Development of the Performance Prediction Equation for a Modular Ground Heat Exchanger

Abstract

Although ground source heat pump (GSHP) systems are more efficient than conventional air source heat pump (ASHP) systems, their high initial investment cost makes it difficult to introduce them into small buildings. Therefore, the development of a method for reducing the installation costs of GSHPs for small buildings is essential. This study proposes a modular ground heat exchanger (GHX) for cost reduction and an improved workability of GSHPs. In addition, a numerical model was constructed for the analysis of the performance of the modular GHX. However, to easily introduce the new GHX at the building design stage, the development of a performance prediction method for the introduction of modular GHXs to small buildings is necessary. Therefore, the entering water temperature (EWT) equation was derived from the calculation methods in the heat transfer process, and the ground temperature model was developed in consideration of the operation condition. The numerical results showed that the average values of EWT and ground temperature were 8.11 °C and 8.00 °C, respectively under an average ambient temperature of 0.42 °C. In addition, the performance prediction model was compared with the numerical results. The results showed that the coefficient of variation of the root mean square error (RMSE) of the ground temperature and EWT model were 5.20% and 1.33%, respectively.

Keywords

• numerical analysis
• ground source heat pump
• heat exchange rate
• ground heat exchanger
• modular heat exchanger