Table of Contents
The Perfect Library
A New Library
Air Conditioning JUL Central
Tailoring the Specs
Making It Work
Paul K. Conkin
Air Conditioning JUL Central
the label "air conditioning" usually refers to the cooling
of buildings in the summer. In 1939, as construction began on JUL
Central, the label had a much wider meaning, with cooling not necessarily
the most important component. Conditioned air then meant not only
air warmed or cooled to a certain temperature, but filtered air
with controlled humidity, all circulated uniformly in a building.
For libraries, two goals were of equal significance, the comfort
of people and the preservation of books. For the second goal, a
relative humidity of around 50 percent was critical, for very dry
air could crack the spines of books, very moist air lead to mold.
most difficult decision facing Kuhlman and the planning committee
in 1939 was whether to air condition the new central library. At
first, the principal architect, Henry Hibbs, plus most committee
members, believed air conditioning would be too costly. No other
libraries in Tennessee, and only two or three in the whole South,
had central air conditioning. The committee considered postponing
air conditioning, or possibly air conditioning only the reading
rooms in the two wings, hoping some of the cooled and dehumidified
air would seep into the central stacks. Hibbs feared the design
changes necessary to accommodate central air conditioning, and in
fact they would require almost continuous alterations in the original
construction contract. But from the beginning the committee at least
planned for future air conditioning. This meant duct work that would
accommodate air conditioning, insulation of walls, and double glazed
factor helped sway the committee in favor of air conditioning. It
was much easier and less expensive to incorporate air conditioning
in the original construction than to add it to an older building.
And, if JUL Central was to be a model library, a guide to future
library design, how could it do without the best possible heating
and cooling system? By May of 1939 the committee decided to take
the risk and procure a state of the art system. It would be just
that, for it decided to hire the ablest heating and cooling engineer
in America to design and supervise the installation of the very
latest in air conditioning technology. This was the best decision
the committee ever made.
E. E. Bryan.
as the committee debated alternatives, E. E. Bryan, supervisor of
buildings and grounds at Vanderbilt, began the search for the ablest
engineer. He also supervised detailed investigations of the average
heat and humidity in Nashville, and the direction and speed of summer
winds. Detailed climate charts awaited any prospective engineer. Bryan
wrote letters to dozens of experts, and soon found that a majority
agreed that the ablest engineer in this speciality was Charles S.
Leopold of Philadelphia. In ordinary times, he would not have been
available for what was, in effect, a rather modest project. He had
supervised the air conditioning of such large buildings as the capitol
of the United States and the Palmer House hotel in Chicago. But
in the depression such contracts were few and far between, and when
approached he eagerly sought the job. He did not come cheap. He
asked to receive ten percent of the cost of the air conditioning
equipment, and payment of all costs for his almost weekly trips
they were interactive, Leopold had to work out the specifications
for all the plumbing, heating, and air conditioning of the new library.
These were the basis of bids by various contractors. As Bryan had
pointed out to the planning committee, it was all but certain that
the Carrier Corporation would win the contract for the main components
of the air conditioning. It had a near monopoly in the field, and
had introduced a series of innovations in the late thirties that
shaped the system Leopold selected for JUL. In 1939 the Carrier
Corporation installed a new, experimental air conditioning compressor
for two buildings at the New York World's Fair. At the fair's closing,
this compressor was purchased by the Melrose Theater in Nashville,
meaning two very similar local systems installed at roughly the
same time. But Carrier only sold the basic components of its system-compressor,
condenser, and evaporator. Leopold had to solicit separate bids
for over a dozen electric motors, including the huge one for the
compressor, a bid won by Allis Chalmers.
series of discoveries had led to modern air conditioning. After
1931, these included all of the major components that, despite many
refinements, are still in use today. The cooling effect of evaporation,
and the warming effect of condensation, is at the heart of any air
conditioning system. As far back as ancient Mesopotamia, people
had learned to use evaporative cooling by forcing air through water
saturated cloth. In very dry climates, such a simple form of cooling
is still effective and inexpensive, but it does not control humidity.
The Romans collected and stored winter ice, and used it to cool
rooms, either by stacking it around the walls or blowing air over
it, with the risk of very high humidity. By 1850, the cooling potential
of evaporation led to the first ice making factories, and a lucrative
summer business. In this case, a gas (then usually a toxic and corrosive
ammonia) was compressed by pistons driven by steam engines. This
heated and condensed the gas. The resulting liquid, under high pressure,
circulated through pipes or tubes, where it was cooled either by
flow of air or water, and then allowed to escape through a pressure
valve into coiled evaporating tubes. The rapid evaporation of the
expanding refrigerant cooled the tubes to below the freezing point
of water, with large blocks of ice forming in areas surrounded by
the tubes. The same principle later allowed for the creation of
skating rinks, and by the 1920s to home refrigerators.
1902, Willis Carrier began the rather long process of using such
a refrigeration system to cool and dehumidify the air in buildings.
At first, human comfort was not a major concern. The largest commercial
market was for a system to control humidity in factories, such as
in textiles, which needed a constant high humidity (around 80%),
or others (paint, plastics, pharmaceuticals) which needed air as
dry as possible. To meet these needs, Carrier conceived of a humidity
control device that first made him famous, a devise that he would
refer to as "dew point control." It alone has led to his
recognition as the inventor of air conditioning (not, be it noted,
of either cooling or refrigeration).
Carrier's chilled water pipes.
new device continued in use until World War II, and was at the heart
of the system installed in JUL Central in 1941. The basic concept
seemed counterintuitive. Carrier decided that one could use a fine spray or mist of water to lower the humidity
of air that circulated in a building. If warm and moist air flowed
through tiny drops of very cold water, or something close to a fog,
these water droplets would create millions of condensation surfaces
(like a cold glass is a condensation surface). If the temperature
of the spray was below the dew point (the temperature at which air
is fully saturated with water vapor) of the circulating air, the
spray would condense some of the moisture out of the air. How much
depended on how much cooler the spray was than the dew point of
the flowing air. Thus Carrier gradually perfected an apparatus to
utilize this principle. He perfected brass nozzles that would emit
a fine spray into a dehumidifying box through which moved the circulating
air of a building. He calculated the temperature of the spray needed
to attain any given humidity. He used a standard refrigeration system
(compressor, condenser, and evaporator) to chill the water of the
spray to the temperature level needed to attain his targeted level
of humidity (usually 50 percent). In effect, the degree of chilling
needed for the spray determined how much compression, and pressure,
was needed in the refrigerant before it entered the condenser and
evaporator. In so far as the motor that powered the compressor could
vary its load to match the needed amount of compression and cooling,
Carrier had a type of thermostatic control over the whole system
and its energy consumption. Until 1920, almost all his installed
systems were for humidity control, not for human comfort. What he
needed was a more efficient compressor and, most of all, a much
better refrigerant than a very toxic ammonia.
had all of these by 1931. In 1922-23 Carrier perfected the first
centrifugal compressor, or what eventually became the standard for
large capacity air conditioning. All early refrigeration systems
had compressed ammonia by reciprocating or piston type motors. They
were not very efficient, but are still used in many small capacity
air conditioners. In them, the main shaft from an electric motor
has cams, which connect by rods to pistons within cylinders, much
like in an automobile engine. As the piston moves down in the cylinder,
it pulls in refrigerant, which is pressurized as it moves up and
released through a pressure valve into the condenser. Carrier's
centrifugal compressor was a turbine type, already used for many
water pumps. In it, the main shaft from the electric motor had attached
impellers (like blades on a fan), which rotate at a rapid speed
in order to compress air. Such a machine is simple, with no cams,
no rods, no pistons, but the speed of the impellers requires a very
strong mounting and casing. The impeller in the compressor for JUL
Central had a rotating speed of over 500 miles an hour at the outermost
rim of the compression chamber. Early centrifugal compressors had
two moveable vanes to control the flow of refrigerant though the
impellers, with less flow lowering the load on the motor (and thus
the energy consumed). Later compressors usually had multi-speed
motors. Such a compressor proved ideal for large, chilled water
systems, and matched up perfectly with Carrier's dew point control
late as 1930 Carrier had searched but had not found his perfect
refrigerant. He had replaced ammonia with a gas that contained chlorine,
but it was far from perfect. What was needed was a stable, non-toxic,
non-flammable, non-corrosive gas with a relatively low condensation
temperature. At first unknown to Carrier, chemists in the Refrigerator
division of General Motors, and then at Du Pont, had synthesized
a family of gases with just these properties by the mid-twenties.
We now refer to them as chlorofluorcarbons (or CFCs). Du Pont subsequently
registered a trademark name for the CFCs used as refrigerants-Freon.
Carrier began using Freon in his centrifugal compressors in 1931.
It would be forty years before humans began to realize that CFCs
help deplete our stratospheric ozone layer, which is the main barrier
to harmful ultraviolet radiation.
before Freon, air conditioning for human comfort had taken off in
the prosperous twenties, in commercial buildings but not yet in
private homes. By the mid-20s several factories both cooled and
dehumidified, most using the Carrier system. In 1922 a movie theater
in Los Angeles began installing air conditioning, and opened in
1923. At about the same time, three movie houses in Texas added
air conditioners and, with much publicity, so did the Rivoli theater
in New York in 1925 and just afterward a new Madison Square Garden.
The air conditioning of the Hudson Department Store in Detroit,
in 1924, was one of the first for a large, multi-storied building.
Even more publicity greeted the air conditioning of the House and
Senate chambers in Washington in 1928-29, with Leopold as the engineer.
By the beginning of the depression in 1930-31, many large city theaters
were air conditioned, as well as some multi-story office buildings
and department stores. In the early thirties the Carrier Corporation
developed a compact room air conditioner, but such was the lack
of demand in the depression that it never marketed it. Home air
conditioning came into its own only after World War II. When the
planning committee for JUL Central decided for air conditioning
in 1939, a few buildings in Nashville already had air conditioning,
including one state office building, one bank, and the Davidson
County Court House. The Cain-Sloan department store installed air
conditioning at the same time as JUL, and perhaps alone in Nashville
offered as many engineering challenges as JUL.
Compressor, rear view.
Leopold was hired before building construction began. Thus, he was
able to integrate his heating and cooling system into the specifications
provided the main contractor. Most of these involved the basement,
but also the allocation of needed space for all the duct work. JUL
Central had a huge basement, of two levels. The upper basement,
in the central tower, included stack floor one, which is approximately
eight feet high. The southwest stairwell, and the public elevator,
offered the only non-stack access to this basement area. The stacks
in this lowest level do not extend to the outer walls on either
the east or west of the building, leaving an eight feet wide tunnel
for the ducts that connect the two wings. The basement areas in
the two wings are twice as deep as stack floor one, or around 17
feet high, with the north basement extending for the whole 144 feet,
the south one only about half of this distance. As planned from
the beginning, the north basement would house the main electrical,
heating, and cooling equipment. A new tunnel from Garland Hall extended
the Vanderbilt steam plant's pipes to the northwest basement (JUL
would have to pay Vanderbilt for its heat). An outside stairwell
leading down to twin doors at the north end of the library provided
access to this deepest basement and to all the utilities.
Leopold completed his specifications for the air conditioning, he
was able to open bids for all the duct work and all circulating
fans and to specify the cooling capacity of the completed system,
but at first offered alternative possibilities for the compressor
or compressors. I am sure he was in constant contact with the Carrier
Corporation, and aware of a rapidly evolving technology. For a few
months, he held out the option of two compressors, and stopped the
construction of faculty studies in both the north towers, in case
both were needed for cooling towers. But by 1940 he had accepted
a Carrier bid for one large, centrifugal compressor. This freed
up the two faculty studies in the northwest tower.
library contained 1,350,000 cubic feet of space. Based on local
climate data, Leopold believed it would take 194 tons of refrigeration
to cool the building when the combined heat and humidity reached
record levels. A ton as a measure of cooling derived from an earlier
era, for it reflects the amount of cooling produced when a ton of
ice melts over a twenty-four hour period. Thus, Leopold required
Carrier to furnish a 200 ton compressor. It had to be capable of
cooling 965 pounds of fresh air per minute (this entered through
screened louvers at the northeast corner of the north basement)
at a temperature of 95° F and a dew point of 80°, plus 3000
pounds of circulating air (back from the library above) at 78°
and 65° dew point. Its target temperature was 76° with a
relative humidity of 50 percent. The variance allowed was slight,
or only one degree of temperature above or below this target, and
one or two percentage points in the humidity. The installed system
would meet these targets, at least in the early years. Note that
the maximum conditions were not likely to be exceeded. Obviously,
Nashville temperatures often soar above 95°, but when temperatures
are this high the dew point is never close to 80°, and when,
during rainy weather, the dew point may rarely exceed 80°, the
temperature will never be close to 95°.
The author alongside the compressor.
200-ton Carrier compressor was an impressive machine. It still is
in its presently unused but basically unchanged condition. It worked
for over forty years and, if needed, I am
sure it would still chill water for cooling. But it was at the small
limits of centrifugal compressors. Most in Leopold's earlier installations
were three times as large. The one for JUL had only one set of impellers
and not the two or three on large machines. It had two thermostatically
controlled vanes to control the flow of Freon, and thus also the
variable energy demands on the motor. The circular chamber for the
impellers was fully five feet high. The motor and compressor were
very heavy. The motor, with a speed of 3540 RPM, even if perfectly
balanced, was sure to produce both a loud noise and some vibration.
Thus, Leopold required the general contractor to dig a pit down
to bed rock and pour a concrete platform on top of this for the
compressor, all before pouring the concrete floor of the basement,
and to place a separator between the platform and floor. Thus, the
compressor would not shake the whole building.
compressor forced the circulating Freon into the coiled tubes of
the condenser, which was mounted above the compressor. Here under
pressure the gas condensed into a fluid, with the condensation heating
the Freon. One way of stating the task of an air conditioner is
to get heat out of a building. The compressor used inertial energy
to condense and heat the refrigerant (the present Vanderbilt chiller
uses direct heat and not compression). The problem was how to cool
the condenser coils and transfer the heat to outside the building.
In home or automobile air conditioners, a flow of air does the cooling.
This is not the most efficient way to do it, and thus is rarely
used in large units. A flow of cold water works best. One way to
get this is to pump cool water from a well through the condenser,
and then allow this heated water to flow to an outside sink or back
into the well. Such a well can support the most efficient system
possible. Vanderbilt had no such well, and could not afford to buy
enough city water to provide a steady flow. Thus, as in most large
systems, it opted for a cooling tower, one that used evaporation
to cool the condenser water. Most cooling towers (like the present
unused and ugly tower on top of the graduate wing of the library)
are constructed on the outside of buildings. JUL Central may have
been unique. Leopold, in order to save money, and to hide what is
usually a loud and ugly tower, decided to convert the northeast
tower of the library into an internal cooling tower.
is how Leopold did it. He used a pump to push the heated water out
of the condenser and up to near the top of the northeast tower.
He placed, on the roof of the tower, a twenty-five hp exhaust fan,
which pulled outside air in at the bottom of the tower, through
louvered openings that, from the outside, appeared to be windows.
He covered the walls of the tower with cooper sheathing, and created
an even thicker copper pan covering the floor. In the old Carrier
tradition, he used brass nozzles on the walls of the tower to release
water in a fine mist, which drifted down through the upsurging air.
Redwood boards, which stretched across the tower, creating additional
surfaces for the falling water. This all maximized the rate of evaporation
in the water, and thus the degree of cooling. The water flowed back,
by gravity, to the condenser, at a temperature of 80° or less, or
a drop of 15° from its entering temperature.
cooled by water, the refrigerant was ready to do its work in the
evaporator. It moved from the condenser through a thermostatically
controlled pressure valve into the evaporator, another large unit
above the compressor. Here the Freon, in coiled tubes, expanded
and evaporated, cooling to a controlled temperature (determined
by the level of pressure created by the compressor). These coils
cooled the bath of water surrounding them, creating the chilled
water that air conditioned the library. The evaporator had an output
of up to 690 grams of water per minute at a temperature as low as
45°. What happened next, for the cooling and not the heating, was
quite different than in systems today. Normally, such chilled water
circulates to pipes or coils within the main plenum and there cools
the air. The condensation that forms on the coils, and is drained
to the outside, lowers the humidity.
Carrier's Control Panel.
still used the old Carrier dew point system. He had the contractor
construct what he called a dehumidifier. It was a large box, a miniature
version of the cooling tower. All the
air that was to circulate in the building flowed through this box.
Surrounding the inside of the box were 240 small brass spray nozzles,
which created the fog-like surfaces for both cooling and dehumidifying.
The thermostatically controlled temperature of the chilled water
determined the humidity and temperature produced in the circulating
air. The extracted humidity simply added to the volume of chilled
water. Except for a small amount of chilled water used to cool the
compressor motor, it was all pumped through the dehumidifier. This
system offered more cooling surfaces than coils in a plenum, and
in this sense was more efficient. It also allowed an exact control
of the humidity, but the heat caused by the internal condensation
slightly lowered the cooling capacity of the unit, particularly
in very humid weather.
before it entered the dehumidifier, the air had passed through an
electrostatic filter. This involved a circulating curtain, which
passed through an oil pan at the bottom of its circuit. This was
supposed to remove the dust and dirt, which sank to the bottom of
the pan as removable sludge. But such was the air in Nashville that
the device was not perfectly self-cleaning. Periodically, the engineer
who supervised the system had to take out the curtain and clean
25 hp fan near the compressor pulled in the fresh and recycled air,
and moved it through the filter and dehumidifier and then through
large ducts to both wings of the library. But it was not powerful
enough, or properly located, to provide a balanced flow of either
heating or cooling through all the complicated rooms and stack floors
of the library. Thus, Leopold added six supplemental circulating
fans (driven in each case by either a five, ten, or fifteen hp motor).
He thus cut the library into six zones, and used the smaller units
for either smaller or lower zones, and the larger units for either
larger or upper zones. Each of the six large circulating units had
sets of disposable filters, or ninety in all. The careful design
of all the ducts, dampers, and grills (by 1941 this was a science
in itself) completed the strategies Leopold used to bring clean,
properly heated or cooled, correctly humidified air to every corner
of the library, down to closets and carrels.
goal of the system was not only perfect control over temperature
and humidity, but to achieve this at the smallest possible cost.
The system was first tested in May, 1942. It seemed to work perfectly.
It was a complex system. A full-time engineer presided over its
operation. It had only one or two brief down periods during each
of the first five years, with the various contractors making needed
adjustments. In the summer of 1942, the system was on only from
June until the end of the Peabody summer school (Vanderbilt had
no summer school) in early August. The operating cost for the summer
was only $1250, or $1.66 per hour of operation. Throughout the war,
the system was off when the students were not present on either
campus, meaning long periods when the staff had to open windows
and suffer, while the books did not gain the benefit of controlled
humidity. From 1942 through 1948 the average annual cost was $1283.
After this, the system was in use longer during most summers, and
costs were higher. Almost everyone acclaimed the system and loved
to visit the library in summer. When I came to Vanderbilt as a graduate
student in 1951, this was the first air conditioned building I had
ever experienced. As late as 1951 no other buildings on either of
the three campuses had central air conditioning (Peabody air conditioned
a new Payne Hall in 1952).
original system remained intact until the new addition in 1967,
when a new cooling tower replaced the one in the northeast tower,
and additional compressors supplemented the original Carrier Unit.
Only in the eighties did Vanderbilt University replace all the original
system. Ironically, the present system, with its chilled water supplied
by a central unit on the Peabody campus, has to make use of some
small, supplemental compressors on the roof, and does not provide
as balanced heating and cooling as the old Carrier unit in 1942.
My faculty study, for example, effectively has no central heating
Acknowledgments: Several people
helped me in telling this story. The staff of Special Collections
assembled the boxes of JUL records. Henry Shipman found and displayed
many photographs of the early building. The staff of campus planning
provided access to the early architectural plans. Dewey James introduced
me to the wonders of the basement, including the old Carrier compressor.
Jean Wright, whose experience reaches back to early JUL Central,
helped me immensely in understanding how the system worked at the
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B&W photos courtesy Vanderbilt University Special
Collections and University Archives.
Color photo by Neil Brake.
updated June 6, 2005
comments to Celia Walker