HVAC unit with hot gas reheat

• US 10,247,430 B2
• Filed: 10/12/2016
• Issued: 04/02/2019
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Blanton, Norman J., Wilson, Stephen C., Pickle, Stephen B.
• Primary Examiner(s): Vazquez, Ana M
• Application Number:
  US15/291,975
• Publication Number:
  US 20170030600A1
• Time in Patent Office: 902 Days
• CPC Class Codes: F24F 1/00075 receiving air from a central station
• CPC Class Codes: F24F 1/00077 receiving heat exchange fluid entering and leaving the unit as a liquid
• 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 11/61 using timers
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/64 using pre-stored data
• CPC Class Codes: F24F 11/65 for selecting an operating mode
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 11/86 by controlling compressors within refrigeration or heat pump circuits
• CPC Class Codes: F24F 11/871 by controlling outdoor fans
• CPC Class Codes: F24F 13/20 Casings or covers
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 2140/12 Heat-exchange fluid pressure
• CPC Class Codes: F24F 2221/183 combined with a hot-water boiler
• CPC Class Codes: F24F 2221/54 Heating and cooling, simultaneously or alternatively
• CPC Class Codes: F24F 3/044 Systems in which all treatment is given in the central station, i.e. all-air systems
• CPC Class Codes: F24F 3/153 with subsequent heating, i.e. with the air, given the required humidity in the central station, passing a heating element to achieve the required temperature
• CPC Class Codes: F25B 2600/0271 the discharge pressure
• CPC Class Codes: F25B 2600/111 : of condenser fans
• CPC Class Codes: F25B 41/20 : Disposition of valves, e.g. of on-off valves or flow control valves expansion valves F25B41/31
• CPC Class Codes: F25B 47/022 : hot gas defrosting
• CPC Class Codes: F25B 5/02 : arranged in parallel
• CPC Class Codes: F25B 7/00 : Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit F25B9/00 takes precedence
• CPC Class Codes: F25D 17/06 : by forced circulation
• CPC Class Codes: Y02B 30/70 : Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

The present disclosure is directed to a single compressor HVAC system with hot gas reheat. The system includes a single compressor, a pair of condensers, a reheat heat exchanger, an evaporator, and an expansion device. Within the system, the refrigerant exiting the compressor is separated into two portions. In the cooling mode, the first and second portions of the refrigerant are directed from the compressor through the two condensers in parallel. In the reheat mode, the first portion of the refrigerant is directed through the first condenser, while the second portion of the refrigerant is directed through the reheat heat exchanger. The system also may include a head pressure control device that is designed to maintain the compressor discharge pressure within a desired range by adjusting the condenser fan speed.

Claims

1. A heating, ventilating, or air conditioning system, comprising:

a first refrigerant loop configured to circulate a first portion of refrigerant in a first operating mode and in a second operating mode;

a first condenser of the first refrigerant loop configured to receive and to condense the first portion of the refrigerant in the first operating mode and the second operating mode;

a second refrigerant loop configured to circulate a second portion of the refrigerant in the first operating mode but not in the second operating mode;

a second condenser of the second refrigerant loop configured to receive and to condense the second portion of the refrigerant in the first operating mode but not in the second operating mode;

a third refrigerant loop configured to circulate the second portion of the refrigerant in the second operating mode but not in the first operating mode; and

a reheat heat exchanger of the third refrigerant loop configured to transfer heat from the second portion of the refrigerant to a conditioned space to condense the second portion of the refrigerant in the second operating mode but not in the first operating mode; and

wherein the first portion of the refrigerant exiting the first condenser is configured to combine with the second portion of the refrigerant exiting the reheat heat exchanger in the second operating mode.

2. The heating, ventilating, or air conditioning system of claim 1, comprising an expansion device disposed along the first refrigerant loop, the second refrigerant loop, and the third refrigerant loop, wherein the first portion of the refrigerant exiting the first condenser is configured to combine with the second portion of the refrigerant exiting the second condenser prior to flowing through the expansion device in the first operating mode and the first portion of the refrigerant exiting the first condenser is configured to combine with the second portion of the refrigerant exiting the reheat heat exchanger prior to flowing through the expansion device in the second operating mode.

3. The heating, ventilating, or air conditioning system of claim 1, wherein the reheat heat exchanger and the first condenser each comprise approximately the same refrigerant volume or the first condenser comprises a refrigerant volume greater than the reheat heat exchanger.

4. The heating, ventilating, or air conditioning system of claim 1, wherein the first condenser and the second condenser each comprise approximately the same refrigerant volume or the first condenser comprises a refrigerant volume greater than the second condenser.

5. The heating, ventilating, or air conditioning system of claim 1, comprising a three-way valve configured to switch between a first position corresponding to the first operating mode and a second position corresponding to the second operating mode, wherein the three-way valve is configured to direct the first portion of the refrigerant into the first condenser and direct the second portion of the refrigerant into the second condenser when in the first position, and wherein the three-way valve is configured to direct the first portion of the refrigerant into the first condenser and direct the second portion of the refrigerant into the reheat heat exchanger when in the second position.

6. The heating, ventilating, or air conditioning system of claim 5, wherein the three-way valve is disposed along the first refrigerant loop downstream of an inlet to the first condenser and disposed along the second refrigerant loop upstream of the second condenser with respect to a flow of the refrigerant.

7. The heating, ventilating, or air conditioning system of claim 1, comprising a compressor configured to circulate the refrigerant through the first refrigerant loop, the second refrigerant loop, the third refrigerant loop, or any combination thereof.

8. The heating, ventilating, or air conditioning system of claim 7, comprising a refrigerant recovery circuit configured to drain the second portion of the refrigerant from the second condenser of the second refrigerant loop to the third refrigerant loop in the second operating mode.

9. The heating, ventilating, or air conditioning system of claim 7, comprising a refrigerant recovery circuit configured to drain the second portion of the refrigerant from the reheat heat exchanger of the third refrigerant loop to the second refrigerant loop in the first operating mode.

10. The heating, ventilating, or air conditioning system of claim 1, comprising a controller configured to switch the system between the first operating mode and the second operating mode based at least on first feedback received from a temperature sensor configured to measure a temperature of the conditioned space and second feedback received from a dehumidistat.

11. A system, comprising:

a compressor configured to circulate a refrigerant through a refrigerant circuit;

a first condenser disposed along the refrigerant circuit, wherein the first condenser is configured to receive and to condense a first portion of the refrigerant in a first operating mode and a second operating mode;

a second condenser disposed along the refrigerant circuit, wherein the second condenser is configured to receive and to condense a second portion of the refrigerant in the first operating mode but not in the second operating mode, wherein the first condenser and the second condenser are configured to operate in parallel with respect to a flow of the refrigerant in the first operating mode;

a reheat heat exchanger disposed along the refrigerant circuit, wherein the reheat heat exchanger is configured to transfer heat from the second portion of the compressed refrigerant to a conditioned space to condense the second portion of the refrigerant in the second operating mode but not in the first operating mode, wherein the first condenser and the reheat heat exchanger are configured to operate in parallel with respect to the flow of the refrigerant in the second operating mode; and

a three-way valve disposed along the refrigerant circuit, wherein the three-way valve is configured to direct the refrigerant from the compressor and through the first and second condensers during the first operating mode, and wherein the three-way valve is configured to direct the refrigerant from the compressor and through the first condenser and the reheat heat exchanger in the second operating mode.

12. The system of claim 11, comprising a refrigerant recovery circuit configured to drain the second portion of the refrigerant from the second condenser to an active refrigerant loop during the second operating mode, wherein the active refrigerant loop is configured to circulate the second portion of the refrigerant through the reheat heat exchanger and not through the second condenser.

13. The system of claim 11, comprising a refrigerant recovery circuit configured to drain the second portion of the refrigerant from the reheat heat exchanger to an active refrigerant loop during the first operating mode, wherein the active refrigerant loop is configured to circulate the second portion of the refrigerant through the second condenser and not through the reheat heat exchanger.

14. The system of claim 11, comprising an isolation device disposed downstream of the reheat heat exchanger, wherein the isolation device is configured to facilitate unidirectional flow of the second portion of the refrigerant from the reheat heat exchanger to the compressor and to block the flow of the second portion of the refrigerant to the reheat heat exchanger in the first operating mode.

15. The system of claim 11, comprising an isolation device disposed downstream of the second condenser and upstream of an outlet of the first condenser with respect to the flow of the refrigerant, wherein the isolation device is configured to facilitate unidirectional flow of the second portion of the refrigerant from the second condenser to the compressor and to block the flow of the second portion of the refrigerant to the second condenser in the second operating mode.

16. The system of claim 11, comprising a pressure control device configured to adjust a speed of one or more fans of the first condenser based on a discharge pressure of the refrigerant exiting the compressor.

17. A method, comprising:

circulating a refrigerant through a refrigerant circuit using a compressor;

directing a first portion of the refrigerant from the compressor toward a first condenser disposed along the refrigerant circuit in a first operating mode and in a second operating mode;

directing a second portion of the refrigerant from the compressor toward a second condenser disposed along the refrigerant circuit in the first operating mode but not in the second operating mode, wherein the first condenser and the second condenser are configured to operate in parallel with respect to a flow of the refrigerant in the first operating mode; and

directing the second portion of the refrigerant from the compressor toward a reheat heat exchanger disposed along the refrigerant circuit instead of toward the second condenser in the second operating mode but not in the first operating mode, wherein the first condenser and the reheat heat exchanger are configured to operate in parallel with respect to the flow of the refrigerant in the second operating mode.

18. The method of claim 17, comprising adjusting a position of a three-way valve disposed along the refrigerant circuit to switch between the first operating mode and the second operating mode.

19. The method of claim 18, wherein adjusting the position of the three-way valve disposed along the refrigerant circuit to switch between the first operating mode and the second operating mode comprises adjusting the position of the three-way valve based at least on a temperature of a conditioned space, a humidity level of the conditioned space, or both.

20. The method of claim 17, comprising measuring a pressure of the refrigerant exiting the compressor and adjusting a fan speed of the first condenser based on the pressure of the refrigerant exiting the compressor.