Search

Grout plays an important role in the heat-transfer performance of borehole heat exchangers. The current study developed a numerical model to investigate the effect of grout thermal conductivity and heat capacity on the heat-transfer performance of borehole heat exchangers. The “relative thermal conductivity” was defined to obtain the best matching relationship of thermal conductivity between grout and soil. The numerical model was validated through sandbox experiments. The results showed that, when the grout thermal conductivity and heat capacity were both varied by 47.00%, the effect of the grout thermal conductivity on the pipe wall temperature was 26.44% stronger than that of the grout heat capacity; whereas the effect of the grout heat capacity on the heat-transfer radius was 5.21% stronger than that of the thermal conductivity. As the same variation of the grout thermal conductivity, when the soil thermal conductivity change from 1.30 to 1.90 W/(m·K) (1.60 kcal/[m2 · h · °C]), the effect of the changing grout thermal conductivity on the heat-transfer performance decreased by 8.04%. The results also showed that the optimal relative thermal conductivity was 1.20-1.30. These results can serve as guidelines for selecting appropriate grouts for different geological conditions. [ABSTRACT FROM AUTHOR]

Thermal performance of closedwet cooling tower (CWCT) with packing is analyzed using experiments and numerical simulations. The effect of cooling water flowdirection on the performance is discussed. The results showthat the packing plays an important role in improving the cooling effect of the CWCT. Under the same operating conditions, the cooling water outlet temperature of CWCT with packing is lower than that of CWCT without packing between 0.6°C and 1.5°C the cooling efficiency of CWCT with packing is higher than that of CWCT without packing between 6.0% and 14.8%. The concurrent cooling water flow direction results in more uniform temperature differences between cooling water and the spray water,which can benefit the cooling water outlet temperature 0.3-0.7°C and the cooling efficiency 3.0-9.5%. [ABSTRACT FROM AUTHOR]