High Pressure Throttling Research Articles

Performance Analysis and Optimization of Supercritical CO2 Recompression Brayton Cycle Coupled With Organic Flash Cycle With a Two-Phase Expander

Abstract In this work, a combined supercritical CO2 recompression Brayton cycle (SCRBC)/organic flash cycle with a two-phase expander (OFCT) system is proposed to improve the thermal efficiency of the SCRBC, which utilizes a two-phase expander to replace the high-pressure throttling valve of a basic organic flash cycle (OFC). In addition, the OFCT is coupled at the waste heat end of the SCRBC as the bottom cycle for the use of waste heat at low temperatures. A comprehensive comparison is carried out for different organic working fluids, including the R123, R245fa, R142B, R236ea, and R600, regarding the thermal performance, environmental effect, and safety levels. Furthermore, influences of various factors on the thermal performance of the combined SCRBC/OFCT cycle are also examined, including the top cycle pressure ratio, top cycle turbine inlet temperature, mass flowrate ratio, evaporation temperature, and the condenser's pinch point temperature difference. A multi-objective optimization approach is employed on the combined SCRBC/OFCT system, which considers both the thermal efficiency and the specific investment cost as the objective function, and the optimization procedure is implemented through the nondominated sorting genetic algorithm II (NSGA-II) algorithm. The Pareto solution set and the compromise solution are finally obtained. The results indicate that the optimized combined SCRBC/OFCT system can improve the thermal efficiency by 11.75% and 9.70% when compared with the SCRBC and SCRBC/OFC, respectively.

Thermodynamic, economic, and environmental analyses and multi-objective optimization of an organic flash regenerative cycle with an ejector for geothermal heat utilization

Based on the existing organic flash regenerative cycle (OFRC), this paper presents a novel OFRC system incorporating an ejector (E-OFRC). The ejector replaces the high-pressure throttle valve for initial flash evaporation and utilizes a low-pressure throttle valve for the second flash evaporation of saturated liquid separated from the first flash. The gaseous working fluid from the second flash is employed as the ejecting fluid. The E-OFRC system employs an ejector to mitigate irreversible losses associated with high-pressure throttle and to drive gaseous working fluids from secondary flash to circulate to enhance overall system performance. Thermodynamic, economic, and environmental models are established, and the impacts of flash pressure (P4), endothermic pressure (P3), and geothermal water temperature (THS,in) on system performance are analyzed and compared with those of the OFRC system. Multi-objective optimization using the Dragonfly algorithm is conducted, while the TOPSIS method is utilized to determine optimal operating parameters for the E-OFRC system. The findings indicate that, in comparison to the OFRC system, the thermal efficiency of the E-OFRC system is only lower under P3, while its thermodynamic, economic, and environmental performance is enhanced under other considered conditions. This underscores the advantages of the E-OFRC system. The optimal operating parameters for the E-OFRC system are THS,in = 423.53 K, P3 = 1.89 MPa, P4 = 0.96 MPa; yielding a net output power of 84.75 kW, a specific investment cost of 2833.54$/kW, and an annual CO2 equivalent emission reduction of 0.807 × 106kg − providing valuable technical support for engineering applications.

Performance improvement analysis of the regenerative dual-pressure organic flash cycle assisted by ejectors

We proposed a dual-ejector-based regenerative dual–pressure organic flash cycle (DEj–RDPOFC) with higher performance than the RDPOFC. The effects of high and low pressures and the entrainment ratio of the ejector on the DEj–RDPOFC performance were analyzed from the viewpoints of thermodynamics and thermoeconomics. An exergy-flow distribution diagram revealed why the DEj–RDPOFC outperformed the RDPOFC. Next, the performances of the DEj–RDPOFC and dual–pressure organic Rankine cycle (DORC) were compared under the same boundary conditions. Finally, the performance of the DEj–RDPOFC was optimized using the nondominated sorting genetic algorithm (NSGA-II). According to the results, the power output of the high-pressure (HP) turbine of the DEj–RDPOFC can be increased by replacing the HP throttling valve (TV) with an ejector (which increases the working fluid dryness of the HP vapor separator and the mass flow rate of the HP turbine) and the low-pressure (LP) TV with an ejector (which increases the HP turbine expansion ratio). The DEj–RDPOFC achieves a higher maximum net power output (Wnet) and a lower corresponding levelized cost of electricity (LCOE) than the DORC. Under the optimum condition, the Wnet and LCOE of the DEj–RDPOFC are 9.71 % higher and 6.59 % lower, respectively, than those of the RDPOFC.

Thermodynamic analysis and efficiency improvement of trans-critical compressed carbon dioxide energy storage system

A novel trans-critical compressed carbon dioxide energy storage (TC-CCES) system was proposed in this paper, then the sensitivity analysis of thermodynamic with a 10 MW unit as the target were conducted, and finally the round-trip efficiency (RTE) of system was improved through distributing the pressure of key nodes and adopting the design method of non-equal pressure ratio. It can be concluded by sensitivity analysis that the system thermodynamic can be improved by increasing the isentropic efficiency of compressors and turbines, increasing the energy release pressure, reducing the outlet pressure of turbines, the pressure drop of high-pressure throttle valve, and the temperature difference of heat exchangers. The RTE of system with non-equal compression ratio and equal expansion ratio can be up to 74 % when the stages are three and the compression temperature is 115 °C. Compared with 65.44 % RTE without the method of pressure distribution at key nodes and non-equal pressure ratio design, the RTE of system is increased by 6.46 %.

A novel low-pressure hybrid dry ice blasting system for improving the tribological and machining characteristics of AISI-52100 tool steel

Hybrid minimum quantity lubrication and compressed carbon dioxide (MQL + CO2) lubri-coolant can play a crucial role in advancing machinability as well as sustainability. However, it is also the fact that the high-pressure throttling of CO2 produces fog and hinders the low-pressure MQL mist to touch the cutting zone adequately. Therefore, a low-pressure novel hybrid MQL-dry ice blasting lubri-coolant technology is anticipated to improve the machinability by providing the cooling and lubrication simultaneously in milling AISI-52100. This low-pressure hybrid dry ice blasting not only reduces an abundance of smog to reduce the cutting zone visibility, but the dry ice grains also behave as carriers to bring MQL-mist to the cutting zone perfectly. In this proposed study, the surface roughness, residual stresses, cutting temperature, surface hardness, tool wear, and cutting forces are measured by varying the cutting speed (75-300 m/min) and feed per tooth (0.04–0.12 mm/z) under hybrid MQL-dry ice blasting lubri-cooling condition in milling AISI52100 tool steel. The results of this study highlighted that as the cutting speed raised from 100 m/min to 300 m/min, an increase in cutting temperature was 22 % at a constant feed per tooth of 0.08 mm/z. Similarly, the decrease in surface roughness was 42 %, tool life reduced to 57 %, surface hardness increased to 9 %, and across-the-feed surface hardness increased to 58 % by the increase of cutting speed from 75 to 300 m/min and constant feed per tooth of 0.08 mm/z. The proof-of-the-concept study showed the machinability advancement under hybrid lubri-cooling technology due to precise penetration of MQL mist and dry ice grains into the cutting zone in terms of ease in chip evacuation, excellent lubrication, and cutting heat dissipation by sublimation of dry ice.

COMBINED MOBILE SUPER CRITICAL CO2 EXTRACTION PLANT

A detailed description of an experimental mobile installation of a new generation, its complete set and the possibilities of supercritical CO2-extraction for processing plant raw materials are presented. New engineering solutions in the operation of a mechanical system were demonstrated, including an improved design of a high gas pressure throttle valve installed in storage tanks and innovations in the system for loading and unloading raw materials using removable nozzles. The operating parameters of the functional elements and their resource are indicated.

Thermodynamic analysis of three ejector based organic flash cycles for low grade waste heat recovery

Systems based on Organic Flash Cycle (OFC) are promising technologies for waste heat recovery application due to a better match of the hot and cold heat transfer curves. However, the large amount of exergy lost during the throttling process, results in a low thermal efficiency for OFC. In this work, ejectors are introduced in basic OFC to replace the low pressure throttle valve, high pressure throttle valve and both two throttle valves, which namely Single Ejector and Single Flash evaporator based OFC (SESF-OFC), Single Ejector and Double Flash evaporators based OFC (SEDF-OFC) and Double Ejectors and Double Flash evaporators based OFC (DEDF-OFC), respectively. The thermodynamic analysis including energy analysis, exergy analysis, the parametric analysis and comparison analysis are evaluated by using steady-state mathematical model and thermodynamic laws. The ejector allows a high pressure fluid to entrain and compress a low pressure fluid to a medium pressure. Hence, the mass flow rate or expansion ratio of turbine can be enhanced, results in all of three ejector based OFCs are more efficient than the basic OFC. When the high temperature fluid with temperature of 453.15 K is set as heat source, the maximum global second law efficiency (ηII,G) of 38.95% belongs to DEDF-OFC followed SEDF-OFC (37.92%), SESF-OFC (33.68%) and basic OFC (31.43%). The SEDF-OFC is more efficient than SESF-OFC, which indicates that the high pressure throttle valve replaced by ejector is a more effective method than the low pressure throttle valve done. Moreover, the four OFCs have been compared with conventional Organic Rankine Cycle (ORC), and the comparison results show that the ηII,G of basic OFC and SESF-OFC are lower than that of ORC, while SEDF-OFC and DEDF-OFC are more efficient than ORC, and the average increment of SEDF-OFC and DEDF-OFC are 10.37% and 15.01%, respectively. Hence, the ejector based OFCs are alternative methods for waste heat recovery application with a high efficiency.

Bond graph modeling of soft switching concept and its parameters optimization

ABSTRACTThe function of a soft switch is to provide a temporarily flow path of high pressure throttle fluid and store it temporally in a small chamber during valve transition, thus leading to passive vibration isolation. In this article, three different on/off controlled hydraulic systems without and with soft switch have been modeled using bond graph technique and simulated to analyze the performance of the soft switch. Some key parameters of the soft switch are identified and their values are optimized through multiple-run simulation. Thereafter, a relationship has been derived between the soft switch parameters and the overall energy loss of the system using regression analysis. It has been observed that the total energy loss in the system with soft switch is about one-third of that when the system is operated with relief valve only.

СИСТЕМЫ ТЕПЛО- И ХЛАДОСНАБЖЕНИЯ УСТАНОВОК ФАЗОВОЙ СЕПАРАЦИИ, ИСПОЛЬЗУЕМЫХ В ТЕХНОЛОГИЯХ ПРОИЗВОДСТВА ЧИСТЫХ ТЕХНИЧЕСКИХ ГАЗОВ

In technologies of obtaining pure industrial gases an important role is assigned to heat and cold supply of phase separation units. They provide a cooling level of 125 K in the process of purification krypton, 175 K — xenon and 243 K — freon-216. We researched a cooling system of a multipurpose rectification unit for the production of krypton and xenon using adsorption-rectification technology. It is shown that using an intermediate cooling circuit on the basis of liquid nitrogen in the form of a thermosiphon provides a higher efficiency compared with high-pressure throttling cycles. The cascade system allows changing the temperature level in a wide range of temperatures by refueling the corresponding intermediate refrigerants; besides, it is also is less energy-consuming. As a system of heating and cooling the rectification column for purifying R216 from low-boiling impurities, a cascade system including a steam compressor refrigerating machine and a heat pump is proposed. The possibility of working on alternative natural refrigerants (R717, R22 and R407b) of a refrigerating machine and efficient working bodies (R114, R142b and R600a) of a heat pump has been proved.

Modelling the Effect of Processing Parameters of Continuous Flow High Pressure Throttling System and Microfluidizer on Particle Size Distribution of Soymilk

Abstract Texture, appearance, and emulsion stability of soymilk are affected by the size and distribution of suspended particles. To produce soymilk which contains all solids in the soy, whole dehulled beans were used in the study. A microfluidizer with throttling valve attachment was used to study the influence of various pressure levels on the particle size distribution of soymilk. Soymilk was processed with a continuous flow high pressure throttling (CFHPT) system to study the effects of different pressures and flow rates in the temperature rise and particle size distribution of soymilk. The results showed that there existed a significant effect of flow rate through the CFHPT on the particle size suspended in soymilk. Temperature rise was proportional to increase in pressure of the CFHPT system. Significant decrease in particle size of soymilk was obtained by increasing pressure for both CFHPT and microfluidizer. Empirical models were established between the pressure applied, volume fraction of particle size, and particle size diameter obtained for soymilk in each system.

Cascade units for neon isotope production by rectification

The basics of neon isotope separation by the distillation method at T = 28 K are discussed. The required numbers of transfer units at the top and bottom column sections are calculated for different loads. The experimental characteristics of packed rectification columns are presented and examples of the cascade are discussed. A configuration for a cryogenic circuit based on a high-pressure throttle neon cycle with intermediate nitrogen cooling is presented. The necessity for and the technical feasibility of creating a driver pressure difference between the columns for different stages are demonstrated.

Observation of Injured E. coli Population Resulting from the Application of High‐Pressure Throttling Treatments

This study used flow cytometry (FC), epifluorescent microscopy (EM), and conventional culture media (PC) to evaluate the potential for high-pressure throttling (HPT) to produce injury in E. coli. E. coli cells suspended at a concentration of approximately 8 log (CFU/mL) in Butterfield's phosphate buffer and UHT skimmed milk, were treated with HPT at pressures ranging from 35 to 283 MPa. Cells were stained with SYTO 9 and propidium iodide (Live/Dead Baclight kit) to assess their membrane integrity. MacConkey and Tryptone Soy agars and a modification of the thin agar layer method were used to determine injured and non-injured cells. PC results indicated a reduction in E. coli counts as pressure increased but no significant injured population was detected in either matrix. However, FC and EM observations indicated that the membrane integrity of a portion of the bacterial population was affected by HPT, producing different degrees of cell injury that could be sublethal. The percentage of this heterogeneous population increased with applied pressure. These results reassert the importance of understanding the potential of new processing treatments to produce sublethally-injured bacteria, and developing appropriate detection techniques.

Microbial Inactivation Kinetics in Soymilk during Continuous Flow High‐Pressure Throttling

The thermal resistance of Clostridium sporogenes PA 3679 ATCC 7955 was determined in soymilk (pH 7) and 0.1% peptone water (pH 7) by the capillary tube method. In the continuous flow high-pressure throttling, the temperature of soymilk increased due to instantaneous pressure release and the additional heat was supplied by a heat exchanger to achieve the set temperature. The soymilk was immediately cooled after a short preset hold time to below 40 degrees C. A significant increase in the heat resistance was observed in C. sporogenes spores when heated in soymilk in comparison to 0.1% peptone water. The D(121)-value for spores in soymilk was approximately 3-folds higher than peptone water. The z-value was also much higher in soymilk as compared to that in 0.1% peptone water. Continuous flow high-pressure throttling (HPT) from 207 or 276 MPa to atmospheric pressure reduced the microbial populations in inoculated soymilk up to 6 log cycles when the holding times were 10.4, 15.6, and 20.8 s and the process temperatures were 85, 121, 133, and 145 degrees C, respectively. The sporicidal effect increased as the operating pressure, time, and temperature were increased. More injured spores were found at 207 MPa than at 276 MPa, indicating that lower pressure caused cell injury whereas high pressure caused cell death.

Effect of Continuous Flow High‐Pressure Throttling on Rheological and Ultrastructural Properties of Soymilk

Soymilk processing uses a filtration or centrifugation step to remove coarse solids in the comminuted soy. The objective was to utilize the whole beans and determine the effect of continuous flow high pressure throttling (CFHPT) process in reducing particle size and narrowing down the particle size distribution. The rheological and ultrastructural properties of such soymilk were also determined. Whole dehulled soybeans and deionized water were ground in a food processor before comminution in a Megatron (process M) or a Fitzmill (process F) or a Stonemill (process S). The comminuted slurry was homogenized at pressures of 69, 103, 138, 207, and 276 MPa using a CFHPT system, heated to 80 degrees C in a tubular heat exchanger prior to depressurization, and held at elevated temperatures of 97, 106, 114, 131, and 148 degrees C, respectively, for each applied pressure after throttling. To avoid flashing, back pressure was applied after the holding tube and soymilk was cooled immediately. Process M produced soymilk with smallest particle size and the highest apparent viscosity. All soymilk samples showed non-Newtonian pseudoplastic flow behavior. Ultrastructural images showed a clear protein network with very small fat globules entrapped in the protein matrix. Particles were uniformly distributed when the highest pressure treatment was applied for process M, which was considered as the best process.

Functional Properties of Skim Milk Processed with Continuous High Pressure Throttling

The objective of this project was to evaluate the functional properties of continuous high pressure throttled milk. Milk was obtained from the University of Georgia dairy farm and separated. Skim milk (9% solids) was divided, and one-half of the volume was concentrated by ultrafiltration to 18% total solids. Samples of concentrated and unconcentrated milk were subjected to treatment with 310MPa (45,000psi) of pressure by a process of continuous high pressure throttling for a maximum of 0.3s or were not pressure treated. All milk samples were chilled to 4°C following treatment and then evaluated for functional properties. Only pressurized milks (9 and 18% solids) produced stable foams. The emulsion stability index, measured at 6-h intervals for 24h, was lower for the pressurized concentrated milk samples, but pressure treatment produced more stable emulsions in unconcentrated milk. Pressure had no significant effect on interfacial tension. Values for surface tension were higher for pressurized milk samples. Pressurized milks were more viscous. Lightness (L*), greenness (a*), and blueness (b*) were affected by pressure treatment in unconcentrated milk; pressurized milks had lower L* (less white), a* (greener), and b* (bluer) values than the unpressurized milks. In concentrated milk, pressure treatment imparted greener color only. Creamers made with pressure throttled milk samples (both systems) were stable (i.e., did not exhibit feathering) when added to coffee solutions.

95/01476 Numerical analysis of natural convection of low Prandti number fluids heated from below

The objective of this project was to evaluate the functional properties of continuous high pressure throttled milk. Milk was obtained from the University of Georgia dairy farm and separated. Skim milk (9% solids) was divided, and one-half of the volume was concentrated by ultrafiltration to 18% total solids. Samples of concentrated and unconcentrated milk were subjected to treatment with 310 MPa (45,000 psi) of pressure by a process of continuous high pressure throttling for a maximum of 0.3 s or were not pressure treated. All milk samples were chilled to 4°C following treatment and then evaluated for functional properties. Only pressurized milks (9 and 18% solids) produced stable foams. The emulsion stability index, measured at 6-h intervals for 24 h, was lower for the pressurized concentrated milk samples, but pressure treatment produced more stable emulsions in unconcentrated milk. Pressure had no significant effect on interfacial tension. Values for surface tension were higher for pressurized milk samples. Pressurized milks were more viscous. Lightness (L*), greenness (a*), and blueness (b*) were affected by pressure treatment in unconcentrated milk; pressurized milks had lower L* (less white), a* (greener), and b* (bluer) values than the unpressurized milks. In concentrated milk, pressure treatment imparted greener color only. Creamers made with pressure throttled milk samples (both systems) were stable (i.e., did not exhibit feathering) when added to coffee solutions.

Parameter Estimation for Reheat Steam Turbines

This paper describes the problems and their solution for the identification of parameters for low-order models of reheat steam turbine generators using single input/output measurements. Because the reheater is effectively in parallel with the highpressure throttle valves but has a much greater time constant the overall system is 'stiff' and presents numerical problems to the estimator. By adopting a compound psuedo-random test signal and a two-stage estimator structure the problem is overcome, as shown by supporting field tests on a large turbine.

Influence of Reverse Osmosis on Milk Lipolysis

Reverse osmosis concentration of subpasteurized whole milk may cause excessive shearing of milk fat globules and increase lipolytic cleavage of fatty acids from milk triglycerides. Free fatty acid content of subpasteurized milk was increased during reverse osmosis. The type of device used for pressure regulation in the reverse osmosis unit was a key factor that was related to increase of free fatty acids. Use of either a high pressure throttle valve or a diaphragm valve caused substantial increases of free fatty acids. Pressure regulation by various lengths of milk retentate exit pipes of small diameter were evaluated as a replacement for a valve. Pressure regulation could be accomplished by appropriate reduction of the diameter of retentate exit pipe. This method of pressure regulation allowed concentration of subpasteurized whole milk by reverse osmosis without causing an increase of concentration of free fatty acids.