Experimental Hypersonic Test facilities and measurements Notes | EduRev

: Experimental Hypersonic Test facilities and measurements Notes | EduRev

 Page 1


NPTEL – Aerospace 
 
Module-7: Experimental Hypersonic Test facilities and 
measurements 
Lecture-31: Hypersonic wind tunnel 
31.1 Hypersonic Test Facilities: 
Hypersonic flow is a flow for which speeds are much larger than the local speed of 
sound. In general hypersonic flow is defined as the flow at Mach 5 or greater at which 
physical properties of the flow changes rapidly. A test facility designed or considered 
for hypersonic testing should simulate the typical flow features of this flow regime. 
These flow features include thin shock layer, entropy layer, viscous interaction and 
most importantly high total or stagnation temperature of the flow. This section deals 
with most common facilities for hypersonic testing.  
31.2 Continuous Hypersonic Wind Tunnel  
Continuous hypersonic wind tunnel is comprised of a compressor, heater, nozzle, test 
section, diffuser, second throat and vacuum chamber as major components. Schematic 
of such tunnel is as shown in Fig.31.1. During the experimental testing, continuous 
operation can be achieved by providing continuously operating compressors. Such 
high pressure air is then heated in the heater so as to reach the desired stagnation 
temperature. Valve is then operated if sufficient low pressure is attained in the 
vacuum chamber. Expansion of the air through the convergent divergent nozzle sets 
the hypersonic flow in the test section. Onwards deceleration of the flow through the 
second throat ensures the low speed air at the compressor inlet.  
 
1. Heater 2.Valve 3.First Throat 4.Test section 5.Diffuser 6.Second throat 7.Valve 
8.Vacuum Chamber 9.Vacuum pump 10. Multistage compressor 
Fig. 31.1: Schematic diagram of continuous hypersonic wind tunnel circuit 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 1 of 36 
Page 2


NPTEL – Aerospace 
 
Module-7: Experimental Hypersonic Test facilities and 
measurements 
Lecture-31: Hypersonic wind tunnel 
31.1 Hypersonic Test Facilities: 
Hypersonic flow is a flow for which speeds are much larger than the local speed of 
sound. In general hypersonic flow is defined as the flow at Mach 5 or greater at which 
physical properties of the flow changes rapidly. A test facility designed or considered 
for hypersonic testing should simulate the typical flow features of this flow regime. 
These flow features include thin shock layer, entropy layer, viscous interaction and 
most importantly high total or stagnation temperature of the flow. This section deals 
with most common facilities for hypersonic testing.  
31.2 Continuous Hypersonic Wind Tunnel  
Continuous hypersonic wind tunnel is comprised of a compressor, heater, nozzle, test 
section, diffuser, second throat and vacuum chamber as major components. Schematic 
of such tunnel is as shown in Fig.31.1. During the experimental testing, continuous 
operation can be achieved by providing continuously operating compressors. Such 
high pressure air is then heated in the heater so as to reach the desired stagnation 
temperature. Valve is then operated if sufficient low pressure is attained in the 
vacuum chamber. Expansion of the air through the convergent divergent nozzle sets 
the hypersonic flow in the test section. Onwards deceleration of the flow through the 
second throat ensures the low speed air at the compressor inlet.  
 
1. Heater 2.Valve 3.First Throat 4.Test section 5.Diffuser 6.Second throat 7.Valve 
8.Vacuum Chamber 9.Vacuum pump 10. Multistage compressor 
Fig. 31.1: Schematic diagram of continuous hypersonic wind tunnel circuit 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 1 of 36 
NPTEL – Aerospace 
 
31.2.1 Heaters 
Condensation free hypersonic expansion of air requires high stagnation temperatures 
as per the Mach number attained in the test section. In the conventional hypersonic 
tunnels different types of heater are used to provide the appropriate temperature. The 
combustion, the electric resistance and the arc-jet type heaters are suitable for 
continuous or long duration operation. Industrial heaters where air is heated using 
combustion products are generally preferred up to Mach 8. Resistance wire electric 
heaters are used to provide for Mach numbers up to 12 to 14. Ceramic materials or 
special alloys provide support for the heating elements in this heater. Nitrogen is used 
as the working fluid for high stagnation conditions with direct electric resistance 
heating because of serious oxidation rates. Direct electric arc heating of the working 
fluid is used in arc-jet heaters. The moderate stagnation temperatures (<5500° K) for 
nitrogen freestream are obtained with such type of heaters.  
31.2.2 Hypersonic Nozzles 
Convergent divergent axi-symmetric nozzles are generally preferred in the hypersonic 
tunnels. These nozzles expand the high pressure and high temperature air to the 
desired Mach number in the test section. These nozzles can also be equipped contour 
to ensure the uniformity of the flow in the test section. The throat of the nozzle needs 
to be water-cooled for continuous and also for blow-down hypersonic tunnels 
operating at high stagnation temperatures or high enthalpy conditions. Frequent 
change of the throat is also encountered for such high enthalpy operations. Beryllium-
copper is often used for the throat liners material to provide strength with high heat 
conductivity. In an alternative design, the throat liner, made of titanium, zirconium 
and molybdenum alloy, is cooled by working gas (air or nitrogen) before its entry in 
to the heater.  
 
 
 
 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 2 of 36 
Page 3


NPTEL – Aerospace 
 
Module-7: Experimental Hypersonic Test facilities and 
measurements 
Lecture-31: Hypersonic wind tunnel 
31.1 Hypersonic Test Facilities: 
Hypersonic flow is a flow for which speeds are much larger than the local speed of 
sound. In general hypersonic flow is defined as the flow at Mach 5 or greater at which 
physical properties of the flow changes rapidly. A test facility designed or considered 
for hypersonic testing should simulate the typical flow features of this flow regime. 
These flow features include thin shock layer, entropy layer, viscous interaction and 
most importantly high total or stagnation temperature of the flow. This section deals 
with most common facilities for hypersonic testing.  
31.2 Continuous Hypersonic Wind Tunnel  
Continuous hypersonic wind tunnel is comprised of a compressor, heater, nozzle, test 
section, diffuser, second throat and vacuum chamber as major components. Schematic 
of such tunnel is as shown in Fig.31.1. During the experimental testing, continuous 
operation can be achieved by providing continuously operating compressors. Such 
high pressure air is then heated in the heater so as to reach the desired stagnation 
temperature. Valve is then operated if sufficient low pressure is attained in the 
vacuum chamber. Expansion of the air through the convergent divergent nozzle sets 
the hypersonic flow in the test section. Onwards deceleration of the flow through the 
second throat ensures the low speed air at the compressor inlet.  
 
1. Heater 2.Valve 3.First Throat 4.Test section 5.Diffuser 6.Second throat 7.Valve 
8.Vacuum Chamber 9.Vacuum pump 10. Multistage compressor 
Fig. 31.1: Schematic diagram of continuous hypersonic wind tunnel circuit 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 1 of 36 
NPTEL – Aerospace 
 
31.2.1 Heaters 
Condensation free hypersonic expansion of air requires high stagnation temperatures 
as per the Mach number attained in the test section. In the conventional hypersonic 
tunnels different types of heater are used to provide the appropriate temperature. The 
combustion, the electric resistance and the arc-jet type heaters are suitable for 
continuous or long duration operation. Industrial heaters where air is heated using 
combustion products are generally preferred up to Mach 8. Resistance wire electric 
heaters are used to provide for Mach numbers up to 12 to 14. Ceramic materials or 
special alloys provide support for the heating elements in this heater. Nitrogen is used 
as the working fluid for high stagnation conditions with direct electric resistance 
heating because of serious oxidation rates. Direct electric arc heating of the working 
fluid is used in arc-jet heaters. The moderate stagnation temperatures (<5500° K) for 
nitrogen freestream are obtained with such type of heaters.  
31.2.2 Hypersonic Nozzles 
Convergent divergent axi-symmetric nozzles are generally preferred in the hypersonic 
tunnels. These nozzles expand the high pressure and high temperature air to the 
desired Mach number in the test section. These nozzles can also be equipped contour 
to ensure the uniformity of the flow in the test section. The throat of the nozzle needs 
to be water-cooled for continuous and also for blow-down hypersonic tunnels 
operating at high stagnation temperatures or high enthalpy conditions. Frequent 
change of the throat is also encountered for such high enthalpy operations. Beryllium-
copper is often used for the throat liners material to provide strength with high heat 
conductivity. In an alternative design, the throat liner, made of titanium, zirconium 
and molybdenum alloy, is cooled by working gas (air or nitrogen) before its entry in 
to the heater.  
 
 
 
 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 2 of 36 
NPTEL – Aerospace 
 
31.2.3 Hypersonic Diffuser 
Typical hypersonic tunnel diffuser is comprised of fixed contraction followed by a 
constant area diffuser duct. This contraction reduces the flow Mach number. A 
complex three dimensional shock pattern executes this Mach number reduction. These 
shock waves interact with the boundary layer during the process. This region is 
followed by a subsonic flow where deceleration takes place in a divergent section. 
Diffuser design is very important for the continuous closed circuit wind tunnels due to 
its dependence on compressor characteristics and drive power. However the design of 
diffuser for the impulse type facilities is carried out mainly to evaluate the useful test 
time. 
31.3 Blow-down Hypersonic Wind Tunnel 
Power requirement of a wind tunnel is directly proportional with the square of the 
required velocity in the test section. Hence installation of a continuous closed circuit 
wind tunnel remains a costly affair. In view of this, impulsive experimental facilities 
like blow-down wind tunnels are designed and installed to simulate the hypersonic 
flow. This wind tunnel is comprised of major components viz. multi-stage 
compressor, dryer, heater, settling chamber, nozzle, test section, diffuser and vacuum 
tank. Schematic of the typical blow-down type wind tunnel is as shown in Fig. 31.2. 
During the operation of the tunnel, air or nitrogen is initially compressed to high 
pressure using the multistage compressor as per the stagnation pressure requirement. 
This high pressure fluid is then dried in the dryer to remove the moisture content of 
the same before it is stored in large tanks. Storage or regenerative type heaters have 
been developed for application in case of such intermittent or blow-down tunnels. 
These heaters are essentially insulated pressure vessels. Use of such heaters makes it 
possible to increase the temperature of the high pressure air but with lower power 
requirement. The pebbles used in the heaters are mostly refractory ceramic pebbles or 
cored bricks which are heated using electrical resistance elements or by products of 
combustion. This high pressure fluid is allowed to pass over a large bed of ceramic 
pebbles during the experiment. A typical experiment starts after the throttling valve 
opening due to which the high pressure air passes through the heater and onwards 
towards to the test section. In some cases a settling chamber is built to provide the 
high pressure and high temperature reservoir before its expansion in the nozzle. 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 3 of 36 
Page 4


NPTEL – Aerospace 
 
Module-7: Experimental Hypersonic Test facilities and 
measurements 
Lecture-31: Hypersonic wind tunnel 
31.1 Hypersonic Test Facilities: 
Hypersonic flow is a flow for which speeds are much larger than the local speed of 
sound. In general hypersonic flow is defined as the flow at Mach 5 or greater at which 
physical properties of the flow changes rapidly. A test facility designed or considered 
for hypersonic testing should simulate the typical flow features of this flow regime. 
These flow features include thin shock layer, entropy layer, viscous interaction and 
most importantly high total or stagnation temperature of the flow. This section deals 
with most common facilities for hypersonic testing.  
31.2 Continuous Hypersonic Wind Tunnel  
Continuous hypersonic wind tunnel is comprised of a compressor, heater, nozzle, test 
section, diffuser, second throat and vacuum chamber as major components. Schematic 
of such tunnel is as shown in Fig.31.1. During the experimental testing, continuous 
operation can be achieved by providing continuously operating compressors. Such 
high pressure air is then heated in the heater so as to reach the desired stagnation 
temperature. Valve is then operated if sufficient low pressure is attained in the 
vacuum chamber. Expansion of the air through the convergent divergent nozzle sets 
the hypersonic flow in the test section. Onwards deceleration of the flow through the 
second throat ensures the low speed air at the compressor inlet.  
 
1. Heater 2.Valve 3.First Throat 4.Test section 5.Diffuser 6.Second throat 7.Valve 
8.Vacuum Chamber 9.Vacuum pump 10. Multistage compressor 
Fig. 31.1: Schematic diagram of continuous hypersonic wind tunnel circuit 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 1 of 36 
NPTEL – Aerospace 
 
31.2.1 Heaters 
Condensation free hypersonic expansion of air requires high stagnation temperatures 
as per the Mach number attained in the test section. In the conventional hypersonic 
tunnels different types of heater are used to provide the appropriate temperature. The 
combustion, the electric resistance and the arc-jet type heaters are suitable for 
continuous or long duration operation. Industrial heaters where air is heated using 
combustion products are generally preferred up to Mach 8. Resistance wire electric 
heaters are used to provide for Mach numbers up to 12 to 14. Ceramic materials or 
special alloys provide support for the heating elements in this heater. Nitrogen is used 
as the working fluid for high stagnation conditions with direct electric resistance 
heating because of serious oxidation rates. Direct electric arc heating of the working 
fluid is used in arc-jet heaters. The moderate stagnation temperatures (<5500° K) for 
nitrogen freestream are obtained with such type of heaters.  
31.2.2 Hypersonic Nozzles 
Convergent divergent axi-symmetric nozzles are generally preferred in the hypersonic 
tunnels. These nozzles expand the high pressure and high temperature air to the 
desired Mach number in the test section. These nozzles can also be equipped contour 
to ensure the uniformity of the flow in the test section. The throat of the nozzle needs 
to be water-cooled for continuous and also for blow-down hypersonic tunnels 
operating at high stagnation temperatures or high enthalpy conditions. Frequent 
change of the throat is also encountered for such high enthalpy operations. Beryllium-
copper is often used for the throat liners material to provide strength with high heat 
conductivity. In an alternative design, the throat liner, made of titanium, zirconium 
and molybdenum alloy, is cooled by working gas (air or nitrogen) before its entry in 
to the heater.  
 
 
 
 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 2 of 36 
NPTEL – Aerospace 
 
31.2.3 Hypersonic Diffuser 
Typical hypersonic tunnel diffuser is comprised of fixed contraction followed by a 
constant area diffuser duct. This contraction reduces the flow Mach number. A 
complex three dimensional shock pattern executes this Mach number reduction. These 
shock waves interact with the boundary layer during the process. This region is 
followed by a subsonic flow where deceleration takes place in a divergent section. 
Diffuser design is very important for the continuous closed circuit wind tunnels due to 
its dependence on compressor characteristics and drive power. However the design of 
diffuser for the impulse type facilities is carried out mainly to evaluate the useful test 
time. 
31.3 Blow-down Hypersonic Wind Tunnel 
Power requirement of a wind tunnel is directly proportional with the square of the 
required velocity in the test section. Hence installation of a continuous closed circuit 
wind tunnel remains a costly affair. In view of this, impulsive experimental facilities 
like blow-down wind tunnels are designed and installed to simulate the hypersonic 
flow. This wind tunnel is comprised of major components viz. multi-stage 
compressor, dryer, heater, settling chamber, nozzle, test section, diffuser and vacuum 
tank. Schematic of the typical blow-down type wind tunnel is as shown in Fig. 31.2. 
During the operation of the tunnel, air or nitrogen is initially compressed to high 
pressure using the multistage compressor as per the stagnation pressure requirement. 
This high pressure fluid is then dried in the dryer to remove the moisture content of 
the same before it is stored in large tanks. Storage or regenerative type heaters have 
been developed for application in case of such intermittent or blow-down tunnels. 
These heaters are essentially insulated pressure vessels. Use of such heaters makes it 
possible to increase the temperature of the high pressure air but with lower power 
requirement. The pebbles used in the heaters are mostly refractory ceramic pebbles or 
cored bricks which are heated using electrical resistance elements or by products of 
combustion. This high pressure fluid is allowed to pass over a large bed of ceramic 
pebbles during the experiment. A typical experiment starts after the throttling valve 
opening due to which the high pressure air passes through the heater and onwards 
towards to the test section. In some cases a settling chamber is built to provide the 
high pressure and high temperature reservoir before its expansion in the nozzle. 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 3 of 36 
NPTEL – Aerospace 
 
Expansion of the gas in the nozzle attains the required hypersonic freestream 
conditions in the nozzle. Higher temperature values of the flow in the test section are 
preferred to prevent the liquefaction of the air as it expands to very low temperatures 
in the nozzle.  
 
1. Multistage compressor 2.Dryer 3.High pressure air storage 4.Gas inlet 5. Refractory 
pebbles 6.Start valve 7.Nozzle with throat cooling apparatus 8.Test section 9.Diffuser 
second throat 10.Valve 11.Vacuum Chamber 12. Vacuum pump 
Fig. 31.2: Schematic drawing of the blow-down hypersonic wind tunnel circuit 
 
 
 
 
 
 
 
 
 
 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 4 of 36 
Page 5


NPTEL – Aerospace 
 
Module-7: Experimental Hypersonic Test facilities and 
measurements 
Lecture-31: Hypersonic wind tunnel 
31.1 Hypersonic Test Facilities: 
Hypersonic flow is a flow for which speeds are much larger than the local speed of 
sound. In general hypersonic flow is defined as the flow at Mach 5 or greater at which 
physical properties of the flow changes rapidly. A test facility designed or considered 
for hypersonic testing should simulate the typical flow features of this flow regime. 
These flow features include thin shock layer, entropy layer, viscous interaction and 
most importantly high total or stagnation temperature of the flow. This section deals 
with most common facilities for hypersonic testing.  
31.2 Continuous Hypersonic Wind Tunnel  
Continuous hypersonic wind tunnel is comprised of a compressor, heater, nozzle, test 
section, diffuser, second throat and vacuum chamber as major components. Schematic 
of such tunnel is as shown in Fig.31.1. During the experimental testing, continuous 
operation can be achieved by providing continuously operating compressors. Such 
high pressure air is then heated in the heater so as to reach the desired stagnation 
temperature. Valve is then operated if sufficient low pressure is attained in the 
vacuum chamber. Expansion of the air through the convergent divergent nozzle sets 
the hypersonic flow in the test section. Onwards deceleration of the flow through the 
second throat ensures the low speed air at the compressor inlet.  
 
1. Heater 2.Valve 3.First Throat 4.Test section 5.Diffuser 6.Second throat 7.Valve 
8.Vacuum Chamber 9.Vacuum pump 10. Multistage compressor 
Fig. 31.1: Schematic diagram of continuous hypersonic wind tunnel circuit 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 1 of 36 
NPTEL – Aerospace 
 
31.2.1 Heaters 
Condensation free hypersonic expansion of air requires high stagnation temperatures 
as per the Mach number attained in the test section. In the conventional hypersonic 
tunnels different types of heater are used to provide the appropriate temperature. The 
combustion, the electric resistance and the arc-jet type heaters are suitable for 
continuous or long duration operation. Industrial heaters where air is heated using 
combustion products are generally preferred up to Mach 8. Resistance wire electric 
heaters are used to provide for Mach numbers up to 12 to 14. Ceramic materials or 
special alloys provide support for the heating elements in this heater. Nitrogen is used 
as the working fluid for high stagnation conditions with direct electric resistance 
heating because of serious oxidation rates. Direct electric arc heating of the working 
fluid is used in arc-jet heaters. The moderate stagnation temperatures (<5500° K) for 
nitrogen freestream are obtained with such type of heaters.  
31.2.2 Hypersonic Nozzles 
Convergent divergent axi-symmetric nozzles are generally preferred in the hypersonic 
tunnels. These nozzles expand the high pressure and high temperature air to the 
desired Mach number in the test section. These nozzles can also be equipped contour 
to ensure the uniformity of the flow in the test section. The throat of the nozzle needs 
to be water-cooled for continuous and also for blow-down hypersonic tunnels 
operating at high stagnation temperatures or high enthalpy conditions. Frequent 
change of the throat is also encountered for such high enthalpy operations. Beryllium-
copper is often used for the throat liners material to provide strength with high heat 
conductivity. In an alternative design, the throat liner, made of titanium, zirconium 
and molybdenum alloy, is cooled by working gas (air or nitrogen) before its entry in 
to the heater.  
 
 
 
 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 2 of 36 
NPTEL – Aerospace 
 
31.2.3 Hypersonic Diffuser 
Typical hypersonic tunnel diffuser is comprised of fixed contraction followed by a 
constant area diffuser duct. This contraction reduces the flow Mach number. A 
complex three dimensional shock pattern executes this Mach number reduction. These 
shock waves interact with the boundary layer during the process. This region is 
followed by a subsonic flow where deceleration takes place in a divergent section. 
Diffuser design is very important for the continuous closed circuit wind tunnels due to 
its dependence on compressor characteristics and drive power. However the design of 
diffuser for the impulse type facilities is carried out mainly to evaluate the useful test 
time. 
31.3 Blow-down Hypersonic Wind Tunnel 
Power requirement of a wind tunnel is directly proportional with the square of the 
required velocity in the test section. Hence installation of a continuous closed circuit 
wind tunnel remains a costly affair. In view of this, impulsive experimental facilities 
like blow-down wind tunnels are designed and installed to simulate the hypersonic 
flow. This wind tunnel is comprised of major components viz. multi-stage 
compressor, dryer, heater, settling chamber, nozzle, test section, diffuser and vacuum 
tank. Schematic of the typical blow-down type wind tunnel is as shown in Fig. 31.2. 
During the operation of the tunnel, air or nitrogen is initially compressed to high 
pressure using the multistage compressor as per the stagnation pressure requirement. 
This high pressure fluid is then dried in the dryer to remove the moisture content of 
the same before it is stored in large tanks. Storage or regenerative type heaters have 
been developed for application in case of such intermittent or blow-down tunnels. 
These heaters are essentially insulated pressure vessels. Use of such heaters makes it 
possible to increase the temperature of the high pressure air but with lower power 
requirement. The pebbles used in the heaters are mostly refractory ceramic pebbles or 
cored bricks which are heated using electrical resistance elements or by products of 
combustion. This high pressure fluid is allowed to pass over a large bed of ceramic 
pebbles during the experiment. A typical experiment starts after the throttling valve 
opening due to which the high pressure air passes through the heater and onwards 
towards to the test section. In some cases a settling chamber is built to provide the 
high pressure and high temperature reservoir before its expansion in the nozzle. 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 3 of 36 
NPTEL – Aerospace 
 
Expansion of the gas in the nozzle attains the required hypersonic freestream 
conditions in the nozzle. Higher temperature values of the flow in the test section are 
preferred to prevent the liquefaction of the air as it expands to very low temperatures 
in the nozzle.  
 
1. Multistage compressor 2.Dryer 3.High pressure air storage 4.Gas inlet 5. Refractory 
pebbles 6.Start valve 7.Nozzle with throat cooling apparatus 8.Test section 9.Diffuser 
second throat 10.Valve 11.Vacuum Chamber 12. Vacuum pump 
Fig. 31.2: Schematic drawing of the blow-down hypersonic wind tunnel circuit 
 
 
 
 
 
 
 
 
 
 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 4 of 36 
NPTEL – Aerospace 
 
Lecture-32: Hypersonic wind tunnel and its calibration 
32.1 Nitrogen Wind Tunnel 
It is a blow-down wind tunnel operated with high pressure Nitrogen gas. Hence the 
arrangement of this tunnel is same as that of a blow-down wind tunnel (Fig. 32.1). 
The high pressure Nitrogen gas is initially heated by a graphite resistance heater 
contained within a pressure vessel and then allowed to expand through the nozzle. 
Experimental duration in these tunnels is in the range of 1 to 4 seconds. Nitrogen 
wind tunnels also operate between two temperature limits discussed herein. The lower 
limit on temperature is essentially to avoid condensation effects in the test section, 
and the upper limit on the temperature is necessarily governed by the heater. Two 
servo-systems are installed for two reasons viz. controlling the gas flow to maintain a 
constant stagnation pressure and ensuring a constant current through the heater which 
effectively controls the stagnation temperature.  
 
1.High pressure vessel  2.Graphite resistance heater  3.Nozzle with water cooling at 
throat 4.Multistage compressor 5.Test section 6.Diffuser Second throat 7.Valve 
8.Vacuum Chamber 9.Vacuum pump   
Fig 32.1: Schematic drawing of Nitrogen wind tunnel circuit 
 
 
Joint initiative of IITs and IISc – Funded by MHRD                                                            Page 5 of 36 
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