Laboratory investigations and numerical analysis of thermal performance of the single U-tube VBHE in multiple-layer substrates

Abstract

In order to study the thermal performance of a single U-tube VBHE in multiple-layer substrates, the similarity principle was used to build an indoor comprehensive miniature bench of single U-tube VBHE innovatively, and effects of inlet water temperature and hydrogeological geology on the thermal performance of VBHE were analyzed. In addition, numerical simulation was used to assist in the research. The results indicate that to build a laboratory-scale GSHP system model test apparatus based on the similarity principle will achieve long-term test of GSHP system with smaller human and material resources and a shorter experimental cycle. It's more efficient and convenient. The simplified use of uniform soil thermal and physical properties can cause great deviation. Heat flux per unit pipe of the VBHE increases linearly with the temperature difference's increasing between the inlet water and initial soil. The water temperature along the tube under thermal conductivity increasing and decreasing conditions does not decrease as linearly as the temperature's decreasing under the uniform thermal conductivity condition.