Tube-in-tube condenser
Tube-in-tube condenser structure
The tube-type condenser is primarily composed of the shell, tube plate (also known as the header), tube bundle, and top cover (also referred to as the head). Parallel tube bundles are installed inside the circular shell, with the ends of the tubes fixed on the tube plate. The tubes are generally secured to the tube plate using welding or expansion methods. The top cover, equipped with import or export tubes, is connected to the shell ends' flanges with screws, forming a fluid distribution chamber between the top cover and the tube plate. It is widely used due to its simple and sturdy structure, ease of manufacturing, broad material range, high processing capacity, and strong adaptability.
During heat exchange, cooling water enters through the connection pipes at the top cover, flows within the pipes, and this path is known as the tube side; harmful vapors flow in the space between the tube bundle and the shell, and this path is called the shell side; the surface area of the tube bundle is the heat transfer area. In the condensation recovery process, whether it is the condensation of saturated vapor or the condensation containing non-condensable gases, in general, condensation occurs in the shell side of the horizontal condenser because it is more reasonable in terms of heat transfer, pressure drop, and cleaning.
Tubular Condenser Types
(1) Fixed tube sheet heat exchangers: Simple and compact structure, capable of withstanding high pressure, low cost, easy to clean the tube side, and easy to block or replace tubes when damaged.
(2) Floating Head Heat Exchanger: Easy to clean inside the tubes and between them, without generating thermal stress.
(3) U-tube Heat Exchanger: Consists of a single tube sheet with a bundle made up of multiple U-shaped tubes. Both ends of the tubes are fixed on the same tube sheet, allowing for free expansion and contraction. No thermal stress is generated when there is a temperature difference between the shell and the U-tube heat exchanger.
(4) Sliding header heat exchanger: Simple structure, low cost, with the option to add baffles in the header as needed to enhance heat transfer.
Features of Tube-in-Tube Condensers
(1) Horizontal shell-side film heat transfer coefficient is several times higher than that of vertical tube-side or tube-outside film heat transfer coefficient, and non-condensibles are less likely to accumulate in dead corners and are easier to discharge.
(2) The cooling water flows through the pipes, making it easier to clean scale. Water flow within the pipes ensures a higher velocity, which is beneficial for reducing scale formation and improving the heat transfer coefficient of the water film.
(3) Tube-in-tube condensers are used to position the lower tubes at the cooling water inlet, allowing condensate to accumulate at the bottom, thereby reducing the condensate temperature. In surface condensing systems, it is crucial to further cool the condensate. If the condensing system temperature is too high, upon contact with air, organic gases will volatilize extensively. Typically, the outlet temperature of the condensate is required to be 60℃ or lower. Of course, an additional cooler can be added, but this will increase costs.
