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The project "Glass". Energy Efficiency Disposable Tea / Coffee Cups


2020 year. It seems to be March 12th. Top-secret laboratory of the Research Institute of Heat and Cold (NIITiHo). Somewhere in the suburbs.

- Comrades! - the head of the laboratory triumphantly raised his fist to the ceiling and looked fervently at the recently awakened engineers and laboratory assistants.

The partially filled and battered assembly hall of the institute sluggishly drilled in response.

“This morning I gathered you for one very important announcement.” Firstly, the distance between you at work should be at least! I repeat, NOT LESS! One meter. How will you ensure this - think you are engineers.

The thought went into the masses, causing a slight laugh and timid disapproval.

- One more thing. The country needs a test of disposable cups, because this is the most hygienic way to consume high-degree drinks such as coffee, tea, chicory vodka and others. Currently, there is a struggle with you know what virus and the use of disposable items is an important component of protection against viruses and ... uh ... other diseases. As soon as you complete the experimental part of the study, the results can be processed remotely, at home. Go!

Engineers reached out trying to maintain a distance of 1 m. It was very similar to the movement of gas molecules in a closed vessel. The most responsible people tried to keep the necessary distance and shoved those who climbed into their meter range. Those who did not care (do not care) stubbornly poked at their colleagues and tried to get out of this hell through the doors of the main entrance. A pair of laboratory assistants, hooting cheerfully, pushed those who tried to keep their distance. Not many managed to get out of this mess. The last one stood weak and looked sadly at what was happening. He knew about another door that led out to the neighboring corridor, but, by a lucky chance, was near the main entrance. The last three employees from the audience got out closer to dinner.


Introduction


So, many of us can not live a day (especially in the autumn-winter-spring time) without having to drink a glass of coffee or tea, but rather a few. Especially when we are at work and there is no time to have a bite - tea / coffee really helps, but at the same time it warms and increases the level of vitality. Most often, disposable cups, thermomugs (energy-efficient thing!) And various reusable mugs / cups are used for this. But at what point is it better to drink such drinks and not get burned? And how to keep them at a temperature optimal for drinking longer? We tried to answer these questions in our study. Today we will try for strength disposable cups.



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When tea / coffee is poured into a glass, it is still impossible to drink it. Someone has evolved in such a way that he already knows how to do it, but he still will not be able to drink the main volume of the cup at such a temperature of the liquid, because you can get seriously burned. For most people, you have to wait N minutes to start drinking this drink. The value of time N is often known to us only empirically, that is, on the basis of previously obtained burns of the tongue, mouth and throat. In this case, the conditions for filling, moving and consuming the contents of the cups change each time, which means that the temperature of the liquid inside the cup also changes.

Upon reaching a certain boundary temperature T xtea / coffee can already be started to drink gently in small sips, so as not to burn yourself. But this temperature indecently quickly drops (if we suddenly use a thermo mug, then we have a little more time) and we remain with a half empty (full) mug of an already barely warm drink (someone might like this option).


Tasks to solve the problem


1. Describe the life path of tea / coffee in a cup (philosophical task).

2. Determine the temperature (temperature range) at which tea / coffee can already be drunk ( T x ) and can no longer be drunk ( T y ).
Yes, each has its own temperature limits
[ / . – , ]


3. Test various types of popular disposable cups and the cooling time of hot drinks in them. Make a rating of their energy efficiency. Calculate how long it takes to reach T x and T y .

4. How to reduce the time N waiting temperature T x ?

5. How to keep the temperature (thermal energy) in the range T x –T y for as long as possible?

Let's try to imagine the life path of a hot drink in a glass. The result is approximately the following:



A, if by points:

1. Preparation of the necessary ingredients and utensils. Water is most often used at a boiling point or close to it (100 - we consider the initial temperature of water). [and coffee made from a coffee machine has a lower temperature most often! approx. senior scientific A. Kurbatov]

2. In the process of pouring liquid into a glass, its temperature drops. True, not enough to immediately drink. This is because the temperature of the cup is close to the temperature of the air in the room and when pouring hot liquid into it, part of the heat is absorbed by the walls of the cup itself. Plus occur during the pouring of heat loss to the environment (temperature 92-82 beverage of C).

3. The liquid cools. Evaporation, heat radiation and convection work on this. Evaporation from above the glass (if there is no lid), convection from above and on the side walls, thermal radiation in all directions. At this stage, there are: the addition of additional ingredients: sugar, milk, water, etc., mixing, attempts to drink. Somewhere here T x and N (small volume drop, the temperature drops to 75-65 on C).

4. The resulting drink is finally actively drunk. A significant drop in the amount of acceleration cooling residues (assuming that the temperature is lowered to about 40 to C).

5. If anything remains in the cup, the temperature is equalized residual volume of liquid at ambient temperature (~ 20 of G).

Search for desired temperatures


For a more accurate determination of the temperature of consumption of drinks, we divide the drinking process into two stages. Firstly, take a sip of your drink (in small sips so that the drink does not burn anything, managing to cool down in the process of getting it out of the glass). Secondly, drink in sips without fear of getting burned.


Employees of the research institute were driven into the dining room for a small study. According to the results and using the statistical method Stelya was determined that approximately at 73-72 of C can attempt sorbat or sip a drink, and in the range of from 67 to 60 on C can already drink (caution, it depends on the individual characteristics of each person) . According to statistics conducted a mini-study is the optimum temperature to safely drink coffee / tea maker, was in the range of 63-60 on the S.

Cup Energy Efficiency Test


Yes, rivers of water, tea and coffee will flow right into disposable cups!

For the study, 4 common types of disposable cups were selected. And during the measurements, a thermal imager, contact thermometers and a stopwatch were used.

Sample # 1



95% paper. It has internal lamination - it is covered with a thin film from the inside, which protects against fluid leakage. The walls are two-layer paper and cardboard, between them a thin layer of air. Most often clogged with tattoos. The volume of the enclosed liquid is 400 ml. The most heat-proof (thought out) of the studied samples. A difficult relationship with Miss Ecology. The leader of the gang. It can be found all over the world at almost any point of sale of coffee / tea.

Sample # 2



All plastic. The main difference from the rest is a short visor on the head (handle on the side at the top). Outside is brown, but inside is gray. Volume of the enclosed liquid is 200 ml. The lowest, but widest in cross section - barrel-shaped. Hang out in offices, at exhibitions and gatherings of a large number of people.

Sample # 3



Younger brother # 1. The smallest in the gang (by volume = 170 ml). Thermal protection is minimal, the wall is in one layer. There is the same plastic film on the inside. He wants to be like an older brother, but so far it does not work out. Usually works in vending coffee machines. Secretly in love with Madame Espresso.

Sample # 4



Your good old friend. Works on historical trust. Plastic from the word at all. Tall, handsome, proud. He does not like hot water, he can grimace, but he suffers from the old habit. Possible locations - old school catering, train stations, bus stations and where people are in a hurry. Also found in coolers in schools, offices and hospitals.

Research


To create a representative sample, several cups of each type were taken. For testing, it was planned to pour boiling water (hot water), tea (or brew directly into them with the help of bags - field conditions), coffee (from a coffee machine). Someone stole coffee from a coffee machine just before the experiments (good coffee, I must say) and had to test only with tea and boiling water. To test the tea bags were seized, which accumulated in large quantities at the source, which asked him not to call.
The obtained values ​​for each type of cup were averaged (as it turned out, adding a tea bag to a cup practically does not affect the speed and cooling time).

The first study was the cooling of hot liquid of all 4 types of cups in wildlife in the absence of caps.


If your goal is to drink tea / coffee as quickly as possible, then # 3 is a good fit for you . Only 5-7 minutes and you can drink. At the same time they do not have covers, so will have to drink quickly, or even after 5 minutes, the temperature will be below 60 on the C (for 12 minutes, the temperature will drop from 86 to to 60 to C). Fast, but energy-efficient, stable 4th place in the study.

Glasses # 2 and # 4 persistently fight for 2nd place, while not very ahead of sample # 3 . Their result is 6 + 8 = 14 (minutes). They are almost identical in volume, but at the same time# 4 is difficult to hold in hand with hot tea-coffee, and # 2 has, albeit not very convenient, but a handle for holding a hot glass. There is also an opinion that # 4 does not interact very well with hot liquids, as At high temperatures, a variety of substances that are unpleasant for the body and the environment can be released from this type of plastic.

Hot liquids in cup # 1cool longer than everyone else. At about the 8th minute you can try to drink, at the 12th minute you can already drink bolder. And after 20 minutes, the contents of the cup will cool too much. Naturally, if you drink tea and coffee, for example, from the 12th minute, then until 20 minutes, either you will not have it left in the glass, or the liquid will cool more and its temperature will already be much lower than 60 ° C. At the moment, the # 1 record holder is up to 60 o C in 20 minutes.

As a result, we got such an energy efficiency rating for disposable cups with a cooling time of up to 60 ° C. Cups # 2 , # 3 and # 4 have one star [*]. At No. 1 two stars [**]:



And # 1 has one big plus - these are caps that hold thermal energy inside the cup and almost completely remove evaporation from heat loss processes (these caps are most often plastic, which is rather a minus from the point of view of Miss Ecology). About covers - further.

Lid tests


Three phase measurements To study the effect on the lid in a disposable drink cup was held



# + 1 : wearing cover 67 when a temperature of S. Low coffee of tea in the cup # 1 with the cover lowered from 67 to 60 degrees for 14 minutes. Significant time gain relative to a similar cup without a lid (there were 8 minutes). Efficiency Rating - [***]

# 1 ++ : The cover is fitted when the temperature reached 72 about C. The temperature is lowered from 72 to 60 degrees for 25 minutes (without the lid was 12 minutes). Energy Efficiency Rating - [***]

# 1 +++: The lid is put on immediately after the drink is poured into a glass. Up to 60 degrees in 44.5 minutes ... vzhzhzhzhzhuh ... (against 20 minutes in cup # 1 without a lid). The result is at the border of 4 and 5 stars according to our energy efficiency rating. Energy Efficiency Rating - [****]


findings


You wanted coffee or tea, and you go to one of the nearest places where you can buy it. There, along with a hot drink, they sell you a disposable glass of one of the types (this is most often # 1 ). And then task variations:

  • You need to bring it somewhere and this is more than 20 minutes:
    Better not to remove the cover. After 20-25 minutes from the moment of pouring the drink into a glass, you can drink it.
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And, remember, modern disposable cups are not the most environmentally friendly dishes. If they were made entirely of paper, they would have decomposed in 2-3 years. But the most common cups for hot drinks in Russia are coated inside with plastic. When disposing of them, the most difficult moment is to separate the plastic and paper (and we are not sure if they can do it well now?). Lids and stirrers for these cups are also plastic, which contributes to the mixing of paper and plastic with each other.

Although, in the current situation, there is a kind of dualism. From the point of view of the spread of viruses and some diseases, disposable cups are safer, but from the point of view of energy efficiency and environmental impact it is better to use reusable dishes (thermomugs in battle!).

In any case, you now have a little more data when making decisions.

PS To everyone who drinks coffee or tea immediately after it is poured into a cup - a huge respect.

Part 2 https://habr.com/en/post/495538

A small bonus - a few beautiful thermal imaging glasses














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