Adnan H. Ayub

Different Types of Carbon Steel Enhanced Tubes in Ammonia Flooded Evaporator

This short paper deals with a real-world case study of a large capacity industrial ammonia-flooded evaporator. Ethylene glycol brine was the process fluid to be cooled. Several options were analyzed (e.g., different versions of shell-and-tube and plate-and-frame heat exchangers). Because of mechanical integrity, control issues, and maintenance requirements, the option of choice was a flooded shell-and-tube. A conventional flooded shell-and-tube with plain surface carbon steel tubes would have been too big, resulting in a large space requirement and greater refrigerant charge. Almost every local code requires the careful audit of ammonia inventory in an industrial plant. The goal of the designers, engineers, contractors, and the end users is to reduce the refrigerant charge to a minimum. In view of design and operational constraints, an evaporator was designed, fabricated, and installed that included a tube bundle with various kinds of tubes. Three different types of tubes were used along the height of the tube bundle. Highly efficient, nucleate boiling characteristics doubly-enhanced tubes were used in the lower section, and inside-only enhanced tubes were used in the top section to minimize the adverse effects of vapor blanketing. Tubes in the midsection were doubly-enhanced with a different outside structure than the tubes in the lower section. This resulted in a very efficient evaporator at a minimum refrigerant charge.

A Review of Correlations for Outside Boiling of Ammonia on Single Tube and Bundles

ABSTRACT Shell and tube heat exchangers are widely used for various industrial refrigeration applications. This paper summarizes previous studies performed on single tube and bundles and the correlations thereof developed for ammonia. There are limited studies available on ammonia boiling outside single tube and bundle. The major driving force behind this paper is that an extensive work is currently underway on the subject of direct expansion of ammonia on the outside of a tube bundle by the authors. As of now, there are no such studies available in the open literature. In order to understand the process, it is important to follow up on previous studies on pool and convective boiling on single tubes and bundles with ammonia.

Replacing Two Shell-and-Plate Exchangers With a Single Special Design Shell-and-Tube Ammonia-Flooded Evaporator at a Major Food Plant—A Case Study

Case Studies Editors Note: We at the Journal of Heat Transfer Engineering (HTE) are happy to announce the introduction of a new section entitled “Case Studies.” The first case study was published in vol. 37(3–4) and the second case was published in vol. 37(7–8). This is the third case study in this series. We are asking authors to contribute their practical experiences in the form of real-world case studies. The goal is to disseminate practical information especially to young engineers who are stepping into the real world. The format of such articles will be a full-length paper or a short brief. It does not have to entail a typical research-type paper format with details about measurement accuracies, references, and so on. The article could have a brief introduction with the problem description, remedy, lessons learned, and recommendations. The review process will be simple and less involved than with typical research papers. The goal is not to discredit a person or a company but to share experiences. We all make mistakes; however, we also find solutions, and it is the solution part that is rewarding and should be shared for the betterment of the society. Zahid Ayub HTE Case Studies Editor