EXH700 plate and frame exchangers

This section briefly describes the advantages and disadvantages of plate and frame exchangers. General Information Plate and frame exchangers consist of thinrippled alloy plates spaced about 14 inch apart. Gasketing (usually rubber) seals the edges of the plates and directs the flow into and out of appropriate headers. The streams exchanging heat usually flow in every other channel in pure countercurrent flow. The general arrangement is illustrated

Chevron Corporation 700-1 December 1989

700 Plate and Frame Exchangers

Abstract

This section briefly describes the advantages and disadvantages of plate and frame exchangers

700 Plate and Frame Exchangers Heat Exchanger and Cooling Tower Manual

710 General Information

Plate and frame exchangers consist of thin-rippled alloy plates spaced about 1/4 inch apart Gasketing (usually rubber) seals the edges of the plates and directs the flow into and out of appropriate headers The streams exchanging heat usually flow

in every other channel in pure counter-current flow The general arrangement is illustrated in Figure 700-1

The advantages of plate and frame exchangers are:

1 Pure counter-current flow

2 Compact

3 Light weight

4 Easily expandable (assuming excess pumping capacity)

The disadvantages of plate and frame exchangers are:

1 Less efficient than in-tube turbulent flow

2 Less efficient than in-shell viscous flow over a staggered tube layout

3 Limited to moderate temperatures (<250°F) and pressures (<200 psig)

4 Superior metallurgy (noncorroding) required

Fig 700-1 Plate and Frame Exchanger

Heat Exchanger and Cooling Tower Manual 700 Plate and Frame Exchangers

5 Gasket deterioration is a problem with hydrocarbon mixtures

6 Poor fire resistance because of large exposed bolts and normal gasket material (usually rubber)

For turbulent flow, the best conversion of pressure drop to heat transfer is in a straight tube where all friction pressure drop thins the laminar sublayer near the heat transfer surface Plates are less efficient as a portion of the pressure drop is expended changing fluid direction around the plate ripples Turbulent-flow heat transfer in plates and in shells is equally efficient

In viscous flow, thermal boundary layers limit heat transfer Flow across a stag-gered-tube layout is best with viscous flow because thermal boundary layers are discontinuous from row to row Viscous flow in plates exhibits the same rapid decrease in heat transfer with increasing viscosity as in-tube flow (see Figure 200-4

in Section 213)

HTRI tests have shown that fouling in plates, in tubes, and in shells is about the same for the same expenditure of pumping power (pressure drop) per unit of heat transfer surface

Plate and frame exchangers may not be cost-competitive when compared to a well-designed shell and tube exchanger unless the following applies: weight, space, and/or expandability are highly valued; the same alloy is required for both types of exchangers; pressures and temperatures are moderate; fire hazard is nonexistent or minimal; and fluids are compatible with rubber gaskets At the same time, some upstream experience suggests that plate and frame exchangers are cost competitive, and they are worth investigating in most cases

The use of titanium plate and frame exchangers on offshore platforms in sea water/fresh water service is an appropriate application