Batch Reactor Heat Exchanger:

Chemical reactions in batch reactors require thermal management. Depending on the needed heat duty and other constraints either an outer jacket or internal coil is being utilized. Assume a reactor as a closed system and the heat exchanger with an inlet and outlet.

A- General Scheme

Write an energy balance on the system.

For this part assume that for the jacket/coil the heat transfer coefficient is U, heat generation is Q, impeller work is Ws.

a) How do you find Ws, knowing the spec of the impeller and its speed?

b) For a flat-blade turbine agitator, with a disk having six blades, installed in a tank with a diameter of 1.83 m and filled at the same height calculate the needed power if the turbine rotates at 100 rpm, the fluid viscosity is 10 cp and its density is 929 Kg/m³. This tank has four baffles each having 0.15 m width. The turbine diameter is 0.61 m.

B- Cooldown

A batch reactor ( V=1.4 m³) is equipped with a jacket to cool down the reactor content from 80 to 50 C, after the reaction is completed. The inlet chilled water to the jacket is at 5 C. Graph the reactor and outlet temperature of the fluid in the jacket as a function of time when the jacket fluid is running through the system at:

A. 0.5 Liter/s

B. 1.35 Liter/s

Note at this point the impeller is off, so Ws is zero, and the reaction is stopped so there is no heat generation. The reactor contains a liquid with physical properties that can be assumed as water. Ua =4.55 kW/K

C- In operation

1. During the reactor operation, the impeller is on and the heat of the reaction should be considered as an important parameter. The goal is to keep the reaction temperature at the desired value so the product with the desired yield can be obtained. Because the operating condition influences the U, you have been asked to come up with some correlation to see how U will change with changing the coolant rate and the impeller speed. Find the proper correlation to use for this vessel in order to estimate convective heat transfer inside the reactor and jacket.

Assume a number for the heat of the reaction, given that the reaction is saponification.

Note: Define all the parameters you will use, e.g. Equivalent diameter of the jacket, Jacket Reynolds number, Vessel Reynolds number, jacket height.

2. Estimate the overall heat transfer coefficient assuming that the jacket height is 2 m and the depth of the jacket is 2.5 cm. (All calculation needs to be done in SI, the coolant rate is 0.5 Liter/s)

3. Find out the relative ratio of the h _jacket/h _vessel as a function of impeller speed and graph it for a range of 50-250 rpm. The vessel temperature needs to be maintained at 50 C

Does the thickness of the vessel play a significant role in heat transfer?