Chimney draught — factors affecting natural draught magnitude Select all influential factors. The available chimney draught varies with which of the following?

Introduction:
Natural draught arises from density differences between hot flue gases in a chimney and cooler outside air. The pressure head it produces is small and sensitive to several environmental and design factors. Recognizing these dependencies is vital for sizing chimneys and assessing seasonal performance.

Given Data / Assumptions:

• Chimney operating with hot gases hotter than ambient air.
• Steady conditions but subject to weather changes.

Concept / Approach:
The draught pressure is proportional to the height of the chimney and the difference between outside air density and flue gas density, which depends on temperature (and composition). Climate affects ambient temperature, wind, and barometric pressure, all of which alter density and, hence, draught. Therefore, chimney height, gas temperature, and climatic conditions all influence natural draught magnitude.

Step-by-Step Solution:

Verification / Alternative check:
Stack effect formulas include chimney height and temperatures; climatic variability appears through ambient temperature and pressure terms, confirming all listed factors matter.

Why Other Options Are Wrong:

• Any single factor alone omits other equally important influences.
• None of these: contradicts both theory and practice.

Common Pitfalls:
Ignoring seasonal derating of natural-draught systems; assuming height alone guarantees adequate draught regardless of temperature or weather.

Final Answer: