Answer:
Flow rate 2.34 m3/s
Diameter 0.754 m
Explanation:
Assuming steady flow, the volume flow rate along the pipe will always be constant, and equals to the product of flow speed and cross-section area.
The area at the well head is

So the volume flow rate along the pipe is

We can use the similar logic to find the cross-section area at the refinery

The radius of the pipe at the refinery is:



So the diameter is twice the radius = 0.38*2 = 0.754m
The definition of a scale of 1: 166 will mean that the scale of 1 in the model will be equivalent to 166 times the measurement in the real model, therefore we will have that the height would be 166 times smaller than the 179m given:

The same for the diameter,

The volume of a cylinder is given as




Therefore the volume would be 
I think u can say thats a constant velocity, but remember if ur turning, or going around a curve, that is also changing velocity. Hope this helps have a great day!