Abstract
With the growth of energy-efficient building sector, ventilation systems are becoming increasingly important not only of fresh air supply but also in terms of energy consumption. The aim of this paper is to describe and analyse the operation of an air handling unit (AHU) with a heat pump using energy and exergy analyses under the variable environmental temperature (from –30 °C to 10 °C). The application of selected methods is illustrated in a case study of an AHU using environmental temperatures of Vilnius city during heating season (from the beginning of October to the end of April). An analytical method for determining distribution of the environmental (outdoor air) temperature is used. Energy and exergy analyses showed periods when the highest amounts of energy and exergy were consumed and the greatest exergy losses occurred. This allowed to reveal the component of the system with the highest exergy losses – the heat pump evaporator. Therefore, further research is needed for its design and application. At the end of the article, the seasonal indicators of the AHU with heat pump operation were calculated: coefficient of performance and exergy efficiency. The presented research procedure could be applied to the analysis of other energy systems and processes in them.
Highlights
Energinėms sistemoms taikoma ekserginė analizė apima pirmąjį ir antrąjį termodinamikos dėsnius apibrėžtomis aplinkos sąlygomis
At the end of the article, the seasonal indicators of the AHU with heat pump operation were calculated: coefficient of performance and exergy efficiency
Summary
Tyrimo objektas – OPĮ su integruotu šilumos siurbliu (ŠS). Pagrindiniai analizės komponentai yra šilumogrąžis (ŠG), du ventiliatoriai (tiekiamasis ir ištraukiamasis), šilumos siurblio garintuvas (GR), kompresorius (KM), kondensatorius (KN) ir droselinis vožtuvas (DV) (1 pav.). Toliau oras transportuojamas į patalpą (žymėjimas Ri), tam naudojamas tiekiamojo oro ventiliatorius (Vt). Čia EOPĮ – OPĮ komponentams tiekiamas eksergijos srautas, kW, t. Šiame tyrime tiekiamojo oro masės srautas yra pastovus ( M oro ), į patalpą tiekiamojo oro temperatūra – TR, o aplinkos (lauko) oro temperatūra – Te. Naudojantis šiais parametrais galima apskaičiuoti reikalingą šilumos srautą, norint pašildyti lauko orą iki reikalingos patalpos temperatūros: QOPĮ Moro cp,oro TR Te ,. ŠG šilumos srauto atveju vertinamos ištraukiamojo oro iš patalpos temperatūros prieš (T3) ir už (T4) ŠG (1 pav.):. Pateiktus), vėliau iš jų nustatomi atitinkami eksergijos nuostoliai ir apskaičiuojamas viso įrenginio ekserginis efektyvumas. Tuomet OPĮ sistemoje suvartotas savitasis eksergijos kiekis apskaičiuojamas pagal formulę:. Norint nusakyti viso įrenginio ekserginį naudingumo koeficientą KOPĮ , įvertinami visi eksergijos nuostoliai lOPĮ bei suvartota eksergija e+, vykstant oro paruošimo procesui. Skaičiuojant sezoninius rodiklius, vertinami tik šildymo sezono mėnesiai: nuo spalio pradžios iki balandžio pabaigos, nagrinėjama vietovė – Vilniaus miestas
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