Plate-type exchangers

Because of the shape of the plates, the developed area of surface is appreciably greater than the projected area. This is shown in Table 9.22 for the four common sizes of plate. 

Plate type Projected area Developed area 

A high degree of turbulence is obtained even at low flowrates and the high heat transfer coefricients obtained are illustrated by the data in Table 9.23. These refer to the heating of cold water by the equal flow of hot water in an HE type exchanger (aluminium or copper), at an average temperature of 310 K. 

Using a stainless steel plate with a flow of 0.00114 m /s, the heat transferred is 1760 W/K for each plate. 

A further desipE of spir heatexchmiger, descrit d by is essentially a single 

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Bypassing in a plate-type exchanger is less of a problem and more use is made of the flow separation which occurs over the plate troughs since the reattachment point on the plate gives rise to an area of very high heat transfer. 

It generally is considered that resistance due to fouling is lower with plate heat exchangers than with tubular units. This is the result of four advantages of plate-type exchangers ... 

Table 9.23. Performance of plate-type exchanger type HF ...

Mercury-cell caustic filters operate at higher temperatures than do other product filters. Some plants operate above 100°C. The solution, pumped under flow control or feed tank level control, leaves the filter with less than 0.5 ppm Hg, usually about 0.1. It then can be cooled before storage, usually to 40-50°C, in a plate-type exchanger. 

The hot glycol from the reboiler is cooled by heat exchange with the wet glycol from the contactor. This heat transfer typically takes place in a double-pipe or plate-type exchanger. On one of the double-pipe heat exchangers, I noticed that the reboiled glycol was being cooled to a rather... 

There are two major types gasketed and welded-plate heat exchangers. Each shall be discussed individually. 

When the solute has a large heat of solution or when the feed gas contains high percentages of the solute, one should consider the use of internal coohng coils or intermediate external heat exchangers in a plate-type tower to remove the heat of absorption. In a packed tower, one could consider the use of multiple packed sections with intermediate hquid-withdrawal points so that me hquid coiild be cooled by external heat exchange. 

Plate-type design (space heaters) Type of heat exchanger characterized by a substantial proportion of its heat output being by way of radiant energy. 

Various designs of liquid/liquid heat exchanger are widely used. Choice is partly influenced by the cleanliness of the liquids and the need for regular cleaning. A compact and commonly used type is the plate heat exchanger. 

Plates are available with effective heat transfer area from 0.03 to 3.5 m and up to 700 can be contained within the frame of the largest plate-type heat exchanger, providing over 2400 m of surface area. Flow ports and associated pipework are sized in proportion to the plate area and control the maximum liquid throughput. 

One particularly important feature of the plate heat exchanger is that the turbulence induced by the troughs reduces the Reynolds number at which the flow becomes laminar. If the characteristic length dimension in the Reynolds number is taken as twice the average gap between plates, the Re number at which the flow becomes laminar varies from about 100 to 400, according to the type of plate. 

Most plate heat exchanger designs fall into the viscous flow range. Considering only Newtonian fluids since most chemical duties fall into this category, in laminar ducted flow the flow can be said to be one of three types ... 

The first type is of interest only when considering fluids of low Prandtl number, and this does not usually exist with normal plate heat exchanger applications. The third is relevant only for fluids such as gases which have a Prandtl number of about one. Therefore, let us consider type two. 

The authors provide selection criteria, by which the suitability of a process for a distributed production can be assessed [139]. These are explicitly given for the categories of feedstock, processes, customer products, and waste products. This is completed by a list of suitable device types for distributed production such as plate heat exchangers, pressure and temperature swing units, electrostatic dispersers, and membrane units. The various operations often rely on the use of electricity and therefore are said to be particularly suited for operation at the mini scale. 

Different from sole combinations of micro devices, this refers to a total system with many functional elements and flow-distribution and, recollecting zones, typically composed of 2-D plate-type architecture. Each of these plates usually has a separate fimction, comprising imit operations and reaction. Frequently, micro mixing and micro heat exchange fimctions and corresponding elements are employed. Often, the system can be composed of different elements resulting in different process flow combinations. Such an approach may be termed a construction kit. 

Plate-fin heat exchangers. Another type of plate heat exchanger is the plate-fin heat exchanger. This is illustrated in Figure 15.17. The plate-fin heat exchanger consists of a series of flat plates, between which is a matrix formed... 

For certain applications multi-pass arrangements are used. When a plate heat exchanger is used instead of the tubular unit, boiling on the heating surfaces is avoided by increasing the static head using a line restriction between the plate pack and the separator. Compared with tubular units, lower circulation rates and reduced liquid retention times are important advantages. Plate-type units are discussed further in Section 14.7.7. 

It may be noted that the gasket is a key component in plate heat exchangers, and this may limit the maximum temperature which can be used and may indeed prevent the use of this type of equipment with some corrosive fluids. 

Figure 5.1 Few common types of heat exchangers, (a) Double-tube type (b) shell-and-tube type (c) coil-type and (d) plate-type.

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