Brazed plate heat exchangers, the heat exchange surface of which is formed of packets of parallel corrugated plates, known for a long time. Corrugated surfaces of the plates lead primarily to an increase of the heat transfer surface and also to some heat-transfer enhancement due to changes in the hydrodynamics of streams and destruction of a viscous boundary layer of the coolant. 

The achievement of high values of heat transfer coefficients in these systems (up to 20 kW/m2K) from the point of view of modern ideas of the science of heat transfer is possible. This is determined by the characteristics of their (machines) design, in particular the small size of the channels (a 1.5 – 5.0 mm) and profiling (with shirring), which together determines the high degree of turbulence in the coolant.

Such high values of heat transfer coefficients, of course, predetermine and smaller mass-dimensional characteristics of the plate apparatus. However (!), the authors of all advertising materials for the promotion of the heat exchangers are silent about the values of hydraulic losses in the path of the plate apparatus, which significantly (several times) higher than the equivalent shell and tube units. This is quite natural in narrow channels with artificial roughness with a high degree of turbulence in the coolant. Meanwhile, the increase in the overall hydrodynamic resistance in the circuits PTU, which can occur when replacing a shell-and-tube apparatus on the plate, is inexpedient, since almost all the pumps in the schemes of modern vocational schools are at the limit of their capabilities, and the value of electricity consumption for own needs of thermal power plants in some cases has already reached 6-7 %, which in modern conditions is economically unprofitable.

The reliability of the equipment of vocational schools (TES in General) is currently one of the main requirements when designing (designing) and its operation (including the modernization of equipment). The authors of advertising works on higher reliability of plate apparatus compared to shell-and-tube is based on their higher corrosion resistance (according to the same authors). This is to some extent natural, since the plate units are generally made of corrosion - resistant materials: stainless steel, titanium, Nickel alloys, etc.

No other indicators of reliability of the plate devices, the authors of the above works do not lead. Meanwhile it is known that the modern shell and tube heat exchangers vocational schools, the pipe system which (in some cases, and housing) are made of the same materials (alloys), have reliability considerably exceeding similar indicators previously manufactured vehicles. Comparing the reliability indices of the plate and shell-and-tube apparatus should also be borne in mind that plate heat exchangers are very sensitive to hydro and thermal shock and to mechanical stress from the connecting piping. Shell-and-tube apparatuses of the modern designs of this drawback have not.

The operation and maintenance of heat exchangers vocational school in the conditions of the TPP, as a rule, is reduced to the solution of issues of contamination and cleaning, disassembly and Assembly and repair of the elements of their designs.

The authors of the works promotion plate heat exchangers, mainly summarizing the operating experience of lamellar heat exchangers in the food, pharmaceutical and refrigeration industries, as well as data for individual devices in hot water systems of housing and communal services say that the plate apparatus: - practically not polluted or slightly polluted, chemical composition of water and the velocity of the coolant is not listed; - easy to understand; - quickly cleaned; the cleaning methods are not specified; - you do not have any problems during repair and Assembly.

These data, in our opinion, given only the qualitative characteristics of the operation plate of the apparatus without any indication of specific parameters and modes of their work and comparison with similar data for shell-and-tube apparatuses and, again, are mostly promotional in nature. In most of the above works indicated that the repairs and cleaning of the plate apparatus is preferably carried out by specialized organizations, in fact, the suppliers (manufacturers) of devices.

We believe that this approach is not the most important issues of operation of plate heat exchangers (repair and cleaning) is fundamentally wrong, because it practically excludes prompt repair of devices operating forces (repair) personnel.

It must be borne in mind that the existing TPP of the Russian Federation the system of maintenance of equipment is regulated by a number of normative documents and involves conducting staff work stations for operational monitoring of this equipment and its repair. With regard to heat exchangers, vocational schools, these are periodic inspections of vehicles, comparison of their condition with the normative characteristics, Troubleshooting, cleaning apparatus, and (often) replacement (ogloszenie) tubes.

The claims of manufacturers of plate heat exchangers full service of vehicles, including assessment, resolve minor issues and cleaning makes the station a hostage of the manufacturer of the apparatus, increasing the cost of maintenance of one item of steam turbine plants.

In addition, according to some experts, analyze the whole complex of comparative figures the plate of the apparatus in comparison with shell-and-tube, that under operating conditions the plate devices have shown a number of fundamental factors that negatively characterize them: 

- plate devices operating on the network water (in heating) and the circulating water (there are some cases use them as coolers), dirty much faster than shell-and-tube (at a number of facilities dismantling and cleaning the machines had to make every (!) 12-14 hours); it is emphasized that to clean them significantly more difficult; 

for chemical washing (cleaning) plate vehicles need expensive washing solutions and special (usually corporate) flushing device;

- disassembly, repair and Assembly of the plate apparatus is very time consuming and expensive process and is mainly determined by the need to install new gaskets are very expensive (up to 30% of the cost of the device), have a complex shape and a length ten times greater than shell-and-tube apparatus (in this case the total number of disassembly – Assembly units is limited); also specifies that for the execution of these works requires highly skilled, specially trained personnel; 

- in case of emergency of leakage of a plate apparatus they need to close protective shielding (screens) of special constructions and devices to install special trays, which complicates access devices and their repair; these housings (screens) and trays usually provided by the manufacturers of the apparatus; 

- require large additional space in the shops near the plate of the apparatus for repair, because they need complete disassembly to audit all elements of the structure; in this case the effect is relatively best compact vane machines than a tube-type actually is "in there"; 

- the level of thermal efficiency of plate apparatus does not exceed the corresponding indicators for the modern shell-and-tube apparatuses, and the cost of the plate apparatus above (according to [22], for example, 3 times) than shell-and-tube with the same amount of heat transfer surface (F ? 400 m2); 

- known clearly negative operating experience of about 30 lamellar units (mainly in the various systems of hot water supply in municipal services at least 10 cities and towns of the Russian Federation), when after a short period of use (1-2 years), the machines were dismantled and replaced by shell & tube; there is evidence of a negative experience of application of the plate apparatuses and abroad (England, France, Italy); 

- the overall operational reliability of the plate apparatus are significantly lower than shell-and-tube; for example, in a number of major European cities is not allowed the installation of gasketed plate units (except in special cases) because of their low reliability.

In addition to the above we consider it necessary to formulate a number of own considerations of the authors of this article.

1. No representative data on the results of the comparative balance tests of plate and shell and tube devices of the same surface under operating conditions (interagency). A separate reference to such data give only a qualitative assessment and are openly advertising.

2. There are no regulatory documents (OST, EP, EB, etc.) regulating the methods of calculation and operation of the plate apparatus. In all known materials (publications) developers – suppliers offer machines to handle all the issues to the developers. This question is from our point of view is fundamentally unacceptable, because not allow to objectively assess the level of developments (both scientific and engineering). In addition, it is impossible to conduct a verification analysis of vehicles with regard to specific operating conditions and, therefore, to compare the real performance of devices with design.