Control of Heat Transfer in a Vertical Ground Heat Exchanger for a Geothermal Heat Pump System

Khaled Salhein, C. J. Kobus and Mohamed Zohdy
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Khaled Salhein: Department of Electrical and Computer Engineering, School of Engineering and Computer Science, Oakland University, Rochester, MI 48306, USA
C. J. Kobus: Department of Electrical and Computer Engineering, School of Engineering and Computer Science, Oakland University, Rochester, MI 48306, USA
Mohamed Zohdy: Department of Electrical and Computer Engineering, School of Engineering and Computer Science, Oakland University, Rochester, MI 48306, USA

Energies, 2022, vol. 15, issue 14, 1-24

Abstract: This paper presents a mathematical model of heat transfer behavior between the liquid inside vertical underground geothermal pipes and the surrounding ground for heating (in the winter) and cooling (in the summer) modes in a ground heat exchanger (GHE) that can optimize its output temperature. The GHE’s output temperature reaches the appropriate value when the water velocity is lowered enough. Subsequently, the proposed model was applied to a case study of a 400-ton geothermal heat pump system (GHPS) at Oakland University, in both the heating and cooling modes, to assess its validity and improve the GHE’s performance. The model was implemented in MATLAB using an ordinary differential equation (ODE) solver. Four different water velocities were used to demonstrate the significant effect of velocity on the loop exit temperature. Model predictive control (MPC) was designed to optimize the GHE’s output temperature by controlling the water velocity, which could reduce the energy consumption used for heat and water circulating pumps. The results reveal that the acceptable range of the water velocity for Oakland University’s GHE was between 0.35 and 0.45 m / s , which ensured that the heat pump system delivered the proper temperature to provide the Human Health Building (HHB) with a comfortable temperature regardless of the season. The suggested water velocity ranges in vertical single U-tube pipes with diameters of De 25 mm , De 32 mm , and De 40 mm are between 0.33 and 0.43 m / s , 0.35 to 0.45 m / s , and 0.38 to 0.48 m / s , respectively.

Keywords: geothermal heat pump system (GHPS); ground heat exchanger (GHE); model predictive control (MPC) (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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