Apparatus and method for dry cycle completion control in heat pump dryer by declining capacity indication by rolling average compressor watts or heat exchanger pressure or temperature

1. A method comprising the steps of:

in a heat pump clothes dryer operating on a mechanical refrigeration cycle, monitoring, as a function of time, at least one parameter, said at least one parameter in turn comprising at least one of:

working fluid temperature;

working fluid pressure; and

compressor power;

based on said monitoring, determining whether said at least one parameter monitored as said function of time reaches a predetermined decision condition; and

if said at least one parameter monitored as said function of time reaches the predetermined decision condition, powering down said mechanical refrigeration cycle,

wherein said monitoring as said function of time comprises sampling at uniform time intervals to obtain a plurality of samples.

2. The method of claim 1 , wherein the predetermined decision condition comprises a maxima of a curve of the at least one parameter monitored as said function of time.

3. The method of claim 1 , wherein the predetermined decision condition comprises a predetermined negative slope level of a curve of the at least one parameter monitored as said function of time.

4. The method of claim 1 , wherein said determining comprises periodically computing a slope value based on a predetermined previous number of said samples.

5. The method of claim 4 , wherein said predetermined previous number of said samples is at least three.

6. The method of claim 5 , wherein said periodic computation of said slope value comprises carrying out, for given ones of said uniform time intervals, a linear least-squares fit on said at least three previous samples.

7. The method of claim 6 , wherein said at least one parameter comprises said working fluid pressure.

8. The method of claim 7 , wherein said monitoring, is carried out at a midpoint of a condenser of said mechanical refrigeration cycle.

9. The method of claim 7 , wherein said monitoring is carried out at an inlet of a condenser of said mechanical refrigeration cycle.

10. The method of claim 6 , wherein said at least one parameter comprises said working fluid temperature.

11. The method of claim 10 , wherein said monitoring is carried out at a midpoint of a condenser of said mechanical refrigeration cycle.

12. The method of claim 10 , wherein said at least one parameter comprises said compressor power.

13. An apparatus comprising:

a mechanical refrigeration cycle arrangement comprising:

a working fluid; and

an evaporator, a condenser, a compressor, and an expansion device, cooperatively interconnected and containing said working fluid;

a drum to receive clothes to be dried;

a duct and fan arrangement configured to pass air over said condenser and through said drum;

a sensor located to sense at least one parameter, said at least one parameter comprising at least one of:

temperature of said working fluid;

pressure of said working fluid; and

power consumption of said compressor; and

a controller coupled to said sensor and said compressor, said controller being operative to:

monitor, as a function of time, said at least one parameter;

based on said monitoring, determine whether said at least one parameter monitored as said function of time reaches a predetermined decision condition; and

if said at least one parameter monitored as said function of time reaches the predetermined decision condition, power down said mechanical refrigeration cycle at least by causing said compressor to shut off,

wherein said controller is operative to monitor as said function of time by sampling at uniform time intervals to obtain a plurality of samples.

14. The apparatus of claim 13 , wherein said controller is further operative to, if said at least one parameter monitored as said function of time reaches said predetermined decision condition, power down said mechanical refrigeration cycle at least by causing at least one of a blower, a drum drive, a heater, a pump, and a lock to shut off.

15. The apparatus of claim 13 , wherein said controller is operative to determine by periodically computing a slope value based on a predetermined previous number of said samples.

16. The apparatus of claim 15 , wherein said predetermined previous number of said samples is at least three.

17. The apparatus of claim 16 , wherein said controller is operative to periodically compute said slope value by carrying out, for given ones of said uniform time intervals, a linear least-squares fit on said at least three previous samples.

18. The apparatus of claim 17 , wherein said at least one parameter comprises said working fluid pressure.

19. The apparatus of claim 18 , wherein said condenser has a midpoint and wherein said sensor is located at said midpoint of said condenser.

20. The apparatus of claim 18 , wherein said condenser has an inlet at wherein said sensor is located at said inlet of said condenser.

21. The apparatus of claim 17 , wherein said at least one parameter comprises said working fluid temperature.

22. The apparatus of claim 21 , wherein said condenser has a midpoint and wherein said sensor is located at said midpoint of said condenser.

23. The apparatus of claim 16 , wherein said at least one parameter comprises said compressor power.

24. The apparatus of claim 13 , wherein the predetermined decision condition comprises a maxima of a curve of the at least one parameter monitored as said function of time.