Steam is used to heat a cylindrical open tank of water until it boils, after which a proportion of the water in the tank is vaporised. The tank has an internal diameter of 1 m and is initially filled with water to a depth of 2 m. At the start of the process, this water is at 19°C and has a density of 998 kg/m3 . It may be assumed that ambient atmospheric pressure is 1 bar and that any effects arising from hydrostatic head can be ignored, as can heat losses from the tank to the surrounding environment. The heating medium is saturated steam at 5 bar, which enters a heating coil at the base of the tank at 5 kg/min, loses heat to the water in the tank and condenses to form saturated liquid condensate at this pressure. Using the steam table supplied: a) Find the temperature (°C) and power rating (kW) of the heater coil. b) Find the boiling point of the water in the tank under these conditions, and the time required to bring the water to this temperature. c) Find the proportion of water vaporised if total heating time is 2 hours.
Steam is used to heat a cylindrical open tank of water until it boils, after which a proportion of the water in the tank is vaporised. The tank has an internal diameter of 1 m and is initially filled with water to a depth of 2 m. At the start of the process, this water is at 19°C and has a density of 998 kg/m3 . It may be assumed that ambient atmospheric pressure is 1 bar and that any effects arising from hydrostatic head can be ignored, as can heat losses from the tank to the surrounding environment. The heating medium is saturated steam at 5 bar, which enters a heating coil at the base of the tank at 5 kg/min, loses heat to the water in the tank and condenses to form saturated liquid condensate at this pressure. Using the steam table supplied:
a) Find the temperature (°C) and power rating (kW) of the heater coil.
b) Find the boiling point of the water in the tank under these conditions, and the time required to bring the water to this temperature.
c) Find the proportion of water vaporised if total heating time is 2 hours.
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