Answer to Question #281393 in Chemical Engineering for alireza naji

Question

The reservoir problem containing 45 kg of liquid with an initial temperature of 45 ° C has one inlet and one outlet equal to the mass flow rates. Liquid water enters at 45 ° C and a mass flow rate of 270 kg / h. A water-cooled cooling coil dissipates energy at a speed of 7.6 kW. The water is mixed well with the help of a vane wheel so that the water temperature is uniform everywhere. The input power from the impeller to the water is 0.6 kW. Inlet and outlet pressures are equal and all kinetic energy and potential effects can be ignored. Determine changes in water temperature over time.

Answer 1

Known Liquid water flows into and out of a well-stirred tank with equal mass flow rates as the water in the tank is cooled by a cooling coil.

Find Plot the variation of water temperature with time.

Schematic and Given Data:

Engineering Model 

1. The control volume is defined by the dashed line on the accompanying diagram.

2. For the control volume, the only significant heat transfer is with the cooling coil. Kinetic and potential energy effects can be neglected.

1 3. The water temperature is uniform with position throughout and varies only with time: T = T(t).

4. The water in the tank is incompressible, and there is no change in pressure between inlet and exit.

Analysis The energy rate balance, Eq. 4.15, reduces with assumption 2 to