I don’t think that is the case. A stratified fluid, in the absence of continued energy exchange with the outside environment, will eventually reach a homogenous temperature distribution due to diffusion.
That said, even if you are were correct, in the context of brewing tea we would only have a few minutes of brew time in which the stratification would have an impact on the extraction.
In many ways, we have been. The average person has casual access to goods and services that would have been immensely inaccessible without industrialization. Consider the average car for example. The engine alone has hundreds of tightly toleranced parts working in a mechanical dance to harness thousands of controlled explosions per second. That doesn’t even touch on the complex support systems required for engine management or chassis/suspension. I can buy a well running used car for less than the cost of a month’s rent.
Compare that to the pre-industrial era, when a simple shirt would have taken a single person 500-600 hours in manual labor to make starting from raw wool. That’s more than three months’ work with a 40 hour work week.
It’s truly amazing that any minimum wage worker in the USA can buy multiple used cars, a monumentally complex piece of machinery by any historical standard, for less labor than it would take to get a new shirt a few hundred years ago.
That said, I do believe we have the capacity to get these benefits PLUS reduced work hours. We will see that when we demand better worker protections from lawmakers and stop equating a human’s value to society with the number of hours they work each week.
We have had ultra-rich people and major wealth inequality for most of American history. Rockefeller (1838-1937) amassed a fortune in the 1800s in excess of $400B inflation adjusted dollars. By most measures, he was the richest American of all time.
The second richest American of all time is up for debate but contenders include Andrew Carnegie (1835-1919), Cornelius Vanderbilt (1794-1877), Henry Ford (1863-1947), or Bill Gates (1955-present).
Wealth inequality has obviously grown over the past 50 years but it’s worth noting that wealth inequality in general is not a uniquely modern problem. It is also exaggerated by comparing to the 1970s, where wealth inequality was at a historical low point (see graph below)
Search the literature for thermal stratification. There are many contexts where it is used outside of lakes and other large bodies of water, many of which do not consist of three distinct layers. Hell, the paper I cited SPECIFICALLY refers to the temperature gradient in the microwaved glass as “stratification”.
If you can’t understand the use of a term outside your specific area of expertise then thats honestly a you problem and that’s all I can say on that.
If the heating methods were as similar as you say, there wouldn’t be hundreds of publications accepted to various journals across the past two decades investigating the problem where microwaves produce a strong temperature gradient between the top and bottom of a body of liquid. It’s a well known process control problem.
That's not really showing temperature stratification which is a more extreme separation of temperature from surface
I think the definition you are using is far too restrictive, in many contexts temperature stratification simply refers to a situation where you get temperature gradients across a fluid with the warmer fluid gathered near the top of the body. For example, in a factory you will often have “destratification” fans operating because warm air from equipment rising to the ceiling results in a temperature gradient from floor the ceiling.
It is not a phenomena exclusive to surface heating.
That's just showing that the hottest atoms gather to the top, which btw, proves Convection currents.
Yes. My point was not to establish that convection is magically absent from fluids in microwaves, but to establish that it differs significantly from stovetop heating. Convection currents in stovetop heating create a strong stirring action that produces a substantially uniform temperature. Microwaves do not create the same stirring action and this produce a significant nonuniform temperature gradient.
The modified glass is just diverting the hotpots to the bottom to make the convection less "unusual".
Clearly. They make the heating more akin to a stovetop, which is really the point here.
They aren't claiming that convection doesn't accrue, only that it's "unusual convection" resulting in less even heating like that of thermal stratification, not literal thermal stratification where the layers have separate convection currents that prevent mixing all together.
Once again, you are using a definition of thermal stratification that is far too specific. However, arguing over it is really just being pedantic because the core point at issue here is whether or not heating a cup in a microwave or a stovetop produce the same final product. They do not unless you apply some mechanical agitation to mix it up.
I'm well aware of temperature stratification. It doesn't happen in a microwave.
It empirically does. We can argue about the theory all day but the research says microwaves produce stratified temperature gradients when heating liquids. However, I’d point out that, in atmosphere, when we have localized hot spots the warm air can effectively travel in bubbles without significant mixing for quite some distance. There seems to be a similar phenomena at work when microwaving liquids.
See the screenshot below.
I pulled this from “Multiphysics analysis for unusual heat convection in microwave heating liquid” published in 2020 in AIP Advances.
Relevant excerpts:
“ Usually, the fluidity of liquids is considered to make the temperature field uniform, when it is heated, because of the heat convection, but there is something different when microwave heating. The temperature of the top is always the highest in the liquid when heated by microwaves.”
“ The experimental results show that when the modified glass cup with 7 cm metal coating is used to heat water in a microwave oven, the temperature difference between the upper and lower parts of the water is reduced from 7.8 °C to 0.5 °C.”
“According to the feedback from Midea (microwave appliance makers), when users use the microwave oven to heat liquids such as milk or water, the temperature at the top of the liquid will be significantly higher than the temperature at the bottom.”
I mean, it’s not really a matter of debate TBH. There are a number of peer reviewed journal articles documenting the temperature stratification. Here is one source, where the authors attempt to create a special cup to heat the water more evenly.
From a utility side perspective it’s true to say 240v is the standard we just wire our outlets to use one of the two hot wires instead of both of them.
Convection currents don’t stir water in a microwave because the heat source isn’t on the bottom. That’s the difference. You get temperature stratified water where the surface is hotter than the bottom of the cup and they don’t naturally mix.
Of course, here in America, we have this incredible technology called a spoon. Pull that bad boy out, give a little stir, problem solved.
It does, because the center of gravity isn’t hanging out on the end of a big lever. Have you ever handled a legitimately well made European style sword in real life?
They feel much lighter than you might expect.
@nBodyProblem
@lemmy.world