EXAMPLE 4.4 Consider a stirred tank heater. It is a square tank 0.5 m on its sides and 2 m high and is filled with water at 20°C. Water is fed to the tank at a flow rate of IL/s and exits out at the same flow rate from the top of the tank. The temperature of inlet water is 20°C. At time t = 0 s, water in the tank is heated by a coil containing steam whose overall heat transfer coefficient based on the outside area of the coil is 200 W/ m²-K. The outside area of the coil through which heat exchange takes place is 1 m². The temperature of the steam is 250°C. The specific heat capacity of water is 4184 J/ kg-K. After how much time is the temperature of exit water 28°C? What is the maximum temperature that can be reached in the tank? h=700 s

EXAMPLE 4.4 Consider a stirred tank heater. It is a square tank 0.5 m on its sides and 2 m high and is filled with water at 20°C. Water is fed to the tank at a flow rate of IL/s and exits out at the same flow rate from the top of the tank. The temperature of inlet water is 20°C. At time t = 0 s, water in the tank is heated by a coil containing steam whose overall heat transfer coefficient based on the outside area of the coil is 200 W/ m²-K. The outside area of the coil through which heat exchange takes place is 1 m². The temperature of the steam is 250°C. The specific heat capacity of water is 4184 J/ kg-K. After how much time is the temperature of exit water 28°C? What is the maximum temperature that can be reached in the tank? h=700 s