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I need to be able to cool down cooking oil quickly after using it in a countertop deep fryer- how can I do that safely?

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    possible duplicate of this – Hao Ye Dec 1 '15 at 21:15
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    I may have been over at Mechanics SE too much, but my immediate thought was rigging up a transmission cooler. – JPhi1618 Dec 1 '15 at 21:39
  • If you want to propose an answer, post it as an answer. – Cascabel Dec 2 '15 at 15:57
  • How much oil are you dealing with, and how quickly do you need to cool it? – Joe Dec 2 '15 at 16:12
  • As this question has come up before ... I wonder if there are any companies that make something that's effectively a double-ended heat sink? (put one end in the oil, the second out of the oil, and then put a fan across it, or use it to stir with). Although, cleaning it would kinda suck unless it's small enough to fit into a dish-washer ... and you had a grease trap. – Joe Dec 2 '15 at 16:16
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I think it would be reasonably safe to use something like an immersion wort chiller as used by homebrewers. The safety points to be aware of that spring to mind are:

  1. Make sure there is no way the cooling water can drip into your hot oil - test all pipe connections first
  2. The cooling water exiting the chiller will be very hot - make sure it can drain away safely
  3. The exit pipe of the chiller will also be very hot - take appropriate precautions when handling
  4. It is possible that the water in the chiller could actually boil. You probably don't want that to happen. Make sure the flow of water through the chiller is fast enough to prevent this. It's probably best to have the cooling water flowing before immersing the chiller in the hot oil.

You can purchase these from your local homebrew store, or purchase the copper pipe and suitable fittings from your local hardware store and build it yourself if you are so inclined.


Please note, I have not tried this out. If you want to try it, I would recommend the following in addition to the above safety notes:

  1. Attach a thermometer to the chiller outlet. Never let the temperature rise above 80 deg C
  2. Start with the maximum possible flow of water through the chiller before immersing the chiller. Immerse the chiller gradually - one coil at a time - checking the chiller outlet temperature all the time
  3. Hold the chiller by the water inlet and not the water outlet, for obvious reasons!
  4. If you can, route your output hot water to the nearest bathtub. Enjoy a nice hot bath afterwards while you enjoy your deep-fried treats ;-)
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    If your oil is hotter than the boiling point of water (which it is -- that's the whole point of deep-frying rather than boiling food), cooling it by transfering its heat to water sounds rather dangerous. – David Richerby Dec 2 '15 at 0:22
  • @DavidRicherby possibly - I wish I had a better handle the physics to calculate the feasibility of it. However I think it is worth noting most internal combustion engines are cooled with non-boiling, non-super-heated water and will have internal temperatures far in excess of fryer oil. I would imagine the average automotive cooling system has much higher overall energy transfer rate than would be required for the fryer, though of course it will have a higher coolant flow rate than may be achieved with domestic water supply and wort chiller. – Digital Trauma Dec 2 '15 at 5:52
  • Except within the combustion chamber and the exhaust manifold attached to it, engine blocks generally do not get that much hotter than boiling water (and less than hot oil in a deep fryer), and the conduits where the coolant flows through it are very heavy duty (basically, the block itself). I don't think your idea is that crazy though, as long as there's water actually flowing through the pipes and they are not sealed. – goldilocks Dec 2 '15 at 6:28
  • @goldilocks is right, and you wouldn't need much flow to stop the water boiing. I'd make sure the outlet was open to let any steam escape, and not pointing towards me. Oil has about half the specific heat capacity of water, but runs about twice as hot above room temp as the boiling point of water. The latent heat of vapourisation means the water needs a significant extra heat input to boil once it reaches 100C. If you immersed the coiils then put the water through you'd get a puff of steam at first then hot water. ... – Chris H Dec 2 '15 at 9:11
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    ... A volume of water comparable to the volume of oil would produce a significant temperature drop without (much) boiling, you might need ~10x as much water as oil to cool it to room temperature if you don't boil it (guesswork on the last point). My main concern would be the outlet water dripping into the oil. – Chris H Dec 2 '15 at 9:15
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You really can't. The best you can do is put some long stainless utensils in the oil to help dissipate heat, but it's still not going to be fast, just a little faster.

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    Maybe also blow cool air across to make the heat transfer through the utensils faster? (Pedantic note, there isn't really radiation here, it's conduction from oil to utensils and convection from utensils into air.) – Cascabel Dec 1 '15 at 19:08
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    Blowing cool air across the top of the container will also move away heated air, making the heat transfer from the oil to the air more efficient, I believe. Dunno if it will have a large efffect though. @Jefromi – eirikdaude Dec 1 '15 at 23:44
  • @eirikdaude But convection would do that pretty efficiently anyway. – David Richerby Dec 2 '15 at 0:20
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    @DavidRicherby Asked about this over at physics SE, and the effect of airflow seems significant from the answers I'm getting. – eirikdaude Dec 2 '15 at 6:23
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    Agreed, natural convection is much less efficient than forced convection. Just try cold windy weather versus cold still weather. Anyway, point is, "you can't" doesn't strike me as a very complete answer. – Cascabel Dec 2 '15 at 7:46
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The more surface, and the more cold thermal mass trying to keep that surface at a given temperature the more rapid the cooling - so if you pour the oil into a wide baking or frying pan sat on a concrete or steel slab (or even a cast iron hobplate),or propped up with good or even forced (fan - but i'd want a fan near hot oil like i'd want to immerse the bottom of that baking sheet in water....NOT) air circulation to the underside, it WILL cool more rapidly.

Alternatively, pouring it between two containers (or scooping up and pouring from a height) repeatedly will expose a large and changing surface area of the liquid to air, also giving you cooling.

All these assume you feel safe handling and pouring the hot oil, and that your deep fryer design allows safely doing so.

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The oil container has some excess capacity to accommodate the volume of the food you were cooking. You can use that and introduce something cold to the fryer. This can either be a heat-safe solid, like sturdy pieces of metal, or just excess cooking oil. Either one can be chilled thoroughly while you're cooking, then added to the fryer to accelerate cooling.

This won't instantly reduce the temperature to a safe level, but it will help. If you are really in a hurry and have freezer space to spare, you could repeatedly replace the cold metal until the temperature has dropped as much as you want. The metal, of course, will become quite hot initially. Be careful there.

Make sure whatever you're using stays as dry as possible: water will cause bubbling, just like it does when you're frying, and if you're deliberately raising the hot oil level to near the rim of the container, a spill could result.

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  • Adding blocks of metal will help very little. Metals have very low specific heat capacity, which means that they increase in temperature a lot when only a small amount of energy is put into them. So the metal block will just heat up rapidly to the temperature of the oil, without removing much energy from the oil and, therefore, without decreasing its temperature very much. – David Richerby Dec 2 '15 at 0:24
  • Sure, metal's not ideal for that reason, @DavidRicherby, but for safety, cleanliness, and conservation reasons, it may be the best available choice. Ice cubes or water would cool the oil faster; they'd also cause a dangerous situation. You could use some food -- which contains a lot of water -- but that's wasteful since it probably won't be edible (or at least palatable) afterwards. You're limited in the amount of cold oil you can add; pieces of something can be removed and replaced with new cold something else. – jscs Dec 2 '15 at 2:36
  • Well, a convenient example of a block of metal is another pan. If you poured hot oil from one pan to another, I wouldn't expect it to cool very much at all. As such, adding metal isn't much better than just waiting, so probably isn't worth doing at all. And, honestly, ice cubes? Water? "A dangerous situation"? "Dangerous" implies some kind of risk; adding water to hot oil is guaranteed to produce serious injury. Sure, you say don't do it but I don't understand why you even mentioned it. I mean, sure, you could try to cool the oil by sticking your head in it, too... – David Richerby Dec 2 '15 at 8:03
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You'd have to let your oil cool down to 212 degrees F (100 degrees C) first, but you could use the following technique to get it the rest of the way down to room temperature after that:

When I want to quickly cool down stock (for food safety reasons), one of the tricks I often use is to get a container larger than the one containing the hot liquid, and fill it with ice water. This technique would also work for oil, but in this case you need to be very careful to make sure that the container the oil is in isn't hot enough to cause the water to spatter into the oil (hot oil and water are extraordinarily dangerous together), isn't anywhere near full, and that the shape and size of the containers is such that the hot container will not have any chance of tipping over as the ice melts (you don't want the oil container tipping over and spilling hot oil into the water). One way to do this is to put just water in the larger container and then put ice in the area surrounding the sides of the oil container. The water will help conduct the heat even from the underside of the oil container into the ice.

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Turn the heat off and wait. There are no safe alternatives.

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