Evaluation of 3D-printed Black Globe Thermometers for Thermal Comfort Assessment in Commercial Livestock and Poultry Operations

Abstract

Black globe thermometers (BGTs) are commonly used to assess animal thermal comfort by combining the effects of air temperature, radiation, and air speed. However, many commercially available BGTs are expensive, which limits their use for some research purposes. This thesis investigates low-cost, 3D-printed BGTs as alternatives to a reference BGT made of copper. Chapter 1 provides a brief review of existing knowledge and identifies the research gap, while Chapter 2 compares five alternative designs against the reference BGT over six months of outdoor data collection. Although mean globe temperatures differed significantly among the designs, all alternative BGTs closely followed the reference temperature trend (R² > 0.90). Among the 3D-printed designs, the best-performing globe achieved an R² of 0.99 and an RMSE of 1.76 °C relative to the reference BGT. Chapter 3 presents the development, calibration, and validation of a baseline computational fluid dynamics (CFD) model of the reference copper BGT. The baseline model was used to simulate alternative designs for two 3D-printing filaments, polylactic acid (PLA) and Ice9 Nylon. The best simulated design for each filament types were printed and tested under field conditions. A 200-mm-diameter PLA BGT demonstrated improved agreement with the reference BGT (R² = 0.99; RMSE = 1.21 °C), outperforming the best 3D-printed design identified in Chapter 2. The reference BGT exhibited the fastest thermal response, with a median first-order time constant (τ) of 14.3 min. The optimized PLA and Ice9 Nylon BGTs had slightly longer response times, with τ values that exceeded the reference by 3.6-3.8 mins. Overall, the results demonstrate that 3D-printed PLA BGTs are sufficiently durable for outdoor use and can provide a low-cost, accurate alternative to commercially available BGTs.