Hydraulic and pneumatic patent forum (18) Spray heat exchange compressed air energy storage system Zhang Guoxian (Shanghai University, Shanghai 200444) 1 Isothermal compression - isothermal expansion is a thermodynamic cycle of air compression and expansion, the ambient temperature under adiabatic conditions When the air at 15 ° C and the initial pressure of 0.1 MPa is compressed to half volume (V = 0.5), the air temperature will rise to 87 ° C. The heat is dissipated through the cylinder wall surface, and the air in the cylinder is lowered to the ambient temperature under equal pressure conditions. The compressed air volume in the cylinder will drop to V=0.4, and then adiabatically expand to V=0.77, the compressed air in the cylinder will be cooled to -51 °C, and the heat exchange between the cylinder wall and the environment will be achieved. At ambient temperature, the compressed air in the cylinder expands to V=1 under isostatic conditions. It can be seen that at high compression ratio, the heat exchange during air compression or expansion is very large. Heat is the key to achieving an isothermal process.
It takes a period of time for the accumulator to rise or cool from one temperature to another. This period of time is the thermal time constant of the accumulator, only when the compression process is slow enough, that is, the compression or expansion time is longer. An isothermal compression or expansion process is possible by greater than the thermal time constant of the accumulator. This is the key issue to be solved in open accumulators.
Spray heat exchange accumulator system patent analysis of transmission and control direction teaching and research work.
It is a spray heat exchange accumulator system. The system is an open accumulator system, the key device of which is an isothermal compression-expansion gas-liquid cylinder 302 driven by a hydraulic system 320. A shower head 334 is arranged on the cylinder head thereof, and is sprayed during the compression process. The cooling water mist sprayed from the head 334 sufficiently cools the compressed air; during the expansion process, the heated water mist sprayed by the shower head 334 sufficiently heats the compressed air to ensure isothermal compression and isothermal expansion. The water cycle is accomplished by a water pump 324 whose pumped water is heat exchanged by an external heat exchanger 322.
The water spray sprayed from the shower head 334 allows the liquid at a unit flow rate to have an extremely large surface area for sufficient heat exchange with the compressed air. If the sprinkler head 334 ejects water droplets or a continuous stream of water, the heat exchange effect is significantly reduced. Whether the sprinkler head 334 ejects water droplets or water mist is related to the Reynolds number Re and the Ohesorge number. The expression of the Ornezog number Oh is: Oh = Hong = we fluid viscous force "Inertial force X surface tension" The physical meaning is the ratio of the viscous force of the fluid to the square root of the product of the inertial force and the surface tension. The greater the viscous force. The raindrop with a diameter of 3mm has an Oh number of about 0.002. It is a relationship between the spray state of the sprinkler and Re and Oh.
It can be seen that increasing the Re or increasing Oh can improve the atomization effect. From the definition of Oh and Re, it can be known that increasing the viscosity of the fluid can raise the high Oh number on page 58, but it will reduce the Re number, which is not a good method.
From the physical meaning of Oh, reducing the surface tension of the fluid can increase the number of Oh without affecting the Re number, which is an effective method. For pure water, Re is greater than 10,000 to achieve atomization. If a surfactant is added to the water, the number of Oh can be significantly increased, so that Re can be atomized as long as it is greater than 7,000.
Under the premise of ensuring atomization, the advantage of reducing Re is that the fluid velocity can be reduced, that is, the power consumption of the pumped fluid is reduced. The mass flow rate of the heat exchange fluid is proportional to the heat transfer amount, that is, the mass flow required to ensure the total heat transfer amount can be achieved by increasing the flow rate of the sprinkler, but this will increase the pump power consumption, so a better method Multiple sprinklers are used.
One thing to consider is that the air is dissolved in water under high pressure (continued from page 54). When the emergency operation of the four-position six-way control rotary valve to the "hand off" valve position, the manual pump can operate the B gas liquid. The hydraulic oil in the tank is pumped into the rod chamber of the hydraulic cylinder, pulling the piston rod to retract, driving the actuator to close the valve, and the hydraulic oil of the rodless chamber of the hydraulic cylinder is returned to the A gas tank.
"Condition valve position" When operating the four-position six-way control rotary valve to the "on" position, the A and B gas liquid tanks are turned on, so that the hydraulic oil level of the two tanks A and B is high.
5 Conclusion According to the basic technical requirements of the gas-liquid linkage actuator in the "Localization Project of Oil and Gas Pipeline Key Equipment" and the given technical parameters, the relationship between pressure and the solubility of air in water. The visible solubility is approximately proportional to the pressure. During the compression process, part of the air is dissolved in the water without being stored in the gas storage tank, in other words causing partial energy loss. During the expansion process, some of the air dissolved in the water will precipitate.
Finally, it is necessary to consider that the compressed or expanded water is no longer dry air, but the wet air, that is, can not be analyzed by the relevant formula of the ideal gas theorem, but the thermodynamic process of compression or expansion must be analyzed according to the air humidity. .
The method proposed by the present invention can be applied to the compressed air energy storage system introduced in the previous two phases.
Note: Enterprises interested in the secondary innovation and development of such products can contact the editorial department of this journal. This paper comprehensively analyzes the technical status of the gas-liquid linkage valve actuators of natural gas pipelines at home and abroad, and has achieved success through trial production, testing and verification.
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