Variable air volume air conditioning system

• US 4,086,781 A
• Filed: 04/23/1976
• Issued: 05/02/1978
• Est. Priority Date: 04/23/1976
• Status: Expired due to Term

• Current Assignee: ITT Corporation (ITT, Inc.)
• Original Assignee: International Telephone & Telegraph Corp. (ITT, Inc.)
• Inventors: Weigle, George L., Brody, Herbert M.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US05/679,592
• Time in Patent Office: 739 Days
• Field of Search: 417/279, 165/16, 165/15, 445/148, 236/13, 236/49, 98/1.5, 62/180
• US Class Current: 62/180
• CPC Class Codes: F24F 11/74 for controlling air flow rate or air velocity
• CPC Class Codes: F24F 3/0442 with volume control at a constant temperature

Abstract

A variable air volume air conditioning system is provided with thermostat controlled variable air volume terminal boxes for controlling the volume of constant temperature conditioned air provided to each space to be conditioned. The conditioned air is delivered through a short pressure recovery duct to a trunk duct by a centrifugal fan having forward curved blades. The trunk duct pressure is maintained substantially constant by control vanes disposed at the recovery duct outlet, said control vanes being responsive to an increase in duct pressure to close the duct outlet and unload the fan, thereby reducing the energy consumed by the fan. Economizer operation is provided by the use of return air dampers and outside air dampers controlled in response to outside air temperature and air supply duct temperature to mix outside air and return air to reduce the amount of mechanical refrigeration required. A power air return means is provided for returning air to the system from the spaces that are conditioned and for controlling the amount of return air in accordance with the volume of air delivered to the conditioned spaces.

Claims

1. A variable air volume air conditioning system, comprising:

means for providing air at a predetermined temperature;

a forward curved fan for delivering said air, said fan having an inlet for receiving the air from the last mentioned means and an outlet;

a pressure recovery duct having one end connected to the outlet of said fan;

outlet control vane means disposed at a second end of said pressure recovery duct for controlling the volume of air flow from said fan in response to air pressure downstream from the outlet control vane means;

duct means for directing the air from the outlet control vane means to a space to be conditioned; and

air volume control means for controlling the volume of air supplied to a space to be conditioned in accordance with the cooling requirements of said space, whereby the air pressure in the duct means is maintained substantially constant by the outlet control vane means.

2. A system as described in claim 1, additionally comprising refrigeration means for cooling said air.

3. A system as described in claim 2, additionally comprising means for controlling the air temperature to a predetermined set point.

4. A system as described in claim 1, having a plurality of forward curved fans having outlets connected to the pressure recovery duct.

5. A system as described in claim 4, wherein said fans are connected to a common drive shaft.

6. A system as described in claim 1, wherein the outlet control vane means comprises a plurality of oppositely disposed outlet vanes for controlling the volume of air delivered by the fan.

7. A system as described in claim 3, wherein the outlet control vane means includes an output for providing a signal corresponding to the position of the outlet control vane means and the means for controlling the air temperature comprises a dual set point temperature controller, the system additionally comprising means connecting the output of the outlet control vane means to the means for controlling air temperature, said means for controlling air temperature being responsive to the signal received from the outlet control vane means for changing the temperature set point, whereby the temperature set point of the means for controlling the air temperature is changed in response to the volume of air flow from the fan.

8. A variable air volume air conditioning system, comprising:

means for providing air at a predetermined temperature;

a forward curved fan having an inlet for receiving said air and an outlet for delivering said air;

a pressure recovery duct having an inlet connected to the outlet of said fan;

outlet control vane means connected to an outlet of the pressure recovery duct for controlling the volume of air delivered by said fan in response to the cooling requirements of a space to be conditioned; and

duct means for directing the air to the space to be conditioned.

9. A variable air volume air conditioning system as described in claim 8, additionally comprising:

means associated with the outlet control vane means for providing a signal corresponding to the position of the outlet control means; and

means for controlling the first mentioned means in response to the signal from the outlet control vane means to maintain a first predetermined air temperature when a first volume of air or more is delivered to said space and to maintain a second predetermined air temperature when less than the first volume of air is delivered to said space.