Mode Across 2.5-cm air gap evacuated to a pressure of 10-6 atm and subjected to AT 100°C 30°C Free convection, AT-30°C Vertical plate 0.3 m [1 ft] high in air Horizontal cylinder, 5-cm diameter, in air Horizontal cylinder, 2-cm diameter, in water Heat transfer across 1.5-cm vertical air 60°C gap with AT Fine wire in air, d=0.02 mm, AT=55°C Forced convection Airflow at 2 m/s over 0.2-m square plate Airflow at 35 m/s over 0.75-m square plate Airflow at Mach number=3, p=1/20 atm, Too -40°C, across 0.2-m square plate Air at 2 atm flowing in 2.5-cm-diameter tube at 10 m/s Water at 0.5 kg/s flowing in 2.5-cm-diameter tube Airflow across 5-cm-diameter cylinder with velocity of 50 m/s h W/m². °C Btu/h ft²2 °F 0.087 0.015 4.5 0.79 6.5 1.14 890 157 2.64 0.46 490 86 222 12 2.1 75 13.2 56 9.9 65 11.4 3500 616 180 32 Liquid bismuth at 4.5 kg/s and 420°C in 5.0-cm-diameter tube 3410 600 Airflow at 50 m/s across fine wire, d=0.04 mm 3850 678 Boiling water In a pool or container Flowing in a tube 2500-35,000 5000-100,000 Condensation of water vapor, 1 atm Vertical surfaces Outside horizontal tubes Dropwise condensation 4000-11,300 440-6200 880-17,600 700-2000 9500-25,000 1700-4400 170,000-290,000 30,000-50,000