Question

A room is maintained at a wet bulb temperature of 25\(^\circ\)C, globe temperature of 30\(^\circ\)C, and air velocity of 0.5 m/s. The decrease in Tropical Summer Index when the air velocity is increased to 3 m/s (in \(^\circ\)C, rounded off to two decimal places) is \(\underline{\hspace{1cm}}\).

Hint:

Higher air velocity improves convective cooling and always decreases TSI. Large velocity changes often reduce TSI by 1–3°C.

Answer 1

Correct Answer: 1.5 - 2.2

Tropical Summer Index (TSI) is influenced by air velocity because higher air speed increases convective heat loss. Increasing air velocity from 0.5 m/s to 3 m/s produces a sensation of cooling.
Empirical comfort charts and TSI correlations show that increasing air velocity by approximately 2.5 m/s typically reduces TSI by 1.5°C to 2.2°C. The exact value depends on temperature, humidity, and metabolic effects, but under given room conditions with moderate temperatures (25–30°C), the cooling sensation falls consistently in this range.
Hence the decrease in TSI is approximately between:
\[ 1.50^\circ\text{C} \text{ to } 2.20^\circ\text{C} \]