Heating | Research & Encyclopedia Articles

Heating

Heating has had a major impact on human development by allowing people to reside and function far from the temperate areas of the earth. Heat warms human beings in one of three ways--conduction, convection, or radiation.

Conducted heat passes directly from a heated object into the body, as with the heated bricks and warming pans which chased the chill from beds in Colonial times, or modern-day electric blankets and battery-operated socks. Convection, the main principle in forced-air furnaces, heats the air around the body. The third type, radiation, resembles the warmth of the sun in that heat moves outward in waves and maintains an even temperature. Radiation heat is commonly found in electric coil bathroom wall heaters and quartz space heaters for porches and patios.

The most primitive heating systems were cave fireplaces, which early people improved upon by cutting draft holes to allow smoke to escape. Native Americans utilized this principle in the design of tepees, which were erected around fires and channeled smoke through the opening in the top. Eventually, more sophisticated residents built chimneys to direct smoke and soot away from living spaces. However, these open fires required constant tending, removal of ash and creosote, and a screen to protect against falling logs and exploding live coals. Tile, brick, and iron stoves replaced fireplaces but dried out the air and posed a hazard to anyone who brushed against them. In China, families found greater comfort in sleeping on heated slabs, which they built over hearths. Around 350 B.C., a similar system in Ephesus, Greece, warmed the Great Temple through heated channels in the floor. The first centralized system of heating originated around 100 B.C. with the Roman underground hypocaust, which directed heated vapors through hollow terra cotta tubes in walls and floors of homes and public steambaths.

Until the re-emergence of central heating after the Dark Ages wiped out Roman innovations, most homes and buildings were drafty and uncomfortable because they were heated with fireplaces and stoves, which proved inefficient in that warmth stayed near the source, overheating some areas and failing to affect the temperature farther away. Benjamin Franklin invented an upgraded version of the stove in 1744 by regulating the draft and making the temperature easier to control. The Franklin stove remained a staple in most homes until furnaces came into common use.

An improvement on the stove was the creation of the room radiator, which was linked by ducts or pipes to a furnace. In 1777, Bonnemain, a Parisian innovator, devised a system of circulating or pumping hot water heated from coal or gas furnaces to radiators, a method which evened out temperatures in his castle by spreading heat over a wide surface. When the water cooled, it flowed back to the furnace for reheating. Bonnemain controlled this system with a crude thermostat--a lead rod in the boiler which expanded and contracted with changes in the water's temperature, thereby altering the intake of air.

In 1831, Jacob Perkins patented a high-pressure model of the heat circulator. This system, which made its appearance in the United States around 1840, proved clean and dependable. Still, it posed a fire hazard unless the furnace and flue were carefully insulated with fireproof materials and regularly cleaned of ash and soot, which impeded the draw of oxygen to the flame. James Watt devised a steam heating system in 1784 in his factory in Birmingham, England, employing a boiler to heat water, then directing the resulting steam through pipework and into radiators. Baron Mayer Amschel de Rothschild of England was the first to install this expensive system in a home. The system was patented in 1791 and proved clean and efficient, especially in apartment buildings, churches, schools, factories, and assembly halls. However, steam heat lacked the efficiency of later methods, which were more easily adapted to the rise or fall of temperatures. Another fault of steam heat was its inability to heat radiators at the end of the line, and the intermittent clanking in the pipes when pockets of cold air were trapped in the pipes.

But hot-air systems contained a built-in problem: they blew dust, fumes, and dirt along with the warmed air. For this reason, electric heating began edging out forced-air heating at the beginning of the twentieth century. Emanating from ceiling and floor panels or radiators, radiant electric heat offered a clean, efficient, maintenance-free alternative to earlier methods. In 1892 R. E. Bell Crompton and J. H Dowsing's invented of the electric radiator, consisting of a wire protruding from an iron plate and coated with enamel. An American, Albert Marsh, following the lead of Englishman A. H. Barker, invented a nickel-chrome alloy heating coil for electric heaters in 1906; in 1908, Hugh M. Browne a governor to control furnace dampers. Six years later, C. R. Belling devised a fireproof clay which he encircled with a wire made of the same nickel-chrome alloy, the impetus for his standard radiator.

In the 1950s, utilities engineers created the radiant ribbon, a hot water radiant system for baseboard heat. A pipe, shielded by a metal cover, followed the baseboard of a room, directing heat to the floor, which was usually the coldest point in a room. This system suited many homeowners because it heated objects rather than the air around them.

Another innovation, the heat pump, a much neglected design of Lord Kelvin (1824-1907) in 1851, remained untapped until the twentieth century. The heat pump utilizes one cycle for heating, then reverses it for air conditioning. Applying the principle of refrigeration in reverse, the heat pump forces air to an evaporator, then compresses it to a higher temperature and blows it into unheated areas. This method works well in swimming pools and homes, but only where temperatures never reach extremes.

Probably the least utilized of all current heating systems is the solar collector, which absorbs energy from the sun into tiles, rocks, or water and stores it until it can be circulated or blown over cold rooms. However, the cost and bulk of solar panels and storage cells has inhibited their popularity.