ok...here's the problem,..I can't s

[Purplehaze]

ok...here's the problem,..I can't seem to get my units
to equal out - I'm overlooking something:

Qt = F.Cp.(T1-T2)+ F.Jc.W2.Y + Qm + Qw

Qt: Total Energy (heat)
F: flow rate
Cp: specific heat of product
T1/T2: temperatures in and out
Jc: Latent heat of crystallization
W2: Solid fat content at exit (unitless)
Y: Fat Content of emulsion (unitless)
Qm: Energy transfer from shaft
Qw: Energy transfer from water

Your help is appreciated!!!

 

[IRstuff]

Your 1st term is troublesome, since the non-flow rate terms should already come out in Joules. which means that you are either trying to calculate and energy flow and are missing some time-related terms in the remainder or the flow rate term needs to be modified with something.

TTFN

 

[JOM]

You have 5 terms that must all have the same units. Qt on the left and the 4 terms on the right summed together.

I suggest you put down the units for everything - kg, kg/sec, and so on. What is "total energy" exactly - a heat transfer rate or an absolute energy measurement.

Should you be using heat capacity (kJ/kg-degree) instead of specific heat, which is dimensionless?
Cheers,
John.

 

[vtl]

Cp is usually the problem since they usually provide you with a Kilo unit

 

[MortenA]

you general equation is right

Now just make sure each constant and independant is in the same system and every thing should work out.

The only thing is: remember that fat and liquid may have different heat capacities and this should be considered for T_sp to T2

T_sp=temp of solification

Best Regards

Morten

 

[Purplehaze]

joules.............Qt: Total Energy (heat)
m/s................F: flow rate
joules/kg.Kelvin...Cp: specific heat of product
Kelvin.............T1/T2: temperatures in and out
J/kg...............Jc: Latent heat of crystallization
...................W2: Solid fat content at exit (unitless)
...................Y: Fat Content of emulsion (unitless)
joules.............Qm: Energy transfer from shaft
joules.............Qw: Energy transfer from water

To clarify, these are the units I am using for the equation - and it isn't working out....

 

[ardilesd]

A couple of problem:

Qs are expressed in energy units (joule) as if we model a non-flow system. But, on the other hand, you use F as a flow , so the inconsistency is between
energy terms (Qm. Qt, Qs) and power terms (F.cp... and F.Jc...)
So, please, express you heat as a flow (in watt or joule/hr or kcal / H ).
Adittionally, your F must be expressed in kg/hr , according to the units in Latent heat and heat capacity
Regards

 

[Purplehaze]

thanks 4 the help!