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Nagoya City University Graduate School
Applying CFD to Increase Air-conditioning System Life Cycle Energy Efficiency


Efficiently using limited energy resources over the long term makes it more important to optimize energy consumption versus simply cutting usage. Dr. Gyuyoung Yoon, Associate Professor at Nagoya City University, has coupled Cradle scSTREAM with an air-conditioning energy management tool to account for the impact of three-dimensional effects on total energy management.

Gyuyoung Yoon (Doctor of Engineering)
Nagoya City University Graduate School
Associate Professor of Design and Architecture

Coupling LCEM Tool with scSTREAM for More Accurate Results

 By coupling the LCEM tool with Cradle’s scSTREAM, users can improve the predictive accuracy for both software. Actual air-conditioning performance will vary depending on room temperature distribution and other environmental factors. However, the LCEM tool only considers one-dimensional conditions and cannot account for the complex temperature distribution within the room. Since the performance of the air-conditioner is highly dependent on the indoor conditions, simulation can be connected to the LCEM tool calculation to realistically represent the indoor temperature condition; this is done by coupling LCEM tool and scSTREAM. LCEM tool intake air conditions can be imported into scSTREAM, which then analyzes indoor room conditions. The results from scSTREAM are converted back to the intake condition for LCEM tool, and the cycle is repeated until the solution converges.


Fig: Conceptual diagram of coupling LCEM tool with scSTREAM
(click to enlarge)

 Before Dr. Yoon started working on the coupling of LCEM tool and scSTREAM, analysts assumed that the temperature of the entire indoor environment could be adjusted to the same temperature all at once. In reality, the temperature cannot be adjusted instantly, and the temperature will vary at different locations inside the room. Seeing this, Dr. Yoon decided to apply simulation to more realistically calculate the room temperature, and couple the simulation to LCEM tool. His investigations included evaluating environmental variations created when the air-conditioner was partially functioning under energy saving measures. He also looked at the variations when the air-conditioning system functioned less regularly. If operating the air-conditioning less regularly did not produce any significant difference in temperature variation, a systematic approach to managing on/off time could offer solutions to today’s growing demand for improved energy efficiency.

 Dr. Yoon started to use scSTREAM in 2006 after he received an inquiry from a design company, asking for suggestions about how to evaluate indoor temperature distribution because one of their clients was interested in this. The company did not know how to analyze this kind of situation. Due to desire to be more energy efficient they knew that they should no longer target to maintain the entire indoor temperature to 26 ºC, but they were concerned about the amount of temperature variation. Fortunately, PC performance had dramatically improved in these days, and 3D simulations had become realistically achievable. When Dr. Yoon received this request he chose scSTREAM to investigate the situation, making full use of its capability to visually represent the simulation results very effectively. He had used scSTREAM to evaluate the airow generated by an approaching train, at the Oebashi Station in Osaka. Dr. Yoon recalls that scSTREAM was extremely useful as it was easy to learn to use the software because just upgraded to a new version with a very user-friendly interface. His students in the laboratory were able to start generating useful results in two weeks. Dr. Yoon says, “it was not only very easy to use, but what was also amazing about scSTREAM was that we were able to master it in far less time compared to other tools.”


Fig: Simulation example of evaluating the effect of energy saving measure for individual air-conditioning system
(click to enlarge)

Further Improvements

 Dr. Yoon appreciates Software Cradle’s fast support service response to inquiries, and says that he is grateful for the speed and quality of the support he received. On the other hand, he notes that new functions should be able to operate on ongoing versions. This wouldn’t be such a problem if only a certain function was involved, but when used with other functions, the whole chain is affected.

 He also notes he would love to have the postprocessor available on laptop PC. Although network edition has not been made portable so far, it would be more effective to show the analysis using postprocessor at meetings since more can be explained in depth compared to showing print-out results. CradleViewer can be used to simply show the results, but it can only show pre-selected images. Dr. Yoon claims that since showing animation is effective when explaining and answering questions, it would be helpful to have the license restriction of just postprocessor removed, if not all.

 Dr. Yoon explains that “there is no point of developing LCEM tool if it’s not widely used in society, and it’s essential to make it accessible and comprehensible in order to spread the awareness.” He now undertakes simulation research using the coupling of LCEM tool and scSTREAM in collaboration with Nagoya University Research Group (organized by Professor Masaya Okumiya and Associate Professor Satoru Iizuka from Nagoya University Graduate School of Environmental Studies). “We hope to customize the coupling of LCEM tool and scSTREAM to make it more useful,” says Dr. Yoon.

 Designing and operating effective air-conditioning system will be inevitable for the field of building and architecture, and it is evident that coupling of LCEM tool and scSTREAM will promote this development further.

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*Contents and specifications of products are as of August 1, 2013 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors.

Institute Details


Nagoya City University
Graduate School of Design and Architecture
Faculty Established 1996
Graduate School Established 2000
Type of University Public
Location of Head Office Mizuho-ku, Nagoya, Aichi, Japan



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