A novel TRNSYS type of a coaxial borehole heat exchanger for both short and mid term simulations: B2G model

Sequential coupled numerical simulations of an air/ground-source heat pump: Validation of the model and results of yearly simulations

“…Therefore, it is not possible to operate with the hypothesis of perfect distribution of the total water mass flow rate among the different probes. This specific problem has been addressed in [38] and to account for the different distributed and concentrated pressure losses, different multiplication factors are used to calculate the fraction of water mass flow rate that flows in a specific probe. The fractions of each probe are reported in Table 2.…”

Appendix: Sample Design and Optimization Projects

“…Coaxial heat exchangers, see Figure A.6, promise to outperform their U-bend counterparts. For this reason, the study of coaxial heat exchangers has received serious attention (Holmberg et al, 2016;Gordon et al, 2018, Dai et al, 2019Iry and Rafee, 2019;Liu et al, 2019;Luo et al, 2019;Pan et al, 2019;Zhang et al, 2019;Cazorla-Marín et al, 2020, Hu et al, 2020. Potential reasons behind the better performance include: (i) a larger heat transfer surface area for a given borehole size, (ii) the fluid in the inner pipe is significantly more insulated from the ground and, thus, exchanges minimum heat with the ground, (iii) possibly less pressure (head) loss because of the larger (compared to its conventional U-bend counterpart) and potentially shorter (to deliver the same amount of heat from or to the ground) conduit.…”

A New Type in TRNSYS 18 for Simulation of Borehole Heat Exchangers Affected by Different Groundwater Flow Velocities

“…De Rosa et al [17,18] developed a new TRNSYS type implementing a borehole-to-ground model to reproduce the short-term dynamic performance of a BHE and validated the approach by comparing the results with the experimental data (for a step-test and under normal operating conditions) of a real GSHP system. Cazorla-Marìn et al [19] adopted a similar approach to reproduce the dynamic behavior of a coaxial BHE and validated the results by comparing them with the experimental data derived from a dual source heat pump (DSHP) system. All of these studies related to TRNSYS software and most of the available energy tools such as EWS [20], EED [21], GLHEPRO [22] Pilesim [23], and Modelica [24] have assumed a pure heat conduction in the ground and have not considered the effects of groundwater flow on the performance of the GSHP system; otherwise, as Angelotti et al demonstrated, this assumption is very limiting because the role of the groundwater flow is essential and can improve the energy performance of a BHE up to 105% for a high flow velocity case [25].…”