Heat transfer in Oxisol in heat storage process¹

Transferência de calor em latossolo vermelho (Oxisol) em processo de armazenamento de calor

HIGHLIGHTS:

Soil temperature increased logarithmically as a function of heat transfer time.

The type of material of the linear heat exchanger (PVC and copper) had no influence on soil temperature variation.

The installation distance between geothermal heat exchangers must be greater than 50 cm.

ABSTRACT

Geothermal energy is a renewable source that can assist in the thermal conditioning of constructed environments. The objective of this study was to analyze the heat transfer in a Red Latosol (Oxisol), in heat storage process, using two linear heat exchangers. The treatments were arranged in a 3 × 2 × 3 factorial scheme, corresponding to three temperature differentials between soil and water (5, 10 and 15 °C), two types of materials (PVC and copper) and three radial distances (10, 20 and 25 cm), with three replicates. Soil temperature variations were obtained continuously for a period of 12 hours using DS18B20 sensors. These variations were logarithmic as a function of heat transfer time and radial distance and linear as a function of the temperature differential between soil and water (θ). The temperature differential between soil and water was the main factor that influenced soil temperature variation, and the material employed was insignificant in this variation. The minimum distance between heat exchangers should be greater than 50 cm, and PVC pipes proved to be more attractive for use involving thermal exchange with the ground as they are more viable than copper and easier to implement.

Key words:
soil thermal behavior; horizontal linear heat exchanger; surface geothermal energy