Izdvajanje dihidromiricetina iz lišća biljke Ampelopsis grossedentata mikrovalnom i višefaznom protustrujnom ekstrakcijom

Microwave-assisted extraction (MAE) technique in combination with multi-stage countercurrent extraction (MCE), namely microwave multi-stage countercurrent extraction (MMCE), was evaluated for the extraction of dihydromyricetin (DMY) from Ampelopsis grossedentata. Ethanol, methanol and water were used as extract solvents in the MMCE method. Of the three solvents used, water was found to be the best in extracting DMY from Ampelopsis grossedentata because it had a good extraction yield and is inexpensive, non-toxic and environmentally friendly. The optimal conditions of MMCE for the extraction of DMY can be determined to be the ratio of the extraction solvent to plant material of 30:1, the extraction time of 5 min, the extraction temperature of 110 °C and the microwave power of 600 W. In addition, the extraction efficiency of the MMCE method was compared with that of the microwave static batch extraction (MSBE) under the optimum extraction conditions. It was found that the MMCE method offered higher extraction efficiency than the MSBE method. Thus, the study suggests that the MMCE method provides an alternative technique in terms of both cost and efficiency.Ekstrakcija dihidromiricetina iz lišća biljke Ampelopsis grossedentata pokusno je provedena metodom mikrovalne ekstrakcije u kombinaciji s višefaznom protustrujnom ekstrakcijom. Kao otapalo upotrijebljeni su etanol, metanol i voda. Voda je najbolja za ekstrakciju dihidromiricetina iz Ampelopsis grossedentata jer daje dobro iskorištenje, jeftina je, nije toksična i ekološki je prihvatljiva. Kao optimalni uvjeti ovako kombinirane metode za ekstrakciju dihidromiricetina određeni su: omjer otapala i biljnog materijala 30:1, vrijeme ekstrakcije od 5 min, temperatura od 110 °C i snaga mikrovalova od 600 W. Uspoređujući učinkovitost ove metode s metodom diskontinuirane mikrovalne ekstrakcije u optimalnim uvjetima, vidi se da se veća učinkovitost ekstrakcije postiže višefaznom nego diskontinuiranom mikrovalnom ekstrakcijom. Stoga se, s obzirom na troškove i njezinu učinkovitost, može preporučiti kao alternativna metoda

Solar powered organic Rankine-vapor compression air conditioning

This paper takes solar-powered organic Rankine-vapor compression air conditioning as the research object, and uses thermodynamic simulation methods to study the type of working fluid, system design and influencing factors. The results show that the temperature and condensation temperature of the working fluid have an important effect on the performance of the system. The cooling power per unit area collector and the total efficiency of the system first increase and then decrease with the temperature of the working fluid, and decrease with the increase of the condensation temperature. Through performance comparison, it is found that R123 is a more suitable working fluid, the thermodynamic feasibility of a solar-powered organic Rankine-vapor compression air-conditioning system was demonstrated

Selection of working fluid for organic Rankine cycle used in low temperature geothermal power plant

In this paper, for the low-temperature geothermal organic Rankine (ORC) power generation system, the subcritical saturated vapor cycle is selected as the key research object, the mathematical and physical model of the thermal process of the ORC system is established, and five organic working fluids are selected. With the net power produced per unit mass of geothermal water(PPH) as the optimization target, the optimal parameters of the ORC system are determined. Based on the selection of the best organic working fluid, various parameters that affect the performance and economic performance of the ORC system are analyzed. After simulation calculation, the results show that: when the system takes PPH as the optimization target, the working fluid R245fa can be selected as the best applicable working fluid

Optimization of low temperature geothermal organic Rankine power generation system

In this paper, a low-temperature geothermal organic Rankine Cycle (ORC) power generation system model is established. R245fa is used as the circulating working fluid. The calculation program is compiled using the engineering calculation software EES, and the thermodynamic parameters and thermodynamic properties of the main state points of the ORC are theoretically calculated. The effects of narrow point temperature difference, evaporation temperature, geothermal water temperature and condenser end temperature difference on system performance are analyzed. The results show that the narrow point temperature difference has a significant impact on the ORC performance. Considering system performance and economic cost comprehensively, the best narrow point temperature difference and the best condenser end temperature difference are both within the range of 5–7 K

Performance analysis and working fluid selection of organic Rankine steam compression air conditioning driven by ship waste heat

In order to effectively use the waste heat of ship flue gas and cooling water, in this paper, the organic Rankine-vapor compression refrigeration system is used for air conditioning for ships, and the thermodynamic model of the system is established. The system performance corresponding to the five commonly used working fluids R22, R141b, R236ea, R218 and R601 is analyzed and compared. The working fluid is optimized with the goal of the best system performance. Calculations proves that: regardless of the organic Rankine cycle and vapor compression refrigeration cycle, or for the entire system, R601 is the most suitable working fluid. The temperature of the heat source and the condensing temperature have an important effect on the performance of the system. The hot water temperature can be controlled and adjusted by changing the hot water flow rate, thereby optimizing system performance. At the same time, the determination of the condensing temperature should comprehensively consider the system performance, cooling water pump power, heat exchanger area and system investment to achieve the best overall system performance

Experimental study on horizontal tube spray falling film evaporator in a low temperature geothermal binary cycle power system

The horizontal tube spray falling film evaporator is an efficient evaporation equipment, which has the advantages of good heat exchange effect, small equipment volume and low cost. In this paper, R245fa is used as the working fluid to build a heat transfer test platform for the horizontal pipe spray falling film evaporator of the Organic Rankine Cycle(ORC) power generation system. The effect of factors such as the spray density of the organic working fluid, the initial temperature of the geothermal water and the flow on the heat transfer coefficient outside the tube is studied. The experimental results show that with the increase of the spray density of the organic working fluid, the initial temperature of the geothermal water, and the flow of the geothermal water, the heat transfer coefficient first increases and then decreases

Studies on the performance of distributed combined cooling, heat and power system under off-design conditions based on exergy analysis

This paper adopts the exergy analysis method of second law of thermodynamics to analyze the characteristics of off-design conditions of distributed combined cooling, heat and power system (CCHP). The research results show that off-design conditions are the primary cause of the performance decline of the system. Under the off-design conditions, although the system’s power generation and cooling capacities decline with the reduction of load, the cooling capacity declines more slowly than generating capacity. When the gas turbine load drops under 60%, the distributed combined cooling, heat and power system may not save energy. If the low grade residual heat in the system could be effectively used, it will obviously improve the system’s performance under off-design conditions. Combustor, high pressure producer, and turbine change significantly in grade differences during the change of load in gas turbine, which also means that these three parts are the areas with the highest potential for improvement of the system’s performance. The biggest loss of system exergy occurs in combustor and high-pressure producer

The Development of Swirling Decaying Laminar Flow in an Annular Pipe

Work on the hydrodynamic entry length of pipe and duct flow has been well studied over the years. The assumption of fully developed flows is commonly used in many practical engineering applications (e.g. Moody's chart). For laminar axial pipe flow, the hydrodynamic entry length can be found through the monomial proposed by Kays, Shah and Bhatti (KSB) (Lh=0.056ReDh). In contrast, several approximations exist for fully turbulent flows (i.e. 10Dh-150Dh). Through theoretical and numerical investigations, the hydrodynamic entry length for swirling decaying pipe flow in the laminar regime is investigated. It was found that, the development length Lh for the axial velocity profile changes when a tangential component is added to the mean flow. The reduction in the hydrodynamic length was found to be dependent on the inlet swirl angle θ. The results indicate that a modification can be made on the KSB equation for two-dimensional swirling annular pipe flow