1. A Brief History
Most animals come into this world with built-in insulation, but human beings come with a delicate skin.
Unlike animals such as a fox or a bear that are born with built-in furs, human beings come into this world with little protection against the harsh environmental conditions (Fig. 1). Therefore, we can claim that the search for thermal comfort dates back to the beginning of human history. It is believed that early human beings lived in caves that provided shelter as well as protection from extreme thermal conditions. Probably the first form of heating system used was open fire, followed by fire in dwellings through the use of a chimney to vent out the combustion gases. The concept of central heating dates back to the times of the Romans, who heated homes by utilizing double-floor construction techniques and passing the fire’s fumes through the opening between the two floor layers. The Romans were also the first to use transparent windows made of mica or glass to keep the wind and rain out while letting the light in. Wood and coal were the primary energy sources for heating, and oil and candles were used for lighting. The ruins of south-facing houses indicate that the value of solar heating was recognized early in the history.
The development of the first steam heating system by James Watt dates back to 1770. When the American Society of Heating and Ventilating Engineers was established in NewYork in 1894, central heating systems using cast iron warm air furnaces and boilers were in common use. Fans were added in 1899 to move the air mechanically, and later automatic firing replaced the manual firing. The steam heating systems gained widespread acceptance in the early 1900s by the introduction of fluid-operated thermostatic traps to improve the fluid circulation. Gravity-driven hot water heating systems were developed in parallel with steam systems. suspended and floor-type unit heaters, unit ventilators, and panel heaters were developed in the 1920s. Unit heaters and panel heaters usually used steam, hot water, or electricity as the heat source. It became common practice to conceal the radiators in the 1930s, and the baseboard radiator was developed in 1944. Today, air heating systems with a duct distribution network dominate the residential and commercial buildings.
The development of cooling systems took the back seat in the history of thermal comfort since there was no quick way of creating “coolness.” Therefore, early attempts at cooling were passive measures such as blocking off direct sunlight and using thick stone walls to store coolness at night. A more sophisticated approach was to take advantage of evaporative cooling by running water through the structure, as done in the Alhambra castle. Of course, natural ice and snow served as “cold storage” mediums and provided some cooling.
In 1775, ice was made by evacuating the air in a water tank.
In 1775, Dr. William Cullen made ice in Scotland by evacuating the air in a water tank (Fig. 2). It was also known at those times that some chemicals lowered temperatures. For example, the temperature of snow can be dropped to -33ºC (-27ºF) by mixing it with calcium chloride. This process was commonly used to make ice cream. In 1851, Ferdinand Carre designed the first ammonia absorption refrigeration system, while Dr. John Gorrie received a patent for an open air refrigeration cycle to produce ice and refrigerated air. In 1853, Alexander Twining of Connecticut produced 1600 pounds (726 kg) of ice a day using sulfuric ether as the refrigerant. In 1872, David Boyle developed an ammonia compression machine that produced ice. Mechanical refrigeration at those times was used primarily to make ice and preserve perishable commodities such as meat and fish (Sauer and Howell, 1994).
Comfort cooling was obtained by ice or by chillers that used ice. Air cooling systems for thermal comfort were built in the 1890s, but they did not find widespread use until the development of mechanical refrigeration in the early 1900s. In 1905, 200 Btu/min (or 12,000 Btu/h) was established as 1 ton of refrigeration, and in 1902 a 400-ton air-conditioning system was installed in the NewYork Stock Exchange. The system operated reliably for 20 years. A modern air-conditioning system was installed in the Boston Floating Hospital in 1908, which was a first for a hospital. In a monumental paper presented in 1911, Willis Carrier (1876–1950), known as the “Father of Air Conditioning,” laid out the formulas related to the dry-bulb, wet-bulb, and dew-point temperatures of air and the sensible, latent, and total heat loads. By 1922, the centrifugal refrigeration machine developed by Carrier made water chilling for medium and large commercial and industrial facilities practical and economical. In 1928 the Milan Building in San Antonio, Texas, was the first commercial building designed with and built for comfort air-conditioning specifications (Sauer and Howell, 1994).
The first room air conditioner was introduced by Frigidaire in the late 1920s.
Frigidaire introduced the first room air conditioner in the late 1920s (Fig. 3). The halocarbon refrigerants such as Freon-12 were developed in 1930. The concept of a heat pump was described by Sadi Carnot in 1824, and the operation of such a device called the “heat multiplier” was first described by William Thomson (Lord Kelvin) in 1852. T. G. N. Haldane built an experimental heat pump in 1930, and a heat pump was marketed by De La Vargne in 1933. General Electric introduced the heat pump in the mid 1930s, and heat pumps were being mass produced in 1952. Central air conditioning systems were being installed routinely in the 1960s. The oil crises of the 1970s sent shock waves among the consumers and the producers of energy-consuming equipment, which had taken energy for granted, and brought about a renewed interest in the development of energy-efficient systems and more effective insulation materials. Today most residential and commercial buildings are equipped with modern air-conditioning systems that can heat, cool, humidify, dehumidify, clean, and even deodorize the air—in other words, condition the air to people’s desires.