Coolant Temperature Research Articles

Homogeneous Equilibrium Modeling for Subcritical Flows in Liquid Rocket Engine Cooling Systems

During off-design operations of liquid rocket engines, the coolant operating conditions can easily extend from the subcritical to the supercritical regime. As a matter of fact, it is very useful to have a single software able to study the flow in this range of operating conditions, providing reliable simulations that are reasonably quick and able to accurately estimate and assess the increase in coolant temperature along the channel and the wall temperature field. This objective is pursued by extending an established approach for the study of supercritical flows to the case of subcritical heating, where a two-phase flow may occur. This is done by exploiting the so-called homogeneous equilibrium model, which has been shown to be sufficiently predictive and accurate for specific applications. With the aim of demonstrating and discussing the potential and limitations of such a single software approach, analyses are conducted on different test cases where two-phase flow is induced by cavitation or flow boiling, and results are compared with those of analytical models and experimental data. It is found that, in addition to some intrinsic limitations in the analysis of subcooled boiling flows, satisfactory agreement with experimental data is obtained in the post-critical-heat-flux regime.

The thermal sensitivity of growth and survival in a wild reptile with temperature‐dependent sex determination

The Charnov‐Bull hypothesis is the leading explanation for the evolution of environmental sex determination (ESD), which includes temperature‐dependent sex determination (TSD), the most common form of ESD. Charnov‐Bull predicts a sex‐by‐incubation temperature interaction for fitness, matching offspring sex with thermal conditions that increase parental fitness. However, there is no general explanation for how the sex‐by‐temperature interaction arises. Two competing explanations for the interaction lie in the survival to maturity hypothesis (SM) and the Trivers–Willard extension (TW). Under SM, the sex that matures later is produced under optimal incubation regimes as the late‐maturing sex accrues more mortality by maturation, while TW suggests that males are always produced under optimal incubation regimes as male mating success is more sensitive to condition (general health, vigor) than female fecundity. In a system where females mature later than males, as in the painted turtle Chrysemys picta, SM and TW generate opposite predictions for the effect of incubation temperature on juvenile survival. We incubated C. picta eggs under either female‐promoting temperatures (28 ± 3 °C) or male‐promoting temperatures (25 ± 3 °C), then released the hatchlings into their natal pond. We used a Bayesian capture–mark–recapture approach to follow their survival over two growing seasons. We found a 2% depression of biweekly survival in individuals incubated under the cooler temperature, providing subtle support for SM. Incubation treatments did not influence growth. Large‐scale field experiments such as this one will be necessary for understanding TSD evolution, and we underline general principles to execute such experiments successfully.

Age dominates flight distance and duration, while body size shapes flight speed in Bombus terrestris L. (Hymenoptera: Apidae).

Flight plays a crucial role in the fitness of insect pollinators, such as bumblebees. Despite their relatively large body size compared with their wings, bumblebees can fly under difficult ambient conditions, such as cooler temperatures. While their body size is often positively linked to their foraging range and flight ability, the influence of age remains less explored. Here, we studied the flight performance (distance, duration and speed) of ageing bumblebee workers using tethered flight mills. Additionally, we measured their intertegular distance and dry mass as proxies for their body size. We found that the flight distance and duration were predominantly influenced by age, challenging assumptions that age does not play a key role in foraging and task allocation. From the age of 7 to 14 days, flight distance and duration increased sixfold and fivefold, respectively. Conversely, the body size primarily impacted the maximum and average flight speed of workers. Our findings indicate that age substantially influences the flight distance and duration in bumblebee workers, affecting foraging performance and potentially altering task allocation strategies. This underscores the importance of considering individual age and physiological changes alongside body size/mass in experiments involving bumblebee workers.

Longer days, larger grays: carryover effects of photoperiod and temperature in gray treefrogs, Hyla versicolor.

Environmental conditions like temperature and photoperiod can strongly shape organisms' growth and development. For many ectotherms with complex life cycles, global change will cause their offspring to experience warmer conditions and earlier-season photoperiods, two variables that can induce conflicting responses. We experimentally manipulated photoperiod and temperature during gray treefrog (Hyla versicolor) larval development to examine effects at metamorphosis and during short (10-day) and long (56-day) periods post-metamorphosis. Both early- and late-season photoperiods (April and August) decreased age and size at metamorphosis relative to the average-season (June) photoperiod, while warmer temperatures decreased age but increased size at metamorphosis. Warmer larval temperatures reduced short-term juvenile growth but had no long-term effect. Conversely, photoperiod had no short-term carryover effect, but juveniles from early- and late-season larval photoperiods had lower long-term growth rates than juveniles from the average-season photoperiod. Similar responses to early- and late-season photoperiods may be due to reduced total daylight compared with average-season photoperiods. However, juveniles from late-season photoperiods selected cooler temperatures than early-season juveniles, suggesting that not all effects of photoperiod were due to total light exposure. Our results indicate that despite both temperature and photoperiod affecting metamorphosis, the long-term effects of photoperiod may be much stronger than those of temperature.

RESEARCH ON THE EFFICIENCY OF CATALYTIC CONVERSION OF EXHAUST GASES FROM A CAR ENGINE DURING WARM-UP MODE

The article is dedicated to researching the efficiency of catalytic conversion of exhaust gases from VW BBY car engine (4FS 7.65/7.56) during warm-up mode. The objective of the study is to determine the impact of structural and operational factors of emission control systems on their efficiency during the warm-up phases of car engines. A compre-hensive research methodology has been developed, which includes experimental investigations of the engine and catalyt-ic converter warm-up processes and their influence on harmful emissions. It has been established that during engine warm-up at idle, the attainment of chemical and thermal conditions necessary for the effective operation of the exhaust gas neutralization system occurs at different times: chemical conditions are reached earlier, while thermal conditions are reached later. The nominal efficiency of neutralizing various harmful exhaust gas components (CO, HC, NO) is achieved at different times and temperatures of the catalytic converter: for NO in 180 seconds at 295 °C; for CO in 220 seconds at 305 °C; and for HC in 400 seconds at 330 °C. The necessary chemical operating conditions are reached in 100 seconds at 230 °C. Furthermore, the attainment of the system’s nominal neutralization efficiency is almost independent of the time taken for the engine to reach its operational temperature based on the coolant temperature. The primary catalytic converter has little impact on emission levels in this mode due to not reaching its operational temperature. The results of the experimental research provide an opportunity to refine the theoretical model for determining the influence of structural and operational factors of emission control systems on harmful emissions and to establish a combination of factors for reducing emissions. Keywords: car engine, operating mode, fuel consumption, catalytic converter temperature, concentrations of harmful substances, exhaust gases.

Impact of Nanoparticles in Water Coolant on Heat Transfer Rate in Parallel and Counter Flow Heat Exchanger

A heat exchanger is a device used to transfer heat between two or more fluids. The fluids can be single or two phases depending on the exchanger type and may be separated by in -direct contact (the two most common kinds of heat exchanger are the shell-and-tube and plate/fin). In this research work double pipe heat exchanger was used to analyze the performance of water coolant for industrial applications. In Heat Exchanger the water coolant temperature increases due to increase in the temperature of oil in the tubes. Therefore, it may decrease the overall efficiency of the equipment resulting from degradation of the lubricant oil. In this regard, it is required some additives to be mixed with water coolant so that to enhance the heat transfer rate of the unit. Due to the excessive heating of the hydraulic oil in the turbine bearings, the material of the bearing found damage and deteriorate. Therefore, the aim of this study was to remove the heat from bearing oil, so that overall efficiency of heating equipment could be increased. In this research work Hydraulic oil was heated at 600C and 700C as per requirements of the industry. The experiments were conducted at both parallel and counter flow directions. Initially, a baseline experiment was carried out between hot oil and water coolant (without additives or nanoparticles). Besides the heat transfer rate between hot oil and water coolant with the additives (CuO and Al2O3) were observed at 1-3% proportion. It was concluded that the heat transfer rate of CuO was increased more than Al2O3 and plain water coolant due to more uniform temperature difference maintained between the inlet and outlet of cold and hot fluids due to the higher thermal conductivity of CuO. The maximum heat transfer rate was found to be 36.6 % at 60℃ and 38% at 70℃ with 3% of CuO additive in water coolant in the counter-flow condition.

MASS-WASTING INDUCED SHIFTS OF THE BASE OF THE GAS HYDRATE STABILITY ZONE: EXAMPLES FROM THE OFFSHORE NIGER DELTA BASIN, NIGERIA

Mass-wasting episodes lead to significant changes in the pressure and temperature regimes within shallow marine sediments and induce variations in the thickness of the gas hydrate stability zone. These variations are marked by vertical migrations of bottom-simulating reflections that typically mark the base of the hydrate zone. Using exploration seismic data from the Offshore Niger Delta, this study presents two examples involving the vertical migration of the base of the gas hydrate stability zones induced by mass-wasting events. The first is related to a slope failure surface along the forelimb of an active thrust-cored anticline with considerable bathymetric relief. Sediment removal has induced both a decrease in overburden pressure and an incursion of cooler temperature flux in strata in the anticline and led to a migration of the base of the gas hydrate stability zone to deeper levels. The second case is related to a recent erosional event that has led to sediment removal along a seafloor channel course. Evidence of ongoing migration of the base of the gas hydrate stability zone to deeper levels is provided by the lateral termination of a BSR along channel wall, its absence beneath the channel bottom and its apparent downward bend close to the channel fringes. Apart from unroofing hydrate systems and releasing free gas into the ocean and possibly the atmosphere, mass-wasting events on the seafloor, represent significant drivers influencing the formation of gas hydrates in shallow subsea sediments and the thickness and depths of the gas hydrate stability zone.

Experimental analysis and investigation of desiccant coated heat exchanger applications involving condensation and sorption mechanisms

This study focuses on the application of desiccant coated heat exchangers (DCHEs) in conditions where condensation occurs below the dew point temperature. Previous experimental studies on DCHEs and DCHPs have predominantly examined the sorption mechanism above the dew point, leaving a gap regarding material selection and system design in the presence of condensation. To address this, a guide is introduced that combines the understanding of condensation and sorption processes for desiccant applications. The guide is applied to evaluate the suitability of a superabsorbent-LiCl (SAP-LiCl) composite desiccant for desiccant coated heat pump (DCHP) applications. The stability of the desiccant in the presence of condensed water droplets is validated. Additionally, an experimental investigation explores the relationship between sorption and condensation mechanisms, identifying the transitional coolant temperature at which dehumidification shifts from condensation-dominant to sorption-dominant. By incrementally adjusting the coolant temperature in 5 °C steps, the transitional temperature of the SAP-LiCl based DCHE is determined to be approximately 15 °C under the target operation scenario, rendering its suitability for additional below-dew-point applications. The study reveals optimal operational parameters for DCHE, demonstrating a potential energy saving of 20 %. Based on these findings, a DCHP prototype is constructed to assess the feasibility of DCHE in real-world applications. The transient behaviors of this prototype are analyzed during each operating cycle, yielding a coefficient of performance of 4.97 and a cooling capacity of 1.5 kW under baseline operating conditions.

Machine learning assisted multi-objective design optimization for battery thermal management system

The rapid expansion of the electric vehicle (EV) industry necessitates the development of advanced battery thermal management systems (BTMSs) to safeguard the cyclic properties and security of lithium-ion batteries. However, the assessment of the performance of BTMS often overlooks the importance of considering not only the thermal regulation effectiveness on batteries but also its own energy efficiency. This study investigated the synergistic effects of BTMS design and control strategies on both thermal performance and energy utilization of its own. A multiphysics-based model was developed, featuring an 18,650 Lithium-ion battery module with curved cooling channels, to systematically evaluate the impact of cooling channel width and warping angle, inlet coolant temperature and velocity, and charging rate on system performance and efficiency. To further expedite the design optimization process, a Gaussian process (GP)-based surrogate model was implemented. An uncertainty quantification analysis was subsequently performed to validate the robustness of the optimized designs against stochastic variations. The findings indicate that the channel width and coolant velocity play a pivotal role in enhancing BTMS efficiency. Through a rigorous multi-objective optimization process, the energy efficiency was improved by 126 %, while maintaining battery temperatures below 28.4 °C and coolant pressure drops under 3.6 kPa. The integration of multiphysics simulation and machine learning assisted optimization technique represents a pioneering step forward in the development of sophisticated and efficient BTMS solutions for future electric vehicles.

Mathematical model and numerical calculation of the movement of oil products in helicoidal heat exchangers

Heating of oil and oil products is widely used to reduce energy losses during transportation. An approach is developed to determine the effective length of the heat exchanger and the temperature of the cold coolant (oil) at its outlet in the case of a strong dependence of oil viscosity on temperature. The method of the log-mean temperature difference, modified for the case of variable viscosity, and the methods of computational fluid dynamics (CFD) are used for calculations. The results of numerical calculations are compared with the data obtained on the basis of a theoretical approach at a constant viscosity. When using a theoretical approach with a constant or variable viscosity, the heat transfer coefficients to cold and hot coolants are found using criterion dependencies. The Reynolds-averaged Navier-Stokes (RANS) and a turbulence model that takes into account the laminar-turbulent transition are applied. In the case of variable oil viscosity, a transition from the laminar flow regime to the turbulent one is manifested, which has a significant effect on the effective length of the heat exchanger. The obtained results of CFD calculations are of interest for the design of heat exchangers of a new type, for example, helicoidal ones.

Hot and fast: seed ecology for restoration relevant species in the Argyle region of the east Kimberley, Australia

This study investigates the germination requirements of 12 plant species native to the Argyle region of the east Kimberley, a biodiverse monsoonal tropical region characterized by high temperatures, high evaporation, and episodic seasonal rainfall. The research involved quality assessment of mature seeds, followed by dormancy alleviation and laboratory‐based germination to determine the responses of seeds to a range of temperatures (5–40°C) in terms of germination speed (T10), mean germination time, and maximum germination proportion. Data were then modeled to calculate the optimal temperature to support germination for each species. The results showed that germination rapidly commences in response to a wide range of temperatures typical of the wet season (November–February) in the east Kimberley, though germination for most species was still high (>50%) after exposure to temperatures as low as 15°C. Mean optimal temperature for germination across all species was 25.8 ± 1.5°C, with minimal variation between most species, the exception being Dodonaea physocarpa, which preferred cooler temperatures (Topt = 14.0°C). The speed of germination was also rapid (T10 = 1–3 days) across all species at the optimal germination temperature. The findings suggest that temperature is not a limiting factor for germination in this region and that the onset and intensity of the wet season are the most significant factors determining successful germination, emergence, and seedling establishment. The study underscores the importance of species‐specific understanding of environmental temperatures required for seed germination in seed‐based restoration efforts and informs the planning of direct seeding works, thus enhancing restoration outcomes.

Research on fuzzy adaptive GPC of average coolant temperature based on regulation of boric acid concentration

In order to keep the balance of power distribution in the core of a nuclear reactor, the method of adjusting the boric acid concentration to regulate the average temperature of the coolant has been adopted to track the demands of power changes in the core. However, the chemical reaction process of regulating the average coolant temperature by adjusting the boric acid concentration is too slow to better meet the demands of power changes. In view of this challenge, this paper proposes an innovative fuzzy adaptive incremental generalized predictive control strategy to optimize the process of regulating the coolant temperature. This strategy employs a dynamic adjustment of control parameters, specifically through the application of incremental factors γ, which is calibrated using a fuzzy logic-based algorithm to enhance system responsiveness and robustness in real-time. The strategy aims to improve the efficiency and responsiveness of the nuclear reactor control mechanism and further enhance the safety and stability of nuclear power generation.Firstly, the system state space equations are established based on the boric acid concentration equation and the nuclear reactor kinetics. Secondly, the step factors β and incremental factors γ are used in improved-GPC to improve control real-time and robustness. The step factor β speeds up the rolling optimization, and the incremental factor γ is adjusted based on the fuzzy algorithm according to the online recognition degree of the system. Finally, the 1000 MW Pressurized Water Reactor is modeled and simulated. The results show that improved-GPC has a shorter regulation time and a stronger ability to cope with the model mismatch in this system than other controllers.

Machine Learning Based Fault Classification in Pilot Plant Batch Reactor: Using Support Vector Machine.

Identifying and diagnosing faults is a critical task in process industries to maintain effective monitoring of process and plant safety. Minimizing process downtime is critical for enhancing the quality of the product and minimizing production costs. Real-time categorization of issues across several levels is essential for the monitoring of processes. However, there are still notable obstacles, that must be addressed, such as the existence of robust correlations, the complexity of the data, and the lack of linearity. This study introduces a novel fault identification technique in batch reactor experimental trials that employs multikernel support vector machines (SVMs) to categorize internal and external issues, specifically reactor temperature, coolant temperature, and jacket temperature. The data set was obtained from empirical research. The classification has been conducted using a multikernel SVM. This article identified that the nonlinear classifier using the radial bias function results in an accuracy that is at least 22.08% superior to other methods.

Soil organic carbon sequestration under Araucaria angustifolia plantations but not under exotic tree species on a mountain range

ABSTRACT Plantation forests can be efficient C sinks in biomass and soil organic carbon (SOC), but the latter depends on many factors, including climate. Tropical humid, mountain areas have cooler temperatures, slowing microbial decomposition, and thus can store considerable SOC. However, the effects of forest plantations on SOC of these montane areas are still poorly studied. Here, we aimed to assess changes in SOC, and related soil properties, after conversion of native rainforest to plantations of five tree species, with rotation cycles varying from 7 to 30 years, on the Mantiqueira Range, Minas Gerais, Brazil. We measured SOC contents and stocks (0.00-0.40 m layer) under a native montane rainforest (control) and plantations of Eucalyptus, Pinus, Cunninghamia, Cupressus and Araucaria, all planted in 3 × 3 m spacing, at an altitude of ca. 1,300 m, marked by humid and cool climate, where SOC contents are naturally high. Soil organic carbon varied from 55 g kg -1 under Eucalyptus to 105 g kg -1 under Araucaria (0.00-0.05 m layer), decreasing in depth (0.20-0.40 m) to the still high values of 20-40 g kg -1 . Soil organic carbon stocks for the top 0.20 m were also high, reaching ca. 140 Mg ha -1 under Araucaria, significantly higher value than the native forest (ca. 90 Mg ha -1 , p<0.05), which did not differ from the other species. Soil organic carbon stocks were not affected in the 0.20-0.40 m soil layer, whereas soil structure patterns changed under some species, without however resulting in bulk density changes, and pH decreased under Araucaria. Such data showed large SOC stocks under montane native forests can not only be preserved upon conversion to forest plantations, but considerable SOC sequestration can be achieved in 30-years rotation cycles plantations of indigenous Araucaria angustifolia, marked by more open canopies and greater understory biomass.

A topology optimization-based-novel design and comprehensive thermal analysis of a cylindrical battery liquid cooling plate

In previous studies, the designs of the liquid cooling channel for battery packs usually paid emphasis on optimizing the predefined cooling channels. This significantly restricts the possibilities for geometric modifications of cooling channels, consequently placing limitations on the potential improvement in heat dissipation performance. To address these limitations, this study proposes a Topology optimization-based-novel design and comprehensive thermal analysis of a cylindrical battery liquid cooling plate. The aim of using topology optimization is to overcome these constraints, enabling more flexible and global domain designs. Three different inlet–outlet configurations of the cooling plate structure were designed using a dual-objective optimization function. A comprehensive numerical analysis was conducted and the topology-optimized liquid cooling plate system was compared with two other cooling pipe liquid cooling systems. The effects of coolant flow rate, battery discharge rate, and cooling plate thickness and quantity on the heat dissipation performance of the liquid cooling system were investigated. Findings demonstrate that the topology-optimized cold plate system with four inlets and two outlets exhibits optimal heat dissipation performance. Increases in coolant flow rate, cold plate thickness, and quantity contribute to enhanced cooling performance of the liquid cooling system. Taking into account factors such as pump power consumption, system weight, and heat dissipation performance, a liquid-cooled system with three cold plates and an inlet flow rate of 2.5 × 10-6 m3/s is considered the optimal choice for cooling the battery pack in this study. Under the cooling of this cold plate system, at a coolant and ambient temperature of 25 °C and a discharge rate of 3C, the battery pack’s maximum temperature and temperature difference are 30.9 °C and 4.87 °C, respectively.

The Decline in Summer Fallow in the Northern Great Plains Cooled Near‐Surface Climate but had Minimal Impacts on Precipitation

AbstractLand management can moderate or intensify the impacts of a warming atmosphere. Since the early 1980s, nearly 116,000 km2 of cropland that was once held in fallow during the summer is now planted in the northern North American Great Plains. To simulate the impacts of this substantial land cover change on regional climate processes, convection‐permitting model experiments using the Weather Research and Forecasting model were performed to simulate modern and historical amounts of summer fallow. The control simulation was extensively validated using multiple observational data products as well as eddy covariance tower observations. Results of these simulations show that the transition from summer fallow to modern land cover led to ∼1.5°C cooler temperatures and decreased vapor pressure deficit by ∼0.15 kPa during the growing season across the study region, which is consistent with observed cooling trends. The cooler and wetter land surface with vegetation led to a shallower planetary boundary layer and lower lifted condensation level, creating conditions more conducive to convective cloud formation and precipitation. Our model simulations however show little widespread evidence of land surface changes effects on precipitation. The observed precipitation increase in this region is more likely related to increased moisture transport by way of the Great Plains Low Level Jet as revealed by the ERA5 reanalysis. Our results demonstrate that land cover change is consistent with observed regional cooling in the northern North American Great Plains but changes in precipitation cannot be explained by land management alone.

A novel battery thermal management based on composite phase change material with liquid-assisted cooling for different ambient temperatures

In this work, a thermal management system (TMS) employing the combination of composite phase change material (CPCM) and liquid cooling was developed for a lithium battery module. To enhance the temperature uniformity of the battery module, a new strategy was proposed creatively, which varied the thermal conductivity of the CPCM wrapping the battery depending on the position of the battery. Firstly, the thermal conductivity of CPCM was optimized for a single battery thermal management. Then, the temperature control effects of the proposed TMS were investigated numerically on the battery module. Results indicate the thermal conductivity of CPCM should not be more than 3 W/m·K. At 40 °C of ambient temperature, the only CPCM cooling can maintain the surface temperature of battery with 5C discharging within 44 °C, presenting excellent uniformity. At 45 °C, CPCM fails and liquid cooling can inhibit the temperature rise of the batteries, but increases the temperature inconsistency. Compared to the CPCM with constant thermal conductivity (3 W/m·K), the surface temperature difference of the battery module decreases from 5.30 to 2.95 °C employing CPCM with varying thermal conductivity (0.6–3 W/m·K). Decreasing coolant temperature can reduce the battery module temperature, but increase its temperature difference. The effectiveness of the varying λCPCM on the temperature uniformity of a battery module has also been verified by the designed experiment. This study can potentially provide significant guidance to the design of a lithium battery module based on the coupling CPCM and liquid cooling.

Coupled modeling of thermal-fluid-solid and chemo-mechanical behaviors in thermal barrier coatings under flowing gas environment

This study proposes a modeling approach to simulate the thermo-chemo-mechanical responses of thermal barrier coatings (TBCs) exposed to flowing high-temperature gas. A thermal-fluid-solid analysis was performed to simulate temperature fields of the coatings under flowing gas environment, while finite element analysis was carried out to study the oxidation and stress evolutions of the coatings using a developed chemo-mechanical constitutive model. Thermal loads from thermal-fluid-solid analysis were imposed on the finite element model, by which the factors associated with flowing gas were incorporated into the thermo-chemo-mechanical modeling. The study systematically investigated the effects of flowing gas and coolant on the chemo-mechanical responses of the coatings. The results revealed that the enhanced gas factors (temperature, velocity, angle of attack, and pressure) and coolant temperatures accelerate oxidation and induce higher residual stresses, while higher coolant velocity mitigates both oxidation and stresses. The volume fraction of oxygen in the gas was found to have a negligible influence. Dimensional analysis and multiple regression were performed to derive mathematical expressions for assessing out-of-plane stress and oxidation dynamics. Design maps were proposed to guide the durable design of the coatings.

Temperature-dependent exercise recovery is not associated with behavioral thermoregulation in a salmonid fish

The relationship between behavioral thermoregulation and physiological recovery following exhaustive exercise is not well understood. Behavioral thermoregulation could be beneficial for exercise recovery; for example, selection of cooler temperatures could reduce maintenance metabolic cost to preserve aerobic scope for recovery cost, or selection of warmer temperatures could accelerate recovery of exercise metabolites. While post-exercise behavioral thermoregulation has been observed in lizards and frogs, little is known about its importance in fish. We examined the influence of post-exercise recovery temperature on metabolic rate, thermal preference, and metabolite concentrations in juvenile brook char (Salvelinus fontinalis). Fish were acclimated to and exercised at 15 °C, then recovered at either 15 °C or 10 °C while their metabolic rate was measured via respirometry. Metabolite concentrations were measured in fish after exercise at 15 °C and recovery under one of three thermal treatments (to simulate various behavioral thermoregulation scenarios): (i) 6 h recovery at 15 °C, (ii) 6 h recovery at 10 °C, or (iii) 3 h recovery at 10 °C followed by 3 h recovery at 15 °C. Thermal preference was quantified using a static temperature preference system (15 °C vs. 10 °C). Metabolic rates returned to resting faster at 10 °C compared with 15 °C, although at 10 °C there was a tradeoff of delayed metabolite recovery. Specifically, post-exercise plasma osmolality, plasma lactate, and muscle lactate remained elevated for the entire period in fish recovering at 10 °C, whereas these parameters returned to resting levels by 6 h in fish from the other two recovery groups. Regardless, fish did not exhibit clear behavioral thermoregulation (i.e., fish overall did not consistently prefer one temperature) to prioritize either physiological recovery process. The advantage of metabolic rate recovery at cooler temperatures may balance against the advantage of metabolite recovery at warmer temperatures, lessening the usefulness of behavioral thermoregulation as a post-exercise recovery strategy in fish.

Inorganic Nitrogen Gas‐Aerosol Partitioning in and Around Animal Feeding Operations in Northeastern Colorado in Late Summer 2021

AbstractAmmonia (NH3) from animal feeding operations (AFOs) is an important source of reactive nitrogen in the US, but despite its ramifications for air quality and ecosystem health, its near‐source evolution remains understudied. To this end, Phase I of the Transport and Transformation of Ammonia (TRANS2Am) field campaign was conducted in the northeastern Colorado Front Range in summer 2021 and characterized atmospheric composition downwind of AFOs during 10 research flights. Airborne measurements of NH3, nitric acid (HNO3), and a suite of water‐soluble aerosol species collected onboard the University of Wyoming King Air research aircraft present an opportunity to investigate the sensitivity of particulate matter (PM) formation to AFO emissions. We couple the observations with thermodynamic modeling to predict the seasonality of ammonium nitrate (NH4NO3) formation. We find that during TRANS2Am northeastern Colorado is consistently in the NH3‐rich and HNO3‐limited NH4NO3 formation regime. Further investigation using the Extended Aerosol Inorganics Model reveals that summertime temperatures (mean: 23°C) of northeastern Colorado, especially near the surface, inhibit NH4NO3 formation despite high NH3 concentrations (max: ≤114 ppbv). Finally, we model spring/autumn and winter conditions to explore the seasonality of NH4NO3 formation and find that cooler temperatures could support substantially more NH4NO3 formation. Whereas NH4NO3 only exceeds 1 μg m−3 ∼10% of the time in summer, modeled NH4NO3 would exceed 1 μg m−3 61% (88%) of the time in spring/autumn (winter), with a 10°C (20°C) temperature decrease relative to the campaign.