Wise choice of showerheads : understanding the impacts of shower water spray patterns on heat transfer coefficient between water and human skin

Abstract

Heat transfer coefficients between shower water and human skin could significantly impact occupants’ thermal sensation and energy consumption during showering. A recently published study found that heat transfer coefficients varied considerably among showerhead patterns. However, no specific effects for overall showerhead patterns were concluded because of the limited characteristic parameters of showerheads. Nonetheless, the impacts of water spray patterns on the heat transfer coefficient between water and flat surface were investigated and identified by several studies on spray cooling. Similar effects were expected for the heat transfer coefficients between shower water and human skin during showering. Hot water showers are the opposite process of water spray cooling. This study conducted experiments to quantify the water spray patterns during showering and define their impacts on the heat transfer coefficient. Five showerheads with 18 water spray patterns were tested in this study. These patterns' resistance factor, water supply pressure, and nozzle area ratio were measured to qualify their shower performance. Each pattern was tested under six showering conditions (two water flow rates × three water temperatures), and the heat transfer coefficient of each condition was calculated using the method proposed by a previous study. Results indicated that the heat transfer coefficient was significantly correlated with the resistance factor (r=0.331, p<0.001), water supply pressure (r=0.271, p=0.006), and nozzle area ratio (r=0.283, p=0.004) of the water spray patterns in general. Although these correlations were not always significant if examining the showerhead individually, clear trends still can be observed. The influence of water spray patterns on the heat transfer coefficient could provide residents with scientific references when selecting showerheads in their bathrooms.