# How was the reactor length determined here?

• hpc2016
In summary: The water flow is also regulated to equalize the radiation dosage at all points along the reactor length.

#### hpc2016

I've recently been reading this paper (a free version is available here).

I've been trying to work out how they came to the 128m length, but I just can't. Feel like it's been just beyond my grasp for a long time and it's been driving me mad. Any help would be appreciated.

Thanks in advance.

The system is designed so that all parcels of water passing through the reactor receive the same dose of uv radiation to kill bacteria. Since the solar radiation rate is highest at mid-day, and falls off toward early morning or late afternoon, the flow rate of water through the reactor is highest at mid-day, and is less earlier in the day and later in the day. The diameter and length of the pipe are chosen so that the total dosage at any time during the day is sufficient to kill the bacteria (down to a desired level). At night, the water flow rate is, of course, zero. There are surge tanks at the exit of the reactor to allow for the variable flow rate in conjunction with the variable demand times.

hpc2016
Thanks for your reply.

I think I should have been more precise in my original question. The system makes sense to me conceptually, what I don't understand is why the length is 128m and not, for example, 200m or 100m. The maths of it is the part I'm struggling with, I think.

So, your question really is "how does one go about quantitatively designing a tubular continuous flow chemical reactor to achieve a desired product concentration in the exit stream, given the flow rate through the reactor?"

Yes, also given the inactivation constant, the pipe diameter and the initial water quality.

hpc2016 said:
Yes, also given the inactivation constant, the pipe diameter and the initial water quality.
OK. I can't give you every last detail because they don't provide all the details. But, it goes something like this. Each parcel of fluid passing through the reactor has to receive a certain minimum solar UV radiation dosage. To do this, they vary the water flow rate so that, as the solar flux decreases, the flow rate also decreases in proportion. There is going to be a certain minimum value of the total pipe volume and surface area necessary to achieve the desired cumulative radiation dosage over all radiation conditions and associated flow rates. This determines the design of the reactor.

mheslep and hpc2016

## 1. How was the reactor length determined?

The reactor length was determined through a series of calculations and simulations based on the desired output and the physical properties of the reactor components.

## 2. What factors were considered in determining the reactor length?

Factors such as the desired reaction rate, reactant concentrations, temperature, pressure, and flow rate were all taken into account when determining the reactor length.

## 3. Why is the reactor length important?

The reactor length is important because it directly affects the efficiency and effectiveness of the reaction taking place. A properly sized reactor length ensures optimal conversion of reactants into products.

## 4. Can the reactor length be adjusted or changed?

Yes, the reactor length can be adjusted or changed to optimize the reaction conditions or to accommodate changes in the process.

## 5. Is there a standard method for determining reactor length?

There is no one standard method for determining reactor length as it depends on the specific reaction and process conditions. However, there are various mathematical models and software programs that can aid in the determination of reactor length.