heating water

were available long before electrically powered circulators.
Flow between the “water jacket” of the stove and the
“range boiler” tank was created by thermosiphoning due
to the differences in density between hot and cold water.
The evolution of heat exchangers was also critical to
development of internal combustion engines. Some of
the earliest engines were cooled solely by surrounding air.
As engine design improved and horsepower increased,
it became impractical to rely solely on surrounding air to
keep the engine temperature under control. Engineers of
that era turned to the superior thermal properties of water
as a means of conveying heat from inside engine blocks to
a location where it could be dissipated to surrounding air.
Figure 1-4 shows an example of a Ford Model T radiator.
radiators, this radiator was not pressurized. Model T
drivers learned to carry extra water with them to replace
the water lost through evaporation, and in some cases,
boiling inside the radiator.
All fuel-burning boilers used for heating buildings have a
combustion chamber combined with a heat exchanger.
Figure 1-5a shows an example of a cast iron section that
is used to build the heat exchanger of a cast iron boiler.
Figure 1-5b shows how this heat exchanger, which is also
called a boiler “block,” is made by joining several cast iron
sections together.
Figure 1-5
Figure 1-4
Courtesy of motormission.com
This radiator could be fundamentally described as a waterto-air
heat exchanger. For its time — the early 1900s —
it represented state-of-the-art-technology. Water from
the upper portion of the engine block flowed into the
upper portion of the radiator and divided up into multiple
closed channels made of copper or brass. Air passed
between these channels as a result of the car moving,
as well as flow created by a simple fan connected to the
engine’s crankshaft by a leather belt. The higher thermal
conductivity of the copper and brass channels provided
minimal thermal resistance between water and the outer
surfaces of the radiator. After giving up heat, the coolest
water settled into a reservoir at the base of the radiator
and flowed back to the lower portion of the engine. No
water pump was used. All flow was driven by the changes
in buoyancy of the water between the top of the engine
and lower portion of the radiator. Unlike modern vehicle
Hot gases pass upward from the combustion chamber
and across the “pins” on the cast iron sections. The pins
increase the heat transfer surface area of the section. Heat
from the hot gases passes through the cast iron walls of
each section and is absorbed by the water inside.
Heat exchanger technology continued to progress
through the 20th century. Hundreds of heat exchanger
designs were developed for use in boilers, radiators,
chillers, fan-coils and convectors. Wrought iron pipe and
copper tubing were embedded into concrete slabs to
create “radiant panel heat exchangers,” as seen in Figure
1-7. These panels transfer heat from heated water into
occupied spaces using thermal radiation and convection.
Today, heat exchangers are precisely engineered for use
in all types of stationary energy-processing equipment, as
well as virtually all land-based vehicles, marine vessels,
aircraft and spacecraft. These devices range from huge,
multi-ton cooling towers used to dissipate heat from highrise
buildings (Figure 1-8), to tiny liquid cooling systems for
microprocessors (Figure 1-9).
Courtesy of Weil McLain
6