The Physics of Hot Pockets

StartsWithABang (3485481) writes "You've all had the experience: you're all excited to microwave your favorite snack. So you pull it out of the freezer, you throw it in, and you let it rip. A minute or two later, you pull it out, and there it is: boiling on the outside, frozen in the middle. Finally, a physicist answers the eternal question: why do microwaved foods remain frozen on the inside when they reach scalding temperatures on the outskirts? Starts With A Bang explains the whole phenomenon. Bonus for the crisping sleeve explanation!"

Comments

Microwave trays

[Travis Mansbridge]

Also those with rotating microwave trays (because microwaves tend to heat unevenly) ought to be aware that anything at the center of the tray will not get the benefit of rotation and heat at the same rate the entire time. To roll around in a (relatively) even distribution, none of your food should sit in the center of the tray.

Re:Microwave trays

[Anonymous Coward]

Of course there are microwaves made with competent stirrers and well-placed feeds. Panasonic makes microwave ovens that feature both (the feed is at the bottom of the cavity), so no rotation is necessary. They also use variable fast pulse width modulation to drive the magnetron, resulting in a smooth output power, thus avoiding another common contribution made by on-off duty cycles to burnt skin / frozen middle problems especially at lower power settings. (Triac controlled magnetrons can only go on and off; most PWM microwave ovens not driven by an inverter supply do a cycle on the order of 30 seconds.) There is work on continuous phase shifting, which will avoid heating the same islands in food even in pessimal cases (like poorly conducting food put in the centre of a rotating tray). Finally, there is still substantial research going into probes inserted into food so as to provide feedback to the driver logic (dynamically or for capture into programs which take food type mass as variables) and whether non-invasive probes can provide useful dynamic feedback every time the oven is in use.

The main problem is that the cheapest microwave ovens are just good enough to follow recipes that call for some number of seconds on the high setting while being unreliable at other settings, and the food industry targets its instructions accordingly. This is a global problem, not unique to the USA. However, as large-cavity combination microwave/grill/convection ovens become more popular in densely populated areas (why waste space having two or three ovens? why not coat your microwave with pyrolytic surfaces that you clean by simply baking or roasting something? why not cook with microwaves and brown with the grill simultaneously?) this is likely to change faster than patents expire, especially as several key manufacturers (Panasonic, GE) will not be cannibalizing conventional oven products. The critical path and most visible extra cost to the first time buyer is mainly in the design of trays and dishes which work well under arbitrary conditions in a combo oven, and avoiding damage when someone uses the wrong tray, dish or tool for a given programme.

Somebody needs to buy...

[Bin_jammin]

a microwave with more than 300 watts of power. I've never had the issue of hot outside/cold inside, my problems have always been of the hot outside/nuclear inferno/solar coronal mass ejection on the inside variety, regardless of where I've microwaved them. I don't even follow the instructions on the package very closely, just pull it out of the wrapper, put it in the sleeve, toss it in, slap the door shut, 3 or so minutes, and out comes an external breading hot to the touch with napalm in the center. Maybe there are just a lot of broken microwaves, or even more likely, people that don't know how to use them properly?

Re:Somebody needs to buy...

[war4peace]

How to microwave popcorn:
Put the bag in, turn microwave on. When number of pops/second goes down to 1, stop, pull bag out, enjoy results.

Re:Somebody needs to buy...

[NotDrWho]

Fuck it. Too much work. I'll just eat this tube of cake frosting instead.

Seriously.

[adolf]

I've never had a problem with Hot Pockets: Follow directions, learn how it works in a given microwave oven, and...done: Ridiculously-hot cheap, bubbly, unhealthy goodness.

Meanwhile, I don't need to read TFA to learn how the powdered aluminum wrapper turns RF energy into thermal energy. And I don't need TFA to know that any thing has a certain reluctance toward changing temperatures, as nothing is a perfect thermal conductor.

In fact: Dude, I've been cooking with a microwave since I was a little kid: It was the first kitchen appliance I was certified on other than -- maybe -- an electric can opener.

Up next on /.: How shoelaces work to keep our shoes on our feet, followed by a lesson in using a light switch to illuminate a dark room. Or "Toast: Why bread is caramelized only on the outside when using the every-day toaster."

*head in hands*

It's on purpose

[Rosco P. Coltrane]

Scalding on the outside and frozen inside is a feature: it's the Hot Pocket's way of telling you it really isn't proper nutrition.