# We will use some of the data from Example 4.18 to show the use of the eff ectiveness-NTU method in solving problems when both exit temperatures are unknown. A liquid food (specifi c heat 4.0 kJ/[kg °C]) fl ows in the inner pipe of a double-pipe heat exchanger. The liquid food enters the heat exchanger at 20°C. The fl ow rate of the liquid food is 0.5 kg/s. In the annular section, hot water at 90°C enters the heat exchanger and fl ows in countercurrent direction at a fl ow rate of 1 kg/s. The average specifi c heat of water is 4.18 kJ/(kg °C). The average overall heat transfer coeffi cient based on the inside area is 2000 W/(m 2 °C), and the diameter of the inner pipe is 5 cm and length is 6.45 m. Assume steady state conditions. Calculate the exit temperature of liquid food and water.

Question-AnswerCategory: Food EngineeringWe will use some of the data from Example 4.18 to show the use of the eff ectiveness-NTU method in solving problems when both exit temperatures are unknown. A liquid food (specifi c heat 4.0 kJ/[kg °C]) fl ows in the inner pipe of a double-pipe heat exchanger. The liquid food enters the heat exchanger at 20°C. The fl ow rate of the liquid food is 0.5 kg/s. In the annular section, hot water at 90°C enters the heat exchanger and fl ows in countercurrent direction at a fl ow rate of 1 kg/s. The average specifi c heat of water is 4.18 kJ/(kg °C). The average overall heat transfer coeffi cient based on the inside area is 2000 W/(m 2 °C), and the diameter of the inner pipe is 5 cm and length is 6.45 m. Assume steady state conditions. Calculate the exit temperature of liquid food and water.

We will use some of the data from Example 4.18 to show the use of the
eff ectiveness-NTU method in solving problems when both exit temperatures are unknown. A liquid food (specifi c heat 4.0 kJ/[kg °C]) fl ows in the
inner pipe of a double-pipe heat exchanger. The liquid food enters the heat
exchanger at 20°C. The fl ow rate of the liquid food is 0.5 kg/s. In the annular
section, hot water at 90°C enters the heat exchanger and fl ows in countercurrent direction at a fl ow rate of 1 kg/s. The average specifi c heat of water
is 4.18 kJ/(kg °C). The average overall heat transfer coeffi cient based on the
inside area is 2000 W/(m 2
°C), and the diameter of the inner pipe is 5 cm and
length is 6.45 m. Assume steady state conditions. Calculate the exit temperature of liquid food and water.