Need some assistance with scientific theory........d'oh


Nuggler
#1
Has anyone seen the commercial for a solar powered fan one puts in the window of their car, leaves it parked in the sun with the windows up, then comes back to find the car interior cool and comfy??

One jams the fan in the top of the window and the sun makes it go, thereby sucking out all the nasty heat, leaving the car cool.

I was never a physics major, but it would seem that if the outside temperature is say 35C (pretty hot), and the car interior is 50C say?? , the very best your going to do if the little fan completely exchanges the air every few minutes is 35C............Not cool and comfy IMHO. It's only a fan, not an air conditioner.

Or am I missing something??

Not a life changing revelation, but it would be nice to know.

Thanks

UGG
 
#juan
#2
No problem here

I've seen those fans. I wouldn't expect too much "cooling" from them. Remember, the only way any ventilation system can "cool" is to impart the excess heat to the air being circulated through the car. If the car is sitting in the sun and it is 35 degrees outside, the temperature inside the car can only be higher even if you had one of those fans in every window.
 
Just the Facts
#3
Quote: Originally Posted by oldnugly

the very best your going to do if the little fan completely exchanges the air every few minutes is 35C............Not cool and comfy IMHO. It's only a fan, not an air conditioner.

Yes I believe you are correct. You likely would not even get down to 35c, as the sun would heat the structure of the car itself, especially if it's a darker colour. The frame would then in turn radiate heat into the compartment of the car.

Still, it sounds like a good idea. Even 39c is better than 50c.
 
TenPenny
#4
Quote: Originally Posted by oldnugly

Or am I missing something??

You're missing the ability to swallow vague advertising statements while ignoring physics. You're just not gullible enough.
 
Kreskin
#5
It would probably melt in my car.
 
Nuggler
#6
Quote: Originally Posted by TenPenny

Quote: Originally Posted by oldnugly

Or am I missing something??

You're missing the ability to swallow vague advertising statements while ignoring physics. You're just not gullible enough.

Ten Penny:

Thanks, that's the kindest thing anyone has said to me in many a moon. I hope to continue to miss that ability

Sorry about yer car meltin Kreskin. They ARE putting far too much plastic in auto construction these days.

Wonder if the dolts that made that commercial (no doubt they sold a pile of those fans) read CC.

Ugg
 
Simpleton
#7
Quote: Originally Posted by oldnugly

Has anyone seen the commercial for a solar powered fan one puts in the window of their car, leaves it parked in the sun with the windows up, then comes back to find the car interior cool and comfy??

One jams the fan in the top of the window and the sun makes it go, thereby sucking out all the nasty heat, leaving the car cool.

I was never a physics major, but it would seem that if the outside temperature is say 35C (pretty hot), and the car interior is 50C say?? , the very best your going to do if the little fan completely exchanges the air every few minutes is 35C............Not cool and comfy IMHO. It's only a fan, not an air conditioner.

Or am I missing something??

Not a life changing revelation, but it would be nice to know.

Thanks

UGG

The car windows would be the killer. If you covered up all of your car windows so that the Sun couldn't shine in, you might get a cooler car. But nowhere near as cool as a car with air conditioning.

To effectively cool your car, you would have to remove the humidity from the air inside your car. Removing the hunidity would make the car much more comfortable, and it would feel cooler. Even if it weren't. Additionally, you would have to remove the warm air to the outside, and replace the inside air with cooler air. This is how air conditioners work.

The warm air is sucked into the air conditioner, where it passes over a cooled radiator. The humidity in the warm air condenses on the coils and drips to a drainage hole. The cooled air is then recirculated within the room.

A simple fan would not effect the humidity level, nor would it replace the warm air with cooler air. Essentially, you would see virtually no change in your car's temperature.
 
#juan
#8
I have to re-organize my position a little on this subject. bercause I ran accross one fan company that acually stated the volume of air their fan was likely to move when the solar cell was in direct sunlight.

If, for the purposes of this discussion,the fan moves 2 cubic feet of air per minute. If we also assume the temperature inside the car to be 50 degrees and the outside temperature to be 30 degrees, the amount of "cooling" available would be 2 cfm times 1.08, times the temperature difference which is 20 degrees or roughly 43 btuh.(btus per hour). The average car airconditioning unit provides about 6500 btuh of cooling so it is more or less obvious that these little fans are not going to keep your car "cool and comfy, parked in the sun, on a warm summer day. Finding a shady parking spot might be a better answer.
 
Simpleton
#9
Quote: Originally Posted by #juan

I have to re-organize my position a little on this subject. bercause I ran accross one fan company that acually stated the volume of air their fan was likely to move when the solar cell was in direct sunlight.

If, for the purposes of this discussion,the fan moves 2 cubic feet of air per minute. If we also assume the temperature inside the car to be 50 degrees and the outside temperature to be 30 degrees, the amount of "cooling" available would be 2 cfm times 1.08, times the temperature difference which is 20 degrees or roughly 43 btuh.(btus per hour). The average car airconditioning unit provides about 6500 btuh of cooling so it is more or less obvious that these little fans are not going to keep your car "cool and comfy, parked in the sun, on a warm summer day. Finding a shady parking spot might be a better answer.

I don't know about the math that you offer, thermal dynamics are not my field of expertise. I specialize in corruption, criminal radio, and putting *******s behind bars. But I would agree with you that these fans will not cool your car very much.

I would tend to think that these fans would have about as much effect as running your car heater on the lowest setting. It's a fan that is pushing hot air around. The warm air is not being replaced with cooler air, and the humidity in your car is not being affected at all.
 
Kreskin
#10
Quote: Originally Posted by Simpleton

I don't know about the math that you offer, thermal dynamics are not my field of expertise. I specialize in corruption, criminal radio, and putting *******s behind bars.

Is that a diploma program?
 
Simpleton
#11
Quote: Originally Posted by Kreskin

Quote: Originally Posted by Simpleton

I don't know about the math that you offer, thermal dynamics are not my field of expertise. I specialize in corruption, criminal radio, and putting *******s behind bars.

Is that a diploma program?

They were going to make it a diploma program, but they decided it would be best to separate the wheat from the chaffe. I hear being an *******, is a diploma program. And in the case of corruption, it's a co-op program as well.
 
iARTthere4iam
#12
I just fill my car up with ice! Doesn't everyone do that?
 
Nuggler
#13
[quote="Simpleton"][

I don't know about the math that you offer, thermal dynamics are not my field of expertise. I specialize in corruption, criminal radio, and putting *******s behind bars. But I would agree with you that these fans will not cool your car very much."

So, like, you're a mafia rat??









JOKE
 
#juan
#14
How soon is it going to be before some genius leaves a baby in a car in the hot sun and believes the stupid adds about these assinine fans? Cooling, industrial refrigeration, and large commercial air conditioning are my field. My advice: Don't do it.
 

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