Utjecaj kompaktnosti bušotinske mreže i termalnih interferencija na dimenzioniranje bušotinskog izmjenjivača topline

master's thesis

• Title: Utjecaj kompaktnosti bušotinske mreže i termalnih interferencija na dimenzioniranje bušotinskog izmjenjivača topline : diplomski rad
• Title (english): Effect of borehole array compactness and thermal interferences on borehole heat exchanger sizing : master's thesis
• Author: Vedrana Krapec
• Mentor: Tomislav Kurevija (mentor)
• Committee member: Tomislav Kurevija
• Committee member: Miroslav Golub
• Committee member: Damir Rajković
• Granter: University of Zagreb; Faculty of Mining, Geology and Petroleum Engineering; (Department of Petroleum and Gas Engineering and energy); Zagreb
• Defense date and country: 2014-09-19, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mining, Petroleum and Geology Engineering; Petroleum Mining

Abstract

Pravilno dimenzioniranje sustava bušotinskog izmjenjivača s dizalicom topline na površini mora minimizirati negativne utjecaje višegodišnjih promjena temperature tla i radnog medija, kao i pojave termalnih interferencija susjednih bušotina u bušotinskom polju. Navedene promjene javljaju se uslijed neravnoteže u godišnjim energetskim bilancama između pridobivene toplinske energije iz tla tijekom ciklusa grijanja zimi i pohranjene energije u tlo pri ciklusu hlađenja ljeti. Pojednostavljeni proračuni i korištenje metode analogije za određivanje ukupno potrebne duljine bušotina za izmjenu toplinske energije s tlom generiraju relativno visoku pogrešku prilikom dimenzioniranja kompleksnih sustava s kompaktnim bušotinskim mrežama. Za projekcije višegodišnjih temperaturnih promjena tla i bušotinskog radnog medija dostupni su programski paketi koji koriste takozvanu g-funkciju – matematičku funkciju koja ovisi o geometriji bušotinske mreže, a koristi funkciju jediničnog skoka za određivanje temperaturnog odaziva bušotina superpozicijom 24h temperaturnog odaziva pri vršnom toplinskom opterećenju na višegodišnje bazno opterećenje sustava. Dimenzionirajući sustav dizalice topline na površini i bušotinskog izmjenjivača pri razliĉitim geometrijskim rasporedima bušotina s obzirom na višegodišnji radni vijek, u radu je analiziran utjecaj razmaka pojedinih bušotina u bušotinskom polju te utjecaj termalnih interferencija na ukupno potrebnu duljinu za prijelaz toplinske energije između površine i tla. U analizi su upotrijebljena dva danas najčešće korištena matematička modela; analitička metoda ASHRAE/Kavanaugh, u kojoj se koristi rješenje cilindričnog prijelaza topline, i numeričko-analitička metoda Lund/Eskilson, koja koristi rješenje linijskog prijelaza topline.

Abstract (english)

Abstract: Properly sized borehole heat exchanger in geothermal heat pump system (widely known also as ground source heat pump system) need to minimize long-term ground and working fluid temperature changes. These changes occur due to imbalances of heat extracted from the ground during winter and heat rejected into the ground during summer months, as well as thermal interferences of adjacent boreholes in borehole array. Simple calculations and spreadsheet-based analogical solutions of required borehole length for heat transfer run into difficulties when dealing with such large, complex ground source heat pump heating and cooling systems, which use compact borehole array. A number of computer programs are available to calculate how ground loop fluid temperature varies in such complex systems during multi year operation, using so-called ‘g-function’ – a mathematical function dependent on the geometry and shape of the borehole array. ‘g-function’ involves a type of ‘step-function’, where 24 h ‘step’ of peak loading is superimposed on a top of a long-term base load. This work will show, by sizing realistic complex geothermal heat pump system with multiple boreholes in various geometric arrays for long-term operation, how spacing of adjacent boreholes and thermal interferences influence required borehole length for heat transfer. Two mathematical models will be used in system analysis, analytical method, developed by ASHRAE/Kavanaugh, in which cylinder source heat transfer solution is used, and numerical-analytical method, by Lund/Eskilson, which uses line source heat transfer solution.

• Keywords: geotermalne dizalice topline; dimenzioniranje bušotinskog izmjenjivača topline; termalne interferencije; termogeologija
• Keywords (english): geothermal heat pumps; borehole array sizing; thermal interferences; thermogeology
• Language: croatian
• URN:NBN: urn:nbn:hr:169:327134
• Study programme: Title: Petroleum Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka naftnog rudarstva (magistar/magistra inženjer/inženjerka naftnog rudarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2016-01-13 08:56:06