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Corresponding Author

El-Ehwany, A.

Subject Area

Mechanical Power Engineering

Article Type

Original Study

Abstract

In this work, the elbow bend heat exchangers were suggested to be used as a heater and a cooler in an alpha type Stirling engine. Elbow bend heat exchanger is a bank of tubes arranged in a quadrant either in line or staggered with different normal and parallel pitches. Eight of the suggested heat exchangers of different dimensions were tested experimentally for steady flow (in a previous research by the same authors). The experimental results were correlated for heat transfer and pressure drop. In the present research, two parallel pistons on a common crankshaft alpha Stirling engine were designed to use elbow bend heat exchangers as a heater and a cooler. The heating fluid flows inside the tubes of the heater, the coolant flows inside the cooler tubes, while the gas circuit fluid (working fluid) flows past the tubes in both of them. A computer program was prepared to analyze the working fluid cycle in the vision of Schmidt theory and it was solved numerically by the program. After that the effect of heat transfer and pressure drop were taken into consideration. Upon calculations, the most suitable values of each of the stroke/bore ratio, the crank phase angle between the hot and cold pistons and the speed range were found out for nitrogen as a working fluid. In a comparison between the proposed engine and practical ones by the literature, it was found that the proposed engine delivers higher power per unit swept volume per unit temperature difference between the heat source and sink in addition to higher values of the efficiency.

Keywords

Stirling engines; Elbow bend heat exchangers; Alpha Stirling engine

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