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A new numerical approach for exergy targets and losses determination in sub-ambient processes

Sub-ambient processes such as a refrigeration system are a highly energy intensive area in chemical industries. Refrigeration systems require a high level of process cooling using a combination of compression and expansion operations. It is, therefore, crucial to optimise heat transfer between the u...

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Main Authors: Hamsani, M. N., Liew, P. Y., Walmsley, T. G.
Format: Article
Published: Italian Association of Chemical Engineering - AIDIC 2017
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TP Chemical technology
Online Access:http://eprints.utm.my/id/eprint/75601/
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030790229&doi=10.3303%2fCET1761202&partnerID=40&md5=045700c5c119629b36de88cbd58ba2bd
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spelling my.utm.756012018-04-27T01:33:18Z http://eprints.utm.my/id/eprint/75601/ A new numerical approach for exergy targets and losses determination in sub-ambient processes Hamsani, M. N. Liew, P. Y. Walmsley, T. G. TP Chemical technology Sub-ambient processes such as a refrigeration system are a highly energy intensive area in chemical industries. Refrigeration systems require a high level of process cooling using a combination of compression and expansion operations. It is, therefore, crucial to optimise heat transfer between the utility system and the process streams including the placement of compression and expansion operations to minimise the exergy losses and work as much as possible. This paper demonstrates how heat integration tools such as Pinch Analysis and Exergy Analysis can be applied to determine exergy losses and exergy targets for sub-ambient processes. In this study, a numerical approach, the Exergy Problem Table Algorithm (Ex-PTA), is proposed as an improved method compared to the graphical method based on the Extended Pinch Analysis and Design (ExPAnD) methodology. The methodology is applied to a literature case study of a refrigeration system to prove its validity. For the new numerical method, the minimum exergy requirement above the Exergy Pinch is 2.67 kW, while the maximum exergy rejection below the Exergy Pinch is 1.33 kW. The result shows that the total exergy loss for the process is 4.74 kW. In contrast, the maximum exergy rejection and minimum exergy requirement obtained in ExPAnD are 0.46 kW and 5.38 kW while the total exergy loss is 6.72 kW. These new targets assume so-called horizontal heat transfer is allowed between process and utility streams, whereas the ExPAnD method assumes vertical heat transfer between process and utility and, therefore, results in less optimistic targets. Italian Association of Chemical Engineering - AIDIC 2017 Article PeerReviewed Hamsani, M. N. and Liew, P. Y. and Walmsley, T. G. (2017) A new numerical approach for exergy targets and losses determination in sub-ambient processes. Chemical Engineering Transactions, 61 . pp. 1225-1230. ISSN 2283-9216 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030790229&doi=10.3303%2fCET1761202&partnerID=40&md5=045700c5c119629b36de88cbd58ba2bd
institution Universiti Teknologi Malaysia
building UTM Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Malaysia
content_source UTM Institutional Repository
url_provider http://eprints.utm.my/
topic TP Chemical technology
spellingShingle TP Chemical technology
Hamsani, M. N.
Liew, P. Y.
Walmsley, T. G.
A new numerical approach for exergy targets and losses determination in sub-ambient processes
description Sub-ambient processes such as a refrigeration system are a highly energy intensive area in chemical industries. Refrigeration systems require a high level of process cooling using a combination of compression and expansion operations. It is, therefore, crucial to optimise heat transfer between the utility system and the process streams including the placement of compression and expansion operations to minimise the exergy losses and work as much as possible. This paper demonstrates how heat integration tools such as Pinch Analysis and Exergy Analysis can be applied to determine exergy losses and exergy targets for sub-ambient processes. In this study, a numerical approach, the Exergy Problem Table Algorithm (Ex-PTA), is proposed as an improved method compared to the graphical method based on the Extended Pinch Analysis and Design (ExPAnD) methodology. The methodology is applied to a literature case study of a refrigeration system to prove its validity. For the new numerical method, the minimum exergy requirement above the Exergy Pinch is 2.67 kW, while the maximum exergy rejection below the Exergy Pinch is 1.33 kW. The result shows that the total exergy loss for the process is 4.74 kW. In contrast, the maximum exergy rejection and minimum exergy requirement obtained in ExPAnD are 0.46 kW and 5.38 kW while the total exergy loss is 6.72 kW. These new targets assume so-called horizontal heat transfer is allowed between process and utility streams, whereas the ExPAnD method assumes vertical heat transfer between process and utility and, therefore, results in less optimistic targets.
format Article
author Hamsani, M. N.
Liew, P. Y.
Walmsley, T. G.
author_facet Hamsani, M. N.
Liew, P. Y.
Walmsley, T. G.
author_sort Hamsani, M. N.
title A new numerical approach for exergy targets and losses determination in sub-ambient processes
title_short A new numerical approach for exergy targets and losses determination in sub-ambient processes
title_full A new numerical approach for exergy targets and losses determination in sub-ambient processes
title_fullStr A new numerical approach for exergy targets and losses determination in sub-ambient processes
title_full_unstemmed A new numerical approach for exergy targets and losses determination in sub-ambient processes
title_sort new numerical approach for exergy targets and losses determination in sub-ambient processes
publisher Italian Association of Chemical Engineering - AIDIC
publishDate 2017
url http://eprints.utm.my/id/eprint/75601/
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030790229&doi=10.3303%2fCET1761202&partnerID=40&md5=045700c5c119629b36de88cbd58ba2bd
_version_ 1643657107910688768
score 13.211869

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