Cooling cooking oil, how many power needed?

[ysh1317]

Hello again from Indonesia...
I need help calculating how much compressor power needed for conditions as follow:

1000 liter of vegetable oil, with base temperature of 100°C, need to bring the temperature down to 30°C within 5 minutes. The vegetable oil will be sitting still in a tank.

How much compressor power do I need to get to the desire temperature within the time frame?

Thanks in advance for any input, much appreciate it!

[xxargs]

1000 litre 100 degree C oil have same amount of heat as 200-250 litre of cooking water or around 1 kJ/litre, so is yes, you need a lot of cooling power.

1 kJ per litre and degree K Oil, * 50 degree K * 1000 litre oil = ~50 MJoule and 1/12 of hour give 50 MJ * 12 = 600 MJ/h or ~ 166 kW in needed cooling power


but question if you not can using cold water to cool down from 100 C to bit lower than 50 degree C and after using refrigerant process to take down to 30 degree C if you living i very hot climate and have hard find water below 20 degree C


Next problem is how take down 1000 liter of hot oil nearly instantly - even if you stir heavily and cool tanks wall very hard - i think not possible take down temperature to 30 degree in only 5 minutes and if you cooling tank wall to low temperature, oil can start to solidify/harden on cooled surface and slower heat release to the wall


third problem: is not easy in refrigerant process in on side of working space to expand refrigerant in 100 degree temperature and after this compress and cooling - compressor and head temperature going very hot in this case, and other side of working space handle ~25 degree C temperature and still efficient - is very big temperature gap to handle

---

So you need to thinking some solution as pumping hot oil trough heat exchange (cooled in part with water/coolant in opposite stream in heat exchanger, and last degree with heat exchange and cool-machine

or

make coil with many windings and almost filled the tank in volume with spaced windings and sink coil in tank (or permanent fit in tank) in time to cooling and put cooled water in coil from big cooled tank for fast cool down.

ie how fast you can cool down is very depend of active surface area per volume oil between hot oil and coolant and flow of coolant...

[Doug30293]

The calculations done by xxargs demonstrate that your oil cannot be cooled 70C in five minutes with a simple refrigeration system. You have some additional problems that make it impractical.

1. Oil has a terrible heat transfer coefficient and it gets worse as temperature drops. This is why plate heat exchangers and pumps are generally used for heating and cooling oils. Oil sitting still in a tank is not going to cool that quickly.

2. Oil is much more difficult to cool than to heat because its viscosity increases significantly at refrigeration temperatures. It forms a thermal barrier at the cooling surface preventing convective heat transfer.

You should probably rethink your process as the one you propose is not reasonably possible.

[sterl]

I would agree with Doug: from the portion we know, this is a cost prohibitive process....

That cubic meter of oil weighs about 910 Kg. The Cp is right around 2.1 kJ/(kG-Deg.C) and vairies according to the oil being used and with temperature: See....

http://www.clayton.k12.mo.us/cms/lib..._with_temp.pdf

so your heat to be removed totals 134000 kJ in 5-minutes: so the actual refrigeration load averaged over that 5-minutes is 134000*60/5*0.000277778 is 446 KW of average refrigeration as local effect, required. (2) things: you are starting with a very large temperature difference and obviously finishing smaller, thus your load is declining; and the load in the first 10-seconds is going to a whole lot larger than that; and the controls and separation capacity and condensing capacity on your refrigeration system are going to be overwhelmed.

SO: How much time is there between these batches of oil? And can you tolerate moving the oil from one tank to another? To make this work, you need to create a thermal storage which at the temperatures you are talking about might as well be water at say 5-deg. C. If this event happens once an hour and you exchange your heat with the single source of water, you can spend 55-minutes cooling it and heat it up over the 5-minutes in exchange with the pumped oil. If you want to be more energy efficient, use (2) water storages, one circulating to a cooling tower alone to make (say) 35-deg water over 55-minutes and one that you refrigerate to 5-deg C. You then have (2) heat exchangers in series and (2) sets of water pumps but both water tanks are smaller and the real refrigeration load is smaller. The whole process is then driven by the rise in temperature of the water so the heat exchanger selection gets considerably simpler. If this has to happen 4-times an hour, everything gets bigger but the basic premise remains the same.

Of course if those batches of hot oil are not all the same product and the oils cannot be mixed: the topic can get pretty pricey....