Efficient Pump Usage in Fuel Oil Supply System: Solving for Tank Fill Time

[Girn261]

Homework Statement

A fuel oil supply system consists of two tanks (Tank A and Tank B) and two transfer pumps (Pump A and Pump B) to supply a Bunker C fuel oil to a heating boiler.

Pump A can fill up a Tank A from the minimum level in 15 hours and 20 minutes
Pump B can fill up a Tank B from the minimum level in 17 hours and 30 minutes

Calculate the time to fill up Tank A from the minimum level under the following conditions.

a) both pumps are used simultaneously
b) pump A is used to fill up Tank A while Pump B is transferring fuel out from Tank A to Tank B

Homework Equations

The Attempt at a Solution

for part a) I converted the hours to minutes for both pumps, I assume both tanks to be same size. Pump A = 920mins to fill tank & 1050 mins for pump B. Then I did (1/920+1/1050)x(t)=1 to find t which was 490 mins. But for part B any tips? I'm having a brain fart.

 

[haruspex]

for part B any tips?

Consider what the change is over one minute.

 

[rude man]

Are the two tanks the same volume? Or are the two pumps of equal capacity? Neither? If neither seems like not enough info given.

 

[Girn261]

Consider what the change is over one minute.

Okay I am kinda lost haha. But I did this (1/1050-1/920)=1/x and for x I got 7430 mins. Is that right?

 

[Girn261]

Are the two tanks the same volume? Or are the two pumps of equal capacity? Neither? If neither seems like not enough info given.

thats the exact question, so I think you're suppose to assume the tanks are same volume, while the pumps are different capacity

 

[haruspex]

Okay I am kinda lost haha. But I did this (1/1050-1/920)=1/x and for x I got 7430 mins. Is that right?

Yes.

 

[rude man]

thats the exact question, so I think you're suppose to assume the tanks are same volume, while the pumps are different capacity

Well, I think it's exactly badly phrased, but OK you have to assume something, might as well be equal-size tanks..