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heat object with fluid

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ymehdi

ymehdi

Mechanical
Jan 30, 2020
12
hi,
how would i calculate heating up an object with oil?
the temperature of the oil is 100 degrees
the object mass is 48.40kg
temp to reach 100 degrees
starting temp of object is 50 degrees
oil is going through object so full contact
 
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sorry forgot to include that in
volume of object is 361mm*361mm*50mm =0.00651605m3
density of material is 7850 kgs/m3
specific heat of material is 0.49kj/kg

i dont know whats the thermal conductivity
 
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I think that you could calculate this using lumped capacitance method. It's described for example in "Fundamentals of Heat and Mass Transfer" book by Incropera.
 
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whats lumped capacitance meathod?
and also the the oil is travelling within the metal block
 
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yhemdi,

This is a transient simulation and hence is ill suited to a calculation, though the paper linked to by IR stuff has a good try.

However depending on how accurate you need to be you can work on some assumptions.

The metal will need a certain amount of heat energy to go from 50 to 100C
This heat energy is supplied by the oil, but at an unknown rate.
What do you mean by "full contact?"

Your unknowns:
How much heat is lost by the outside of your block to air / other losses. Again a temperature dependant thing as the hotter it gets the greater the losses.
Unless this block is heavily insulated

Heat transfer rate and oil flow. You say nothing about oil flow rate. It has be be big enough that it's exit temperature is close to the inlet temperature for simple calculations to work.

So work or estimate some of those and you might get close.

As said if the oil temp is 100 and your target temp is a 100 you will get to 97 or98 but to get to 100 will take a loooooong time. Maybe better to have at least 10C difference between oil temp and desired block temperature

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Oh, from your other posts, I thought the object was immersed in the oil, not that the oil is flowing through it, presumably, like coolant in an engine.

So, yes, if there's ANY loss of heat to the ambient or elsewhere, you will never reach 100C everywhere in your "object"

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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I also thought that the object is immersed in oil. Lumped capacitance method can be used for pipe (cylinder) with oil flowing inside (this example is even solved in aforementioned book). However, I'm afraid that for a block it will be much more difficult (if at all possible). Thus I would use numerical simulation to solve this problem.
 
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Ok

for this experiment we will be calculating with no loss

and depending on the temperature of the oil it can flow around 49-47 L/min

its acts as radiator as you say fluid goes in circulates around and then goes out however its a solid block not just tubing and fins

if the oil flowing at 110 degrees ( we dont count the time for oil to heat up to temp) and is flowing in the metal block can we not use temp of oil and just the mass of the object to work out time to heat up or can we not do this as its a fluid heat up a solid and not a solid heating up another solid?

thank you for everyone help i appreciate it :)
 
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So, I don't get this task that you volunteered to do, with, seemingly, no coursework in heat transfer, and, seemingly, the lack of desire to crank through your own resources, or the links we've provided.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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I have not read all the posts so I am assuming that the oil temperature remains the same when the object is immersed in the oil bath. To keep the oil at a constant temperature, a heating source is required so you should then know the value of the heat input to the oil bath. the amount of heat absorbed by the block will then be equal to the heat input to the oil bath and we are discounting all heat losses to the environment. So far for equation, we have:
Qin= M*Cp*dT/Dt; Qin (but/hr),M (lbm of block), Cp (Btu/(Lbm-dF),dT/dt (rate of rise the object temperature in degrees F/time element be it sec,min,hr)
All units are in the English system and it's up to you to convert into the Metric units. The equation that I presented is emendable to a spread sheet. You could also use integration for a solution. I would use both as a mean to determine accuracy.
 
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Instead if the Cp specific heat at constant pressure use the Cv which is the specific heat at constant volume since the item immersed in the oil bath is incompressible.
 
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