state in response to the measured radiant temperature increasing or decreasing at a rate faster than a predetermined threshold, and
the control module further configured to control an exhaust air flow rate based on the determined status of the cooking appliance;
an exhaust fan for removing exhaust air generated by the cooking appliance; and
the motor controller for controlling the exhaust fan coupled to the control module and the exhaust fan, wherein
the control module is configured to change the exhaust flow rate through the motor controller to design exhaust flow rate (Qdesign) when the cooking appliance is determined to be in the cooking state, to the idle exhaust flow rate (Qidle) when the appliance status is determined to be in the idle state, and to the off exhaust flow rate when the appliance is determined to be in the off state, and
wherein the control module determines that the cooking appliance is in the cooking state when there is a fluctuation in the radiant temperature and the radiant temperature is greater than a predetermined minimum radiant temperature, the cooking appliance is in the idle state when there is no fluctuation in the radiant temperature, and the cooking appliance is in the off state when there is no fluctuation in the radiant temperature and the radiant temperature is less than a minimum predetermined radiant temperature.
2. The system of claim 1 , wherein the at least one sensor for measuring
the radiant temperature is an infrared sensor.
3. The system of claim 1 , wherein the control module controls the exhaust air flow rate by controlling a speed of the exhaust fan.
4. The system of claim 1 , further comprising at least one motorized balancing damper attached to the exhaust hood to control a volume of the exhaust air that enters the exhaust hood.
5. The system of claim 4 , wherein the control module further controls the exhaust air flow rate by controlling a position of the at least one motorized balancing damper.
6. The system of claim 1 , further including a temperature sensor for measuring an ambient temperature of the air in the vicinity of the ventilation system.
7. The system of claim 6 , wherein the control module is further configured to determine a difference between the exhaust air temperature in the vicinity of the exhaust hood and the ambient temperature in the vicinity of the ventilation system.
8. The system of claim 7 , wherein, based on the determined temperature difference, the control module determines that the cooking appliance is in the cooking state when the exhaust air temperature is greater than or equal to a maximum predetermined ambient temperature, the cooking appliance is in the idle state when the exhaust air temperature is less than the predetermined maximum ambient temperature, and the cooking appliance is in the off state when the exhaust air temperature is less than a predetermined ambient temperature.
9. The system of claim 1 , wherein the system is calibrated before the control module controls the exhaust air flow.
10. The exhaust ventilation system according to claim 1 , wherein
the fan idle speed (Qidle) is determined according to the following equation:
Qidle
=
Qdesign
(
Tex
-
Tspace
+
dTspace
T
max
-
Tspace
+
dTspace
)
where Tex is the exhaust temperature, Tspace is the ambient temperature, dTspace is a predetermined temperature difference between the exhaust temperature and the ambient temperature, Tmax is a predefined maximum exhaust temperature, and Qdesign is a predefined design exhaust flow rate for the exhaust hood.
11. A control module for controlling an exhaust flow rate in an exhaust ventilating system comprising an exhaust hood positioned above a cooking appliance, the control module comprising:
a processor configured to receive a measured radiant temperature, and a measured exhaust air temperature as inputs from at least one radiant temperature sensor and at least one temperature sensor, respectively,
the processor being configured to determine a status of the cooking appliance as at least one of
a cooking state,
an idle state, and
an off state, based on
a mean of the radiant temperature, the temperature of the exhaust air, and fluctuation in the radiant temperature,
the control module further configured to determine the status as the cooking state in response to the measured radiant temperature increasing or decreasing at a rate faster than a predetermined threshold,
the control module further configured to control an exhaust fan motor controller based on the determined status of the cooking appliance,
the control module further configured to change the exhaust flow rate through the motor controller to design exhaust flow rate (Qdesign) when the cooking appliance is determined to be in the cooking state, to the idle exhaust flow rate (Qidle) when the appliance status is determined to be in the idle state, and to the off exhaust flow rate when the appliance is determined to be in the off state, and
wherein the control module determines that the cooking appliance is in the cooking state when there is a fluctuation in the radiant temperature and the radiant temperature is greater than a predetermined minimum radiant temperature, the cooking appliance is in the idle state when there is no fluctuation in the radiant temperature, and the cooking appliance is in the off state when there is no fluctuation in the radiant temperature and the radiant temperature is less than a minimum predetermined radiant temperature.
12. The control module of claim 11 , wherein the exhaust flow rate includes
a design exhaust flow rate (Qdesign), an idle exhaust flow rate (Qidle), and an off exhaust flow rate.
13. The control module of claim 11 , wherein the control module is configured to determine that the appliance is in the cooking state when the exhaust air temperature is greater than or equal to a maximum predetermined ambient temperature, that the appliance is in an idle state when the exhaust air temperature is less than the predetermined maximum ambient temperature, and that the appliance is in an off state when the exhaust air temperature is less than a predetermined ambient temperature.
14. The control module of claim 11 , wherein the control module controls the exhaust air flow by controlling the exhaust fan motor controller which controls a speed of an exhaust fan attached to the exhaust hood.
15. The control module of claim 11 , wherein the control module controls the exhaust air flow by controlling a position of at least one balancing damper attached to the exhaust hood.
16. The control module of claim 11 , wherein the control module further calibrates the system before changing the exhaust flow rate.
17. The control module according to claim 11 , wherein
the fan idle speed (Qidle) is determined according to the following equation:
Qidle
=
Qdesign
(
Tex
-
Tspace
+
dTspace
T
max
-
Tspace
+
dTspace
)
where Tex is the exhaust temperature, Tspace is the ambient temperature, dTspace is a predetermined temperature difference between the exhaust temperature and the ambient temperature, Tmax is a predefined maximum exhaust temperature, and Qdesign is a predefined design exhaust flow rate for the exhaust hood.
18. An exhaust ventilation system adapted for use with a cooking appliance, the exhaust ventilation system comprising:
an exhaust hood;
a radiant temperature sensor measuring radiant temperature of a surface of the cooking appliance;
a control module coupled to a motor controller and configured to determine a status of the cooking appliance as at least one of a cooking state, an idle state, and an off state based on at least a measured radiant temperature;
an exhaust fan for removing exhaust air generated by the cooking appliance;
the motor controller coupled to the control module and the exhaust fan, wherein
the control module is further configured to control an exhaust air flow rate through the motor controller based on the determined status of the cooking appliance,
the control module is further configured to determine that the status of the cooking appliance is one of the cooking state and the idle state in response to the measured radiant temperature exceeding a predetermined threshold,
the control module is further configured to determine that the cooking appliance is in the cooking state when the radiant temperature increases faster than a predetermined threshold and when the radiant temperature decreases faster than the predetermined threshold, and
the control module is further configured to set the exhaust flow rate to a design exhaust flow rate (Qdesign) through the motor controller when the cooking appliance is determined to be in the cooking state.
19. The exhaust ventilation system according to claim 18 , wherein the at least one radiant temperature sensor is an infra-red (IR) sensor.
20. The exhaust ventilation system according to claim 18 , further comprising:
at least one temperature sensor attached to the exhaust hood and measuring temperature of exhaust air in the vicinity of the exhaust hood.
21. The exhaust ventilation system according to claim 20 , wherein
the fan idle speed (Qidle) is determined according to the following equation:
Qidle
=
Qdesign
(
Tex
-
Tspace
+
dTspace
T
max
-
Tspace
+
dTspace
)
where Tex is the exhaust temperature, Tspace is the ambient temperature, dTspace is a predetermined temperature difference between the exhaust temperature and the ambient temperature, Tmax is a predefined maximum exhaust temperature, and Qdesign is a predefined design exhaust flow rate for the exhaust hood.