Calculation of flow in an air system

Patent metadata

Field	Value
Publication number	US-9636970-B2
Application number	US-201414246409-A
Country	US
Kind code	B2
Filing date	Apr 7, 2014
Priority date	Apr 15, 2013
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

A method is provided for determining an air flow in a vehicle air conditioning system that comprises an inlet; a plurality of outlets; at least one air duct for guiding air from the inlet to the outlets, each air duct being characterized by a predetermined flow resistance coefficient; at least one flap characterized by a flow resistance based on a degree of opening of the flap; and a fan for creating an air flow from the inlet to an outlet. The method comprises determining a total equivalent flow resistance between a predetermined location in the system and an interior of the vehicle, wherein flow resistances are treated as resistances in an electric circuit, and a total equivalent flow resistance is determined. Treating a pressure drop as equivalent with a voltage drop, the air flow can be determined, as the pressure is equal to the resistance times the flow squared.

First claim

What is claimed is:

1. A method for determining an air flow in a vehicle air conditioning system, wherein the system comprises at least one inlet; a plurality of outlets; at least one air duct for guiding air from the at least one inlet to the plurality of outlets, each air duct having a predetermined flow resistance coefficient; at least one flap having a flow resistance based on a degree of opening of the at least one flap; and a fan for creating an air flow from the at least one inlet to at least one of the plurality of outlets; the method comprising:
determining a total equivalent flow resistance k tot between a predetermined location in the system and an interior of the vehicle, wherein flow resistances arranged in series are added to each other and wherein an equivalent flow resistance k 0 representing a first flow resistance k 1 and a second flow resistance k 2 arranged in parallel is determined as:

k
0

=

k
1

⁢

k
2

k
1

+

k
2

+

2
⁢

k
1

⁢

k
2

;

determining a pressure difference P between the predetermined location in the system and the interior of the vehicle; and
determining total air flow F into the interior of the vehicle as

F
=

P

k
tot

.

2. The method according to claim 1 further comprising determining an air flow from an outlet based on the total air flow and an equivalent flow resistance between the predetermined location and the outlet.

3. The method according to claim 1 wherein an air flow f 1 from a first duct having a first flow resistance k 1 , arranged in parallel with a second duct having a second flow resistance k 2 , is determined as

f
1

=

k
2

k
1

+

k
1

⁢

f
0

where f 0 is total inflow to the first and second ducts.

4. The method according to claim 1 wherein the pressure difference is determined as the difference between an absolute pressure measured in the interior of the vehicle and an absolute pressure measured at the predetermined location in the system.

5. The method according to claim 1 wherein pressure at a predetermined location of the system is determined based on a vehicle speed and fan speed.

6. The method according to claim 1 wherein the predetermined location is located between the fan and the at least one air duct.

7. The method according to claim 1 wherein a predetermined flow resistance for the at least one air duct and/or the at least one flap is adjusted based on a temperature.

8. The method according to claim 1 further comprising controlling fan speed and the degree of opening of the at least one flap such that a predetermined air flow is achieved through each of the plurality of outlets.

9. The method according to claim 1 further comprising controlling an actuator connected to one of the at least one flap for controlling a degree of opening of the one flap.

10. An air conditioning system for a vehicle, the system comprising:
at least one inlet;
a plurality of outlets;
at least one air duct configured to guide air from the at least one inlet to the plurality of outlets, each air duct having a predetermined flow resistance coefficient;
at least one flap having a flow resistance based on a degree of opening of the at least one flap;
a controllable fan for creating an air flow from the at least one inlet to at least one of the plurality of outlets; and
a control unit configured to:
determine a total equivalent flow resistance between a predetermined location in the system and an interior of the vehicle, wherein flow resistances arranged in series are added to each other and wherein an equivalent flow resistance k 0 representing a first flow resistance k 1 and a second flow resistance k 2 arranged in parallel is determined as:

k
0

=

k
1

⁢

k
2

k
1

+

k
2

+

2
⁢

k
1

⁢

k
2

;

determine a pressure difference between the predetermined location in the system and the interior of the vehicle; and
control total air flow into the interior of the vehicle by controlling the fan and the degree of opening of the at least one flap.

11. The air conditioning system according to claim 10 further comprising a recirculation flap arranged bet

Assignees

• Volvo Car Corp

Inventors

• Jange Jonas

Classifications

• G01F15/002

  for gases · CPC title

• G01F1/36

  the pressure or differential pressure being created by the use of flow constriction · CPC title

• G01F15/005

  Valves (valves in general F16K) · CPC title

• B60H1/00864 Primary

  Ventilators and damper doors · CPC title

• G01F1/34

  by measuring pressure or differential pressure · CPC title