Heat exchange – Regenerator – Checker brick structure
Patent
1982-05-12
1986-03-11
Davis, Jr., Albert W.
Heat exchange
Regenerator
Checker brick structure
165 39, 165 40, F28F 2700
Patent
active
045748705
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for controlling the flow of fluids through a heat exchanger in order to maintain the efficiency or effectiveness of the heat exchanger at a predetermined level that is selected with respect to the particular prevailing operational conditions. The inventive method and apparatus eliminate the requirement to use flow meters for measuring either of the two fluid flows through the heat exchanger, even if the flow of one of the fluids varies in an uncontrollable fashion with respect to time.
In many industrial processes there are produced large flows of fluid which have been elevated in temperature, such as heated waste water, and in which the flow of the fluid may exhibit large variations in the flow with respect to time. When the flow rate of the elevated temperature fluid is high, it is attractive to recover as much of the heat content of such fluid as possible by conducting it through a heat exchanger, preferably through a counter-current heat exchanger, and there to transfer the heat to another fluid, making it possible to utilize the heat absorbed in this second fluid. Should the flow rate of one of the fluids vary, then the flow rate of the other fluid also has to be adapted or adjusted correspondingly to keep the thermal transfer in the heat exchanger at or near an optimum value with respect to the particular prevailing operational conditions.
The solution to this problem which seems nearest at hand, and the one that is most commonly used, involves making direct fluid flow rate measurements and controlling the flow of one of the fluids in response to variations in the flow of the second fluid, as well as the other measured parameters. This direct measuring of fluid flow involves technical as well as economic problems in many applications, for example, when confronted with the large magnitudes of variations of fluid flow which may be present when recovering heat from the waste water in an industrial process.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to substantially eliminate the problems mentioned above that are inherent in the prior art.
It is another object of the present invention to provide a method and apparatus for controlling the fluid flow through a heat exchanger in such a fashion that the operation of the heat exchanger is maintained substantially at an optimal level, even when there are large, uncontrolled variations in the flow rate of one of the fluids, and in which the controlling of the flow rate of the second fluid that is being heated is provided without the use of making direct flow measurements.
According to one aspect of the present invention a servo-controlled valve is arranged at the inlet of the second fluid that is being heated, and the valve is controlled in response to the temperatures which are sensed in each of the respective inlet and outlet lines of the two fluids. The temperatures sensed are compared and divided based upon developed temperature relationships, and the valve in the second fluid inlet line is operated accordingly, without any requirement for costly and complicated fluid flow meters.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically represents a heat exchanger and indicates the relevant fluid flow parameters and temperatures useful in the present invention;
FIG. 2 is a graphical representation of the relationship between the temperature and enthalpy levels of the fluids flowing through the heat exchanger of FIG. 1; and
FIG. 3 schematically represents a heat exchanger and control system according to the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 shows a heat exchanger 5, which may be a heat exchanger of the kind used to recover heat from large flows of water at elevated temperatures, such as occur in waste water from an industrial process, and which transfers the heat extracted from such waste water to a second flow of water. Heat exchanger 5 has inlet 1 for "cold" water which is to be heated and whic
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patent: 4381814 (1983-05-01), Funk
Kreith, Frank, Principles of Heat Transfer, International Textbook Co., Scranton, Pa., 1958, pp. 448-452.
Davis Jr. Albert W.
Eslinger Lewis H.
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