Download Problem #1 Water is boiled at Tsat = 100°C by a spherical platinum

ME 223 Heat Transfer Workshop #10
Spring 2017
By: H. Askari
Problem #1
Water is boiled at Tsat = 100°C by a spherical platinum heating element of 15 cm diameter which is immersed in water.
The surface temperature is Ts = 350°C. Calculate the boiling heat transfer coefficient.
Problem #2
Ammonia is liquefied in a horizontal condenser at 37°C by a coolant at 20°C. The pipe layout in the condenser is shown
in the figure. The tubes have an outer diameter of 3.8cm and inner diameter of 3cm. The flow is such that the internal
convection coefficient is 4,000 W/m2.°C and the tubes are made of a material with conductivity of k = 401 W/m.°C. The
average value of overall heat transfer coefficient and the tube length are to be determined.
* Note: Actual tube surface temperature will be larger than 20°C, so you will need to make assumptions. For this, assume
the tube surface temperature is 31°C and verify if this was a reasonable assumption.
Problem #3
Consider water boiled at 1 atm pressure and thus at a saturation temperature of Tsat = 100°C by a nickel electric heater
with diameter of 2 mm. Determine the highest heat flux and surface temperature at which this heater can operate without
burnout issues.