Development of optimization criterions of regenerative heat exchangers

Abstract

The paper offers a simple method for analyzing the operation of regenerative heat exchangers, which significantly reduces the amount of calculations. Similarity criterions of regenerative heat exchange are obtained, which can be used to analyze the relationship of their thermophysical, structural and operating parameters. Similarity criterions were formulated by reducing the differential equation of regenerative heat transfer to a dimensionless form. These mathematical transformations were performed under the condition of regular regime of heating (cooling) of the checkerwork. As a result, three similarity criterions are obtained. The first criterion Kp1 determines the ratio between the heat-accepting capacity of the heat transfer agent and the heat-accumulating capacity of the checkerwork. The second criterion Kp2 is the ratio between the heat-receiving capacity of the heat transfer agent and the intensity of convective heat exchange. The third criterion Kp3 is the ratio between the heat-accumulating capacity of the checkerwork and the intensity of convective heat exchange. Similarity criterions include both the design and performance characteristics of the regenerative heat exchanger. Using these criterions, it is possible to choose a rational operating mode for existing heat exchangers. The proposed method of criteria analysis of regenerative heat exchangers was applied to hot-blast stove. In particular, the conditions for implementing a regular regime in heat exchangers are found. The regular mode is characterized by a linear temperature distribution over the height of the checkerwork, which can be obtained by selecting the appropriate ratio of the reduced costs and the time of the cooling and heating periods. It is also shown in what range it is advisable to change the design and operating parameters of the heat exchanger in order to obtain the maximum heating temperature of the blast-furnace air and the maximum heat availability factor. Since the similarity criteria are universal, the proposed method can be applied to other types of regenerative heat exchangers.