What Are The Physics Of "Thick Wall = Cool Smoke"?

[workman]

Hmm, actually, wood is a poor heat conductor. That's why you can hold a torch by the unlit end without burning yourself.

Still it's way better than air. Upwards of 10 times as good.

 

[unadoptedlamp]

Asking this board for a definitive answer on anything is like asking Hobbes what he thinks about math problems. Throw some physics into it? Nice touch.

 

[cosmicfolklore]

Still it's way better than air. Upwards of 10 times as good.

I disagree. I like air. Air is good stuff. I couldn’t live without it.

 

[mso489]

Posts are juggling several topics: The heat of the smoke coming into your mouth; the heat of the bowl as felt by your hand; tongue bite from the smoke in your mouth; and maybe moisture and other variables. I have two or three pipes with quite thin bowls that do not heat up to the touch and which seem to emit smoke in my mouth that is also quite cool. I haven't noticed especially reduced heat from my thicker walled bowls in the past. So I'm more undecided what, if any, relationship there is between the thickness of the walls and the heat of the smoke drawn into the mouth. I'll attempt to notice more carefully and report back any observations that emerge. Interesting question.

 

[workman]

I disagree. I like air. Air is good stuff. I couldn’t live without it.

Have you even tried it without smoke in it?

 

[jpberg]

There’s definitive internet physics going on in this thread, and they’re guaranteed 50% correct 35% of the time.
You can take that to the bank.

 

[LBT]

I've recently read in a number of posts the adage that a thick-walled pipe "smokes cooler." Can someone explain the rationale here? I'll explain my thinking below, and welcome any corrections.

Thick walls might provide more of a heat sink, but they would insulate the chamber and retain more heat than thin walls, no? One might expect a thinner-walled pipe to lose more heat to radiation and convection.

The physics of heat transfer supports the cooler smoke hypothesis. While there a number of ways to state the heat equation, the simplest one (IMO) for this question follows:

∂Q=m*c*∂T​

Where ∂Q = heat transferred within the system
m = mass of the system
c = specific heat of the system
∂T = the change in temperature for the system

So, if we have two pipes, one thin walled, the other thick walled, assuming the same bowl material, same tobacco, and same tobacco burn temp to start, the variables will be:

m-thicker wall > m-thinner wall
c-thicker wall = c-thinner wall

So, the ratio of the two systems is:

∂Q-thinner wall/∂Q-thicker wall = m-thinner/m-thicker *∂T-thinner/∂T-thicker

or

∂Q-thinner/∂T-thinner > ∂Q-thicker/∂T-thicker

So,

1. The thinner system experiences more heat transfer for a given temp differential​
2. The thicker system experiences a greater temp differential for the same heat transfer​

Situation one means hotter bowl for same temp of smoke. Situation two means similar bowl temp, but cooler smoke.

There are a lot of assumptions that can be quibbled with, but they largely cancel out, and converge with common sense (to me): thicker bowl, cooler smoke*

Lee

* = once bowls achieve the same temp, the smoke temp will be equivalent. note that briar has a large specific heat value (see comment above on soak times), so, it's a hell of a long smoke to achieve equilibrium temp between the two bowls

 

[trubka2]

Let me add my own unsubstantiated theory based on my limited experience with about 100 pipes. I don't notice a difference in the temperature of the smoke. Not saying there is none, but that I don't notice it. I do notice that some bowls get warmer quicker than others, and it has very little to do with the thickness of the wall. I have super thin bowls that don't warm up no matter how I puff, and I have thick-walled pipes that get hot with the slightest provocation. I conclude from this that it mostly has to do with the properties of the particular chunk of briar a given pipe is made from (and no, that has nothing to do with grain). All briar is not equal, so equations are completely meaningless here.

 

[Road To Pines]

I could see little wet spots forming and evaporating on the surface as I smoked.

That must have been fascinating to witness. Another surprising little movement within nature's symphony.

 

[rajangan]

. I conclude from this that it mostly has to do with the properties of the particular chunk of briar a given pipe is made from (and no, that has nothing to do with grain). All briar is not equal, so equations are completely meaningless here.

How could it have nothing to do with the grain?

 

[cosmicfolklore]

You jackhats never told there was going to be math in this test!! Crap!

 

[Road To Pines]

Posts are juggling several topics

Yes, in the interest of clarity we need to keep in mind precisely what we're referring to when we say "cooler". I'm inquiring specifically about the temperature of smoke and gas exiting the bit of the pipe.

 

[rajangan]

If you smoked a pipe made out of the ceramic that's on the nose of a space shuttle, (extremely poor heat conductor), all of the heat would dissipate out the mouth piece or the top of the bowl. It would be cool to the touch.

If you smoked out of a 100% steel pipe, (relatively good heat conductor) the pipe would get very hot, and radiate that heat. Therefore, if the tobacco in each pipe is burning at the same temperature, the smoke out of the steel pipe would be cooler than the ceramic pipe.

But which pipe would subjectively "smoke hotter"? Which would you rather smoke?

I think the answer to these questions indicates whether or not we are talking about literal smoke temperature or the gestalt of the smoking experience.

 

[Road To Pines]

Let me add my own unsubstantiated theory based on my limited experience with about 100 pipes. I don't notice a difference in the temperature of the smoke. Not saying there is none, but that I don't notice it. I do notice that some bowls get warmer quicker than others, and it has very little to do with the thickness of the wall. I have super thin bowls that don't warm up no matter how I puff, and I have thick-walled pipes that get hot with the slightest provocation. I conclude from this that it mostly has to do with the properties of the particular chunk of briar a given pipe is made from (and no, that has nothing to do with grain). All briar is not equal, so equations are completely meaningless here.

I can welcome the notion that properties other than thickness are at play. Does that mean that thickness has nothing to do with it? Or little? Or "it depends"? Dunno.

But I'm asking about the temperature of the smoke/gas entering your mouth, not about the relative warmth of different pipe bowls in your hand (though that may have something to do with it).

 

[olkofri]

The physics of heat transfer supports the cooler smoke hypothesis. While there a number of ways to state the heat equation, the simplest one (IMO) for this question follows:

∂Q=m*c*∂T​

Where ∂Q = heat transferred within the system
m = mass of the system
c = specific heat of the system
∂T = the change in temperature for the system

So, if we have two pipes, one thin walled, the other thick walled, assuming the same bowl material, same tobacco, and same tobacco burn temp to start, the variables will be:

m-thicker wall > m-thinner wall
c-thicker wall = c-thinner wall

So, the ratio of the two systems is:

∂Q-thinner wall/∂Q-thicker wall = m-thinner/m-thicker *∂T-thinner/∂T-thicker

or

∂Q-thinner/∂T-thinner > ∂Q-thicker/∂T-thicker

So,

1. The thinner system experiences more heat transfer for a given temp differential​
2. The thicker system experiences a greater temp differential for the same heat transfer​

Situation one means hotter bowl for same temp of smoke. Situation two means similar bowl temp, but cooler smoke.

There are a lot of assumptions that can be quibbled with, but they largely cancel out, and converge with common sense (to me): thicker bowl, cooler smoke*

Lee

* = once bowls achieve the same temp, the smoke temp will be equivalent. note that briar has a large specific heat value (see comment above on soak times), so, it's a hell of a long smoke to achieve equilibrium temp between the two bowls

?

Thanks for bringing math into the equation: it does away with all the guessing and the subjectivity.

I'm still having a problem with your conclusion, however:

1. The thinner system experiences more heat transfer for a given temp differential
2. The thicker system experiences a greater temp differential for the same heat transfer

Situation one means hotter bowl for same temp of smoke. Situation two means similar bowl temp, but cooler smoke.

I'm still failing to see why situation #2 would mean a cooler smoke, though. In any case, it'd mean I can still hold the pipe in my hand without discomfort, whereas a thinner wall would make me hold the pipe by the stem (I've experienced this many times: my Brigham Canadian has a thinner wall than my Vauen apple and the one gets uncomfortably hot in the area around the cherry, whereas the other doesn't); still, the temperature of the cherry being the same, I'd think the temperature of the smoke is the same. I can scorch my tongue equally with a thin-walled pipe and a thick-walled one, it's just my hand that will be spared or warmed up.

 

[Chasing Embers]

I can welcome the notion that properties other than thickness are at play. Does that mean that thickness has nothing to do with it? Or little? Or "it depends"? Dunno.

But I'm asking about the temperature of the smoke/gas entering your mouth, not about the relative warmth of different pipe bowls in your hand (though that may have something to do with it).

You're drawing from an active ember, not the heat of the pipe. Slower draw, cooler smoke, etc.

 

[olkofri]

You're drawing from an active ember, not the heat of the pipe. Slower draw, cooler smoke, etc.

Precisely. Hence my pondering and wondering as expressed above. If anything, wood being a poor heat conductor, a thicker pipe would mean a hotter smoke due to poorer heat disipation versus a thinner pipe.

 

[Road To Pines]

1. The thinner system experiences more heat transfer for a given temp differential​
2. The thicker system experiences a greater temp differential for the same heat transfer​

Thank you for that. I find the math a bit hard to follow, but I believe I get the gist of your comment.

My question is *where* in the 'system'? Is the smoke reaching the mouth influenced significantly, or at all? *How* is the heat transferred?

Some smoke will presumably not contact the edges of the bowl at all; more will contact narrow passageways.

As the ember sinks downward, less and less smoke communicates with the sides of the chamber.

Does the grip of a hand increase the heat sink, or does it further insulate the system from heat loss?

Is exposure to the environment counted in the 'mass'?

Not only mass, but the conducting vs. insulating properties need to be accounted for. Greater mass of a non-conductive, non-radiating body would retain a large percentage of heat in the chamber.

It's not clear to me how the equation applies.

 

[rajangan]

What if... now, hear me out... larger pipes are statistically more likely to have larger bowl diameters, and since the smoker is pulling the same amount of air through a larger airspace, it is traveling slower, resulting in a lower burn temperature?

 

[Road To Pines]

You're drawing from an active ember, not the heat of the pipe. Slower draw, cooler smoke, etc.

Yes, a significant point. So how does the thickness of a pipe affect--if at all--the smoke and gas once it has been released from the tobacco and/or passed through the ember?

(As a side note, it's been pointed out elsewhere that the smoke we seek generally comes from tobacco outgassing below and around the ember. We don't want to taste the burning material so much as the fragrant substances released by near-burning heat.)

Maybe there's an answer but no satisfaction.

Maybe there's no clear answer, just the continued lore, mystery, dabbling, and speculation of generations of smokers.