Shell and tube heat exchangers7 (4)

The shell and tube heat exchanger, also known as the jacketed heat exchanger, is a type of inter-tube heat exchanger where the walls of the tube bundle enclosed in the shell serve as the heat transfer surface. This type of heat exchanger is characterized by its simple construction, low cost, wide flow cross-section, and ease of scale cleaning; however, it has a low heat transfer coefficient and occupies a large space. It can be made from various materials (primarily metal) and is used under high temperature and pressure conditions, making it the most common type. Tubular heat exchangers include several types: stationary tube bundles of steam-water heat exchangers, tubular steam-water heat exchangers with compensators, floating-head steam-water heat exchangers, U-shaped tube bundles of steam-water heat exchangers, tubular steam-water heat exchangers with corrugated sections, sectional water-water heat exchangers, and others. The main control parameters of tubular heat exchangers are heating area, hot water flow rate, heat transfer, heat carrier parameters, and others. The shell-and-tube heat exchanger consists of a shell, a bundle of heat exchange tubes, a tube sheet, baffles, and a tube box. The shell is usually cylindrical, with a bundle of tubes installed inside, whose ends are fixed on the tube sheet. The two heat exchange flows, the cold and the hot, move in opposite directions: one inside the tubes, called the tube side flow, and the other outside the tubes, called the shell side flow. To increase the heat transfer coefficient of the shell side flow, several baffles are typically installed in the shell. The baffles increase the velocity of the shell side flow, causing it to repeatedly cross the bundle of tubes along a specific trajectory, enhancing the flow turbulence. The heat exchange tubes on the tube sheet can be arranged in an equilateral triangle or square pattern. The equilateral triangle arrangement provides a more compact layout, higher turbulence in the shell side flow, and a greater heat transfer coefficient; the square arrangement is convenient for cleaning the shell side space and is suitable for flows prone to fouling. The main control parameters of the shell-and-tube heat exchanger are heating area, hot water flow rate, heat transfer, and heat carrier parameters. Each passage of fluid through the tube space is called a tube pass; each passage through the shell is called a shell pass. The figure shows the simplest heat exchanger with one shell pass and one tube pass, which is briefly referred to as a 1-37 heat exchanger. To increase the fluid velocity in the tubes, baffles can be installed in the tube boxes at both ends, dividing all tubes into several groups. Thus, the fluid passes through only part of the tubes during each pass, making multiple passes through the tube space, which is called multiple tube passes. Similarly, to increase the fluid velocity in the shell space, longitudinal baffles can be installed in the shell, forcing the fluid to pass through the shell space multiple times, which is called multiple shell passes. Multiple tube and shell passes can be used together.