Info

limitations

number possible

or two passes

limitations^

limitations

limitations^

Internal gaskets eliminated

Yes

Yes

Yes

No

Yes

No

NOTE: Relative costs A and B are not significantly different and interchange for long lengths of tubing. 'Modified from page a-8 of the Patterson-Kelley Co. Manual No. 700A, Heat Exchangers.

fU-tube bundles have been built with tube supports which permit the U-bends to be spread apart and tubes inside of the bundle replaced.

tNormal triangular pitch does not permit mechanical cleaning. With a wide triangular pitch, which is equal to 2 (tube diameter plus cleaning lane)/^3, mechanical cleaning is possible on removable bundles. This wide spacing is infrequently used.

§For odd number of tube side passes, floating head requires packed joint or expansion joint.

FIG. 11-35 TEMA-type designations for shell-and-tube heat exchangers. (Standards of Tubular Exchanger Manufacturers Association, 6th ed., 1978.)

function (chiller, condenser, cooler, etc.). Almost any type of unit can be used to perform any or all of the listed functions. Many of these terms have been defined by Donahue [Pet. Process., 103 (March 1956)].

Equipment

Function

Chiller

Condenser Partial condenser

Final condenser

Cooler Exchanger

Heater Reboiler

Thermosiphon reboiler

Forced-circulation reboiler Steam generator

Superheater Vaporizer Waste-heat boiler

Cools a fluid to a temperature below that obtainable if water only were used as a coolant. It uses a refrigerant such as ammonia or Freon.

Condenses a vapor or mixture of vapors, either alone or in the presence of a noncondensable gas.

Condenses vapors at a point high enough to provide a temperature difference sufficient to preheat a cold stream of process fluid. This saves heat and eliminates the need for providing a separate preheater (using flame or steam).

Condenses the vapors to a final storage temperature of approximately 37.8° C (100° F). It uses water cooling, which means that the transferred heat is lost to the process.

Cools liquids or gases by means of water.

Performs a double function: (1) heats a cold fluid by (2) using a hot fluid which it cools. None of the transferred heat is lost.

Imparts sensible heat to a liquid or a gas by means of condensing steam or Dowtherm.

Connected to the bottom of a fractionating tower, it provides the reboil heat necessary for distillation. The heating medium may be either steam or a hot-process fluid.

Natural circulation of the boiling medium is obtained by maintaining sufficient liquid head to provide for circulation.

A pump is used to force liquid through the reboiler.

Generates steam for use elsewhere in the plant by using the available high-level heat in tar or a heavy oil.

Heats a vapor above the saturation temperature.

A heater which vaporizes part of the liquid.

Produces steam; similar to steam generator, except that the heating medium is a hot gas or liquid produced in a chemical reaction.

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