System and method for using hot gas reheat for humidity control

• US 20050115254A1
• Filed: 12/30/2004
• Published: 06/02/2005
• Est. Priority Date: 11/08/2002
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: York International Corporation (Johnson Controls International plc)
• Inventors: Bellah, Stephen Wayne, Knight, John Terry, Pickle, Stephen Blake
• Granted Patent: US 7,434,415 B2
• Time in Patent Office: Days
• US Class Current: 62/176.100
• 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 2400/04 Refrigeration circuit bypassing means
• CPC Class Codes: F25B 2400/06 Several compression cycles arranged in parallel
• CPC Class Codes: F25B 2400/061 the capacity of the first system being different from the second
• CPC Class Codes: F25B 2400/19 Pumping down refrigerant from one part of the cycle to another part of the cycle, e.g. when the cycle is changed from cooling to heating, or before a defrost cycle is started
• 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 49/02 for compression type machines, plants or systems
• CPC Class Codes: F25B 6/02 arranged in parallel

Abstract

A humidity control method is provided for a multi-stage cooling system having two or more refrigerant circuits that balances humidity control and cooling demand. Each refrigerant circuit includes a compressor, a condenser and an evaporator. A hot gas reheat circuit having a hot gas reheat coil is connected to one of the refrigerant circuits and is placed in fluid communication with the output airflow from the evaporator of that refrigerant circuit to provide additional dehumidification to the air when humidity control is requested. The hot gas reheat circuit bypasses the condenser of the refrigerant circuit during humidity control. Humidity control is only performed during cooling operations and ventilation operations. During a first stage cooling operation using only one refrigerant circuit and having a low cooling demand, the request for humidity control activates the hot gas reheat circuit for dehumidification and activates a second refrigerant circuit to provide cooling capacity. During a second stage cooling operation using two or more refrigerant circuit and having a high cooling demand, the request for humidity control is suspended and is initiated only upon the completion of the second stage cooling demand.

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30. A refrigeration circuit for use in an HVAC system comprising:

a cooling circuit having a high-pressure side and a low-pressure side comprising a compressor, a condenser and an evaporator, the cooling circuit capable of circulating refrigerant,

a reheat circuit comprising a reheat coil, the reheat circuit in selective fluid communication with the cooling circuit,

a first means for controlling flow of refrigerant, the first means selectively providing flow of refrigerant from the compressor to one of the reheat circuit and the cooling circuit, and

a second means for controlling flow of refrigerant, the second means selectively providing flow of refrigerant from the reheat circuit to the cooling circuit,

wherein the second means provides flow of refrigerant from the reheat circuit to the high-pressure side of the cooling circuit when the first means provides flow to the reheat circuit, and the second means providing flow of refrigerant from the reheat circuit to the low-pressure-side of the cooling circuit when the first means does not provide flow to the reheat circuit.

31. The refrigeration circuit of claim 30, wherein:

the first means is in fluid communication with the high-pressure side of the cooling loop and is switchable between a first position in which the refrigerant from the high pressure side of the cooling loop flows through the reheat circuit and a second position in which the refrigerant is blocked from entering the reheat circuit;

the second means being configurable to a first position in which refrigerant flows from the reheat circuit to the high-pressure side of the cooling loop and a second position in which the refrigerant flows from the reheat circuit to the low-pressure side of the cooling loop;

a reheat coil configured and disposed to receive refrigerant from the first means and to provide refrigerant to the second means, the reheat coil being configured to exchange heat from the refrigerant flowing through the coil from the first means to air flowing across the coil, the reheat coil in fluid communication with an evaporator in the cooling loop so as to provide refrigerant to the evaporator when the means for controlling is in the first position; and

wherein refrigerant flows from the reheat coil to the low-pressure side of the cooling loop in response to the first means being in the second position and the second means being in the first position.

32. The refrigeration circuit of claim 31, wherein:

the compressor includes a high-pressure discharge end and a low-pressure suction end,

the first means is a first valve arrangement, the first valve arrangement configured and disposed to provide flow of refrigerant to the reheat circuit in a first position and block flow of refrigerant to the reheat circuit in a second position, and

the second means is a second valve arrangement, the second valve arrangement configured and disposed to selectively provide flow of refrigerant from the reheat circuit,

the second valve arrangement flowing refrigerant from the reheat circuit to the evaporator when the first valve arrangement is in the first position, and

the second valve arrangement flowing refrigerant from the reheat circuit to the suction end of the compressor when the first valve arrangement is in the second position.

33. The refrigeration circuit of claim 32, wherein refrigerant flowing from the reheat circuit when the first valve arrangement is in the second position is refrigerant remaining in the reheat circuit when the first valve arrangement blocks flow to the reheat circuit.

34. The refrigeration circuit of claim 32, wherein the first valve arrangement includes one or more solenoid valves.

35. The refrigeration circuit of claim 32, wherein the second valve arrangement includes one or more solenoid valves.

36. The refrigeration circuit of claim 30, wherein the reheat coil is positioned adjacent to the evaporator wherein cooled, dehumidified air flowing across the evaporator is heated prior to entering an interior space.

37. A system for providing humidity control and cooling for an interior space of a building, comprising:

a refrigeration circuit comprising a cooling circuit having a high-pressure side and a low-pressure side comprising a compressor, a condenser and an evaporator, the cooling circuit capable of circulating refrigerant, and a reheat circuit comprising a reheat coil, the reheat circuit in selective fluid communication with the cooling circuit;

at least one sensor to monitor at least one condition indicative of parameters in the interior space of the building;

a first means for controlling flow of refrigerant, the first means selectively providing flow of refrigerant from the compressor to one of the reheat circuit and the cooling circuit, and

a second means for controlling flow of refrigerant, the second means selectively providing flow of refrigerant from the reheat circuit to the cooling circuit,

the second means providing flow of refrigerant from the reheat circuit to the high-pressure side of the cooling circuit when the first means provides flow to the reheat circuit, and the second means providing flow of refrigerant from the reheat circuit to the low-pressure-side of the cooling circuit when the first valve arrangement is in the second position, and

wherein the reheat coil is positioned between the interior space of the building and the evaporator to heat air to a preselected temperature after it passes across the evaporator;

a blower to assist the delivery of air to the interior space, and;

a controller in communication with the first means, the second means and at least one sensor to selectively configure the first means and second means in response to a signal from the at least one sensor.

38. The system of claim 37, wherein:

the compressor includes a high-pressure discharge end and a low-pressure suction end,

the first means is a first valve arrangement, the controller configuring the first valve arrangement to provide flow of refrigerant to the reheat circuit in a first position and block flow of refrigerant to the reheat circuit in a second position in response to the signal from the at least one sensor, and

the second means is a second valve arrangement, the second valve arrangement configured and disposed to selectively provide flow refrigerant from the reheat circuit,

the controller configuring the second valve arrangement to flow refrigerant from the reheat circuit to the evaporator when the first valve arrangement is in the first position, and

the controller configuring the second valve arrangement to flow refrigerant from the reheat circuit to the suction end of the compressor when the first valve arrangement is in the second position.

39. The system of claim 38 wherein the first valve arrangement includes one or more solenoid valves.

40. The system of claim 38 wherein the second valve arrangement includes one or more solenoid valves.

41. The system of claim 38 wherein the at least one sensor includes a temperature measuring device for monitoring the temperature of the interior space.

42. The system of claim 38 wherein the at least one sensor includes a humidity measuring device for monitoring the humidity of the interior space.

43. The system of claim 38 wherein the at least one sensor monitors an operating condition of the operation of the refrigeration circuit indicative of parameters in the interior space of the building.

44. The system of claim 38 wherein the at least one sensor includes a temperature measuring device for monitoring the outside temperature.

45. The system of claim 38 wherein the at least one sensor includes a humidity measuring device for monitoring the outside humidity.

46. The system of claim 38 further including a second refrigeration circuit for providing additional cooling to the interior space, the second refrigeration circuit including a second compressor, a second condenser, and a second evaporator.

47. A method of providing conditioned air to an interior space of a building, the method comprising the steps of:

providing a refrigeration circuit comprising a cooling circuit having a high-pressure side and a low-pressure side comprising a compressor, a condenser and an evaporator, and a reheat circuit comprising a reheat coil, the reheat circuit in selective fluid communication with the cooling circuit,

circulating refrigerant through the cooling loop to provide conditioned air to an interior space of a building, and wherein the reheat coil heats air for the interior space after it passes over the evaporator when the reheat circuit is activated,

wherein the reheat circuit further includes means for removing refrigerant from the reheat coil to low-pressure side of the cooling loop when the reheat circuit is inactivated and wherein the reheat coil is disposed adjacent to the evaporator;

providing at least one sensor indicative of at least one condition in the interior space of the building, the at least one sensor providing at least one signal indicative of the at least one condition in the interior building space;

providing a controller to receive the at least one signal indicative of the at least one condition in the interior building space and to control the operation of the refrigerant circuit in response to the at least one received signal, wherein control of the refrigerant circuit further includes controlling the refrigerant flow to the reheat circuit in response to the at least one received signal so that one of a conditioned air selected from the group consisting of dehumidified air and cooled air can be provided to the interior building space;

enabling the refrigerant circuit to provide cooling of air for the interior space in response to a signal from the controller; and

dehumidifying air for an interior space in response to a signal from the controller by activating the reheat circuit to provide refrigerant from the first compressor to the reheat coil heat the air to a first preselected temperature prior to delivering the air to the interior space.

48. The method of claim 47 further including a step of providing at least one sensor to monitor the temperature of air passing over the evaporator and provide a signal to the controller indicative of the temperature, and providing a heater to heat to a preselected temperature air passing into the interior space from evaporator in response to a signal from the controller.

49. The method of claim 47, wherein the means for removing refrigerant from the reheat coil to low-pressure side of the cooling loop when the reheat circuit is inactivated further includes a valve selectively providing fluid communication between the coil and the low-pressure side of the cooling loop.