3. Consider a spherical balloon with volume of 1 m³ balloon filled with helium at 340 kPa

and 80°C. The balloon undergoes a process which increases its volume by 80%, and its

temperature is kept constant.

(a) What is the final pressure of the balloon?

(b) How much heat must be added to ensure the temperature remains constant during

this process?

(c) If the process takes 30 seconds, what is the heat transfer coefficient if the sur-

rounding temperature is 20°C? Assume an average surface area for the balloon

between the initial and final state.

Hint: Assume helium is an ideal gas with Rue = 2.077 kJ/kg-K.