Method and apparatus for reheat dehumidification with variable air volume

• US 10,337,755 B2
• Filed: 11/30/2015
• Issued: 07/02/2019
• Est. Priority Date: 11/30/2015
• Status: Active Grant

• Current Assignee: Lennox Industries Incorporated (Lennox International Incorporated)
• Original Assignee: Lennox Industries Incorporated (Lennox International Incorporated)
• Inventors: Goel, Rakesh, Phillips, Derek
• Primary Examiner(s): Trpisovsky, Joseph F
• Application Number:
  US14/954,531
• Publication Number:
  US 20170153037A1
• Time in Patent Office: 1,310 Days
• Field of Search: 62 93, 62115
• 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 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 11/83 by controlling the supply of heat-exchange fluids to heat-exchangers
• CPC Class Codes: F24F 11/86 by controlling compressors within refrigeration or heat pump circuits
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 2140/00 Control inputs relating to system states
• CPC Class Codes: F24F 2140/20 Heat-exchange fluid temperature
• CPC Class Codes: F24F 2221/16 mounted on the roof
• 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 39/028 having distributing means
• CPC Class Codes: F25B 41/42 Arrangements for diverging or converging flows, e.g. branch lines or junctions
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

The HVAC system includes an evaporator coil and a metering device fluidly coupled to the evaporator coil via a distribution line. The HVAC system includes a variable-speed circulation fan for circulating air around the evaporator coil. A temperature sensor is thermally exposed to the distribution line. At least one controller is operatively coupled to the temperature sensor and to the variable-speed circulation fan. The at least one controller adjusts a speed of the variable-speed circulation fan to increase latent capacity of the HVAC system responsive to a determination that a temperature of fluid in the distribution line exceeds an optimal distribution line temperature.

Claims

1. A heating, ventilation, and air conditioning (HVAC) system for regulating humidity of an enclosed space, the system comprising:

an evaporator coil;

a metering device fluidly coupled to the evaporator coil via a distribution line;

a variable-speed circulation fan for circulating air around the evaporator coil;

a temperature sensor thermally exposed to the distribution line;

at least one controller operatively coupled to the temperature sensor and to the variable-speed circulation fan;

wherein the at least one controller is configured to;

determine a latent cooling load based on a relative-humidity setpoint;

determine an optimal distributor line temperature that corresponds to the latent cooling load;

compare a measured distributor line temperature to the optimal distributor line temperature;

responsive to a determination that the measured distributor line temperature exceeds the optimal distributor line temperature, reduce a speed of the variable-speed circulation fan; and

responsive to a determination that the measured distributor line temperature falls below the optimal distributor line temperature, increase the speed of the variable-speed circulation fan.

2. The system of claim 1, comprising:

a condenser coil fluidly coupled to the metering device;

a compressor fluidly coupled to the condenser coil and the evaporator coil; and

a condenser fan for circulating air around the condenser coil.

3. The system of claim 1, wherein the at least one controller is configured to detect a relative humidity of the enclosed space.

4. The system of claim 3, wherein the at least one controller is configured to calculate the optimal distribution line temperature based on the relative humidity of the enclosed space.

5. The system of claim 4, wherein the at least one controller is configured to modulate the speed of the variable-speed circulation fan to maintain the optimal distribution line temperature.

6. The system of claim 4, wherein the optimal distribution line temperature is calculated based on at least one of indoor dry-bulb temperature, relative humidity, and outdoor temperature.

7. The system of claim 1, wherein the temperature sensor is configured to measure the distribution line temperature as a proxy for an evaporator coil surface temperature.

8. The system of claim 1, wherein the HVAC system comprises a rooftop unit.

9. The system of claim 1, wherein the at least one controller is configured to communicate with at least one of a monitoring device and a communication device.

10. The system of claim 1, wherein the at least one controller is configured to reduce the speed of the variable-speed circulation fan thereby lowering a temperature of the evaporator coil.

11. The system of claim 1, wherein the temperature sensor comprises a thermistor.

12. A method of regulating humidity of an enclosed space, the method comprising:

measuring a distributor-line temperature associated with a heating, ventilation, and air conditioning (HVAC) system;

determining, via at least one controller, a latent cooling load based at least in part on environmental conditions;

calculating, via the at least one controller, an optimal distributor-line temperature corresponding to the latent cooling load;

comparing the measured distributor-line temperature to the optimal distributor-line temperature;

determining if the measured distributor-line temperature exceeds the optimal distributor-line temperature;

responsive to a determination that the distributor-line temperature exceeds the optimal distributor-line temperature, adjusting, via the at least one controller, a speed of a variable-speed circulation fan to lower an evaporator coil surface temperature; and

wherein the adjusting the speed of the variable-speed circulation fan increases a latent capacity of the HVAC system.

13. The method of claim 12, wherein the step of measuring comprises measuring a saturated suction temperature of the HVAC system.

14. The method of claim 12, wherein increasing the latent capacity of the HVAC system facilitates dehumidification of conditioned air without an associated change of temperature of the conditioned air.

15. The method of claim 12, comprising detecting, via the at least one controller, a relative humidity of an enclosed space.

16. The method of claim 15, wherein the at least one controller is configured to modulate the speed of the variable-speed circulation fan to maintain the optimal distributor-line temperature.

17. The method of claim 12, wherein the adjusting comprises decreasing a speed of the variable-speed circulation fan.

18. The method of claim 12, comprising, responsive to a determination that the distributor-line temperature does not exceed the optimal distributor-line temperature, maintaining, via the at least one controller, a speed of a variable-speed circulation fan.

19. A heating, ventilation, and air conditioning (HVAC) system for regulating humidity of an enclosed space, the system comprising:

an evaporator coil;

a metering device fluidly coupled to the evaporator coil via a distribution line;

a variable-speed circulation fan for circulating air around the evaporator coil;

a temperature sensor thermally exposed to the distribution line;

at least one controller operatively coupled to the temperature sensor and to the variable-speed circulation fan;

a condenser coil fluidly coupled to the metering device;

a compressor fluidly coupled to the condenser coil and the evaporator coil;

a condenser fan for circulating air around the condenser coil;

wherein the at least one controller is configured to;

determine a latent cooling load based on a relative-humidity setpoint;

determine an optimal distributor line temperature that corresponds to the latent cooling load;

compare a measured distributor line temperature to the optimal distributor line temperature;

responsive to a determination that the measured distributor line temperature exceeds the optimal distributor line temperature, reduce a speed of the variable-speed circulation fan; and

responsive to a determination that the measured distributor line temperature falls below the optimal distributor line temperature, increase the speed of the variable-speed circulation fan.