Supplementary data

Extended surfaces are commonly used to improve heat transfer in shell and tube heat exchangers, increasing manufacturing complicacy and material cost, especially for smaller units. These issues are attempted in the present study through dimensional variations of the tube. Seven model configurations are selected including common straight tubes and each is divided into three zones based on diameter. Both water temperatures and flow directions are also varied for each configuration resulting in 168 combinations. Hot water (30-100℃) flows through the tube and cold air at room temperature flows over the tube. It was observed that heat exchange is much higher compared to straight flow tubes when the hot fluid flows through a narrow neck located at the mid-zone. Comparatively, heat transfer increased by 14.41%, 26.34% and 40.34% during laminar, transition and turbulent conditions respectively. Heat gain by air is much higher during transition flow through tube, regardless of configuration.