Progress 07/01/23 to 06/30/24
Outputs
Target Audience:We have developed a comprehensive set of course materials for engineering courses at UW-Madison, incorporating new CFD case studies alongside the latest precision air jet cooling designs. This initiative aims to help engineering students understand the technical, environmental, and economic impacts of their design analyses. We made a deliberate effort to include the PPPV system design as one of the senior capstone projects. Additionally, we integrated analytical and computational exercises that highlight the importance of computational simulations and their real-world applications. For dairy farmers, employees, and extension specialists, our team has also maintained a web portal that serves as an updated information resource focused on dairy farm facility design and animal comfort, featuring the latest findings. Additionally, we shared the technical details at the esteemed 2024 Annual International Meeting for the American Society of Agricultural and Biological Engineers (ASABE) in Anaheim, CA. Our presentation was accepted for an oral session at the conference. To reach a broader audience, we are currently working on a manuscript detailing our comprehensive computational work, with plans to submit the findings to a peer-reviewed journal. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Newly recruited students underwent training sessions on machine shop safety and animal handling protocols for this project. They were also instructed in the use of advanced solid modeling and assembly computer-aided design software to create digital twins of the PPPV system. The principal investigators taught them how to perform mesh generation and apply boundary conditions based on the measured data sets. The PIs and the students also visited local dairy farms to prepare air quality measurements and CFD simulations. How have the results been disseminated to communities of interest?The comprehensive computational work was finalized and presented at the annual ASABE international meeting, which is attended by research engineers and students. Additionally, we have reached out to local farmers and extension agents to strategize the further dissemination of the PPPV system to the dairy community in the Midwest region of the United States. What do you plan to do during the next reporting period to accomplish the goals?During the second year, we plan to establish two experimental treatments involving (i) a control pen cooled by natural ventilation and circulation fans located above the stalls and (ii) a test pen in which the PPPV System had been installed. An additional 'buffer' pen located between the control and test pens would house cows not included in the data analyses. This pen would be naturally ventilated (no recirculation fans operating for the duration of the experiment. The pen would clearly demarcate the treatment effects that occurred in the two experimental pens and thus prevent any bleed-over between the two experimental zones. The control pen would be fitted with 2 variable speed fans located above one crossover and angled downward to provide air speeds of 1-2.5 m s-1 in the stalls (measured at 0.5 m above the floor surface in each of the 16 stalls). These fans would be fitted with a direct current drive to allow us to program the revolutions per minute and maintain them at specific values. Based on the results of our observations, the fan speed would be set at 60% to provide the required air speeds. The PPPV pen would be adjacent to the end wall at the northeast corner of the barn. The two treatments would be applied in an alternating sequence: 1) naturally-ventilated and 2) PPPV. Groups of 16 cows confined in each pen (32 cows total at a time) would receive both treatments for 5 consecutive days with a 2-day break between treatments, in a replicated crossover design (10 days of active data collection per group), with the treatments applied concurrently in each pen. The study would be repeated for 8 groups of 16 cows (total 128 cows). To achieve a power of 0.8 or higher, at least 7 groups of cows (for safety we chose 8 groups) would be needed to complete the study in an estimated 8-week time-period.As a proxy for vulnerability to heat stress, cows would be selected based on average daily milk yield ≥34 kg and absence of lameness and disease. Preference would be given to pregnant cows to avoid the Core Body Temperature (CBT) loggers from interfering with breeding and because estrus alters behavior. The animal-based outcome measures would include lying time, daily milk yield, vaginal CBT, rumination, respiration rate and panting. Daily individual milk weights would be obtained from the herd computer system. For all 32 cows being tested at any one time, we would record vaginal CBT 24 h/day at 1-min intervals using data loggers attached to blank CIDRs, along with lying and standing behavior using HOBO Pendant G data loggers. We would automatically record rumination behavior 24 h/day using commercial sensors mounted to both collars and ear tags, the latter of which would also track activity levels and the locations of individual cows within a pen.Using cameras equipped with a wide-angle lens to provide a wide horizontal field of view, we would monitor each cow's preference and behavioral responses because cooling air jets over individual stalls and feeding spaces would likely reduce bunching behavior and potentially increase the time each cow spent reclining in her stall. To evaluate the overall differences among treatments, outcome measures would be averaged over the 5 day/treatment, and each outcome variable would be evaluated using a model with a fixed term for treatment (naturally ventilated vs plenum). With some variation in weather conditions during the summer being expected to occur, the effects of daily ambient conditions (T and RH within the barn and weather conditions outdoors) would be evaluated, and additional models would include fixed terms for treatment, the ambient conditions, and their interaction. All models would include random terms for the treatment period and group of cows.
Impacts
What was accomplished under these goals?
During this period, we have conducted a comprehensive computational simulation for the proposed Positive-Pressure Precision Ventilation (PPPV). This design has emerged as an innovative solution because it overcomes the most prevalent limitations of traditional mechanical ventilation schemes and improves the ventilation efficiency by relying on a centrally located, pressurized plenum and a series of air-jet nozzles to precisely target each cow. Our approach describes a design optimization procedure involving a series of Computational Fluid Dynamics (CFD) simulations to establish ideal design parameters for the system's air-jet nozzles. To assess system performance, these designs were tested according to specified assumptions and scenarios in conjunction with computational case studies. The outcomes demonstrated the efficacy of using straight air-jets emitted through a medium-sized nozzle opening (0.1016m in diameter) to achieve balanced cooling performance and the most efficient operational pressurization level. The case studies showed that PPPV systems could double the cooling efficiency at half the required flow rate employed by traditional systems and demonstrated the system's scalability, uniformity with respect to nozzle exhaust, and resilience when subjected to a drifting ambient air-current of 0.5 m s-1. This study's approach and resultant insights should be considered instrumental when installing a PPPV system and could play a significant role in the evolution of dairy barn design innovations aimed at addressing economic and animal welfare concerns. We have been assessing our air measurements through two approaches: (1) as detailed in the proposal, utilizing gas chromatography, which is our standard method, and (2) employing a portable air analyzer that records gas concentrations along with latitude, longitude, and altitude using a high-precision GPS system. With the second method, we will capture real-time measurements at specific locations and upload the data to a cloud server via the LoRa protocol. We have also tested the use of the portable air analyzer to measure air emissions from livestock facilities, funded separately. Our gas chromatography system is currently operational in the laboratory. During this budget period, we have been preparing to conduct our air measurements, and a PhD student has been trained to carry out the experiments. We have visited the university experimental site at Arlington, Wisconsin. Based on the measured dimensions, we have finalized the computer-aided design for the fan and plenum sections. We are now in the process of constructing and testing the first PPPV section at the machine shop within the BSE department on campus. A series of test runs are currently being conducted. Additionally, we are testing the variable speed fans along with a control unit that monitors microclimate parameters using sensors.
Publications
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2024
Citation:
Karapitiya S, HW Chung, ND Panditharatne, CY Choi (2024) CFD-based System Design and Optimization of a Positive-Pressure Precision Ventilation Design to Mitigate Heat Stress for Dairy Cattle, ASABE Annual International Meeting, Anaheim, California.
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