Question

A long thin-walled double-pipe heat exchanger with tube and shell diameters of 1.0 cm and 2.5 cm, respectively, is used to condense refrigerant -134a by water at 20°C. The refrigerant flows through the tube with a convection heat transfer coefficient of hi = 4500 W/m2 °C. Water flows through the shell at a rate of 0.5 kg/s. Determine the overall heat transfer coefficient of this heat exchanger.

Answer 1

The overall heat transfer coefficient of a heat exchanger can be calculated using the equation: 1/U = 1/hi + R1 + R2 + 1/hs.

Step-by-step explanation:

The overall heat transfer coefficient of a heat exchanger is a measure of the thermal conductivity of the system and describes how efficiently heat is transferred between the two fluids. To calculate the overall heat transfer coefficient, you first need to determine the individual heat transfer coefficients and the thermal resistances of the tube and shell sides.

The overall heat transfer coefficient (U) can be calculated using the equation: 1/U = 1/hi + R1 + R2 + 1/hs, where hi is the convection heat transfer coefficient of the tube side, R1 is the thermal resistance of the tube side, R2 is the thermal resistance of the shell side, and hs is the convection heat transfer coefficient of the shell side.

In this case, the convection heat transfer coefficient of the tube side is given as 4500 W/m2 °C and the flow rate of water through the shell side is given as 0.5 kg/s. By substituting these values into the equation, you can calculate the overall heat transfer coefficient.