The purpose of the isokinetic sampling nozzle is to:

The isokinetic sampling nozzle is designed specifically to gather representative samples of steam or gas from a system, making it particularly useful in applications where accurate analysis of the steam composition is essential. It achieves this by ensuring that the velocity of the gas at the inlet of the nozzle matches the velocity of the gas in the surrounding flow, minimizing the chances of turbulence and other flow disturbances that could affect sample accuracy.

By using isokinetic sampling techniques, operators can obtain steam samples that truly reflect the conditions within the system, allowing for better monitoring, analysis, and decision-making regarding steam quality and system performance. This representative sampling is crucial for assessing factors such as moisture content, chemical composition, and other properties that influence operational efficiency and safety.

In contrast, the other options pertain to different functions outside the specific purpose of isokinetic sampling. For instance, measuring flow rate in the boiler or discharging excess steam are operational processes that involve different equipment and principles. Improving steam quality relates to the treatment and management of steam, not specifically to the mechanisms of sampling. This means that while these concepts are relevant to steam system management, they do not align with the primary function of an isokinetic sampling nozzle.