The quantitative evaluation of design parameter's effects on a ground source heat pump system

• The quantitative effects of the design parameters of GSHP systems was investigated.
• The GLHX size and the GSHP system performance should be considered together for optimum design of the system.
• The reduction of the length for GLHX is very important to save initial cost of a GSHP system.

The main solution for the reduction of energy consumption in the field of HVAC is the development of new and renewable energy technologies. Among the various renewable energy systems, ground source heat pump (GSHP) systems have been spotlighted as efficient building energy systems because of their great potentials for energy reduction in building air conditioning and reducing CO2 emissions. However, higher initial cost works as a barrier to the promotion of their use. Therefore, it is critical to reduce the initial costs by optimizing the design of the system. In this paper, parameters that affect the performance of the GSHP system and the size of ground loop heat exchanger (GLHX) have been investigated. Ratio of GLHX length to unit capacity (L/Q) decreased according to increasing value of thermal conductivity, but L/Q increased according to increasing value of borehole heat transfer resistance. In cooling mode, L/Q decreased according to increasing EWT of underground circulating water and borehole distance but increased in heating mode. The value of L/Q tended to increase according to increasing underground initial temperature in cooling mode, but decreased in heating mode. L/Q decreased according to increasing U-tube separation distance and decreasing underground circulating water flow rate, because the thermal interference effect of underground circulating water and heat absorption and emission rate from the ground decreased. The reduction of the size of GLHX is very important in the aspect of saving total installation cost of a GSHP system. Therefore, the size of GLHX and the performance of GSHP system should be considered together for optimum design of the GSHP system.