# Linear and vortex flow heat transfer coefficients

## Abstract

"In order to make possible better, more efficient equipment, a higher and higher rate of heat transfer has been the goal of engineers for many years. The need for heat transfer rates never thought of 25 years ago has been brought about by the advent of modern high-performance devices such as nuclear reactors and rocket motors. "A heat release of about 40,000 Btu/hr.cu.ft. is considered good practice in a modern boiler, but in a rocket or a nuclear reactor it may be 1,000,000,000 Btu/hr.cu.ft." This heat must be removed by transfer to a coolant or converted into work or the device will fail since in these devices the heat release is independent of the heat removal rate.

When heat is applied to a container containing a fluid such as water, the fluid adjacent to the surface is heated and then replaced by the colder less dense fluid from the top of the container. In this manner, convection currents are created and heat is transferred to all parts of the fluid. This gravitational effect is called natural convection. If the surface temperature is greater than the saturation temperature of the fluid, bubbles of vapor form, and the convection current, and thereby, the heat transfer rate increases greatly due to the large difference between the density of the vapor and the fluid. This process, when the heating surface is hotter than the saturation temperature but the bulk fluid temperature is less than the saturation temperature, is called subcooled nucleate boiling or local boiling. If the gravitational effect causing natural convection can be increased many times over and combined with the turbulent nature of forced convection, an increase in heat transfer should be realized.

The multiplication of the gravity effect in natural convection can be achieved as done in a centrifuge, by causing the fluid to move in a curved path, thereby creating centripetal acceleration many times greater than gravitational acceleration. The resulting transport of the hot fluid from the heating surface and the replacement by the colder fluid should cause an increase in the heat transfer coefficient.

The curved flow required can be generated by forcing the water to flow in a helical path down a test section from which heat is transferred to the water. Fluid flow with combined axial and tangential components of velocity is termed source vortex or simply vortex flow.

It is the purpose of this investigation (1) to design and build apparatus for the determination of the heat transfer film coefficient when using an induction heater to generate heat in the test section, (2) to check the accuracy of the measurements by determination of the film coefficients for linear flow, the values of which are quite well known and (3) to make preliminary evaluation of the effects of vortex flow on heat transfer"--Introduction, pages 1-2.

Miles, Aaron J.

## Committee Member(s)

Pauls, Franklin B., 1911-1996
Eppelsheimer, Daniel S., 1909-1988
Rankin, Rolfe M., 1892-1974

## Degree Name

M.S. in Nuclear Engineering

## Publisher

Missouri School of Mines and Metallurgy

1959

## Pagination

v, 45 pages

Includes bibliographical references (pages 42-43).

## Document Type

Thesis - Open Access

text

## Language

English

Heat -- Convection, Natural
Heat -- Transmission
Nucleate boiling

T 1228

5928002

## Electronic OCLC #

915951364

http://merlin.lib.umsystem.edu/record=b2610175~S5

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