Saturation Efficiency Research Articles

Aerodynamic analysis and hygrothermal transfer characteristics of cellulose evaporative cooling pads: A case study applied to protected agriculture

Evaporative cooling pads are clean media for cost-effective temperature management. However, the spatially integrated microclimate resulting from heat and mass transfer in the evaporative cooling pad is an uncertain and nonlinear complexity. Therefore, this purpose of this study is to present an innovative prediction model with computational fluid dynamics and evaluate the operating scenarios and geometrical properties of wet pads from quantitative metrics such as saturation efficiency and pressure drop. The reliability of the established numerical model of wet pads was verified by wind tunnel experiments and existing experiments, which predicted the outlet conditions in satisfactory conformity. The results showed that a wet pad with 8 mm ripple height and 19.6 mm ripple distance exhibits the best prospective, with energy consumption and specific water consumption reduced by 45.28 % and 26.26 %, respectively. Meanwhile, the cross strategy of 45_45° corrugation obliquity reduces the pressure drop by 18.95 %, providing uniform supply air distributions. The heat exchange of the wet pad is mainly concentrated within the first 35 mm from the inlet section, while the mass exchange of the wet pad is concentrated within the first 60 mm. The range of frontal air velocity with 0.9–2.5 m/s is recommend for the evaporative cooling system.

Analysis and design of hybrid Doherty-Outphasing power amplifier

This paper theoretically analyzes the network phase solution space under Doherty, Outphasing, and hybrid modes. A dual-input wideband Doherty-Outphasing power amplifier (DOPA) design method is proposed. This method can ensure that the output back-off (OBO) amount is further increased based on the OBO amount of Doherty power amplifier. To prove the reliability of the proposed method, a hybrid DOPA power amplifier in the band of 1.7–2.4 GHz with an OBO amount of 12 dB is designed. The experimental results also show that the output power of the hybrid DOPA is 48.6–49.5 dBm in the band of 1.7–2.3 GHz, and the saturation efficiency is 57%–63%. The efficiency at 12 dB, 9 dB and 6 dB OBO is 42%–50%, 46%–59% and 50%–63% respectively. The digital pre-distortion correction is carried out at 1.8, 2.1 and 2.3 GHz frequency points, and the adjacent channel power ratio is lower than -47.7 dBc. Simulation and experiment results can verify the effectiveness and correctness of the proposed method. To the best of our knowledge, it is the first time to achieve such a wide bandwidth to the hybrid DOPA with the proposed design method.

The Best Design for a Direct Evaporative Cooling System Based on Pressure Drop at Desired Saturation Efficiency: A Cost–Benefit Optimization

The Best Design for a Direct Evaporative Cooling System Based on Pressure Drop at Desired Saturation Efficiency: A Cost–Benefit Optimization

Reducing transport via extreme flux-surface triangularity

Based on a gyrokinetic analysis of and extrapolation from TCV discharges with large negative and positive triangularity δ, the potential of extreme |δ| in reducing turbulent transport is assessed. Linearly, both positive and negative δ can exert a stabilizing influence, with substantial sensitivity to the radial wavenumber kx . Nonlinear fluxes are reduced at extreme δ in a trapped-electron-mode regime, whereas low-amplitude ion-temperature-gradient turbulence is boosted by large negative δ. Focusing on the former case, nonlinear fluxes exceed quasilinear ones at negative δ, a trend that reverses as δ > 0. A change in saturation efficiency is the cause of these features: the zonal-flow residual is boosted at δ > 0, reducing fluxes compared with the linear drive as δ is increased, and a shift towards larger zonal-flow scales occurs with increasing δ due to finite-kx modes weakening with δ.

Efficient noncollinear optical parametric chirped-pulse amplification in oversaturation region

Optical parametric chirped pulse amplification (OPCPA) is the workhorse to generate intense ultrashort pulses across a broad wavelength range. Typically, OPCPA operates in the saturation region, but barely in the oversaturation region due to efficiency drop caused by back conversion. Through numerical simulations, we reveal the potential of noncollinear OPCPA to achieve significantly higher conversion efficiency in the oversaturation regime compared to the recognized saturation efficiency. This enhancement stems from the suppression of back conversion facilitated by noncollinearity-induced idler dissipation. Besides offering high efficiency and robustness, the oversaturated noncollinear OPCPA also exhibits acceptable spatial and temporal properties, as well as spatiotemporal coupling properties. These findings hold promise for enhancing the final stage of a noncollinear OPCPA system, where a high conversion efficiency is essential.

A Gallium Nitride (GaN) Doherty power amplifier chip design based on series RC stability network

SummaryThis paper presents Doherty power amplifier (DPA) based on gallium nitride (GaN) technology, incorporating a parallel grounded network with series RC elements in front of the carrier and peaking amplifiers to enhance circuit stability. In comparison to the traditional series network with parallel RC structure, this configuration effectively reduces the sensitivity of the stability factor K to the capacitance value within the stability network. Consequently, it mitigates the impact on various performance indicators such as gain and drain efficiency, addressing the issue of measurement performance deviation caused by inaccurate capacitance models in the simulation files, which is particularly crucial for DPA. As a result, the circuit exhibits improved consistency in design and processing. With full band stability, the DPA achieves a saturation output power of approximately 29.8 dBm at 28 GHz, a saturation efficiency of 38.2%, and a 6‐dB back‐off efficiency of 29.6%.

Experimental and analytical study of the energy and exergy performance for different evaporative pads in hot and dry climate

In this work, effects of using different evaporative cooling pads (ECPs) on the energetic and exergetic efficiency of a direct evaporative air cooler (DEAC) have been theoretically and experimentally investigated. Three types of ECPs were used, i.e., honeycomb cellulose cooler pad (HCCP), shading-cloth cooler pad (SCCP), and aspen wood wool cooler pad (AWWCP). For SCCP and AWWCP, a 3-cm pad thickness was used, while for the HCCP, three different values of pad thickness were used, i.e., 3, 5, and 7 cm. Tests were carried out using air velocities of 8, 14, and 19 m/s, measured at the DEAC outlet. Engineering equation solver (EES) used for performing the required calculations of the various parameters affecting the thermal performance of the DEAC, i.e., dry bulb temperature at exit (Tdbo), relative humidity at exit (RHo), mass of water evaporated, saturation efficiency, energetic efficiency (ηen), exergetic efficiency (ηex), and the overall exergetic efficiency (ηexoverall). Results showed the great effectiveness of HCCP compared to the other studied types. HCCP showed the highest energetic efficiency reached 103 % for 3 cm thickness of the ECP, and the highest exergetic efficiency of about 19 %. All with the highest temperature difference, achieving 10.3 °C.

A multi-objective optimization based doherty power amplifier and its matching network optimization method.

In the actual design process of traditional power amplifiers, there is a problem of being cumbersome and unable to simultaneously meet low power and saturation modes. Therefore, an improved multi-objective optimization algorithm proposed by decomposition is introduced to optimize its matching network to achieve overall optimization design of power amplifiers. The algorithm, matching network, and optimized power amplifier performance are simulated and verified. The experimental outcomes denote that on the logic function with Zener diode transistor, the proposed algorithm has a mean generation distance index of 5.03E-3, which is lower than most algorithms. Its overall comprehensive performance is better than the comparison algorithm, and compared to the comparison algorithm, it converges more quickly in the early stage of iteration on 1 and 2, and tends to stabilize in the 40th generation, and completes convergence in the 80th generation. In addition, the optimal solution has already begun to appear around the 25th generation and reached saturation around the 70th generation. At the same time, in the actual working bandwidth, the optimized power amplifier saturation efficiency reaches 51.5%~61.9%, and the efficiency at 6dB power backoff is about 44.4%~56.5%. Overall, the algorithm proposed in the study is effective in optimizing power amplifiers and their matching networks, effectively solving the problem of insufficient efficiency in low power modes in traditional designs.

Evaluating the viability and performance enhancement of Ensete ventricosum fibre pads in evaporative cooling system

This study mainly focused on enhancing the water absorption capacity of organic fibres to improve the performance of evaporative cooling pads. The enhancement involved immersing 10 g of Ensete fibre in different volumes of NaOH–water solution (for the cases of 0, 5, 10, and 20% NaOH and the remaining water). Saturation efficiency and predictive mean vote (PMV) were used to quantify performance assessment. The maximum saturation efficiency is 75.66%. The computed PMV for the hourly of 8:00 am through 5:00 pm ranges from –3.17 to –0.70 with much too cool in the early morning at 8:00 am comfortably cool at 9:00 am and 11:00 am and comfortable at 10:00 am, 12:00 am, 1:00 am, 2:00 am, 3:00 pm, 4:00 pm and 5:00 pm. Moreover, from 12:00 pm to 4:00 pm, they remained on the ASHRAE scale of thermal sensations, providing the best alternative to an evaporative cooling pad in the study area and similar air conditions for comfort applications.

Experimental study of the influence of pad angle on the thermal performance of a direct evaporative cooling system

One of the most important parts of direct evaporative cooling systems is the cooling pad. Pads vary in materials and construction features. The parameters studied in the performance of the pads are air speed, pad thickness, geometrical characteristics, and its configuration and the provided water flow rate. The performance of the pads is usually determined through saturation efficiency, pressure drop, temperature drop and humidity increase in the treated air, evaporation and water consumption, cooling capacity, coefficient of performance, and heat and mass transfer coefficients. Since the geometry and how to place the pad in the evaporative cooling system is one of the most important issues related to the performance of such systems, the present work experimentally investigates the amount of cooling and evaporation of the direct evaporative cooling system under 5 different angles of placement of the cellulose pad in relation to the vertical position. It includes angles of 0^circ, 5^circ, 10^circ, 15^circ, and 20^circ in 5 different air speeds, 2 different inlet water flow rates, 2 inlet air temperatures, and 2 different inlet water temperatures. Results show that the lowest output temperature, highest air relative humidity, highest coefficient of performance (about 12% more than 0^circ), highest saturation efficiency, and highest evaporation rate are obtained in the case of a 15^circ of cooling pad placement angle.

Estimation of ecosystem respiration and photosynthesis in supersaturated stream water downstream of a hydropower plant

The estimation of whole stream metabolism, as determined by photosynthesis and respiration, is critical to our understanding of carbon cycling and carbon subsidies to aquatic food-webs. The mass development of aquatic plants is a worldwide problem for human activities and often occurs in regulated rivers, altering biodiversity and ecosystem functions. Hydropower plants supersaturate water with gases and prevent the use of common whole stream metabolism models to estimate ecosystem respiration. Here we used the inert noble gas argon to parse out biological from physical processes in stream metabolism calculations. We coupled the O2:Ar ratio determined by gas chromatography in grab samples with in-situ oxygen concentrations measured by an optode to estimate aquatic plant photosynthesis and ecosystem respiration during supersaturation events through a parsimonious approach. The results compared well with a more complicated two-station model based on O2 mass balances in non-supersatured water, and with associated changes in dissolved CO2 (or dissolved inorganic carbon). This new method provides an independent approach to evaluate alternative corrections of dissolved oxygen data (e.g. through the use of total dissolved gases) in long term studies. The use of photosynthesis-irradiance models allows the determination of light parameters such as the onset of light saturation or low light use efficiency, which could be used for inverse modelling. The use of the O2:Ar approach to correct for oversaturation may become more applicable with the emergence of portable mass inlet mass spectrometers (MIMS). Photosynthesis was modest (2.9-5.8 g O2 m2 day−1) compared to other rivers with submerged vegetation, likely indicating nutrient co-limitations (CO2, inorganic N and P). Respiration was very low (-2.1 to -3.9 g O2 m2 day−1) likely due to a lack of allochthonous carbon supply and sandy sediment.

Continuous Class-J/F-1 Mode Asymmetrical Doherty Power Amplifier With Extended Bandwidth and Enhanced Efficiency

This article presents a design method of continuous class-J/F <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1}$</tex-math> </inline-formula> mode asymmetrical Doherty power amplifier (DPA) using the phase tuning technique. By properly adjusting the phase characteristics of the output matching network (OMN) of the carrier amplifier (CA) and the harmonic impedances of the postmatching network (PMN), the load impedance of CA can be effectively tuned to meet the impedance requirements of continuous class-J and continuous class-F <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1}$</tex-math> </inline-formula> modes at the power back-off point, which thus extends the bandwidth with enhanced power back-off efficiency. In addition, the proposed DPA can theoretically achieve saturation efficiency of more than 58.7% over the working frequency. Based on the proposed method, a broadband continuous class-J/F <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1}$</tex-math> </inline-formula> mode asymmetrical DPA operating from 1.3 to 2.5 GHz (63%) is designed and measured. Under the continuous wave stimulation, the measured 9-dB back-off, 6-dB back-off, and saturation efficiencies are 55%–62.5%, 52.4%–65.6%, and 62.5%–81%, respectively. The measured 9-dB back-off and saturation gains are 8.8–11.3 and 7–10.6 dB, respectively. When driven by a 20-MHz long-term evolution (LTE) modulated signal with 9.9-dB peak-to-average power ratio (PAPR), the measured average efficiency is 47%–59% and the adjacent channel power ratio is from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 23.6 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 31.7 dBc.

Investigation of the Water-Invasion Gas Efficiency in the Kela-2 Gas Field Using Multiple Experiments

Although improving the recovery of water-invaded gas reservoirs has been extensively studied in the natural gas industry, the nature of the efficiency of water-invaded gas recovery remains uncertain. Low-field nuclear magnetic resonance (NMR) can be used to clearly identify changes in water saturation in the core during high-pressure water-invasion gas. Here, we provide four types of water-invasion gas experiments (spontaneous imbibition, atmospheric pressure, high-pressure approximate equilibrium, and depletion development water-invasion gas) to reveal the impact of the water-invasion gas efficiency on the recovery of water-invasion gas reservoirs. NMR suggested that imbibition mainly occurs in medium to large pores and that residual gas remains mainly in large pores. The amount of gas driven out from the large pores by imbibition was much greater than that driven out from the small pores. Our findings indicate that the initial gas saturation, contact surface, and permeability are the main factors controlling the residual gas saturation, suggesting that a reasonable initial water saturation should be established before the water-invasion gas experiments. Additionally, the water-invasion gas efficiency at high pressures can be more reliably obtained than that at normal pressures. After the high-pressure approximate equilibrium water invasion for gas displacement, a large amount of residual gas remains in the relatively larger pores of the core, with a residual gas saturation of 42%. In contrast to conventional experiments, the residual gas saturation and water displacement efficiency of the high-pressure approximate equilibrium water invasion for gas displacement did not exhibit a favorable linear relationship with the permeability. The residual gas saturation ranged from 34 to 43% (avg. 38%), while the water displacement efficiency ranged from 32 to 45% (avg. 40%) in the high-pressure approximate equilibrium water invasion for gas displacement. The residual gas saturation in the depletion development water-invasion gas experiment was 26–40% (average: 33%), with an efficiency ranging from 45 to 50% (average: 48%), indicating that the depletion development experiment is closer to the actual development process of gas reservoirs. Our findings provide novel insights into water-invasion gas efficiency, providing robust estimates of the recovery of water-invasion gas reservoirs.

Design of High-efficiency Continuous Class F Doherty Power Amplifier

The high efficiency of the saturation state and rollback state is an important part of the front end of modern wireless communication systems. Improving the efficiency of RF power amplifiers is of great significance for energy saving and amplifier performance. Based on the traditional Doherty power amplifier, the harmonic suppression network is introduced before the fundamental frequency matching, so that the second harmonic impedance and third harmonic impedance can achieve continuous class F impedance matching conditions, and then the saturation efficiency and regression efficiency can be improved without affecting the fundamental wave matching. The results of the simulation show that the saturation efficiency of the Doherty amplifier reaches 73.94%~77.22%. The drain efficiency of back-off 6 dB reaches 61.80%~62.92%. The average saturation drain efficiency is 75.58%, and the average back-off 6 dB drain efficiency is 62.36%.

Dual-Band Dual-Output Doherty Power Amplifier for Unsynchronized Time-Division Duplexing

Conventional multiband power amplifiers (PAs), when working in time-division duplex (TDD), require the transmit–receive intervals of all bands to be synchronized. This is an undesirable constraint in modern radio base stations. This article proposes a dual-output dual-band Doherty PA (DB-DPA) that enables the loading of one band to be switched on-and-off without impacting the other band in normal transmission. A thorough analysis of the proposed dual-output DB-DPA architecture is presented, and a dual-output DB-DPA prototype operating at 1.4 and 2.6GHz has been designed as a proof of concept. The large-signal measurements of the prototype DB-DPA indicate Doherty behavior at both frequencies with over 56% saturation efficiency and 45% efficiency at 6-dB power back-off (PBO). Furthermore, single-band and concurrent dual-band linearized modulated measurements, using 10-MHz new radio (NR) signals with 6-dB peak-to-average power ratio (PAPR), demonstrate the linearizability of the proposed DB-DPA and its usefulness for unsynchronized TDD applications.

Parametric Studies on a Two-Stage Evaporative Cooler During Tropical Climates in India

Abstract This research study aims to work out the best possible performance parameters for a two-stage direct–indirect evaporative cooler (IDEC) when it is operated in Indian climatic conditions. A numerical simulation model has been developed to estimate temperature, relative humidity, cooling capacity, and saturation efficiency for a direct evaporative cooler (DEC), when it is operated during hot and humid and hot and less humid conditions in Chennai city. Simulation results have been corroborated with those obtained from experiments. Simulation techniques have also been extended for a fin and tube heat exchanger, which acts as IDEC. Both DEC and IDEC are combined and developed into a two-stage evaporative cooler in which performance studies have been carried out. Performance parameters are optimized for all three modes of evaporative cooling. These studies reveal that the DEC system with optimized parameters has a better approach to wet bulb temperature (WBT). Hence, cooling effectiveness of DEC depends on the ambient air WBT of Indian localities. IDEC systems perform better in places where ambient air WBT is less, either hot and less humid or hot and dry climates. Two-stage evaporative cooling is the preferred technique for Chennai weather when compared with direct and indirect cooling methods. In this cooler, spray water temperature approaches the WBT of IDEC cooled air, whereas it is reduced well below ambient air WBT and approaches ambient air dew point temperature. Also, when ambient air is cooled in this new cooler, dry bulb temperature (DBT) of IDEC cooled air can be reduced below ambient air WBT.

Development and Application of a Mathematical Simulation Model to Evaluate Environmental Performance of Greenhouses Using Physical and Climatic Indicators

This study was conducted to determine and apply a mathematical model to simulate the environmental and climatic parameters to evaluate the performance of different greenhouses in three areas within the Khartoum North – Sudan (Date Palm Technology Company., Abu Halima Center and Khartoum University). The assessment method depends on development of a computer simulation model to generate from house physical characteristics and climate data ten environmental performance evaluation indicators (Relative moisture efficiency; Cooling effectiveness, Moisture saturation efficiency; Water consumption rate; House overall efficiency; House ventilation rate, Optimum internal temperature and internal relative humidity).The result of application of the evaluation model for nine greenhouses in three different locations in Khartoum North reveals that there is no significant differences (P = 0.05) in evaluation indicators between the three studied areas. The study concluded that additional work is needed to upgrade the mode of running greenhouse crop cultivation system with regards to: using sustainable and energy efficient cooling and ventilation technologies, adopting new techniques to conserve water and its efficient utilization, introducing properly adapted materials for high temperatures and strong solar radiation, and accessibility of technologies such as automation systems. In the current system moisture use efficiency in particular found to be lower than expected and measures to improvement are critically needed. With respect to the system efficiency and utility of fan and pad greenhouse the effectiveness of cooling system is function of internal environmental parameter (temperature and relative humidity with negative relation). The evaluation model shows that cooling efficiency tends to go up in the areas with low relative humidity.

An Efficient Broadband Symmetrical Doherty Power Amplifier With Extended Back-Off Range

In this brief, a symmetrical Doherty power amplifier (DPA) which exhibits enhanced efficiency, bandwidth and output power back-off range by phase compensation, is proposed. This proposed architecture compensates the phase deviation between main and auxiliary amplifiers mainly caused by the load modulation circuit and parasitic parameters of transistors. With phase compensation, both saturation efficiency and bandwidth are significantly improved while maintaining an extended output back-off range. For verification, a 2.05–2.8-GHz symmetrical DPA is designed, fabricated and measured. Under continuous wave excitation, measurement results show that the implemented DPA exhibits drain efficiency of 40%–49% at 9 dB output back-off level and 66%–76% at saturation with a maximum output power of 43.9–44.9-dBm over the entire band.

Experimental investigation of locally available Torai (luffa cylindrica) as evaporative cooling pads

ABSTRACT This work presents an experimental evaluation of the performance of a cooling pad made from the locally available material “Torai” (luffa cylindrica). Different performance parameters that define the cooling performance of the proposed pad, such as the exit air temperature, degree of cooling, saturation effectiveness, cooling potential, and coefficient of performance, have been experimentally investigated. Results show that the overall cooling performance (cooling potential, degree of cooling, effectiveness, and coefficient of performance) increases by increasing the pad thickness. For a given pad an increase in air velocity decreases the saturation efficiency and degree of cooling. The maximum saturation effectiveness and coefficient of performance found for a 7 cm pad at 1.5 m/s air velocity are 65.9% and 8.53, respectively. The rate of water evaporation increases by increasing the pad thickness and air velocity. The maximum water evaporation rate found is 1.4 g/s for a 7 cm pad at 1.5 m/s air velocity. The water retention capacity of the proposed pad material is about 78 g. Moreover, it may be concluded that the proposed pad shows reasonably good performance to be employed as a pad material for direct evaporative coolers. The cost of manufacturing a pad 30.48 cm2 is between Rs130 (US$1.625) and Rs234 (US$2.925).

Clinical Characteristics of Obstructive Sleep Apnea and Comorbid Primary Aldosteronism

To explore the characteristics of patients with obstructive sleep apnea (OSA) and comorbid primary aldosteronism (PA) and to explore the relevant factors affecting plasma aldosterone concentration. A total of 105 patients diagnosed with PA and admitted at West China Hospital, Sichuan University between January 2016 and December 2021 were retrospectively analyzed. The subjects were divided into a PA with comorbid snoring group (n=20) and a PA with comorbid OSA group (n=85) based on the results of polysomnography (PSG). The PA with comorbid OSA group was further divided into mild, moderate, and severe subgroups according to the apnea-hypopnea index (AHI). A total of 85 outpatients diagnosed with OSA were included as the control group. Demographic, clinical, biochemical, and PSG data were compared between the groups. Compared with patients with only OSA, a significantly higher proportion of patients with OSA and comorbid PA had hypertension and elevated levels of systolic and diastolic blood pressure (P<0.05). In addition, patients with OSA and comorbid PA had significantly increased AHI and significantly decreased mean oxygen saturation and sleep efficiency (P<0.05). The more severe the OSA was, the higher levels of BMI, cholesterol, low-density lipoprotein, and uric acid the PA patients had. Linear regression analysis showed that the lowest oxygen saturation (β=－0.222, P=0.045) was negatively correlated with plasma aldosterone concentration. Comorbidity with PA can aggravate the clinical manifestations of OSA, while OSA further disrupted the metabolism of lipids and uric acid in PA patients. Plasma aldosterone concentrations in patients with comorbid OSA and PA were affected by the lowest oxygen saturation level.