An approach is proposed for selecting the most efficient updated (renovated) version of gas cooling system (GCS) based on concordance of energy and economic optimization results. This approach has been put into effect in optimizing the make-up and operation conditions of heat exchanging equipment in the course of its seasonal operation (efficiency criterion−energy cost) as well as in comparing GCS design versions with complete replacement of air cooling devices (ACD) and addition of new ACDs to the existing ones (efficiency criterion−life cycle cost). A general strategy is given for selecting the updated version of GCS of compressor stations (CS), and the characteristics of major Russian-and foreign-made ACDs are compared. An example of solution to problems of compressor stations of gas pipelines (diameter 1420 mm and operating pressure 7.45 MPa) lying under climatic conditions of the central zone of Russia is given.The technical state of the equipment of the gas transporting systems being operated since the 1970s, the change in the gas pipeline operation conditions associated with the depletion of reserves of the existing and development of new fields, and commissioning of new gas transporting systems attest to the fact that it is necessary to update and technically reequip compressor stations (CS) of trunk gas pipelines.Depletion of resources and marked aging and obsolescence of the principal technological equipment (gas pumping units) lead to increased operating costs (excessive consumption of fuel gas, increased frequency, time, and cost of repairs, and maintenance cost) and to reduced operational reliability of the gas pipeline system. In view of this, despite substantial capital investments, the need for complete replacement of gas pumping units (GPU) is indisputable.One of the problems to be solved at the stage of making major technical decisions is selecting unit power and manufacturers of the GPU. As criteria for making this decision, use can be made of net discounted revenue [1] or the discounted cost of the life cycle [2,3]. The second criterion can be taken as optimum for sound and reliable calculation of all components of operational and capital expenditures. In particular, in determining operational costs, attention must be paid to monthly CS operation schedule over a year with due regard for the correctives associated with planned variation in throughput of the gas pipeline [4].

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Based on calculations of energy consumption by air gas cooling devices, an analysis has been made of the efficiency of the methods of control of temperature conditions of the transported gas. Two types of air cooling devices (two-fan 2AVG-75S and multi-fan AVG-85MG) and two control methods (discrete with a part of the fans turned off and partial with use of speed-controllable drives) have been investigated as comparable versions.Raising energy efficiency of air gas cooling devices (AGCD) usable at linear and booster compressor stations (CS) to ensure optimum temperature conditions of gas transportation through the technological section consisting of two successively placed CSs and the gas pipeline section between them is currently an urgent task.The work on raising efficiency of AGCD is being developed in two directions [1, 2]: 1) improving designs of air gas cooling devices (AGCD) to enhance their thermal and aerodynamic efficiency; and 2) improving automatic control systems (ACS) and controlling operation conditions of air cooling devices (ACD) during seasonal operation for attaining the optimum gas cooling temperature at minimal operating costs.New designs of ACDs of the type AVGB-83, AVG-BM-83, and AVG-85MG with increased number of fans (up to six) and reduced drive motor power have been developed. The advantages of these multi-fan ACDs over two-fan ones is more uniform air cooling of the heat exchange surface and greater precision of maintenance of the required temperature level of the gas being cooled owing to increased discretization of control (noncontinuous control) on the pattern of start/stop type of electric motors.The AVG-85MG type of ACDs (six fans with a power of 6.5 kW each) have distinctive characteristics. At low thermal efficiency losses, they ensure substantial saving of electric power for driving the fans as a result of sparse arrangement of the pipe bundle and consequent reduction of its aerodynamic resistance along the cooling airflow [1, 2].Significant progress in development of systems of automatic control of technological processes makes it possible to derive effective algorithms for setting temperature conditions of gas transportation by discrete switching off of a part of the devices or fans [3] as well as by speed control of drives (SCD) of ACD fans [4,5].

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