The Outlet Temperature Prediction of In-Situ Thermal Response Test using CFD Analysis

Title & Authors
The Outlet Temperature Prediction of In-Situ Thermal Response Test using CFD Analysis
Sim, Yong-Sub; Lee, Hee-Sang;

Abstract
The in-situ thermal response test for the design of a ground heat exchanger of geothermal heat pumps have difficulty in predicting the outlet temperature according to the variation of conditions due to the expense and time. This paper suggests a 3-D CFD analysis method to predict the heat transfer performance of vertical type ground heat exchanger, which is mostly used in national, and the outlet temperature and the slope of two in-situ thermal response tests were compared to test the proposed CFD reliability. The results of CFD analysis showed that the outlet temperature was predicted to within $\small{0.5^{\circ}C}$ of the actual value and the slope was predicted to within 1.6%. The reliability of the CFD analysis method was confirmed using this process, and the outlet temperature prediction of the two in-situ thermal response tests was obtained by changing $\small{{\pm}20%}$ of the flow rate and the effective thermal conductivity conditions, respectively. The results of CFD analysis showed that the outlet temperature of Case 1 was 28.0 (-20%) and $\small{29.6^{\circ}C}$ (+20%) for the flow rate variation and $\small{29.6^{\circ}C}$ (-20%) and $\small{28.0^{\circ}C}$ (+20%) for the effective thermal conductivity variation, and the outlet temperature of Case 2 was 28.4 (-20%) and $\small{29.8^{\circ}C}$ (+20%) for the flow rate variation and $\small{29.7^{\circ}C}$(-20%) and $\small{28.4^{\circ}C}$(+20%) for the effective thermal conductivity variation.
Keywords
CFD(Computational Fluid Dynamics);Geothermal Heat Pump;Ground Heat Exchanger;In-Situ Thermal Response Test;Outlet Temperature;
Language
Korean
Cited by
References
1.
S. K. Yim, "The Practical Study of Geothermal Heat Pump System", 2002-N-GE11-P-030, 2005.

2.
Y. B. lee, S. I. Cho, C. H. Kang, I. K. Jung, C. G. Lee, J. H. Sung, S. O. Chung, Y. B. Kim, "Analysis of Heat Transfer Characteristics in Soil for Development of a Geothermal Heat Exchanger System", Korean Society for Agricultural Machinery, Vol. 30, No. 3, pp. 185-191, 2005.

3.
S. S. Kim, "A Study on the Heat Pump System by using Geothermal Energy", Gyeongsang National University, Doctoral dissertation, 2010.

4.
S. W. Woo, J. H. Kim, S. H. Shin, K. I. Hwang, "The Comparison of the EWT&LWT between Field Measurement and CFD of Vertical-type Geothermal Heat Exchanger", Korea Society of Geothermal Energy Engineers, Vol. 3, No. 1, pp. 11-16, 2007.

5.
S. K. Lee, J. S. Woo, D. K. Kim, "A Study of Determining Initial Ignoring Time of Line Source Model used in Estimation the Effective Soil Formation Thermal Conductivities", Journal of Energy Engineering, Vol. 17, No. 3, pp. 167-174, 2008.

6.
K. Torikoshi, G. N. Xi, "Numerical study of flow and thermal fields in finned tube heat exchangers", Proceedings of the IMECE, HTD-317-1, pp. 453-458. 1995.