Panel (thermal spalling) test condition: the average hot-face temperature of the refractory panel assembly is maintained at approximately what temperature for a 24-hour exposure?

Introduction / Context:
The panel test is a comparative method to assess thermal spalling resistance of refractories under controlled yet severe temperature gradients. The average hot-face temperature is a defining parameter that, along with cycling and quenching protocols, helps rank materials for thermal shock performance.

Given Data / Assumptions:

• Standardized panel tests use a sustained high temperature to impose thermal stress.
• The exposure duration is 24 hours at the specified face temperature.
• We require the commonly cited nominal temperature.

Concept / Approach:
In classic panel test setups, an average face temperature around 1000 °C is maintained to induce significant but practical thermal stress representative of many industrial furnace conditions. This temperature is high enough to reveal differences in microstructural compliance and crack-arrest features without melting most common refractories. Much lower values (e.g., 700 °C) may under-stress the specimen, while much higher values (≥ 1600 °C) are not typical for generalized panel spalling tests due to equipment and safety constraints.

Step-by-Step Solution:
Recall standard panel test protocols.Identify the representative setpoint used widely → ~1000 °C.Select “1000 °C.”

Verification / Alternative check:
Industrial lab procedures and training manuals frequently reference 1000 °C as the face temperature for 24-hour panel exposures before quenching or cycling assessments.

Why Other Options Are Wrong:
700 °C: too low to create severe differential strains in many refractories.1600/2000 °C: atypically high for general panel tests; specialized rigs would be required.500 °C: far below standard high-temperature shock regimes.

Common Pitfalls:
Confusing panel tests with quench or water-immersion shock tests; parameters differ across methods.

Final Answer:
1000 °C