FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION
(See Section 10; rule 13)


TITLE OF THE INVENTION
Test Rig For Air Flow Measurement Thorough Ducts Of Mobile Air Conditioning System
APPLICANTS
TATA MOTORS LIMITED, an Indian Company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

INVENTORS
Mr. Navdeep Singh and Mr. Shrikant Awate
Both are Indian Nationals of
TATA MOTORS LIMITED, an Indian Company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION The following specification describes invention


FIELD OF INVENTION
This invention relates to the designing of a test rig for measuring Air Flow through he ducts of an air conditioning system in an automobile. This rig particularly uses the nozzles to measure the air flow coming out of the ducts.
BACKGROUND OF INVENTION
HVAC System is used in the vehicles for comfort cooling or heating of the vehicle cabin for human beings. When providing such kind of conditioning system for vehicles it is very important to have desired air flow of conditioned air through the ducts of the HVAC system. Therefore, it is important to measure the total amount of air flowing through the HVAC duct system. Often this amount of air flow is measured several times for getting the optimized air flow through the HVAC duct system.
Conventionally, the total amount of air flowing from a duct system is measured individually at various grill outlet of duct system and added together to get the total amount of air flow from the duct system. Usually, individual air flow is measured using vane type anemometer, pencil anemometer or hot wire, anemometer. At each grill outlet air velocity is measured with anemometer and it is then multiplied by the cross sectional area of the grill outlet to obtain the volumetric air flow.
Conventional method is not accurate for measuring the air flow form the ducts. It involves the variations in the measurements. The present invention addresses the conventional problems and gives accurate results directly to user in volumetric air flow.
OBJECTS OF INVENTION
The main object of this invention is to provide an accurate system for measuring a

wide range of air flow through the HVAC duct system.
BRIEF DESCRIPTION OF INVENTION
Air Flow Rig is basically comprises of a flexible duct and a set of nozzles for measuring different air flows. This flexible duct canalizes all the air flow from the grill outlet to the chamber in which nozzle is fixed. A differential pressure sensor is mounted on the one end of this duct. The other end of the duct is fixed to a chamber where nozzle is placed. Beyond the nozzle a blower is fixed for sucking the air.
A differential pressure sensor is placed across the nozzle to measure the differential pressure across nozzle. Flexible duct is kept at the grill outlet and HVAC blower is switched on. Air flow coming out of the grill will generate some pressure. This pressure is measured by the pressure sensor at this end of flexible duct. External blower is in turn driven by the variable frequency drive to make this grill pressure zero.
With external blower running all the air flow from the duct is passed through the flexible duct to nozzle. This air flow creates a pressure difference across the nozzle while passing. This pressure difference along with the area of nozzle opening is used to calculate the volumetric air flow passing through the nozzle using flow equation for the nozzle. This air flow is the same as coming out of the grill outlet.
SUMMARY OF INVENTION
This invention relates to an Air Flow Rig for measuring volumetric air flow from the grill outlet of HVAC system comprising of a flexible duct having a differential pressure sensor fixed at one end, said and is connected to the grill outlet of the HVAC system for measurements while other end is connected to a chamber. Said chamber is consists of a nozzle and an externally driven blower. Said system is controlled with software and various inputs.

BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 shows the sectional view of front end of Air Flow Rig showing details of construction of rig in accordance with this invention.
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
Flexible Duct (2) of the rig in accordance with this invention basically fixed on the grill outlet (1) of vehicle HVAC system. Flexible Duct (2) is used to canalize the air flow from the grill outlet (1) to the chamber (3). A pressure sensor (13) fixed on the start point of flexible duct (2) measures the static pressure developed at grill outlet (1) when HVAC system blower is on. Pressure Sensor (13) is capable of measuring the grill pressure with respect to atmosphere as well as vehicle cabin by keeping its open end (15) in atmosphere and vehicle cabin respectively.
Flexible Duct (2) is connected to the chamber (3) having a wire mesh (4) for distributing air flow uniformly. Temperature sensor (5) is provided for measuring temperature of incoming air. Air flow passes though nozzle (6). Another wire mesh (7) is provided after said nozzle (6) for uniform distribution of air flow. External blower (8) is used to suck all air and passing it to atmosphere.
This pressure value from pressure sensor (13) is fed to Control PID (12) which in turn gives instructions to Variable Frequency Drive (9) to run external blower (8) at such a speed that pressure developed at grill outlet (1) becomes zero. At this point all the air flow from the grill outlet (1) passes through the nozzle (6). Due to the shape of the nozzle (6), pressure drop develops across nozzle (6). This pressure drop is measured with a differential pressure sensor (10) and displayed on Control PID (11).

This information is fed to Computer (14) where it is converted into volumetric air flow through software calculations.
Dated this 24th day of March 2009