Total Heat Production Research Articles

380 Diet protein concentration does not influence dietary net energy by group housed growing pigs offered ad libitum access to feed

Abstract The objective was to test the hypothesis that net energy (NE) of diets is not increased by reducing soybean meal (SBM) and increasing crystalline amino acids (CAA) in diets fed to group-housed pigs on an ad libitum basis. Two “normal protein” diets with 17 and 14% crude protein (CP) were formulated. One diet was based on corn, SBM, and no CAA and the other diet was based on corn, SBM, and crystalline Lys, Met, and Thr. Four additional diets containing 13, 12, 11, or 10% CP were formulated by reducing SBM and increasing crystalline Lys, Met, Thr, Trp, Val, and Phe. Growing pigs (n = 24; initial body weight = 29.9 ± 2.4 kg) were randomly allocated to 6 calorimeter chambers with 4 pigs per chamber. The 6 chambers were allotted to the six diets using a 6 × 6 Latin square design with six 15-d periods providing 6 replicate chambers per diet. Pigs had ad libitum access to diets throughout the experiment except during the fasting periods. Consumption of O2 and production of CO2 and CH4 were measured, and fecal and urine samples were collected for 6 d after 7 d of adaptation. Fasting heat production (FHP) was determined for 12 h following a 24 h fasting period. Diets, fecal samples, and lyophilized urine samples were analyzed for gross energy (GE) and N. Data were analyzed using contrasts statements to determine linear and quadratic effects of reducing dietary protein. Results indicated that feed intake, fecal and urine GE output, the apparent total tract digestibility (ATTD) of dry matter and GE, total heat production (THP), FHP, and retained energy were not different between pigs fed the 17 and the 14% CP diets (Table 1). The respiratory quotient (RQ) of pigs fed the 17% CP diet was less (P = 0.045) compared with the 14% CP diet. Digestible energy (DE) and metabolizable energy (ME) in the 17% CP diet were greater (P < 0.05) than in the 14% CP diet, but NE was not different between these 2 diets. Feed intake, GE intake, and fecal GE output of pigs were linearly (P = 0.044) increased by reducing CP in diets, but reducing diet CP did not affect ATTD of dry matter or GE or urine GE excretion. Total heat production, FHP, retained energy, and DE, ME, and NE were also not affected by reducing CP in diets. In conclusion, reducing CP of diets for pigs by reducing SBM and increasing CAA did not increase NE of the diet when fed to group-housed pigs on an ad libitum basis, and dietary CP does not appear to influence diet NE.

Incremental supply of fat, lactose, or protein influences the diurnal pattern of heat production and substrate oxidation in preweaning calves

Increasing nutrient supply to dairy calves has well known benefits; however, the effects of milk replacer (MR) composition when supplied in higher amounts are not fully understood, particularly in the first weeks of life. To better understand the metabolism of macronutrient supply in young calves (21 d old), we investigated diurnal patterns of heat production and substrate oxidation in young calves fed MR with an incremental supply of fat, lactose, or protein. Thirty-two groups of 3 mixed-sex Holstein-Friesian newborn calves (3.4 ± 1.6 d of age), were randomly assigned to one of 4 dietary treatments and studied for 21 d. Diets consisted of a basal MR (23.3% CP, 21.2% EE, and 48.8% lactose of DM) fed at 550 kJ/kg BW0.85 per day (CON; n = 24), or the basal MR incrementally supplied with 126 kJ of digestible energy/BW0.85 per day as milk fat (+FAT; n = 23), lactose (+LAC; n = 24), or milk protein (+PRO; n = 23). Calves were fed MR in 2 daily meals and had ad libitum access to water, but were not supplied with any calf starter nor forage. After 2 weeks of adaptation to the diets, groups of 3 calves were placed for 1 wk in an open-circuit respiration chamber for nitrogen and energy balance measurements (lasting 7 d). On d 3, glucose oxidation kinetics was estimated by using [U-13C]glucose. Measurements included total heat production (total energy [HP], activity [Hact] expenditure, resting metabolic rate [RMR]), respiration quotient (RQ), carbohydrate (COX) and fat oxidation (FOX) in 10 min. intervals and averaging these values per hour over days. Incremental supply of lactose and fat increased body fat deposition, with observed patterns in RMR indicating that this increase occurred primarily after the meals. Specifically, the average daily RMR was highest in the +PRO group and lowest in the CON treatment. The HP was higher in the +PRO group and throughout the day, hourly means of HP were higher in this treatment mainly caused by an increase in Hact. The recovery of 13CO2 from oral pulse-dosed [U-13C]glucose was high (77%), and not significantly different between treatments, indicating that ingested lactose was oxidized to a similar extent across treatments. Increasing lactose supply in young calves increased fat retention by reduction in fatty oxidation. Calves fed a MR with additional protein or fat raised RMR persistently throughout the day, whereas the extra lactose supply only affects RMR after the meal. Dietary glucose was almost completely oxidized (77% based on (13C) glucose measurement) regardless of nutrient supplementation. Extra protein supply increased HP and FOX compared with similar intakes of fat and lactose. Fasting heat production (FHP) of young, group-housed calves is comparable to literature values and unaffected by energy intake. Overall, these findings deepen our understanding of how different nutrients affect metabolic processes, fat retention, and energy expenditure in young dairy calves.

Continuous monitoring using thermography can capture the heat oscillations maintaining body temperature in neonates

The body temperature of infants at equilibrium with their surroundings is balanced between heat production from metabolism and the transfer of heat to the environment. Total heat production is related to body size, which is closely related to metabolic rate and oxygen consumption. Body temperature control is a crucial aspect of neonatal medicine but we have often struggled with temperature measures. Contactless infrared thermography (IRT) is useful for vulnerable neonates and may be able to assess their spontaneous thermal metabolism. The present study focused on heat oscillations and their cause. IRT was used to measure the skin temperature every 15 s of neonates in an incubator. We analyzed the thermal data of 27 neonates (32 measurements), calculated the average temperature within specified regions, and extracted two frequency components—Components A and B—using the Savitzky–Golay method. Furthermore, we derived an equation describing the cycle—named cycle T—for maintaining body temperature according to body weight. A positive correlation was observed between cycle T and Component B (median [IQR]: 368 [300–506] s). This study sheds light on the physiological thermoregulatory function of newborns and will lead to improved temperature management methods for newborns, particularly premature, low-birth-weight infants.

The efficiency of dodecafluoro-2-methylpentan-3-one in suppressing NCM 811 lithium-ion battery fire

With the increase in the specific energy of lithium-ion batteries (LIBs), fire accidents occur more frequently; however, the effective and clean suppression of LIB fires remains a challenge. In the present work, the efficiency of dodecafluoro-2-methylpentan-3-one (C6F12O) in suppressing high energy density (HED) ternary LIB fires is experimentally investigated. It is found that C6F12O can efficiently extinguish the HED battery and its module fire. As the flow rate increases, the extinguishment time decreases and the peak temperature decreases, but the cooling efficiency for the long-term process is reduced. When the C6F12O spray can completely cover the thermal runaway (TR) area, its extinguishing and cooling effect is the best. For the HED module, the application of C6F12O effectively increases the TR trigger temperature, reduces the TR peak temperature, and decreases heat production. The application of water mist enhances the cooling of extinguished LIBs, the combination of C6F12O and water mist extends the TR propagation time of the fully charged LIB module to 1.4 times that without suppression, and the total TR heat production is reduced by 1423.1 kJ. These results provide guidance for the design of inhibitor volume fractions for HED LIB fires.

Body temperature and locomotor activity of social subterranean mole voles (Ellobius talpinus) in winter

To find out whether a social subterranean rodent—the northern mole vole (Ellobius talpinus)—hibernates in winter, nine individuals from Southern Siberia were captured in late autumn and implanted with loggers [that constantly recorded body temperature (Tb) and locomotor activity] and then released. Eight of them were recaptured the following spring. From October to April, the animals’ Tb never dropped below 33 °C, although cosinor analysis revealed a decrease in mesor values and in the amplitude of daily fluctuations of Tb and activity in winter months. Spectral density of circadian rhythms of both indexes also diminished in winter. The magnitude of Tb and fluctuations of activity differed between the two studied familial groups, probably due to their unequal numbers of individuals, which could affect the total heat production. The levels and patterns of temperature and activity fluctuations observed in winter rule out the possibility of hibernation in this species.

Investigation of flame structure and emission production: Combustion modeling of co-flow interaction with spray

Using a validated computational approach, the present study examines the flame structure and emission production by spray combustion in an unconfined, swirl-free lab burner. Some species, such as acetylene, a precursor to the formation of polycyclic aromatic hydrocarbons, are generated within the fuel-rich region. A smaller area of the enclosed region reduces the mass concentration of emissive species. This can be accomplished by modifying the operating conditions, such as the spray characteristics, macro-flow velocity, and nozzle geometry. Increasing the co-flow velocity has a significant effect on transforming the flame structure from a single-reaction regime to a double-structure regime. The fuel-rich area shrinks as the co-flow velocity increases, resulting in a decrease in emissive species but a fall in total heat generation. In terms of air passage design, it appears that altering the air passage area has a noticeable impact on the flame structure, where a reaction zone can be established within the flame core. Depending on the equivalence ratio, the total heat generation and output emissions can be modified through the burner air passage improvement, resulting in a 90% decrease in the production of emissive species and an 18% increase in total heat production.

Eco-friendly diet: nutrient digestibility, nitrogen and energy balances and growth performance of growing pigs.

The traditional approach to formulating pig diets is based only on minimizing cost while meeting nutritional requirements and thus does not consider the environmental impacts associated with producing feed ingredients. To reduce the overall environmental impact of pork production, feed ingredients can be considered to formulate environmentally friendly diets. However, their potential effects on pig performance could decrease environmental benefits at the farm gate. The objective of this study was to quantify the effects of such eco-friendly pig diets on nitrogen (N) and energy (E) balances, the components of heat production (HP), and the performance of growing pigs. Digestibility coefficients of dry matter (84.5% vs. 88.2%, P < 0.01) and N (80.4% vs. 86.3%, P < 0.01) were significantly lower for the eco-friendly diet than the Control-diet (a commercial diet used in France). N excretion in feces was significantly higher for the group of pigs fed the eco-friendly diet than for the group fed the Control-diet (9.8 vs. 6.9g/d, respectively, P = 0.01), while the N retention tended to be lower (27.8 vs. 30.3g/d, respectively; P = 0.06). The metabolizable E:digestible E ratio did not differ between diets, but total HP was significantly lower for the eco-friendly diet group than for the Control-diet group (1,340 vs. 1,388 kJ/kg body weight0.60/d, respectively, P = 0.03). Using feed ingredients with lower environmental impacts, such as locally produced protein or co-products from wheat processing, is an effective way to decrease the environmental impacts of pig production. However, the nutritional composition of these eco-friendly ingredients could be overestimated, in particular the true digestibility of amino acids. This indicates the need to better estimate and consider the true digestibility of eco-friendly diets to decrease environmental impacts of livestock production without decreasing animal performance.

Energy efficiency of grazing Hereford heifers classified by paternal residual feed intake

Abstract Residual feed intake (RFI) has become a widely spread index of feed efficiency. Although most of beef cattle systems in the world are pasture based, RFI evaluation and research is usually performed in confinement conditions. In this context, residual heat production (RHP) estimated as the difference between actual and expected heat production (HP), could allow to identify efficient animals. Thus, the aim of this work was to evaluate the relationship between paternal estimated breeding values (EBV) for RFI and beef heifer efficiency, measured as RHP, as well as its association with heifers’ productive and reproductive performance on grazing conditions. Seventy-one 25 ± 0.8-mo-old and seventy-four 24 ± 0.7-mo-old Hereford heifers were managed as contemporary groups in spring 2019 and 2020, respectively. Heifers were sired by 10 RFI-evaluated bulls and classified into three groups according to the paternal EBV for RFI: five bulls of low RFI (high efficiency, pHE), two bulls of medium RFI (medium efficiency), and three bulls of high RFI (low efficiency, pLE). The experimental period lasted 70 d prior to their first insemination where HP was determined by the heart rate-O2 pulse technique. In addition, reproductive performances during the first and second breeding and calving seasons were recorded. Heifers’ RHPs expressed as MJ/d and kJ/kg of body weight (BW)0.75/d were positively correlated with paternal RFI EBVs (P &amp;lt; 0.05; r &amp;gt; 0.60). Moreover, BW and average daily gain (ADG) were greater (P &amp;lt; 0.01) for pHE than pLE heifers while expressed as units of BW0.75/d, neither total HP nor metabolizable energy (ME) intake differed between groups, but pHE heifers had greater retained energy (RE; P &amp;lt; 0.01) and lower RHP (P &amp;lt; 0.05) than pLE ones. Gross energy efficiency (RE/ME intake) was greater (P &amp;lt; 0.001) for pHE than pLE heifers while the HP/ADG and RHP/ADG were reduced (P &amp;lt; 0.05) and feed-to-gain ratio (ADG/DM intake) tended to be greater (P = 0.07) for pHE than pLE heifers. In addition, during the first breeding and calving seasons, small but significant (P &amp;lt; 0.01) differences in reproductive responses between groups suggested an earlier pregnancy in pHE heifers than the pLE group, differences that disappeared during the second breeding and calving seasons. Thus, heifers sired by high-efficiency bulls measured as RFI were more efficient measured as RHP in grazing conditions, without significant differences in reproductive performance.

Experimental and numerical modeling of the heat generation characteristics of lithium iron phosphate battery under nail penetration

This study conducted nail penetration tests on 20 Ah prismatic LiFePO4 batteries and simulated the slow release of Joule heat and side reaction heat by combining a new thermal model with a parameter optimization method. The results indicate that the 50% and 80% SOC LiFePO4 batteries only release Joule heat under penetration, while the side reaction heat is acquired under 100% SOC besides Joule heat. Moreover, approximately 56.4% of the stored electrical energy is converted into Joule heat, which accounts for the majority of the total heat production of 100% SOC LiFePO4 battery under penetration, while side reaction heat accounts for only 6.4%. Furthermore, the exothermic side reactions of 100% SOC LiFePO4 battery under penetration can be effectively suppressed when the electrical energy release ratio is less than 0.52, or the convection coefficient between the battery and its surroundings exceeds 12 W/m2K. This numerical study expands the analysis of the heat generation characteristics of LiFePO4 batteries during penetration and provides practical guidance for system safety design.

Investigation of the thermal performance and heat transfer characteristics of the lithium-ion battery module based on an oil-immersed cooling structure

Based on the concept of direct contact liquid cooling, a compact oil-immersed battery thermal management system is designed in this work. In the experiment, methyl silicone oil, white oil, and transformer oil are used as coolants to study the cooling effect and the heat transfer characteristics of the system. It is found that three oils show good cooling effects and temperature uniformity in general at three discharge rates. The maximum average temperatures of the battery module immersed in silicon oil, white oil, and transformer oil reach 53 °C, 47.3 °C, and 45.6 °C, respectively, under the maximum discharge condition (2 C). It decreases by about 25 %, 33 %, and 35 % compared with the maximum temperature of the battery module under natural convection cooling (70.5 °C). In addition, the theoretical analysis verifies that the battery heat production and the ratio of heat absorbed by three oils to the total heat production increases with the discharge rate. At the end of 2 C discharge, the ratio of heat absorbed by silicone oil, white oil, and transformer oil to the total heat production reaches 38.9 %, 46.3 %, and 49.5 %, respectively. Theoretical calculations show that all three oils can effectively absorb the heat generated by the battery, and especially transformer oil can achieve an excellent cooling effect. The results further confirm the effectiveness of the oil-immersed battery thermal management system, which provides additional new insights for the future development of battery thermal management systems based on immersion cooling.

Thermo-kinetic studies of in vitro digestion and colonic fermentation of inulin/Lactobacillus rhamnosus GG co-encapsulated composite beads

In this study, Lactobacillus rhamnosus GG (L.GG) and inulin were successfully co-encapsulated into alginate/pectin composite beads using high efficiency vibration technology with freeze-drying. The addition of inulin did not substantially affect the morphology or particle size of microcapsules but improved the survival number of L.GG during encapsulation process, storage and in vitro digestion. Isothermal microcalorimetry was used for the first time to investigate the thermo-kinetics properties of these encapsulated L.GG during in vitro gastrointestinal digestion and colon fermentation, revealing that the co-encapsulation with inulin increased the growth rate of L.GG in the logarithmic growth phase, without change the total heat production. The number of probiotic microcapsules surviving after 60 days of storage was still more than 8 Log CFU/g. Inulin co-encapsulation also significantly improved the storage and heat stability of L.GG, with the highest viability of 8 Log CFU/g after 60-day storage, 5.58 Log CFU/g after heating at 63 °C for 30 min, and 7.85 Log CFU/g at 72 °C for 3 min, respectively. These microcapsules also altered the composition and diversity of mice gut microbiota, increasing the relative abundance of Lactobacillus and decreasing that of Bacteroides. This study introduces a novel colon-targeted probiotic-delivery system and a method to understand the control-release thermodynamics of the encapsulated probiotics in simulated gastrointestinal digestion and colonic fermentation.

381 Evaluating Indirect Measures of Milk Production in Heat-Stressed Lactating Sows Genomically Selected for Improved Thermotolerance

Abstract Lactating sows are among the most heat stress sensitive population in the swine herd. Exposure to high ambient temperatures causes a marked decrease in production measures and welfare in lactating sows and may have a negative downstream impact on piglet growth due to impaired sow lactogenesis. Genomic selection for improved heat stress (HS) tolerance may be a viable method to reduce the negative impacts of HS on lactating sows and their offspring. However, selection for HS tolerance is generally associated with decreased productivity. Therefore, the study objective was to evaluate the impact of genomic selection for thermotolerance on indirect measures of sow milk production under HS conditions. We hypothesized that heat tolerant sows would have a decrease in indirect measures of milk production when compared with heat sensitive sows. A total of 20 multiparous lactating sows (Large White x Landrace; parity = 4.85 ± 0.75) divergently genomically selected for heat tolerance (TOL; n = 11) or heat sensitivity (SEN; n = 9) were subjected to cyclic HS temperatures (28 to 32° C) from day 2.5 ± 1.0 post-farrowing until weaning (d 21.3 ± 1.1). On d 4, 8, 14, and 18 of lactation, indirect calorimetry was used to estimate total heat production (THP) on an individual sow basis following previously published methods by our group. In addition, sow respiration rate (RR) was measured daily at 0800, 1200, 1600, and 2000 h. All data were analyzed using PROC GLIMMIX in SAS 9.4 with individual sow included as the experimental unit. It was determined that TOL sows had an overall increase (P = 0.04; 5.68 ± 0.24 kcal·sow· kg BW0.75(-1)) in THP when compared with SEN sows (4.74 ± 0.18 kcal·sow· kg BW0.75(-1)). A treatment by day effect was observed where THP was greater (P &amp;lt; 0.01; 88%) for TOL sows on d 4 of lactation when compared with SEN sows. Preliminary evidence suggests that TOL sows had an overall increase (P = 0.01) in RR (78 ± 5 bpm) when compared with SEN sows (73 ± 5 bpm). Taken together, these data suggest that genomic selection methods used to increase lactating sow thermotolerance may have had a positive impact on indirect measures of lactogenesis under HS conditions.

Impact of the Core Deformation on the Tidal Heating and Flow in Enceladus' Subsurface Ocean

AbstractWe present a novel approach to modeling the tidal response of icy moons with subsurface oceans. The problem is solved in the time domain and the flow in the ocean is calculated simultaneously with the deformation of the core and the ice shell. To simplify the calculations, we assume that the internal density interfaces are spherical and the effective viscosity of water is equal to or greater than 100 Pa s. The method is used to study the effect of an unconsolidated core on tidal dissipation in Enceladus' ocean. We show that the partitioning of tidal heating between the core and the ocean strongly depends on the thickness of the ocean layer. If the ocean thickness is significantly greater than 1 km, heat production is dominated by tidal dissipation in the core and the amount of heat produced in the ocean is negligible. In contrast, when the ocean thickness is less than about 1 km, tidal heating in the core diminishes and dissipation in the ocean increases, leaving the total heat production unchanged. Extrapolation of our results to realistic conditions indicates that tidal flow is turbulent which suggests that the linearized Navier‐Stokes equation may not be appropriate for modeling the tidal response of icy moons. Finally, we compare our results with those obtained by solving the Laplace tidal equations and discuss the limitations of the two‐dimensional models of ocean circulation.

Process modeling and analysis of a combined heat and power system integrating solid oxide fuel cell and organic Rankine cycle for poultry litter utilization

Syngas from the gasification process of poultry litter can be utilized as the fuel in the solid oxide fuel cell for electricity production. A novel combined heat and power system, integrating solid oxide fuel cell and organic Rankine cycle, is currently proposed to achieve efficient and clean utilization of poultry litter. The effects of biomass type for co-gasification and six operational parameters on this cogeneration system are studied. Results show that the total electricity production, fuel cell power output, total heat production and primary energy utilization efficiency are 162.02 kW, 141.65 kW, 52.41 kW and 44.70%, respectively. Co-gasification of straw and poultry litter can improve the overall system performance. Low water content of poultry litter is generally preferable. The highest primary energy utilization is achieved at equivalent air ratio of around 0.26. Increasing water-carbon ratio would deteriorate the fuel cell and the overall system performance. When the operating temperature is 950 °C, the energy utilization efficiency reaches the peak value. This energy efficiency reaches the maximum value of 44.98% at fuel utilization efficiency of 0.78. This research provides a new solution for high-value utilization of the low-calorific poultry litter, to achieve the sustainable utilization of wasted energy and biomass resources.

Multi-source district heating system full decarbonization strategies: Technical, economic, and environmental assessment

Implementing innovation and sustainable development of district heating requires sound energy planning at the national and local levels. However, a research gap still exists on technically and economically viable solutions for developing fully decarbonized heat supply systems and assessing their environmental impact to provide a holistic analysis. Therefore, the case study-based research includes in-depth analyses of the current situation and existing operating conditions of the solar field, biomass and natural gas boilers, and thermal storage tank. The future fossil-free scenarios analyze the additional thermal storage capacity, and integration of heat pumps and local waste heat sources to reduce fossil fuel consumption, increase energy efficiency and minimize heat production costs.The results show that the waste heat utilization and heat pump integration allow to phase-out of natural gas for the peak load coverage. However, increasing thermal storage capacity by more than 50 % is crucial to store the thermal energy for peak demand-supply. The increased thermal storage tank volume allows higher biomass production rates and aligns the heat production with the available waste heat sources. The total heat production costs in a low-temperature heat pump scenario decrease by 5 %. The environmental impact assessment shows that the low-temperature heat pump scenario decreases the resource category by 61 % and the climate change category by 17 % in comparison with the Reference scenario due to higher solar yield and higher overall efficiency.

Energy utilization and requirement of broiler breeders during the production phase

This study aimed to evaluate energy utilization and propose models for metabolizable and net energy requirements in broiler breeders during the egg production phase. Sixty Cobb500 broiler breeders aged between 29 and 65 wk were randomly assigned to 3 feeding levels. At each age, 6 birds were adapted for 8 d to 3 levels of metabolizable energy intake (MEi), established based on the amount of feed allocated: 1) the amount of feed recommended in the guideline, 2) 25% above, and 3) 25% below. The birds were housed in respirometry chambers for 6 d (1 adaptation, 4 feeding state, 1 fasting) to measure oxygen consumption and carbon dioxide production to calculate heat production (HP) and fasting HP (FHP). Daily measurements of feed intake, egg weight, egg production, and total excreta were recorded. Variables of MEi, HP, and retained energy (RE) in the egg were calculated, while RE in the body and its partitioning into fat and protein in the egg and body were calculated from MEi, total HP (THP), and RE in the egg. Statistical analysis involved linear regression of multiple factors with MEi and age (categorical) as the independent variables. Pearson correlation analysis was conducted to investigate the relationship between visceral mass and the evaluated variables. The study proposed mixed models for developing models of energy requirements for both metabolizable (ME) and net systems (NE). The study found that FHP (average 259 ± 20.08 kJ/kg0.75*d) remained constant throughout the production cycle regardless of the MEi level (P > 0.05). The efficiency of energy utilization for depositing protein and fat in the body changed with the bird's age. The lower error model was considered to select ME requirements for maintenance, egg, and gain efficiencies, disregarding the effect of age. The efficiencies were 0.89, 0.78, and 0.80 for maintenance, gain, and egg production, respectively. The NE was unaffected by age and showed a lower error than the ME model. The NE system was found to be more accurate in expressing the energy requirements of broiler breeders.

Influence of site characteristics on the performance of shallow borehole heat exchanger arrays: A sensitivity analysis

Using borehole heat exchangers (BHE) to extract shallow geothermal energy has grown rapidly in recent years. How to maintain a long-term balanced, sustainable operation of the BHE arrays becomes a key issue. Site characteristics, including hydrogeological and geothermal conditions as well as spatial distribution of subsurface physical parameters, are generally idealized or partly neglected in practice. To investigate the consequences of such simplifications, a 3D model, based on data from a planned real site, is established to consider groundwater flow, subsurface heterogeneity, and various hydrogeothermal boundary conditions. After verifying the model, a sensitivity analysis is conducted. Nine factors regarding site characteristics are selected, including Darcy flux in the aquifer, thermal conductivity and volumetric heat capacity of the ground, groundwater depth, thermal and hydraulic heterogeneity, geothermal gradient, heat transfer coefficient on the ground surface and seasonal rainfall. Sensitivity results indicate that the annual total heat production is most sensitive to geothermal gradient, followed by Darcy flux, both of which have positive effects. Groundwater depth and heat transfer coefficient have negative effects on annual heat production. Compared to thermal heterogeneity and rainfall, the influence of hydraulic heterogeneity is higher. Uncertainty of annual heat production due to various Peclet numbers is quantified through regression analysis.

Global Crustal Thickness Revealed by Surface Waves Orbiting Mars

AbstractWe report observations of Rayleigh waves that orbit around Mars up to three times following the S1222a marsquake. Averaging these signals, we find the largest amplitude signals at 30 and 85 s central period, propagating with distinctly different group velocities of 2.9 and 3.8 km/s, respectively. The group velocities constraining the average crustal thickness beneath the great circle path rule out the majority of previous crustal models of Mars that have a &gt;200 kg/m3 density contrast across the equatorial dichotomy between northern lowlands and southern highlands. We find that the thickness of the Martian crust is 42–56 km on average, and thus thicker than the crusts of the Earth and Moon. Considered with the context of thermal evolution models, a thick Martian crust suggests that the crust must contain 50%–70% of the total heat production to explain present‐day local melt zones in the interior of Mars.

Simulation of wellbore temperature and heat loss in production well in geothermal site

ABSTRACT Knowledge of fluid flow temperature along the wellbore can be useful for a realistic calculation of the total heat production in geothermal wells. Therefore, wellbore modeling is an important part of the characterization of geothermal wells and predicting their future behavior. This study describes the dynamic transport of transient heat and fluid dynamic transport inside a geothermal well and also heat loss in the surrounding rocks. The objective of this investigation is to accurately predict temperature and pressure variations within the producing well GPK2 of the geothermal site Soultz-sous-Forêts. The temperature effect of possible leakage zones in the reservoir section of the production casing was also considered. A single-phase flow modeling was carried out using Comsol software. Our study highlights that the properties of the flow (well flow rates for steady and unsteady flow), of the fluid (density, viscosity, chemical composition), and the well (diameter, length, thermal properties of environments) are parameters, which directly influence the pressure and temperature profiles of the well. A sensitivity study has been carried out to demonstrate the role that these parameters play in the heat transport occurring in this well. According to our simulated results, during the flow of hot water in GPK2 well the production temperature of water decreases by dozen degrees of its downhole temperature. It is also shown that the leakage zone affects the temperature, decreasing it at least by 1–2°C.

Effects of body size and countermeasure exercise on estimates of life support resources during all-female crewed exploration missions

Employing a methodology reported in a recent theoretical study on male astronauts, this study estimated the effects of body size and aerobic countermeasure (CM) exercise in a four-person, all-female crew composed of individuals drawn from a stature range (1.50- to 1.90-m) representative of current space agency requirements (which exist for stature, but not for body mass) upon total energy expenditure (TEE), oxygen (O2) consumption, carbon dioxide (CO2) and metabolic heat (Hprod) production, and water requirements for hydration, during space exploration missions. Assuming geometric similarity across the stature range, estimates were derived using available female astronaut data (mean age: 40-years; BMI: 22.7-kg·m−2; resting VO2 and VO2max: 3.3- and 40.5-mL·kg−1·min−1) on 30- and 1080-day missions, without and with, ISS-like countermeasure exercise (modelled as 2 × 30-min aerobic exercise at 75% VO2max, 6-day·week−1). Where spaceflight-specific data/equations were not available, terrestrial equivalents were used. Body size alone increased 24-h TEE (+ 30%), O2 consumption (+ 60%), CO2 (+ 60%) and Hprod (+ 60%) production, and water requirements (+ 17%). With CM exercise, the increases were + 25–31%, + 29%, + 32%, + 38% and + 17–25% across the stature range. Compared to the previous study of theoretical male astronauts, the effect of body size on TEE was markedly less in females, and, at equivalent statures, all parameter estimates were lower for females, with relative differences ranging from -5% to -29%. When compared at the 50th percentile for stature for US females and males, these differences increased to − 11% to − 41% and translated to larger reductions in TEE, O2 and water requirements, and less CO2 and Hprod during 1080-day missions using CM exercise. Differences between female and male theoretical astronauts result from lower resting and exercising O2 requirements (based on available astronaut data) of female astronauts, who are lighter than male astronauts at equivalent statures and have lower relative VO2max values. These data, combined with the current move towards smaller diameter space habitat modules, point to a number of potential advantages of all-female crews during future human space exploration missions.