Thermal wells used in temperature measurements should have
A. Very thick walls
B. Low emissivity
C. Polished surface
D. High transmissivity of radiation
Answer: Option C
Solution (By Examveda Team)
Thermowells protect temperature sensors from harsh process conditions, but their design also affects measurement accuracy.A polished surface reduces the emissivity of the thermowell, which minimizes radiative heat losses to the surroundings and ensures the sensor measures the true process temperature.
Very thick walls provide mechanical strength to withstand high pressures and flows, but they cause increased thermal lag, slowing down the sensor’s response to temperature changes, which can be problematic for process control applications.
Low emissivity is effectively achieved through a polished surface, which is why Option C covers this aspect practically.
High transmissivity of radiation is not relevant since thermowells measure temperature through conduction, not radiation transmission.
For accurate and fast temperature measurement in process control, a polished surface is essential, making Option C the correct choice in this context.
This Question Belongs to Chemical Engineering >> Process Control And Instrumentation
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The correct answer is:
A. Very thick walls
✅ Explanation:
Thermal wells (thermowells) are protective housings inserted into a process stream to shield temperature sensors (like thermocouples or RTDs) from pressure, corrosion, and flow-induced damage.
For accurate and safe temperature measurement, thermowells should have:
🔍 Key Requirement:
A. Very thick walls ✅
Ensures mechanical strength
Withstands high-pressure and high-velocity fluids
Reduces risk of vibration-induced failure (e.g., from vortex shedding)
Hence, correct answer
❌ Why the Others Are Incorrect:
B. Low emissivity: Not relevant — thermowells measure conductive heat, not radiant heat
C. Polished surface: Affects emissivity but not crucial to thermowell performance
D. High transmissivity of radiation: Irrelevant — thermowells are opaque metals, not used for radiation measurement
✅ Final Answer:
A. Very thick walls