This paper presents an energy performance evaluation of two low-GWP refrigerants, R1234yf and R1234ze(E), as drop-in replacements for R134a. Tests are carried out in a monitored vapor compression ...system combining different values of evaporation and condensation temperature, and without/with the adoption of an internal heat exchanger. The parameters analyzed are volumetric efficiency, cooling capacity and COP and they are presented taking R134a as baseline. Results show that without IHX the average volumetric efficiency for R1234yf and R1234ze is 4% and 5% lower compared with R134a. The cooling capacity obtained with R1234yf and R1234ze is reduced, with an average difference of 9% and 30% without IHX. Also, COP values are about 7% lower for R1234yf and 6% lower for R1234ze than those obtained using R134a. Finally, the use of an internal heat exchanger reduces the COP differences for both replacements.
•We present an experimental comparison between R134a, R1234yf and R1234ze.•We carry out 54 tests in wide range of operating conditions, including use of IHX.•R1234yf and R1234ze volumetric efficiency is lower than that of R134a.•R1234yf and R1234ze cooling capacity is below that of R134a, especially for R1234ze.•IHX can approximate energy performance of R1234yf and R1234ze to that of R134a.
In vitro colonic fermentation of saponin-rich extracts from quinoa, lentil, and fenugreek was performed. Production of sapogenins by human fecal microbiota and the impact of extracts on ...representative intestinal bacterial groups were evaluated. The main sapogenins were found after fermentation (soyasapogenol B for lentil; oleanolic acid, hederagenin, phytolaccagenic acid, and serjanic acid for quinoa; and sarsasapogenin, diosgenin, and neotigogenin acetate for fenugreek). Interindividual differences were observed, but the highest production of sapogenins corresponded to quinoa (90 μg/mL) and fenugreek (70 μg/mL) extracts, being minor for lentil (4 μg/mL). Lentil and quinoa extracts showed a general antimicrobial effect, mainly on lactic acid bacteria and Lactobacillus spp. Significant increases of Bifidobacterium spp. and Lactobacillus spp. were observed for fenugreek in one volunteer. Thus, the transformation of saponin-rich extracts of quinoa, lentil, and fenugreek to sapogenins by human gut microbiota is demonstrated, exhibiting a modulatory effect on the growth of selected intestinal bacteria.
•Extracts from edible insects Acheta domesticus and Tenebrio molitor.•Ultrasound (UAE) or pressurized liquid (PLE) extraction by ethanol or ethanol:water.•All the extracts are antioxidant, which ...correlates with total phenolic compounds.•All the extracts, mainly T. molitor, show inhibitory activity of pancreatic lipase.•Aqueous ethanol is better for antioxidant activity and PLE for inhibition of lipase.
Extracts from the edible insects Acheta domesticus and Tenebrio molitor were obtained by ultrasound-assisted extraction (UAE) and pressurized-liquid extraction (PLE) using ethanol (E) or ethanol:water (E:W). Characterization by GC–MS was performed and total phenolic compounds (TPC), antioxidant activity (DPPH) and pancreatic lipase inhibitory capacity were assayed.
Most extracts, mainly ethanolic extracts, predominantly presented lipids as free fatty acids, followed by aminoacids, organic acids, carbohydrates, hydrocarbons and sterols. The UAE-E:W extracts were different, being characterized by organic acids for A. domesticus, or aminoacids for T. molitor. All the extracts exhibited antioxidant activity, which correlated with TPC values, being the E:W extracts the most effective. All the extracts showed inhibitory activity of lipase, although those from T. molitor and extracted by PLE were the most effective.
Therefore, bioactive insect extracts can be selectively obtained by advanced methods of extraction, being aqueous ethanol preferred for antioxidant activity and PLE for inhibitory lipase activity.
•HFO-1336mzz(Z), HCFO-1233zd(E) and HCFO-1224yd(Z) are numerically studied to replace HFC-245fa.•Mapping of the minimum superheat requirement to ensure the dry compression is provided.•All ...alternatives improve the COP, being benefited from the use of an IHX.•HCFO-1233zd(E) and HCFO-1224yd(Z) present similar behaviour to HFC-245fa.•The alternatives reduce the equivalent CO2 emissions.
This paper analyses the feasibility of HCFO-1224yd(Z), HCFO-1233zd(E) and HFO-1336mzz(Z), three low global warming potential (GWP) refrigerants, as alternatives to HFC-245fa in high-temperature heat pump (HTHP) systems for low-grade waste heat recovery. HTHPs are a sustainable technology that can help to mitigate climate change through the thermal valorisation of the industrial low-grade waste heat. Before presenting and analysing the results, mapping of the minimum superheat degree requirement in the operating range, and the influence of the Internal Heat Exchanger (IHX) on each alternative are studied. The simulations were carried out at condensing temperatures from 115 to 145 °C and evaporating temperatures from 45 to 75 °C, using a single-stage cycle with and without IHX. Finally, the Total Equivalent Warming Impact (TEWI) evaluation is performed to illustrate the environmental effect of each alternative. Attending to the results, HCFO-1233zd(E) improves the COP about 27% compared to HFC-245fa, whereas HFO-1336mzz(Z) and HCFO-1224yd(Z) show an improvement of approx. 21 and 17%, respectively. Although HCFO-1233zd(E) and HCFO-1224yd(Z) present similar suction volumetric flow rate to HFC-245fa, HFO-1336mzz(Z) shows a relative increment up to 80%, and therefore, higher compressor and installation size are expected for this refrigerant. Finally, the TEWI analysis presents a significant reduction of the equivalent CO2 emissions for each low GWP alternative, between 59 and 61%. HCFO-1233zd(E) shows the highest reduction in all the simulation cases, followed by HCFO-1224yd(Z) and HFO-1336mzz(Z).
This work is focused on waste heat recovery of jacket cooling water from Internal Combustion Engines (ICEs). Cooling water heat does not always find use due to its low temperature, typically around ...90 °C, and usually is rejected to the ambient despite its high thermal power. An efficient way to take benefit from the ICE cooling water waste heat can be to increase the power output through suitable bottoming Organic Rankine Cycles (ORCs). Thereby, this work simulates six configurations using ten non flammable working fluids and evaluates their performances in efficiency, safety, cost and environmental terms. Results show that the Double Regenerative ORC using SES36 gets the maximum net efficiency of 7.15%, incrementing the ICE electrical efficiency up to 5.3%, although requires duplicating the number of main components and high turbine size. A more rigorous analysis, based on the system feasibility, shows that small improvements in the basic cycle provide similar gains compared to the most complex schemes proposed. So, the single Regenerative ORC using R236fa and the Reheat Regenerative ORC using R134a seem suitable cycles which provide a net efficiency of 6.55%, incrementing the ICE electrical efficiency up to 4.9%.
•Suitable bottoming cycles for ICE cooling water waste heat recovery are studied.•Non flammable working fluids and various ORC configurations are evaluated.•Double regenerative cycle using SES36 is the most efficient configuration.•Regenerative and reheat regenerative ORCs seem feasible cycles.•Electrical efficiency of the ICE can be improved up to 5.3%.
HFC-245fa is a common working fluid used in Organic Rankine Cycles generating mechanical power from low temperature heat. This paper compares the predicted ORC performance of two novel low GWP ...working fluids, HCFO-1233zd-E and HFO-1336mzz-Z, to HFC-245fa over a wide range of evaporating temperatures, condensing temperatures and vapour superheat values. Expander power output, required pump power input, net cycle efficiencies, mass flow rates and turbine size parameters with HCFO-1233zd-E, HFO-1336mzz-Z and HFC-245fa were compared for a given thermal power input. HCFO-1233zd-E and HFO-1336mzz-Z are predicted to have attractive thermodynamic Rankine power cycle performance. HCFO-1233zd-E would require 10.3%–17.3% lower pump power and would enable up to 10.6% higher net cycle efficiencies than HFC-245fa over the range of cycle conditions examined in this paper. The turbine size required with HCFO-1233zd-E would be up to about 7.5%–10.2% larger than with HFC-245fa. HFO-1336mzz-Z would require 36.5%–41% lower pump power and would enable up to 17% higher net cycle efficiencies than HFC-245fa over the range of cycle conditions examined in this paper. The turbine size required with HFO-1336mzz-Z would be up to about 30.9%–41.5% larger than with HFC-245fa. HFO-1336mzz-Z cycle efficiency is benefitted substantially by a recuperator. The net cycle efficiency increases and the required turbine size decreases relative to HFC-245fa for HCFO-1233zd-E and for HFO-1336mzz-Z at higher evaporating and condensing temperatures.
•The ORC performance of two low GWP working fluids is compared to HFC-245fa.•HCFO-1233zd-E would enable up to 10.6% higher net cycle efficiency than HFC-245fa.•HFO-1336mzz-Z would enable up to 17% higher net cycle efficiencies than HFC-245fa.
Saponin-rich extracts from edible seeds have gained increasing interest and their hydrolysis to sapogenin-rich extracts may be an effective strategy to enhance their potential bioactivity. However, ...it remains necessary to study the resulting chemical modifications of the extracts after hydrolysis as well as their impact on the subsequent bioaccessibility of bioactive compounds. The chemical composition of non-hydrolyzed and hydrolyzed extracts from fenugreek (FE, HFE) and quinoa (QE, HQE), and the bioaccessibility of saponins, sapogenins and other bioactive compounds after an in vitro gastrointestinal digestion was assessed. In general, FE mainly contained saponins (31%), amino acids (6%) and glycerides (5.9%), followed by carbohydrates (3.4%), fatty acids (FFA) (2.3%), phytosterols (0.8%), tocols (0.1%) and phenolics (0.05%). HFE consisted of FFA (35%), sapogenins (8%) and partial glycerides (7%), and were richer in phytosterols (1.9%) and tocols (0.3%). QE mainly contained glycerides (33%), FFA (19%), carbohydrates (16%) and saponins (7.9%), and to a lesser extent alkylresorcinols (1.8%), phytosterols (1.5%), amino acids (1.1%), tocols (0.5%) and phenolics (0.5%). HQE mainly consisted of FFA (57%), partial glycerides (23%) and sapogenins (5.4%), were richer in phytosterols (2.4%), phenolics (1.2%) and tocols (0.7%) but poorer in alkylresorcinols (1%). After in vitro digestion, saponins from FE and QE were fully bioaccessible, sapogenins from HFE displayed a good bioaccessibility (76%) and the sapogenin from HQE was moderately bioaccesible (38%). Digestion of saponin and sapogenin standards suggested that other components of the extracts were enhancing the bioaccessibility. Other minor bioactive compounds (phytosterols, alkylresorcinols, tocols and some phenolics) also displayed optimal bioaccessibility values (70–100%).
Evapotranspiration (ET) plays an important role in integrated water resource planning, development and management. This process is particularly relevant in semiarid regions. The aim of this study is, ...hence, to compare spatial and temporal patterns of actual ET, as well as the temporal trends in two different semiarid forests, Caatinga (Brazil) and Tierra de Pinares (Spain). We used the surface energy balance algorithm for land (SEBAL) to assess actual evapotranspiration (ETa) in both areas. In the Brazilian semiarid forest, Caatinga is the main vegetation, while it is Pinares in Spain. For this purpose, 69 Landsat‐5 and 42 Landsat‐8 images (1995–2019) were used. The Mann–Kendall test was applied to assess the occurrence of trends in precipitation, temperature and potential ET data; and the Temporal Stability Index (TSI) to know which areas have greater seasonal ETa. The annual amplitude of the potential evapotranspiration (ET0) is the same in both areas, however, the Caatinga values are higher. In the Caatinga forest, when ET0 presents its highest values throughout the year, ETa presents the lowest, and vice versa. In the Pinares forest, ETa follows the ET0 dynamics during the year, and the difference between ET0 and ETa is maximum during the summer. The Caatinga forest showed a greater spatial variation of ETa than the Pinares forest as well as a greater extension with lower temporal stability of ETa than the Pinares forest. Both the Caatinga forest and the Pinares forest showed significant positive trends in annual ET0 and ETa. We estimate that the value of ETa increases more rapidly in Pinares than in the Brazilian Caatinga. Taking Caatinga as a hydrological mirror, some consequences are expected to Pinares, such as significant changes in the water balance, increase of biodiversity vulnerability, and reduction of water availability in soil and reservoirs.
Actual evapotranspiration increases more rapidly in Pinares than in the Caatinga. Taking Caatinga as a hydrological mirror, some consequences are expected to Pinares, such as significant changes in the water balance, increase of biodiversity vulnerability and reduction of water availability in soil and reservoirs.
Our understanding of the movement and storage of water in typical Caatinga plants is still limited and often disregarded in water balance calculations. This is why the objective of this work was to ...evaluate the water storage dynamic in typical trees of the Caatinga biome during the dry, rainy and transition period by gauging the water content levels that cause the onset of leaf emergence. In a preserved Caatinga forest, soil and stem water content of six trees of the representative species catingueira (Caesalpinia pyramidalis Tul.) were monitored with low‐cost capacitive sensors. Leaf moisture, leaf area index, leaf and stem water volume, and sap flow density were measured. The emergence of leaves occurred with a stem moisture of 0.32 m3 m−3, and the leaf area index was maximum with a stem moisture of 0.34 m3 m−3. Catingueira plants are able to absorb water below the soil water potential commonly determined as the permanent wilting point (−1.5 MPa). The volume of water stored in the plants represents 108% of the average volume stored in the Boqueirão reservoir during the study period.
The volume of water stored in the catingueira plants could represents more than 100% of the average volume stored in a surface reservoir.
PDF
