The TEMA heat exchanger refers to a shell and tube heat exchanger built according to the standards established by the Tubular Exchanger Manufacturers Association (TEMA). These standards define the construction and manufacturing requirements for shell and tube heat exchangers, ensuring quality and interchangeability across different manufacturers. TEMA standards are widely used in industries like oil and gas, chemical processing, and power pants. 

TEMA heat exchanger includes heaters, condensers, reboilers, and other type shell and tube heat exchangers. There are three major TEMA classifications: TEMA Class C (General commercial applications), TEMA Class B (Chemical applications), TEMA Class R (Refinery applications).