@article {30300, title = {A Comparative Study on Energy Performance of Variable Refrigerant Flow Systems and Variable Air Volume Systems in Office Buildings}, journal = {Applied Energy}, year = {2016}, abstract = {

Variable air volume (VAV) systems and variable refrigerant flow (VRF) systems are popularly used in office buildings. This study investigated VAV and VRF systems in five typical office buildings in China, and compared their air conditioning energy use. Site survey and field measurements were conducted to collect data of building characteristics and operation. Measured cooling electricity use was collected from sub-metering in the five buildings. The sub-metering data, normalized by climate and operating hours, show that VRF systems consumed much less air conditioning energy by up to 70\% than VAV systems. This is mainly due to the different operation modes of both system types leading to much fewer operating hours of the VRF systems. Building simulation was used to quantify the impact of operation modes of VRF and VAV systems on cooling loads using a prototype office building in China. Simulated results show the VRF operation mode leads to much less cooling loads than the VAV operation mode, by 42\% in Hong Kong and 53\% in Qingdao. The VRF systems operated in the part-time-part-space mode enabling occupants to turn on air-conditioning only when needed and when spaces were occupied, while the VAV systems operated in the full-time-full-space mode limiting occupants{\textquoteright} control of operation. The findings provide insights into VRF systems operation and controls as well as its energy performance, which can inform HVAC designers on system selection and building operators or facility managers on improving VRF system operations.\  \ \ 


}, keywords = {building simulation, comparative analysis, energy performance, field measurement, Variable Air Volume (VAV) Systems, Variable Refrigerant Flow (VRF) Systems}, author = {Xinqiao Yu and Da Yan and Kaiyu Sun and Tianzhen Hong and Dandan Zhu} } @article {56246, title = {Building energy modeling programs comparison Research on HVAC systems simulation part}, year = {2013}, abstract = {

Building energy simulation programs are effective tools for the evaluation of building energy saving and optimization of design. The fact that large discrepancies exist in simulated results when different BEMPs are used to model the same building has caused wide concern. Urgent research is needed to identify the main elements that contribute towards the simulation results. This technical report summarizes methodologies, processes, and the main assumptions of three building energy modeling programs (BEMPs) for HVAC calculations: EnergyPlus, DeST, and DOE-2.1E, and test cases are designed to analyze the calculation process in detail. This will help users to get a better understanding of BEMPs and the research methodology of building simulation. This will also help build a foundation for building energy code development and energy labeling programs.

}, keywords = {Building energy modeling programs, comparison tests, HVAC system simulation, theory analysis}, author = {Xin Zhou and Da Yan and Tianzhen Hong and Dandan Zhu} } @article {56245, title = {A Detailed Loads Comparison of Three Building Energy Modeling Programs: EnergyPlus, DeST and DOE-2.1E}, journal = {Building Simulation}, volume = {6}, year = {2013}, month = {09/2013}, pages = {323-335}, publisher = {Tsinghua University Press}, chapter = {323}, abstract = {

Building energy simulation is widely used to help design energy efficient building envelopes and HVAC systems, develop and demonstrate compliance of building energy codes, and implement building energy rating programs. However, large discrepancies exist between simulation results from different building energy modeling programs (BEMPs). This leads many users and stakeholders to lack confidence in the results from BEMPs and building simulation methods. This paper compared the building thermal load modeling capabilities and simulation results of three BEMPs: EnergyPlus, DeST and DOE-2.1E. Test cases, based upon the ASHRAE Standard 140 tests, were designed to isolate and evaluate the key influencing factors responsible for the discrepancies in results between EnergyPlus and DeST. This included the load algorithms and some of the default input parameters. It was concluded that there is little difference between the results from EnergyPlus and DeST if the input values are the same or equivalent despite there being many discrepancies between the heat balance algorithms. DOE-2.1E can produce large errors for cases when adjacent zones have very different conditions, or if a zone is conditioned part-time while adjacent zones are unconditioned. This was due to the lack of a strict zonal heat balance routine in DOE-2.1E, and the steady state handling of heat flow through interior walls and partitions. This comparison study did not produce another test suite, but rather a methodology to design tests that can be used to identify and isolate key influencing factors that drive the building thermal loads, and a process with which to carry them out.

}, keywords = {building energy modeling program, building thermal loads, comparison, dest, DOE-2.1E, energyplus}, issn = {Print: 1996-3599; Online 1996-8744}, doi = {10.1007/s12273-013-0126-7}, author = {Dandan Zhu and Tianzhen Hong and Da Yan and Chuang Wang} } @conference {2673, title = {Comparative research in building energy modeling programs}, booktitle = {China Annual HVACR Conference}, year = {2012}, month = {06/2011}, address = {China (in Chinese)}, keywords = {advanced building software: energyplus, building energy modeling program, building simulation, comparison, dest, doe-2, energyplus, simulation research group, test}, author = {Dandan Zhu and Tianzhen Hong and Da Yan and Chuang Wang} } @article {3445, title = {Comparison of Building Energy Modeling Programs: Building Loads}, year = {2012}, month = {06/2012}, author = {Dandan Zhu and Tianzhen Hong and Chuang Wang} } @conference {3404, title = {A Comparison of DeST and EnergyPlus}, booktitle = {China HVAC Simulation Conference}, year = {2011}, month = {2011}, address = {Beijing}, keywords = {building simulation, comparison, dest, energy modeling, energyplus, simulation research, simulation research group, test cases}, author = {Dandan Zhu and Chuang Wang and Da Yan and Tianzhen Hong} }