The temperature of the fluid in the tubes increases continuously as the fluid flows through the tubes.
Temperature ºC
The temperatures of the condensing vapor and of the liquid are plotted against the tube length. The horizontal line represents the temperature of the condensing vapor, and the curved line below it represents the rising temperature of the tube-side fluid.
流体力学与传热课件Principles of Heat Flow in Fluids
• Heat transfer from a warmer fluid to a cooler fluid, usually through a solid wall separating the two fluids, is common in chemical engineering practice.
Heat is transferred between warm and cool fluids by conduction and convection.
4.3.1 Typical Heat-Exchange Equipment
Typical heat-exchange equipment Single-pass shell-and-tube condenser
The two fluids enter at different ends of the exchanger and pass in opposite directions through the unit.
It is called counterflow or countercurrent flow. The temperature-length curves for this case shown in figure.
Single-pass shell-and-tube condenser
If the vapor entering the condenser is not superheated and the condensate is not subcooled, the temperature throughout the shell-side of the condenser is constant.
connection G leads to a trap, which is a device that allows flow of liquid but holds back vapor.
The fluid to be heated is pumped through connection H into channel D2.
One fluid flows through the inside pipe and second fluid through the annular space between the outside and inside pipes.
Double-pipe eFra bibliotekchanger are useful when not more than 9 to 14 m2 of surface is required.
It consists essentially of a bundle of parallel tubes A, the ends of which are expanded into tube sheets B1 and B2.
The tube is inside a cylindrical shell C and is
Temp of condensing vapor T
Δt2 Δt Δt1
Length of tube L
Double-tube heat exchanger
It is assembled of standard metal pipe and standarized return bends and return heads. shown in figure.
• The heat transferred may be latent heat accompanying a phase change such as condensation or vaporization, or
it may be sensible heat from the rise or fall in the temperature of a fluid without any phase change.
For larger capacities , more elaborate shelland-tube exchangers, containing up to thousand of square meter of area, are used.
Countercurrent and parallel-current flows
provided with two channels D1 and D2, one at each end, and two channel covers E1 and E2.
Steam and other vapor is introduced through nozzle F into the shell-side space surrounding the tubes, condensate is withdrawn through connection G, and any noncondensable gas that might be enter with the inlet vapor is removed through vent K.