Mechanical Engineering ETDs

Publication Date

5-5-1977

Abstract

The heat transfer process for a special class of wick fed grooved heat pipe evaporators was investigated analytically and experimentally. The heat pipes studied had vapor release slots cut through the evaporator wick to enhance removal of the vapor generated in the evaporator. As a result of the slots, the liquid menisci formed between the groove tips and the transport wick rather than at the base of the grooves as normally observed. This type of heat pipe evaporator is referred to as an inverted meniscus design.

A comprehensive survey of the literature was completed to establish the existing state of knowledge on evaporator heat transfer. Emphasis was placed on research relating to the problem of removing the vapor from the evaporator without disturbing the liquid flow in the wick.

Thirty-one variations of the basic design were experimentally evaluated and the results reported. A variety of wick materials were applied to evaporators of various groove densities. Screens from 100 to 1400 mesh of various metals, copper feltmetals and composite wicks were all evaluated. Water was the working fluid in all cases.

Basic heat pipe performance relationships were expanded to include inverted meniscus designs. Predictions of the critical heat rate, temperature difference and the heat transfer coefficient were established for each heat pipe tested. The model predicted the experimental results within 10 percent.

As a result of the analytical and experimental correlation and visual observation, the meniscus position was verified and the mode of heat transfer determined. For the inverted meniscus evaporators investigated, conduction through the heat pipe wall and through a liquid layer with evaporation from the liquid surface was found to be the primary heat transfer mechanism.

The mechanism limiting the critical heat rate was found to be a capillary limit. The ability of the wick to supply sufficient fluid to the evaporator controlled the maximum heat rate. When internal pressure losses equaled the pumping head available, the critical heat rate was achieved. The theoretical model was used to predict the effect of each variable on heat pipe performance. Additionally, the potential of inverted meniscus heat pipes for laser mirror heat removal is discussed.

Degree Name

Mechanical Engineering

Level of Degree

Doctoral

Department Name

Mechanical Engineering

First Committee Member (Chair)

Karl Thomas Feldman Jr.

Second Committee Member

Charles Gilbert Richards

Third Committee Member

Arthur Vincent Houghton III

Fourth Committee Member

L. Schlie

Document Type

Dissertation

Language

English

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