High Ambient Temperature Conditions Research Articles

Simulation study on the performance of a vapor-bypassed evaporator for heat pump applications

• A mathematical model for the vapor-bypassed evaporator is developed. • Corresponding experiments were conducted to validate the model accuracy. • Entropy generation is applied to evaluate the evaporator overall performance. • Phase separation position and channel number of the evaporator are optimized. This paper presents a simulation study on the vapor-bypassed evaporator for heat pump applications. The vapor-bypassed evaporator, in which a phase separator is set in the middle of the refrigerant circuit to bypass vapor refrigerant, can reduce the refrigerant pressure drop for enhancing the evaporator overall performance. A mathematical model for the vapor-bypassed evaporator is developed and the experiments were conducted to validate its accuracy. Based on the entropy generation minimization theory, the optimum phase separation positions and refrigerant channel numbers of the evaporator for various operation conditions are selected out. According to the simulation results, as the required heat transfer capacity ranges 4~10 kW, the vapor-bypassed (VB) mode obtains 25.6~84.6 kPa lower refrigerant pressure drop and 3.1~25.3% lower entropy generation than the conventional operation (CO) mode. Moreover, when the ambient temperature ranges 5~15°C, the entropy generation of VB mode is decrease by 22.3~11.5% than CO mode. In general, applying the vapor-bypassed technique is a promising way for improving the evaporator performance especially under high heat transfer capacity and low ambient temperature conditions.

Physics Based Degradation Models for Electrolytic Capacitor Prognostics under Thermal Overstress Conditions

Electronics subsystems play an increasingly important role in safety critical systems for monitoring, control, and enhanced functionality. Electrolytic capacitors are an important component in ,amy subsystems that range from power supplies on safety critical avionics equipment to power drivers for electro-mechanical actuators. These capacitors are ideal forpassing or bypassing low-frequency signals in power supplies but are known to have lower reliability compared to ceramic and tantalum capacitors, and given their criticality in electronicssubsystems they are a good candidate for component level monitoring and prognostics. Prognostics provides a way to assess remaining useful life of components and systems based on their current state of health and their anticipated future use and operating conditions. Past experiences have shown that capacitor degradation and failures are quite prevalent under high electrical and thermal stress conditions that they experience during operations. Our focus in this work is on deriving a physics-based degradation model for electrolytic capacitors under thermal stress conditions. As part of our methodology, we study the effects of accelerated aging due to thermal stress on a batch of capacitors stored at high ambient temperature conditions. This provides a framework for supplementing theoretical modeling with data collected from simultaneous experiments, which is then used to validate the derived models. This work represents a first step toward combining data driven and physics-based approaches for modeling capacitor degradation. The case study shows how the proposed technique is applied to a batch of identically manufactured capacitors.

The non-ideal evaporation behaviors of ethanol/heptane droplets: Impact on diameter, temperature evolution and the light scattering by droplet at the rainbow angle

This paper aims to investigate the influence of non-ideal vapor-liquid equilibrium (VLE) on the heating and evaporation of ethanol/heptane binary droplets. Three correction parameters, the activity coefficient, the Poynting factor, and the fugacity coefficient, are incorporated in the Effective Thermal Conductivity Model (ECM) and Effective Diffusivity Model (EDM) to present the non-ideal behavior at droplet surface. Rainbow theory was used to present the difference between the ideal and non-ideal models by predicting the scattering light patterns with the obtained results. The evaporation process of ethanol/heptane droplet was performed by the ideal and non-ideal VLE methods, with the ambient temperature varying from 473 K to 673 K, ambient pressure of 1 and 10 bar, together with the initial mass fraction of heptane in liquid phase ranging from 0 to 1. The results indicate firstly, the effect of non-ideal behavior on evaporation constant and temperature evolution is more pronounced for the droplets with initial heptane mass fraction of 25% and 50% inside the mixture. This reveals that when the lighter component dominates the mixture, the assumption of an ideal mixture is less accurate. Secondly, for the non-ideal system, the liquid phase composition is an important factor in deciding the evaporation order of different components in the mixture. In some situations, the less volatile fuel evaporates faster than the more volatile part in the mixture. Moreover, the influence of non-ideal behavior is attenuated under high ambient temperature and pressure conditions as presented by the relatively smaller value of separation factor. Lastly, the obtained simulation results were analyzed with the rainbow theory by predicting the scattering light patterns by droplet at the rainbow angle. The difference in the scattering light patterns was analyzed.

Experimental study of the effect of C8 oxygenates on sooting processes in high pressure spray flames

Oxygenated compounds have the ability to reduce soot emissions and to improve the combustion efficiency in engines. Most studies have focused on the soot reduction potential of shorter carbon chain oxygenates, whilst longer carbon chain oxygenates are still relatively unexplored. In this work, the soot reduction potential of long carbon chain oxygenates having similar thermo-physical and chemical properties to those of diesel have been studied, viz., 2-octanone (ketone), 1-octanol (alcohol), hexyl acetate (ester) and octanal (aldehyde). These oxygenates were injected at high pressure into a constant volume chamber maintained at high ambient temperature conditions, and their spray flames were investigated using a high-speed, two-colour pyrometry system. It was found that for the same injected fuel mass, the oxygenates reduced the overall soot when compared to diesel. Small differences in sooting tendencies were observed between different oxygenated moieties but these were smaller than those relative to diesel. The absence of aromatic groups and the presence of oxygen directly bonded to carbon atoms seemed to have a larger effect on soot reduction than the oxygenated functional group. The oxygenates altered the local oxygen equivalence ratio in the spray, influencing the soot formation and its distribution in the flame. Under the high pressure conditions studied, the average sooting tendency of the long carbon-chain oxygenates studied increased in the order of: ester< aldehyde ~ alcohol<ketone.

Effects of Cyclic High Ambient Temperature and Dietary Supplementation of Orotic Acid, a Pyrimidine Precursor, on Plasma and Muscle Metabolites in Broiler Chickens.

The aim of this study was to evaluate the effects of high ambient temperature (HT) and orotic acid supplementation on the plasma and muscle metabolomic profiles in broiler chickens. Thirty-two 14-day-old broiler chickens were divided into four treatment groups that were fed diets with or without 0.7% orotic acid under thermoneutral (25 ± 1 °C) or cyclic HT (35 ± 1 °C for 8 h/day) conditions for 2 weeks. The chickens exposed to HT had higher plasma malondialdehyde concentrations, suggesting an increase in lipid peroxidation, which is alleviated by orotic acid supplementation. The HT environment also affected the serine, glutamine, and tyrosine plasma concentrations, while orotic acid supplementation affected the aspartic acid, glutamic acid, and tyrosine plasma concentrations. Untargeted gas chromatography–triple quadrupole mass spectrometry (GC-MS/MS)-based metabolomics analysis identified that the HT affected the plasma levels of metabolites involved in purine metabolism, ammonia recycling, pyrimidine metabolism, homocysteine degradation, glutamate metabolism, urea cycle, β-alanine metabolism, glycine and serine metabolism, and aspartate metabolism, while orotic acid supplementation affected metabolites involved in pyrimidine metabolism, β-alanine metabolism, the malate–aspartate shuttle, and aspartate metabolism. Our results suggest that cyclic HT affects various metabolic processes in broiler chickens, and that orotic acid supplementation ameliorates HT-induced increases in lipid peroxidation.

Correlation of neurological level and sweating level of injury in persons with spinal cord injury

Objective: Thermoregulatory dysfunction after spinal cord injury (SCI) impairs quality of life and predisposes persons to life-threatening sequela of heat-related illness (HRI) in conditions of high ambient temperature. SCI clinicians currently have no objective way to predict which persons are at greatest risk of HRI. Evaporative cooling via sweating is the body’s most efficient mechanism of heat dissipation. The relationship between the neurological level of injury (NLOI) and the degree of sudomotor dysfunction is not well defined. This study examines the relationship between the NLOI and sweating level of injury (SwLOI). This information can assist SCI clinicians in identifying individuals with SCI who have most impaired sudomotor function and thus highest risk of HRI. Design: Observational. Setting: Human physiology laboratory. Participants: 10 persons with tetraplegia (TP), 14 with paraplegia (PP) and 10 able-bodied (AB). Intervention: Passive heat stress (1°C rise in core temperature) with sweat responses (SR) quantified with the starch iodine test. Outcome measures: The most caudal dermatomal level in which sweating was visualized was recorded as the SwLOI, which was compared to the NLOI. Minimum, maximum and median differences between NLOI and SwLOI were calculated. Results: Persons with tetraplegia demonstrated no SR. Persons with paraplegia demonstrated SR at a median of 1 level below NLOI. Able-bodied controls demonstrated sweating on all skin surface areas. Conclusions: Persons with motor complete tetraplegia lack evaporative cooling capacity through SR during passive heat stress predisposing them to HRI. Meanwhile, persons with paraplegia sweat on average 1 dermatomal level below their NLOI.

High ambient temperature increases the toxicity and lethality of 3,4-methylenedioxymethamphetamine and methcathinone

RationaleMethylenedioxymethamphetamine (MDMA) and methcathinone (MCAT) are abused psychostimulant drugs that produce adverse effects in human users that include hepatotoxicity and death. Recent work has suggested a connection between hepatotoxicity, elevations in plasma ammonia, and brain glutamate function for methamphetamine (METH)-induced neurotoxicity. ObjectivesThese experiments investigated the effect of ambient temperature on the toxicity and lethality produced by MDMA and MCAT in mice, and whether these effects might involve similar mechanisms to those described for METH neurotoxicity. ResultsUnder low (room temperature) ambient temperature conditions, MDMA induced hepatotoxicity, elevated plasma ammonia levels, and induced lethality. Under the same conditions, even a very high dose of MCAT produced limited toxic or lethal effects. High ambient temperature conditions potentiated the toxic and lethal effects of both MDMA and MCAT. ConclusionThese studies suggest that hepatotoxicity, plasma ammonia, and brain glutamate function are involved in MDMA-induced lethality, as has been shown for METH neurotoxicity. The toxicity and lethality of both MDMA and MCAT were potentiated by high ambient temperatures. Although an initial mouse study reported that several cathinones were much less toxic than METH or MDMA, the present results suggest that it will be essential to assess the potential dangers posed by these drugs under high ambient temperatures.

Effect of Lance Structure on Behavior of Coherent Jet in EAF Steelmaking Process.

During the electric arc furnace steelmaking process, the coherent jet technology was widely used to protect the kinetic energy of the supersonic oxygen jet and achieve better mixing effects. Comparing with the conventional oxygen lance, the coherent lance could increase the surface area of impaction cavity, resulting in a better stirring effect and higher reaction rate. However, there was limited research about the effect of restriction structure for the coherent lance tip on the flow field characteristic of the main oxygen jet. In this research, three kinds of restriction structures have been investigated by numerical simulation and combustion experiment at room and high ambient temperature conditions. Then an optimum restriction structure would be tested in a 75 t electrical arc furnace steelmaking process to verify its metallurgical property.

System simulation on refrigerant-based battery thermal management technology for electric vehicles

Progress in the higher requirements for battery thermal management system (BTMS), a new refrigerant-based BTMS of electric vehicles (EVs) is proposed and analyzed, especially designed for high ambient temperature and high speed dynamic conditions. Based on the vehicle system framework, the thermal response, energy efficiency and irreversibility of the system are discussed hereunder. As indicate by the results, the average temperature of battery module and temperature difference between cells are effectively controlled. In addition, energy analysis is performed under different conditions, including energetic coefficient of performance (COPen) and exergetic coefficient of performance (COPex). The intensification of driving conditions has a negative impact on both COPen and COPex, while the increase of ambient temperature reduces COPen and promotes COPex. Further, the effects of BTMS on the air conditioning (AC), and their consequences are explored. Through a cabin-prioritized control strategy and a series-connected system configuration, this paper aims to improve the system performance and make progresses on the whole vehicle thermal management system.

Tissue storage solution for preservation and transfer of forensic specimen in high ambient-temperature

Storage of tissue samples in high ambient-temperature can affect the quality of forensic evidence. Experiments were conducted to investigate the potential use of 3 tissue storage solutions for the preservation and transfer of forensic specimen in high ambient temperature conditions, i.e., DMSO, Longmire’s buffer, and trehalose solution. Results showed that DNA in tissue was best preserved in DMSO buffer. Samples preserved in Longmire’s buffer gave DNA analysis results for temperatures up to 60 °C, however, amplification between replications were not reproducible. For those tissue samples preserved in trehalose solution, DNA markers larger than 300 bp were absent, and irreproducible amplification results were detected at a higher level when the storage temperature increased, and storage time was over 2 weeks. Tissue storage condition at high temperature over 1 week is not recommended. Experimental results here provided an alternative collection and preservation method for tissue samples at ambient temperature (without cold-storage) for subsequent DNA analysis. These can potentially be implemented in forensic biological evidence collection, preservation and transfer in hot climates.

Exergy analysis of a solar regenerated liquid desiccant assisted air conditioning system for hot and humid climates

In this paper, exergy analysis of a novel solar powered liquid desiccant assisted air conditioning system is presented and simulated. The system aims to provide suitable thermal comfort conditions inside large office buildings with high internal loads situated in the hot and humid tropical/subtropical countries of the world. The system consists of process and regenerating air streams, a liquid desiccant solution loop and a cooling water loop. The primary objective of this study is to present the exergy of cooling capacity along with the overall exergy efficiency of the proposed system. The study helps to quantify the optimum operating and design parameters for system operation based on the second law of thermodynamics. For the base case, which is representative of a hot and humid climatic condition, the proposed system is able to maintain the room air conditions within the moderate thermal acceptability criterion. The exergy of cooling capacity and exergy efficiency for the base case is about 2900 W and 2 % respectively. Parametric analyses show that the system performs the best under conditions of high ambient insolation and temperature, low ambient humidity and a process air to desiccant solution mass flow rate of about 3 in the dehumidifier.

Effects of astaxanthin-rich dried cell powder from Paracoccus carotinifaciens on carotenoid composition and lipid peroxidation in skeletal muscle of broiler chickens under thermo-neutral or realistic high temperature conditions.

Thirty‐two 15‐day old broiler chicks (Chunky strain ROSS 308) were randomly divided into four treatments in a 2 × 2 factorial design. The main factors were diet (basal diet or basal diet supplemented with 0.15% astaxanthin‐rich dried cell powder (Panaferd‐P [astaxanthin 30 ppm]) and ambient temperature (thermo‐neutral [25 ± 1°C] or high [35 ± 1°C for 6 hr]). Dietary supplementation with Panaferd‐P did not affect growth performance, though high ambient temperature decreased feed intake and the weight of breast tender muscle, liver, and heart. High ambient temperature also decreased redness in both breast and leg muscles of chickens, while Panaferd‐P increased redness and yellowness of breast and leg muscles of chickens. Panaferd‐P increased Paracoccus carotinifaciens‐derived pigments (i.e., adonixanthin, astaxanthin, adonirubin, and cantaxanthin) as well as corn‐derived pigments such as zeaxanthin and lutein in breast and leg muscles. High ambient temperature increased the malondialdehyde (MDA) concentration in breast muscle, while Panaferd‐P decreased the MDA concentration in breast muscle under both temperature conditions. Our results suggest that dietary supplementation with Panaferd‐P increases muscle carotenoid content, the redness and yellowness of meat and decreases the muscle MDA concentration in broiler chickens kept under thermo‐neutral or high ambient temperature conditions.

The effect of dietary ions difference on drinking and eating patterns in dairy goats under high ambient temperature.

ObjectiveThe present study was carried out to evaluate the effect of high dietary cation and anion difference (DCAD) rations on diurnal variations in eating and meal patterns, water intake and urination patterns in dairy goats fed under high ambient temperature (HTa).MethodsTen crossbred dairy goats during peri-parturition period were selected and divided into two groups of five animals each. Experimental diets were control DCAD (control, 22.8 mEq/100 g dry matter [DM]) and high DCAD (DCAD, 39.1 mEq/100 g DM). The composition of two diets consisted of 44% corn silage and 56% concentrate. From the 2nd week to 8th week postpartum, goats were fed ad libitum twice daily either with the control or DCAD total mix ration with free access to water. The spontaneous eating and drinking patterns were determined.ResultsThe environmental conditions in the present experiment indicated that goats were fed under HTa conditions (average peak THI = 85.2) and were in heat stress. In addition to the typical HTa induced tachypnoea in both groups, the respiratory rate in the DCAD group was significantly higher than the control group (p<0.05). Although the goats from both groups showed comparable level of eating, drinking and urination during experiment, the meal pattern and water intake were different. High DCAD apparently increased eating and meal patterns compared with the control. At week 8 postpartum, goats from high DCAD group had significant (p<0.05) bigger meal size and longer meal duration. Moreover, high DCAD appeared to increase night-time water intake (p<0.05).ConclusionBoth meal pattern and night-time drinking effects of DCAD suggested that feeding with high DCAD ration may alleviate the effect of heat stress in dairy goat fed under HTa conditions.

The effect of purslane hydroextract and zinc on performance, antioxidant capacity and immunity of broiler chickens during summer conditions

Abstract. Due to negative effects of high ambient temperature, the present study was conducted to investigate the effects of Portulaca oleracea hydroextract (PHE) and zinc (Zn) on the growth performance and immunity of broiler chickens reared under high summer ambient temperature conditions. A total of 420 day-old male broiler chickens (Ross 308) were randomly allocated to seven dietary treatments each replicated four times with 15 birds per replicate. The basal diet as the control diet was supplemented with 100 mg kg−1 butylated hydroxytoluene (BHT), or 300 and 600 mg kg−1 of PHE, 100 mg kg−1 of zinc and 100 mg kg−1 of zinc plus 300 or 600 mg kg−1 of PHE (ZP300 and ZP600). The result of the present study showed that Zn, PHE and their combination did not alter daily feed intake and feed conversion ratio. Although there was a tendency toward an increase in broiler body weight at 24 and 44 days of age (P=0.059 and P=0.061), the body weight of birds fed the basal diet supplemented with Zn reduced at day 10. The birds fed diets supplemented with BHT or ZP600 showed lower aspartate aminotransferase (ASAT) and lactate dehydrogenase activity at 24 days of age (P&lt;0.05), but it remains lower in the ZP600 group only for ASAT activity level at day 44. The results of the present study suggest that dietary PHE and Zn supplementation partially improved body weight and serum antioxidant capacity, superoxide dismutase activity and antibody titer against sheep red blood cells and Newcastle diseases in the broiler chickens during summer conditions.

Automatic air temperature control in a container with an optic-variable wall

Solar energy is one important source of sustainable and green energy. However, solar radiation is not always demanded as heat source for building in seasons. Automatic air temperature control with an optic-variable wall is proposed in this paper to reduce the HVAC (Heating, Ventilation & Air-Conditioning) energy consumption in containers. The feasibility of an optic-variable wall (OVW) is first verified with sample-test on the color, reflectivity and absorbance with UV 3600. The reference for relectivity test is BaSO4 and the reference for absorbance test is quartz. The feasibility of its performance on air temperature control inside a container is verified with preliminary experiments under natural winter conditions at a low ambient temperature. It is checked that the color of OVW varies from dark at low temperature to light at high temperature. The reflectivity of OVW is small at low temperature and high at high temperature. Then, the theoretical investigation on air temperature inside a container is conducted. It is concluded that air inside a container is simultaneously kept cool in summer and warm in winter, with the adoption of OVW. The stable air temperature rise is small under the conditions of high ambient temperature and large solar radiation, leading to the potential of less energy consumption for cooling in summer, while it is large under the conditions of low ambient temperature and small solar radiation, leading to the potential of less energy consumption for heating in winter. The variation range of the stable air temperature with OVW is also narrower. The results are helpful for green design and energy saving in containers.

Genetic selection for growth performance and thermal tolerance under high ambient temperature after two generations using heat shock protein 90 expression as an index

Genetic selection for productive performance in high ambient temperatures was performed on two chicken strains, Rhode Island Red and Sinai, for two generations, and the heritable responses to tolerance were estimated using heat shock protein 90 (HSP90) gene expression. The results are summarised as follows: (1) heat stress negatively affected some economic traits, mainly bodyweight. This effect was more pronounced in the parent stock than in the first generation (F1) and second generation (F2). (2) This effect was modulated by the chicken strain, and the decreased bodyweight was more pronounced in RI strain than in the Sinai strain, indicating that the Sinai strain is more tolerant to high ambient temperature. (3) The offspring (F1 and F2) of both strains were more tolerant to high ambient temperature; this trend was also true for the parents of these two strains. (4) HSP90 mRNA expression was the same in both strains under normal conditions in all three generations. (5) Under high ambient temperature conditions, the Sinai strain (all generations) showed significantly increased HSP90 mRNA expression compared with the Rhode Island Red strain. These findings suggest that heat tolerance is passed from parents to offspring. We recommended that selection for heat-stress tolerance be applied to producing commercial strains reared in hot climate conditions.

Effect of wall surface temperature on ignition and combustion characteristics of diesel fuel spray impingement

This paper investigated the ignition and combustion characteristic of wall-impinged diesel sprays in a constant volume combustion vessel simulated the diesel engine condition. A steel flat wall was installed perpendicular to the fuel injector axis. Wall surface temperatures were set at 45 °C, 90 °C, 150 °C, 280 °C, 380 °C, 460 °C, 510 °C and 570 °C separately, and a single nozzle hole with a diameter of 0.12 mm was adopted. Direct image method was applied to capture the natural luminosity and liquid spray to analyze the ignition and initial combustion process. The results reveal that, with the decrease of the wall temperature, ignition delay time becomes longer and the ignition positions become farther away from the wall. The total flame luminosity reduced and more time has been spent to reach the saturation under low wall temperature. When the wall surface temperature decreased, both flame height and flame width reduced. And they decreased more sharply in the low temperature zone. There obviously exists the temperature gradient near the wall surface for the low temperature surface is in the high ambient temperature condition. The low temperature zone was negative to the ignition and initial combustion of the fuel mixture. For this reason, the initial ignition location transferred to the high temperature zone.

Measured Efficiency of a Luminescent Solar Concentrator PV Module Called Leaf Roof

A functional prototype of a luminescent solar concentrator photovoltaic (LSC PV) module, called Leaf Roof, aims at demonstrating the design features of LSC PV technologies such as coloring, transparency, and flexibility in physical shape. In this paper, the prototype is presented and the first measurements of its performance are shown. The geometrical gain of this new type of PV module is 3.6. For two types of Leaf Roof modules, I – V curves have been measured resulting in efficiencies of 5.8% for a red-colored PV module, and 5.5% for a green-colored PV module under similar conditions. These results demonstrate colorful, robust solar energy collectors which can be produced in a wide variety of shapes are viable, attractive devices for use in building integrated systems. Additionally, thanks to the use of poly(methyl methacrylate) (PMMA) as a cell encapsulant, the Leaf Roof modules are less susceptible to energy losses at elevated temperatures due to high irradiance and high ambient temperature conditions.

Water-soluble silicate gelants: Comparison and screening for conformance control in carbonate naturally fractured reservoirs

This work compares and screens green, water-soluble silicate gelants for possible use in isolating high conductivity water paths in fractured carbonate formations. The impact of cation, K+, Na+, Li+, Al3+, in the structure of a silicate is investigated with regards to gelation time, gel strength, and gel shrinkage. Several activators, such as NaCl, HCl, HCl+NaCl, HCl+NaCl+CaCl2, SAAP (sodium acid pyrophosphate) and CitAc (citric acid), are tested with the silicate systems at 40°C, 60°C and 80°C and evaluated based on their ability to form rigid gels and on gelation time. The ability of the silicate gelants to form gel and the gelation time are determined mainly by the type of silicate, the SiO2 to M2O ratio (M denotes a metal ion), the type and concentration of the activator, and temperature. Some silicates do not always form gels; when gels are formed for a given silicate gelant, the gelation time is a strong function of the activator type and concentration, and temperature. Other parameters tested include pressure, ethylenediaminetetraacetic acid (EDTA) (chelating agent), and formaldehyde (bactericide for added xanthan).The impact of elevated pressure on the designed gelation time of silicate gelants is very important for field applications in the oil and gas industry. Results obtained from experiments conducted at high pressures (150 and 300bar) and ambient temperature conditions showed that applied high pressures delay gelation of a given silicate gelant compared to gelation times observed at standard pressure and desired temperature conditions.Silicate gelants containing divalent ions display shorter gelation times at given conditions (silicate, activator, pressure and temperature) compared to ones of the same salinity without divalent ions. The use of EDTA as complexing agent to neutralize or partially control the impact of divalent ions on gelation time may not be efficient; therefore, the impact of these ions on gelant's gelation and gel properties must be considered. The addition of formaldehyde as bactericide to prevent long-term degradation of added xanthan was found to reduce gelation times and decrease gel strength. Formed gels from diluted Silicate A and Silicate C gelants (these gelants are defined in the next section of this paper) showed a similar behavior (gelation time) as the one of gels formed from non-diluted gelants.Gel shrinkage is a function of the gelant type and SiO2 to M2O ratio, temperature, and storage time. Silicate A gels display a low degree of shrinkage; Silicate C gels appear to be affected significantly by high temperatures (60°C and 80°C) with the gels displaying up to 80% shrinkage at long post-gelation storage times; Silicate C gels are less affected (lower shrinkage) at low temperatures (40°C).

Influence of dietary cation–anion difference in finishing diets fed to Holstein steers during periods of high ambient temperature on feedlot performance and digestive function

ABSTRACTOne hundred twenty-six Holstein steers (457.1 ± 27.5 kg BW) were used in a 127-d experiment to evaluate the influence of dietary cation–anion difference (DCAD) on growth performance and carcass characteristics. Treatments consisted of steam-flaked corn-based diets supplemented to provide DCAD of 34, 84 or 134 mEq/kg diet DM. There was no treatment effect (P > .20) on ADG, DMI, gain efficiency or dietary NE. Six Holstein steers (196 ± 3 kg) with cannulas in rumen and proximal duodenum were used in a replicated 3 × 3 Latin Square design to evaluated treatment effects on digestion characteristics. The DCAD did not affect (P > .20) ruminal or total digestion of OM, NDF, starch and N, or ruminal pH and VFA molar proportions. It is concluded that increasing DCAD of Holstein steers fed a conventional steam-flaked corn-based diet under conditions of high ambient temperature will not enhance growth performance.