HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New Millenniumthe air. Air conditioning technology began to progress much furtherwhen in the 1840s, several systems evolved for both cooling and humidifyingrooms.The first units were developed by textile manufacturers to reducestatic electricity in the air. Later, adaptations were made by other industries.Although developments in air conditioning technology increasedrapidly in the first part of the 20th century, the widespread use of airconditioning in buildings did not take place until the post-World War IIperiod.Unlike the early forms of air conditioning which were designed tocool the air and add moisture to it, modern air conditioning systems cancontrol temperature, air moisture content, air cleanliness, and air movement.The modern systems truly condition the air, rather than simplycool it.Heating SystemsMany different methods have been devised for heating buildings.Each has its own characteristics and most of them have at least oneundesirable characteristic such as the cost of fuel, expensive to install orinefficient heating. Most of these heating methods can be classified accordingto one of the following four criteria:• heat conveying medium,• fuel used,• nature of the heat, and• efficiency of the method.The heat conveying medium is the substance or combination ofsubstances that carries the heat from its point of origin to the area beingheated. The four basic mediums for conveying heat are air, water, steamand electricity.Throughout history different types of wood, coal, oil, and gasproducts have been used as fuels for producing heat. Electricity can beconsidered both as a fuel and a heat conveying medium. Each type ofheating fuel has its characteristics and the advantages of one over anotherdepends on variables such as availability, efficiency and cost.©2001 by The Fairmont Press, Inc. All rights reserved.