Heating, ventilation, and air-conditioning system with reheat
A heating, ventilation, and air-conditioning (“HVAC”) system for use with a refrigerant. The HVAC system may include a compressor, an outdoor heat exchanger positioned downstream of the compressor, a first variable expansion device positioned downstream of the outdoor heat exchanger, an indoor heat exchanger positioned downstream of the first variable expansion device and upstream of the compressor and including a reheat portion and a main portion, a second variable expansion device positioned downstream of the reheat portion of the indoor heat exchanger and upstream of the main portion of the indoor heat exchanger, a first control valve operable to selectively control the flow of the refrigerant through the reheat portion of the indoor heat exchanger and the main portion of the indoor heat exchanger, and a control system programmed to selectively operate the HVAC system in one of a first cooling mode, a second cooling mode, and a dehumidification mode.
1 . A heating, ventilation, and air-conditioning (“HVAC”) system for use with a refrigerant, the HVAC system comprising:
a compressor operable to compress the refrigerant;
an outdoor heat exchanger positioned downstream of the compressor and configured to condense the refrigerant;
a first variable expansion device positioned downstream of the outdoor heat exchanger and operable to change a pressure of the refrigerant flowing therethrough;
a single indoor heat exchanger positioned downstream of the first variable expansion device and upstream of the compressor, comprising a reheat portion downstream of the first variable expansion device and a main portion, and configured to vaporize low-pressure refrigerant;
a second variable expansion device positioned downstream of the reheat portion of the indoor heat exchanger and upstream of the main portion of the indoor heat exchanger, the second variable expansion device operable to change a pressure of the refrigerant flowing therethrough;
an indoor control valve operable to selectively control the flow of the refrigerant through the reheat portion of the indoor heat exchanger and the main portion of the indoor heat exchanger; and
a control system in electronic communication with the first variable expansion device, the second variable expansion device, and the indoor control valve, the control system comprising a processor programmed to adjust the change in pressure due to the first variable expansion device, adjust the change in pressure due to the second variable expansion device, and operate the indoor control valve to selectively operate the HVAC system between a first cooling mode wherein no refrigerant flows through the reheat portion of the indoor heat exchanger, a second cooling mode wherein the pressure of the refrigerant flowing through the first variable expansion device is decreased and at least a portion of the decreased pressure refrigerant flows through the reheat portion of the indoor heat exchanger where the refrigerant absorbs heat so as to provide additional cooling compared to the first cooling mode, and a dehumidification mode.
2 . The HVAC system of claim 1 , wherein the reheat portion is configured to vaporize the refrigerant expanded in the first variable expansion device and the main portion is configured to vaporize refrigerant expanded in at least one of the first variable expansion device or the second variable expansion device.
3 . The HVAC system of claim 1 , wherein the control system is further programmed to adjust the change in pressure due to the first variable expansion device, adjust the change in pressure due to the second variable expansion device, and operate the indoor control valve based on at least one of the mode of the HVAC system or a load on the HVAC system.
4 . The HVAC system of claim 1 , wherein the control system further comprises an input device and the control system is further programmed to adjust the change in pressure due to the first variable expansion device, adjust the change in pressure due to the second variable expansion device, and operate the indoor control valve based on a user input from the input device.
5 . The HVAC system of claim 1 , further comprising an outdoor control valve positioned downstream of the compressor and upstream of the outdoor heat exchanger, the outdoor control valve operable to selectively control flow of the refrigerant through the outdoor heat exchanger and flow of the refrigerant that bypasses the outdoor heat exchanger.
6 . The HVAC system of claim 3 , wherein the control system is further programmed to operate the indoor control valve to force refrigerant to bypass the reheat portion, to force refrigerant to flow through the reheat portion, or to allow a first portion of refrigerant to flow through the reheat portion and a second portion of refrigerant to bypass the reheat portion.
7 . The HVAC system of claim 4 , wherein the control system is further programmed to operate the indoor control valve to force refrigerant to bypass the reheat portion, to force refrigerant to flow through the reheat portion, or to allow a first portion of refrigerant to flow through the reheat portion and a second portion of refrigerant to bypass the reheat portion.
8 . The HVAC system of claim 5 , wherein the control system is further programmed to adjust the change in pressure due to the first variable expansion device, adjust the change in pressure due to the second variable expansion device, operate the indoor control valve, and operate the outdoor control valve based on at least one of the mode of the HVAC system or a load on the HVAC system.
9 . The HVAC system of claim 5 , wherein the control system further comprises an input device and the control system is further programmed to adjust the change in pressure due to the first variable expansion device, adjust the change in pressure due to the second variable expansion device, operate the indoor control valve, and operate the outdoor control valve based on a user input from the input device.
10 . The HVAC system of claim 8 , wherein the control system is in electronic communication with the outdoor control valve and further programmed to operate the outdoor control valve to force refrigerant to bypass the outdoor heat exchanger, to force refrigerant to flow through the outdoor heat exchanger, or to allow a first portion of refrigerant to flow through the outdoor heat exchanger and a second portion of refrigerant to bypass the outdoor heat exchanger.
11 . The HVAC system of claim 9 , wherein the control system is in electronic communication with the outdoor control valve and further programmed to operate the outdoor control valve to force refrigerant to bypass the outdoor heat exchanger, to force refrigerant to flow through the outdoor heat exchanger, or to allow a first portion of refrigerant to flow through the outdoor heat exchanger and a second portion of refrigerant to bypass the outdoor heat exchanger.
12 . An HVAC system for use with a refrigerant, the HVAC system comprising:
a compressor operable to compress the refrigerant;
an indoor heat exchanger positioned downstream of the compressor, comprising a reheat portion and a main portion, and configured to condense the refrigerant;
an expansion device positioned downstream of the indoor heat exchanger and operable to reduce a pressure of the refrigerant flowing therethrough into a low-pressure refrigerant;
outdoor heat exchanger positioned downstream of the expansion device and upstream of the compressor and configured to vaporize the low-pressure refrigerant;
an indoor control valve operable to selectively control only a selected portion of the flow of the refrigerant through the reheat portion of the indoor heat exchanger; and
a control system in electronic communication with the indoor control valve, the control system comprising a processor programmed to operate the indoor control valve and the indoor control valve to selectively operate the HVAC system between one of a first heating mode wherein refrigerant flows through the main portion and no refrigerant flows through the reheat portion and a second heating mode wherein refrigerant flows through the main portion and only the selected portion of the refrigerant flows through the reheat portion, unexpanded, to provide additional heating compared to the first heating mode.
13 . The HVAC system of claim 12 , wherein the control system is further programmed to operate the indoor control valve based on at least one of the mode of the HVAC system or a load on the HVAC system.
14 . The HVAC system of claim 12 , wherein the control system further comprises an input device and the control system is further programmed to operate the indoor control valve based on a user input from the input device.
15 . The HVAC system of claim 13 , wherein the control system is programmed to operate the indoor control valve between a first position that forces all of the flow of the refrigerant to bypass the reheat portion, a second position that forces all of the flow of the refrigerant to flow through the reheat portion, and a position between the first position and second position to allow only a portion of the flow of the refrigerant to flow through the reheat portion.
16 . The HVAC system of claim 14 , wherein the control system is programmed to operate the indoor control valve between a first position that forces refrigerant to bypass the reheat portion, a second position that forces refrigerant to flow through the reheat portion, and a position between the first position and second position to allow a first portion of refrigerant to flow through the reheat portion and a second portion of refrigerant to bypass the reheat portion.
17 . A method of operating an HVAC system, the method comprising:
compressing a low-pressure vapor refrigerant with a compressor into a high-pressure vapor refrigerant; then
condensing at least a portion of the high-pressure vapor refrigerant into a high-pressure liquid refrigerant with an outdoor heat exchanger; then
in a first cooling mode:
flowing the refrigerant through a first expansion device without adjusting the pressure of the refrigerant; then
operating an indoor control valve so that no refrigerant flows through a reheat portion of an indoor heat exchanger; then
expanding the refrigerant to a low-pressure liquid refrigerant with a second expansion device; and then
vaporizing the low-pressure liquid refrigerant from the second expansion device with a main portion of the indoor heat exchanger;
in a second cooling mode:
expanding the refrigerant to a low-pressure liquid refrigerant with the first expansion device; then
operating the indoor control valve to flow an amount of the refrigerant through the reheat portion of the indoor heat exchanger; then
flowing the refrigerant through a second expansion device without adjusting the pressure of the refrigerant; and then
vaporizing the low-pressure liquid refrigerant from the second expansion device with a main portion of the indoor heat exchanger; and
in a dehumidification mode:
flowing the refrigerant through the first expansion device without adjusting the pressure of the refrigerant; then
operating the indoor control valve to flow a first selected amount of the refrigerant through the reheat portion of the indoor heat exchanger and the remaining amount of the refrigerant does not flow through the reheat portion; then
expanding the refrigerant to a low-pressure liquid refrigerant with the second expansion device; and then
vaporizing the low-pressure liquid refrigerant from the first expansion device with a main portion of the indoor heat exchanger.
18 . The method of claim 17 , further comprising:
flowing a first portion of air across the main portion of the indoor heat exchanger to cool and reduce humidity in the first portion of the air while flowing a second portion of air over the reheat portion of the indoor heat exchanger to heat the second portion of the air; and then
combining the first portion of the air and the second portion of the air such that the air flows across the indoor heat exchanger without significantly changing a temperature of the air.
19 . The method of claim 17 , further comprising:
flowing air across the main portion of the indoor heat exchanger to cool the air and reduce humidity in the air; and then
flowing the air across the reheat portion of the indoor heat exchanger to heat the air such that the air flows across the indoor heat exchanger without significantly changing a temperature of the air.
20 . The method of claim 17 , wherein operating the indoor control valve comprises operating the indoor control valve to flow all of the refrigerant through the reheat portion of the indoor heat exchanger.
21 . The method of claim 17 , further comprising adjusting the first expansion device to expand the refrigerant to an intermediate-pressure liquid refrigerant at a higher pressure than the low-pressure liquid refrigerant, wherein:
operating the indoor control valve comprises operating the indoor control valve to flow at least a portion of the intermediate-pressure liquid refrigerant through the reheat portion of the indoor heat exchanger; and
expanding the refrigerant with the second expansion device comprises expanding the intermediate-pressure liquid refrigerant to the low-pressure liquid refrigerant.
22 . The method of claim 17 , wherein the amount of the refrigerant flowed through the reheat portion of the indoor heat exchanger is based on a load on the HVAC system.
23 . The method of claim 17 , wherein the amount of the refrigerant flowed through the reheat portion of the indoor heat exchanger is based on a user input into an input device.
24 . The method of claim 17 , further comprising:
operating an outdoor control valve to allow at least a portion of the high-pressure vapor refrigerant to bypass the outdoor heat exchanger; and then
condensing the portion of the high-pressure vapor refrigerant bypassing the outdoor heat exchanger into the high-pressure liquid refrigerant with the reheat portion of the indoor heat exchanger,
wherein operating the indoor control valve comprises operating the indoor control valve to flow all of the refrigerant through the reheat portion of the indoor heat exchanger.