Preliminary communication
Optimal Sizinig of Borehole Heat Exchangers
Miroslav RUŠEVLJAN
; Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Zagreb, Croatia
Vladimir SOLDO
; Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Zagreb, Croatia
Tonko ĆURKO
; Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Zagreb, Croatia
Abstract
The heat pumps coupled to the borehole heat exchangers (BHE) can serve for heating and/or cooling of buildings. Optimal sizing of BHE is important because of high drilling costs and importance of matching borehole thermal capacity with the capacity of the heat pump.
Proper design of such systems is usualy based on complex mathematical simulations that have to be performend not only for peak building loads, but also for building loads that are calculated throughout the whole year. For this reason the building loads have to be analysed in more detail than for sizing of a conventional system. Designers of heat pump systems coupled to the BHE should also take into acount the long-term temperature changes in the ground surrounding the BHE, which would influence the overall efficiency of the system during its life cycle. The required BHE length is substantially influenced by the thermal conductivity of the ground, which can be only roughly estimated from local geological data. Experimental thermal response tests provide a good estimate of the ground thermal conductivity and borehole thermal resistance. The high cost of the thermal response test reduces its application to commercial and institutional premises with the large number of BHE.
In this work, the overview of calculation methods for the heat pumps coupled to the BHE is presented, with suggestions for optimal sizing of BHE.
Keywords
Borehole heat exchanger; Ground thermal conductivity; Heat pump; Long-term temperature changes; Optimal sizing
Hrčak ID:
50568
URI
Publication date:
30.10.2009.
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