Claims
- 1. A method of temperature control in a cryogenic system comprising:
providing a motor speed sensor, the motor speed sensor being operatively coupled to a proportional-integral-derivative controller, the motor speed sensor determining a motor speed and sending the motor speed to the proportional-integral-derivative controller; providing a pressure sensor, the pressure sensor being operatively coupled to the proportional-integral-derivative controller, the pressure sensor determining a cryogenic pressure, and sending the pressure to the proportional-integral-derivative controller; providing a temperature sensor in the conditioned space, the temperature sensor being operatively coupled to the proportional-integral-derivative controller, the temperature sensor measuring a temperature within the conditioned space and sending the temperature to the proportional-integral-derivative controller; providing a deprived integral region in a proportional band to the proportional-integral-derivative controller when the motor speed is close to a motor speed set point; and generating an overriding control signal at the proportional-integral-derivative controller when the temperature and the pressure are beyond a temperature set point and a pressure set point.
- 2. The method of claim 1, wherein the temperature is a return air temperature, and wherein with the system in a null mode, generating the control signal comprises:
determining an ambient temperature; providing a switch point temperature; providing a lockout temperature; comparing the returned air temperature with the switch point temperature; comparing the ambient temperature and the lockout temperature; and locking out a heat mode when the returned air temperature is less than the switch point and the ambient temperature is greater than the lockout temperature.
- 3. The method of claim 2, wherein the switch point temperature is a null-to-heat switch point temperature.
- 4. The method of claim 1, wherein the temperature is a return air temperature, and wherein with the system in a null mode, generating the control signal comprises:
determining an ambient temperature; providing a switch point temperature; providing a lockout temperature; comparing the returned air temperature with the switch point temperature; comparing the ambient temperature and the lockout temperature; and locking out a cool mode when the returned air temperature is greater than the switch point and the ambient temperature is less than the lockout temperature.
- 5. The method of claim 4, wherein the switch point temperature is a heat-to-cool switch point temperature.
- 6. The method of claim 1, wherein generating the control signal comprises generating a top freeze protection signal when the temperature has fallen below a predetermined temperature for a predetermined amount of degree minutes.
- 7. The method of claim 6, wherein the predetermined temperature is approximately 32° F., and the predetermined amount of degree minutes is approximately 250.
- 8. The method of claim 1, further comprising:
determining if the motor speed is within the deprived integral region; and accumulating an integral error at a rate that is half of an original rate.
- 9. The method of claim 1, wherein with the system in a high speed cool mode, the method further comprises:
providing a speed cutoff; and closing an expansion valve to approximately one percent when the speed is greater than the speed cutoff.
- 10. The method of claim 1, wherein the cryogenic pressure is determined at an end of an evaporator coil.
- 11. A method of controlling a cryogenic temperature system, wherein the cryogenic system uses a proportional-integral-derivative control, and controls the temperature within a conditioned space, the method comprising:
determining a motor speed; determining a cryogenic pressure; determining a plurality of temperatures inside the conditioned space; determining a plurality of temperatures outside the conditioned space; determining a new motor speed based on the motor speed, the pressure, the temperatures, and a plurality of predetermined temperature and pressure tables; and actuating the motor based on the new motor speed.
- 12. The method of claim 11, wherein the temperatures include a return air temperature and an ambient temperature, and wherein with the system in a null mode, the method further comprises:
providing a switch point temperature; providing a lockout temperature; comparing the returned air temperature with the switch point temperature; comparing the ambient temperature and the lockout temperature; and locking out a heat mode when the returned air temperature is less than the switch point and the ambient temperature is greater than the lockout temperature.
- 13. The method of claim 12, wherein the switch point temperature is a null-to-heat switch point temperature.
- 14. The method of claim 11, wherein the temperatures include a return air temperature and an ambient temperature, and wherein with the system in a null mode, the method further comprises:
providing a switch point temperature; providing a lockout temperature; comparing the returned air temperature with the switch point temperature; comparing the ambient temperature and the lockout temperature; and locking out a cool mode when the returned air temperature is greater than the switch point and the ambient temperature is less than the lockout temperature.
- 15. The method of claim 14, wherein the switch point temperature is a heat-to-cool switch point temperature.
- 16. The method of claim 11, further comprising generating a top freeze protection signal when the temperature has fallen below a predetermined temperature for a predetermined amount of degree minutes.
- 17. The method of claim 11, wherein the predetermined temperature is approximately 32° F., and the predetermined amount of degree minutes is approximately 250.
- 18. The method of claim 11, further comprising accumulating an integral error at a rate that is half of an original rate if the motor speed is within a deprived integral region.
- 19. The method of claim 11, wherein with the system in a high speed cool mode, the method further comprises:
providing a speed cutoff; and closing an expansion valve to approximately one percent when the speed is greater than the speed cutoff.
- 20. The method of claim 11, wherein the cryogenic pressure is determined at an end of an evaporator coil.
- 21. A method of conserving a heat absorbing liquid in a cryogenic temperature control system, wherein the system includes a controller and a motor, and wherein the controller adjusts a motor speed, the method comprising:
setting a target motor speed; averaging the motor speed over a predetermined amount of time after the system has entered a temperature controlling mode; regulating the heat absorbing liquid after the predetermined amount of time; resetting the target motor speed to a new target motor speed if the average motor speed is less than or equal to a predetermined speed below the target motor speed, the new target motor speed being set below the average motor speed by a predetermined motor speed value; and adjusting the motor speed such that the motor speed approaches the new target motor speed for a second predetermined amount of time.
- 22. The method of claim 21, wherein resetting the target motor speed and adjusting the motor speed are repeated.
- 23. The method of claim 21, wherein the predetermined amount of time is approximately two minutes.
- 24. The method of claim 21, wherein the predetermined speed is approximately 15 RPM.
- 25. The method of claim 21, wherein the predetermined motor speed value is approximately 40.
- 26. A cryogenic temperature control system comprising:
a conditioned space containing a gas and a load, the gas having a gas heat and thereby also having a temperature; a heat exchanger in the conditioned space, the heat exchanger having a heat absorbing liquid, and the heat absorbing liquid absorbing the gas heat within the conditioned space thereby lowering the temperature within the conditioned space; a heat source, the heat source releasing heat into the conditioned space thereby increasing the temperature within the conditioned space; a fan adjacent to the heat source and the heat exchanger, the fan circulating the gas in the conditioned space thereby having a fan speed; a temperature sensor determining a temperature within the conditioned space; a pressure sensor determining a cryogenic pressure; and a controller operatively coupled to the fan, the temperature sensor, the pressure sensor, the heat exchanger, and the heat source, the controller receiving the temperature from the temperature sensor, receiving the pressure from the pressure sensor, adjusting the fan speed within the proportional band based on the temperature, the pressure, and the fan speed.
- 27. The system of claim 26, wherein the temperature sensor is a first temperature sensor, the system further comprising a second temperature sensor, the second temperature sensor measuring a temperature outside the conditioned space.
- 28. The system of claim 26, further comprising a plurality of temperature pressure conversion tables, the tables converting a pressure into a translation temperature, and the translation temperature determining whether the system enters a super heat mode.
- 29. The system of claim 26, wherein the cryogenic pressure is determined at an end of the heat exchanger.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. §119 to provisional patent application serial No. 60/295,708, filed on Jun. 4, 2001.
Provisional Applications (1)
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Number |
Date |
Country |
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60295708 |
Jun 2001 |
US |