Kiirguskadude mõju analüüs hoone soojusbilansile
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Kuupäev
2021
Kättesaadav alates
10.09.2021
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Vastavalt standarditele ja eeskirjadele võetakse soojuskadude määramisel läbi hoone
välispiirete üldjuhul arvesse ainult juhtivuslikku ja konvektiivset soojuslevi, kuid
kiirguslikku soojusülekannet ei arvestata. Sellest lähtuvalt oli töö eesmärgiks hinnata
kiirguskadude mõju hoone arvutuslikele soojuskadudele.
Selle eesmärgi nimel selgitati käesolevas töös taeva temperatuuri määramist nii pilvise kui
ka selge taeva korral, kirjeldati seosed mille abil saab leida kiirgusliku soojusvoo suuruse
erinevates olukordades, selgitati tasakaaluolukorra tingimusi mil vaadeldavasse süsteemi
sisenevad ja lahkuvad soojusvood on võrdsed, tutvustati tasakaaluolukorra korral hoone
välispinna temperatuuri leidmist neljanda astme võrrandi lahendamise teel ning esitleti
kirjeldatud meetodite abil saadud näidistulemusi.
Jõuti järeldusele, et kiirguskadudega arvestamine suurendab hoone soojuskadusid
piisavalt hea soojusisolatsiooni ja standardis ettenähtud välispinna soojustakistuse korral
vaid paari protsendi võrra, sest kiirguskao mõjul piirde pinnatemperatuuri langemisel alla
välisõhu temperatuuri hakkab piirde ja välisõhu vaheline konvektiivne soojusvoog väga
efektiivselt kompenseerima kiirguse mõjul tekkivat soojuskadu.
According to standards and regulations, only conductive and convective heat transfer are generally taken into account when determining heat losses through the boundaries of a building. But heat is also dissipated by radiation. Based on this, the aim of the thesis was to assess the impact of radiation losses on the calculated heat losses of the building. To this end, the calculation of sky temperature for both cloudy and clear sky was explained, formulas for calculating the radiant heat flux in differing situations were developed, the conditions of the equilibrium situation under which the heat flows entering and leaving the system were clarified, finding the temperature of the external surface of the building during the state of equilibrium in the form of solving the quartic equation was described, and sample results calculated using the aforementioned methods and equations were presented. It was concluded that taking into account the radiant heat flux increased the heat loss of a building only by a few percent, and this is explained by the fact that convection heat flux coming from the ambient air will effectively balance out the heat losses caused by radiative flux.
According to standards and regulations, only conductive and convective heat transfer are generally taken into account when determining heat losses through the boundaries of a building. But heat is also dissipated by radiation. Based on this, the aim of the thesis was to assess the impact of radiation losses on the calculated heat losses of the building. To this end, the calculation of sky temperature for both cloudy and clear sky was explained, formulas for calculating the radiant heat flux in differing situations were developed, the conditions of the equilibrium situation under which the heat flows entering and leaving the system were clarified, finding the temperature of the external surface of the building during the state of equilibrium in the form of solving the quartic equation was described, and sample results calculated using the aforementioned methods and equations were presented. It was concluded that taking into account the radiant heat flux increased the heat loss of a building only by a few percent, and this is explained by the fact that convection heat flux coming from the ambient air will effectively balance out the heat losses caused by radiative flux.
Kirjeldus
Magistritöö
Energiakasutuse õppekaval
Märksõnad
magistritööd, Stefan-Boltzmanni seadus, taeva temperatuur, kiirguslik soojuskadu, Wieni nihkeseadus