Keeping cool without sweat

Note for new readers: this blog presents a rather technical approach to the subject of living comfortably in the tropics. It aims to teach you about tropical comfort and discomfort. Don't read this blog unless you got a "B" or better in high school physics or are an architect/builder who needs to understand heat transfer! If you're more interested in tropical lifestyle matters, the ups and downs of living in paradise, you can check out the blog by my brother Jack at:

http://www.nationmultimedia.com/webblog/home.php?uid=361

One of our readers, reflecting on the pleasures of keeping cool using one of those "mist fan" machines while struggling to enjoy a good cigar, raises the following question:

There has to be some balance point here, where body cooling by external evaporation is such that the body does not need to sweat heavily and so is happy in a high humidity atmosphere. These machines do work, the only problem I have with them is keeping my cigar alight...........

Yao Bar at sundown, your author making the sketch that you see here

Appropriate meditiation on this matter requires a proper setting, and I write here from one of my favorite streetside venues, the Yao Bar off Ekamai, where the sun is setting in a tawny sky at the end of a day warm enough to raise a slight sweat as I was walking here. Now the waitress is serving a large (22 oz) bottle of cold Chang beer, 70 baht, over a large glass of ice cubes (3 degrees C, but my radiant thermometer is probably mistaken here because it's mosquito brain does not really know the exact emssivivity of ice, or as you can see, of the sky which of course is not 6 degrees but closer to 30 degrees, only emitting like a 6 degree object). Here, carressed by a gentle breeze, watching life, much of it casually and lightly clothed as tends to be on these sois, I am comfortable enough, not sweating at all, though I am continuing to produce, as we all do while engaged in these indolent activities -- and subsisting on a healthy Thai diet of fish and rice, not fatty British pub food simultaneously engaged in heated discusion of such matters as cricket and motor racing-- heat. And my heat production is likely to be around 50 watts.

Now sitting here I perceive that I am comfortable but on the verge of sweating. (At this point I can only appeal to the reader's intuition when I say comfortable, since I can neither define that term or conversely define its opposite, uncomfortable, though in the future we will necessarily have to face this definitional task, not as simple as it might first appear).

Let us now proceed to make some estimates of the transfer of heat that is occurring at my bodily envelope (having disposed of the problem of dealing with transfer of moisture, since I'm not sweating, though almost sweating).

Since I am warmer than the air around me by about 3 degrees, and the transfer of heat being a linear function of temperature difference with a constant of proportionality of about 10 (for a pleasant breeze) my transfer via convection to the air will be in watts

W=10*(34-31)=30 watts

I am also radiating heat directly to both the "cold" sky at 6 degrees and my other surroundings, and without going through l the tiresome arithmetic, Stefan Boltzmann constants and so forth (unless I later add an appendix to this chapter), my estimate for radiant loss is a minor 10-15 watts.

The 22 ounce bottle of Chang beer which by ingesting I am raising from 18 to 37 degrees over a time period of 20 minutes provides further cooling of about 5 watts, not counting the vasodilative impact of alcohol on improving the blood supply to my nose. I neglect my cigar, and I am now too weary with these exertions to account for respiratory loss, either sensible or latent, though I think it might be as much as a few watts.

Observation of surroundings: the waitress is hacking at a mango in the course of making herself som tam dinner; though lightly dressed her skinny brown legs to which my eyes are drawn are doubtless more effective in transferring heat to the air than my ham-like euro limbs. The bartender, who has a large belly, is engaged in mild activities, and has elected for his comfort to be shirtless. Altogether, we represent a sample of three varied non-sweating bodies, with heat production approximately equal to the rate of heat being lost to our environment. Therefore we meet a working definition of comfort with sweating:

Energy produced sweatlessly=energy lost without need for sweat.

On this basis, I propose that for a typical fahlang, sweating will not be necessary for sedentary activity with surrounding temperature (e.g. air temperature but also consider surrounding radiant temperatures) of about 30 degrees or a little less. Under these or cooler conditions, we do not call on any heat dissipative mechanism that is sensitive to humidity, so we may say in a gross sense that humidity is not a factor in our comfort. If however our level of effort should increase to say 100 watts, we will not be able to throw off enough heat to the surroundings and after a few minutes our body and skin temperature will begin to rise and our sweat system will activate, with the rate of cooling being very sensitive to humidity (more on this later). And we will begin to say that we are too warm (suggesting that sweat = thermal discomfort.)

So my answer is this: humidity doesn't matter too much (except in relation to such issues as keeping cigars lit and beers cool) as long as we are not sweating, ie at a temprature of roughly 30 degrees in sedentary mode.

Thin Roofs...and foil

Even now at the winter solstice, with the noon solar radiation reduced some 20 percent, any thin darkish thin surface (such as a metal roof or a tile roof) heats up to 50 degrees C or more, with the heat being almost immediately transferred undiminished to the underside, as you can see from the temp reading of the underside of this rubberized canvas tent which is supposed to provide cooling shade but really provides heating shade which will radiate on the order of (52-32)*5=100 watts per square meter to my balding head, plus perhaps as much again convected to the air below. Not as bad as the 700 watt sun, you might say, but not comfortable either – and suffocating if the underside of the roof is not radically ventilated. So next time you are sitting under one of these tents at a Thai wedding or funeral, be warned -- it's the heat, not your emotions, that is causing you to feel like you are going to faint.

Here is an excerpt from the manual of the Australian company Bluescope Steel who make (and promote) steel roofing in Thailand. This indicates a good reduction in heat transmission through thin roofs (steel, cement tile, etc) with foil insulation, properly installed (air space above and below foil, and foil with shiny side down.) For a dark roof, the thermal transmission is said to drop from 165 to 22 watts, almost 90 percent.

Foil sales folks must be delighted with this conclusion. But be aware that it contains at least one hidden but important assumption -- very low convective transfer from the roof to the room below because the air beneath the foil is taken to be perfectly still. But this is not true in any case for many reasons. Convective cells develop even in sealed spaces, desirable fans move air, and required ventilation to replace that air which will otherwise heat at about 2 degrees per minute (ventilation rate of approx one room air change per minute--that's right, not one or two air changes per hour, as in most attic spaces even with vents) so there is in fact much more downward convective transfer from the roof than this chart suggests.

My estimates do not yield quite such promising results – my 1935 Eshbach Engineers Manual (college edition) indicates an R value bonus of only about 2 or so for a single layer of foil. And a direct measure of the efficacy of shiny vs. black spray paint surface on the foil which can be seen in the simple room simulation which I performed last month yields a reduction of about 50 percent in heat transmission. This implies that the heat flux from downward radiation and convection are about the same. Th foil brigade will try to tell you that here is not convective transfer downward at all, and this just ain't true.

Want to know the exact ruth? The fact is that the physics of downward heat flow in roofs is extremely complex, the stuff of learned papers by mathematically oriented professors.

But I don't question that properly installed foil will improve matters-- from very bad to not as bad--in the case of a thin tile, cement, or metal roof. Studies such as those done in Florida suggest aircon energy savings of perhaps 15 percent with the addition of foil. My caveat is that in most practical situations one cannot rely on foil alone to prevent uncomfortable heat buildup from a foil-insulated roof.

Some reasonably unbiased web sites describing use of foil insulation are:

Florida studies indicating reduction of energy 25 percent and temp 6 deg:

http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1231-01/index.htm

Wikipedia:

http://en.wikipedia.org/wiki/Building_insulation

Q&A on foil insulation by experienced researchers:

http://www.fsec.ucf.edu/en/publications/html/FSEC-EN-15/index.htm

Night before Christmas

Some think of Santa. I dream of Planck's Constant.

I put a steel bar outside on the roof at night, facing upward into the relatively clear sky (stars visible), compare its temp with the temp of a shielded sensor; you see, on December 23-24, 2007, a temp suppression of the bar of only about one degree. This is with a sky radiant temp (Radioshack sensor) of about 5 degrees and relatively high dew point of about 21 degrees. Notice the wave of humidity at about 2 to 4 am, dew point reaches close to air temp, so RH is close to 100 percent and the temp suppression becomes much less (in part because water begins to condense on the steel surface, creating heat.). Therefore we cannot get much radiant cooling under these circumstances of high air saturation.

It happens that I did not in my bed dreaming of sugar plums notice any suffocating wave of humidity at 2-4 am, perhaps it did not arise in the indoor environment. Why? Or was it the low temp, not over 23 degrees, that kept my body well below the point of perspiration? All worth investigating as the hot season approaches and the night temps hover up at around 30 rather than this month's more comfortable mid twenties.

Shortest day

For millenia we northern folk have been mighty nervous about these shortening days of winter and have invented all kinds of potions and ceremonies to ward off the fear that the days were going to get shorter…and shorter.. and God know what then. So we have mulled wine and moldy grain (which is what Tacitus described as the favored beverage of the barbarians of the north) and those big stone henges in Ireland and even Peru where the priests coax the sun back from wherever it has wandered off to, and nowadays Prozac for Seasonal Affective Disorder and doubled up holiday AA meetings for those who overdid it in Christmases past. Here in Thailand it was April, not Decmber, that was the big deal in the old days, but this hasn’t prevented the Thai from going mad with joy over Christmas and New Years as you can see from this little video clip I took last night in the Emporium. Notice at the end that it is against the law to photograph Santa Claus here in the land of smiles, leaving poor Santa looking like some kind of frightened and much overdressed hostage imprisoned here far from his native latitudes.

With the sun vacationing somewhere down in Australia some 36 to the south, solar radiation, as you can see from the readings of a solar radiometer at Bnagkok's Mahidol University is now peaking at about 750 watts per square meter.

http://nanotech.sc.mahidol.ac.th/weather/Weather_Soil_Experiment.htm

As always you correspondent finds the season an emotional challenge, taking comfort that though the days are a little shorter they aren’t a lot shorter. This morning, in fact, the sun rose over Bangkok at 6:30 am, and tonight setting at 6:00, as I make my way to the pub for what I hope will be a modest pint or two, leaving the sky over Sukhumvit washed with a smoky plum, when I take this photo thirteen minutes later.

But where are those refreshing cold snaps that are supposed to be blowing down from the north? This year you hear Thai complaining of the heat and muttering about global warming, with the wind even now backing around to the south and the temps creeping up into the low thirties, a preview of the coming hot season.

Red wine in them hills

Jack and Dah had me over for dinner, quite a nice pasta with little sea clams, plus a red wine that Jack said was a local Thai wine, 600 baht a bottle.

It was certainly drinkable. We did a second bottle. I thought about this. "Don't wine grapes have to grow in a cool place?"

"That's it, this stuff is only 100 clicks from Bangkok, it's a kind of hill station. Look at the bottle."


"Fourteen degrees latitude, that's not far."

Jack said "About three hundred meters above sea level. Cool nights, not far from our village. We're at two hundred." Jack and Dah were building another house in this little Isan village they had discovered, four hours from Bangkok.



Now after the second bottle Jack was mad to grow wine grapes. He wanted to know all about the climate there, he wanted me to compare Bangkok, and the PB wine growing place near Khao Yai, and his new village at the foot of the same hills a little to the west of Khao Yai. The next week, mid December, we took the bus to a little place south of Korat called Pak Tong Chai, near where Jack and Dah were building their house. An uncle picked us up and drove us around, we stayed a couple of days. The mornings were delightful, dew on the grass and nice little jungly tropical mists over the patches of rice paddy.


I took temp measurements with my roving Hobo, compared them with Bangkok. Here they are.




Cool nights indeed, you can see the difference at night, I shaded it blue. Sundown the temp dropped a lot up there, much more than Bangkok. You could se stars at night.

Sunday roast

This Sunday afternoon I was alone and I took to the streets walking, no more than a slight film of sweat on the brow on this fine California-like afternoon, then sitting in the park for a while then consumed a giant roast pork dinner and the Financial Times in the Robin Hood.

The steady graphed points are a recording of the temp and dew point on my deck at home, beneath a large mango tree. The irregular traces are a recorder that I carried with me, you can see every time I go into an air conditioned space where the temp and dew point both drop a few degrees. Consultation with Carrier's chart indicates that each cubic meter of conditioned air has been subjected to about 10 KJ of enthalpy reduction--at considerable energy cost.

Sunday afternoons bring a few families out and into the pubs, you can see this sixty-something guy with his thirty-something Thai wife and "half child", the dream of many a Thai girl. Some of the foreign-Thai relationships are disastrous for the man, but this one looks pretty pleasant for all, arguably more interesting than playing golf and visiting prospective nursing homes back in the old country (or obsessively recording temps in the new), and certainly a step up in comfort and respectability for the girl from an poor Isan village.

Interesting stuff blows in from Isan

Sometimes for relaxation in the cooler evenings now I like to go down to Soi Cowboy and watch the world go by, just sitting at a little bar by the side of the road, watching tourists and bar girls, I try to figure the girls that are fresh from upcountry from the ones who say they are fresh from upcountry. They blow into Bangkok, the prettiest girls from the villages, dozens a day, on buses to Mo Chit and trains to Hua Long Pong, and a lot of them drift over to this street and the other two or three venues that cater to the tourists looking to see Bangkok's notorious sex scene. There they wait by the side of the road, in front of their clubs, like trout waiting under the banks of a stream for passing grubs.






This time of year the wind is from the north to northeast too, and along with the girls comes the cool air of the north, equally delightful, the air warming like the girls themselves as it blows out of Udorn and Korat and Surin, down from the hills, across the plain, and into the wicked concrete alleys of the town. The journey takes about a day, and you can see from the twin pictures here of parallel temp and dew point of November air in Bangkok and Korat, 165 to the north. The air moisture stays pretty much the same, but you can see the arrival of the air in the big city heats it up by about 4 degrees C. Even so, most Bangkokians will be complaining of the cold, and if they venure to the northeast, they will make special purchases in fahlang thrift shops or expensive department store, depending on their situation in life, of "winter" clothes.





Oh, I should note that not all of them are girls.

Change your perception of, and attitude toward, discomfort

The prospect of staying longer in the house of Jack and Dah, on the occasion of their travels in the country, seemed agreeable to a degree that was even enhanced as the dew point declined during this week, and I found myself spending less time in the pub and looking forward, as a man might in the morning shower look forward to an anticipated departure or an encounter with a certain lady that promised to end in a pleasant conclusion, to my evening cigar and a cold bottle of Singh, and a profitable review of the basic equations of gaseous heat transimission. And yet, as the week went on, I found myself to an increasing degree drawn to reading Swann's Way, from which I began to learn slowly a new manner of perceiving everyday events, as in reading the passage in which Proust's father, remarks to his son's visiting friend, who is visibly wet on the occasion of his visit to the house at Combray: "Why, Mr. Bloch, is there a change in the weather? Has it been raining?" Which drew from Bloch nothing more instructive than: "Sir, I am absolutely incapable of telling you whether it has rained. I live so resolutely apart from physical contingencies that my senses no longer trouble to inform me of them." This bringing to mind the teachings of the eminent Thai monk Buddhasa Bhikkhu who told of his many solitary months living in the forest near the current monastery of Suan Mokh, in the province of Surat Thani, and his conquest of mosquito bites in the evening by strict adherence to the precepts of the Dhamma. "Not using mosquito nets...was very beneficial. It helped us xpand our thinking, to feel unburdened, to wake up better, and to consider sleep as a temporary rest rather than a pursuit of or indulgence in comfort. It also helped us practice wakefulness to the best."

Cool night sky

I got a giant case of ptomaine from eating a giant hot dog at the Robin Hood and while bedridden began to read a copy of Proust that I found at Jack's place, he and Dah were upcountry. A few days in the world of Combray put me in a contrarian frame of mind and I began to imagine that much of what I believed about roof insulation could be wrong, that rusty tin roofs might be the best of all. Thai country folk lived under them. They just stayed under the house, not in the house, in the daytime when the uninsulated roof created oven-like heat in the room. But at night maybe the outward radiation would cool the simple metal roof below air temperature.

An email from technology innovator Steve Baer reminded me of work by the solar master Harold Hay who invented and promoted a roof pond concept in California that relied on night radiative cooling to store "coolness" for the day use.

I built a "upcountry" room with a metal roof and zero ventilation and let it sit on my roof for a couple of days. Of course not a real room, but one of about a cubic foot size with a sheet of mat black aluminum foil for a roof and the room itself a foam picnic box that I bought for a buck at the Chinese shop down the street. Into which I put a brick for thermal mass and a hobo to measure temp and dew point.

You can see the temp history of the country room in red and the temps of Jack's bedroom and the outside temp (last two almost the same) over several days. The country room is impossible in the daytime but gets really cool at night. At least toward the end of the test period when the dew point got fairly low and the night sky temp fell to as low as -5 degrees C. So you might be very happy with a simple tin roof at night -- though not at day. And, this being a dryish night, note that the suppresssed temp is still way above the dew point, so there will be no problematical condensation. The question being, how about during the hot season, when the dew points are a lot higher, maybe 18 C instead of 10 C? Would you get any radiative night cooling then? If so, would water start to drip from the ceiling?

By the way, I say test boxes--there were two of them. One had foil with shiny side down (the blue line) the other had the bottom surface of the foil spray painted mat black (red line). The shiny foil reduces the peak heat of the day but also slightly reduces the cooling effect of night radiation.

In the cool of the pub

Sometimes the only place that seemd tolerable was a pub, so I spent time working in those fine places sipping Heinekens and sketching out my ideas on paper napkins. Sometimes I'd lose interest in thermodynamics -- I did poorly in it at college --and then I'd draw little pictures of the action around me, older guys like myself thinking and drinking or watching TV with their bored girlfriends picking at the fahlang food or patiently waiting, like rice farmers waiting for the rains.
















I noticed that many of these girls had remarkably large hands.

A one-watt air conditioner

Air conditioning for your pet mouse

Jack and Dah have a goal: no house air conditioning.

Air conditioning is notoriusly inefficient in Thailand, with typical split room-size air conditioners churning out 12000 BTU per hour (3000 watts) of cooling per room, mainly energy spent on cooling sun-heated walls and vaporizing moisture that freely enters the room from outside sources, all at a cost equal to 35 percent of a Thai college graduate's salary. Tankers of oil steam into the Gulf to meet this wasteful demand.

And of course with the light, leaky construction of a traditional Thai house an off-the-shelf machine would be even more inefficient.

So...while hanging around the pub one day I set out to reinvent the air conditioner.

Let's start not with a 3000 watt machine, or even a (say) 300 watt machine that would be arguably sufficient to cool Jack and Dah when they are sleeping. Let's start with the bench machine above, which I built for a couple of hundred baht, a one-watt air conditioner, which meets the following specifications:

cooling capacity (mostly latent): 1 watt
condensate, cc/hr: 1
unconditioned air water vapor entering machine: 20 g/cubic meter
conditioned air water vapor exiting machine: 8 g/cubic meter

Operation of this machine requires about 3600 joules of energy per hour, which can be easily provided by only about 10 grams of ice.

The question: can we effectively scale up, say by a factor of about 300? This would require about 3 kg of ice per hour--seems doable.

Aircon fantasies

In times of general retreat I spent hours fiddling with air-conditioning ideas. Solar powered desiccants. Micro air conditioners like they used to cool yachts and space men and NASCAR racing drivers. I went to the annual southeast Asian air conditioning trade show at the Sirikit convention center. Eager Chinese salesmen filled my arms with lavish brochures. The brochures showed their company president, tan, fit, and shrewd, perfecting his golf swing. China was clearly the future of air-conditioning manufacture.

But what I wantedI couldn't find. That was, a device that would condition air for a couple of people, not cool a big leaky overheated Thai room that delivered 2000 watts of heat from walls heated by the afternoon sun and steamy outside filthy air through window framwes that didn’t fit right. I knew he was on the right track when I went to visit the Carrier office in Bangkok. They somewhat reluctantly sent an engineer out to talk to this fahlang with the short pants milling around the front desk. Could they offer small units, maybe 5000 btus or less, asked I?

"What you want for?" the engineer asked, his eyes narrowing suspiciously.

“For small room, maybe twenty, twenty five square meters.”



The engineer whipped out a calculator and pecked in some numbers. Multiplying something by twenty five. No wonder people are annoyed by engineers, I thought to himself.

"Twelve thousand. "

"Twelve thousand what, for what."

" BTU for room."

I said that I was amazed, amazing thailand, I said, that he could do this so quickly. He must have a very good college degree. I thanked him for his time in a rather exaggerated way that he hoped conveyed the general idea. This was a Thai trick he had learned.

*********************************

I thought some more on this subject that I was clearly thinking about too much.. This is what I am looking for, I thought:

The system would cool a large fahlang body, and maybe Dah too if Jack could ever get it together with her. It would cull a small space that was reasonably protected against radiant, convective heat transfer and moisture infiltration, either convective or diffusive. Maybe like a tent. I drew a sketch.


The air within would be dry, say 40 percent RH but not too cold, so maybe there would be some heat transfer between the incoming and outgoing air. The capacity would be only say 500 watts or 2000 BTUs per hour, half the size of a small US style window unit, 20 percent of the one that Mr. Wonton said was necessary because it was the smallest the Carrier company made. The electrical savings for say six hours of operation of a 2000 btu unit would be a dollar fifty a day. Half a million air conditioners were bought in Thailand every year. The space to be cooled would be small, maybe 25 cubic meters altogether, and the envelope would serve as a mosquito barrier as well. The air would be conditioned air would be ducted into the space silently.

And wouldn’t it be nice to power the whole thing with exactly that dreadful stuff that was causing the whole problem, the 1000 watts per square meter, that would be 36 kw of power, of sun power burning down on that hot red roof? Maybe putting all that heat into the ground or say a lithium salt solution or some ammonia like the old days under the house or hidden away in the garden and some of it into the cool 26 degree water that came in off the street so the shower would be nice in warm in the cool season when the sky is clear and the solar at a maximum?

They would call it the "Ron Swelters Quarter Ton Aircon Machine", dedicated to His Majesty the King who had shown a keen interest in energy savings, and also to Doctor Carrier who invented the first air conditioner to cool the fevered brows of malaria victims but who had been swindled out of his rewards by John "Ice King" Tudor. In the year 1831, it was.

This was getting good. I ordered another pint, it was three minutes before seven and the price would double if I didn’t, the waitress told me so.

***************

The following night I had dinner with Jack and Dah. I told them all about my air conditioning ideas.

"Oh, Khun Jack, that very good. "

Jack thought this would be a good time to sort of pop a question.

"You know, Dah", he said, "we have to make an important decision. W can do it with only 1000 btu. But maybe I should get extra, maybe 2000 btu. Just in case maybe things different in the future."

Dah considered this.

"I think you and Ron know best about this. We need more money in account."

End of the rains?

Could this be it, the end of the rains?

Last weekend a great flood in our neighborhood, a day confined to home with two feet of dirty water in the streets, local kids swimming happily in the sewage. Dek Sa-lum, says Auntie Porn, our Isan cleaning lady.

Now this week the days feeling cooler in the morning, no more than a few weak drops of rain in the late afternoon. It just feels different. Notice the wind heading from the west to east, then changing to the north, this was the beginning of the different feel. Dah says that winter has come. (Though the night temperature of close to thirty is still a little warm for this fahlang.)

Index of pages

A long way from home	1/1/2007
black hole	1/1/2007
Greasy black dust	1/7/2007
2007/07/first-night-tropical-paradise.html>	1/10/2007
by Ron Swelters " align="left" height="17"> 2007/07/that-april-thrill.html#comments> by Ron Swelters	1/10/2007
2007/06/here-is-my-story_25.html>	2/28/2007
2007/06/same-heat-every-year.html>	3/1/2007
Tropical Cool: How was it for you?	3/6/2007
Tropical Cool: Hot roof unmitigated(revised)	3/9/2007
Tropical Cool: Solar-heated concrete roofs	3/10/2007
Tropical Cool: Foiled by the foil	3/11/2007
Tropical Cool: Carrier's magic chart	3/12/2007
Tropical Cool: Tour the world's most uncomfortable cities!	3/15/2007
Tropical Cool: Why so hot at Don Muang?	3/17/2007
Tropical Cool: Keeping cool without sweat	3/22/2007
Topical Cool: Bangkok 's lovely breezes	3/23/2007
Tropical Cool: You probably don't vent enough	3/27/2007
Tropical Cool: Big open windows	3/28/2007
Tropical Cool: Fans and turbines for a hot afternoon	3/29/2007
Tropical Cool: A hat for her apartment	4/1/2007
Tropical Cool: When will the heat break?	4/3/2007
Tropical Cool: An escape from romance	4/8/2007
Tropical Cool: Worst night yet	4/8/2007
Tropical Cool: A two-hundred foot tree	4/15/2007
Tropical Cool: Local wisdom, upstairs/downstairs	4/20/2007
Tropical Cool: How cold that night sky	4/22/2007
Tropical Cool: Regional heat agony today	4/24/2007
Tropical Cool: My fan's fan Apr 27, 2007 352	4/27/2007
Tropical Cool: Cold exceptions prove the hot rule Apr 30, 2007 298	4/30/2007
Tropical Cool: Banish unsightly necksweat! May 08, 2007 320	5/8/2007
Tropical Cool: Hungarian attack on US hegemony May 11, 2007 316	5/11/2007
Tropical Cool: Are the Thai really different? May 13, 2007 508	5/13/2007
Tropical Cool: Enter humidity May 21, 2007 308	5/21/2007
Tropical Cool: Thai comfort II (the mysterious orient) May 25, 2007 297	5/25/2007
Tropical Cool: Is a hot tin roof cooler? Jun 10, 2007 249	6/10/2007
2007/07/hatless-in-bangkok.html>	7/30/2007
2007/07/waning-heat-of-summer.html>	7/31/2007
2007/08/hot-tin-roof.html>	8/1/2007
" align="left" height="17"> 2007/09/old-spice.html#comments>	9/24/2007
2007/09/normal-year.html>	9/24/2007
one watt aircon	11/3/2007
aircon fanatasies	11/3/2007
IN the cool of the pub	11/4/2007
Cool night roof	11/12/2007
Would you mosquitoes mind leabving	to add from thaivisa
Out of Africa	to add from thaivisa
Rain and the mud	to add from thaivisa
Tropical Cool: The dream and the dread	x
Tropical Cool: That April thrill	x
Tropical Cool: Hot tin roofs and fahlang sweat	x
Tropical Cool: Night heat in June Jun 15, 2007 257
the air from Isan--november	12/1/2007
change your perception of (proust)	11/26/2007
index	10/1/2007

Old Spice

Last year the makers of "Old Spice" deodorant for men published the results of a study of the "sweat rankings" of American cities. The winner was Phoenix Arizona but Texas cities like Dallas and Houston and several Florida cities were right up there and since I've always had a bad memory of Houston I'm going to use that place as a kind of bench mark, to compare Boston and Bangkok.


Take a look at the "march of temperature" through the seasons in three cities: Boston, which had a famous heat wave the first few days in August, 2006 (pink circle), a hundred thirty six people died including one woman sitting inthe bleachers at Fenway Park; Houston, which as I said seemed to me to be really awful, and Bangkok, awfuller yet. The red points are the highest temperature of the day, the green the highest dew point temperature of the day (more on that later). When the temperture is more than 30, you will begin to sweat, even if you are just sitting looking at this blog.

As you can see, that's most afternoons in Bangkok (the daily high is usually at about three o'clock).

You might say that Boston heat wave got up as high as Bangkok, but even thoughthey were passing out cold water on the half deserted Boston streets you could still sweat pretty effectively there because the dew point temperature was low, down around 24. In Bangkok, in contrast, the dew point hardly gets below 26 most of the year, so all that sweat just soaks your shirt and hardly cools a body at all.

Normal Year?

A couple of weeks ago a Thai lady said to me "The heat hasn't been bad this year, a couple of weeks in March or April, then the rains cooled things down and it hasn't been bad since."

This lady happened to be an experienced architect, and my sense of the year agreed with her comment, but as a "quant" I felt compelled to look at the data, so I loaded Don Muang daily highs (temp and dew point) and superimposed on the hottest year I've found, which happens to be 1983. To my surprise this suggested that 1983 wasn't really so bad after all, except that the hot season got a little prolonged (so it just kept getting hotter) and then finally broke with the rain which (if I am right in my thinking) came a little late. I also believe that 1983 was a bad flood year, so now I wonder wheher al these things are tied together.

Hatless in bangkok

It was getting into late July now and to my delight the weather had become tolerable and even pleasant. I had feared the sun and brought from California an excellent straw hat, designed and branded in Australia, made in China, and bought by me in a sporting goods store for five dollars and ninety eight cents. The shading and ventilative features of this hat were excellent, but it was more than a nuisance to carry, and I began to notice that I really needed it only a few minutes every day. I had, for one, found that I was not venturing abroad for vigorous midafternoon walks as I might in America, and even then the sun did not shine much of the day, the sky filled with rapidly changing clouds, now mild and oyster colored, now blackish and turbulent. Soon enough I left the hat somewhere, I think in a movie theatre in Siam Square where they occasionally showed films that met my discriminating tastes.

I determined to design a better hat, since all that I was able to find in the markets were intolerably hot except during those very occasional and fleeting moments of fierce overhead solar radiation, for the Bangkok sun since April and until August was almost directly overhead. Extreme portability and low value were the principal design criteria for my hat; I thought that a small napkin-like folded paper disposable might do the trick, but I grew weary of trying to find the right materials and one day stumbled in desperation on the expedient of cutting a sleeve from an old T-shirt and gluing the end opening with ordinary carpenters glue. This worked well, I eventually made half a dozen, and though it might be said to have created a somewhat odd appearance I reasoned that foreigners were universally taken by the natives to be both odd and correct. I have never noticed even when shooting my most darting looks at the locals passing on the streets the slightest hint of derision from anyone.

But were it not for the impractical bulkiness for city wear, the traditional Thai farm hat, or muak, is clearly the winner, allowing for full shade and full circulation of air on your sweaty head.

Waning Heat of Summer

To my delight, the temperature moderated over the summer because of the rains, not at all unpleasant, crackling thunderstorms that might appear at any time, dawn, mid-day, most often in the late afternoon, everyone scurrying for shelter where girls had plenty of time to give you a lookover, then the black clouds would open and the dazzle would come back.

I downloaded the daily high temps for the year so far(blue), superimposed them on a speciment year fro the past (red) and it became clear that thought the sun was still hovering around in the middle of the sky, the cooling bath of rains was causing the temp to drop over the summer months. For that matter, it appeared that if you hated heat, the time to avoid in Bangkok was March through June.

That April Thrill

So my brother calls me on my new Thai cellphone.

"That's fine, your first effort, but what are you talking about women for? You're supposed to be writing about the tropical weather, how foreigners can learn to live with it, help me figure out how to stay comfortable in this house, not about going to bars and women, for God's sake. Try thinking like the M.I.T. student you once were, not like an adolescent."

He's talking about my new blog, he doesn't like the way I'm going on this thing. Annoying, but he did help with my ticket here. I'll try to get back on topic.

The sun. That's a good place to start, our ancient enemy, the sun.

The Sun

Most people don't know it, but down here in the tropics we've got two "hottest" days of the year, not one like back up north. Wintertime, the sun is down there in Australia, giving skin cancers to all those pale blokes who live at the tropic of Capricorn, 23 degrees below the equator. Around the end of the year, even at noon the sun is fairly far off vertical in Bangkok, in fact this picture of a lady at Asoke BTS station (a burning hell of a place in general) at noon shows that the sun is at 53 degrees. Makes sense, when you think that Bangkok is about 13 degrees above the equator, so

90-(23+13)=54 degrees (OK, it's not exact)

Notice something else about this picture, that lady is carrying an umbrella. In winter. She doesn't want any part of the sun, she's even holding up her shopping bag to keep out any little slivers of sunlight.

This is typical of the people here, Thailand, Malaya. They hold up their arm to show you," I very black skin," they say. You say "O I think beautiful skin, I wish I had the same." They smile, thinking "fahlang very polite, they always say this but not believe." That night they put on extra skin whitener, which is about as effective as "anti-aging cream."

Tons of the stuff sold in Bangkok every day.

It's a system, the old Khmers had it all figured out nine hundred years ago, they learned it from the Indians.works like this, the sun gets to be right overhead in April, starts to decline a bit to the north over the summer, then in August back again. On April 29 and again on August 13, you throw no shadow at noon.

You can make a graph of the relative intensity of the sun on a flat surface at noon, it gets up near 1000 watts a square meter in april and August. You can compare the relative intensity with other places, like Miami and Boston, as I've done above.

Now I got my hands on a large set of data for Bangkok weather, must be from the old Don Muang airport, and I made a chart showing the daily high temperature and dew point for the years 1982 to 1985. And the yellow line is an accurate plot of the graph above, the relative noon intensity of sunlight falling on the unshaded ground at noon on the same day.

You'll not be surprised to see that the daily high temperature starts out nicely in the beginning of the year and then as the sun gets progressively higher in the sky, the dawn heat builds with it month by month, now in the beginning of March it's getter pretty sweaty even when I get up to walk to Starbucks early, and it's going to get worse, maybe a lot worse, some people say that this will be the big one this year in April, toward the end of the month.

But then, look, there in late April or early May, when the hot tension has built to a peak, and the people are dancing around and throwing water on each other but especially on fahlangs, and they used to have these wonderful rites with lingas -- you know what they are, don't you? -- the lingas spurting water and everyone is saying "Ahhh..." or as they say in Thai "Ooooiiiiyy........"

And then everybody gets this terrific little kiss from the gods.....

Or at least it seems terrific to them. As far as the folks from Boston are concerned, it's still one helleva big heat wave for the next six months, til November.

Same heat every year?

Brother jack let it be know that Bangkok's horrible heat and humidity was the game, and that he expected solutions from me. "You're the guy from MIT," he said.

I had a couple of days before leaving and instead of buying gift chocolate figurines of Mickey Mouse or Parodi cigars as gifts for all the people I was going to meet I went for the UCLA library and loaded up on data. I found a huge collection of Bangkok weather data from some American military spy agency and almost missed my flight transferring all the files to a CD.

Our ultimate concern here is the weather within a room, or between your shirt and your skin, not the world at large. Although we are not particularly interested in grand questions such as global warming or pressure ridges in China -- I know nothing of these matters -- one of the first things that I asked myself was whether the weather, or more specifically the heat, which is my enemy here, is always the same in Bangkok, year by miserable year.

This extract from my massive data file (which you can have, for free, if you have some good purpose)gives a quick answer to this question. It shows the daily mid afternoon temperature, which is almost always the hottest temperature of the day, for fifteen years, starting in 1982.

Given that you are going to start to sweat at 30 degrees even at rest, you can see that a brisk walk at three pm is not going to be enjoyable.

Especially if it happens to be 1983.

But will jogging be more pleasant at six in the morning?

Night heat in June

We saw the other day that in theory the roof on brother Jack's house retains a critical amount of heat resulting in a room temperature that is two or three degrees higher than the outside temperature -- enough to make the difference between a good and miserable sleep.

How does this check out in practice?

Here you can see my notes from a recent stay at the house. I measured the temp of the interior wall surface with a radiant thermometer until about 3 am, at which time the outside air temp was about 29 and the interior temp hanging up at 31 -- too warm for comfort (the orange colored zone). This was a pretty typical June night (June 8, 2007) ending with a dawn temperature of 27 to 29, (dawn temp also happens in almost all cases to be the daily minimum.). This matches the experience that Jack has been reporting, too hot in room in the middle of the night many nights in June. (It doesn't help that Dah insists on closing the windows at night for fear of intruders).

The interesting thing here is that the the discomfort comes from only a small amount of temp elevation. If we can drag the temp down just a couple of degrees, we will be as happy as the farmer sleeping under a cool nighttime tin roof. The challenge is this-- how can we get this modest amount of cooling without resorting to the overkill of air conditioning?

Is a hot tin roof cooler?

Interestingly enough, the answer might be yes if we are talking about the time that matters most to many folks, that being at night when the outside temperature is slowly falling from the low thirties (too hot!) to the upper twenties (reasonably cool for sleeping). A "tin" (galvanized iron) roof is fairly light, perhaps a kilogram per square meter and has a very low "R" value. So hot as it might be even at sundown, it quickly cools to the ambient air temperature, even two or three degrees below if the humidity is not too high and the effective sky temperature is low, say 5 degrees or so. So you may even get some free radiative air conditioning from such a roof at night.

Lets look at Brother Jack's roof:

This roof weighs about 10 kg/sm and has an "R" value of about 5, and each square meter retains perhaps 10,000 joules of heat per degree. If you want it to cool as fast as the outside air, say 1 degree per hour, you've got to make it discharge 10,000 joules per hour per sm, or 3 watts/sm. If the "R" value is 5, this will require a temperature gradient across the roof from inside to outside of about 3 degrees. In other words the interior temperature will be 3 degrees higher than the outside air temperature--which is what we saw earlier on our April 3 measurements (vertical difference between red and blue lines). Therefore even when the outside air dips to a nice 29 degrees, the inside of the room will still be a sweaty 32 -- too warm for sleeping. And if in your desperation to keep cool in the daytime you had installed some bulk insulation instead of the foil insulation, the "R" value might be double, and the required temperature to push 3 watts out through the roof even more, maybe 5 degrees, an even worse situation! Meanwhile the poor farmer next door will be happily snoozing with his tin roof at or below outside air temperature! His red line will closely track the blue line, maybe be even lower.

So the joke is on you, Mister high-tech fahlang--you tricked nature in the afternoon, but she got back at you when you were trying to sleep!

Thai comfort II (the mysterious orient)

Ron: So Dah, do you think Thai people feel the heat the same as fahlang? Sometimes when I feel very hot my girlfriend also says "very hot" too.

Dah: Thai people say "Oh very hot" but just start the conversation, that all. It not about real hot. Actually it not bother them. It just the way it is. After you born it like this, no one can change. Even you go to hospital and doctor there make mistake, you have to think maybe I do bad last life, that's why I get. In America if someone do something bad, you have to sue him to get something back. But in Thai they think maybe last life I do something bad to them.

Ron: I see. But Jack told me last few days you were complaining about the heat at night. Were you just making conversation?

Dah: No, it about the flea, that bug, I don't know if flea or not. It bother me. Not the heat.

A long way from home

I grew up in New England.

The summers, especially the "Dog Days of August" were sultry; the fall was crisp and delicious, and then the "frost was on the pumpkin" and the rains came and then the howling "Nor' Easter" storms that closed all schools, we heard the good news on the radio in the morning. Serious businessmen like my father trekked through the drifts to work anyway, never missed a day.

Boston as always thought the best of itself and everyone said that the vigorating seasons were what made people alert and industrious, compared, for example, to Mexico, where everyone slept away the day, and Havana, God knows what they did down there. But then you'd think about that, whatever they did do down there, maybe it wouldn't be so bad after all, the warm wind on the Malecon and the bar lights twinkling and one night when I finally went there to see what was going on I went into one the bars and there was a juke box playing Nat King Cole and a couple of girls sitting at the bar and...well that's another story. The funny thing is, my father, the serious busibnessman, once had a Cuban girlfriend. But this was the tropics, people ran away to places like that, it was hot and sticky and sweating far into the night, the weather just did things to you. Made you irresponsible.

But getting back to Boston, as soon as the days that my mother called the "dog days of August" were over, bright and sparkling September came along and I walked to school kicking the yellow and orange maple leaves. I loved that weather, the smell of those leaves burning in the fall. Halloween was just around the corner, and then soon enough the "frost would be on the pumpkin."

But all of that was half century ago at latitude 42, and aside from my nightly film festival of dreams of those sparkling times and those Kodachrome neighborhoods, my days now, and probably all my future days, will be at a very different latitude, latitude 13. Think Djibouti, or Cape Verde, or the Marshall Islands, or who knows where in Africa.


Now I live a long way from home.

Think heat.

Think humidity.

Or think Bangkok, Thailand, where I am writing this entry, waiting for the sun to go down, then I'm going out into this traffic you see here, and do some things I'll discuss later in this blog.