The indirect dry cooling system, consisting mainly of the dry cooling tower and condenser, keeps energy balance under stable state. However dry cooling tower is easily influenced by the variation of ...ambient condition, like ambient temperature and crosswind, and theses unfavorable effects will affect the operation of the condenser directly and further impact unit efficiency. Therefore it is necessary to study the effects of ambient temperature and crosswind on thermo-flow performance of the tower under energy balance of the indirect dry cooling system. Taking a 600 MW indirect dry cooling system as an example, numerical simulation model of the dry cooling tower and thermal calculation model of the condenser are established respectively. With the method coupling the two models, the pressure, temperature fields and streamlines are presented. The indirect dry cooling system regains equilibrium after ambient condition varies, and parameters of the system under this stable state are obtained. These parameters reflect the effects of ambient conditions on the thermo-flow performance of the tower under energy balance of the system rather than under the condition that the tower is viewed as isolated. When the power unit is steady running with a certain load, outlet water temperature of the tower is approximately linear with ambient temperature, whereas nonlinear with crosswind speed. In addition, the computational models and coupled method mentioned in this paper are proved reliable enough for the performance prediction of the tower under energy balance of the indirect dry cooling system, which is beneficial to the economic and safe operation of the unit.
•Simulation model coupling the dry cooling tower and condenser is established.•The coupled method is based on energy balance of the indirect dry cooling system.•Outlet water temperature of the tower is nonlinear with crosswind speed.•Outlet water temperature of the tower is nearly linear with ambient temperature.•The coupled method is reliable for predictions under various working conditions.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Choline is an essential nutrient for pig development and plays a role in the animal's growth performance, carcass characteristics, and reproduction aspects in weaned pigs and sows. However, the ...effect of choline on finishing pigs and its potential regulatory mechanism remains unclear. Here, we feed finishing pigs with 1% of the hydrochloride salt of choline, such as choline chloride (CHC), under a basic diet condition for a short period of time (14 days). A 14-day supplementation of CHC significantly increased final weight and carcass weight while having no effect on carcass length, average backfat, or eye muscle area compared with control pigs. Mechanically, CHC resulted in a significant alteration of gut microbiota composition in finishing pigs and a remarkably increased relative abundance of bacteria contributing to growth performance and health, including Prevotella, Ruminococcaceae, and Eubacterium. In addition, untargeted metabolomics analysis identified 84 differently abundant metabolites in the liver between CHC pigs and control pigs, of which most metabolites were mainly enriched in signaling pathways related to the improvement of growth, development, and health. Notably, there was no significant difference in the ability of oxidative stress resistance between the two groups, although increased bacteria and metabolites keeping balance in reactive oxygen species showed in finishing pigs after CHC supplementation. Taken together, our results suggest that a short-term supplementation of CHC contributes to increased body weight gain and carcass weight of finishing pigs, which may be involved in the regulation of gut microbiota and alterations of liver metabolism, providing new insights into the potential of choline-mediated gut microbiota/metabolites in improving growth performance, carcass characteristics, and health.
The intestinal microbiota is required for maintaining the development and health of the host. However, the gut microbiota contributing to the regulation of the growth performance and health of Duroc ...and Yorkshire boars remains largely unknown. In this study, we first evaluated the difference in the growth performance between Duroc and Yorkshire boars when their body weight reached 100 kg. Relative to Duroc boars, Yorkshire boars weighed 100 kg at a younger age and exhibited a significantly lower backfat thickness and eye muscle area. Microbial analysis of the fecal samples revealed a marked difference in gut microbiota composition between the two pig models and remarkably increased α-diversity in Yorkshire boars compared to Duroc boars. Further analysis indicated that Bacteroidota, Prevotellaceae, and Ruminococcaceae might be associated with the growth performance and lean meat rate of Yorkshire boars. Taken together, these results highlight that Yorkshire boars exhibit a faster growth rate and higher lean meat rate compared to Duroc boars, and these differences may be attributed to the influence of the gut microbiota, thereby providing valuable insight into optimizing pig breeding systems and selecting terminal paternal sires to enhance overall productivity and quality.
The Yorkshire pigs, renowned for their remarkable growth rate, low feed conversion ratio (FCR), and high meat production, emerge as a novel preference for paternal breeding. In this study, we found ...that purebred paternal Yorkshire pigs (PY) surpass the purebred Duroc breed in terms of growth rate. Specifically, purebred PY attain a weight of 100 kg at an earlier age compared to purebred Duroc (Male, 145.07 vs. 162.91; Female, 145.91 vs. 167.57; p-value < 0.01). Furthermore, different hybrid combinations suggest that offspring involving purebred PY exhibit superior growth performance. Compared with purebred Duroc, the offspring of purebred PY have an earlier age in days (173.23 vs. 183.54; p-value < 0.05) at the same slaughter weight. The changes of plasma metabolites of 60-day-old purebred boars in the two sire-breeds showed that 1335 metabolites in plasma were detected. Compared with Duroc, 28 metabolites were down-regulated and 49 metabolites were up-regulated in PY. Principal component analysis (PCA) discerned notable dissimilarities in plasma metabolites between the two sire-breeds of pigs. The levels of glycerol 3-phosphate choline, cytidine, guanine, and arachidonic acid increased significantly (p-value < 0.05), exerting an impact on their growth and development. According to our results, PY could be a new paternal option as a terminal sire in three-way cross system.
In this study, we aimed to estimate the genetic parameters of the reproductive traits in three popular commercial pig breeds: Duroc, Landrace, and Yorkshire. Additionally, we evaluated the factors ...that influence these traits.
We collected data from a large number of litters, including 1,887 Duroc, 21,787 Landrace, and 74,796 Yorkshire litters. Using the ASReml-R software to analyze 11 traits, which included: total number of pigs born (TNB); number of piglets born alive (NBA); number of piglets born healthy (NBH); number of piglets born weak (NBW); number of new stillborn piglets (NS); number of old stillborn piglets (OS); number of piglets born with malformation (NBM); number of mummified piglets (NM); total litter birthweight (LBW); litter average weight (LAW); duration of gestational period (GP). We investigated the effects of 4 fixed factors on the genetic parameters of these traits.
Among the 11 reproductive-related traits, the gestational period belonged to the medium heritability traits (0.251-0.430), while remaining traits showed low heritability, ranging from 0.005 to 0.159. TNB, NBA, NBH, LBW had positive genetic correlation (0.737 ~ 0.981) and phenotype correlation (0.711 ~ 0.951). There was a negative genetic correlation between NBW and LAW (-0.452 ~ -0.978) and phenotypic correlation (-0.380 ~ -0.873). LBW was considered one of the most reasonable reproductive traits that could be used for breeding improvement. Repeatability of the three varieties was within the range of 0.000-0.097. In addition, the fixed effect selected in this study had a significant effect on Landrace and Yorkshire (
< 0.05).
We found a positive correlation between LBW and TNB, NBA, and NBH, suggesting the potential for multi-trait association breeding. Factors such as farm, farrowing year, breeding season, and parity should be taken into consideration in practical production, as they may impact the reproductive performance of breeding pigs.
The Liangshan pig is a traditional Chinese small-sized breed; it has a relatively long feeding period and low meat production ability but superior meat quality. This study utilized three non-linear ...growth models (Von Bertalanffy, Gompertz, and logistic) to fit the growth curve of Liangshan pigs from an unselected, random-bred pig population and estimate the pigs most suitable slaughter weight. The growth development data at 20 time points of 275 Liangshan pigs (from birth to 250 d) were collected. To analyze the relative gene expression related to development, seven slaughter weight phases (50, 58, 66, 74, 82, 90, and 98 kg) (20 pigs per phase) were examined. We found that the Liangshan pig growth curve fit the typical S-curve well and that their growth turning point was 193.4 days at a weight of 62.5 kg, according to the best fit Von Bertalanffy model based on the goodness of fit criteria. Furthermore, we estimated that the most suitable slaughter weight was 62.5 to 74.9 kg based on the growth curve and the relative expression levels of growth-related genes.
•Aerodynamic field around dry cooling tower is presented with numerical model.•Performances of cooling deltas are figured out by air inflow velocity analysis.•Setting angles of wind-break walls are ...optimized to improve cooling performance.•Optimized walls can reduce the interference on air inflow at low wind speeds.•Optimized walls create stronger outside secondary flow at high wind speeds.
To get larger cooling performance enhancement for natural draft dry cooling tower with vertical cooling deltas under crosswind, setting angles of wind-break walls were optimized. Considering specific structure of each cooling delta, an efficient numerical model was established and validated by some published results. Aerodynamic fields around cooling deltas under various crosswind speeds were presented, and outlet water temperatures of the two columns of cooling delta were exported as well. It was found that for each cooling delta, there was a difference in cooling performance between the two columns, which is closely related to the characteristic of main airflow outside the tower. Using the present model, air inflow deviation angles at cooling deltas’ inlet were calculated, and the effects of air inflow deviation on outlet water temperatures of the two columns for corresponding cooling delta were explained in detail. Subsequently, at cooling deltas’ inlet along radial direction of the tower, setting angles of wind-break walls were optimized equal to air inflow deviation angles when no airflow separation appeared outside the tower, while equal to zero when outside airflow separation occurred. In addition, wind-break walls with optimized setting angles were verified to be extremely effective, compared to the previous radial walls.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•An integrated model is built to quantify spray cooling effects on tower performance.•The model couples droplet evaporation and tower natural draft at different scales.•Spray cooling slightly reduces ...tower ventilation while enhancing its heat transfer.•The caused velocity decrease of inflow air in turn promotes droplet evaporation.•The shrinkage of effective air inlet area of the tower is adverse to spray cooling.
An integrated model with a coupling procedure was developed to combine the dynamics of spray injections and natural draft of the dry cooling tower. By the integrated model, the interaction was clearly revealed that pre-cooling slightly reduces the buoyancy and ventilation of the tower while enhancing heat transfer, but velocity decrease of inflow air in turn promotes droplet evaporation and enhances spray cooling effects. Under an example pre-cooling system, the calculated inflow air temperature drop is about 6.6% larger than that obtained by the traditional model which neglected this interaction. Moreover, spray cooling effects on tower performance were directly quantified by the integrated model, and the tower achieved 6.94% heat dissipation improvement and 2.75% ventilation decrease. According to streamlines, effective air inflow area of the tower gradually shrinks, which promotes the formations of interferences among the injections and severely impedes the evaporation process. Especially near the inlet of the radiator, evaporation rate hardly grows, and it gets worse under the case of more nozzles. The larger droplet size and the lower droplet velocity under a smaller spray pressure are adverse to droplet evaporation, and spray cooling makes little sense at low air temperature and especially high air humidity. The proposed integrated model is a powerful tool for spray cooling research and optimization for the dry cooling tower and some other large-scale objects.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To reduce the adverse effect of crosswind on thermo-flow performance of the natural draft dry cooling tower (NDDCT), a novel type of external flat windbreak walls is introduced. Taking the prevailing ...wind direction as the symmetry axis, windbreak wall arranged at each flank of the tower is divided into three rotatable columns according to the size of the researched NDDCT, with the rotating angle equal to air inflow deviation angle of nearest cooling delta. Subsequently, using the steady model and half tower simulations after comparison, effects of various combinations of the rotatable columns were revealed based on the analysis of velocity and temperature fields in and around the tower. At the general wind speeds, wall form of only middle column rotating contributes the largest performance improvement to the tower, which is over 17% at wind speed of 8 m/s, nearly 2.5% larger than that brought by the traditional radial walls. Meanwhile, it was found that outlet water temperatures of the next three cooling deltas at the back of inner column get increased under the optimal wall form. To overcome this problem, porous walls were tested to be applicable, but without overwhelming superiority, compared to the solid walls. In addition, when crosswind gradually deviates from the specified prevailing wind direction, wall form of only middle column rotating is still superior to the traditional radial walls, especially at a small crosswind deviation angle, but the difference between the benefits brought by the two wall forms to the tower is decreasing.
•Novel windbreak walls are used for efficiency recovery of the NDDCT under wind.•Each proposed wall outside tower flank is divided into three rotatable columns.•Effects of various wall forms are analyzed based on flow and temperature fields.•Wall form of only middle column of the wall rotating is the best choice.•The optimal wall form is still superior when crosswind direction varies.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
During low ambient temperature periods, the huge heat transfer temperature difference would result in an excess cooling capacity of the natural draft dry cooling tower. So low cooling water ...temperature and back pressure can be easily achieved in cold days due to the unavoidable air leakage in practical operation, and the excess cooling capacity is a great threat to the safe operation of the indirect dry cooling system. To cope with that problem, a novel partial through-flow tower shell is proposed. By numerical simulation of the tower, aerodynamic fields in and around the tower were presented, and cooling water temperature drop was exported as well. It was found that thermal performance of the tower would get enhanced by crosswind under the air leakage condition, but that can be counteracted by the proposed partial through-flow tower shell. The through-flow tower shell is effective to reduce air inflow rate and cooling capacity of the tower, and increase back pressure and cooling water temperature after the coupling of the tower and condenser. Compared with the sideward or leeward through-flow tower shell, the windward through-flow tower shell would provide a much larger feasible region for safe operation of the system, and achieve the maximum anti-freezing result at the moderate wind speed. At the fairly high wind speed, the sideward through-flow tower shell would bring the adverse effect, while the other two forms are still active, although their anti-freezing effects degrade a bit in this condition.
•The partial through-flow tower shell is proposed for indirect dry cooling system.•Aerodynamic fields in and around the tower are presented by numerical simulation.•Strong crosswind in cold days is a great threat to safe operation of the system.•The through-flow tower shell is effective to reduce cooling capacity of the tower.•The proposed tower shell would greatly broaden safe operation range of the system.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
