Dryer appliances and methods for diagnosing restrictions in dryer appliances

1. A method for diagnosing a restriction in a dryer appliance, the method comprising:

obtaining a plurality of temperature readings at a controller of the dryer appliance during each operation of the dryer appliance by intermittently measuring a temperature of inlet air to the dryer appliance from a temperature sensor mounted within a cabinet of the dryer appliance;

obtaining a heater status for a heater of the dryer appliance at the controller during each measurement of the temperature;

estimating an effective opening size equal to or smaller in relation to an actual opening size of an outlet assembly in the dryer appliance at the controller during each operation of the dryer appliance based on the temperature and heater status for each of the plurality of temperature readings, the estimating comprising

calculating a heater contribution rate for temperature and a decay rate for temperature for the plurality of temperature readings at the controller utilizing the temperature and heater status for each of the plurality of temperature readings, and

utilizing at least one of the heater contribution rate for temperature and the decay rate for temperature to estimate the effective opening size; and

transmitting a restriction signal from the controller when the effective opening size is less than a predetermined minimum size threshold,

wherein the effective opening size is correlated to the at least one of the heater contribution rate for temperature or the decay rate for temperature,

wherein the heater contribution rate for temperature includes a rate of temperature increase at an active status of the heater, and

wherein the decay rate for temperature includes a rate of temperature decrease at an inactive status of the heater.

2. The method of claim 1 , wherein the intermittent measuring occurs at a predetermined time interval.

3. The method of claim 1 , wherein the at least one of the heater contribution rate for temperature and the decay rate for temperature is the heater contribution rate for temperature.

4. The method of claim 1 , wherein the utilizing step comprises inputting the at least one of the heater contribution rate for temperature and the decay rate for temperature into a restriction characteristic function for the dryer appliance, and wherein an output of the restriction characteristic function is the effective opening size.

5. The method of claim 1 , further comprising assigning an operation time value to each operation of the dryer appliance.

6. The method of claim 5 , further comprising calculating an effective opening change rate at the controller for an operation of the dryer appliance based on the effective opening size and operation time value of a plurality of operations of the dryer appliance.

7. The method of claim 6 , further comprising calculating a remaining time value at the controller for an operation of the dryer appliance when the effective opening change rate is negative, the remaining time value based on the effective opening change rate for the operation of the dryer appliance, the effective opening size for the operation of the dryer appliance, and a predetermined cleaning size threshold, wherein the remaining time value for the operation of dryer appliance is an estimated time remaining before clearing of a restriction is required.

8. The method of claim 7 , further comprising transmitting the remaining time value from the controller.

9. The method of claim 6 , further comprising transmitting a no-cleaning signal from the controller when the effective opening change rate is zero.

10. The method of claim 6 , further comprising transmitting a clear-data signal from the controller when the effective opening change rate is positive.

11. A dryer appliance, comprising:

a cabinet defining an interior;

a drum positioned within the interior, the drum defining a chamber for receipt of articles for drying;

a heating assembly;

an inlet duct providing fluid communication between the drum and the heating assembly;

an outlet assembly, the outlet assembly comprising a vent duct and an exhaust conduit;

a temperature sensor; and

a controller, the controller in communication with the temperature sensor and the heating assembly and configured to initiate:

obtaining a plurality of temperature readings during each operation of the dryer appliance by intermittently measuring a temperature of inlet air to the dryer appliance;

obtaining a heater status for a heater of the heating assembly during each measurement of the temperature; and

estimating an effective opening size equal to or smaller in relation to an actual opening size of the outlet assembly in the dryer appliance during each operation of the dryer appliance based on the temperature and heater status for each of the plurality of temperature readings, the estimating comprising

calculating a heater contribution rate for temperature and a decay rate for temperature for the plurality of temperature readings utilizing the temperature and heater status for each of the plurality of temperature readings, and

utilizing at least one of the heater contribution rate for temperature and the decay rate for temperature to estimate the effective opening size,

wherein the effective opening size is correlated to the at least one of the heater contribution rate for temperature or the decay rate for temperature,

wherein the heater contribution rate for temperature includes a rate of temperature increase at an active status of the heater, and

wherein the decay rate for temperature includes a rate of temperature decrease at an inactive status of the heater.

12. The dryer appliance of claim 11 , wherein the temperature sensor is disposed in one of the inlet duct or the drum.

13. The dryer appliance of claim 11 , wherein the temperature readings are obtained from the temperature sensor.

14. The dryer appliance of claim 11 , wherein the controller is further configured to initiate:

assigning an operation time value to each operation of the dryer appliance; and

calculating an effective opening change rate for an operation of the dryer appliance based on the effective opening size and operation time value of a plurality of operations of the dryer appliance.

15. The dryer appliance of claim 14 , wherein the controller is further configured to initiate calculating a remaining time value for an operation of the dryer appliance when the effective opening change rate is negative, the remaining time value based on the effective opening change rate for the operation of the dryer appliance, the effective opening size for the operation of the dryer appliance, and a predetermined cleaning size threshold, wherein the remaining time value for the operation of dryer appliance is an estimated time remaining before clearing of a restriction is required.