Factors affecting temperature change

Accuracy required- impact of sensor accuracy on overall measurement accuracy.

Length of deployment

Thermocouple material selection

Selection of the Measuring Junction

Durability

Determine the maximum and minimum range in which you want to measure the temperature and select the thermocouple with higher Maximum temperature range.

Check whether the linearity of thermocouple meets the range requirement.

Select the correct sheath material to resist chemical reaction.

Perfect isolation to resist noise protection.

Thermocouple should withstand vibration and abrasion.

Appropriate connectors and cables to be used between thermocouple and measuring instruments.

Appropriate measuring instrument should be used to give an accurate result.

Steeped Shank- Provide faster response time and lower drag force.

Straight Shank- Extremely strong, but response time is slower and drag force on the fluid flow is high.

Tapered Shank- Provide good response time and strength.

For best temperature measurement accuracy,  the “U” dimension should be long enough to permit the entire temperature-sensitive part of the measuring instrument to project into the medium being measured.

Liquid temperature measurement: One inch or greater.

Gas temperature measurement:  three inches or greater.

Fluid flowing past the well forms a turbulent wake (the Von Karman Trail), which has a definite frequency based on the diameter of the well and the velocity of the fluid.

The thermowell must have sufficient stiffness so that the wake frequency will never equal the natural frequency of the thermowell itself. If the natural frequency of the well were to coincide with the wake frequency, the well would vibrate to destruction and break off.

Maximum or operating temperature

Maximum or operating pressure

Fluid(gas or liquid) velocity

Fluid Density.