ENERGY EFFICIENT DEHUMIDIFYING REFRIGERATION SYSTEM

• US 20140345307A1
• Filed: 05/23/2013
• Published: 11/27/2014
• Est. Priority Date: 05/23/2013
• Status: Abandoned Application

• Current Assignee: Air To Water Technologies, Inc.
• Original Assignee: Air To Water Technologies, Inc.
• Inventors: Bagley, Jeffrey William, Lucia, Keith Gregory
• Application Number:
  US13/900,852
• Publication Number:
  US 20140345307A1
• Time in Patent Office: Days
• US Class Current: 62/115
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/49 ensuring correct operation, e.g. by trial operation or configuration checks
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 3/1405 in which the humidity of the air is exclusively affected by contact with the evaporator of a closed-circuit cooling system or heat pump circuit
• CPC Class Codes: F25B 2400/075 with parallel compressors
• CPC Class Codes: F25B 2500/19 Calculation of parameters
• CPC Class Codes: F25B 2600/0253 with variable speed
• CPC Class Codes: F25B 2600/0272 the suction pressure
• CPC Class Codes: F25B 2600/111 of condenser fans
• CPC Class Codes: F25B 2600/112 of evaporator fans
• CPC Class Codes: F25B 2600/2513 Expansion valves
• CPC Class Codes: F25B 2700/1933 Suction pressures
• CPC Class Codes: F25B 2700/21172 at the inlet
• CPC Class Codes: F25B 2700/21174 of the refrigerant at the inlet of the evaporator
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

An evaporator setpoint temperature for a refrigeration system is adjusted by an electronic control module to maximize a ratio of volume of condensate produced per unit of electricity consumed. When the control module detects a change in the relative humidity of air entering an evaporator in the refrigeration system, the module determines the new dew point for the air, compensates the dew point value by a predetermined offset value, and changes the setpoint for refrigerant temperature in the evaporator to the compensated dew point value. The control module operates the refrigeration system to drive the evaporator temperature to the compensated dew point value. Refrigeration system parameters measured and modified by the control module include operating speed of compressors, number of operating compressors, refrigerant flow through an expansion valve, compressor suction pressure, and fan speeds for the condenser and evaporator.

Claims

1. An apparatus, comprising:

a refrigeration system comprising a first compressor and an evaporator connected in series in a closed fluid circuit;

a humidity sensor positioned to measure a relative humidity value for inlet air to said evaporator;

a first temperature sensor positioned to measure a temperature value for inlet air to said evaporator;

a second temperature sensor positioned to measure a temperature value for refrigerant in said evaporator; and

an electronic control module adapted to store a setpoint offset value, said electronic control module electrically connected to said humidity sensor, said first temperature sensor, and said second temperature sensor, said electronic control module adapted to compute a dew point temperature value from said relative humidity value and said temperature value for inlet air, said electronic control module adapted to adjust an operating of speed of said first compressor until said temperature value for refrigerant is approximately equal to a compensated evaporator setpoint temperature calculate by subtracting said setpoint offset value from said dew point temperature, and when said electronic control module receives a changed value of relative humidity from said humidity sensor, said electronic control module autonomously calculates a new dew point temperature and adjusts said operating speed of said first compressor until a new temperature value for said refrigerant is approximately equal to a new compensated evaporator setpoint temperature.

2. The apparatus of claim 1, further comprising an electronic expansion valve connected to said closed fluid circuit in series between said first compressor and said evaporator, wherein said electronic control module further comprises an expansion valve control output electrically connected to said electronic expansion valve;

and said electronic control module is adapted to adjust said electronic expansion valve and said operating speed of said first compressor until said new temperature value for said refrigerant is approximately equal to said new compensated evaporator setpoint temperature.

3. The apparatus of claim 1, further comprising a plurality of temperature sensors thermally coupled to said evaporator at different positions in said evaporator, wherein said electronic control module is adapted to calculate an average evaporator temperature value equal to the arithmetic mean of the temperature measured by each of said plurality of temperature sensors.

4. The apparatus of claim 3, wherein said electronic control module is adapted to adjust said operating of speed of said first compressor until said average evaporator temperature value is approximately equal to said compensated evaporator setpoint temperature.

5. The apparatus of claim 1, further comprising a second compressor connected to said closed fluid circuit in parallel with said first compressor, wherein said electronic control module adjusts said operating speed of said first compressor and an operating speed of said second compressor until said temperature value for refrigerant is approximately equal to said compensated evaporator setpoint temperature.

6. An apparatus, comprising:

an electronic control module comprising;

a central processor unit comprising electronic semiconductor devices arranged in a digital logic circuit;

a humidity sensor signal input adapted for sending a value of relative humidity to said central processor unit; and

a plurality of temperature sensor inputs, each adapted for sending a value of temperature to said central processor unit;

a compressor variable frequency drive (VFD) in data communication with said electronic control module;

a humidity sensor for measuring a value of relative humidity of air entering an evaporator in a refrigeration system;

a first temperature sensor for measuring a value of inlet air temperature; and

a second temperature sensor for measuring a value of refrigerant temperature, said electronic control module adapted to calculate a compensated evaporator setpoint value from said value of relative humidity and said value of inlet air temperature and send a signal to said compressor VFD to increase an operating speed of a compressor until said value of refrigerant temperature is approximately equal to said compensated evaporator setpoint value.

7. The apparatus of claim 6, further comprising an expansion valve control output in data communication with said electronic control module.

8. The apparatus of claim 6, further comprising a condenser fan VFD in data communication with said electronic control module.

9. The apparatus of claim 6, further comprising an evaporator fan VFD in data communication with said electronic control module.

10. A method, comprising the steps of:

measuring a first value of relative humidity at an air inlet for an evaporator in a refrigeration system;

measuring a first value of temperature at the air inlet for the evaporator;

determining a first value of dew point temperature from the first values of relative humidity and temperature at the air inlet for the evaporator;

assigning a value for setpoint offset;

calculating a first compensated setpoint value by subtracting the value of setpoint offset from the first value of dew point temperature; and

adjusting the flow of refrigerant in the refrigeration system until a measured value of refrigerant temperature in the evaporator is approximately equal to the first compensated setpoint value.

11. The method of claim 10, further comprising the steps of:

measuring a plurality of temperature values in the evaporator, wherein each of said plurality of temperature values in the evaporator is approximately equal to a value of refrigerant temperature at a different location in the evaporator;

calculating an average value of evaporator temperature as the arithmetic mean of the plurality of temperature values; and

adjusting the flow rate of refrigerant in the refrigeration system until the average value of evaporator temperature is approximately equal to the first compensated setpoint value.

12. The method of claim 10, wherein the setpoint offset is equal to a magnitude of difference in temperature between refrigerant flowing into the evaporator and refrigerant flowing out of the evaporator.

13. The method of claim 10, further comprising the steps of:

measuring a second value of relative humidity at the air inlet for the evaporator; and

comparing the first value of relative humidity to the second value of relative humidity and, when the magnitude of difference between the first and second values of relative humidity is greater than a selected magnitude of humidity change;

determining a second value of dew point temperature from the second value of relative humidity;

calculating a second compensated setpoint value by subtracting the value of setpoint offset from the second value of dew point temperature; and

adjusting the flow of refrigerant in the refrigeration system until the measured value of refrigerant temperature in the evaporator is approximately equal to the second compensated setpoint value.

14. The method of claim 15, further comprising the steps of:

measuring a second value of temperature at the air inlet for the evaporator;

comparing the first value of temperature at the air inlet to the second value of temperature at the air inlet, and when the magnitude of difference between the first and second values of temperature at the air inlet is greater than a selected magnitude of temperature change;

determining a second value of dew point temperature from the second value of temperature at the air inlet;

calculating a second compensated setpoint value by subtracting the value of setpoint offset from the second value of dew point temperature; and

adjusting the flow of refrigerant in the refrigeration system until the measured value of refrigerant temperature in the evaporator is approximately equal to the second compensated setpoint value.

15. The method of claim 10, further comprising the step of increasing the flow rate of refrigerant through an expansion valve when the measured value of refrigerant temperature in the evaporator is greater than the first compensated setpoint value.

16. The method of claim 10, further comprising the step of adjusting the operating speed of a first compressor in the refrigeration system until the measured value of refrigerant temperature in the evaporator is approximately equal to the first compensated setpoint value.

17. The method of claim 16, further comprising the step of comparing the operating speed of the first compressor to a maximum operating speed, and when magnitude of difference between the maximum operating speed and the operating speed is greater than a selected safety factor, starting a second compressor in a parallel fluid circuit with the first compressor.

18. The method of claim 16, further comprising the step of reducing the operating speed of the compressor when the measured value of refrigerant temperature in the evaporator is within a selected magnitude of temperature difference from 32°

F. (0°

C.).

19. The method of claim 10, wherein when the relative humidity of the inlet air changes, adjusting the flow of refrigerant to maintain a constant value for a rate of condensate collection.

20. The method of claim 10, wherein when the relative humidity of the inlet air changes, adjusting the flow of refrigerant to maintain a constant value for electrical power consumption.