Technology Review

Status of Enhanced Heat Transfer in Systems With Natural Refrigerants

[+] Author and Article Information
Zahid Ayub

 Isotherm, Inc., 7401 Commercial Blvd. East, Arlington, TX 76001zahid@iso-therm.com

J. Thermal Sci. Eng. Appl 2(4), 044001 (Jan 28, 2011) (6 pages) doi:10.1115/1.4003343 History: Received August 29, 2010; Revised December 05, 2010; Published January 28, 2011; Online January 28, 2011

Global environmental and energy concerns have prompted the heating, ventilating, air-conditioning, and refrigeration industry to revisit the use of natural refrigerants. Nearly all natural refrigerants have superior transport properties as compared with synthetic refrigerants; however, the drawback with natural refrigerants has been their toxicity and flammability with an exception of carbon dioxide. In order to overcome this hurdle, it is essential that enhanced surface methods be developed and introduced to reduce the refrigerant charge in a system. Halocarbon industry has expended enormous amount of time and money in developing the ultrahigh efficiency heat exchangers. This experience and knowledge is available and could be applied in developing the efficient exchangers for natural refrigerant applications. This paper presents an overview of the status of natural refrigerants and the trends in the development of compact and low-charge systems.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Different type of tubes in different sections of a flooded tube bundle

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Figure 2

(a) Nucleate boiling characteristic tube in Section I. (b) Nucleate/convective characteristic tube in Section II. (c) Convective characteristic tube in Section III.

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Figure 3

Low-fin carbon steel tube

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Figure 4

Structured surface carbon steel tube

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Figure 5

Enhanced tube in carbon steel for ammonia DX evaporator

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Figure 6

Low charge flooded evaporator with bouyant beads

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Figure 7

Laser welded cassette

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Figure 8

Experimental and correlated Nu for the three chemical beam epitaxy



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