THE PYRAMIDS of the COLD • Chapter 03 The really-not-horizontal flash-evaporative cooling passage and the expansion joints

In summary: the so-called horizontal passage of the Great Pyramid of Khufu was designed to transform pressurized liquid water produced inside the inclined well by the fall of a composite piston-like impactor, into a fog of microdroplets of liquid water that would evaporate and naturally create flash-evaporative cold; most probably the Queen's chamber could have reached temperatures as low as zero degree Celsius (32 °Fahrenheit) or even -10 °C (14 °Fahrenheit) depending on the capacity of the central wooden Djed caisson in the Grand Gallery to generate a strong overpressure throughout the entire cooling system.

The cold would be stored into the Queen's chamber, the only chamber of the Great Pyramid at the center of the gigantic structure, where a copper plate cold exchanger was most probably set and would have allowed the cooling of a Solvay-like ammonia-soda process chemical manufacturing of sodium carbonate (the purest mineral form of natron, the salt used for the mummification of the pharaohs), and sodium bicarbonate.

The thing is that if you're looking at the design of the Great Pyramid without any pre-conceived ideas, and in particular the horizontal passage, clues are literally everywhere: how come nobody have ever understood that the large, continuous and vertical joints in the first 64 feet of the passage, filled with tar or resin, were expansion joints? How come nobody ever linked these joints with the presence of massive salt encrustation, completely specific to this part of the Pyramid? How come nobody ever realized the so-called horizontal passage actually has the exact same slope as an ancient or modern aqueduct? Am I the first one to really look at the Great Pyramid with a complete open mind?

Modern evaporative coolers' biggest problem is salt deposits; it is called encrustation, and it is exactly what had been documented in both the horizontal passage and the Queen's chamber of the Great Pyramid: hard and up to one-half inch thick incrustation of salt, specific to these two very particular parts of the pyramid. Unfortunately, this proof of the evaporative cooling process had been cleared out in 1998 by Zahi Hawass. Because of this unfortunate salt deposit cleaning, it probably is impossible today to precisely determine how cold did it get inside the Queen's chamber as well as how long was the Great Pyramid operated for such cold production.

[illustration] The continuous spray water bottle is a near-perfect model for the operation of the flooded part of the central wooden Djed caisson that was located both in the Grand Gallery of the Great Pyramid (the aerial part of the pressurization system) and in the inclined well of the Pyramid (the so-called “ascending passage” that was the flooded part of the pressurization system at the origin of the pressurized water absolutely necessary to the production of the fog of microdroplets of water that triggered the creation of flash-evaporative cold). Source: GoSupps

Operating diagram of the Great Pyramid of Khufu, showing the so-called 'horizontal passage' which actually has a slope of 0.3% over a distance of 32 meters (0.3% is by the way, the average slope of Roman aqueducts).

03.01  The starting point of the study: the specific layout of the horizontal passage that points to cold production

It actually is because of the horizontal passage and its very specific layout, that I started to understand the real function of the Great Pyramid of Khufu, and its involvement in cold production, because when I was younger, I used to have a very basic air cooler, and I was already intrigued by it. I was so intrigued that I did some experiments on it, measuring the difference of temperature at the entry and at the exit of the cooler. So, I was aware of the evaporative cooling process capability since maybe 2008, and when I started to interest myself in the Great Pyramid in 2021, I'm sure it helped a lot.

[The above photograph is about an air cooler, that uses the same basic evaporative principle to create cold as the flash-evaporative cooling, but this is very important to keep in mind that the air cooler isn't very effective at all: the air cooler only uses plates soaked with water and doesn't create the fog of microdroplets of liquid water that is specific to flash-evaporation] "What is an Air Cooler, and How Does it Work". Evapoler: https://www.evapoler.com/what-is-an-air-cooler-and-how-does-it-work/

03.02  The whole study can be summarized as: "how the hell did ancient Egyptians were able to produce flash-evaporative cold, 4,500 years ago, without access to electricity or any kind of motor"

If ancient Egyptians designed an entire layout to resist to thermal stress, and there is no trace of any damage caused by heat, the only logical reason for this layout has to be related to cold production, even if the whole thing is taking place at the very heart of the Great Pyramid. That is the breakthrough. Cold is the breakthrough and the entire Pyramid was designed to produce that cold. But once you have understood this, the real challenge actually begins: how did ancient Egyptians managed to create that cold; such intense and brutal cold that they had to protect the structure from it? That's what all the study of The Pyramids of the Cold is all about.

03.03  The surprising efficiency of the evaporative cooling process that created cold in the horizontal passage of the Great Pyramid of Khufu, is still used today in modern evaporative coolers

What’s really important to understand, is that the evaporative cold that was used in the Great Pyramid, was not just a damp cloth or bowl of water evaporating in the air: Egyptians used flash-evaporative cold, which is much more efficient than regular evaporative cold. The trick is to produce as many and as tiny little drops of liquid water as possible so that the evaporative process could be almost instantaneous and all the liquid water used really participate in the process. Egyptians simply used water to its maximum  refrigerant potential while we, in our modern world, used different refrigerants. But the principle is the same; we didn’t pushed water used as a refrigerant to its limit, but Egyptians did.

Not only did they use flash-evaporative cooling, that needs the creation of a fog of microdroplets, but they also did something else: instead of working at atmospheric pressure (this is called an adiabatic process), they pressurized the entire cooling passage and the Queen’s chamber, by the use of the central wooden Djed caisson. Before the impactor hit the waters of the inclined well and pressurized that water, the air trapped into the caisson was first pressurized as well; and even if the first reason for that was to replace old moist air of a previous cooling cycle, it also pressurized the whole system.

So, the question now would be to estimate the real final pressure that was reached in the cooling system, understanding that the pressurization only occurred every 15 minutes or so, probably for about 10 seconds or so, and of course the final temperature of the Queen’s chamber after the end of each cycle.

"Evaporative cooling exploits the fact that water will absorb a relatively large amount of heat in order to evaporate (that is, it has a large enthalpy of vaporization). The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration."

"Evaporative coolers lower the temperature of air using the principle of evaporative cooling, unlike typical air conditioning systems which use vapor-compression refrigeration or absorption refrigeration. Evaporative cooling is the conversion of liquid water into vapor using the thermal energy in the air, resulting in a lower air temperature". https://en.wikipedia.org/wiki/Evaporative_cooler

Evaporative cooling applications webpage screenshot: AquaFog® from Jaybird Manufacturing Inc (Pennsylvania, USA).

03.04  The Queen's chamber was the cooling chamber where the cold was stored: it needed perfect thermal insulation and required that chamber to be 'in the center of the Pyramid'

There is another thing egyptologists don’t really want to talk about: if Egyptians designed the Great Pyramid as a tomb for Khufu, why didn’t they build the so-called King’s chamber in the center of his Pyramid? Why is his chamber offset, and why is it the Queen’s chamber which is the only chamber of the Great Pyramid that has been built on its central axis?

“As you can see, the Queen´s chamber is the only (known) chamber in the Great Pyramid which is located exactly in the midline of the south-north direction. Petrie did the same observation and added some measures: ‘41. In the Queen's Chamber it seems, from the foregoing statement, that the ridge of the roof is exactly in the mid-place of the Pyramid, equidistant from N. and S. sides ; it only varies from this plane by a less amount than the probable error of the determination. The size of the chamber (after allowing suitably in each part for the incrustation of salt) is on an average 205,85 wide, and 226,47 long, 184,47 high on N. and S. walls, and 245,1 high to the top of the roof ridge on E. and W. walls. The variations of the horizontal quantities in detail are as follows, from the mean dimensions.’ Stefan A. H. Holmgren: https://khufupyramid.dk/inside-dimensions/the-queens-chamber

Vertical elevation of the lower (northern) end of the Grand Gallery of the Great Pyramid of Giza, showing the joint-lines in the Western and Eastern walls, and in particular the continuous expansion joints (red arrows) that are suggesting thermal stress was applied on the structure: that is constraint due to a sudden and significant change in temperature.

03.05  The structural anomalies of the first 64 feet of the horizontal passage: small blocks, symmetrical design, poor structural rigidity, large and continuous vertical joints filled with resin or tar

The first 64 feet of the so-called horizontal passage of the Great Pyramid has puzzled many egyptologists, because clearly it hasn’t been built with any structural concern at all: the blocks are very small, everything is completely symmetrical and the joints not only are very wide and continuous, but they’ve been filled with some kind of tar or resin.

Everyone has heard at least once in his life that the Great Pyramid has been built with gigantic blocks, so nicely crafted you couldn’t even slide a sheet of paper between the blocks; and indeed there is no mortar that has been used: the blocks, at least the ones we can see in the chambers and passages of the Pyramid, are ‘face to face’. There is no mortar used in the King’s chamber, in the Queen’s chamber or in the Grand Gallery, and there is no mortar either after the first 64 feet of the so-called horizontal passage; so why is it there? And why isn’t it regular mortar, but some kind of resin or tar that has been used?

"As I indicated in a former letter, the masonry of this Horizontal Passage is very symmetrical. For a length of about 64 feet from the beginning of the roof at the Grand Gallery end, each wall is built in two equal courses. In each of these courses there are 15 stones of one uniform size, namely, 41*4 inches in length, and half the height of the passage in breadth — Plate IX. The vertical joints in the upper course are in line with those in the lower ; and those on the east are in direct opposition to those on the west wall." Great Pyramid Passages Vol 1, 1910 edition, by John and Morton Edgar, paragraph ref. 583, page 293: https://archive.org/details/GreatPyramidPassagesVol11910Edition/page/n301/mode/2up

"One more detail from Dormion: some blocks of this part of the horizontal corridor have a wider gap in between (2-3mm). The external part has been filled by mortar, while the internal part by something black and rubbery, maybe coal tar or vegetal resin. Also the first part of the floor is atypical: the blocks are narrow and often side by side, showing a poor structural rigidity, almost a propensity to warp (dis. G19). These details may show the purpose of the architect." Source: https://www.greatpyramidexplanation.com/easyUp/file/10_07_horizontalcorridor.pdf

Elevation at different points in the horizontal passage and Queen's chamber of the Great Pyramid, revealing an elevation loss of 3.8 inches between the start of the collection ramp (858.4 inches) and its end (854.6 inches). [source] "The pyramids and temples of Gizeh", by Petrie, W. M. Flinders (William Matthew Flinders), Sir, 1853-1942. Section 40, page 66: https://archive.org/details/cu31924012038927/page/n103/mode/2up?view=theater

03.06  The almost 32 meters long collection ramp with a 0.30% slope

The 0.30% slope of the so-called horizontal passage of the Great Pyramid created a 32 meters ramp that would have collected and redirected the part of liquid water that didn't evaporate toward the basin of the Queen's chamber. Length of the collection ramp: 1307 - 52 = 1255 inches, or 3187.7 cm.

Elevation loss of the collection ramp: 858.4 - 854.6 = 3.8 inches = 9.65 cm. Slope: 3.8/1255 = 0.30%

The 0.30% slope of the so-called horizontal passage of the Great Pyramid created a 32 meters ramp that would have collected and redirected the part of liquid water that didn't evaporate toward the basin of the Queen's chamber.

03.07  The 0.30% slope of the so-called horizontal passage is the exact same slope than the one used in ancient or modern aqueducts

The elevation loss is 3.8 inches, between the beginning of what could be called a collecting ramp (that starts at an elevation of 858.4 inches) and its end (elevation 854.6 inches). 

Just to put the 0.3% slope of the flash-evaporative cooling conduct into perspective and because the only purpose of this ramp was to redirect the liquid water that didn’t evaporate towards the basin of the Queen's chamber: “Since the aqueducts were operated by gravity the course of the channel had to be carefully planned so that it would maintain a steady slope. A steep gradient was avoided, since faster flowing water would erode the channel walls and threaten the stability of the structure, especially at bends. These constraints would have affected possible courses the aqueducts took. Vitruvius gives a figure of 0.5% as an ideal angle of descent, but in practice this varied considerably, the average gradient usually lying between 0.15% and 0.3%, due to the constraints of geography.” From a thesis by Evan J. Dembskey: http://www.romanaqueducts.info/picturedictionary/pd_onderwerpen/surveying.htm

And from another source: “The slope of the aqueducts [in ancient Rome] ranged from 0.07% to 3.00%, with an average slope of 0.20%”: https://engineeringrome.org/the-water-system-of-ancient-rome/

Above illustration: “A rare look at a subterranean Roman aqueduct channel, this one built by the Roman army to bring water to Viminacium in modern Serbia. Despite the popular image of grand aqueduct bridges, most Roman aqueducts ran almost entirely underground.” Source: r/ancientrome

Construction of cooling chambers. "Zero energy cool chamber. Keeps the vegetables fresh for 2 weeks. Easy to construct. Low cost technology". By Safe to Eat Crop: https://x.com/SafeCrop/status/929633516228304899/photo/1

03.08  The fine sand lining discovered by Dormion and Goidin in the horizontal passage

Dormion was so intrigued by the first 64 feet of the horizontal passage and the continuous vertical joints, that he decided to drill holes in this first section of the passage, hoping to discover a hidden chamber, but we’ll see that the only hidden thing he discovered was sand! There is a huge amount of sand right after the first blocks in this part of the passage!

Excerpt from the Los Angeles Times article "Scientists Seeking Hidden Vaults in Great Pyramid Find Only Sand", written by Michael Ross, September 1986 : https://www.latimes.com/archives/la-xpm-1986-09-09-mn-12810-story.html

"A team of French scientists searching for hidden, treasure-filled rooms in the Great Pyramid of Cheops suspended work Monday after drilling three holes through an interior wall and finding only sand. But the French team and the head of the Egyptian organization supervising the work said they believe that the presence of a powder-fine lining of sand between the interior stones of the Great Pyramid supports their theory that secret chambers lie deep within the 4,600-year-old tomb of the Pharaoh Cheops.

“The sand means the ancient Egyptians are protecting something, something very serious and meaningful,” said Ahmed Kadry, head of the Egyptian Antiquities Organization. He said that although the French team failed to find and penetrate the cavities, samples taken from the wall beyond the sand lining indicate that it is made of a fine, soft limestone used by the ancient Egyptians for ornamental carvings on royal tombs. “We can be sure now that there are cavities, and not just structural or stress cavities but something much more mysterious,” he said.

The French mission, headed by Gilles Dormion and Jean-Patrice Goidin, two architects who postulated the existence of secret rooms in the Great Pyramid on the basis of architectural anomalies in the interior stonework, had hoped to bore four holes through the wall of a gallery leading to the so-called Queen’s chamber. The plan then was to observe and photograph the interior with an endoscope, an optical instrument developed for viewing the interior of human organs. However, the work was suspended after five days when, after boring three holes through more than eight feet of hard limestone, the drills hit the fine sand lining. Jacques Montlucon, an engineer with the French National Electric Company, which is providing technical expertise for the project, said the work was suspended because the drills being used are not suitable to bore through sand.

The existence of hidden chambers in the Great Pyramid has long been suspected, but there was never any real evidence until last May, when the French found what they said appeared to be three spaces, measuring 6 feet by 9 feet, off of the Queen’s gallery. The discovery, which the French said could indicate the presence of hidden storerooms, created a flurry of excitement among Egyptologists, who for the most part have assumed that all the treasures of Cheops were plundered long ago. Not all the experts share Kadry’s conviction that there are secret chambers, but discovery of a sand lining about 10 to 17 inches thick between the great stones is regarded as a puzzling and exciting find in itself."

03.09  The fine sand lining in the horizontal passage is because the passage was built like a Zero Energy Cooling Chamber

I first thought that the sand was here to reduce the thermal stress on the structure, due to the constant sudden changes in temperature that occurred in the first part of the passage, and maybe it also served this problem, but it was most likely essentially a thermal insulation, simply because the first part of the evaporative cooling passage was constantly exposed to the warmth of the Grand Gallery. Also, probably that same sand would have been set all around the entire structure of the horizontal passage and  Queen's chamber. After all, when the French team who discovered the sand behind the blocks, reported it, they were asked to stop their work right away. We don't know the entire extent of the sand casing behind the blocks.

"The complete structure of the Zero Energy Cool Chamber is almost finished: perforated water pipes have been installed onto the sand and are now connected with the water tank. Sand must be wet at all times for the evaporative cooling to be possible."

Constructing a Zero Energy Cool Chamber. By the MAMETI, Meghalaya Agricultural Management and Extension Training Institute, Upper Shillong, Northeastern India: https://mametimeghalaya.com/zero-energy-cool-chamber-zecc/

Large Capacity Fine Fog Nozzles, from Ikeuchi: https://www.ikeuchi.eu/news/pressure-and-flow-rate-in-spray-nozzles/

03.10  The horizontal passage was a flash-evaporative cooling conduct using pressurized water and a fog nozzle which have been glorified into the "Dendera Light" and the shower head-like lotus seed head

Now, it is time to talk about the most incredible discovery of the study: not only ancient Egyptians mastered flash-evaporative cold, and we did have the proof of this in the salt encrustation that have been found in the Queen’s chamber and the horizontal passage until it has been removed in 1998, but Egyptians also did something completely revolutionary: they used their scientific knowledge and technological accomplishments to legitimate themselves as the rulers of Egypt. And to do so, they glorified every single accomplishment of theirs, every piece of equipment and demonstration of technology by creating over 2,000 gods and goddesses. This is the most troubling discovery of the study: pharaohs created the Egyptian religion, and every single deity or religious idea is about science and technology.

Here, we have the first example of this glorifying process: to this day, the only certain purpose of the Great Pyramid was to create a fog of microdroplets that would produce evaporative cold, and of course Egyptians glorified this fog, and the fog nozzle as well: the Dendera Light is that fog, and the lotus flower from which is emerging the bulb is that fog nozzle.

The Dendera Light in the Hathor temple, is a representation of the fog of microdroplets of liquid water, transforming itself in vapor and by doing so, creating the evaporative cold. The Light Bulb shape of the Dendera Light is constrained by the shape of the horizontal passage. [Photograph of the Dendera Light] Kairoinfo4U: https://www.flickr.com/photos/manna4u/14525094039/in/photostream/

Lotus seed head thanks to Dinkum : https://commons.wikimedia.org/wiki/File:Nelumbo_nucifera_%28fruit%29.JPG

03.11  The up to one-half inch thick salt incrustation in the Queen's chamber and horizontal passage

The salt encrustation inside the Great Pyramid has been source of questioning since its discovery by the very first explorers in the 1800s and 1900s, but obviously egyptologists preferred to get rid of the problem in 1998 rather than seriously solving the problem.  Salt deposit has been mainly documented inside both the Queen's chamber where it could have been up to one-half-inch thick in some places, 1.3 centimeter, and in the horizontal passage; but to be exact some light deposit also has been noted in a smaller extent in the lower part of the Grand Gallery and 'somewhere' in the ascending passage. When you've understood the reason of the presence of this salt encrustation, you also understand the pattern of its distribution all around the exit of the horizontal cooling passage: cold simply spread from the cooling unit to the lower part of the Grand Gallery and the upper part of the ascending passage. There is no salt encrustation documented anywhere else in the Great Pyramid, and its distribution is perfectly explained by the evaporative process and the connection of the horizontal passage with the Grand Gallery and the ascending passage.

•  Excerpt from "Great Pyramid Passages Vol 1, 1910 edition" by John and Morton Edgar, paragraph ref. 584, page 293:  https://archive.org/details/GreatPyramidPassagesVol11910Edition/page/n301/mode/2up

"Following these uniform sets of 15 stones, are two long stones in each course, averaging about six feet in length, after which each wall is built in one course only, apparently as far at least as the drop in the floor of the passage ; but beyond this, on to the Queen's Chamber, the very thick and hard incrustation of salt which entirely covers the walls of this passage, made it impossible for us to locate the joints with any certainty. This salt incrustation is peculiar to the Horizontal Passage and Queen's Chamber, although a little of it may also be seen on the walls of the First* Ascending Passage." 

*For some authors, the first ascending passage starts at the granite plugs and ends with the start of the Grand Gallery, the second ascending passage.

• Excerpt from "The pyramids and temples of Gizeh" by Petrie, W. M. Flinders (William Matthew Flinders), Sir, 1853-1942: https://archive.org/details/cu31924012038927/page/n103/mode/2up

"The size of the chamber (after allowing suitably in each part for the incrustation of salt) is on an average 205 85 wide, and 226*47 long, 184*47 high on N. and S. walls, and 245*1 high to the top of the roof ridge on E. and W. walls."

03.12  Salt encrustation is the signature of the evaporative cooling process... even nowadays

Of course, the salt encrustation in evaporative cooling systems is not about table salt NaCl, but primarily calcium carbonate CaCO3 also called calcium scale, or limescale. With most of the pyramid built with limestone, this is not a surprise that limescale would have been a major problem.

From "Evaporative Cooler: Self Salt Clean", by Mohammed Ali Bahobail from the Department of Architecture and Building Sciences, College of Architecture and Planning, King Saud University, a Public university in Riyadh, Saudi Arabia : "Evaporative coolers are relatively economical, less expensive to install and to operate. They are consuming less electricity than a refrigerated unit, and they do not need an expert to maintain. In addition, evaporative coolers provide the building with a fresh humid air. However, evaporative coolers have some disadvantages; one of them is the deposited salt. Water usually has a high percentage of mineral. The evaporative mechanism will leave mineral deposits on the pads and interior of the cooler. This cumulative mineral will close the porous of the wetted pads and damage them and will participate to corrosion of the cooler frame." Source: https://cap.ksu.edu.sa/sites/cap.ksu.edu.sa/files/imce_images/jap_ksu_jan2013_e1_0.pdf

The work made by Mohammed Ali Bahobail is about coolers designed with wetted pads where water is circulating, there is no fog of microdroplets, but the principle is the same and the deposited salt problem is the same.

03.13  The dramatic and scandalous salt encrustation removal by Zahi Hawass in 1998

Unfortunately, the salt deposits have been removed since the first explorers of the pyramid reported its presence, when the chamber was cleaned by Zahi Hawass in 1998:

Zahi Hawass (Director General of the Giza Pyramids, between 1987 and 2002) : "Each visitor produces nearly an ounce of moisture with a high saline content through their breath and perspiration. This results in the accumulation of salt, which leeches into the limestone and plaster and gradually causes them to crumble into powder. So, in 1998, we spent 12 months cleaning the salt." Excerpt from https://www.world-archaeology.com/features/pyramids-excavation-and-preservation/

03.14  Salt deposits and the problem of the exponential growth of blog creation on the internet in the late 1990s

One can only assume that the decision to get rid of these tartar deposits was likely prompted by the realization that, with the exponential growth of blog creation on the internet in the late 1990s, egyptologists were losing their monopoly on storytelling, and that sooner or later, some amateur egyptologists or simply curious individuals started posting photos and videos of this tartar, asking the awkward question: what is all this tartar doing here, in this Queen’s chamber and the so-called “horizontal passage” leading to this chamber, and why is there no tartar anywhere else in the Great Pyramid, or in any other structure, pyramid or not, built by the ancient Egyptians?

“Blogging had its beginnings in the early 1990s. The term “weblog” was coined by Jorn Barger in December 1997, and was later shortened to “blog” by Peter Merholz in 1999. Prior to that blogging can be traced back to the early online diaries and personal pages that began to appear with the advent of the World Wide Web. Early blogs were simple websites where individuals could post updates about their daily lives, thoughts, and interests, serving as a digital extension of personal journaling. In the late 1990s and early 2000s, blogging platforms like LiveJournal and Blogger emerged, making it easier for people to create and maintain their own blogs. These platforms provided user-friendly interfaces that required no advanced technical knowledge. Anyone could start a blog and thousands of people did.” A Brief History of Blogging, by Mark McNease: https://markmcnease.com/2025/03/11/a-brief-history-of-blogging/

03.15  The stupid and outrageous incrimination of the salt deposits in the Queen's chamber on tourists

Mr Hawass is obviously blaming tourists for the salt encrustations in the Queen's chamber, but when the first explorers of the pyramid discovered these encrustations, there wasn't any tourist at all visiting the pyramid. The remark of Mr Hawass, is pretty funny though: did we ever had to periodically close down limestone built churches, cathedrals or any other pyramid or building made of this material (I guess in Mr Hawass' mind, limestone is a key element of the salt deposits in the Great Pyramid), just to remove the salt? Be that as it may, salt deposits were only documented in the Grand Gallery in its lower part (most probably just around the junction with the horizontal and ascending passages); did tourists stop breathing passed this point, and did they climb the gallery and visit the King's chamber in total apnea ? Were they offered respiratory masks ?

The cleaning of the salt deposits is actually a real drama, because before 1998 it was still possible to know exactly at what temperature the Queen's chamber was cooled down, simply by analyzing the crystalline structure of the deposits, the size and shape of the crystals.

The creation of a fog of microdroplets of water, at the origin of the flash-evaporative cooling.

03.16  To what temperature were the ancient Egyptians able to cool the Queen's Chamber down? The Zero degrees Celcius hypothesis

This is a fundamental and fascinating question. Unfortunately, since the salt deposits (scale) in the Queen's Chamber were removed by Zahi Hawass's team in 1998, we will probably never know for sure how effective the system implemented in the Great Pyramid was, since it would have been enough to measure the size of the crystals to determine the exact temperature at which they formed.

That said, we can make some suggestions. Personally, I think they managed to either get close to zero degrees Celsius (32 °Fahrenheit) or to descend to negative temperatures close to or below -10 °C (14 °Fahrenheit) depending on the capacity of the central wooden Djed caisson to generate a strong overpressure throughout the cooling system.

The big question is actually related to the fact that their cooling system was not at atmospheric pressure (it wasn’t an adiabatic process), but rather at overpressure thanks to the piston-like impactor falling inside the central wooden Djed caisson of the Grand Gallery. No doubt, in the years and decades to come, computer models and reconstructions, to some extent, will make it possible to get closer to the true initial performances, but unfortunately this will of course not have the same flavor as if we still had a few samples of this tartar, of which there is probably nothing left today. 

Evaporative cooling applications webpage screenshot: AquaFog® from Jaybird Manufacturing Inc (Pennsylvania, USA).

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Table of contents

Operating diagrams of the Great Pyramid

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Index