Question #3

A second system for heating dodecane is going to be built, this system is the same as the one from the previous

question. In order to save money it is being proposed that the system is not insulated.

Your manager would like to know how removing the insulation would affect the dynamics of the system. In

performing this analysis you can assume that the air temperature is 10 °C and that the heat transfer coefficient

between the tank and the air is 20 W m² K¹¹.

In answering this question:

• Clearly show how the changes to the design affect the mass and energy balances for the system.

• Determine how much energy needs to be supplied by the heater to keep the uninsulated tank at a

temperature of 150 °C for an inlet flow rate of 120 L min¹¹.

•

Compare how the insulated and uninsulated systems respond to a stepwise increase in the inlet flowrate

from 120 to 180 L min¹. Use a value of 500 kW for the heater power, and an initial temperature of

150 °C for both cases.

State whether or not you think building the system without insulation is a good idea. Make sure you

justify your decisions.

[10 marks]

3