heatexchanging

Heat exchanging, or heat exchange, refers to the transfer of thermal energy between two or more fluids at different temperatures through a solid barrier that prevents mixing. The driving force is the temperature difference, and heat flows from the hotter to the cooler fluid. The basic components include a heat transfer wall or barrier and flow passages that enable convection on both sides and conduction through the wall.

Industrial heat exchangers come in several configurations, with shell-and-tube and plate heat exchangers the most common. Shell-and-tube designs consist of a bundle of tubes inside a shell; one fluid flows through the tubes while the other passes through the shell, and the arrangement can be countercurrent or co-current. Plate heat exchangers use corrugated plates that form a series of thin, narrow channels to maximize surface area. Other variants include finned-tube, air-cooled, spiral, and regenerative exchangers, each chosen for pressure drop, fouling tendency, heat transfer area, and space constraints.

Performance is described by the heat transfer rate Q. In many designs Q = U A ΔT_lm, where U is the overall heat transfer coefficient, A is the heat transfer area, and ΔT_lm is the log-mean temperature difference between streams. For a given stream, Q also equals m dot cp ΔT. The effectiveness NTU method is used to analyze exchangers with fixed inlet temperatures. Fouling and corrosion can reduce U over time, increasing pressure drop and reducing performance.

Design considerations include material compatibility, mechanical strength, corrosion resistance, pressure drop and pumping power, maintenance needs, and leakage prevention. Materials range from stainless steel and copper to aluminum and specialized alloys. Environmental and safety aspects, such as leakage containment and containment of hazardous fluids, are also considered.

Applications span heating and cooling in HVAC, power generation, chemical processing, petrochemicals, refrigeration, and electronics cooling, where efficient transfer of thermal energy between process streams or with ambient environments is required.