A nodal model for displacement ventilation in commercial buildings

Natalia Lastovets

A nodal model for displacement ventilation in commercial buildings

Julkaisun otsikon käännös: Syrjäytysilmanvaihdon vyöhykemalli liikerakennuksissa

Natalia Lastovets

Energia- ja konetekniikan laitos

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Syrjäytysilmanvaihdon mitoitus perustuu yleensä suunnitellun oleskeluvyöhykkeen lämpötilan hallintaan. Lämpötasapainoon perustuvaa menetelmää käytetään syrjäytysilmanvaihdon suunnittelemassa, kun ylikuumeneminen on ensisijainen sisäilmaongelma. Pystysuuntainen lämpötilagradientti DV-järjestelmissä lasketaan yleensä kiinteäparametrisillä vyöhykemalleilla. Tarkan huonetilan lämpötilakerrostuman määrittäminen on tärkeä syrjäytysilmanvaihdon suunnittelussa, koska se liittyy suoraan tuloilmavirran mitoitukseen. Tämä tutkimus keskittyy lämpötilakerrostumamallinnukseen ja tuloilmavirran suunnitteluun huoneissa, joissa on syrjäytysilmanvaihto. Käytetyt tutkimusmenetelmät ovat fysikaaliset mittaukset ja mallintamismenetelmät. Mittaukset jatkuvuustilan olosuhteissa tyypillisillä konvektiolämpökuormilla, lämpökuormitusyhdistelmillä ja huonekorkeuksilla osoittivat, että suurin osa pystysuorasta lämpötilagradientista tapahtuu huoneen alaosassa. Tutkimus paljasti myös, että yleisesti käytetyt lineaarisen lämpötilakerrostumaan perustuvat mallit eivät pysty arvioimaan tarkasti huoneilman lämpötilagradienttia. Tuloksena oleskeluvyöhykkeen laskettu ilman lämpötila voi poiketa todellisesta lämpötilasta 2-3° C, mikä heikentää lämpöviihtyvyyttä ja johtaa jäähdytysjärjestelmien alimitoitukseen. Kehitetty stationaarisen monivyöhykemalli ottaa huomioon lämpökuormien tyypit ja sijainnit ja pystyy ennustamaan tarkasti lämpötilakerrostuman tiloissa, joissa syrjäytysilmanvaihtoa on käytetty. Käytännön sovelluksissa stationaaritilannetta ei kuitenkaan esiinny ja huoneiden lämpökuormat vaihtelevat merkittävästi käyttöjakson aikana. Lisäksi rakenteiden terminen massa vaikuttaa huoneilman lämpötilaan. Tässä tutkimuksessa esitellään uusi dynaamisen syrjäytysilmanvaihdon laskentamalli, jonka tuloksia verrataan perinteiseen menetelmään muutamassa tyypillisessä sovelluskohteessa. Tutkimuksessa esitetään rakenteiden dynaamisten mallien parametrien kalibrointimenetelmä simulaatio-ohjelmiston IDA-ICE avulla. Dynaamista mallia verrattiin mittaustuloksiin, joissa syrjäytysilmanvaihtoa on käytetty. Dynaaminen syrjäytysilmanvaihdon suunnittelun monivyöhykemalli pystyy ottamaan huomioon rakennuksen termisen massan ja vaihtelevien sisäisten lämpökuormien vaikutuksen pystysuuntaiseen lämpötilakerrostumaan. Raskaissa rakenteissa dynaamisen mallin avulla laskettu tuloilman ilmavirta voi olla jopa 50% pienempi kuin stationaarisin malleilla laskettu ilmavirta. Dynaamista mallia voidaan soveltaa syrjäytysilmanvaihdon suunnittelussa erilaisissa sovelluksissa, joissa lämpökuormat vaihtelivat ja terminen massa aiheuttaa merkittävän vaikutuksen. Dynaamisen mallin avulla voidaan pienentää merkittävästi tarvittavan ilmanvaihtojärjestelmän mitoitusilmavirtaa, mikä voi vähentää investointikustannuksia ja puhaltimen sähkönkulutusta.

Julkaisun otsikon käännös	Syrjäytysilmanvaihdon vyöhykemalli liikerakennuksissa
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Kosonen, Risto, Vastuuprofessori
Kustantaja	Aalto University
Painoksen ISBN	978-952-64-0172-0
Sähköinen ISBN	978-952-64-0173-7
Tila	Julkaistu - 2020
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

syrjäytysilmanvaihdon suunnittelu
ilmamäärän mitoitus
lämpötilakerrostuma
vyöhykemalli
lämpötilaperusteinen ilmanvaihdon suunnittelu

YK:n kestävän kehityksen tavoitteet

Tämä tuotos edistää seuraavia kestävän kehityksen tavoitteita:

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-64-0173-7

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@phdthesis{a90cb5d19af74b9489b3bdda16d65a1c,

title = "A nodal model for displacement ventilation in commercial buildings",

abstract = "The design of displacement ventilation (DV) is usually based on controlling the desired air temperature in the occupant zone. A heat balance-based method is applied in displacement ventilation design when overheating is the primary indoor climate concern. The vertical temperature gradient in DV systems is usually calculated with lumped-parameter nodal models. An accurate vertical temperature gradient calculation is essential for displacement ventilation system design since it directly relates to the calculation of supply airflow rate. This study is focused on temperature gradient modelling and design of supply airflow rate in rooms with DV. The research methods include physical measurements and modelling methods. The measurements in steady-state conditions with typical buoyant flow elements, heat gain combinations and room heights showed that the major part of the vertical temperature gradient occurs at a low level of a room. The study also reveals that commonly used linear DV design models are not able to estimate vertical air temperature gradient accurately. As a result, the calculated air temperature in the occupied zone can defer from the real one by 2–3 °C, which causes poor thermal comfort and inadequate sizing of the ventilation and cooling systems. The developed steady-state model takes into account the types and locations of the heat gains and can accurately predict the temperature gradient in a room with DV.However, in practical applications, steady-state conditions do not exist, and heat gains vary significantly during operation hours. In addition, the thermal mass of building structures affects the room air temperature. This study presents a new dynamic displacement ventilation calculation model, the results of which are compared with the traditional method in a few typical applications. The study presents the calibration method of the dynamic model parameters of the building structures with the use of building simulation software IDA-ICE. The dynamic model was compared with the measurement results in a lecture room with DV. The dynamic multi-nodal model of displacement ventilation design is able to take into account the effect of building thermal mass and varying internal heat gains on the vertical temperature gradient. The airflow rate calculated by the dynamic model could be up to 50% lower than the airflow rate calculated with the steady-state models for heavyweight constructions.The dynamic DV model can be applied in DV design with various applications where heat gains varied, and thermal mass plays a significant role. The dynamic model can significantly decrease the design airflow rate of DV, which can result in a reduction of investment costs and electrical consumption of fans.",

keywords = "design of displacement ventilation, calculation of airflow rate, temperature gradient, nodal model, temperature-based ventilation design, syrj{\"a}ytysilmanvaihdon suunnittelu, ilmam{\"a}{\"a}r{\"a}n mitoitus, l{\"a}mp{\"o}tilakerrostuma, vy{\"o}hykemalli, l{\"a}mp{\"o}tilaperusteinen ilmanvaihdon suunnittelu, design of displacement ventilation, calculation of airflow rate, temperature gradient, nodal model, temperature-based ventilation design",

author = "Natalia Lastovets",

year = "2020",

language = "English",

isbn = "978-952-64-0172-0",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "204",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - A nodal model for displacement ventilation in commercial buildings

AU - Lastovets, Natalia

PY - 2020

Y1 - 2020

N2 - The design of displacement ventilation (DV) is usually based on controlling the desired air temperature in the occupant zone. A heat balance-based method is applied in displacement ventilation design when overheating is the primary indoor climate concern. The vertical temperature gradient in DV systems is usually calculated with lumped-parameter nodal models. An accurate vertical temperature gradient calculation is essential for displacement ventilation system design since it directly relates to the calculation of supply airflow rate. This study is focused on temperature gradient modelling and design of supply airflow rate in rooms with DV. The research methods include physical measurements and modelling methods. The measurements in steady-state conditions with typical buoyant flow elements, heat gain combinations and room heights showed that the major part of the vertical temperature gradient occurs at a low level of a room. The study also reveals that commonly used linear DV design models are not able to estimate vertical air temperature gradient accurately. As a result, the calculated air temperature in the occupied zone can defer from the real one by 2–3 °C, which causes poor thermal comfort and inadequate sizing of the ventilation and cooling systems. The developed steady-state model takes into account the types and locations of the heat gains and can accurately predict the temperature gradient in a room with DV.However, in practical applications, steady-state conditions do not exist, and heat gains vary significantly during operation hours. In addition, the thermal mass of building structures affects the room air temperature. This study presents a new dynamic displacement ventilation calculation model, the results of which are compared with the traditional method in a few typical applications. The study presents the calibration method of the dynamic model parameters of the building structures with the use of building simulation software IDA-ICE. The dynamic model was compared with the measurement results in a lecture room with DV. The dynamic multi-nodal model of displacement ventilation design is able to take into account the effect of building thermal mass and varying internal heat gains on the vertical temperature gradient. The airflow rate calculated by the dynamic model could be up to 50% lower than the airflow rate calculated with the steady-state models for heavyweight constructions.The dynamic DV model can be applied in DV design with various applications where heat gains varied, and thermal mass plays a significant role. The dynamic model can significantly decrease the design airflow rate of DV, which can result in a reduction of investment costs and electrical consumption of fans.

AB - The design of displacement ventilation (DV) is usually based on controlling the desired air temperature in the occupant zone. A heat balance-based method is applied in displacement ventilation design when overheating is the primary indoor climate concern. The vertical temperature gradient in DV systems is usually calculated with lumped-parameter nodal models. An accurate vertical temperature gradient calculation is essential for displacement ventilation system design since it directly relates to the calculation of supply airflow rate. This study is focused on temperature gradient modelling and design of supply airflow rate in rooms with DV. The research methods include physical measurements and modelling methods. The measurements in steady-state conditions with typical buoyant flow elements, heat gain combinations and room heights showed that the major part of the vertical temperature gradient occurs at a low level of a room. The study also reveals that commonly used linear DV design models are not able to estimate vertical air temperature gradient accurately. As a result, the calculated air temperature in the occupied zone can defer from the real one by 2–3 °C, which causes poor thermal comfort and inadequate sizing of the ventilation and cooling systems. The developed steady-state model takes into account the types and locations of the heat gains and can accurately predict the temperature gradient in a room with DV.However, in practical applications, steady-state conditions do not exist, and heat gains vary significantly during operation hours. In addition, the thermal mass of building structures affects the room air temperature. This study presents a new dynamic displacement ventilation calculation model, the results of which are compared with the traditional method in a few typical applications. The study presents the calibration method of the dynamic model parameters of the building structures with the use of building simulation software IDA-ICE. The dynamic model was compared with the measurement results in a lecture room with DV. The dynamic multi-nodal model of displacement ventilation design is able to take into account the effect of building thermal mass and varying internal heat gains on the vertical temperature gradient. The airflow rate calculated by the dynamic model could be up to 50% lower than the airflow rate calculated with the steady-state models for heavyweight constructions.The dynamic DV model can be applied in DV design with various applications where heat gains varied, and thermal mass plays a significant role. The dynamic model can significantly decrease the design airflow rate of DV, which can result in a reduction of investment costs and electrical consumption of fans.

KW - design of displacement ventilation

KW - calculation of airflow rate

KW - temperature gradient

KW - nodal model

KW - temperature-based ventilation design

KW - syrjäytysilmanvaihdon suunnittelu

KW - ilmamäärän mitoitus

KW - lämpötilakerrostuma

KW - vyöhykemalli

KW - lämpötilaperusteinen ilmanvaihdon suunnittelu

KW - design of displacement ventilation

KW - calculation of airflow rate

KW - temperature gradient

KW - nodal model

KW - temperature-based ventilation design

M3 - Doctoral Thesis

SN - 978-952-64-0172-0

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

A nodal model for displacement ventilation in commercial buildings

Abstrakti

Tutkimusalat

YK:n kestävän kehityksen tavoitteet

Pääsy asiakirjaan

Sormenjälki

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