A Method for the Evaluation of the Flow Rate of Cryogenic Two-Phase Flows in Venturi Flowmeters Without Separation
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MECHANICAL MEASUREMENTS A METHOD FOR THE EVALUATION OF THE FLOW RATE OF CRYOGENIC TWO-PHASE FLOWS IN VENTURI FLOWMETERS WITHOUT SEPARATION I. A. Arkharov1 and I. D. Kakorin2
UDC 681.121:536.483
We propose a method for the evaluation of the flow rate of cryogenic two-phase flows in flowmeters without separation based on the Venturi tube. The proposed procedure takes into account the equations of state of two-phase medium, i.e., the changes in density, mass vapor quality, and temperature of cryogenic twophase flows depending on the level of pressure in the Venturi tube. It is shown that if we do not take into account the evolution of the parameters of flow, then we get an additional error in the evaluation of the flow rate. Hence, it is impossible to correctly determine the sensitivity and measurement range of the flowmeter. We determine the optimal range of measurements of the pressure drop and propose a procedure of measurement of the flow rate of two-phase cryogenic flows according to the temperature drop in the Venturi tube. The problem of measurement of the flow rates of two-phase cryogenic flows is urgent for accelerators, as well as for the aerospace and gas-transportation equipment. Keywords: two-phase cryogenic flows, flowmeters without separation, Venturi tube, helium.
Introduction. The necessity of measuring the flow rates of two-phase cryogenic flows appears in various branches of contemporary engineering. Thus, for the maintenance of the required functional parameters of superconducting accelerators of elementary particles and high-energy ions, such as NICA [1], FAIR/SIS100/300 [2, 3], LHC [4], Tevatron [5], Nuclotron [6], and TTF [7], it is necessary to be able to cool (and thermostate) all superconducting elements, including magnets, resonators, and power buses down to temperatures less than 4.5 K. For this purpose, it is customary to use systems with forced circulation of helium. In this case, an important problem is to maintain the required values of the parameters of two-phase cryogenic flows, which include the vapor quality, flow rate, temperature, and pressure. The continuous monitoring and maintenance of the parameters within the required ranges of values make it possible, first, to perform flexible regulation of the conditions of cooling of superconducting elements and, second, to optimize the use of liquid helium. The possibility of flexible regulation of the conditions of thermostatting of superconducting elements enables one to minimize the number of emergency situations connected with the transitions of superconducting units into the normal state (quench) and accompanied by large losses of helium. In view of the large amounts of consumption of liquid helium in the accelerating complexes (often more than 104 liters/h), the problem of rational use of liquid helium is directly connected with the necessity of optimization of financial costs spent by the entire complex. The possibility of monitoring of the parameters of two-phase flows of cryogenic fluids is also of high importance for the oth
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