Dehumidification system

1. A dehumidification system comprising:

(a) a regeneration air flow path within which a regeneration air fan and a refrigeration system having an evaporator coil and a condenser coil are disposed, the evaporator and condenser coils sharing a common refrigerant, the regeneration air flow path having a regeneration air inlet and a regeneration air outlet, the evaporator coil and the condenser coil each being located in the regeneration air flow path, the evaporator coil being configured to cool air within the regeneration air flow path and being located between the regeneration air inlet and the condenser coil, the condenser coil being configured to heat air within the regeneration air flow path;

(b) a process air flow path having a process air inlet and a process air outlet within which a process air fan is disposed, the process air flow path being separate from the regeneration air flow path;

(c) a desiccant wheel partially disposed within the process air flow path between the process air inlet and the process air outlet, and partially disposed in the regeneration air flow path between the condenser coil of the refrigeration system and the regeneration air outlet;

(d) a recirculation air flow path having a recirculation air inlet and a recirculation air outlet and being in fluid communication with the regeneration air flow path, the recirculation air inlet being located between the regeneration air fan and the regeneration air outlet, the recirculation air outlet being located between the regeneration air inlet and the evaporator coil of the refrigeration system, the recirculation air flow path being arranged to allow for an air flow to be recirculated through the refrigeration system and the desiccant wheel by the regeneration air fan; and

(e) an air-to-air heat exchanger located entirely within the recirculation airflow path and having a first exchanger inlet, a first exchanger outlet, a second exchanger inlet, and a second exchanger outlet, the first exchanger inlet being connected to the regeneration fan, the first exchanger outlet being connected to an inlet side of the evaporator coil, the second exchanger inlet being connected to an outlet side of the evaporator coil, the second exchanger outlet being connected to the condenser.

2. The dehumidification system of claim 1 , wherein the refrigeration system further comprises a compressor.

3. The dehumidification system of claim 2 , wherein the compressor is a variable output compressor.

4. The dehumidification system of claim 1 , further comprising a control system for controlling the refrigeration system and the regeneration fan.

5. The dehumidification system of claim 4 , wherein the control system is a direct digital control system.

6. The dehumidification system of claim 1 , further comprising a heating coil in the recirculation air flow path.

7. A method for dehumidifying air in a process air flow path with air in a regeneration air flow path, the method comprising:

(a) directing a regeneration air flow stream through a first side of an air-to-air heat exchanger to sensibly cool the regeneration air flow stream;

(b) directing the regeneration air flow stream from the air-to-air heat exchanger first side through an evaporator coil of a refrigeration system;

(c) directing the regeneration air flow stream from the evaporator coil through a second side of the air-to-air heat exchanger to sensibly heat the regeneration air flow stream with regeneration air passing through the first side of the air-to-air heat exchanger;

(d) directing the regeneration air flow stream from the second side of the air-to-air heat exchanger through a condenser coil of the refrigeration system to sensibly heat the regeneration airflow stream, wherein the evaporator coil and condenser coil share a common refrigerant;

(e) directing the regeneration air flow stream from the condenser coil through a first side of a desiccant wheel to cool and humidify the regeneration air flow stream, wherein a second side of the desiccant wheel is in fluid communication with a the process air flow path to dehumidify the air in the process air flow path; and

(f) directing the regeneration air flow stream from the desiccant wheel back to the first side of the air-to-air heat exchanger with a regeneration fan.

8. The method of claim 7 , further including the step of heating the process air flow path with a second condenser coil of the refrigeration system.

9. The method of claim 8 , wherein the step of heating the process air flow path includes modulating a three-way control valve in the refrigeration system, the three-way valve being in communication with the first and second condenser coils of the refrigeration system.

10. The method of claim 9 , wherein the three-way control valve is modulated to allow for a compressor of the refrigeration system to operate within an operating envelope.

11. The method of claim 10 , wherein the three-way control valve is modulated to match a dehumidification load of the process air flow stream.

12. The method of claim 7 , wherein the refrigeration system includes at least one variable output compressor.

13. The method of claim 7 , further comprising a warm-up process step comprising the step of suspending the rotation of the wheel until a regeneration air temperature set point has been reached.

14. The method of claim 7 , wherein the air-to-air heat exchanger is a fixed plate heat exchanger.

15. A dehumidification system comprising:

(a) a recirculating regeneration airflow path including:

i. a regeneration air fan;

ii. an air-to-air heat exchanger having a first exchanger inlet extending to a first exchanger outlet and having a second exchanger inlet extending to a second exchanger outlet, wherein air flowing between the first exchanger inlet and outlet exchanges sensible heat with air flowing between the second exchanger inlet and outlet, the first exchanger inlet being connected to the regeneration fan;

iii. an evaporator cooling coil of a refrigeration system, the evaporator coil being connected to the first exchanger outlet;

iv. a condenser heat rejection coil of the refrigeration system, the condenser heat rejection coil sharing a common refrigerant with the evaporator coil and being connected to the second outlet of the air-to-air heat exchanger;

v. a desiccant wheel heat exchanger having a first side and a second side, the first side being connected to the condenser heat rejection coil at a first side inlet and connected to the regeneration fan at a first side outlet; and

(b) a process airflow path including:

i. a process air inlet connected to a second side inlet of the desiccant wheel second side;

ii. a process air fan connected to a second side outlet of the desiccant wheel second side.

16. The dehumidification system of claim 15 , wherein the process airflow path further includes a process air heating coil and a process air cooling coil.

17. The dehumidification system of claim 16 , wherein the process air heating and cooling coils are located downstream of the desiccant wheel second side.

18. The dehumidification system of claim 15 , wherein the air-to-air heat exchanger is a fixed plate heat exchanger.