Thermodynamics: Melting ice cream (cool wind vs still air)

[Ichinisan]

My stubborn mother...

I met up with her near the gas pumps at the supermarket. We were waiting for someone else to arrive and just got word that he'd be 40+ minutes later than we had expected. She had just purchased ice cream from the supermarket. It was in the "warm" trunk of her car. There was a cool / cold breeze the whole time. The iOS Weather app said it was about 48° (Fahrenheit) -- but it felt colder in the breeze. She got the ice cream out of her trunk and held it in the shade of my car.

I told her that the constant breeze, while it feels cold, is well above freezing and will only warm the ice cream more quickly than if it sat in the trunk with still air. I didn't even touch on the fact that her body heat and the ambient light and solar infrared (even in the shade) would contribute to accelerated warming. She stubbornly refused to put the ice cream carton back in her car.

Has anyone tested this in a way that would prove anything to her?

 

[Cogman]

Maybe talk about defrosting a turkey? One of the suggested turkey defrosting methods is running cool water over it.

 

[drinkmorejava]

My stubborn mother...

Has anyone tested this in a way that would prove anything to her?

Put some ice cubes outside with a fan blowing on half of them.

Forced convection promotes greater heat transfer, so you should already know the answer.

 

[SOFTengCOMPelec]

My stubborn mother...

I met up with her near the gas pumps at the supermarket. We were waiting for someone else to arrive and just got word that he'd be 40+ minutes later than we had expected. She had just purchased ice cream from the supermarket. It was in the "warm" trunk of her car. There was a cool / cold breeze the whole time. The iOS Weather app said it was about 48° (but it felt cooler in the breeze). She got the ice cream out of her trunk and held it in the shade of my car.

I told her that the constant breeze, while it feels cold, is well above freezing and will only warm the ice cream more quickly than if it sat in the truck with still air. I didn't even touch on the fact that her body heat and the ambient light and solar infrared (even in the shade) would contribute to accelerated warming. She stubbornly refused to put the ice cream carton back in her car.

Has anyone tested this in a way that would prove anything to her?

I don't want to appear rude, or be insulting your intelligence and possible lack of schooling.

The convection currents, because cold air drops, and warm air rises, do a very strange thing, to someone who does not know about, the appropriate laws of physics.

But you seem to have completely, forgotten, Newtons tertiary (sometimes known as fifth) law of Thermodynamics.

Which is nicely explained here:

Newtons Law 5 C

Which explains, using liquid Nitrogen and a glass sphere, why your mother was right, all along. The orange section in the middle, is because they used a thermal imaging camera to show the effect. I have an alternative link, but the one I supplied seems best.

 

[Ichinisan]

I don't want to appear rude, or be insulting your intelligence and possible lack of schooling.

The convection currents, because cold air drops, and warm air rises, do a very strange thing, to someone who does not know about, the appropriate laws of physics.

But you seem to have completely, forgotten, Newtons tertiary (sometimes known as fifth) law of Thermodynamics.

Which is nicely explained here:

Newtons Law 5 C

Which explains, using liquid Nitrogen and a glass sphere, why your mother was right, all along. The orange section in the middle, is because they used a thermal imaging camera to show the effect. I have an alternative link, but the one I supplied seems best.

LOL! That's great!

 

[DrPizza]

What was the temperature inside the trunk versus the temperature of the air?

 

[Ichinisan]

What was the temperature inside the trunk versus the temperature of the air?

Didn't feel the air in her trunk, but it couldn't have been very warm since it had been parked for a long time and the weather outside was a bit cold all day long (slightly uncomfortable compared to what I would call "cool" weather).

I tried to describe it like: If you don't want to think of it as "absorbing heat," you can think of it as "losing its cold." In the trunk, the carton might develop a skin of cold air around the container and the plastic grocery bag. In the breeze, you're constantly removing that skin and bringing in air that is relatively warmer than the ice cream. So, instead of cooling a small amount of air around the ice cream, you're cooling a lot more air that's being moved past it. Even though the breeze feels cold, it's not as cold as the ice cream. It's imparting heat energy into the ice cream and warming it.

 

[WilliamM2]

In 40+ minutes at 48 degrees the ice cream would be ruined either way. Pointless argument.

 

[thescreensavers]

^ we have a winner!

Not to mention the ride home!

 

[serpretetsky]

She stubbornly refused to put the ice cream carton back in her car.

Has anyone tested this in a way that would prove anything to her?

warm car vs cool but breezy outside?

I wouldn't be able to tell you which is worse. I'm not so sure why you are so confident of the answer.

 

[CZroe]

warm car vs cool but breezy outside?

I wouldn't be able to tell you which is worse. I'm not so sure why you are so confident of the answer.

What melts faster:
An ice cube in a cup of room-temperature water
or
An ice cube in contact with your 98.6-degree fingers held under the flow of cold water from the sink
?

It had warmed up to about 50 degrees outside. If anything, the trunk was cooler due to being shaded, somewhat insulated since the cooler temperatures earlier in the morning, and limited exposure to any warmth from the rest of the car. The trunk is the room-temperature water. The cool breeze while being held is the flow of cold water over the pinched ice cube. It was VERY windy. Temps would have to be crazy different for there to be any question about which choice was superior.

 

[serpretetsky]

It had warmed up to about 50 degrees outside. If anything, the trunk was cooler due to being shaded, somewhat insulated since the cooler temperatures earlier in the morning, and limited exposure to any warmth from the rest of the car. The trunk is the room-temperature water. The cool breeze while being held is the flow of cold water over the pinched ice cube. It was VERY windy. Temps would have to be crazy different for there to be any question about which choice was superior.

How do you know it was morning, the trunk was shaded, and that it was "VERY windy"?

Anyways, I don't need a water analogy but thank you. The concept makes perfect sense to me, I just don't have an intuitive sense of which one would melt the ice cream faster, especially with such little data

 

[CZroe]

How do you know it was morning, the trunk was shaded, and that it was "VERY windy"?

Anyways, I don't need a water analogy but thank you. The concept makes perfect sense to me, I just don't have an intuitive sense of which one would melt the ice cream faster, especially with such little data

#1: Because the OP said it was windy
#2: Trunks are always shaded from the sunlight (you should've been able to tell that "truck" was a typo since it didn't magically become a "car")
#3: it wasn't morning, but mornings are typically cooler than later in the afternoon
#4: I was the person they were waiting for.

It should be intuitive because the air acts almost the exact same way: as long as it is replenished and we aren't dealing with extreme temperature differences, the exchange will go faster.

Now, this is a OC tech forum, so perhaps this analogy makes more sense.
Which will throttle first:
A Core i7 Haswell with a water block and a broken pump in an air conditioned roomat room (zero air or water flow; water block is insulating)
or
a Core i7 Haswell with a stock HSF and a working fan on a hot day with no air conditioning
???

The concept is the same. The one with a comparatively infinite supply of cooler air flowing (re-supplying) will cool faster. It's the same concept as warming something that is below ambient temperatures.

 

[Biftheunderstudy]

To really answer this, we would need to know what the temperature of the air was outside *and* the temperature in the trunk.

Given that you said the car was outside for a long time in the cold, it's probably a safe assumption to say that the air temperature was the same outside as it was for in the trunk.

Next, the answer is given by Newton's law of cooling,

Q = h_c A \Delta T

Q is the heat transferred per unit time (the rate)
\Delta T is the temperature difference of the air to the ice cream
h_c is the convective heat transfer coefficient

h_c depends on the relative velocity of the air and looks something like
h_c = 10.45 - v + 10 v^1/2

If the air temperature was the same, then the windy conditions would provide a much higher rate of heat transfer.

(Note: the trunk would seem warmer for exactly this equation, your skin senses rate of heat transfer, not absolute temperature. The rate in the trunk is slower and so it feels warmer.)

 

[Ichinisan]

To really answer this, we would need to know what the temperature of the air was outside *and* the temperature in the trunk.

Given that you said the car was outside for a long time in the cold, it's probably a safe assumption to say that the air temperature was the same outside as it was for in the trunk.

Next, the answer is given by Newton's law of cooling,

Q = h_c A \Delta T

Q is the heat transferred per unit time (the rate)
\Delta T is the temperature difference of the air to the ice cream
h_c is the convective heat transfer coefficient

h_c depends on the relative velocity of the air and looks something like
h_c = 10.45 - v + 10 v^1/2

If the air temperature was the same, then the windy conditions would provide a much higher rate of heat transfer.

Thank you!

...
(Note: the trunk would seem warmer for exactly this equation, your skin senses rate of heat transfer, not absolute temperature. The rate in the trunk is slower and so it feels warmer.)

I figured this much, but it's impossible to get my mother to believe it. It's the same principle as wind chill, but we're talking about cool wind that's still warmer than the object in question (the ice cream carton).

 

[CZroe]

To really answer this, we would need to know what the temperature of the air was outside *and* the temperature in the trunk.

Given that you said the car was outside for a long time in the cold, it's probably a safe assumption to say that the air temperature was the same outside as it was for in the trunk.

Next, the answer is given by Newton's law of cooling,

Q = h_c A \Delta T

Q is the heat transferred per unit time (the rate)
\Delta T is the temperature difference of the air to the ice cream
h_c is the convective heat transfer coefficient

h_c depends on the relative velocity of the air and looks something like
h_c = 10.45 - v + 10 v^1/2

If the air temperature was the same, then the windy conditions would provide a much higher rate of heat transfer.

(Note: the trunk would seem warmer for exactly this equation, your skin senses rate of heat transfer, not absolute temperature. The rate in the trunk is slower and so it feels warmer.)

Not unless you want exact figures. When my soup is so hot that it burned the roof of my mouth, I don't need to know the exact temperature of the soup or the air-conditioned room to know that blowing my 90-plus-degree breath over it will cool it faster than simply being left still in the static, room temperature, air. It's intuitive. I know this even though my breath is significantly warmer than the room temperature air it is already in contact with.

Unless we are dealing with extremes, equalization of the temperature differential between the object and its surroundings will accelerate with a continual flow. You put a fan on it in an enclosed room and it will equalize faster.

 

[MrDudeMan]

The real answer is to return the ice cream since you were still at the grocery store and then buy it again when the other person arrives. This situation required a small amount of critical thinking, not math.

 

[WHAMPOM]

My stubborn mother...

I met up with her near the gas pumps at the supermarket. We were waiting for someone else to arrive and just got word that he'd be 40+ minutes later than we had expected. She had just purchased ice cream from the supermarket. It was in the "warm" trunk of her car. There was a cool / cold breeze the whole time. The iOS Weather app said it was about 48° (Fahrenheit) -- but it felt colder in the breeze. She got the ice cream out of her trunk and held it in the shade of my car.

I told her that the constant breeze, while it feels cold, is well above freezing and will only warm the ice cream more quickly than if it sat in the truck with still air. I didn't even touch on the fact that her body heat and the ambient light and solar infrared (even in the shade) would contribute to accelerated warming. She stubbornly refused to put the ice cream carton back in her car.

Has anyone tested this in a way that would prove anything to her?

Yes. Buy her an insulated bag at Walmart and solve the problem.

 

[bwanaaa]

show her this thread

 

[Red Squirrel]

A good example of this is take an ice cube and drop it in a glass of water. Take another ice cube, put it in the sink and let the water run over it. The one in the sink will melt faster.

Though, to be fair, it was probably hotter in the car than outside, as cars get really hot even if it's not that hot out. Though at that temp it's not like it would have been super hot in there either. The outer edges of the ice cream would maybe melt a bit inside the container but it would most likely be ok, but 40 minutes is kind of pushing it. I would have just brought it home right away and went back to wait for the other person or tell them I can't wait that long since I have ice cream and to just meet me at home.

 

[Ichinisan]

A good example of this is take an ice cube and drop it in a glass of water. Take another ice cube, put it in the sink and let the water run over it. The one in the sink will melt faster.

Though, to be fair, it was probably hotter in the car than outside, as cars get really hot even if it's not that hot out. Though at that temp it's not like it would have been super hot in there either. The outer edges of the ice cream would maybe melt a bit inside the container but it would most likely be ok, but 40 minutes is kind of pushing it. I would have just brought it home right away and went back to wait for the other person or tell them I can't wait that long since I have ice cream and to just meet me at home.

The air outside was really cool. Slightly uncomfortable with the wind blowing.

No light would have entered the trunk. She was basically taking it out of the shade and moving it into the light. I tried to tell her that the constant breeze was even bigger factor. She seemed to think that holding it in the cool breeze would keep it cold. I tried to tell her that, as long as the breeze is warmer than the ice cream, a breeze will cause the ice cream melt faster than being in still air of the same temperature.

 

[CZroe]

A good example of this is take an ice cube and drop it in a glass of water. Take another ice cube, put it in the sink and let the water run over it. The one in the sink will melt faster.

Though, to be fair, it was probably hotter in the car than outside, as cars get really hot even if it's not that hot out. Though at that temp it's not like it would have been super hot in there either. The outer edges of the ice cream would maybe melt a bit inside the container but it would most likely be ok, but 40 minutes is kind of pushing it. I would have just brought it home right away and went back to wait for the other person or tell them I can't wait that long since I have ice cream and to just meet me at home.

Great minds think alike.

What melts faster:
An ice cube in a cup of room-temperature water
or
An ice cube in contact with your 98.6-degree fingers held under the flow of cold water from the sink
?

 

[sm625]

The best thing to do is wrap the ice cream in plastic bags, as many as possible, and then place the package inside a cardboard box, and then place the box in the coolest possible location. Even if you do not have a box, the insulation from the bags will reduce the wind effect, making the temperature delta the primary melting force. If wrapped properly, a container of ice cream will survive a temperature delta of 15 degrees F for more than an hour.