Energy and control performance investigation of air-handling units with return-air bypass

Gang Wang, Xuejing Zheng, Li Song, Esber Andiroglu

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The adoption of energy-efficient standards significantly cut the energy consumption in buildings by reducing envelope heat transfer and internal heat gain. These energy efficiency measures reduce not only the electrical load, but also the cooling load as well as the supply airflow rate. On the other hand, a minimum airflow rate is always required for all building types. As a result, additional reheat is typically required to maintain the minimum airflow set point under partial spacecooling loads for conventional air-handling units (AHUs) and may degrade the effectiveness of energy efficiency measures. The AHUs with return-air bypass (RAB) provides an alternative to reduce additional reheating and overcooling at the minimum airflow rate with good space humidity control. However, because of insufficient performance data, the AHUs with RAB are still notwidely applied. The purpose of this study is to investigate the energy and control performance of the AHUs with RAB under differen to perating conditions through simulations. First, the AHU thermodynamic models and simulation approaches are developed, and then the system performance, including reheating and cooling loads and space humidity, is simulatedon apseudo-AHU. Thesimulation results reveal that the studied AHU with RAB can wellmaintain the desired space humidity without the additional reheating and overcooling as the space cooling load varies from 100% to 15% and space sensible heat ratio varies from 0.9 to 0.7.

Original languageEnglish (US)
Title of host publicationASHRAE Transactions
PublisherAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
Number of pages11
ISBN (Electronic)9781939200778
StatePublished - 2017
Event2017 ASHRAE Annual Conference - Long Beach, United States
Duration: Jun 24 2017Jun 28 2017

Publication series

NameASHRAE Transactions
ISSN (Print)0001-2505


Other2017 ASHRAE Annual Conference
Country/TerritoryUnited States
CityLong Beach

ASJC Scopus subject areas

  • Building and Construction
  • Mechanical Engineering


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