Heat transfer processes of serpentine tubular heat exchangers
Abstract
The focus of the research described herein was to study the heat transfer behavior of tubular serpentine heat exchangers commonly used in residential non-condensing furnaces. The main task was to develop a computer model of the furnace heat exchanger that accurately simulates furnace performance. The purpose of the model is to provide design engineers a tool that can predict performance trends for given design changes. Many of the relevant heat transport processes found within these heat exchangers are well understood. However, sharp 180 degree bends found in serpentine exchangers (and many heat exchangers used in industry) are not adequately described in the literature. These bends are known to have a significant impact on the performance of the heat exchanger. A critical review of the literature for heat transfer in 180 degree bends is given. While it is found that the literature concerning internal heat transfer within these bends is incomplete for the flow ranges found in furnace designs it is concluded that the knowledge is good enough for engineering estimates. However, there are no studies in the literature describing the heat-transfer for heated U-Bends in cross flow. A novel heat transfer correlation is constructed defining the behavior of both bend geometry and incidence angle. Finally, the heat transfer enhancement options available for serpentine tubular heat exchangers are also reported. The enhancement options described are not of the surface treatment variety often found in the open literature. But these options include tube-flattening, insert devices and tube branches that split the flow into several smaller passages.
Degree
Ph.D.
Advisors
Goldschmidt, Purdue University.
Subject Area
Mechanical engineering
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