Air conditioning system having improved dehumidification capabilities

• US 4,003,729 A
• Filed: 11/17/1975
• Issued: 01/18/1977
• Est. Priority Date: 11/17/1975
• Status: Expired due to Term

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: McGrath, William L.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US05/632,330
• Time in Patent Office: 428 Days
• Field of Search: 62/93, 62/176, 62/186, 62/208, 62/180, 62/216
• US Class Current: 62/93
• CPC Class Codes: F24F 3/1405 in which the humidity of the air is exclusively affected by contact with the evaporator of a closed-circuit cooling system or heat pump circuit
• CPC Class Codes: F25B 49/00 Arrangement or mounting of control or safety devices
• CPC Class Codes: G05D 23/1931 to control the temperature of one space
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

An air conditioning system includes a mechanical refrigeration unit having a control to vary the dehumidifying capabilities of the system. The speed of the fan provided to route air in heat transfer relationship with the evaporator of the refrigeration unit is varied to vary the flow rate of the air across the evaporator. When it is desired to increase the dehumidifying capabilities of the system, the flow rate of the air is reduced. The temperature of the evaporator is monitored to decrease the flow rate of the air thereacross as the temperature of the refrigerant flowing through the coil increases and to increase the flow rate of the air across the evaporator as the refrigerant temperature decreases, to thereby maintain the refrigerant temperature in the evaporator at a predetermined level.

Claims

1. In an air conditioning system including a mechanical refrigeration unit having a fan to route air in heat transfer relationship with the evaporator and actuating means to drive said fan, a control system to increase the dehumidifying capabilities of said system comprising:

temperature responsive means to sense the temperature level of the refrigerant passing through the evaporator coil;

means to generate a control signal in response to said sensed refrigerant temperature including means to vary the magnitude of said signal as the sensed refrigerant temperature varies;

means to supply said variable magnitude control signal to said fan actuating means to vary the speed of said actuating means and thus the speed of said fan, whereby the speed of said fan is decreased as the sensed refrigerant temperature increases to decrease the flow rate of the air across the evaporator, and the speed of the fan is increased as the sensed refrigerant temperature decreases to increase the flow rate of air across the evaporator to maintain a substantially constant refrigerant temperature;

means to sense the temperature level of the air in the space being served by said air conditioning system;

means to generate a second control signal in response to said sensed air temperature including means to vary the magnitude of said second signal as the sensed air temperature varies;

means to supply said second variable magnitude control signal to said fan actuating means to vary the speed of said fan; and

monitoring means to determine the magnitude of said second control signal including means to discontinue operation of said refrigeration unit if the magnitude of said second control signal is indicative of the air temperature having fallen below a predetermined value.

2. In an air conditioning system including a mechanical refrigeration unit including a fan to route air in heat transfer relationship with the evaporator of said refrigeration unit;

and actuating means to drive said fan, a control system to increase the dehumidifying capabilities of said system comprising;

temperature responsive variable resistance means disposed in heat transfer relation with the evaporator of the refrigeration unit to monitor the temperature level of the refrigerant flowing therethrough;

means to generate a control signal in response to said monitored refrigerant temperature, including means to vary the magnitude of said signal in response to variations in the monitored refrigerant temperature;

means to supply said variable magnitude control signal to said fan actuating means to vary the speed of said fan, whereby the speed of the fan is decreased as the monitored refrigerant temperature increases to decrease the flow rate of the air across the evaporator, and the speed of the fan is increased as the monitored temperature decreases to increase the flow rate of the air across the evaporator, the flow rate of the air being maintained at a sufficient level to prevent said refrigerant from decreasing below a predetermined temperature;

second temperature responsive variable resistance means to sense the temperature level of the air in the space being served by said air conditioning system;

means to generate a second control signal in response to said sensed air temperature, including means to vary the magnitude of said second signal as the sensed air temperature varies;

means to supply said second control signal to said fan actuating means to vary th speed of said fan; and

monitoring means to determine the magnitude of said second control signal including means to discontinue operation of said refrigeration unit if the magnitude of said second control signal is indicative of the air temperature having decreased below a predetermined value.

3. In an air conditioning system in accordance with claim 2 further including:

second temperature responsive variable resistance means to sense the temperature level of the air in the space being served by said air conditioning system;

means to generate a second control signal in response to said sensed air temperature, including means to vary the magnitude of said second signal as the sensed air temperature varies;

means to supply said second control signal to said fan actuating means to vary the speed of said fan; and

monitoring means to determine the magnitude of said second control signal including means to discontinue operation of said refrigeration unit if the magnitude of said second control signal is indicative of the air temperature having decreased below a predetermined value.

4. A method of operating an air conditioning system, including a mechanical refrigeration unit, to increase the dehumidifying capabilities of said system comprising the steps of:

propelling air to be conditioned in heat transfer relation with refrigerant flowing through the evaporator of the refrigeration unit, with the air rejecting heat to the refrigerant;

monitoring the temperature of the refrigerant flowing through the evaporator;

generating a control signal, with the magnitude thereof varying as the monitored refrigerant temperature varies;

supplying the variable magnitude control signal to the air propelling device to vary the speed of the device whereby the speed of the device is increased to increase the flow rate of the air across the evaporator as the refrigerant temperature decreases below a predetermined level, and the speed of the device is decreased to decrease the flow rate of the air across the evaporator as the refrigerant temperature increases above a predetermined level;

sensing the temperature of the air in the space being conditioned;

generating a second control signal in response to the sensed air temperature, with the magnitude of the signal varying in response to changes in sensed air temperatures;

supplying a second control signal to the air routing device to vary the speed of the device to vary the rate of flow of air in heat transfer relation with the evaporator; and

monitoring the second control signal to determine the magnitude thereof to discontinue operation of the air conditioning system if the magnitude of the second control signal is indicative of the air temperature having decreased below a predetermined value.

5. A method in accordance with claim 4 further comprising the steps of:

sensing the temperature of the air in the space being conditioned;

generating a second control signal in response to the sensed air temperature, with the magnitude of the signal varying in response to changes in sensed air temperature;

supplying the second control signal to the air routing device to vary the speed of the device to vary the rate of flow of air in heat transfer relation with the evaporator; and

monitoring the second control signal to determine the magnitude thereof to discontinue operation of the air conditioning system if the magnitude of the second control signal is indicative of the air temperature having decreased below a predetermined value.

6. In an air conditioning system including a mechanical refrigeration unit having a fan to route air in heat transfer relationship with the evaporator of said refrigerator unit to provide relatively cold air for a space being conditioned, and actuating means to drive said fan, the improvement of a control system comprising:

first temperature responsive means to sense the temperature of the refrigerant passing through the evaporator coil;

means to generate a first control signal in response to said sensed refrigerant temperature including means to vary the magnitude of said signal as the sensed refrigerant temperature varies;

second temperature responsive means to sense the temperature of the air in the space being conditioned;

means to generate a second control signal in response to said sensed air temperature, including means to vary the magnitude of said signal as the sensed air temperature varies; and

comparative means to receive said first and second control signals and to select the control signal of the larger magnitude to supply said larger magnitude signal to said fan actuating means to vary the speed of said actuating means and thus the speed of said fan in response to the magnitude of said selected signal.

7. In an air conditioning system in accordance with claim 6 wherein the magnitude of said first signal increases as the temperature of the refrigerant decreases below a predetermined level.

8. In an air conditioning system in accordance with claim 7 wherein the magnitude of said second signal increases as the temperature of the air increases above a predetermined level.

9. In an air conditioning system in accordance with claim 6 wherein the magnitude of said second signal increases as the temperature of the air increases above a predetermined level.

10. A method of operating an air conditioning system including a mechanical refrigeration unit comprising the steps of:

routing air to be conditioned in heat transfer relation with the refrigerant flowing through the evaporator of the refrigeration unit, with the air rejecting heat to the refrigerant;

sensing the temperature of the air in a space being served by the system;

selectively increasing and decreasing the flow rate of air over the evaporator as the temperature of the sensed air respectively increases above or decreases below a first predetermined level;

sensing the temperature of the refrigerant flowing through the evaporator; and

increasing the flow rate of the air over the evaporator irrespective of the sensed air temperature if the temperature of the refrigerant decreases below a predetermined value.

11. A method in accordance with claim 10 wherein the compressor of the refrigeration unit is deenergized if the temperature of the sensed air decreases below a second predetermined level, the second predetermined level being below the first predetermined level.