3 replies to this topic

[emd.franz]

Hi Everyone! 

 

I am currently working as Plant Engineer in an Edible Oil Refining Plant. We are working on a trial run for our Cooling Water Pump which was increased from 38 m³/hr to 45 m³/hr. As seen in the image the said pump was supplying on 2 plate heat exchangers. We are aiming to cool down the oil at PHE #1 to 50^oc. - 55^oc. I am using

 

Qoil=Qwater or

Mcp(t_in-t_out)=Mcp(t_out-t_in)

 

M oil         = 5.06kg/hr

M water    = to be determined

cp Oil       = 2.179 kj/kg-^oc

cp water   = 4.18   kj/kg-^oc

 

which resulted to ~25 m³/hr of cooling water. 

 

My question is, is there other computation which I can use in this problem?

My aim is to know the amount of water used in cooling the oil @ PHE #1 ( and right now we dont have the flow meter to be installed in the cooling line). I have tried Bernoulli's equation but the difference between the two velocity doesn't seem right.

 

Please see my attached image. (and sorry for the handwriting  )

 

I will be very pleased for any comments/ suggestions and advice.

 

Thanks.

 

-Franz

 

 

Attached Files

•  cooling data.jpg   67.73KB   2 downloads

[breizh]

Franz

 

You need flow meter , at least one on the water side . You might consider to ask a 3rd party to perform the flow rate measurement using a non intrusive flow meter (Doppler effect) .

 

My 2 cents 

Breizh

[katmar]

If you confirm that the flowrates are correct, as suggested by Breizh then the problem could be that you do not have enough heat transfer surface in the exchangers.  Your calculation shows what the mass flow requirement would be if all the heat is transferred, but it may be that at 25m³/h the heat transfer coefficient (and therefore the area) is too low to transfer this heat.  Increasing the flow rate of the water will increase your LMTD and the heat transfer coefficient. You can check this by measuring the actual temperature changes across the heat exchangers.  If the temperatures you have marked on your drawing are correct then your flow rates need to be checked.

[emd.franz]

Sir Breizh,

 

I am now considering your advice. We are looking for the service in the nearest supplier.

 

Sir katmar,

 

I agree. I think with the computations I used, Qin=Qout, I have disregarded the coefficient of the plates, and efficiency of the system. This is why I have a doubt that I achieved the correct answer from my computation.