Bruce I. Nelson, P.E., President of Colmac Coil, presented a technical paper entitled "Designing Air Coolers for Direct Expansion (DX) with Ammonia" at the annual meeting of the International Institute of Ammonia Refrigeration (IIAR). The 1998 IIAR annual meeting was held March 15-18th, 1998, in Colorado Springs, Colorado, USA, at the Broadmoor Hotel. An abstract of Mr. Nelson's paper is included below. A full version is also now available for download in MS Word format (zipped).
1998 IIAR Annual Meeting
Presentation Title: Designing Air Coolers for Direct Expansion (DX) with Ammonia
Author: Bruce I. Nelson, P.E.
President
Colmac Coil Manufacturing
Date: 16 Jan 98
Abstract:
There are several methods of controlling the flow of refrigerant to air coolers: Gravity Flooding, Liquid Overfeed, and Direct Expansion (DX). There is increased interest in using Direct Expansion with ammonia for several reasons. Direct Expansion minimizes system refrigerant charge inventory (an important safety consideration with ammonia), minimizes liquid line sizes, offers good heat transfer efficiencies when designed properly, and regulates refrigerant flow automatically. Even though the thermodynamic and physical properties of ammonia give it good heat transfer characteristics, certain properties limit its effectiveness when used in low temperature DX refrigeration air coolers. Design techniques to mitigate these problems is the subject of this presentation.
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