Degree Type

Dissertation

Date of Award

1994

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

First Advisor

Michael Pate

Abstract

For the past five decades, CFCs (chlorofluorocarbons) have been some of the primary working fluids used in vapor-compression refrigeration devices. In recent years, CFCs (such as CFC-12 and CFC-11) have been found to destroy the Earth's protective ozone layer, and current mandates require that all new refrigeration equipment produced after 1996 must use an ozone-safe refrigerant. Currently, HFC-134a is targeted as the replacement for CFC-12, and HCFC-123 is targeted as a near-term replacement for CFC-11. The purpose of the present study was to obtain experimental performance data for the shell-side condensation of HFC-134a and HCFC-123 on enhanced tube surfaces. The data obtained in this study will be used to aid engineers who design shell-and-tube condensers for vapor compression refrigeration systems utilizing HFC-134a and HCFC-123;Shell-side condensation heat transfer data were obtained for refrigerants HFC-134a and HCFC-123. In addition, CFC-12 and CFC-11 data were obtained for comparison purposes. The tube bundles used in this study were constructed from 19.1 mm (0.75 in) o.d. 1024-fpm (26-fpi), 1575-fpm (40-fpi), Turbo C-II, and GEWA SC tubes. The tube bundles tested are 5 columns wide by 5 rows deep and have a staggered tube arrangement with a horizontal pitch of 22.2 mm (0.875 in) and a vertical pitch of 19.1 mm (0.75 in). The data were obtained at a refrigerant saturation temperature of 35°C (95°F) over a bundle heat flux range of 18 000-40 000 W/m[superscript]2 (5700-12 700 Btu/(hr·ft[superscript]2)). Average condensing heat transfer coefficients for the bundle as well as average condensing heat transfer coefficients for the middle tube of each row were calculated;For a given tube geometry, the performance of HFC-134a was generally 20% better than the performance of CFC-12, while the performance of HCFC-123 was generally 20% better than the performance of CFC-11 at low heat fluxes, and 10% better at high heat fluxes. For HFC-134a, the performance of the Turbo-CII was two to three times better than that of the other tube geometries, and 1.25 to 2 times better than the other geometries for HCFC-123.

DOI

https://doi.org/10.31274/rtd-180813-11526

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Joseph B. Huber

Language

en

Proquest ID

AAI9503567

File Format

application/pdf

File Size

214 pages

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