Selection of organic Rankine cycle working fluid based on unit-heat-exchange-area net power

To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.

The role of fluid polarity in the swelling of sodium-montmorillonite clay:A molecular dynamics and Fourier transform infrared spectroscopy study

Swelling clays are found extensively in various parts of the world, and sodium-montmorillonite(NaMMT) is the main constituent of an expansive clay mineral. In this work, the swelling behavior of NaMMT clay with a wide range of organic fluids, high polar through low polar fluids, is studied using a combination of Fourier transform infrared(FTIR) technique and molecular dynamics(MD) simulations.The construction of the representative clayefluid models is carried out, and the nature of nonbonded interactions between clay and fluids is studied using MD. Our FTIR and MD simulations results suggest the significant nonbonded interactions between Na-MMT clay and polar fluids, such as formamide and water. The nonbonded interactions of Na-MMT with methanol and acetone are significantly less than those in Na-MMT with polar fluids. The interactions of the fluids with various entities of the clay such as Sie O, Fee OH, Mge OH, and Ale OH captured via the spectroscopy experiments and modeling provide a finer understanding of the interactions and their contributions to swelling. The MD simulations are able to capture the band shifts observed in the spectra obtained in the spectroscopy experiments. This work also captures the conformations of interlayer sodium ions with formamide, water, methanol, and acetone during swelling. These nonbonded interactions provide insight into the molecular mechanism that the polarity of fluids plays an important role in the initiation of interlayer swelling, alteration in the orientations, and evolution of microstructure of swelling clays at the molecular scale.

An Innovative Organic Rankine Cycle with Gas-liquid Injector for Pressurization

The organic Rankine cycle （ORC） is an effective way to recycle low temperature exhaust heat but pump for the ORC has several disadvantages such as great difficulty in manufacturing, easily-invited cavitations, low efficiency and high cost. Gas-liquid two-phase injector is a device without moving parts, in which steam is used to drive cold liquid from a pressure lower than the primary steam to a pressure higher than the primary steam. In this paper, the mechanical circulation pump was replaced with a gas-liquid injector. The effect of the evaporate temperature for the system was studied with the organic fluid R123. While this novel ORC can not only improves the energy utilization, but also be suitable for some occasions without power.

Energy-and exergy-based performance evaluation of solar powered combined cycle(recompression supercritical carbon dioxide cycle/organic Rankine cycle)

Nowadays,the recompression supercritical carbon dioxide(R-SCO_(2))cycle has emerged as a promising option for power conversion systems because of its boundless potential to tackle energy and environmental issues.In this study,we examined the performance of the solar parabolic trough collector(SPTC)integrated combined cogeneration system for the purpose of power generation as well as recovery of waste exhaust heat from the R-SCO_(2) cycle with the help of the organic Rankine cycle(ORC).An exergy and energy analysis was performed for a combined recompression cycle(R-SCO_(2)-ORC)by varying the input variables such as intensity of solar irradiation(Gb),pressure at the inlet of SCO_(2) turbine(P_(5)),mass flow rate of SCO_(2)()&mSCO_(2) inlet temperature of SCO_(2) turbine(T5),inlet temperature of main compressor(T_(9))and effectiveness of the high-and low-temperature recuperator( HTR and LTR).Eight organic working fluids were considered for the ORC:R123,R290,isobutane,R1234yf,R1234ze,toluene,isopentane and cyclohexane.The study revealed that R123-based R-SCO_(2)-ORC demonstrates the highest thermal and exergy efficiency:~73.4 and 40.89%at G_(b)=0.5 kW/m^(2);78.8 and 43.9%at P_(5)=14 MPa;63.86 and 35.57%at T5=650 K;74.84 and 41.69%at&mSCO 7kg s;2=/85.83 and 47.82%at T_(9)=300 K;84.57 and 47.11%at HTR 65;=0.85.06 and 47.38%at LTR 65,=0.respectively.Alternatively,R290 showed the minimum value of exergy and thermal efficiency.As can be seen,the maximum amount of exergy destruction or exergy loss occurs in a solar collector field,~58.25%of the total exergy destruction rate(i.e.6703 kW)and 18.99%of the solar inlet exergy(i.e.20562 kJ).Moreover,R123 has the highest net work output,~4594 kJ at T5=650 K and 6176 kJ at T_(9)=300 K.

Impact of combining chlorine dioxide and chlorine on DBP formation in simulated indoor swimming pools

The main objective of this study was to assess the combined use of chlorine dioxide（ClO_2）and chlorine（Cl_2） on the speciation and kinetics of disinfection by-product（DBP） formation in swimming pools using synthetic pool waters prepared with a body fluid analog（BFA）and/or fresh natural water. At 1：25（mass ratio） of ClO_2 to Cl_2, there was no significant reduction in the formation of trihalomethanes（THMs） and haloacetic acids（HAAs） for both BFA solution and natural water compared to the application of Cl_2 alone. When the mass ratio of ClO_2 to Cl_2increased to 1：1, substantial decreases in both THMs and HAAs were observed in the natural water, while there was almost no change of DBP formations in the BFA solution. Haloacetonitriles and halonitromethanes levels in both water matrices remained similar. In the presence of bromide, the overall DBP formation increased in both BFA solution and natural water. For the DBP formation kinetics, after 72 hr of contact time,very low formation of THMs and HAAs was observed for the use of ClO_2 only. Compared to Cl_2 control, however, applying the 1：1 mixture of ClO_2/Cl_2 reduced THMs by 〉 60% and HAAs by 〉 50%. Chlorite was maintained below 1.0 mg/L, while the formation of chlorate significantly increased over the reaction time. Finally, in a bench-scale indoor pool experiment, applying ClO_2 and Cl_2simultaneously produced less THMs compared to Cl_2 control and kept chlorite at 〈 0.4 mg/L, while HAAs and chlorate accumulated over 4-week operation period.