An air-water mixture is flowing in a tube with a diameter of 25.4 mm. The two-phase mixture enters the tube at 15°C and exits at 75°C, while the tube surface temperature is maintained at 80°C. If the superficial gas and liquid velocities are 1 m/s and 2 m/s, respectively, determine the two-phase heat transfer coefficient htp for

(a) The horizontal tube (θ = 0°) and
(b) The vertical tube (θ = 90°), and compare the two results. Assume the surface tension is σ = 0.068 N/m and the void fraction is α = 0.33.