Air-conditioning system with variable subcooling
A dedicated outside air-conditioning system (DOAS) that may automatically generate variable subcooling refrigerant delivered to the evaporator; and modulate hot discharge gas to reduce the relative humidity of the discharge air from the DOAS. The DOAS may include fluid control valves configured to regulate delivery of the refrigerant in order to seamlessly flex between maximum latent capacity (minimum discharge dewpoint) and maximum sensible capacity (minimum leaving air discharge dry bulb temperature) to match load and/or ventilation air requirements.
1. A dedicated outdoor air-conditioning system comprising:
an evaporator, a condenser, a compressor, a refrigerant receiver, and a control system for circulating refrigerant through the condenser and the evaporator, the evaporator having a refrigerant inlet, and the compressor having a refrigerant outlet;
an air handler that moves an air flow over the evaporator which conditions the air flow to a desired temperature and humidity prior to entering a conditioned room;
a heat exchanger coil that subcools refrigerant from a subcooling heat exchanger to the refrigerant inlet of the evaporator and wherein the subcooling heat exchanger reheats the airflow downstream of the evaporator to lower a relative humidity of the air flow;
the control system including a modulating valve for modulating a refrigerant flow through the subcooling heat exchanger, and an actuator connected to the modulating valve for moving the valve in response to a sensed air flow temperature or humidity or a sensed refrigerant temperature, humidity, or pressure,
wherein the modulating valve modulates the reception of refrigerant from the compressor and receiver and directs the flow of refrigerant toward the evaporator.
2. The dedicated outdoor air conditioning system of claim 1 , wherein the control system further comprises a first sensor for reading the temperature, humidity, or pressure of the air flow upstream of the evaporator or downstream of the subcooling heat exchanger and a second sensor for reading the temperature, humidity, or pressure of the refrigerant as it travels through the dedicated outdoor air conditioning system.
3. The dedicated outdoor air conditioning system of claim 1 , wherein a first valve and a second valve are located after the modulating valve and prior to the evaporator;
the first valve modulating flow of refrigerant along a first path and the second valve modulating flow of refrigerant along a second path;
the first path flowing to the subcooling heat exchanger prior to entering the evaporator; and
the second path flowing directly to the evaporator.
4. The dedicated outdoor air conditioning system of claim 3 further comprising:
a hot vapor heat exchanger, connected with the refrigerant outlet of the compressor and positioned in the air flow downstream from the evaporator, for further reheating the air flow from the evaporator to further lower the relative humidity of the air flow,
wherein the control system further comprises:
a second modulating valve receiving flow of refrigerant from the compressor and modulating the flow of refrigerant between a third and a fourth path;
the third path flowing toward a second heat exchanger prior to entering the condenser; and
the fourth path flowing directly toward the condenser.
5. The dedicated outdoor air conditioning system of claim 4 , wherein the second heat exchanger is a second hot vapor heat exchanger, the second hot vapor heat exchanger positioned in the air flow downstream from said subcooling heat exchanger.
6. The dedicated outdoor air conditioning system of claim 1 , further comprising a reversing valve to reverse the flow of refrigerant.
7. A method of operating a dedicated outdoor air-conditioning system apparatus comprising an evaporator, a condenser, a compressor, a refrigerant receiver, and refrigerant through the condenser and the evaporator, said method comprising the steps of:
operating a control system including a modulating valve to modulate the reception of refrigerant from the compressor and receiver and directing the flow of refrigerant toward the evaporator, and an actuator connected in the modulating valve for moving the valve in response to a sensed air flow temperature or humidity or a sensed refrigerant temperature, humidity, or pressure;
generating an air flow over the evaporator to cool the air flow;
subcooling refrigerant being delivered to the evaporator;
reheating the air flow downstream from the evaporator to further lower the relative humidity of the air flow; and
modulating the flow of refrigerant via the control system.
8. The method of claim 7 , the control system further comprising a first sensor for reading the temperature, humidity, or pressure of the air flow upstream or downstream of the evaporator and a second sensor for reading the temperature, humidity, or pressure of the refrigerant as it travels through the dedicated air conditioning system.
9. The method of claim 7 , wherein the step of modulating the flow of refrigerant includes:
modulating the reception of refrigerant to the modulating valve from the compressor and the receiver responsive to a sensed condition and directing the flow of refrigerant to the evaporator through a first valve and second valve,
wherein the first valve modules flow of a refrigerant to a first path responsive to a sensed condition, the first path including a sub cooling heat exchanger and an evaporator, and
wherein the second valve modulates flow of refrigerant to a second path responsive to a sensed condition, the second path including an evaporator.
10. The method of claim 7 , wherein the step of modulating the flow of refrigerant includes:
modulating the flow of refrigerant via the modulating valve, wherein the modulating valve receives refrigerant from the receiver and modulating the flow of refrigerant to the evaporator through a first path responsive to a sensed condition, the first path including a subcooling heat exchanger and evaporator, and a second path responsive to a second condition, the second path including an evaporator; and
modulating the flow of refrigerant via a second modulating valve, wherein the second modulating valve receives refrigerant from the compressor and modulating the flow of refrigerant through a third path responsive to a sensed condition, the third path including a second heat exchanger and condenser, and a fourth path responsive to a sensed condition, the fourth path including the condenser.