Date of Award

Summer 1968

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

First Advisor

Bush, John

Second Advisor

Lewis, James L.

Third Advisor

Elkouh, A.

Abstract

Finned-tube heat transfer surfaces with flat tubes and continuous fins are used extensively in gas-liquid heat exchangers. This type of heat exchanger is found in many applications including air conditioning and refrigeration. An important consideration in the design process of these heat exchangers is the fin efficiency of the proposed fins required to provide the necessary heat transfer rate. Designers in the past have used the fin efficiency expression derived for a classical straight rectangular tin in which the resistance to conduction heat transfer in the tin is idealized to be one-dimensional. However, the typical heat exchanger using staggered flat tubes and continuous fins has a two-dimensional temperature distribution in the plane of the fin, and the use of the classical tin efficiency expression as an idealization of the actual case can result in significant error in the prediction of fin efficiency. This study analyzes the effect of the two-dimensional temperature variation in the plane of these fins on the prediction of fin efficiency, using an approximate numerical technique. The results are presented in a form that permits the use of the classical one-dimensional fin efficiency expression to accurately describe the efficiency of the two-dimensional fin by using a corrected tin length parameter which is related to the fin geometry. The corrected fin length was found to be essentially a function "formula", the ratio of tube pitch to tube width, and b/L, the ratio of tube width to fin length. The corrected length can be calculated within 5% by the equation "formula" The ratio of tube thickness to fin length, w/L, was held constant at 0.10.

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