Comparative analysis of recuperator efficiency

The disadvantages of conventional heat exchangers:

• Excessive weight and size;
• Complex or impossible repair ;
• Structures are subjected to buckling and fracture due to thermal stresses followed by the significant difference in thickness of the elements and uneven heating and cooling. In tube recuperators, local overheating zones often arise due to uneven distribution of air flow through the pipes. More air is supplied to short pipe loops due to lower resistance, and less air is supplied to long loops. As a result, due to the uneven distribution of air flow in the weld zone, additional thermal stresses occur.
• In conventional design, there is an uneven distribution of gas flows over the cross section of ducts, which also significantly affects the process of heating the heat transfer surfaces directly in the recuperator itself. In this case, there is an uneven thermal expansion of the elements of the nodes, i.e. thermal stresses occur and, as a result, welded joints and heat exchange surfaces are damaged.

Further, we consider the compactness factor, as comparative analysis of various designs of conventional recuperators and ribbed plate recuperators.

Design of heat transfer surfaces of ribbed plate recuperators provide uniform distribution of incoming flows (both on the flue and on the air sides). The gas flows at the inlet are evenly distributed into numerous streams, and flow motion occurs in narrow slot channels.
These conditions increase the degree of uniform heating of heat transfer surfaces, both from the side of the heating medium and from the side being heated. This, in turn, reduces thermal stresses and, accordingly, structural damage.

Ribbed plate recuperators are made of stainless sheet steel, the thickness of all heat transferring surfaces is usually 1.5 mm.

Advantages of ribbed plate recuperators

• Low weight and dimensional parameters (2-8 times less than traditional recuperators)
• Ability to create any thermal capacity for heat utilization.
• Easy maintenance, transportation, installation and repair.
• Uniform distribution of gas flows directly into recuperator.
• Low thermal inertia of heat transferring surfaces.
• High thermal plasticity.
• Operation in aggressive gas conditions.
• Cleaning and self-cleaning of gas-air ducts from the combustion products due to straight channels, and low pressure drop ensuring significant gas speeds.
• Access to each module during installation, repair and inspection.
• Different steel grades for each module of the heat exchanger, depending on operating conditions.
• Internal compensation of thermal expansions, ribbed plate recuperators can be mounted without compensators.
• Low cost, as well as low operating costs and, accordingly, short payback period (usually less than a year).

Technical data of ribbed plate recuperators

Technical data of ribbed plate recuperators can be selected optimally for specific customer requirements and can vary over a wide range depending on a number of parameters:

• the speed of gas medium (heating, heated);
• the fins pitch and height of fins (ribbed panel);
• the direction of motion of gas medium;
• the number of passes of air ducts; modular sections layout.

Analyzing the above information on existing recuperators and ribbed plate recuperators, we set forth the technical parameters of the above recuperators in the form of tables, where we indicate the initial and calculated parameters according to technical literature sources *. Calculations of ribbed plate recuperators were carried out according to a software developed by Termo Nord Stream LLC — TERMO (version 4.1).