do you have optical access to your pipe? if yes, there are a number of suitable methods for non-contact temperature measurements, such as Raman and absorption techniques

Thanks Dr. Kiefer for your response. In my problem, the gas flow occurs at average pressure, velocity and temperature of 5 bar, 50m/s and 1500 K, respectively. Temperature may range from 800 K to 1600 K throughout the pipe cross section at a particular instance of time. Can you please suggest a suitable method for measuring the temperature distribution throughout the pipe cross section?

Depending on what species you have in the flow, tomographic spectroscopy may be an option, see e.g. http://dx.doi.org/10.1364/OE.21.001152

Thanks Dr. Kiefer for suggesting this solution. This is an interesting approach to get accurate measurement of the 2-D temperature field. I shall go through this paper thoroughly to see whether we can implement this.

I would request you if you can give me an approximate idea about the cost of implementation of this measurement system.

sure, no problem

A cheap method is a thermocouple.

You need a thermocouple able to reach temperatures of 1600 K. This would be Gold/Platinum. Note furthermore that the wires should be thin ( length to diameter ratio of more than 200) in order to avoid conduction along the wires. A correction for radiation losses might be needed at the highest temperatures. Furthermore the probe can disturbe the flow. Typically I used this kind of probes simply by stretching a thin thermocouple wire across the pipe diameter. By using an array of such probes you can determine a profile. You can also make a system allowing to translate the thermocouple along the stretched wire. This is quite cheap and reasonably accurate. You can use this also to check the validity of another method.

A simple way to measure gas total temperature in this temperature range may be to use a cooled gas temperature sensor emploring a water cooled thermocouple sensor. These sensors are used in rocket engine nozzle gas temperature measurements.I know that Medtherm Corporation provides many sensors of this type to rocket engine industry. A link is attached.

http://medtherm.com/

I do not trust commercial sensors.

Usually they are to short and suffer dramatically from heat conduction to the walls.

Note furthermore that a thermocouple in a gas flow will measure a temperature close to the total temperature of the flow. This is at high Mach number different from the gas temperature (see attached file). For subsonic flows this is a small correction.