Simplified Modelling of Displacement Ventilation
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Displacement Ventilation in Action: Performance Monitoring of Demonstration Classrooms
Displacement Ventilation in Action: Performance Monitoring of Demonstration Classrooms Charles Eley and John Arent, Architectural Energy Corporation Bradley Meister, California Energy Commission ABSTRACT Displacement ventilation (DV) can provide better acoustics, improved indoor air quality, and reduced energy use for schools and other buildings. Recent research has used CFD simulation to determine supply air requirements and predict thermal comfort. However, there is a scarcity of performance data from these systems in practice. This paper presents recent research results from a Public Interest Energy Research (PIER) funded study of the technology and its application to K-12 schools. Two demonstration classrooms were continuously monitored over a six-month period to evaluate DV’s impact on thermal comfort, indoor air quality and energy use. Each of the displacement ventilation classrooms was compared to a control classroom that used a conventional packaged rooftop unit and overhead mixing air distribution. The demonstration and control classrooms were instrumented to record room temperature, carbon dioxide concentrations, relative humidity levels, and HVAC system electricity use. Temperatures were recorded at four different heights for each of three different locations to verify that thermal stratification in the space conforms to ASHRAE standards for thermal comfort. The monitoring data shows a consistent pattern of thermal stratification in the displacement classrooms. The displacement classrooms also have a lower CO2 concentration in the occupied zone than at the ceiling return, a sign of good ventilation effectiveness. Feedback from teacher surveys of thermal comfort, indoor air quality and acoustics is testament to the benefits of displacement ventilation. The results of the demonstration classrooms will help bridge the gap between theory and practice and will be a catalyst for market adoption. -
A Model for an Under Floor Air Distribution System
Energy and Buildings 37 (2005) 399–409 www.elsevier.com/locate/enbuild A model for an under floor air distribution system Y.J.P. Lina,*, P.F. Lindenb aEnergy and Resources Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan bDepartment of Mechanical and Aerospace Engineering, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0411, USA Received 15 April 2004; received in revised form 30 July 2004; accepted 31 July 2004 Abstract We present a simplified model of an underfloor air distribution (UFAD) system consisting of a single source of heat and a single cooling diffuser in a ventilated space. Laboratory experiments were carried out to simulate the flow and a model for the flow in this space is proposed. The model is based on plume theory for the heat source and a fountain model for the diffuser flow, and predicts a steady-state two-layer stratification in the room. The governing parameters are shown to be the buoyancy flux of the heat source, and the volume and momentum fluxes of the cooling diffuser. The results suggest ways to optimize UFAD design and operation. # 2004 Elsevier B.V. All rights reserved. Keywords: UFAD system; Penetrative entrainment; Turbulent plume; Turbulent fountain; Displacement ventilation; Mixing ventilation 1. Introduction Bauman and Webster [2] show that well-designed UFAD systems can provide such benefits as: The motivation for this study is to understand and model the behavior of an under floor air distribution system reduced life cycle building costs; (hereafter referred to as UFAD) in a ventilated room. This improved thermal comfort; system was first introduced in the 1950s to cool a computer improved ventilation efficiency and indoor air quality; room and is emerging as a leading ventilation system design reduced energy use; in modern commercial buildings. -
Dwelling on Courtyards
18 2014 Dwelling on Courtyards Exploring the energy efficiency and comfort potential of courtyards for dwellings in the Netherlands Mohammad Taleghani Dwelling on Courtyards Exploring the energy efficiency and comfort potential of courtyards for dwellings in the Netherlands Mohammad Taleghani Delft University of Technology, Faculty of Architecture and the Built Environment, Department of Architectural Engineering + Technology i i Dwelling on Courtyards Exploring the energy efficiency and comfort potential of courtyards for dwellings in the Netherlands Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof.ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op 3 december 2014 om 12.30 uur door Mohammad TALEGHANI Master of Science in Architecture Engineering University of Tehran, Tehran, Iran geboren te Shahrood, Iran i Dit proefschrift is goedgekeurd door de promotor: Prof.dr.ir. A.A.J.F. van den Dobbelsteen Copromotor Dr.ir. M.J. Tenpierik Samenstelling promotiecommissie: Rector Magnificus, voorzitter Prof.dr.ir. A.A.J.F. van den Dobbelsteen, Technische Universiteit Delft, promotor Dr.ir. M.J. Tenpierik, Technische Universiteit Delft, copromotor Prof. Dr. D.J. Sailor, Portland State University, USA Prof. Dr. K. Steemers, MPhil PhD RIBA University of Cambridge, UK Prof.dr.ir. L. Schrijver, University of Antwerp, Belgium Prof.dr.ir. B.J.E. Blocken, Technische Universiteit Eindhoven Prof.dr.ir. P.M. Bluyssen, Technische Universiteit -
Theoretical and Experimental Study of Combined System: Chilled Ceiling and Displacement Ventilation
Universal Journal of Mechanical Engineering 7(3): 118-138, 2019 http://www.hrpub.org DOI: 10.13189/ujme.2019.070305 Theoretical and Experimental Study of Combined System: Chilled Ceiling and Displacement Ventilation Israa Ali AbdulGhafor1,*, Adnan A. Abdulrasool2, Qasim S. Mehdi2 1Lecturer, Department of Electronic Technique, Middle Technical University, Iraq 2Professor, Department of Mechanical Engineering, Al-Mustansiriya University, Iraq Copyright©2019 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract The present experimental study presents the obtain with using HVAC systems that supply enough of performance of the combine cooling system (chilled quantity of fresh air to the occupied zone whilst effectively ceiling and displacement ventilation). The experimental elimination contaminants. So, HVAC, systems provide study included the effect of different temperatures of suitable air temperature by elimination heat from occupied chilled ceiling of (20 and 16)°C and different supplied air zone while avoid large air temperature gradients and drafts. temperatures of (18, 20, 22 and 24)°C with constant Economic side should be achieved by both thermal and internal load of 1600W and constant supplied air velocity indoor air quality requirements, because the largest energy of 0.75m/s. The theoretical study content studying the air consumption is done by these systems. According to recent flow pattern through occupant zone and temperatures researches more than 40% of total energy used by contours in different directions X, Y and Z at supplied air commercial building is consumption by HAVC systems temperature (18)°C and internal load, mean plate [1]. -
Underfloor Air Distribution (UFAD)
Underfloor Air Distribution Underfloor Air Distribution Introduction Underfloor Air Distribution (UFAD) is an alternative to traditional overhead air distribution that delivers air from a pressurized air plenum beneath a raised access floor, relying on the natural buoyancy of air to remove heat and contaminants. Price offers both UFAD Mixing Systems turbulent flow (mixing) and 63-65°F supply air 55°F supply air displacement flow Mixes the “occupied Mixes the entire space underfloor diffusers zone” only Stratified temperature Uniform temperature and Turbulent Flow and contaminant levels contaminant levels Displacement Flow What is stratification? Stratification refers to a non-uniform temperature throughout a zone, with higher temperatures towards the ceiling and lower temperatures towards the floor. In a stratified room, return air is warmer and has a higher level of contaminants than supply air does. What is the occupied zone? Displacement diffusers result in more The occupied zone refers to the space in a room that begins one pronounced stratification and lower velocity profiles in the room, often foot from all walls and extends from the floor to six feet above the leading to improved indoor air quality floor. Mixing the occupied zone instead of the whole space can and thermal comfort. result in energy savings in spaces with high ceilings. 2 priceindustries.com Advantages Flexibility Diffusers installed in a raised floor can be reconfigured at a fraction of the time and cost of an overhead system. Given the prevalence of churn in a modern office environment, a highly configurable HVAC system can be a great cost savings in these environments. -
Displacement Ventilation Provides Cornerstone of Hospital Design
ASHRAE TECHNOLOGY AWARD CASE STUDIES 2020 ©ASHRAE www.ashrae.org. Used with permission from ASHRAE Journal at https://www.mazzetti.com. This article may not be copied nor distributed in either paper or digital form without ASHRAE’s permission. For more information about ASHRAE, visit www.ashrae.org. Displacement Ventilation Provides Cornerstone of Hospital Design The project uses displacement ventilation in the structural columns in the lobby, patient rooms and the intensive care unit. BY BRIAN HANS, P.E.; JOHN PAPPAS, P.E., MEMBER ASHRAE 38 ASHRAE JOURNAL ashrae.org OCTOBER 2020 HONORABLE MENTION | 2020 ASHRAE TECHNOLOGY AWARD CASE STUDIES Displacement ventilation was incorporated into the lobby’s structural columns to seam- lessly integrate the mechanical systems and T he overarching goal for the Lucile provide efficient air distribution, reducing energy consumption and improving Packard Children’s Hospital (Packard occupant comfort. Children’s) was to create an environment that aids healing by providing children and expectant mothers and their visi- tors warm, comfortable, light-filled and uplifting spaces, creating a “home away from home.” The project embodies inno- vation and a true commitment to envi- ronmental sustainability. Displacement ventilation was a cornerstone system decision to achieving the project’s energy- efficiency goals. The new 521,000 net square feet (48 402 square meter) building sits atop a 192,000 square foot (17 837 square meter) garage, more than doubling the size of the exist- ing pediatric and obstetrics hospital campus. The new building adds 149 patient beds for a total of 364 patient beds on the Palo Alto campus. It includes four floors con- sisting of two wings of ICU and acute care unit patient care beds, 12 operating/interventional radiology rooms, a full imaging area that includes MRI, CT and PET/CT, a grand light-filled lobby, public areas, and 3.5 acres (1.4 ha) of green space with gardens and artwork for patients, family and staff. -
Thermal Displacement Ventilation (TDV) in Schools: Improving Indoor Air Quality and Saving Energy
Thermal Displacement Ventilation (TDV) in Schools: Improving Indoor Air Quality and Saving Energy Andrey Livchak, Halton Company Charles Eley, Architectural Energy Corporation Zeqiang Sun, Halton Company John Arent, Architectural Energy Corporation Vern Smith, Architectural Energy Corporation ABSTRACT Thermal displacement ventilation (TDV) is a promising technology for schools and other buildings. The potential energy efficiency, health, and acoustic benefits offer promise as California and other states prepare to spend billions on new schools and major modernization. This paper presents some results from a PIER-funded study of the technology evaluated with computational fluid dynamics and full-scale model testing. In 1995, the Government Accounting Office concluded that 25% of the nation’s schools are plagued by indoor air quality (IAQ) problems. A few years later the Environmental Protection Agency (Johnston & Davis 2001) reported an even higher percentage of schools having IAQ problems. Most of these IAQ problems can be attributed to poor ventilation. TDV, which has been used since the late 1980s in Northern Europe and only more recently in U.S. schools (Turner 1999; Holland & Livchak 2002), disproves the common perception that improving IAQ in an air-conditioned space must result in higher energy consumption. What Is It? Most classroom air conditioning systems use overhead mixing ventilation to deliver cool air (about 55ºF) at the ceiling level. Air is supplied at a high velocity to provide efficient mixing of supply air with room air, to provide uniform temperature throughout the space, and to dilute contaminants with fresh supply air. This system of ventilation has several drawbacks: it can circulate germs, promoting exposure to illness, and it can be noisy and/or drafty – the high-speed air can whistle as it leaves the diffuser, creating possible drafts and making it harder for the students to hear the teacher. -
Estimating Performance of Thermal Displacement Hvac Systems Using Heat Balance-Based Simulation Programs
Eighth International IBPSA Conference Eindhoven, Netherlands August 11-14, 2003 ESTIMATING PERFORMANCE OF THERMAL DISPLACEMENT HVAC SYSTEMS USING HEAT BALANCE-BASED SIMULATION PROGRAMS Thomas A. Lunneberg, P.E. CTG Energetics, Inc. Irvine, California 92618 United States of America ABSTRACT The use of thermal displacement systems in the This paper will address the shortcomings of typical United States, however, is still in its infancy. Driven heat balance-based HVAC design and analysis in large part by increasing emphasis on sustainable software when applied to thermal displacement design practices and an impetus to provide healthier ventilation (TDV) system design. The performance indoor environments, many owners and developers characteristics of thermal displacement systems that are asking their engineers to design TDV systems for lead to inaccurate calculations from heat balance- their new buildings. Unfortunately, many U.S. based programs are discussed. Finally, the paper engineers and architects have little experience with presents an approach for estimating the performance the design and analysis of thermal displacement of TDV systems using existing heat-based calculation systems. As a result, many approach this task from tools that responds to most of the significant an incorrect perspective – namely, that the thermal differences between overhead mixing systems and behavior of a displacement system is similar to that thermal displacement systems. of a traditional overhead “mixing” system. The result is that poorly designed systems are being INTRODUCTION introduced into the marketplace. Such systems tend Thermal displacement ventilation (TDV) systems – to deliver too much supply air, do not adequately essentially, HVAC air distribution systems that address dehumidification needs, and frequently have supply conditioned air at or near the floor and extract overly complex control systems. -
The Meteorological Observations in Coimbra and the Portuguese Participation in Weather Forecast in Europe
THE METEOROLOGICAL OBSERVATIONS IN COIMBRA AND THE PORTUGUESE PARTICIPATION IN WEATHER FORECAST IN EUROPE ANTÓNIO JOSÉ F. LEONARDO, DÉCIO R. MARTINS, AND CARLOS FIOLHAIS Department of Physics and Centre of Computational Physics Faculty of Sciences and Technology of the University of Coimbra 3004–516 Coimbra, Portugal [email protected] ABSTRACT In the early nineteenth century, regular meteorological observations started at the Faculty of Natural Philosophy of the University of Coimbra (FPUC). From 1854 to 1856 these observations were published in O Instituto , a journal of an academic society of the same name, founded in Coimbra in 1852. This new area of science aroused great interest, offering itself as unexplored territory waiting for scientific investigation. In reaction to the pioneering work at the Polytechnic School of Lisbon of Guilherme Pegado, who founded the first meteorological observatory in Portugal in 1854, the FPUC established a Earth Sciences History Meteorological and Magnetic Observatory in Coimbra. The main actor was, from 1863, the physicist Jacinto António de Sousa. In the twentieth century, the increasing need for weather forecasting, especially at sea, led to the creation of the Meteorological Services of the Navy in which Carvalho Brandão played a pivotal role. It was the beginning of an international cooperation that brought Jacob Bjerknes to Portugal. He addressed a conference at Coimbra recommending the creation of a meteorological station in the Azores, to relay observational data from vessels travelling in the Atlantic. The Portuguese meteorological services were scattered in various institutions until 1946, when the National Meteorological Services (NMS) were created. Based on articles published in O Instituto and on the activities of the academy with the same name, we provide an overview of the evolution of meteorology in Portugal until the establishment of the NMS, with particular emphasis on the work of the Meteorological and Magnetic Observatory at the University of Coimbra. -
The Fluid Mechanics of Natural Ventilation-Displacement Ventilation by Buoyancy-Driven Flows Assisted by Wind G.R
AIVC 12,435 PERGAMON Building and Em·ironment 34 ( 1999) 707-710 -- The fluid mechanics of natural ventilation-displacement ventilation by buoyancy-driven flows assisted by wind G.R. Hunt*, P.F. Linden Depanme111 oj Applied .Hatlil'111a1ics Theol'<'li('llf Phi-sics. L"11ireni1r(}(Camhridge. Silrer Street. Ca111hriclg<'. CBJ 9EW. L'.K. mu/ Abstract This paper describes the fluid mechanics of natural ventilation by the combined effects of buoyancy and wind. Attention is restricted to transient draining flows in a space containing buoyant fluid. when the wind and buoyancy forces rei11/(Jrc<' one another. The flows have been studied theoretically and the results compared with small-scale laboratory experiments. Connections between the enclosure and the surrounding fluid are with high-level and low-level openings on both windward and leeward faces. Dense fluid enters through \\indward openings at low levt:ls and displaces the lighter fluid within the enclosure through high-level. leeward openings. A strong. stable stratification develops in this case and a displacement flow is maintained for a range of Froude numbers. The rate at which the enclosure drains increases as the wind-induced pressure drop between the inlet and outlet is increased and as the density difference between the exterior and interior environment is increased. A major result of this work is the identification of the form of the nonlinear relationship between the buoyancy and wind effects. It is shown that there is a Pythagorean relationship between the combined buoyancy and wind-driven velocity and the velocities which are produced by buoyancy and wind forces acting in isolation. -
Displacement Ventilation
Displacement Ventilation Risto Kosonen (ed.) Arsen Melikov Elisabeth Mundt Panu Mustakallio Peter V. Nielsen rehva Federation of European Heating, Ventilation and Air Conditioning Associations GUIDEBOOK NO 23 Single user license only, copying and networking prohibited. All rights reserved by REHVA. Single user license only, copying and networking prohibited. All rights reserved by REHVA. REHVA Displacement Ventilation Risto Kosonen (ed.) Arsen Melikov Elisabeth Mundt Panu Mustakallio Peter V. Nielsen Single user license only, copying and networking prohibited. All rights reserved by REHVA. DISCLAIMER This Guidebook is the result of the efforts of REHVA volunteers. It has been written with care, using the best available information and the soundest judgment possible. REHVA and its volunteers, who contributed to this Guidebook, make no representation or warranty, expressed or implied, concerning the completeness, accuracy, or applicability of the infor- mation contained in the Guidebook. No liability of any kind shall be assumed by REHVA or the authors of this Guidebook as a result of reliance on any information contained in this document. The user shall assume the entire risk of the use of any and all information in this Guidebook. ----------------------------------------------------------------------------------------------------------- Copyright © 2017 by REHVA REHVA is the Federation of European Heating, Ventilation and Air Conditioning Associations, www.rehva.eu All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopies or any other information storage and re- trieval system, without permission in writing from the publisher. Requests for permission to make copies of any part of the work should be addressed to: REHVA Office, 40 Rue Washington, 1050 Brussels – Belgium e-mail: [email protected] ISBN 978-2-930521-17-6 Printed in Finland, Forssan Kirjapaino Oy, Forssa Single user license only, copying and networking prohibited. -
On the Natural Displacement Ventilation Flow Through a Full Scale Enclosure, Driven by a Source of Buoyancy at Floor Level S
Seventh International IBPSA Conference Rio de Janeiro, Brazil August 13-15, 2001 ON THE NATURAL DISPLACEMENT VENTILATION FLOW THROUGH A FULL SCALE ENCLOSURE, DRIVEN BY A SOURCE OF BUOYANCY AT FLOOR LEVEL S. A. Howell and I. Potts University of Newcastle upon Tyne Newcastle upon Tyne, NE1 7RU, England technique, which uses salt water to generate density ABSTRACT differences and motivate the displacement flow. This paper presents experimental data for the This paper reports independent validation work, temperature stratification established within a where a natural displacement ventilation flow, driven full-scale enclosure, for the natural displacement by a source of buoyancy at floor level, is established ventilation flow driven by a source of buoyancy at within a full-sized enclosure with air as the working floor level within the space with air as the working fluid. This is an extension of previously published fluid. work (Howell and Potts, 1998), where a smaller scale A range of predictive techniques is also enclosure was studied. The current investigation is, investigated for the flow, and for each technique a however, truly representative of the ventilation flows critical comparison with the experimental data is observed in real buildings. presented. It is found that there are differences between It is confirmed that the salt-bath modelling the ventilation flow through the full-scale test room technique and related mathematical model of Linden and that predicted by the simple mathematical et, al. (1990) is not appropriate for the prediction of models for the steady-state case. The causes of the this type of ventilation flow in full-scale buildings.