American Institute of Physics: The problem with microwaving tea

5 Aug

The United Kingdom Tea Council has some fascinating facts about the history of tea in The History of Tea:

Tea is so much a part of everyday life in Britain that we might never stop to think about how a unique plant from faraway China became the nation´s favourite drink. But the history of tea is fascinating, and in this section we can follow its story from the earliest times in Imperial China right up to its present place at the heart of British life.

Read about the exotic beginnings of tea in China and the Far East and in time how it was transported to the UK and America on the Tea Clippers.

Discover how tea was brought to England by a seventeenth century queen, and how important the tea trade was to the British East India Company, one of the most powerful commercial organisations the world has ever seen.

Learn how the phenomenal popularity of tea in the eighteenth century led to widespread smuggling and adulteration, and about the murderous lengths smugglers went to to protect their illegal trade.

Read also about the Boston Tea Party of 1773, which sparked off the American Revolution, and how rivalry between the English and the American tea traders in the nineteenth century led to the excitement of the Clipper races. And trace the social history of tea in Britain, from the early debates about its health-giving properties, to the rise of the tea bag, via the great tradition of the London Tea Auction and the role of tea in boosting morale in the World Wars. http://www.tea.co.uk/history-of-tea

Here is a bit about the history of tea:

The birth of tea in China

Tea is often thought of as being a quintessentially British drink, and we have been drinking it for over 350 years. But in fact the history of tea goes much further back.

The story of tea begins in China. According to legend, in 2737 BC, the Chinese emperor Shen Nung was sitting beneath a tree while his servant boiled drinking water, when some leaves from the tree blew into the water. Shen Nung, a renowned herbalist, decided to try the infusion that his servant had accidentally created. The tree was a Camellia sinensis, and the resulting drink was what we now call tea.

tea was first introduced to Japan, by Japanese Buddhist monks

It is impossible to know whether there is any truth in this story. But tea drinking certainly became establishedin China manycenturies before it had even been heard of in the west. Containers for tea have been found in tombs dating from the Han dynasty(206 BC – 220 AD) but it was under the Tang dynasty (618-906 AD), that tea became firmly established as the national drink of China. It became such a favourite that during the late eighth century a writer called Lu Yu wrote the first book entirely about tea, the Ch’a Ching, or Tea Classic. It was shortly after this that tea was first introduced to Japan, by Japanese Buddhist monks who had travelled to China to study. Tea drinking has become a vital part of Japanese culture, as seen in the development of the Tea Ceremony, which may be rooted in the rituals described in the Ch’a Ching.

The growth of tea in Europe

So at this stage in the history of tea, Europe was rather lagging behind. In the latter half of the sixteenth century there are the first brief mentions of tea as a drink among Europeans. These are mostly from Portuguese who were living in the East as traders and missionaries. But although some of these individuals may have brought back samples of tea to their native country, it was not the Portuguese who were the first to ship back tea as a commercial import. This was done by the Dutch, who in the last years of the sixteenth century began to encroach on Portuguese trading routes in the East. By the turn of the century they had established a trading post on the island of Java, and it was via Java that in 1606 the first consignment of tea was shipped from China to Holland. Tea soon became a fashionable drink among the Dutch, and from there spread to other countries in continental western Europe, but because of its high price it remained a drink for the wealthy…. http://www.tea.co.uk/tea-a-brief-history-of-the-nations-favourite-beverage

See, Types of Teas and Their Health Benefits                      http://www.webmd.com/diet/features/tea-types-and-their-health-benefits

Science Daily reported in The problem with microwaving tea: Why microwaving liquids is different from other heating techniques, and how this issue can be resolved:

Tea drinkers have been saying it for years. Water heated in a microwave just isn’t the same.

Typically, when a liquid is being warmed, the heating source — a stove, for example — heats the container from below. By a process called convection, as the liquid toward the bottom of the container warms up, it becomes less dense and moves to the top, allowing a cooler section of the liquid to contact the source. This ultimately results in a uniform temperature throughout the glass.

Inside a microwave, however, the electric field acting as the heating source exists everywhere. Because the entire glass itself is also warming up, the convection process does not occur, and the liquid at the top of the container ends up being much hotter than the liquid at the bottom.

A team of researchers from the University of Electronic Science & Technology of China studied this nonuniform heating behavior and presents a solution to this common problem in the journal AIP Advances, from AIP Publishing.

By designing a silver plating to go along the rim of a glass, the group was able to shield the effects of the microwave at the surface of the liquid. The silver acts as a guide for the waves, reducing the electric field at the top and effectively blocking the heating. This creates a convection process similar to traditional approaches, resulting in a more uniform temperature.

Placing silver in the microwave may seem like a dangerous idea, but similar metal structures with finely tuned geometry to avoid ignition have already been safely used for microwave steam pots and rice cookers.

“After carefully designing the metal structure at the appropriate size, the metal edge, which is prone to ignition, is located at weak field strength, where it can completely avoid ignition, so it is still safe,” said Baoqing Zeng, one of the authors on the paper and professor of electronic science and engineering at UESTC.

Solids don’t undergo convection, so getting your leftovers to warm up uniformly is a completely different challenge….                                                                                                                                      https://www.sciencedaily.com/releases/2020/08/200804111516.htm

Citation:

The problem with microwaving tea

Why microwaving liquids is different from other heating techniques, and how this issue can be resolved

Date:        August 4, 2020

Source:     American Institute of Physics

Summary:

Through convection, as the liquid toward the bottom of a container warms up, it becomes less dense and moves to the top, allowing a cooler section of the liquid to contact the heating source. This ultimately results in a uniform temperature. Inside a microwave, however, the electric field acting as the heating source exists everywhere and the convection process does not occur.

Journal Reference:

Peiyang Zhao, Weiwei Gan, Chuanqi Feng, Zhongxing Qu, Jianlong Liu, Zhe Wu, Yubin Gong, Baoqing Zeng. Multiphysics analysis for unusual heat convection in microwave heating liquidAIP Advances, 2020; 10 (8): 085201 DOI: 10.1063/5.0013295

Here is the press release from the American Institute of Physics:

NEWS RELEASE 4-AUG-2020

The problem with microwaving tea

Why microwaving liquids is different from other heating techniques, and how this issue can be resolved

AMERICAN INSTITUTE OF PHYSICS

WASHINGTON, August 4, 2020 — Tea drinkers have been saying it for years. Water heated in a microwave just isn’t the same.

Typically, when a liquid is being warmed, the heating source — a stove, for example — heats the container from below. By a process called convection, as the liquid toward the bottom of the container warms up, it becomes less dense and moves to the top, allowing a cooler section of the liquid to contact the source. This ultimately results in a uniform temperature throughout the glass.

Inside a microwave, however, the electric field acting as the heating source exists everywhere. Because the entire glass itself is also warming up, the convection process does not occur, and the liquid at the top of the container ends up being much hotter than the liquid at the bottom.

A team of researchers from the University of Electronic Science & Technology of China studied this nonuniform heating behavior and presents a solution to this common problem in the journal AIP Advances, from AIP Publishing.

By designing a silver plating to go along the rim of a glass, the group was able to shield the effects of the microwave at the surface of the liquid. The silver acts as a guide for the waves, reducing the electric field at the top and effectively blocking the heating. This creates a convection process similar to traditional approaches, resulting in a more uniform temperature.

Placing silver in the microwave may seem like a dangerous idea, but similar metal structures with finely tuned geometry to avoid ignition have already been safely used for microwave steam pots and rice cookers.

“After carefully designing the metal structure at the appropriate size, the metal edge, which is prone to ignition, is located at weak field strength, where it can completely avoid ignition, so it is still safe,” said Baoqing Zeng, one of the authors on the paper and professor of electronic science and engineering at UESTC.

Solids don’t undergo convection, so getting your leftovers to warm up uniformly is a completely different challenge.

“For solids, there is no simple way to design a bowl or plate in order to achieve a much better heating result,” Zeng said. “We can change the field distribution, but the change is very small, so the improvement is limited.”

The group is considering other ways to improve nonuniformity in solid foods, but the methods are currently too expensive for practical use. For now, they’re focusing their efforts on working with a microwave manufacturer to commercialize their microwave accessories for liquids.

A future in which tea can be microwaved without ridicule may not be too far away.

###

The article, “Multiphysics analysis for unusual heat convection in microwave heating liquid,” is authored by Peiyang Zhao, Weiwei Gan, Chuanqi Feng, Zongxing Qu, Jianlong Liu, Zhe Wu, Yubin Gong and Baoqing Zeng. The article will appear in AIP Advances on Aug. 4, 2020 (DOI: 10.1063/5.0013295). After that date, it can be accessed at http://aip.scitation.org/doi/full/10.1063/5.0013295.

ABOUT THE JOURNAL

AIP Advances is an open access journal publishing in all areas of physical sciences–applied, theoretical, and experimental. The inclusive scope of AIP Advances makes it an essential outlet for scientists across the physical sciences. See https://aip.scitation.org/journal/adv.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

Heathline listed the benefits of drinking tea in 10 Evidence-Based Benefits of Green Tea:

  1. Contains healthy bioactive compounds
  2. May improve brain function
  3. Increases fat burning
  4. Antioxidants may lower the risk of some cancers
  5. May protect the brain from aging
  6. May reduce bad breath
  7. May help prevent type 2 diabetes
  8. May help prevent cardiovascular disease
  9. May help you lose weight
  10. May help you live longer

https://www.healthline.com/nutrition/top-10-evidence-based-health-benefits-of-green-tea#13

Resources:

12 Research-Backed Health Benefits Of Black Tea                                                                           https://www.organicfacts.net/health-benefits/beverage/health-benefits-of-black-tea.html

18 Benefits Of Drinking Tea Everyday                                                                                         https://www.beautytohealth.com/18-benefits-drinking-tea-everyday/

25 Surprising Health Benefits Of Tea                                                                                              https://www.organicfacts.net/tea.html

Where information leads to Hope. © Dr. Wilda.com

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