Open Access
Chen, Long
Graduate Program:
Agricultural and Biological Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
March 26, 2019
Committee Members:
  • Eileen Eilzabeth Fabian, Dissertation Advisor
  • Eileen Eilzabeth Fabian, Committee Chair
  • John Michael Cimbala, Committee Member
  • Virendra Puri, Committee Member
  • Paul H Patterson, Outside Member
  • CFD modeling
  • Cage-free egg production
  • Simulation
  • Indoor air quality
  • Animal housing
  • Animal welfare
  • Agricultural and biological engineering
The U.S. poultry industry is the world’s largest producer and second largest exporter of poultry meat, and it is a major egg producer. A shift to cage-free eggs is underway that contributes to the most significant evolution that poultry facilities have been faced with in decades. However, the lack of unified guidelines and various definitions of cage-free housing options have left egg producers with many uncertainties about cage-free housing. This work aims to provide practical recommendations to refining ventilation system design in cage-free hen houses with the goal of assuring bird welfare through comfortable conditions and improving the capacity of containing contaminants, such as a virus. This study uses a well-established engineering computer modeling technique – computational fluid dynamics (CFD) that simulates the flow of air and particles to quantify the effectiveness of ventilation systems in maintaining suitable, uniform living conditions at the bird level and the capacity of containing any contaminant. A commercial software package was used to develop CFD models and implement all simulations. Four three-dimensional CFD models were developed on the basis of a full-scale floor-raised hen house, corresponding to ventilation configurations of the standard top-wall inlet sidewall exhaust (TISE), and three alternatives: mid-wall inlet ceiling exhaust (MICE), mid-wall inlet ridge exhaust (MIRE), and mid-wall inlet attic exhaust (MIAE). In addition, 2,365 birds were individually modeled with simplified shapes. One-eighth of a real commercial hen house was modelled although the reduced size included a representative number of hens, ventilation inlet and fan features and portions of a barn important for hen management, for example nest boxes, feed and water area and litter scratch floors. A surrogate virus contaminant, particles of ammonia, were introduced to the hen house at the upwind ventilation inlets and their dispersion through the house and outdoor environment was simulated. Performance of the standard ventilation configuration and alternative designs were analyzed and evaluated by comparing their simulation outputs at locations represented by cross-sectional planes in the model. The simulated ventilation rate for the hen house in each model was 1.97 m3/s (4174 ft3/min), 1.93 m3/s (4089 ft3/min), 1.96 m3/s (4153 ft3/min), and 1.91 m3/s (4047ft3/min), which all fell in the desired range for cold weather (0oC). Five animal-occupied zones within each of the model planes were evaluated for practical hen comfort attributes, air velocity and temperature, and ventilation performance, static pressure and presence of the contaminant mass fraction. The three alternative models showed comparable performance in maintaining desirable microclimate at the bird level, compared to the standard TISE model. The simulation output of MIRE and MIAE demonstrated both models could provide airflows about 0.35 m/s (69 ft/min) on average at the bird level, which had no statistically significant difference with the standard TISE model. The temperature at the bird level was maintained between 20 and 24oC on average by all models, which was acceptable in the cold weather. The indoor static pressure was stabilized at -25 to -21 Pa, which fell in the normal range for a hen house with the negative-pressure ventilation. Simulation results also revealed three models, TISE, MIRE, and MIAE had indistinguishable performance in containing the contaminant, while the average contaminant level in the model of MICE was discovered 19% lower than the others within the majority of the indoor space. Of interest is that the mid-wall alternative inlet designs in combination with the vertical roof-level exhaust were able to limit most contamination to that half of the hen house were the vector was introduced. Considerable simulation results and subsequent analyses substantially demonstrated these alternative models had the capacity to create satisfactory indoor conditions for the cage-free hen house. In addition, statistical analyses were conducted to confirm the significance of vital factors and verify significant differences for particular comparisons. As a primary goal of conducting this study, practical recommendations are documented based on valuable simulation output, which have been and will continue to be provided to egg producers and poultry house builders. This dissertation demonstrated the CFD modeling was a powerful tool for studying the ventilation system for animal housing. The author hopes the application of CFD modeling will play a pivotal role in addressing practical issues related to indoor air quality of agricultural buildings in the future.