Heat Transfer and Exergy Analysis of a Spiral Heat Exchanger

• Published in: Heat transfer engineering Vol. 37; no. 12; pp. 1013 - 1026
• Main Authors: Nguyen, Duc-Khuyen, San, Jung-Yang
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 12.08.2016; Taylor & Francis Ltd
• Subjects: Economic conditions; Exergy; Heat exchangers; Heat transfer; Optimization; Power consumption; Spirals; Walls
• ISSN: 0145-7632; 1521-0537
• DOI: 10.1080/01457632.2015.1104159

The heat transfer effectiveness of a countercurrent spiral heat exchanger is expressed as a function of number of transfer units, ratio of flow capacity rates, number of spiral turns, and dimensionless start-point angle of spiral (dimensionless angular angle of the start point of a spiral curve constituting the solid wall of the heat exchanger). The heat transfer effectiveness is weakly dependent on the dimensionless start-point angle of spiral, but moderately increases with the number of spiral turns. As the number of spiral turns is larger than 20, the heat transfer effectiveness of the spiral heat exchanger approaches that of a counterflow heat exchanger. The heat transfer effectiveness of the spiral heat exchanger has a maximum. The optimum number of transfer units at the maximum heat transfer effectiveness increases with the number of spiral turns, whereas it increases with a decrease of the ratio of flow capacity rates. In the second-law analysis, an optimum hot flow-to-cold flow capacity-rate ratio is found. For obtaining a large net recovered exergy rate, the spiral heat exchanger needs to possess a large number of transfer units (greater than 2.0) and operate at a near balanced-flow condition. In addition, a small consumed mechanical power is demanded.